JP2022094151A - Switching element drive circuit - Google Patents

Abstract

To obtain a switching element driving circuit in which a detection function is simplified and a control processing load is reduced.SOLUTION: A control unit 30U controls a current value of a gate signal to be inputted to a gate of a switching element 44U on the basis of either one of a surge peak of a voltage between input and output terminals and a surge peak of an element current, which are respectively derived based on a result of comparing the voltage between input and output terminals of the switching element 44U detected by a voltage between input and output terminals detection unit 24U with a threshold, and a result of comparing a voltage corresponding to the element current of the switching element 44U detected by an element current detection unit 26U with the threshold, in a detection processing unit 28U.SELECTED DRAWING: Figure 2

Description

The present invention relates to a switching element drive circuit that drives the gate of the switching element.

By controlling the current value of the gate signal that drives the gate of switching elements such as IGBTs (Insulated Gate Bipolar Transistors) and MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), switching surges (surges) that occur immediately after switching of switching elements An active gate control (hereinafter abbreviated as "AGC") has been devised to keep the voltage (voltage or surge current) within an appropriate range.

However, if the switching characteristics change due to sudden changes in load, abnormal operation, or changes over time in parts, the peak of switching surge (hereinafter referred to as "surge peak") may exceed the withstand voltage of the switching element. was there.

In Non-Patent Document 1 below, the surge peak is peak-held and detected in the first switching cycle, and the error is corrected in the second and subsequent switching cycles so that the desired surge voltage is obtained, thereby making the switching surge constant. A controllable gate drive circuit has been proposed.

2019 IEEJ Industrial Application Division Conference 1.2 kV 30 kV / μs SiC MOSFET gate driver with built-in surge voltage control function

However, the invention according to Non-Patent Document 1 has a problem that a peak holding function and an A / D conversion function are required for surge peak detection, and the cost increases. Further, the invention according to Non-Patent Document 1 has a problem that the processing load of the control unit increases because the processing of the detected waveform is performed every switching cycle.

The present invention has been created in view of the above problems, and an object of the present invention is to obtain a switching element drive circuit that realizes simplification of a detection function and reduction of a control processing load.

In order to achieve the above object, the switching element drive circuit according to the present invention includes a control terminal and an input / output terminal, and a switching element in which the input / output terminals are switched according to an electric signal input to the control terminal is provided. The input / output terminal voltage detection unit that detects the input / output terminal voltage when switching in different switching cycles, the current detection unit that detects the element current of the switching element switched in the different switching cycles, and the input. A voltage comparison result that is the result of comparing the voltage between the output terminals and the threshold voltage that can be switched according to the switching cycle, and a current comparison that is the result of comparing the element current and the threshold current that can be switched according to the switching cycle. When the signal processing unit that outputs the result and the voltage comparison result in the first switching cycle and the voltage comparison result in the second switching cycle different from the first switching cycle are different, in the first switching cycle. The intermediate value between the threshold voltage and the threshold voltage in the second switching cycle is set as the surge peak of the voltage between the input / output terminals, and the current comparison result in the first switching cycle and the current comparison result in the second switching cycle. When is different, the intermediate value between the threshold current in the first switching cycle and the threshold current in the second switching cycle is defined as the surge peak of the element current, and the surge peak of the voltage between the input / output terminals is defined as the voltage. The current value of the electric signal is reduced when it is larger than the value or when the surge peak of the element current is larger than the specified current value, and the surge peak of the voltage between the input / output terminals is the specified voltage. It includes a control unit that controls to increase the current value of the electric signal when the surge peak of the element current is smaller than the value and the surge peak of the element current is smaller than the current specified value.

With this configuration, a plurality of time information related to the calculation of the voltage surge peak and the current surge peak can be detected at the time of switching at different timings, and the change of the control terminal voltage etc. using the threshold value can be detected. It is possible to reduce the processing load of the control of the switching element drive circuit according to the above.

Further, since the surge peak is detected by a simple method of comparing the voltage and the like with the threshold value, the detection function can be simplified.

It is a block diagram which showed an example of the inverter which provided the switching element drive circuit which concerns on 1st Embodiment. It is a block diagram which showed an example of the structure of the gate driver provided in the gate of a switching element. It is a block diagram which shows an example of the specific structure of a control part. It is a block diagram which showed an example of the circuit centering on the comparison function part which the detection processing part has. (A) is an explanatory diagram of surge voltage detection, and (B) is an explanatory diagram of surge current detection. (A) is an explanatory diagram showing an example of surge waveforms detected at two different threshold values, and (B) is a case where a surge peak is calculated based on the similarity of surge waveforms detected at two different threshold values. It is an explanatory diagram of. (A) is a schematic diagram when the voltage between the input / output terminals to be measured is detected at four points, and (B) is a straight line passing through two points included in the detected four points and the detected four points. It is explanatory drawing for calculating a surge voltage from the intersection with the straight line passing through the other two included points. In (A), when the voltage between the input / output terminals of the switching element is equal to or higher than the initial value of the threshold voltage in the first switching, the threshold voltage is gradually increased from the initial value by a constant value in the switching following the first switching. It is an explanatory diagram in the case of detecting the surge voltage, and (B) follows the first switching when the voltage between the input / output terminals of the switching element is less than the initial value of the threshold voltage in the first switching. It is explanatory drawing in the case of detecting a surge voltage by gradually lowering a threshold voltage from an initial value by a constant value by switching. (A) and (B) are explanatory views in which the initial value of the threshold voltage is set as the center value of the surge upper limit of the switching element and the voltage of the DC power supply. It is explanatory drawing in the case that the initial value of the threshold voltage is set as the previously detected value. It is explanatory drawing in the case that the initial value of the threshold voltage is the surge voltage derived last time. In (A), when the comparison result is ON reaction in the first switching, the threshold voltage is increased, and when the comparison result is different from the previous value in the second and subsequent switchings, the threshold voltage is decreased and the detection is performed again. It is an explanatory diagram of the case, and (B) reduces the threshold voltage when the comparison result is OFF reaction in the first switching, and sets the threshold voltage when the comparison result is different from the previous value in the second and subsequent switchings. It is explanatory drawing in the case of increasing and performing detection again. If the comparison result between the threshold voltage, which is the initial value in the first switching, and the voltage between the input / output terminals is an ON reaction, the threshold value in the subsequent switching is set to 1 of the difference between the surge upper limit of the switching element and the initial value. It is explanatory drawing in the case of changing the threshold voltage by adding the threshold addition width which is / 2. It is explanatory drawing in the case that the initial value of the threshold voltage is set as the previously detected value. It is explanatory drawing in the case that the initial value of the threshold voltage is the surge voltage derived last time. (A) and (B) are explanatory views in the case where two kinds of different threshold voltages are switched at the timing when the gate signal is switched from OFF to ON and ON to OFF in each switching cycle. When the voltage between input / output terminals is compared between the initial value of the first threshold and the initial value of the second threshold, and the voltage between the input / output terminals is equal to or more than the initial value of the first threshold and equal to or less than the initial value of the second threshold. Further, in the subsequent switching, it is an explanatory diagram that the first threshold value is gradually increased from the initial value and the second threshold value is gradually decreased from the initial value. It is explanatory drawing of the determination of the initial value. It is explanatory drawing in the case of switching a plurality of different threshold voltages at the timing of switching from OFF to ON and ON to OFF in each switching cycle. It is explanatory drawing which showed the mode of setting of three kinds of thresholds. It is explanatory drawing which showed the other mode of setting of three kinds of thresholds. It is explanatory drawing in the case of comparing the voltage between input / output terminals of a switching element with the first threshold voltage and the second threshold voltage, respectively, when the motor phase current is substantially the same. It is explanatory drawing in the case of comparing the voltage between input / output terminals of a switching element with the first threshold voltage and the second threshold voltage, respectively, when the motor phase current is substantially the same in the same electric angle cycle. It is explanatory drawing in the case of providing the thinning section between the detection section which compares a voltage and the threshold voltage, and the control calculation section which calculates a surge voltage from a comparison result. When a thinning section is provided between the detection section that compares the voltage and the threshold voltage and the control calculation section that calculates the surge voltage from the comparison result, and between the control calculation section and the operation section that operates the gate current. It is an explanatory diagram of. It is explanatory drawing when the thinning-out section is provided after the control of a gate current. It is explanatory drawing when the thinning-out section is set according to the motor phase current.

Hereinafter, this embodiment will be described with reference to the drawings. FIG. 1 is a block diagram showing an example of an inverter 10 provided with a switching element drive circuit according to the present embodiment. The inverter 10 is a three-phase inverter that converts a DC voltage supplied from a DC power source 80, which is an in-vehicle battery, into, for example, a U-phase, V-phase, and W-phase three-phase AC voltage and outputs the DC voltage to the motor 12. ..

As shown in FIG. 1, the inverter 10 according to the present embodiment includes switching elements 42U, 42V, 42W, 44U, 44V, 44W such as MOSFETs, and supplies electric power supplied to the coil of the stator of the motor 12 to the switching elements. It is generated by switching to turn 42U, 42V, 42W, 44U, 44V, 44W on and off. For example, the switching elements 42U and 44U switch the power to be supplied to the U-phase coil, the switching elements 42V and 44V to the V-phase coil, and the switching elements 42W and 44W to the W-phase coil.

The drains of the switching elements 42U, 42V and 42W are connected to the positive electrode (+) of the DC power supply 80, and the sources of the switching elements 42U, 42V and 42W are the respective sources of the switching elements 44U, 44V and 44W. It is connected to the drain. Further, each source of the switching element 44U, 44V, 44W is connected to the negative electrode (−) of the DC power supply 80.

The node 46U to which the source of the switching element 42U and the drain of the switching element 44U are connected is connected to the U-phase coil of the motor 12. As an example, when the switching element 42U is turned on and the switching element 44U is turned off, the power of the DC power supply 80 is supplied to the U-phase coil of the motor 12 via the node 46U. At the same time, as an example, when the switching element 42W is turned off and the switching element 44W is turned on, the current flowing through the U-phase coil flows through the W-phase coil through the neutral point of the coil of the motor 12. The current flows to the negative electrode (-) of the DC power supply 80 via the node 46W to which the source of the switching element 42W and the drain of the switching element 44W are connected and the switching element 44W. When the U-phase coil and the W-phase coil are energized, a magnetic field is generated in the U-phase coil and the W-phase coil.

The node 46V to which the source of the switching element 42V and the drain of the switching element 44V are connected is connected to the V-phase coil of the motor 12. As an example, when the switching element 42V is turned on and the switching element 44V is turned off, the power of the DC power supply 80 is supplied to the V-phase coil of the motor 12 via the node 46V. At the same time, as an example, when the switching element 42U is turned off and the switching element 44U is turned on, the current flowing through the V-phase coil flows through the U-phase coil through the neutral point of the coil of the motor 12. The current flows to the negative electrode (−) of the DC power supply 80 via the node 46U and the switching element 44U. When the V-phase coil and the U-phase coil are energized, a magnetic field is generated in the V-phase coil and the U-phase coil.

Further, as an example, when the switching element 42W is turned on and the switching element 44W is turned off, the power of the DC power supply 80 is supplied to the W phase coil of the motor 12 via the node 46W. At the same time, as an example, when the switching element 42V is turned off and the switching element 44V is turned on, the current flowing through the W-phase coil flows through the V-phase coil through the neutral point of the coil of the motor 12. The current flows to the negative electrode (-) of the DC power supply 80 via the node 46V and the switching element 44V. When the W-phase coil and the V-phase coil are energized, a magnetic field is generated in the W-phase coil and the V-phase coil.

As described above, by switching the phase in which a magnetic field is generated in the coil of the motor 12 by switching the switching elements 42U, 42V, 42W, 44U, 44V, 44W (hereinafter, abbreviated as "switching elements 42U to 44W"), A so-called rotating magnetic field that rotates a rotor (rotor) composed of a permanent magnet or the like is generated in the coil of the motor 12. In the actual rotation control of the motor, a three-phase alternating current voltage is generated and applied to the coils of each phase of the motor 12 by PWM (pulse width modulation) control in which each of the switching elements 42U to 44W is turned on and off in small steps.

As described above, the n-type MOSFET is turned on by inputting a positive voltage gate signal to the gate. As shown in FIG. 1, in the present embodiment, each of the switching elements 42U to 44W has gate drivers 20U, 20V, 20W, 22U, 22V, 22W (hereinafter, "gate driver") for controlling the current value of the gate signal. 20U-22W ”) are connected to each other. Each of the gate drivers 20U to 22W adjusts the current value of the gate signal (hereinafter referred to as "gate current") by a variable resistor and inputs it to each gate of the switching elements 42U to 44W.

FIG. 2 is a block diagram showing an example of the configuration of the gate driver 22U provided at the gate of the switching element 44U. As described above, the gate drivers 20U to 22W are provided in each of the switching elements 42U to 44W, but the gate driver 22U will be described as a typical example, and the description of other gate drivers will be omitted.

As shown in FIG. 2, the gate driver 22U detects the input / output terminal voltage (drain / source voltage V _ds ), which is the voltage of the input / output terminals of the switching element 44U, in association with the time information. Each of the voltage detection unit 24U, the element current detection unit 26U that detects the element current (drain current Id) of the switching element _44U in association with the time information, and the input / output terminal voltage detection unit 24U and the element current detection unit 26U, respectively. A control that performs a control calculation of a gate signal input to the gate of the switching element 44U based on the output of the detection processing unit 28U that converts the detection signal of the above into a signal in a format that can be processed by the control unit 30U described later. It includes a unit 30U and an operation unit 32U that changes the gate drive capability. Each of the input / output terminal voltage detection unit 24U and the element current detection unit 26U detects time information using, for example, the control clock of the control unit 30U.

As an example, the element current detection unit 26U may detect a current value based on the potential difference between both ends of the shunt resistor, or based on the induced current generated by energization between the source and the ground region of the switching element 44U. The current value may be calculated.

For example, when the detection signals of the input / output terminal voltage detection unit 24U and the element current detection unit 26U are analog signals, the detection processing unit 28U is a kind of A / that converts them into digital signals that can be processed by the control unit 30U. It is a circuit including a D converter.

The operation unit 32U is a variable resistor that changes the resistance value under the control of the control unit 30U to change the current value of the gate signal input to the gate of the switching element 44U. The operation unit 32U has a variable resistor 32UO that changes the current value of the positive voltage gate signal input to the gate of the switching element 44U, and a variable resistor 32UO that changes the current value of the negative voltage gate signal input to the gate of the switching element 44U. Includes a resistor 32UF.

A gate signal is input to the operation unit 32U from a higher-level control device via an amplifier 34U and a complementary MOS 36U which is a kind of inverting circuit. The gate signal input from the upper control device is amplified by the amplifier, and then the positive and negative are inverted by the complementary MOS36U. The complementary MOS 36U may be omitted depending on the positive / negative mode of the gate signal input from the upper control device.

FIG. 3 is a block diagram showing an example of a specific configuration of the control unit 30U. The control unit 30U is a kind of computer, and includes a CPU (Central Processing Unit) 30UB, a ROM (Read Only Memory) 30UA, a RAM (Random Access Memory) 30UC, and an input / output port 30UD.

In the control unit 30U, the CPU 30UB, ROM 30UA, RAM 30UC, and input / output port 30UD are connected to each other via various buses such as an address bus, a data bus, and a control bus. The detection processing unit 28U, the operation unit 32U, and the like are connected to the input / output port 30UD as various input / output devices.

A calculation program for calculating the optimum gate resistance, a control command program for generating a command for operating the operation unit 32U based on the calculated gate resistance, and the like are installed in the ROM 30UA. In this embodiment, the CPU 30UB executes an arithmetic program to calculate the optimum gate resistance. Further, the CPU 30UB generates a command for operating the operation unit 32U by the control command program. The RAM 30UC is a storage unit that temporarily stores data, and holds, for example, data input from the detection processing unit 28U.

Next, various functions realized by the CPU 30UB of the control unit 30U executing the arithmetic program and the control command program will be described. When the CPU 30UB executes the calculation program and the control command program, the CPU 30UB generates a control command unit for operating the calculation unit 300A and the operation unit 32U for calculating the optimum gate resistance, as shown in FIG. Functions as 300B.

FIG. 4 is a block diagram showing an example of a circuit centered on the comparison function unit 280 included in the detection processing unit 28U. In the comparison function unit 280, the inverting dominant terminal (-) is grounded via the variable capacitor CV ₁ , and the non-inverting input terminal (+) is connected to the voltage divider circuit 280D composed of the capacitor C ₁ and the capacitor C ₂ . It is configured to include a comparator 280C.

The input / output terminal voltage (drain / source voltage V _ds ) detected by the input / output terminal voltage detection unit 24U is input to one end of the capacitor C ₁ of the voltage divider circuit 280D. The voltage between the input / output terminals is divided according to the impedances of the capacitors C ₁ and C ₂ , and is input to the non-inverting input terminal (+) of the comparator 280C.

The comparator 280C compares the voltage value related to the voltage between the input / output terminals input to the non-inverting input terminal (+) with the voltage value input to the inverting input terminal (−). The input value to the inverting input terminal (−) is a threshold value described later, and the threshold value is configured to be changeable by the variable capacitor CV ₁ .

The comparator 280C outputs "1" which is an ON reaction when the input value of the non-inverting input terminal (+) is equal to or higher than the input value of the inverting input terminal (-), and outputs "1" of the non-inverting input terminal (+). It has a digital conversion function that outputs "0", which is an OFF reaction, when the input value becomes less than the input value of the inverting input terminal (-).

The output value of the comparator 280C is input to the calculation unit 300A included in the control unit 30U. The arithmetic unit 300A calculates the optimum gate resistance based on the output value of the comparator 280C and the desired surge voltage command V _{srg *} , and the control command unit 300B operates the operation unit 32U based on the calculated gate resistance. Generate a command to do so. In calculating the optimum gate resistance in the calculation unit 300A, for example, it is necessary to detect the switching surge of the switching element 44U, and a specific method for detecting the switching surge will be described later. Further, depending on the method of detecting the switching surge described later, a plurality of different threshold values may be applied at the same time to detect the switching surge. In such a case, it is shown in FIG. 4 according to the number of threshold values applied at the same time. The comparison function unit 280 is mounted.

Further, in FIG. 4, a case where the surge voltage among the switching surges is detected based on the voltage between the input / output terminals detected by the voltage detection unit 24U between the input / output terminals has been described. When the surge current of the switching surge is detected based on the element current (drain current Id) detected by the element current detection unit _26U , the voltage value that changes according to the element current is compared with the threshold value by the comparator 280C. The voltage value that changes in response to the element current is, for example, a voltage value obtained by appropriately amplifying the potential difference between both terminals of the shunt resistor when the element current detection unit 26U uses a shunt resistor.

Hereinafter, a specific method for detecting a surge peak will be described. In the present embodiment, the surge peak is detected by appropriately using the detection methods described below.

FIG. 5A is an explanatory diagram of surge voltage detection, and FIG. 5B is an explanatory diagram of surge current detection. The surge voltage and surge current are detected in the comparator 280C by comparing the detection values of the input / output terminal voltage detection unit 24U and the element current detection unit 26U with predetermined threshold values.

As shown in FIG. 5A, in the surge voltage V _surge , the voltage between input / output terminals detected by the voltage detection unit 24U between input / output terminals after the gate signal is turned off in the Nth cycle is the first threshold voltage. After the voltage becomes V _th1 or more and the gate signal is turned off again in the (N + 1) cycle, the voltage between the input / output terminals detected by the input / output terminal voltage detection unit 24U is larger than the first threshold voltage V _th1 . 2 Detected when the threshold voltage is less than V _th2 . Specifically, as shown in the following equation (1), it is calculated as an intermediate value between the first threshold voltage V _th1 and the second threshold voltage V _th2 . Since the surge peak can be detected by a relatively simple method that calculates the surge voltage V _surge as an intermediate value between the first threshold voltage V _th1 and the second threshold voltage V _th2 , the cost of detecting the surge voltage V _surge can be suppressed. Can be done. Further, since the calculation load is light, the processing load from the detection to the operation of the active gate control can be reduced.

Then, the gate current of the switching elements 42U to 44W is operated based on the calculated surge voltage V _surge . As an example, when the surge voltage V _surge is larger than the predetermined specified value, the gate current is decreased, and when the surge voltage V _surge is smaller than the predetermined voltage specified value, the gate current is increased. The predetermined voltage specified value is, for example, the center value of the surge upper limit, which is the upper limit value of the voltage determined based on the safe operating region of the switching elements 42U to 44W, and the voltage (+ B voltage) of the DC power supply 80.

As shown in FIG. 5B, the voltage V _{surge_Id} corresponding to the surge current is the voltage corresponding to the element current detected by the element current detection unit 26U after the gate signal is turned on in the Nth cycle. After the 1st threshold voltage V _{th1_Id} or more and the gate signal is turned on again in the (N + 1) cycle, the voltage corresponding to the element current detected by the element current detection unit 26U is larger than the 1st threshold voltage V _{th1_Id} . 2 Detected when the threshold voltage is less than V _{th2_Id} . Specifically, as shown in the following equation (1), it is calculated as an intermediate value between the first threshold voltage V _{th1_Id} and the second threshold voltage V _{th2_Id} . The value of the surge current can be calculated from the surge voltage V _{surge_Id} based on Ohm's law. Then, the gate current of the switching elements 42U to 44W is operated based on the calculated surge voltage V _{surge_Id} . As an example, when the surge voltage V _{surge_Id} is larger than a predetermined specified value, the gate current is lowered, and when the surge voltage V _{surge_Id} is smaller than the predetermined current corresponding specified value, the gate current is increased. The predetermined current correspondence specified value is, for example, an intermediate value between the voltage corresponding to the upper limit value of the current determined based on the safe operating region of the switching elements 42U to 44W and the voltage corresponding to the load current of the switching elements 42U to 44W. Is. In addition, the current of the gate signal is either when the surge voltage V _surge of the voltage between the input / output terminals is larger than the specified voltage value, or when the surge voltage V _{surge_Id} corresponding to the element current is larger than the specified current value. Decrease the value, and increase the current value of the gate signal when the surge voltage V _surge of the input / output terminal voltage is smaller than the specified voltage value and the surge voltage V _{surge_Id} of the element current is smaller than the current corresponding specified value. May be good.

FIG. 6A is an explanatory diagram showing an example of surge waveforms detected at two different threshold values, and FIG. 6B is a surge peak based on the similarity of surge waveforms detected at two different threshold values. It is explanatory drawing in the case of calculating.

As shown in FIG. 6A, the peak value of the surge voltage is derived from the ratio of the surge width t ₁ in the switching of the Nth cycle and the surge width t ₂ in the switching of the (N + 1) th cycle. A section where the voltage between input / output terminals (drain source voltage V _ds ) of the switching elements 42U to 44W is _larger than the threshold voltages V _th1 and V _{th2 when the threshold voltage is changed from V th1 to V th2 different from} V th 1. Will be triangles 400 and 402 that are similar to each other. As a result, the surge voltage can be derived from the similar relationship between the two triangles 400 and 402.

The similarity ratio between the triangle 400 and the triangle 402 is the ratio between the surge width t ₁ and the surge width t ₂ . The surge width t ₁ is the time from when the voltage between the input / output terminals detected by the input / output terminal voltage detection unit 24U in the switching of the Nth cycle becomes the threshold voltage V _th1 or more and becomes the threshold voltage V _th1 or less. be. The surge width t ₂ is from the time when the voltage between the input / output terminals detected by the input / output terminal voltage detection unit 24U in the switching of the (N + 1) th cycle becomes the threshold voltage V _th2 or more and becomes the threshold voltage V _{th 2} or less. It's time.

As shown in FIG. 6B, the height of the triangle 400 is the difference between the surge voltage V _surge and the threshold voltage V _th1 , and the height of the triangle 402 is the difference between the surge voltage V _surge and the threshold voltage V _th2 . Is. Then, the following equation (3) for calculating the surge voltage V _surge is derived from the similarity relationship between the two triangles 400 and 402. In this way, the peak value of the surge voltage can be estimated by calculating the surge voltage V _surge from the similar relationship of the triangles 400 and 402. Further, since the voltage, time and detection can be performed by switching twice, the detection time can be shortened.

V _surge -V _th1 : V _surge -V _th2 = t ₁ : t ₂
V _surge = (V _th1 * t ₂ － V _th2 * t ₁ ) / (t ₂ － t ₁ )… (3)

6 (A) and 6 (B) show the case of calculating the surge voltage V _surge , but the procedure is the same when calculating the surge voltage V _{surge_Id} corresponding to the surge current I _surge . Specifically, the surge voltage V _{surge_Id} is the _following formula based on the result of comparing the voltage value that changes according to the element current (drain current Id) with the first threshold voltage V _{th1_Id} and the second threshold voltage V _{th2_Id} . Calculated according to (4). The surge width t ₁ in the equation (4) becomes the threshold voltage V _{th1_Id} or less after the voltage corresponding to the element current detected by the element current detection unit 26U in the switching of the Nth cycle becomes the threshold voltage V _{th1_Id} or more. It is time to. The surge width t ₂ is the time from when the voltage corresponding to the element current detected by the element current detection unit 26U in the switching of the (N + 1) th cycle becomes the threshold voltage V _{th2_Id} or more and becomes the threshold voltage V _{th2_Id} or less. be.

V _{surge_Id} = (V _{th1_Id} * t ₂ － V _{th2_Id} * t ₁ ) / (t ₂ － t ₁ )… (4)

FIG. 7A is a schematic diagram when the voltage between input / output terminals to be measured is detected at four points, and FIG. 7B is a straight line passing through two points included in the detected four points. It is explanatory drawing for calculating a surge voltage V _surge from the intersection with the straight line passing through the other 2 points included in 4 points.

As shown in FIG. 7A, V _{ds1 and V ds2 ,} which are voltages between input / output terminals having a threshold voltage V _th1 or more, are detected in the switching of the first cycle, and the time t ₁ and the time t 1 at which V _ds 1 is detected are detected. Each of the time t ₂ when V _ds 2 is detected is detected. Then, V _ds3 and V _ds4 , which are the voltages between the voltage between the input / output terminals becoming less than or equal to the surge voltage V _surge and reaching the threshold voltage V _th1 in the second cycle switching, are detected, and V _ds3 is detected. Each of the detected time _{t 3} and the detected time t ₄ is detected. During the period from when the voltage between input / output terminals becomes less than or equal to the surge voltage V _surge in the second cycle switching until the threshold voltage V _th1 is reached, for example, the voltage between input / output terminals detected by the voltage detector unit 24U between input / output terminals. The time differential of is negative, and the voltage between input / output terminals detected by the voltage detection unit 24U between input / output terminals is the threshold voltage V _th1 or more.

FIG. 7B is a straight line passing through a point showing voltage V _ds 1 and time t ₁ and a point showing voltage V _{d s} 2 and time t ₂ in an orthogonal coordinate system assuming time on the horizontal axis and voltage on the vertical axis. The surge voltage V _surge is derived from the intersection of (1), the point indicating the voltage V _ds 3 and the time t ₃ , and the straight line (2) passing through the point indicating the voltage V _ds 4 and the time t ₄ .

As shown in FIG. 7B, assuming that the position corresponding to the origin of the orthogonal coordinates is the threshold voltage 0 and the time 0, the straight line (1) is represented by the following equation (5).

Similarly, the straight line (2) is represented by the following equation (6). In order to define the equation of the straight line (2), the time t ₅ at which the straight line (2) and the straight line V _th1 intersect is separately assumed. The time t ₅ is detected by recording the time when the voltage detected by the voltage detection unit 24U between the input / output terminals coincides with the threshold voltage V _th1 .

Then, the y coordinate of the intersection of the straight line (1) and the straight line (2) becomes the surge voltage V _surge . The x-coordinate of the intersection of the straight line (1) and the straight line (2) is expressed by the following equation (7), and the y-coordinate is expressed by the following equation (8). In this way, the peak value of the surge voltage can be estimated by calculating the surge voltage as the intersection of two straight lines. Further, since the voltage, time and detection can be performed by switching twice, the detection time can be shortened.

7 (A) and 7 (B) show the case of calculating the surge voltage V _surge , but the procedure is the same when calculating the surge voltage V _{surge_Id} corresponding to the surge current I _surge . Specifically, the surge voltage V _{surge_Id} derives the equations of two intersecting straight lines based on the result of comparing the voltage value that changes according to the element current (drain current _{Id) with the threshold voltage V th1_Id .} Calculate the intersection of two straight lines.

FIG. 8A shows that when the voltage between the input / output terminals of the switching elements 42U to 44W is equal to or higher than the initial value of the threshold voltage in the first switching, the threshold voltage is set to a constant value from the initial value in the switching following the first switching. It is explanatory drawing in the case of detecting a surge voltage by increasing it step by step, and FIG. 8 (B) shows the initial value of the threshold voltage that the voltage between input / output terminals of the switching element 42U-44W is the initial value in the first switching. If it is less than, it is an explanatory diagram in the case where the surge voltage is detected by gradually lowering the threshold voltage from the initial value by a constant value in the switching following the first switching.

In FIG. 8A, since the voltage between the input / output terminals shown as the V _ds waveform in the first switching is equal to or higher than the first threshold voltage V _th1 which is the initial value, the voltage is higher than the first threshold voltage V _th1 in the second switching. The large second threshold voltage V _th2 is compared with the voltage between the input / output terminals. As the comparison result in the lower part of FIG. 8A shows an ON reaction, the voltage between the input / output terminals is the second threshold voltage V _th2 or more, so that it is larger than the second threshold voltage V _th2 in the third switching. The third threshold voltage V _th3 and the voltage between the input / output terminals are compared. Since the comparison result in the third switching is an OFF reaction and it can be confirmed that the voltage between the input / output terminals is less than the third threshold voltage V _th3 , it is determined that the surge is detected. The surge voltage V _surge is calculated as an intermediate value between the second threshold voltage V _th2 and the third threshold voltage V _th3 as shown in the following equation (9).

V _surge = (V _th2 + V _th3 ) / 2… (9)

In FIG. 8B, since the voltage between the input / output terminals shown as the V _ds waveform in the first switching is less than the first threshold voltage V _th1 which is the initial value, it is higher than the first threshold voltage V _th1 in the second switching. The small second threshold voltage V _th2 is compared with the voltage between the input / output terminals. As the comparison result in the lower part of FIG. 8B shows an OFF reaction, the voltage between the input / output terminals is less than the second threshold voltage V _th2 , so that it is smaller than the second threshold voltage V _th2 in the third switching. The third threshold voltage V _th3 and the voltage between the input / output terminals are compared. The comparison result in the third switching is an ONN reaction, and it is confirmed that the voltage between the input / output terminals is equal to or higher than the third threshold voltage V _th3 , so that it is determined to be surge detection. Also in the case of FIG. 8B, the surge voltage V _surge is calculated as an intermediate value between the second threshold voltage V _th2 and the third threshold voltage V _th3 as shown in the above equation (9).

In this way, the surge voltage V _surge is calculated as an intermediate value between the ON-reacted threshold voltage V _th and the OFF-reacted threshold voltage V _th based on the results of comparison with a plurality of different threshold voltages V _th . It is possible to prevent the allowable withstand voltage of 42U to 44W from being exceeded, and to quickly detect the surge voltage when the drive capacity is high.

8 (A) and 8 (B) show the case of calculating the surge voltage V _surge , but the procedure is the same when calculating the surge voltage V _{surge_Id} corresponding to the surge current I _surge . Specifically, the surge voltage V _{surge_Id} is an ON-reacted threshold voltage V _{th_Id} and OFF based on the result of comparing a voltage value that changes according to the element current (drain current Id) with a plurality of different threshold voltages V _{th_Id .} Calculated as an intermediate value with the reacted threshold voltage V _{th_Id} .

FIG. 9A is an explanatory diagram showing that the initial value of the threshold voltage V _th is the center value of the surge upper limit of the switching elements 42U to 44W and the voltage of the DC power supply 80 in the case shown in FIG. 8A. 9 (B) shows that the initial value of the threshold voltage V _th is the center value of the surge upper limit of the switching elements 42U to 44 W and the voltage of the DC power supply 80 in the case shown in FIG. 8 (B). It is an explanatory diagram of.

The surge upper limit is a voltage upper limit determined based on the safe operating region of the switching elements 42U to 44W. As shown in FIGS. 9 (A) and 9 (B), the initial value of the threshold voltage V _th is set to the switching element regardless of whether the threshold voltage V _th is gradually increased or decreased. It is effective to set the center value of the surge upper limit of 42U to 44W and the voltage of the DC power supply 80. Further, by setting the initial value of the threshold voltage V _th to the center value of the surge upper limit and the voltage of the DC power supply 80, the detection time can be shortened.

9 (A) and 9 (B) show the case of calculating the initial value of the threshold voltage V _th , but the procedure also shows the case of calculating the threshold voltage V _{th_Id} corresponding to the element current of the switching elements 42U to 44 W. Is similar. Specifically, the initial value is an intermediate value between the voltage corresponding to the upper limit value of the current determined based on the safe operating region of the switching elements 42U to 44W and the voltage corresponding to the load current of the switching elements 42U to 44W. ..

FIG. 10 is an explanatory diagram when the initial value of the threshold voltage V _th is set as the previously detected value in the case shown in FIG. 8 (B). Specifically, the threshold voltage V _th when the voltage between the input / output terminals detected by the voltage detection unit 24U between the input / output terminals becomes equal to or less than the threshold voltage V _th that is gradually increased, and the voltage detection unit between the input / output terminals. It is one of the threshold voltage V _th when the voltage between the input / output terminals detected by the 24U becomes equal to or higher than the threshold voltage V _th that is gradually reduced.

By setting the previously detected value as the initial value of the threshold voltage V _th , the time for determining the threshold voltage V _th can be shortened, and the surge voltage V _surge can be detected quickly.

Similarly, the initial value of the threshold voltage V _{th_Id} corresponding to the element currents of the switching elements 42U to 44W is also equal to or less than the threshold voltage V _{th_Id} in which the voltage corresponding to the element current detected by the element current detection unit 26U is gradually increased. By setting either the threshold voltage V _{th_Id} at that time or the threshold voltage V _{th_Id} when the voltage corresponding to the element current detected by the element current detection unit 26U becomes equal to or higher than the threshold voltage V _{th_Id} which is gradually reduced. The surge voltage V _{surge_Id} can be detected quickly.

FIG. 11 is an explanatory diagram when the initial value of the threshold voltage V _th is the surge voltage (surge peak) derived last time in the case shown in FIG. 8 (A). By setting the surge voltage V _surge detected last time as the initial value of the threshold voltage V _th , the time for determining the threshold voltage V _th can be shortened, and the surge voltage V _surge can be detected quickly.

Similarly, the surge voltage V _{surge_Id} can be quickly detected by _setting the initial value of the threshold voltage V _{th_Id} corresponding to the element current of the switching elements 42U to 44W to the surge voltage V surge_Id detected last time.

FIG. 12A shows that the threshold voltage V _th is increased when the comparison result is ON reaction in the first switching, and the threshold voltage V _th is decreased when the comparison result is different from the previous value in the second and subsequent switchings. It is an explanatory diagram in the case of performing detection again, and FIG. 12B shows that when the comparison result is an OFF reaction in the first switching, the threshold voltage V _th is reduced and the comparison result is obtained in the second and subsequent switchings. It is explanatory drawing in the case of increasing the threshold voltage V _th and performing detection again when it is different from the previous value.

In the case of FIG. 12A, specifically, when the voltage between the input / output terminals detected by the input / output terminal voltage detection unit 24U in the first switching is equal to or higher than the initial value of the first threshold voltage V _th1 , the threshold voltage is reached. After the voltage is sufficiently increased from the initial value of the first threshold voltage V _th1 , the voltage between the input / output terminals detected by the input / output terminal voltage detection unit 24U in the switching following the first switching becomes equal to or higher than the threshold voltage. The threshold voltage is gradually reduced until.

In the case of FIG. 12B, specifically, when the voltage between the input / output terminals detected by the input / output terminal voltage detection unit 24U in the first switching is equal to or less than the first threshold voltage V _th1 which is the initial value, the threshold value is set. After making the voltage V _th sufficiently smaller than the initial value of the first threshold voltage V _th1 , the voltage between the input / output terminals detected by the input / output terminal voltage detection unit 24U in the switching following the first switching is the threshold voltage V. The threshold voltage V _th is gradually increased until it becomes _th or less.

Then, in the case of FIG. 12A, the threshold voltage V _th when the voltage between the input / output terminals detected by the voltage detection unit 24U between the input / output terminals becomes equal to or higher than the threshold voltage V _th that is gradually reduced, and the threshold value. The intermediate value between the threshold voltage V _th , which is one step larger than the voltage V _th , is defined as the surge voltage of the voltage between the input / output terminals. Similarly, in the case of FIG. 12B, the threshold voltage V _th when the voltage between the input / output terminals detected by the input / output terminal voltage detection unit 24U becomes equal to or less than the threshold voltage V _th that is gradually increased, and the corresponding voltage. The intermediate value between the threshold voltage V _th , which is one step smaller than the threshold voltage V _th , is defined as the surge voltage of the voltage between the input / output terminals.

As shown in FIGS. 12A and 12B, the switching elements 42U to 44W are increased or decreased by increasing or decreasing the threshold voltage V _th based on the comparison result between the input / output terminal voltage and the threshold voltage V _th . The surge voltage when the drive capacity of the is low can be calculated with high accuracy.

In FIGS. 12A and 12B, the threshold voltage V _th is increased or decreased based on the comparison result between the input / output terminal voltage and the threshold voltage V _th , but the voltage corresponding to the element current and V _{th_Id} Since the same procedure can be used to increase or decrease the threshold voltage V _{th_Id} based on the comparison result with the above, detailed description thereof will be omitted.

FIG. 13 shows that when the comparison result between the threshold voltage V _th1 which is the initial value in the first switching and the voltage between the input / output terminals is an ON reaction, the threshold value in the subsequent switching is set to the surge of the switching elements 42U to 44W. It is explanatory drawing in the case of changing the threshold voltage V _th1 by adding the threshold addition width which is 1/2 of the difference between the upper limit and the initial value.

In FIG. 13, when the voltage between the input / output terminals detected by the input / output terminal voltage detection unit 24U in the switching following the first switching is the changed threshold voltage V _th2 or more, the subsequent switching in the previous switching The value of 1/2 of the previous threshold addition width is added to the threshold voltage V _th2 , and the threshold is gradually increased until the voltage between the input / output terminals detected by the input / output terminal voltage detection unit 24U becomes equal to or less than the threshold voltage V _th . Increase the voltage V _th .

Then, the threshold voltage V _th (threshold voltage V _th3 in FIG. 13) when the voltage between the input / output terminals detected by the input / output terminal voltage detection unit 24U becomes equal to or less than the threshold voltage V _th that is gradually increased, and the said. The surge voltage of the voltage between the input / output terminals is defined as an intermediate value with the threshold voltage V _th (threshold voltage V _th2 in FIG. 13) which is one step smaller than the threshold voltage V _th . Further, the threshold voltage V _th (threshold voltage V _th3 in FIG. 13) when the voltage between the input / output terminals detected by the input / output terminal voltage detection unit 24U becomes equal to or less than the threshold voltage V _th that is gradually increased is set to the previous value. If the comparison result between the new threshold voltage V _th (threshold voltage V _th4 in FIG. 13) obtained by subtracting the value of 1/2 of the threshold addition width and the voltage between the input / output terminals is an ON reaction, the new threshold is used. The intermediate value between the voltage V _th and the threshold voltage V _th (threshold voltage V _th3 in FIG. 13), which is one step larger than the threshold voltage V _th , is defined as the surge voltage of the voltage between the input / output terminals with higher accuracy.

Similarly, if the voltage between the input / output terminals detected by the input / output terminal voltage detection unit 24U in the switching following the first switching is equal to or less than the changed threshold voltage V _th , the threshold in the previous switching in the subsequent switching The value of 1/2 of the previous threshold voltage subtraction width is subtracted from the voltage V _th , and the threshold voltage is gradually increased until the voltage between the input / output terminals detected by the input / output terminal voltage detection unit 24U becomes equal to or higher than the threshold voltage V _th . Decrease V _th .

Then, the threshold voltage V _th when the voltage between the input / output terminals detected by the input / output terminal voltage detection unit 24U becomes equal to or higher than the threshold voltage V _th that is gradually reduced, and one step larger than the threshold voltage V _th . The intermediate value with the threshold voltage V _th is taken as the surge voltage of the voltage between the input / output terminals. Further, the threshold voltage V _th when the voltage between the input / output terminals detected by the input / output terminal voltage detection unit 24U becomes equal to or less than the threshold voltage V _th that is gradually reduced is a value of 1/2 of the previous threshold addition width. When the comparison result between the new threshold voltage V _th obtained by adding and the voltage between the input / output terminals is an ON reaction, the new threshold voltage V _th and the threshold voltage V one step larger than the threshold voltage V _th are obtained. The intermediate value with _th is taken as the surge voltage of the voltage between the input / output terminals with higher accuracy.

In the case of FIG. 13, the initial value of the threshold voltage V _th is the center value of the surge upper limit of the switching elements 42U to 44W and the voltage of the DC power supply 80. Then, the surge voltage can be detected with high accuracy by increasing or decreasing the threshold voltage V _th stepwise from the initial value based on the comparison result.

FIG. 14 is an explanatory diagram when the initial value of the threshold voltage V _th is set as the previously detected value in the case shown in FIG. Specifically, the threshold voltage V _th when the voltage between the input / output terminals detected by the input / output terminal voltage detection unit 24U becomes equal to or less than the threshold voltage V _th that is gradually increased (threshold voltage V _th3 in FIG. 14). , And the threshold voltage V _th (threshold voltage V _th4 in FIG. 14) when the threshold voltage V _th (threshold voltage V _th3 in FIG. 14) is gradually reduced to the threshold voltage V _th or more. ..

By setting the previously detected value as the initial value of the threshold voltage V _th , the time for determining the threshold voltage V _th can be shortened, and the surge voltage V _surge can be detected quickly.

FIG. 15 is an explanatory diagram in the case shown in FIG. 13 in the case where the initial value of the threshold voltage V _th is the surge voltage derived last time. By setting the surge voltage V _surge detected last time as the initial value of the threshold voltage V _th , the time for determining the threshold voltage V _th can be shortened, and the surge voltage V _surge can be detected quickly.

16 (A) and 16 (B) are explanatory views in the case where two types of different threshold voltages V _th are switched at the timing when the gate signal is switched from OFF to ON and ON to OFF in each switching cycle. Is.

In FIGS. 16A and 16B, the voltage between the input / output terminals shown as the V _ds waveform is compared at each of the initial value of the first threshold value and the initial value of the second threshold value in the Nth cycle. When the voltage between the input / output terminals is equal to or greater than the initial value of the first threshold value and equal to or less than the initial value of the second threshold value, the first threshold value is increased from the initial value and the second threshold value is initially set in the (N + 1) th cycle. Decrease from the value.

In FIG. 16A, the voltage between the input / output terminals is equal to or higher than the first threshold value and the second threshold value in the (N + 1) th cycle. In such a case, the surge voltage V _surge is an intermediate value between the initial value V _th1 of the second threshold value and the changed value V _th2 of the second threshold value obtained by reducing the initial value V _th1 .

In FIG. 16B, the voltage between the input / output terminals is equal to or lower than the first threshold value and the second threshold value in the (N + 1) th cycle. In such a case, the surge voltage V _surge is an intermediate value between the initial value V _th1 of the first threshold value and the changed value V _th2 of the first threshold value obtained by reducing the initial value V _th1 .

Then, the gate current of the switching elements 42U to 44W is operated based on the calculated surge voltage V _surge . As an example, when the surge voltage V _surge is large, the gate current is decreased, and when the surge voltage V _surge is small, the gate current is increased.

In FIGS. 16A and 16B, by using a plurality of threshold values, it is possible to improve the detection accuracy of the surge voltage V _surge and shorten the detection time.

16 (A) and 16 (B) show a case where the surge voltage V _surge is calculated, but the procedure is the same when calculating the surge voltage V _{surge_Id} corresponding to the surge current I _surge . Specifically, the surge voltage V _{surge_Id} is an ON-reacted threshold voltage V _{th_Id} and OFF based on the result of comparing a voltage value that changes according to the element current (drain current Id) with two different threshold voltages V _{th_Id .} Calculated as an intermediate value with the reacted threshold voltage V _{th_Id} .

FIG. 17 compares the voltage between the input / output terminals shown as the V _ds waveform as in FIG. 16A with the initial value of the first threshold value and the initial value of the second threshold value, and the voltage between the input / output terminals is the first. When the value is equal to or more than the initial value of one threshold and is equal to or less than the initial value of the second threshold, the first threshold is gradually increased from the initial value and the second threshold is gradually decreased from the initial value in the subsequent switching. It is explanatory drawing of what to do.

By changing each of the first threshold value and the second threshold value to a smaller width than in the case of FIG. 16A, it is possible to improve the detection accuracy of the surge voltage V _surge .

FIG. 18 is an explanatory diagram of determination of initial values in FIGS. 16 (A), 16 (B) and 17. In FIG. 18, the initial value V _th1 of the first threshold value is the voltage of the DC power supply 80, and the initial value V _th1 of the second threshold value is the upper limit of the voltage determined based on the safe operation region of the switching elements 42U to 44W. This is the upper limit of the surge, which is the value.

FIG. 18 describes the determination of the initial values of the first threshold and the second threshold when calculating the surge voltage V _surge , but the first related to the calculation of the surge voltage V _{surge_Id} of the voltage corresponding to the element current. It is also possible to determine the initial values of the first threshold and the second threshold in the same manner. In such a case, the initial value of the first threshold value is the voltage corresponding to the load current of the switching elements 42U to 44W, and the initial value of the second threshold value is determined based on the safe operation region of the switching elements 42U to 44W. It is the voltage corresponding to the upper limit of the current.

FIG. 19 is an explanatory diagram in the case where a plurality of different threshold voltages V _th are switched at the timing when the gate signal is switched from OFF to ON and ON to OFF in each switching cycle.

In FIG. 19, the input / output terminal voltage detected by the input / output terminal voltage detection unit 24U is compared with each of the initial values of the three types of threshold voltages, the first threshold value, the second threshold value, and the third threshold value, as an example. When the voltage between the input / output terminals detected by the input / output terminal voltage detection unit 24U is equal to or higher than the initial value of each of the three types of threshold voltages, each of the three types of threshold voltages is stepwise changed in the subsequent switching. Increase from the initial value of.

When the voltage between input / output terminals detected by the voltage detection unit 24U between input / output terminals becomes equal to or less than the threshold voltage of any of the three types of threshold voltages gradually increased, the threshold voltage and the threshold voltage thereof. The intermediate value between the threshold voltage and the threshold voltage, which is one step smaller than any of the threshold voltages, is defined as the surge voltage V _surge of the voltage between the input / output terminals.

In FIG. 19, since the input / output terminal voltage detected by the input / output terminal voltage detection unit 24U in the first switching is equal to or higher than the initial values of the first threshold value, the second threshold value, and the third threshold value, in the subsequent switching. , Each of the increased first threshold value, second threshold value, and third threshold value is compared with the voltage between the input / output terminals. As a result, the voltage between the input / output terminals is equal to or higher than the first threshold value and equal to or lower than the second threshold value. Therefore, the surge voltage V _surge is set as an intermediate value between the first threshold value and the second threshold value.

As shown in FIG. 19, by using a plurality of threshold values, it is possible to improve the detection accuracy of the surge voltage V _surge and shorten the detection time.

Although FIG. 19 describes the case of calculating the surge voltage V _surge , the same applies to the case of calculating the surge voltage V _{surge_Id} of the voltage corresponding to the element current. In such a case, the surge voltage V _{surge_Id} is calculated based on the result of comparing the voltages corresponding to the element currents of the switching elements 42U to 44W with three types of threshold values.

FIG. 20 is an explanatory diagram showing an mode of setting three types of threshold values in the case shown in FIG. In FIG. 20, the initial values of each of the three types of threshold values are set with equal differences so that the resolution width is constant, and each of the three types of threshold values is gradually increased by the same predetermined value.

FIG. 21 is an explanatory diagram showing another aspect of setting the three types of threshold values as shown in FIG. In FIG. 21, the initial value of each of the three types of threshold values is equal between the surge upper limit, which is the upper limit value of the voltage determined based on the safe operation region of the switching elements 42U to 44W, and the voltage of the DC power supply 80. It is set to divide into.

In the first switching, the input / output terminal voltage detected by the input / output terminal voltage detection unit 24U is compared with each of the initial values of the three types of thresholds, and the input / output terminals detected by the input / output terminal voltage detection unit 24U. The same number of threshold voltages as the initial value is reset so as to evenly divide the range between the maximum value of the initial value smaller than the interim voltage and the initial value one step larger than the maximum value. If the maximum value is the maximum value of the initial value, the same number of threshold voltages as the initial value is reset so as to evenly divide the range between the maximum value and the surge upper limit.

Then, when the voltage between the input / output terminals detected by the voltage detection unit 24U between the input / output terminals becomes equal to or less than the threshold voltage of any of the plurality of reset threshold voltages, the threshold voltage of any of the threshold voltages and any of the threshold voltages are obtained. The intermediate value between the threshold voltage and the threshold voltage, which is one step smaller than the threshold voltage, is defined as the surge voltage V _surge of the voltage between the input / output terminals. Alternatively, if the voltage between the input / output terminals detected by the voltage detection unit 24U between the input / output terminals is larger than any of the plurality of reset threshold voltages, the maximum value of the plurality of reset threshold voltages and the upper limit of the surge are set. The intermediate value is the surge voltage V _surge of the voltage between the input and output terminals.

As described above, by using the plurality of threshold values, the detection time of the surge voltage V _surge can be shortened, and the interval between the plurality of threshold values can be gradually narrowed to improve the detection accuracy of the surge voltage V _surge .

Although FIG. 21 describes the case of calculating the surge voltage V _surge , the same applies to the case of calculating the surge voltage V _{surge_Id} of the voltage corresponding to the element current. In such a case, the surge voltage V _{surge_Id} is calculated based on the result of comparing the voltages corresponding to the element currents of the switching elements 42U to 44W with three types of thresholds in which the intervals are gradually narrowed.

FIG. 22 is an explanatory diagram in the case where the voltage between the input / output terminals of the switching elements 42U to 44W is compared with the first threshold voltage V _th1 and the second threshold voltage V _th2 when the motor phase currents are substantially the same. As described above, in the actual motor rotation control, a three-phase AC voltage is generated and applied to the coils of each phase of the motor 12 by PWM control that turns each of the switching elements 42U to 44W on and off in small steps. The motor phase current supplied to the motor 12 changes in a substantially sinusoidal shape as shown in the middle stage of FIG. 22. When the motor phase current is different, the V _ds waveform, which is the waveform of the voltage between the input / output terminals, is also different. The V _ds waveform at the timing when the motor phase current is high tends to be steep as shown in the upper part of FIG. Further, as shown in the lower part of FIG. 22, the V _ds waveform at the timing when the motor phase current is low tends to be gentler than the V _ds waveform at the timing when the motor phase current is high.

As shown in FIG. 22, when the motor phase currents are different, the V _ds waveforms are different. In this modification, the detection by the first threshold voltage V _th1 and the detection by the second threshold voltage V _th2 higher than the first threshold voltage V _th1 are performed at the timing when the motor phase currents appearing in each electric angle cycle are substantially the same. The surge voltage V _surge is calculated. Since the V _ds waveforms are almost the same at the timing when the motor phase currents are substantially the same, the surge voltage V _surge can be calculated accurately, and as a result, the gate current can be controlled with high accuracy. As an example, the timing at which the motor phase currents are substantially the same is detected as the same timing within the electrical angular cycle by counting the control clock of the control unit 30U.

Further, by detecting the timing at which the motor phase currents are substantially the same for each electric angle cycle and performing detection by the first threshold voltage V _th1 and detection by the second threshold voltage V _th2 , the gate drivers 20U to 22W can be used. The load can be reduced.

Although FIG. 22 shows the case where the surge voltage V _surge is calculated, the surge voltage V _{surge_Id} corresponding to the element currents of the switching elements 42U to 44W can be calculated by the same procedure.

FIG. 23 shows a case where the voltage between the input / output terminals of the switching elements 42U to 44W is compared with the first threshold voltage V _th1 and the second threshold voltage V _th2 when the motor phase currents are substantially the same in the same electric angle cycle. It is an explanatory diagram of. As for the motor phase current that changes in a substantially sinusoidal shape, the same value appears twice in the same electric angle period unless it is a maximum value or a minimum value. In this modification, the motor phase currents that appear twice in the same electrical angle cycle are detected by the first threshold voltage V _th1 and the detection by the second threshold voltage V _th2 different from the first threshold voltage V _th1 at substantially the same timing. To calculate the surge voltage V _surge . As described above, since the V _ds waveforms are almost the same at the timing when the motor phase currents are substantially the same, the surge voltage V _surge can be calculated accurately, and as a result, the gate current can be controlled with high accuracy.

As an example, the timing at which the motor phase currents are substantially the same within the same electric angle cycle is detected by counting the control clock of the control unit 30U within the electric angle cycle.

Further, since the timing at which the motor phase currents are substantially the same within the same electric angle cycle is longer than the switching cycle of the switching elements 42U to 44W in PWM control, the frequency of low threshold value detection and high threshold value detection per unit time can be determined. It can be suppressed, and as a result, the load of the gate driver 20U to 22W can be reduced.

Although FIG. 23 shows the case where the surge voltage V _surge is calculated, the surge voltage V _{surge_Id} corresponding to the element currents of the switching elements 42U to 44W can also be calculated by the same procedure.

FIG. 24 is an explanatory diagram in the case where a thinning section is provided between the detection section for comparing the voltage and the threshold voltage and the control calculation section for calculating the surge voltage V _surge or the surge voltage V _{surge_Id} from the comparison result. In the present embodiment, basically, for each switching of the switching elements 42U to 44W by PWM control, surge detection and surge voltage V _surge comparing the voltage corresponding to the input / output terminal voltage or the element current with the threshold voltage. Alternatively, the control calculation for calculating the surge voltage V _{surge_Id} and the operation of the gate current are performed, but in such an operation, the load of the gate drivers 20U to 22W becomes a problem.

In the case shown in FIG. 24, a thinning section in which surge detection is not performed is provided, and a control operation for calculating the surge voltage V _surge or the surge voltage V _{surge_Id} is performed following the thinning section. The thinning section is performed, for example, by the control unit 30U outputting an operation stop signal to each of the input / output terminal voltage detection unit 24U and the element current detection unit 26U. After calculating the surge voltage V _surge or the surge voltage V _{surge_Id} , the gate current is operated through the thinning section. Then, after the operation, surge detection is performed again. The thinning section is a section including at least one switching, and may extend to a plurality of switchings.

FIG. 25 shows a detection section for comparing the voltage and the threshold voltage, a control calculation section for calculating the surge voltage V _surge or the surge voltage V _{surge_Id} from the comparison result, and a control calculation section and an operation section for operating the gate current. It is explanatory drawing in the case where the thinning section is provided in each of the space.

FIG. 26 is an explanatory diagram when a thinning section is provided after controlling the gate current. As shown in FIG. 26, a thinning section is provided in which detection, calculation, and operation are not performed during at least one switching after the operation of the gate current.

As shown in FIGS. 24, 25, and 26, the load on the gate drivers 20U to 22W can be reduced by providing a thinning section in which surge detection, calculation, and operation are not performed.

FIG. 27 is an explanatory diagram when the thinning section is set according to the motor phase current. As shown in FIG. 27, the motor phase current supplied to the motor 12 changes in a substantially sinusoidal shape. When the motor phase current is large, the load of the gate drivers 20U to 22W also increases accordingly. Therefore, when the motor phase current is large, a thinning section is provided between the surge detection section and the control calculation section, and between the control calculation section and the operation section. If the motor phase current is small, no thinning section is provided. If the motor phase current is medium, either between the surge detection section and the control calculation section, or between the control calculation section and the operation section. A thinning section will be provided in.

Since the effect of AGC is considered to be remarkable when the motor phase current is low, the load of the gate driver 20U to 22W is small. When the motor phase current is low, surge detection, calculation, and operation are positively performed. Is recommended. At the same time, the load on the gate drivers 20U to 22W can be reduced by suppressing surge detection, calculation, and operation when the motor phase current is high.

As described above, according to the present embodiment, it is possible to obtain a switching element drive circuit that realizes simplification of the detection function and reduction of the processing load of control.

In the present embodiment, one unit cycle is from when the gate signal is turned off to when it is turned on and immediately before it is turned off again or until when the gate signal is turned on and then turned off and immediately before it is turned on again. Then, the threshold value to be compared with the voltage of the switching element is switched for each switching cycle, and if it is different from the previous determination result, it is determined that there is a surge peak between the previous threshold value and the current threshold value. In this way, one cycle is set as the detection section by the first threshold value, and the cycle following the detection section is set as the detection section by the second threshold value different from the first threshold value, so that the control terminal voltage using the threshold value is used. It is possible to suppress the load of the gate drivers 20U to 22W related to the detection of changes such as.

Two different thresholds may be used in the detection of the surge peak, or three or more different thresholds may be used. By using a plurality of threshold values of three or more, it is possible to accurately detect the surge peak.

In the present embodiment, as shown in FIG. 4, since a simple configuration in which the voltage related to the switching of the switching element and the threshold value are compared by the comparator 280C is adopted, the detection function can be simplified.

By controlling the gate current based on the calculated surge peak, it is possible to suppress the occurrence of a surge peak that exceeds the surge upper limit of the switching element.

Further, the load on the gate drivers 20U to 22W can be reduced by appropriately providing a thinning section in which surge detection, calculation, and operation are not performed.

In this embodiment, since the comparator 280C that performs voltage comparison is adopted for threshold comparison, the surge voltage V _{surge_Id} is calculated by comparing the voltage corresponding to the element current with the threshold voltage V _{surge_Id} , but the current values are compared. The surge current I _surge may be calculated by comparing the element current with the threshold current I _th by adopting a circuit configuration capable of the above.

10 Inverter, 12 motor, 22U gate driver, 24U input / output terminal voltage detection unit, 26U element current detection unit, 28U detection processing unit, 30U control unit, 32U operation unit, 32UF, 32UO variable resistor, 44U switching element, 80 DC power supply, 280 comparison function unit, 280C comparator, 300A arithmetic unit, 300B control command unit, 400, 402 triangle, _{Id drain current, V ds1, V ds2 , V ds3} , V _ds4 voltage, V _ds drain source voltage, V _surge surge voltage, V _th , V _th1 , V _th2 , V _th3 , V _th4 , V _{th_Id} , V _{th1_Id} , V _{th2_Id} , threshold voltage, t ₁ , t ₂ , t ₃ , t ₄ , t ₅ hours

Claims (35)

A voltage between input / output terminals when a switching element (44U) having a control terminal and an input / output terminal and switched between the input / output terminals according to an electric signal input to the control terminal is switched in a different switching cycle. Input / output terminal voltage detector (24U) to detect
A current detection unit (26U) that detects the element current of the switching element (44U) switched in the different switching cycles, and
It is the result of comparing the voltage between the input / output terminals and the threshold voltage switched according to the switching cycle, and the result of comparing the element current with the threshold current switched according to the switching cycle. A signal processing unit (28U) that outputs the current comparison result, and
When the voltage comparison result in the first switching cycle and the voltage comparison result in the second switching cycle different from the first switching cycle are different, the threshold current in the first switching cycle and the second switching cycle When the current comparison result in the first switching cycle and the current comparison result in the second switching cycle are different from each other, the intermediate value with the threshold voltage in is set as the surge peak of the voltage between the input / output terminals. The intermediate value between the threshold current in the switching cycle and the threshold current in the second switching cycle is set as the surge peak of the element current, and when the surge peak of the voltage between the input / output terminals is larger than the specified voltage value, and the element. The current value of the electric signal is reduced in any case where the surge peak of the current is larger than the specified current value, the surge peak of the voltage between the input / output terminals is smaller than the specified voltage value, and the element current. A control unit (30U) that controls to increase the current value of the electric signal when the surge peak of the current is smaller than the specified current value.
Switching element drive circuit including. The threshold voltage includes a first threshold voltage and a second threshold voltage larger than the first threshold voltage.
In the control unit (30U), the output result of the signal processing unit (28U) is the input / output terminal voltage detected by the input / output terminal voltage detection unit (24U) in the first switching cycle. When the voltage between the input / output terminals is equal to or higher than the threshold voltage and the voltage between the input / output terminals detected by the input / output terminal voltage detection unit (24U) in the second switching cycle is equal to or lower than the second threshold voltage, the first threshold voltage and the said. The switching element drive circuit according to claim 1, wherein an intermediate value with the second threshold voltage is set as a surge peak of the voltage between the input / output terminals. The threshold current includes a first threshold current and a second threshold current larger than the first threshold current.
In the control unit (30U), the output result of the signal processing unit (28U) is that the element current detected by the current detection unit (26U) in the first switching cycle is equal to or higher than the first threshold current. When the element current detected by the current detection unit (26U) in the second switching cycle is equal to or less than the second threshold current, the intermediate value between the first threshold current and the second threshold current is set as the surge of the element current. The switching element drive circuit according to claim 1, wherein the peak is used. The threshold voltage includes a first threshold voltage and a second threshold voltage larger than the first threshold voltage.
The signal processing unit (28U) is the first after the voltage between the input / output terminals detected by the voltage detection unit (24U) between the input / output terminals in the first switching cycle becomes equal to or higher than the first threshold voltage. After the first time until the voltage becomes equal to or lower than the threshold voltage and the voltage between the input / output terminals detected by the input / output terminal voltage detection unit (24U) in the second switching cycle becomes equal to or higher than the second threshold voltage. The second time until the voltage becomes equal to or lower than the second threshold voltage is detected.
The control unit (30U) has a difference between the surge peak of the voltage between the input / output terminals and the first threshold voltage, and a difference between the surge peak of the voltage between the input / output terminals and the second threshold voltage. The switching element drive circuit according to claim 1, wherein the surge peak of the voltage between the input / output terminals is derived based on the ratio equal to the ratio of the first time and the second time. The threshold current includes a first threshold current and a second threshold current larger than the first threshold current.
The signal processing unit (28U) has the element current detected by the current detection unit (26U) in the first switching cycle from the time when the element current becomes equal to or more than the first threshold current to the time when the element current becomes equal to or less than the first threshold current. 1st time and the 2nd time from when the element current detected by the current detection unit (26U) in the 2nd switching cycle becomes equal to or more than the 2nd threshold current to becomes equal to or less than the 2nd threshold current. And detect,
In the control unit (30U), the ratio of the difference between the surge peak of the element current and the first threshold current and the difference between the surge peak of the element current and the second threshold current is the first time. The switching element drive circuit according to claim 1, wherein a surge peak of the element current is derived based on the ratio equal to the second time. The signal processing unit (28U) has a different first unit from the time when the voltage between the input / output terminals detected by the input / output terminal voltage detection unit (24U) becomes equal to or higher than the threshold voltage until the surge peak is reached. The voltage and the second voltage are extracted in association with each detection time, and the voltage between the input / output terminals detected by the input / output terminal voltage detection unit (24U) becomes the threshold voltage after the surge peak or less. Different third and fourth voltages until they are reached are extracted in association with each detection time.
The control unit (30U) indicates a point indicating the detection time of the first voltage and the first voltage in an orthogonal coordinate system assuming time on the horizontal axis and voltage on the vertical axis, and the second voltage and the second voltage. A straight line passing through a point indicating the voltage detection time, a straight line passing through the point indicating the detection time of the third voltage and the third voltage, and a point indicating the detection time of the fourth voltage and the fourth voltage. The switching element drive circuit according to claim 1, wherein a surge peak of the voltage between input / output terminals is derived from the intersection of the above. The signal processing unit (28U) has different first currents and first currents from the time when the element current detected by the current detection unit (26U) becomes equal to or higher than the threshold current until the surge peak of the element current is reached. The two currents are extracted in association with each detection time, and the element current detected by the current detection unit (26U) is different from the time when the element current is equal to or less than the surge peak of the element current until the threshold current is reached. The third current and the fourth current are extracted in association with each detection time.
The control unit (30U) indicates a point indicating the detection time of the first current and the first current in an orthogonal coordinate system assuming time on the horizontal axis and current on the vertical axis, and the second current and the second current. A straight line passing through a point indicating the current detection time, a straight line passing through the point indicating the detection time of the third current and the third current, and a point indicating the detection time of the fourth current and the fourth current. The switching element drive circuit according to claim 1, wherein a surge peak of the element current is derived from the intersection of the above. When the voltage between input / output terminals detected by the voltage detection unit (24U) between input / output terminals in the first switching cycle is equal to or higher than the initial value of the threshold voltage, the signal processing unit (28U) performs the first switching. In the switching cycle following the cycle, the threshold voltage is gradually increased from the initial value until the voltage between the input / output terminals detected by the input / output terminal voltage detection unit (24U) becomes equal to or lower than the threshold voltage, and the switching element is used. When the voltage between input / output terminals detected by the voltage detection unit (24U) between input / output terminals in the first switching cycle of (44U) is equal to or less than the initial value of the threshold voltage, the voltage following the first switching cycle is followed. The threshold voltage is gradually reduced from the initial value until the voltage between the input / output terminals detected by the input / output terminal voltage detection unit (24U) becomes equal to or higher than the threshold voltage in the switching cycle.
The control unit (30U) has a threshold voltage when the voltage between the input / output terminals detected by the input / output terminal voltage detection unit (24U) becomes equal to or less than the threshold voltage gradually increased, and the threshold voltage is higher than the threshold voltage. The intermediate value with the threshold voltage one step smaller is set as the surge peak of the voltage between the input / output terminals, and the voltage between the input / output terminals detected by the voltage detection unit (24U) between the input / output terminals is equal to or higher than the threshold voltage gradually reduced. The switching element drive circuit according to claim 1, wherein an intermediate value between the threshold voltage at the time of failure and a threshold voltage one step larger than the threshold voltage is set as a surge peak of the voltage between the input / output terminals. When the input / output terminal voltage detected by the input / output terminal voltage detection unit (24U) in the first switching cycle is equal to or higher than the initial value of the threshold voltage, the signal processing unit (28U) sets the threshold voltage to the initial value. After sufficiently increasing the value from the value, the voltage between the input / output terminals detected by the input / output terminal voltage detection unit (24U) in the switching cycle following the first switching cycle becomes equal to or higher than the threshold voltage in stages. When the threshold voltage is reduced and the voltage between the input / output terminals detected by the voltage detection unit (24U) between the input / output terminals in the first switching cycle of the switching element (44U) is equal to or less than the initial value of the threshold voltage, the threshold voltage is set. After the voltage is sufficiently reduced from the initial value, until the voltage between the input / output terminals detected by the input / output terminal voltage detection unit (24U) becomes equal to or less than the threshold voltage in the switching cycle following the first switching cycle. , Gradually increase the threshold voltage,
The control unit (30U) has a threshold voltage when the voltage between the input / output terminals detected by the input / output terminal voltage detection unit (24U) becomes equal to or higher than the threshold voltage gradually reduced, and the threshold voltage is higher than the threshold voltage. The intermediate value with the threshold voltage one step higher is set as the surge peak of the voltage between the input / output terminals, and the voltage between the input / output terminals detected by the voltage detection unit (24U) between the input / output terminals is equal to or less than the threshold voltage gradually increased. The switching element drive circuit according to claim 1, wherein an intermediate value between the threshold voltage at the time of becoming the threshold voltage and the threshold voltage one step smaller than the threshold voltage is set as the surge peak of the voltage between the input / output terminals. When the voltage between the input / output terminals detected by the voltage detection unit (24U) between the input / output terminals in the first switching cycle is equal to or higher than the initial value of the threshold voltage, the signal processing unit (28U) sets the initial value to the initial value. The threshold voltage is changed by adding the threshold addition width of 1/2 of the difference between the upper limit value of the voltage determined based on the safe operation region of the switching element (44U) and the initial value to change the threshold voltage, and the first switching cycle is performed. When the voltage between input / output terminals detected by the voltage detection unit (24U) between input / output terminals is equal to or less than the initial value of the threshold voltage, the initial value is connected to the initial value and the input / output terminals of the switching element (44U). The switching element drive circuit according to claim 9, wherein the threshold voltage is changed by subtracting a value of ½ of the difference from the voltage of the DC power supply. When the input / output terminal voltage detected by the input / output terminal voltage detection unit (24U) is equal to or higher than the changed threshold voltage in the switching cycle following the first switching cycle, the signal processing unit (28U) In the subsequent switching cycle, the voltage between the input / output terminals detected by the input / output terminal voltage detection unit (24U) is calculated by adding the value of 1/2 of the previous threshold addition width to the threshold voltage in the previous switching cycle. The threshold voltage is gradually increased until it becomes equal to or lower than the threshold voltage, and the voltage between the input / output terminals detected by the input / output terminal voltage detection unit (24U) in the switching cycle following the first switching cycle is changed. When the voltage is equal to or lower than the threshold voltage, the voltage detection unit (24U) between the input / output terminals detects by subtracting a value of 1/2 of the previous threshold subtraction width from the threshold voltage in the previous switching cycle in the subsequent switching cycle. The switching element drive circuit according to claim 10, wherein the threshold voltage is gradually reduced until the voltage between the input / output terminals becomes equal to or higher than the threshold voltage. When the element current detected by the current detection unit (26U) in the first switching cycle is equal to or greater than the initial value of the threshold current, the signal processing unit (28U) is in the switching cycle following the first switching cycle. The threshold current is gradually increased from the initial value until the element current detected by the current detection unit (26U) becomes equal to or less than the threshold current, and the current detection is performed in the first switching cycle of the switching element (44U). When the element current detected by the unit (26U) is equal to or less than the initial value of the threshold current, the element current detected by the current detection unit (26U) becomes equal to or greater than the threshold current in the switching cycle following the first switching cycle. The threshold current is gradually reduced from the initial value until
The control unit (30U) has a threshold current when the element current detected by the current detection unit (26U) becomes equal to or less than the gradually increased threshold current, and a threshold current one step smaller than the threshold current. The intermediate value is set as the surge peak of the element current, and the threshold current when the element current detected by the current detection unit (26U) becomes equal to or greater than the threshold current gradually reduced and the threshold one step larger than the threshold current. The switching element drive circuit according to claim 1, wherein an intermediate value with the current is set as a surge peak of the element current. When the element current detected by the current detection unit (26U) in the first switching cycle is equal to or greater than the initial value of the threshold current, the signal processing unit (28U) sufficiently increases the threshold current from the initial value. The threshold current of the switching element (44U) is gradually reduced until the element current detected by the current detection unit (26U) becomes equal to or higher than the threshold current in the switching cycle following the first switching cycle. When the element current detected by the current detection unit (26U) in the first switching cycle is equal to or less than the initial value of the threshold current, the threshold current is sufficiently reduced from the initial value, and then the first switching cycle is followed. The threshold current is gradually increased until the element current detected by the current detection unit (26U) in the switching cycle becomes equal to or less than the threshold current.
The control unit (30U) has a threshold current when the element current detected by the current detection unit (26U) becomes equal to or higher than the threshold current gradually reduced, and a threshold current one step larger than the threshold current. The intermediate value is set as the surge peak of the element current, and the threshold current when the element current detected by the current detection unit (26U) becomes equal to or less than the gradually increased threshold current and the threshold one step smaller than the threshold current. The switching element drive circuit according to claim 1, wherein an intermediate value with the current is set as a surge peak of the element current. The initial value of the threshold voltage is intermediate between the upper limit value of the voltage determined based on the safe operating region of the switching element (44U) and the voltage of the DC power supply connected to the input / output terminal of the switching element (44U). The switching element drive circuit according to any one of claims 8 to 11, which is a value. The initial value of the threshold current is the intermediate value between the upper limit value of the current determined based on the safe operating region of the switching element (44U) and the load current of the switching element (44U), according to claim 12 or 13. The switching element drive circuit described. The initial value of the threshold voltage is the threshold voltage when the voltage between the input / output terminals detected by the input / output terminal voltage detection unit (24U) becomes equal to or less than the threshold voltage gradually increased, and the threshold voltage between the input / output terminals. The switching element according to any one of claims 8 to 11, which is one of the threshold voltages when the voltage between input / output terminals detected by the voltage detection unit (24U) becomes equal to or higher than the threshold voltage gradually reduced. Drive circuit. The initial value of the threshold current is the threshold current when the element current detected by the current detection unit (26U) becomes equal to or less than the gradually increased threshold current, and the element current detected by the current detection unit (26U). The switching element drive circuit according to claim 12, wherein is any of the threshold currents when the current becomes equal to or higher than the threshold current gradually reduced. The switching element drive circuit according to any one of claims 8 to 11, wherein the initial value of the threshold voltage is a surge peak of the voltage between input / output terminals derived last time. The switching element drive circuit according to claim 12, wherein the initial value of the threshold current is a surge peak of the element current derived last time. The threshold voltage includes a first threshold voltage and a second threshold voltage larger than the first threshold voltage.
The signal processing unit (28U) uses the voltage between the input / output terminals detected by the voltage detection unit (24U) between the input / output terminals as the initial value of the first threshold voltage and the initial value of the second threshold voltage. By comparison, in the first switching cycle, the voltage between the input / output terminals detected by the voltage detection unit (24U) between the input / output terminals is equal to or higher than the initial value of the first threshold voltage and is of the second threshold voltage. When it is equal to or less than the initial value, in the switching cycle following the first switching cycle, the first threshold voltage is gradually increased from the initial value and the second threshold voltage is gradually decreased.
The control unit (30U) includes a first threshold voltage when the voltage between the input / output terminals detected by the input / output terminal voltage detection unit (24U) becomes equal to or lower than the first threshold voltage gradually increased. The intermediate value with the first threshold voltage, which is one step smaller than the first threshold voltage, is set as the surge peak of the input / output terminal voltage, and the input / output terminal voltage detected by the input / output terminal voltage detection unit (24U) is the step. The intermediate value between the second threshold voltage when the voltage becomes smaller than the second threshold voltage and the second threshold voltage one step larger than the second threshold voltage is defined as the surge peak of the voltage between the input / output terminals. The switching element drive circuit according to claim 1. The initial value of the first threshold voltage is the voltage of the DC power supply connected to the input / output terminal of the switching element (44U), and the initial value of the second threshold voltage is the safe operation of the switching element (44U). The switching element drive circuit according to claim 20, which is an upper limit value of a voltage determined based on a region. The threshold current includes a first threshold current and a second threshold current larger than the first threshold current.
The signal processing unit (28U) compares the element current detected by the current detection unit (26U) with each of the initial value of the first threshold current and the initial value of the second threshold current, and the first In the switching cycle, when the element current detected by the current detection unit (26U) is equal to or greater than the initial value of the first threshold current and equal to or less than the initial value of the second threshold current, the first switching cycle is performed. In the subsequent switching cycle, the first threshold current is gradually increased from the initial value, and the second threshold current is gradually decreased.
The control unit (30U) is one with a first threshold current when the element current detected by the current detection unit (26U) becomes equal to or less than the first threshold current gradually increased, and one with respect to the first threshold current. The intermediate value with the first threshold current that is step smaller is set as the surge peak of the element current, and the second threshold when the element current detected by the current detection unit (26U) becomes equal to or greater than the second threshold current that is stepwise reduced. The switching element drive circuit according to claim 1, wherein an intermediate value between the current and a second threshold current one step larger than the second threshold current is a surge peak of the element current. The initial value of the first threshold current is the load current of the switching element (44U), and the initial value of the second threshold current is the current determined based on the safe operating region of the switching element (44U). The switching element drive circuit according to claim 22, which is an upper limit value. The threshold voltage includes a plurality of different threshold voltages.
The signal processing unit (28U) compares the voltage between the input / output terminals detected by the voltage detection unit (24U) between the input / output terminals with each of the initial values of the plurality of threshold voltages, and the first switching cycle. In the switching cycle following the first switching cycle, when the voltage between the input / output terminals detected by the voltage detection unit (24U) between the input / output terminals is equal to or higher than the initial value of each of the plurality of threshold voltages. , Each of the plurality of threshold voltages is gradually increased from the initial value of each.
When the voltage between the input / output terminals detected by the voltage detection unit (24U) between the input / output terminals becomes equal to or less than the threshold voltage of any of the plurality of threshold voltages gradually increased by the control unit (30U). The switching element drive circuit according to claim 1, wherein an intermediate value between the threshold voltage and the threshold voltage one step smaller than the threshold voltage is set as the surge peak of the voltage between the input / output terminals. Each of the initial values of the plurality of threshold voltages is set by an arithmetic progression.
The switching element drive circuit according to claim 24, wherein the signal processing unit (28U) increases each of the plurality of threshold voltages stepwise at the same predetermined value. The threshold current includes a plurality of different threshold currents.
The signal processing unit (28U) compares the element current detected by the current detection unit (26U) with each of the initial values of the plurality of threshold currents, and in the first switching cycle, the current detection unit ( When the element current detected by 26U) is equal to or higher than the initial value of each of the plurality of threshold currents, in the switching cycle following the first switching cycle, each of the plurality of threshold currents is stepped by each. Increase from the initial value,
When the element current detected by the current detection unit (26U) becomes equal to or less than the threshold current of any of the plurality of threshold currents gradually increased, the control unit (30U) has one of the threshold currents. The switching element drive circuit according to claim 1, wherein an intermediate value between the current and a threshold current one step smaller than any of the threshold currents is set as a surge peak of the element current. Each of the initial values of the plurality of threshold currents is set by arithmetic progression.
The switching element drive circuit according to claim 26, wherein the signal processing unit (28U) increases each of the plurality of threshold currents step by step with the same predetermined value. The threshold voltage includes a plurality of different threshold voltages.
The initial values of the plurality of threshold voltages are the upper limit value of the voltage determined based on the safe operating region of the switching element (44U) and the voltage of the DC power supply connected to the input / output terminal of the switching element (44U). Set to divide evenly between
The signal processing unit (28U) compares the voltage between the input / output terminals detected by the voltage detection unit (24U) between the input / output terminals in the first switching cycle with each of the initial values of the plurality of threshold voltages. Then, the range between the maximum value of the initial value smaller than the input / output terminal voltage detected by the input / output terminal voltage detection unit (24U) and the initial value one step larger than the maximum value, or the maximum value. If is the maximum value of the initial value, the same number of threshold voltages as the initial value is reset so as to divide the range between the maximum value and the upper limit value evenly.
When the voltage between input / output terminals detected by the voltage detection unit (24U) between input / output terminals becomes equal to or less than the threshold voltage of any of the plurality of reset threshold voltages, the control unit (30U) said. The intermediate value between any of the threshold voltages and the threshold voltage one step smaller than the threshold voltage was set as the surge peak of the voltage between the input / output terminals, and was detected by the voltage detection unit (24U) between the input / output terminals. When the voltage between the input / output terminals is larger than any of the plurality of reset threshold voltages, the surge peak of the voltage between the input / output terminals is set to an intermediate value between the maximum value of the plurality of reset threshold voltages and the upper limit value. The switching element drive circuit according to claim 1. The threshold current includes a plurality of different threshold currents.
The initial value of the plurality of threshold currents is such that the upper limit value of the current determined based on the safe operating region of the switching element (44U) and the load current of the switching element (44U) are evenly divided. Set,
The signal processing unit (28U) compares the element current detected by the current detection unit (26U) with each of the initial values of the plurality of threshold currents in the first switching cycle, and the current detection unit (28U) The range between the maximum value of the initial value smaller than the element current detected by 26U) and the initial value one step larger than the maximum value, or if the maximum value is the maximum value of the initial value, the maximum value The same number of threshold currents as the initial value is reset so that the range between the upper limit value and the upper limit value is divided evenly.
The control unit (30U) determines that the element current detected by the current detection unit (26U) is equal to or less than the threshold current of any of the plurality of reset threshold currents. An intermediate value with a threshold current one step smaller than any of the threshold currents is set as a surge peak of the element current, and the element current detected by the current detection unit (26U) is higher than any of the plurality of reset threshold currents. The switching element drive circuit according to claim 1, wherein the surge peak of the element current is an intermediate value between the maximum value of the plurality of resettled currents and the upper limit value that have been reset. In the second switching cycle of the switching element (44U), the current supplied from the switching element (44U) to the power load is transferred from the switching element (44U) to the power load during the first switching cycle. The switching element drive circuit according to claim 2 or 3, which is a switching cycle at a timing that appears at every electric angle cycle that is substantially the same as the supplied current. In the second switching cycle, in the same electric angular cycle, the current supplied from the switching element (44U) to the power load is transferred from the switching element (44U) to the power load during the first switching cycle. The switching element drive circuit according to claim 2 or 3, which is a switching cycle at a timing substantially the same as the supplied current. 2. The switching element drive circuit described. Between the detection using each of the input / output terminal voltage detection unit (24U) and the current detection unit (26U) and the derivation of the surge peak by the control unit (30U), and the surge by the control unit (30U). Detection using each of the input / output terminal voltage detection unit (24U) and the current detection unit (26U) for each of the derivation of the peak and the control of the electric signal by the control unit (30U), said. The switching element drive circuit according to claim 2 or 3, wherein a thinning section for stopping the derivation of the surge peak by the control unit (30U) and the control of the electric signal by the control unit (30U) is provided between the switching cycles. After the control of the electric signal by the control unit (30U), detection using each of the input / output terminal voltage detection unit (24U) and the current detection unit (26U), and a surge peak by the control unit (30U). The switching element drive circuit according to claim 2 or 3, wherein a thinning section for stopping the derivation of the electric signal and the control of the electric signal by the control unit (30U) is provided between the switching cycles. The switching element drive circuit according to any one of claims 32 to 34, wherein the thinning section is set according to a current supplied from the switching element (44U) to a power load.

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