JP7635436B2 - Power Conversion Equipment - Google Patents

Description

The present invention relates to a power conversion device.

Patent Document 1 is known as a technology that can detect abnormalities in a power conversion device. Patent Document 1 discloses a technology that detects abnormalities in a braking circuit that passes current to a braking resistor that consumes energy during regenerative operation of the power conversion device.

JP 2019-176601 A

A power conversion device receives AC power, converts it to DC power using a rectifier circuit, and then converts it back to AC using an inverter. The inverter section is often made up of power semiconductors, which are switching elements. The control circuit that controls the power conversion device is an electronic circuit that uses a microcontroller or other ICs, as well as resistors and capacitors. The control circuit components are generally mounted on a circuit board.

When the output capacity of a power conversion device increases, the capacity of the switching element used must also be increased according to the main capacity. As the capacity of the switching element increases, the package of the switching element also becomes larger. This makes it difficult to directly connect the board and switching element by soldering or the like. Therefore, the board and switching element are connected via wires.

An abnormality such as a break in the electric wire may occur. In that case, the power conversion device needs to detect the abnormality.

Patent document 1 does not take into consideration such connection abnormalities.

The object of the present invention is to provide a power conversion device capable of detecting an abnormality in the connection with a switching element.

The present invention provides a power conversion device having a plurality of switching elements, a drive unit that drives gates of the switching elements, and a control unit that outputs a control signal to the drive unit,
The drive unit is
The power conversion device includes a gate resistor connected to the switching element, and a voltage monitoring unit that detects an abnormality in connection with the switching element based on a potential difference of the gate resistor.

According to the present invention, it is possible to detect abnormalities in the connection with the switching element.

FIG. 1 is a circuit diagram of a first embodiment. 3 is a timing chart according to the first embodiment. 1 is an overall schematic circuit diagram of a power conversion device according to a first embodiment; 1 is a schematic diagram of an overall structure of a power conversion device according to a first embodiment; FIG. 11 is a circuit diagram of a second embodiment. FIG. 11 is a circuit diagram of a third embodiment. 13 is a timing chart according to the third embodiment. FIG. 13 is a circuit diagram of a fourth embodiment. FIG. 13 is a circuit diagram of a fifth embodiment. 13 is a timing chart of the fifth embodiment. FIG. 13 is a circuit diagram of a sixth embodiment.

First, the configuration of the power conversion device to which this embodiment is applied will be described with reference to Figures 3 and 4. Figure 3 shows an example of the overall circuit configuration of the power conversion device 1 to which the embodiment 1 is applied.

In the power conversion device 1, power from an AC power source 2 is full-wave rectified by a diode 3, smoothed by a capacitor 4, and first converted to DC power. The converted DC power is then converted back to AC power by an inverter in the power conversion device 1. The inverter comprises multiple IGBTs (Insulated Gate Bipolar Transistors) 5. By switching the IGBTs 5 ON or OFF, the DC power is converted into AC power of any frequency and voltage, and the power conversion device 1 outputs the AC power to a load 6.

The control circuit 9 that controls the power conversion device 1, the IGBT gate drive circuit 10 that drives the gate of the IGBT 5, and other circuits are composed of a microcomputer with a CPU and memory, ICs, semiconductors such as transistors, resistors, capacitors, etc. These circuits are mounted on the substrate 8.

Figure 4 is a diagram showing an example of the overall structure of a power conversion device to which this embodiment is applied. Power semiconductors such as diodes and IGBTs are often provided in the form of modules sealed in packages. Figure 4 shows an example in which an IGBT5 is configured as a module sealed in a package.

A gate terminal to which a gate signal is applied is arranged on the IGBT5. In order to cool the heat generated by the power semiconductors, multiple diodes 3 and multiple IGBTs 5 are arranged on a cooling fin 21. Each power semiconductor such as the diodes and IGBTs 5 are wired to the capacitor 4 using wiring material 22 such as an electric wire or a copper bar. The multiple diodes 3 or multiple IGBTs 5 are connected by main circuit wiring material 23 such as an electric wire or a copper bar. The terminal of the substrate 8 on which the control circuit 9 and IGBT gate drive circuit 10 are mounted is connected to the gate terminal of the IGBT5 by IGBT gate wiring 24 such as an electric wire or a copper bar.

An operation panel 7 is connected to the control circuit 9. The operation panel 7 inputs operation information for the power conversion device from outside and outputs information regarding the status of the power conversion device.

Below, an embodiment of the present invention is explained in detail with reference to the drawings.

Figure 1 is a diagram showing an IGBT gate drive circuit 10, a control circuit 9, and an IGBT5 in the first embodiment. In Figure 1, the IGBT gate drive circuit 10 and the control circuit 9 are mounted on a substrate 8. The IGBT gate drive circuit 10 includes a gate signal amplifier 31, a gate resistor 32, and a voltage monitor 33. An IGBT gate wiring 24 is provided between the substrate 8 and the IGBT5, transmitting a signal that controls the gate of the IGBT5. The circuit in Figure 1 shows one phase of the IGBT gate drive circuit 10 and IGBT5 shown in Figure 3, which have a total of six phases.

The gate source signal from the control circuit 9, an ON signal or OFF signal, is amplified by the gate signal amplifier 31 into a signal suitable for driving the IGBT gate. The amplified gate control signal is supplied to the gate terminal of the IGBT via gate resistor 32. The voltage monitor 33 monitors the voltage generated in the gate resistor 32, and monitors whether a voltage pulse is generated immediately after outputting an ON signal to the IGBT gate. If a pulse is generated, it is determined to be normal, and if not, it is determined to be abnormal, and a normal or abnormal signal is sent to the upper control circuit 9.

Next, the operation of the circuit of Example 1 will be described. Figure 2 shows a timing chart of the circuit of Figure 1. In Figure 2, the horizontal axis indicates time, and the vertical axis indicates the voltage at each point in Figure 1.

From the top to the bottom of Figure 2, there are shown a gate source signal 41 that turns the gate of the IGBT on or off and is output from the control circuit 9, a gate signal 42 which is the output voltage of the gate signal amplifier 31 which amplifies the gate source signal 41, a voltage (gate voltage) 43 between the gate and emitter of the IGBT, a voltage 44 generated across both ends of the gate resistor 32, and an output voltage (open circuit signal) 45 of the voltage monitor 33.

At time t1, the gate signal 42 of the gate signal amplifier 31 rises due to an ON signal from the control circuit 9. Here, since the IGBT gate is capacitive, charging occurs to the IGBT gate through the gate resistor 32. Therefore, a voltage is generated in the gate resistor 32 during the charging period of the IGBT gate.

When the IGBT is turned OFF, the current is discharged from the IGBT gate through gate resistor 32. This causes a voltage to be generated in the reverse direction. Each time an ON or OFF signal is sent to the IGBT gate, a potential difference is repeatedly generated across the gate resistor.

At time t2, assume that the IGBT gate wiring 24 between the substrate 8 and the IGBT 5 breaks at the break point 34 in Figure 1. In that case, no charge or discharge current flows to the IGBT gate when the IGBT is turned ON or OFF. As a result, no voltage is generated across the gate resistor.

The voltage monitor 33 monitors the voltage across the gate resistors immediately after the IGBT is turned on, and if a voltage pulse above a specified value is generated, it does not output signal 45 (outputs an OFF signal). On the other hand, if the voltage across the gate resistors does not exceed the specified value, the voltage monitor 33 outputs an ON open circuit signal 45. In this way, if there is no abnormality such as a open circuit, the voltage monitor 33 assumes that it is normal and does not output signal 45. If an abnormality such as a open circuit occurs, the voltage monitor 33 outputs an abnormality signal 45, making it possible to detect the abnormality.

When the control circuit 9 receives an ON signal 45 from the voltage monitor 33, it determines that the IGBT gate wiring 24 between the substrate 8 and the IGBT 5 has been broken, and controls the power conversion device to stop. In that case, the control circuit 9 may control a display unit such as the operation panel 7 to notify an external device that a break has occurred so that a user or administrator can understand that a break has occurred.

According to this embodiment, if an abnormality occurs in the connection of the wiring between the substrate 8 and the IGBT 5, the abnormality can be detected and the operation of the power conversion device can be stopped.

Figure 5 is a diagram showing a circuit of the second embodiment. Explanation of points common to the first embodiment will be omitted. This embodiment is an embodiment in which two IGBTs are used in parallel. The reason for using two IGBTs in parallel is that there are cases where it is desired to increase the capacity of the current flowing through the IGBTs.

Between the gate signal amplifier 31 and the parallel IGBTs, there is provided a gate resistor 32 connected to the gate of each IGBT. A voltage monitor 33 similar to that in the first embodiment is provided for each gate resistor 32. The output from the voltage monitor 33 is connected to an OR circuit 51, and if any of the voltage monitors 33 detects an abnormality, a detection signal is transmitted to the control circuit 9.

In this embodiment, two IGBTs are connected in parallel, but the number of parallel connections can be three or more. In this case, a voltage monitor is provided on the gate resistor of each IGBT, and an OR is taken for all outputs.

When the control circuit 9 receives a signal from the OR circuit 51 indicating that one of the IGBT gate wirings 24 connecting the two IGBTs connected in parallel to the substrate 8 has been broken, it controls the power conversion device to stop.

When using two IGBTs in parallel, even if the IGBT gate signal wiring of one of the IGBTs becomes defective and one of the IGBTs cannot turn on, the IGBT with the healthy wiring can turn on normally and pass current. In other words, when using two IGBTs in parallel, the situation where one IGBT cannot turn on does not become apparent. As a result, the output as a power conversion device is normal and the abnormality may not become apparent.

Even under such circumstances, in this embodiment, a wiring fault in the IGBT gate is detected and the control circuit 9 stops the operation of the power conversion device, thereby preventing a secondary failure.

Figure 6 is a diagram showing a circuit of the third embodiment. This embodiment is an embodiment that embodies the voltage monitor 33 in the first embodiment. In this embodiment, the voltage monitor 33 in Figure 3 is composed of a voltage comparator 61, an edge detector 62, a latch circuit 63, and an XOR circuit 64. Explanations of points common to the first and second embodiments will be omitted.

The voltage comparator 61 compares the voltage 44 at the gate resistor 32 with a reference voltage 74. When the voltage 44 at the gate resistor 32 is higher than the reference voltage 74, the voltage comparator 61 outputs an ON signal 71 to the latch circuit 63.

The reference voltage 74 is preset in the voltage comparator 61. This reference voltage 74 is set to a level lower than the pulse voltage of the voltage 44 of the gate resistor 32 under normal conditions, and is set to a level at which the voltage comparator 61 does not output a signal due to noise, detection errors, etc., except when the IGBT is turned on.

The signal from the voltage comparator 61 is sent to the input of the latch circuit 63. When an ON signal 71 is received, the latch circuit 63 holds the output signal 73 in the ON state, and when a reset signal 72 is received, the latch circuit 63 is reset and the output signal 73 turns OFF.

The edge detector 62 detects the falling edge of the gate signal 42, which is the output of the gate signal amplifier 31, and outputs a falling edge signal 72. The latch circuit 63 inputs the falling edge signal (reset signal) 72 from the edge detector 62. The output signal 73 of the latch circuit 63 and the gate signal 42 of the gate drive circuit are input to the XOR circuit 64. The XOR circuit 64 takes the XOR (exclusive OR) of the output signal 73 of the latch circuit 63 and the gate signal 42, which is the output of the gate drive circuit.

When the gate signal 42 is an ON signal and the output signal 73 of the latch circuit 63 is an ON signal, the output 45 of the XOR circuit 64 is an OFF signal as a normal state. When the gate signal 42 is an ON signal and the output signal 73 of the latch circuit 63 is an OFF signal, the output 45 of the XOR circuit 64 is an ON signal as a wiring abnormality.

The control circuit 9 receives the output signal 45, and in the case of an abnormal signal, detects that a wiring fault has occurred in the IGBT gate, and the control circuit 9 controls the power conversion device to stop operation.

Figure 7 shows a timing chart of the circuit in Figure 6. In Figure 7, the horizontal axis shows time, and the vertical axis shows the voltage at each point in Figure 6.

From the top to the bottom of Figure 7, there are shown a gate source signal 41 that turns the gate of the IGBT on or off and is output from the control circuit 9, a gate signal 42 which is the output voltage of the gate signal amplifier 31 which amplifies the gate source signal 41, a gate voltage 43 between the gate and emitter of the IGBT, a voltage 44 which is the potential difference across the gate resistor 32, a signal 71 from the voltage comparator 61, a falling signal 72 of the gate signal 42, an output signal 73 from the latch circuit 63, and an output voltage 45 of the XOR circuit 64.

According to this embodiment, similar to the first embodiment, when an abnormality occurs in the connection of the wiring between the substrate 8 and the IGBT 5, the abnormality can be detected. Then, the operation of the power conversion device can be stopped. In addition, the reference voltage 74 for determining whether or not an abnormality has occurred can be set arbitrarily according to the state of the circuit.

Figure 8 is a diagram showing a circuit of the fourth embodiment. Explanation of points common to the above-mentioned embodiments will be omitted. In this embodiment, a circuit that embodies the voltage monitor 33 in the third embodiment is provided for each gate resistor of the IGBT. In FIG. 8, since two IGBTs 5 are connected in parallel, two voltage monitors 33 are connected corresponding to the IGBTs 5. As in the third embodiment, the voltage monitor 33 has a voltage comparator 61, an edge detector 62, a latch circuit 63, and an XOR circuit 64. In FIG. 8, the outputs of the two XOR circuits 64 are connected to an OR circuit 81. The OR circuit 81 outputs the logical sum of the outputs of the two XOR circuits 64 to the control circuit 9. In the case where any of the parallel-connected IGBTs 5 has an abnormality due to a wiring defect, the control circuit 9 can detect the occurrence of a wiring abnormality by receiving an ON signal.

According to this embodiment, as in the second embodiment, the control circuit 9 can receive a signal from the OR circuit 81 indicating that one of the IGBT gate wirings 24 connecting the two IGBTs connected in parallel to the substrate 8 has been broken. This allows the power conversion device to be controlled to stop, thereby preventing secondary failures.

Figure 9 is a diagram showing a circuit of Example 5. Explanation of points common to the above-mentioned examples will be omitted. This example is an example in which a single voltage monitor 93 is provided for each phase when IGBTs are used in parallel. This example differs from the above-mentioned examples in that two resistors 921, 922 are provided, which are connected to the gate resistor 91 and connected to each IGBT. The common gate resistor 91 is provided with a voltage monitor 93 that monitors the voltage generated at the gate resistor 91.

The operation of the circuit of this embodiment will now be described. Figure 10 shows a timing chart of this embodiment. As in the first embodiment, at time t1, when the output voltage of the gate signal amplifier rises due to an ON signal from the control circuit, a potential difference occurs across the gate resistor 91, the first resistor 921, and the second resistor 922.

In this embodiment, the gate resistor 91 and the first resistor 921, and the gate resistor 91 and the second resistor 922 are connected in series. Therefore, the voltage generated in the gate resistor 91 is the resistance voltage division ratio. If the IGBT gate wiring 24 is disconnected at the disconnection point 34 at time t2, the resistance voltage division ratio changes and the generated voltage changes.

The resistance value of the gate resistor 91 is R91, and the resistance values of the first resistor 921 and the second resistor 922 are R92. In this case, the voltage division ratio before and after the IGBT gate wiring 24 is disconnected changes from R91/(R91+R92/2) to R91/(R91+R92).

The gate voltage when the IGBT turns ON is VH. In that case, the voltage generated across gate resistor 91 before time t2 is VH × R91/(R91 + R92/2). After time t2, voltage 101 generated across gate resistor 91 becomes VH × R91/(R91 + R92), and voltage 101 generated across gate resistor 91 is smaller than before the break.

The reference voltage 102 for voltage detection judgment by the voltage monitor 93 is set to a level where the IGBT turns on when the voltage 101 generated by the gate resistor 91 is VH×R91/(R91+R92/2) and the IGBT does not turn on when the voltage 101 is VH×R91/(R91+R92). The voltage monitor 93 detects whether the potential difference generated at turn-on exceeds the reference voltage 102.

If the potential difference generated when IGBT5 is turned on exceeds the reference voltage 102, the voltage monitor 93 outputs a normal OFF signal 45 to the control circuit 9.

If the potential difference across the gate resistor 91 generated when the IGBT 5 is turned on falls below the reference voltage 102, or if no potential difference pulse is generated across the gate resistor 91, the voltage monitor 93 outputs an abnormal ON signal 45 to the control circuit 9.

According to this embodiment, when IGBT5 are used in parallel, one voltage monitor 93 per phase is configured, and it is possible to judge wiring failure of the IGBT gate. In addition, secondary failures can be prevented in advance.

Figure 11 is a diagram showing the circuit of the fifth embodiment. Explanation of points common to the above-mentioned embodiments will be omitted. In this embodiment, in the circuit configuration of Figure 9 of the fifth embodiment, the specific circuit of the voltage monitor 93 is the same as that of the voltage monitor 33 of the third embodiment.

11 shows the voltage monitor 93 in FIG. 9, which is composed of a voltage comparator 61, an edge detector 62, a latch circuit 63, and an XOR circuit 64. In this embodiment, the reference voltage of the voltage comparator 61 is the reference voltage 102, as in the fifth embodiment. In this embodiment, the detection voltage of the voltage comparator is different from that in the third embodiment, but the other operations are the same as those in the third embodiment.

According to this embodiment, when IGBT5 is used in parallel, it is not necessary to provide two voltage monitors for each gate resistor of the IGBT, as compared to the second and fourth embodiments. According to this embodiment, there is only one gate resistor 91 of the IGBT, and one voltage monitor connected to one gate resistor 91 is sufficient. And, according to this embodiment, it is possible to determine wiring defects to the gate of the IGBT. In addition, secondary failures can be prevented in advance.

Furthermore, according to the first to sixth embodiments, damage to components such as IGBTs of the power conversion device can be prevented and wasteful power consumption can be reduced. This allows for effective use of resources such as components and eliminates waste, which contributes to the realization of a society that does not adversely affect the global environment through environmental conservation.

In the above embodiment, IGBTs were used as an example, but they may be replaced with other switching elements such as MOSFETs.

1...power conversion device, 2...AC power supply, 3...diode, 4...capacitor, 5...IGBT, 6...load, 7...operation panel, 8...circuit board, 9...control circuit, 10...IGBT gate drive circuit, 21...cooling fin, 22...wiring material, 23...main circuit wiring material, 24...IGBT gate wiring, 31...gate signal amplifier, 32...gate resistor, 33...voltage monitor, 34...disconnection location, 41...gate source signal, 42...gate signal, 43...gate voltage, 44...gate resistor voltage, 45...disconnection signal, 51...OR circuit, 61...voltage comparator, 62...edge detector, 63...latch circuit, 64...XOR circuit, 71...output signal of voltage comparator, 72...output signal of edge detector, 73...output signal of latch circuit, 921...first resistor, 922...second resistor, 102...reference voltage of voltage monitor

Claims (10)

A plurality of switching elements;
A driving unit that drives a gate of the switching element;
A power conversion device having a control unit that outputs a control signal to the drive unit,
The drive unit is
A gate resistor connected to the switching element;
A power conversion device having a voltage monitoring unit that monitors the potential difference of the gate resistor, and determines that there is an abnormality in the connection with the switching element if no voltage pulse is generated immediately after outputting an ON signal to the switching element . 2. The power conversion device according to claim 1,
The voltage monitoring unit
The power conversion device compares the potential difference with a specified value, and outputs a different signal to the control unit depending on whether or not there is a break in the line between the switching element and the drive unit. 2. The power conversion device according to claim 1,
The switching elements are connected in two in parallel,
The power conversion device, wherein the gate resistor and the voltage monitoring unit are disposed for each of the switching elements. 2. The power conversion device according to claim 1,
The voltage monitoring unit
comparing the potential difference with a specified value;
The power conversion device outputs a different signal to the control unit depending on the presence or absence of a break in the line between the switching element and the drive unit, based on the signal resulting from the comparison and a signal for controlling a gate. The power conversion device according to claim 4,
The switching elements are connected in two in parallel,
A power conversion device in which the gate resistor and the voltage monitoring unit are arranged for each of the switching elements. 2. The power conversion device according to claim 1,
The switching element includes a first switching element and a second switching element,
a first resistor is disposed between the first switching element and the gate resistor;
A power conversion device, comprising: a second resistor disposed between a second switching element and the gate resistor. 7. The power conversion device according to claim 6,
The voltage monitoring unit
comparing the potential difference with a specified value;
Based on the comparison result signal and the signal that controls the gate,
A power conversion device that outputs a different signal to the control unit depending on whether or not there is a break in a line between the switching element and the drive unit. 2. The power conversion device according to claim 1,
The power conversion device, wherein the switching element is an IGBT. 2. The power conversion device according to claim 1,
an inverter having a plurality of the switching elements;
A power conversion device having the drive unit and the control unit. 10. The power converter according to claim 9,
The switching element is enclosed in a package,
The power conversion device, in which the switching element and the drive unit are connected via wiring.

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