JP7269193B2 - power converter - Google Patents

Description

The present invention relates to power converters.

As a power conversion device, when a switching element is turned on in a DC/DC converter using a transformer, overcurrent is detected from the result of comparison between the measured voltage at the intermediate node between the primary coil of the transformer and the switching element and a predetermined threshold. Detectors are known (see, for example, the embodiment of Patent Document 1).

JP 2013-255304 A

However, when the switching element is on-driven, the primary side current is considered to flow to the ground via the switching element and not flow into the secondary coil. Further, it is considered that the rectifying action of the diode on the secondary side prevents the induced current from flowing through the secondary coil when the switching element is turned on. Therefore, even if a short circuit occurs in the secondary coil, the voltage at the intermediate node when the switching element is turned on does not change much compared to the normal time, so the measured voltage at the intermediate node when the switching element is turned on Therefore, it is difficult to detect the short circuit of the secondary coil.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power conversion apparatus capable of detecting a short-circuit fault in a secondary coil of a transformer with a simple configuration.

For this reason, the power conversion device according to the present invention has a primary coil and a secondary coil, and an inductive load configured such that magnetic flux generated by energization of the primary coil interlinks with the secondary coil; a switching element disposed between the primary coil and the ground; a voltage measuring means for measuring the voltage of a connection line connecting the primary coil and the switching element; a control means for controlling energization, wherein the control means obtains a change in the voltage of the connection line due to the turn-off of the switching element, and when the change in the voltage of the connection line is greater than a predetermined threshold, the secondary coil is abnormal. It is determined that

According to the power conversion device of the present invention, it is possible to detect a short-circuit failure in the secondary coil of the transformer with a simple configuration.

1 is a schematic configuration diagram showing an example of a vehicle damper system; FIG. It is a schematic sectional drawing which shows the internal structural example of the damping force variable damper in the same system. It is a circuit diagram showing a detailed internal configuration example of a high voltage supply device in the same system. 4 is a time chart showing a sample operation example of the same device in a normal state; It is a time chart which shows the example of a schematic operation|movement at the time of abnormality of the same apparatus. It is a flowchart which shows an example of the abnormality detection process in the control circuit of the apparatus. 5 is a time chart for explaining drain voltage acquisition timing in the same detection process; It is a flowchart which shows the modification of the same abnormality detection process. It is a time chart explaining the drain voltage acquisition timing of the same modification.

Embodiments for carrying out the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an example of a vehicle damper system to which a power converter is applied. The damper system for a vehicle has four variable damping force dampers 3, one damping force variable damper 3 corresponding to one wheel 2, in order to attenuate vibrations caused by unevenness of the road surface while a four-wheeled vehicle 1 is running, for example. Prepare. The variable damping force damper 3 contains an electrorheological fluid whose viscosity changes depending on the voltage applied to it (up to several kilovolts) as a working fluid. configured to be adjustable. The damping force variable damper 3 constitutes a suspension device together with a suspension spring (not shown) provided on the corresponding wheel 2 .

In addition, the vehicle damper system includes a vehicle height sensor 4 in the suspension device for each wheel 2 in order to measure the vehicle height at the wheel 2 as vehicle body behavior information of the vehicle 1 . The vehicle height sensor 4 outputs a vehicle height signal including information on the height of the vehicle body from the road surface at the wheels 2, such as the amount of vertical displacement between the suspension arm and the vehicle body.

Then, the vehicle damper system supplies a voltage to be applied to the variable damping force damper 3 in order to generate the necessary damping force in the variable damping force damper 3 according to the vehicle height signal output from the vehicle height sensor 4. A high voltage supply 5 is provided. The high-voltage supply device 5 is a power conversion device that converts (boosts) the power supply voltage V _BAT supplied from the on-vehicle battery 6, which is a DC power supply, to a desired DC voltage, that is, a DC voltage to be applied to the damping force variable damper 3. It functions as a DC/DC converter that outputs

Specifically, the high voltage supply device 5 includes a control circuit 10 containing a microcomputer, and a booster circuit 20 provided for each of the four variable damping force dampers 3 . Based on the vehicle height signal from the vehicle height sensor 4, the control circuit 10 calculates the damping force (target damping force) required in the damping force variable damper 3 of the suspension system provided with the vehicle height sensor 4, A control signal corresponding to the target damping force is output to the booster circuit 20 corresponding to the damping force variable damper 3 . The booster circuit 20 boosts the power supply voltage V _BAT supplied from the vehicle-mounted battery 6 to a desired DC voltage based on the control signal output from the control circuit 10 , and outputs the DC voltage to the damping force variable damper 3 .

FIG. 2 schematically shows an example of the damping force variable damper 3. As shown in FIG. In the damping force variable damper 3, a cylindrical outer cylinder 31 forming the outer shell has a bottomed cylindrical body in which the lower end opening is closed with a lower end cap 32, and a lower end opening is closed with a valve body 33. A cylindrical inner cylinder 34 is housed coaxially with the outer cylinder 31 . Upper end openings of the outer cylinder 31 and the inner cylinder 34 are closed by an upper end cap 35 . A reservoir chamber α is formed between the outer cylinder 31 and the inner cylinder 34 (more precisely, an electrode cylinder described later). The inner cylinder 34 is electrically connected to the high voltage supply device 5 .

In the variable damping force damper 3 , the piston rod 36 is inserted into the inner cylinder 34 through the insertion opening 35 a of the upper end cap 35 . The space between the piston rod 36 and the insertion port 35a is configured to be liquid-tight and air-tight. The tip of the piston rod 36 is provided with a piston 37 that repeatedly moves up and down while sliding on the inner peripheral surface of the inner cylinder 34 . The internal space of the inner cylinder 34 is defined by the piston 37 into an upper cylinder chamber β on the upper end cap 35 side and a lower cylinder chamber γ on the valve body 33 side.

An inner cylinder communication hole 34 a is provided in the vicinity of the upper end cap 35 on the side surface of the inner cylinder 34 to communicate the inside and the outside of the inner cylinder 34 . Further, the valve body 33 is provided with a valve body communication hole 33a for communicating between the reservoir chamber α and the lower cylinder chamber γ, and a valve body communication hole 33a for restricting the flow of working fluid from the lower cylinder chamber γ to the reservoir chamber α. A stop valve 33b is provided. Further, the piston 37 is provided with a piston communication hole 37a that communicates between the upper cylinder chamber β and the lower cylinder chamber γ, and a piston check valve that restricts the flow of working fluid from the upper cylinder chamber β to the lower cylinder chamber γ. A valve 37b is provided.

In the damping force variable damper 3, a cylindrical electrode cylinder 38, which is a conductor, is provided between the inner cylinder 34 and the outer cylinder 31 and between the upper end cap 35 and the valve body 33. It is arranged coaxially with the cylinder 34 and the outer cylinder 31 and spaced apart from the inner cylinder 34 and the outer cylinder 31 . The electrode tube 38 is electrically connected to the high voltage supply device 5 . In the electrode tube 38, an annular isolator 39 made of an electrically insulating material closes the gap between the inner tube 34 and the electrode tube 38 at the upper end and the lower end of the electrode tube 38, and also separates the outer tube 31 from the inner tube 38. It is electrically isolated from surrounding components such as tube 34 .

Between the electrode tube 38 and the inner tube 34, a voltage application flow path δ is formed to apply a voltage to the working fluid flowing therethrough. An isolator communication hole 39a communicating with the reservoir chamber α is provided.

The damping force variable damper 3 is attached to the vehicle 1 by attaching the lower end of the outer cylinder 31 to each wheel 2 (axle) and attaching the upper end of the piston rod 36 to the vehicle body.

When the piston rod 36 extends, the piston 37 in the inner cylinder 34 rises to pressurize the working fluid in the upper cylinder chamber β, and the working fluid in the upper cylinder chamber β flows through the inner cylinder communication hole 34a into the voltage application flow path δ. flow inside. At this time, an amount of working fluid corresponding to the amount of working fluid that has flowed into the voltage application flow path δ due to the upward movement of the piston 37 flows from the reservoir chamber α into the lower cylinder chamber γ through the valve body communication hole 33a.

When the piston rod 36 contracts, the piston 37 in the inner cylinder 34 descends, causing the working fluid in the lower cylinder chamber γ to flow into the upper cylinder chamber β through the piston communication hole 37a. At this time, the working fluid displaced by the increased volume of the piston rod 36 in the inner cylinder 34 flows from the upper cylinder chamber β into the voltage application flow path δ through the inner cylinder communication hole 34a.

Both when the piston rod 36 extends and when it contracts, the working fluid that has flowed into the voltage application channel δ moves through the voltage application channel δ toward the isolator communication hole 39a. Therefore, when the DC voltage supplied from the high voltage supply device 5 is applied to the inner cylinder 34 and the electrode cylinder 38 , the working fluid in the voltage application flow path δ flows between the inner cylinder 34 and the electrode cylinder 38 . It becomes a viscosity according to the generated potential difference. As a result, the damping force necessary for the variable damping force damper 3 is generated.

FIG. 3 shows a detailed internal configuration example of the high voltage supply device 5 . As described above, the high voltage supply device 5 includes four booster circuits 20, but for convenience of explanation, only one booster circuit 20 corresponding to one damping force variable damper 3 is shown in the drawing. . Also, the damping force variable damper 3 is represented by an equivalent circuit in which a capacitor 3C and a resistor 3R are connected in parallel.

The booster circuit 20 includes a transformer 21 , a main diode 22 , an output capacitor 23 , a freewheeling diode 24 , a consumption resistor 25 , a switching element 26 , a driver section 27 and a filter section 28 .

The transformer 21 has a primary coil 21a and a secondary coil 21b, and the primary coil 21a and the secondary coil 21b are arranged so that magnetic flux generated by energization of the primary coil 21a interlinks with the secondary coil 21b. Inductive load wound on the omitted core. The primary coil 21a is connected to the vehicle-mounted battery 6 and applied with the power supply voltage _VBAT . The secondary coil 21b is connected to the damping force variable damper 3 to supply the damping force variable damper 3 with a boosted DC voltage. More specifically, one end of the primary coil 21a is connected to the positive electrode of the vehicle battery 6 via a positive wire 6a, and the other end of the primary coil 21a is connected to the negative electrode of the vehicle battery 6 via a negative electrode wire 6b. be. One end of the secondary coil 21b is connected to the electrode cylinder 38 of the damping force variable damper 3 via the electrode cylinder wire 3a, and the other end of the secondary coil 21b is connected to the inner cylinder 34 of the damping force variable damper 3 by the inner cylinder wire. 3b. The negative wire 6b and the inner cylindrical wire 3b are connected to a ground such as the body ground of the vehicle 1. As shown in FIG. In the figure, as indicated by a black dot indicating the polarity (start of winding) of each coil, the polarities of the primary coil 21a and the secondary coil 21b are opposite to each other. The output voltage of the coil 21b is opposite in phase to each other.

The main diode 22 is arranged on the electrode tube 3 a , the anode of the main diode 22 is connected to the secondary coil 21 b , and the cathode of the main diode 22 is connected to the damping force variable damper 3 . As a result, the main diode 22 functions as a rectifying element that allows current to flow in one direction from the secondary coil 21b to the damping force variable damper 3 via the electrode tube 3a.

The output capacitor 23 is arranged in parallel with the secondary coil 21b between the electrode tube 3a and the inner tube 3b. Specifically, one end of the output capacitor 23 is connected between the cathode of the main diode 22 and the damping force variable damper 3 in the electrode tube 3a, and the other end of the output capacitor 23 is connected to the inner tube 3b. .

The return diode 24 and the consumption resistor 25 are arranged in series in a return line 29 that connects the positive line 6a and the negative line 6b while bypassing the primary coil 21a. Specifically, the freewheeling diode 24 is arranged with the direction from the negative electrode line 6b to the positive electrode line 6a as the forward direction.

The switching element 26 is arranged closer to the ground than the connection point of the negative electrode line 6b to which the return line 29 is connected. The switching element 26 has a control terminal connected to the control circuit 10 via the driver section 27 and performs a switching operation in which ON/OFF is switched based on a control signal output from the control circuit 10 . When the switching element 26 is on, the primary coil 21a is electrically connected to the ground, and when the switching element 26 is off, the primary coil 21a is electrically cut off from the ground. be done.

In the illustrated configuration, an n-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is used as the switching element 26, the drain terminal is connected to the other end of the primary coil 21a, the source terminal is connected to the ground, and the gate terminal are connected to the driver unit 27 . The switching element 26 is not limited to an n-channel MOSFET, and may be a semiconductor switching element that performs switching operation by inputting a control signal from the outside to a control terminal, such as a bipolar transistor or an IGBT (Insulated Gate Bipolar Transistor). etc.

The control circuit 10 calculates the target damping force as described above, and outputs a control signal generated according to the target damping force to the driver unit 27 to turn the switching element 26 on and off to energize the primary coil 21a. perform normal processing to control Driver section 27 generates a drive signal for actually driving switching element 26 based on the control signal, and outputs this drive signal to switching element 26 .

In the illustrated configuration, the control circuit 10 generates a PWM signal that causes the switching element 26 to perform a switching operation by pulse width modulation (PWM) control, and outputs this PWM signal to the driver section 27 . The ratio (duty) of the ON time or OFF time during the switching operation of the switching element 26 is set according to the target damping force. generated by As a result, the PWM signal becomes a rectangular pulse signal having two potential levels, an H level in a high potential state and an L level in a low potential state. For example, the switching element 26 is turned on when the PWM signal is at H level, and the switching element 26 is turned off when the PWM signal is at L level. The driver section 27 generates a gate drive signal for actually driving the switching element 26 based on the PWM signal, and outputs this gate drive signal to the gate terminal of the switching element 26 .

In addition, the control circuit 10 inputs the voltage of the intermediate node between the primary coil 21a and the switching element 26 in the negative electrode line 6b through the filter unit 28 that removes high frequency components, measures the voltage, and measures the measured intermediate node voltage. Abnormality detection processing is performed to detect a short-circuit failure of the secondary coil 21b based on the node voltage. The control circuit 10 functions as voltage measuring means for measuring the voltage of the intermediate node by A/D (Analog to Digital) conversion or the like. Hereinafter, according to the illustrated configuration, the control signal output from the switching element 26 is assumed to be the PWM signal, the voltage of the intermediate node is assumed to be the drain voltage _Vds , and the current flowing through the switching element 26 is assumed to be the drain current _Id .

The microcomputer of the control circuit 10 is configured by communicably connecting a processor such as a CPU (Central Processing Unit), storage means including a volatile memory and a nonvolatile memory, an input/output port, and the like via an internal bus. In the control circuit 10, the processor reads out the control program stored in the non-volatile memory to the volatile memory and executes it, thereby performing the normal processing and the abnormality detection processing. However, it is not excluded that part or all of the normal processing and the abnormality detection processing are performed by the hardware configuration.

Next, with reference to FIG. 4, an example of operation of the high voltage supply device 5 in a normal state when no short-circuit failure occurs in the secondary coil 21b of the high voltage supply device 5 will be described. 4A and 4B are schematic operation examples of the high-voltage supply device 5 during normal operation, in which (a) shows the switching operation of the switching element 26, (b) shows the change over time of the drain current _Id , and (c ) shows the change over time of the drain voltage _Vds .

At time _t1 , when the switching element 26 is turned on based on the PWM signal output from the control circuit 10 (see FIG. 4(a)), the primary coil 21a is energized to start accumulating excitation energy. The current flowing through the primary coil 21a, that is, the drain current _Id gradually rises under the influence of the inductance specific to the primary coil 21a (see FIG. 4(b)). As a result, the magnetic flux change generated by the primary coil 21a generates an induced electromotive force in the secondary coil 21b through the core. However, since the secondary coil 21b has the opposite polarity to the primary coil 21a, the induced current in the secondary coil 21b is blocked by the main diode 22 on the secondary side. Instead, the discharge current of the output capacitor 23 charged when the switching element 26 was previously turned off flows to the damping force variable damper 3 . On the other hand, the drain voltage _Vds is approximately the ground potential (see FIG. 4(c)).

At time _t2 , when the switching element 26 is turned off based on the PWM signal output from the control circuit 10 (see FIG. 4(a)), the energization of the primary coil 21a stops and the drain current _Id stops flowing ( See FIG. 4(b)). Then, an induced electromotive force is generated in the secondary coil 21b in the direction opposite to that when the switching element 26 is turned on so as not to reduce the magnetic flux generated in the core by the energization of the primary coil 21a. Therefore, the induced current of the secondary coil 21b flows to the damping force variable damper 3 through the main diode 22 on the secondary side. At this time, the output capacitor 23 is also charged. As a result, the excitation energy accumulated in the transformer 21 is released to the damping force variable damper 3 . The induced current generated in the secondary coil 21b decreases as the excitation energy is released.

Even if the switching element 26 is turned off, the drain voltage _Vds does not immediately rise to the power supply voltage _VBAT , but gradually rises due to the influence of the back electromotive force generated in the primary coil 21a (see FIG. 4(c)). ). At this time, a voltage (reflected voltage) reflected from the secondary coil 21b through which the induced current flows is superimposed on the primary coil 21a. Therefore, the drain voltage _Vds rises to a potential higher than the power supply voltage _VBAT (see FIG. 4(c)). Here, let λ1 be the rate of increase of the drain voltage _Vds when the switching element 26 is turned off in the normal state. If all the excitation energy is released and the induced current in the secondary coil 21b stops flowing before the switching element 26 is turned on, the reflected voltage will not be superimposed on the primary coil _{21a .} converges to The back electromotive force generated in the primary coil 21a is attenuated by the freewheeling diode 24 and the consumption resistor 25, thereby suppressing the drain voltage _Vds below the withstand voltage of the switching element 26. FIG.

At time t ₃ , the switching element 26 is turned off again based on the PWM signal output from the control circuit 10, and the operation of the high voltage supply device 5 from time t ₁ to t ₃ is repeated.

Next, with reference to FIG. 5, an operation example of the high voltage supply device 5 in an abnormal state in which the secondary coil 21b of the high voltage supply device 5 is short-circuited will be described. FIG. 5 is a schematic operation _example of the high-voltage supply device 5 in the event of an abnormality. ) shows the change over time of the drain voltage _Vds .

When the switching element 26 is turned on during times t ₁₁ to t ₁₂ (see FIG. 5(a)), no induced current flows through the secondary coil 21b as described above. reflected voltages from are not superimposed. Therefore, the drain voltage V _ds and the drain current I _d exhibit temporal changes similar to those at times t ₁ to t ₂ in the normal state (see FIGS. 5(b) and 5(c)).

At time _t12 , when the switching element 26 is turned off based on the PWM signal output from the control circuit 10 (see FIG. 5(a)), the energization of the primary coil 21a stops and the drain current _Id stops flowing ( See FIG. 5(b)). At this time, since the inductance of the secondary coil 21b is reduced due to the short-circuit fault, an induced current larger than that in the normal case flows through the secondary coil 21b abruptly. Increase. Therefore, the drain voltage _Vds also rises more sharply than in the normal state according to the reflected voltage from the secondary coil 21b (see FIG. 5(c)). Let λ2 be the rate of increase of the drain voltage _Vds when the switching element 26 is turned off in an abnormal state.

When the induced current due to the short-circuit failure of the secondary coil 21b is excessive, the drain voltage _Vds exhibits ringing that vibrates violently as shown in the figure due to mutual induction between the primary coil 21a and the secondary coil 21b. wake up (see FIG. 5(c)). When all the excitation energy is released and the induced current in the secondary coil 21b stops flowing before the switching element 26 is turned on, the reflected voltage is _no longer superimposed on the primary coil 21a. Converge to V _BAT . It should be noted that the back electromotive force generated in the primary coil 21a is attenuated by passing through the freewheeling diode 24 and the consumption resistor 25, as in the normal state.

At time t ₁₃ , the switching element 26 is turned off again based on the PWM signal output from the control circuit 10, and the operation of the high voltage supply device 5 from time t ₁₁ to t ₁₃ is repeated.

In this way, there is a clear difference in the change in the drain voltage _Vds due to the turn-off of the switching element 26 between the abnormal state and the normal state. It is possible to determine whether

FIG. 6 shows an example of abnormality detection processing that is repeatedly performed by the control circuit 10 every control cycle ΔT when the ignition switch of the vehicle 1 is turned on and the operating voltage is supplied to the control circuit 10 . It is assumed that the abnormality detection process is performed in parallel with the normal process.

In step S1 (abbreviated as “S1” in the drawing, the same applies hereinafter), the control circuit 10 detects that the switching element 26 is turned off. The control circuit 10 can detect the turn-off of the switching element 26 when the PWM signal output by the control circuit 10 changes to a potential state (for example, L level) indicating the turn-off of the switching element 26 . Alternatively, the control circuit 10 detects that the switching element 26 is turned off when it detects that the gate drive signal output from the driver section 27 has changed to a potential state (e.g., L level) indicating that the switching element 26 is turned off. . When the control circuit 10 detects that the switching element 26 is turned off (YES), the process proceeds to step S2. S4 is omitted and step S1 is executed again.

In step S2, the control circuit 10 calculates the change rate σ1 of the drain voltage _Vds based on the two measured values of the drain voltage _Vds . Specifically, as shown in FIG. 7, the measured values of the two drain voltages _Vds are acquired after the time _tn when the turn-off of the switching element 26 is detected and stored in a storage means such as a register. Then, the rate of change σ1 of the drain voltage _Vds is the first measured value Vdsn+1 of the drain voltage _Vds obtained at time tn ₊₁ after time _tn , and the first measured value Vdsn ₊₁ of the drain voltage Vds obtained at time _{tn+ 2 after time tn+1.} It is calculated by dividing the change amount ΔVd (=Vd _n+2 −Vd _n+1 ) between the measured value Vds _n+2 of the second drain voltage V _ds and the measurement interval S (=t _n+2 −t _n+1 ).

However, at least one of the control period _ΔT and the period (or frequency) of the PWM signal is measured during the time when the drain voltage _Vds is increasing (before decreasing) due to the turn-off of the switching element 26. Assume that it is set so that the value can be obtained. Note that the two measured values of the drain voltage _Vds stored in the storage means such as a register may be erased by the next control period ΔT.

At step S3, the control circuit 10 determines whether or not the change rate σ1 of the drain voltage _Vds is greater than a predetermined threshold. When the control circuit 10 determines that the change rate σ1 of the drain voltage _Vds is greater than the predetermined threshold value (YES), it determines that a short-circuit fault has occurred in the secondary coil 21b, and performs the process. Proceed to step S4. On the other hand, when the control circuit 10 determines that the change rate σ1 of the drain voltage _Vds is equal to or less than the predetermined threshold value (NO), it determines that the secondary coil 21b is not short-circuited, and performs step S4. is omitted and step S1 is executed again. If the measurement interval S is constant, it may be determined whether or not the secondary coil 21b is short-circuited by comparing the amount of change ΔVd in the drain voltage _Vds with another threshold value.

At step S4, the control circuit 10 performs an abnormality processing. The control circuit 10 stops the output of the PWM signal and the power supply relay capable of interrupting the conduction between the on-vehicle battery 6 and the primary coil 21a to the positive electrode line 6a as abnormal processing when giving priority to suppressing the occurrence of the secondary failure. is located, cut off the power relay. Alternatively, the control circuit 10 reduces the duty (ratio of ON time) of the PWM signal to a predetermined value or less as abnormal processing when giving priority to continuing the operation of the damping force variable damper 3 . Regardless of which abnormal process is performed, the control circuit 10 communicates with another electronic control unit of the vehicle 1 via a communication network such as a CAN (Controller Area Network) that a short-circuit failure of the secondary coil 21b has occurred. may be notified.

FIG. 8 shows a modification of the abnormality detection process that is repeatedly performed by the control circuit 10 every control period ΔT when the ignition switch of the vehicle 1 is turned on and the operating voltage is supplied to the control circuit 10 . It should be noted that the description of the same processing contents as the abnormality detection processing of FIG. 6 will be omitted or simplified.

In step S11, the control circuit 10 acquires the measured value (previous value) of the drain voltage _Vds input through the filter section 28 and stores it in a storage means such as a register. The measured values of the drain voltage _Vds are stored in such a way that the time series can be recognized, for example, by being associated with the order of storage or the order of control cycles.

At step S12, if the control circuit 10 detects that the switching element 26 is turned off (YES), the process proceeds to step S13 in the same manner as at step S1. On the other hand, if the control circuit 10 does not detect the turn-off of the switching element 26 (NO), the control circuit 10 deletes the measured value of the drain voltage _Vds stored in the previous step S11, and omits steps S13 to S16. Then step S1 is executed again.

In step S13, similarly to step S11, the control circuit 10 acquires the measured value (current value) of the drain voltage _Vds input via the filter section 28 and stores it in a storage means such as a register.

In step S14, the control circuit 10 calculates the change rate σ2 of the drain voltage _Vds based on the two measured values of the drain voltage _Vds , as in step S2. Specifically, the two drain voltages _Vds are obtained before and after the time _tn at which the turn-off of the switching element 26 is detected, as shown in FIG. That is, the two drain voltages V _ds are the measured value Vds _n−1 (previous value) of the first drain voltage V _ds acquired in step _S11 at time t _n−1 before time t _n and and the second measured value Vds _n+1 (current value) of the drain voltage V _ds obtained in step S13 at time t _n+1 of . Then, the change rate σ2 of the drain voltage V _ds is the first measured value Vds _n−1 of the drain voltage V _ds obtained at time t _n −1 and the second drain voltage V ds obtained at time t _n+1. It is calculated by dividing the measured value Vds _n+1 of _ds and the amount of change ΔVd (=Vd _n+1 −Vd _n−1 ) by the measurement interval S (=t _n+1 −t _n−1 ).

In step S14, the two drain voltages V _ds are obtained before _and after the time tn when the turn-off of the switching element 26 is detected, because the second measured value of the drain voltage V _ds is This is to facilitate acquisition while _ds is rising (before it falls).

In step S15, similarly to step S3, if the control circuit 10 determines that the rate of change σ2 of the drain voltage _Vds is greater than the predetermined threshold value (YES), a short-circuit fault has occurred in the secondary coil 21b. Then, the process proceeds to step S16, and the abnormality processing is performed in the same manner as in step S4. On the other hand, when the control circuit 10 determines that the rate of change σ2 of the drain voltage _Vds is equal to or less than the predetermined threshold value (NO), it determines that the secondary coil 21b is not short-circuited, and proceeds to step S16. is omitted and step S1 is executed again.

According to such a high voltage supply device 5, noting that there is a clear difference in the change in the drain voltage _Vds accompanying the turn-off of the switching element 26 between abnormal and normal conditions, the drain voltage V Based on the change (rate of change or amount of change) of _ds , it is determined whether or not a short circuit has occurred in the secondary coil 21b. Therefore, according to the high-voltage supply device 5, compared to the configuration in which the overcurrent is detected from the comparison result between the drain voltage _Vds and the predetermined threshold value when the switching element 26 is turned on, the configuration is simple and the secondary current is detected. A remarkable effect is obtained in that a short-circuit failure of the coil 21b can be detected.

In the abnormality detection process (see FIGS. 6 and 7) of the above embodiment, while the drain voltage _Vds is increasing (before decreasing) due to the turn-off of the switching element 26, the two drain voltages _Vds It is conceivable that the measured value cannot be acquired in terms of time. In this case, assuming that the change in the drain voltage V _ds due to the turn-off of the switching element 26 is constant in each cycle of the PWM signal, the measured value Vds _n+1 of the first drain voltage V _ds is acquired in the PWM cycle A second measurement Vds _n+2 of the drain voltage V _ds may be obtained after the switching element 26 is turned off in another PWM period at a later time. More specifically, the time for n cycles of the PWM signal (n is a positive integer) and the time less than the measurement interval S are added to the time tn ₊₁ at which the first measured value Vds _n+1 of the drain voltage _Vds is obtained. A second measured value of the drain voltage V _ds may be obtained at the same time.

In the abnormality detection process of the above embodiment and its modifications (hereinafter referred to as "embodiment etc."), the rate of change σ1, σ2 of the drain voltage _Vds is compared with a predetermined threshold value. A plurality of thresholds with different magnitudes may be provided to determine the fault level of the short circuit fault. For example, when two large and small thresholds are provided, determination can be made as follows. When the rates of change σ1 and σ2 of the drain voltage _Vds are equal to or less than the smaller threshold value, it is determined that the secondary coil 21b is not short-circuited. When the rates of change σ1 and σ2 of the drain voltage _Vds exceed the smaller threshold but are equal to or less than the larger threshold, it is determined that a minor short-circuit failure has occurred in the secondary coil 21b. When the rates of change σ1 and σ2 of the drain voltage _Vds exceed the larger threshold, it is determined that a serious short-circuit failure has occurred in the secondary coil 21b.

By judging the failure level of the short-circuit failure of the secondary coil 21b in this way, it is possible to select the content of the abnormal processing according to the failure level. For example, in the case of a minor short-circuit failure, the duty (on-time ratio) of the PWM signal is reduced to a predetermined value or less to continue the operation of the damping force variable damper 3 . On the other hand, if the short-circuit failure is serious, at least one of stopping the output of the PWM signal and shutting off the power relay is performed to suppress the occurrence of secondary failures.

The present invention has been specifically described above based on the above embodiments, etc., but the present invention is not limited to the above embodiments, etc., and various modifications can be made without departing from the scope of the invention. It goes without saying that this is possible. Also, the technical matters described independently in the above embodiments and the like can be appropriately combined as long as they are not technically inconsistent.

In the high-voltage supply device 5, in the normal processing performed by the control circuit 10, the frequency of the PWM signal may correspond to either the discontinuous current mode or the continuous current mode. Here, the discontinuous current mode is a mode in which the switching element 26 is turned on after the induced current of the secondary coil 21b is stopped while the switching element 26 is driven off. The continuous current mode is a mode in which the switching element 26 is turned on before the induced current of the secondary coil 21b stops while the switching element 26 is driven off.

The high-voltage supply device 5 includes four booster circuits 20, with one variable damping force damper 3 corresponding to one booster circuit 20, but the number of booster circuits 20 is not limited to four. For example, in the high voltage supply device 5, the two variable damping force dampers 3 for the front wheels correspond to one booster circuit 20, and the two variable damping force dampers 3 for the rear wheels correspond to one booster circuit 20. It is also possible to provide two booster circuits 20 . Alternatively, the high-voltage supply device 5 may include one booster circuit 20 corresponding to one booster circuit 20 for four variable damping force dampers 3 of all wheels.

The abnormal processing is not limited to being performed in parallel with the normal processing, and may be performed in series with the normal processing. For example, when the turn-off of the switching element 26 is not detected (steps S1, S12), or when the rate of change σ1, σ2 of the drain voltage _Vds is equal to or less than a predetermined threshold (steps S3, S15), Normal processing may be performed.

The power conversion device can be applied as the high voltage supply device 5 in the vehicle damper system as described above, but if it utilizes the function as a DC/DC converter using the transformer 21, its use does not matter. do not have. Therefore, in a system having an AC power supply, the power converter may convert AC power into DC power using a diode bridge or the like, and then apply the DC power to the primary coil 21a. Further, the power conversion device is not limited to one that boosts voltage, and may be one that steps down voltage.

5 High-voltage supply device 6 Vehicle-mounted battery 6b Negative electrode line 10 Control circuit 20 Booster circuit 21 Transformer 21a Primary coil 21a, 21b Secondary coil 26 Switching element V _ds … Drain voltage, V _BAT … Power supply voltage, Vds _n+1 , Vds _n−1 … First drain voltage measurement value, Vds _n+2 , Vds _n+1 … Second drain voltage measurement value*

Claims (3)

an inductive load having a primary coil and a secondary coil, wherein magnetic flux generated by energization of the primary coil interlinks with the secondary coil;
a switching element disposed between the primary coil and ground;
voltage measuring means for measuring the voltage of a connection line connecting between the primary coil and the switching element;
control means for controlling energization of the primary coil by turning on and off the switching element;
with
The control means obtains a change in the voltage of the connection line due to the turn-off of the switching element, and determines that the secondary coil is abnormal when the change in voltage of the connection line is greater than a predetermined threshold. Power converter. 2. The power converter according to claim 1, wherein the change in voltage of said connection line is calculated from the voltage of said connection line before said turn-off and the voltage of said connection line after said turn-off. 2. The power converter according to claim 1, wherein the change in voltage of said connection line is calculated from the voltage of said connection line after said turn-off.

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