JP2021145406A - Power converter - Google Patents

Abstract

To detect short-circuit failure in a secondary coil of a transformer with a simple configuration.SOLUTION: A power converter includes: an inductive load 21 having a primary coil 21a and a secondary coil 21b and configured such that magnetic flux generated by energization of the primary coil 21a interlinks with the secondary coil 21b; a switching element 26 arranged between the primary coil 21a and the ground; voltage measuring means 10 for measuring a voltage Vds of a connection line 6b connecting between the primary coil 21a and the switching element 26; and control means 10 for controlling energization of the primary coil 21a by turning on/off the switching element 26. The control means 10 obtains change in the voltage Vds of the connection line 6b accompanied by turning-off of the switching element 26, and when the change in the voltage Vds of the connection line 6b is larger than a predetermined threshold value, it is determined that the secondary coil 21b is abnormal.SELECTED DRAWING: Figure 3

Description

The present invention relates to a power converter.

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

Japanese Unexamined Patent Publication No. 2013-255304

However, when the switching element is on-driven, it is considered that the primary side current flows to the ground via the switching element and does not flow into the secondary coil. Further, it is considered that the induced current does not flow in the secondary coil due to the rectifying action of the diode on the secondary side when the switching element is driven on. Therefore, even if a short circuit occurs in the secondary coil, the voltage of the intermediate node when the switching element is on-driven hardly changes as compared with the normal state, so that the measured voltage of the intermediate node when the switching element is on-driven Then, it is difficult to detect a short circuit of the secondary coil.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a power conversion device capable of detecting a short-circuit failure in a secondary coil of a transformer with a simple configuration.

Therefore, the power conversion device according to the present invention has an inductive load having a primary coil and a secondary coil, and a magnetic flux generated by energization of the primary coil is configured to interlink with the secondary coil. A switching element arranged between the primary coil and the ground, a voltage measuring means for measuring the voltage of the connection line connecting the primary coil and the switching element, and a primary coil by turning the switching element on and off. A control means for controlling energization is provided, and 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 larger than a predetermined threshold value, the secondary coil is abnormal. Is determined to be.

According to the power conversion device according to the present invention, a short-circuit failure in the secondary coil of the transformer can be detected with a simple configuration.

It is a schematic block diagram which shows an example of the damper system for a vehicle. It is the schematic cross-sectional view which shows the internal structure example of the damping force variable damper in this system. It is a circuit diagram which shows the detailed internal configuration example of the high voltage supply device in this system. It is a time chart which shows a model operation example in a normal state of this apparatus. It is a time chart which shows the typical operation example at the time of abnormality of this apparatus. It is a flowchart which shows an example of the abnormality detection processing in the control circuit of this apparatus. It is a time chart explaining the drain voltage acquisition timing of the detection process. It is a flowchart which shows the modification of the abnormality detection processing. It is a time chart explaining the drain voltage acquisition timing of the same modification.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the attached drawings.

FIG. 1 shows an example of a vehicle damper system to which a power conversion device is applied. In the vehicle damper system, for example, in order to dampen the vibration caused by the road surface unevenness while the four-wheeled vehicle 1 is traveling, one wheel 2 is associated with one damping force variable damper 3, and four damping force variable dampers 3 are provided. To be equipped. The variable damping force damper 3 internally encloses an electrorheological fluid whose viscosity changes depending on the voltage applied to it (maximum several kilovolts) as a working fluid, and controls the applied voltage from the outside to control the level of damping force. It is configured to be adjustable. The variable damping force damper 3 constitutes a suspension device together with a suspension spring (not shown) provided on the corresponding wheel 2.

Further, 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 on the wheels 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 on 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 applied to the damping force variable damper 3 in order to generate the damping force required for the damping force variable damper 3 according to the vehicle height signal output from the vehicle height sensor 4. A high voltage supply device 5 is provided. _{The high voltage supply device 5 is a power conversion device, and converts (boosts) the power supply voltage VBAT} supplied from the vehicle-mounted battery 6 which is a DC power supply into a desired DC voltage, that is, a DC voltage applied to the damping force variable damper 3. Functions as a DC / DC converter that outputs.

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

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

Further, in the damping force variable damper 3, the piston rod 36 is inserted into the inner cylinder 34 via the insertion port 35a of the upper end cap 35. The space between the piston rod 36 and the insertion port 35a is configured to be liquid and airtight. 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 34a that communicates the inside and outside of the inner cylinder 34 is provided in the vicinity of the upper end cap 35 on the side surface of the inner cylinder 34. Further, the valve body 33 is provided with a valve body communication hole 33a that communicates the reservoir chamber α and the lower cylinder chamber γ, and the valve body reverse that restricts the flow of the 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 for communicating the upper cylinder chamber β and the lower cylinder chamber γ, and a piston check valve that limits the flow of working fluid from the upper cylinder chamber β to the lower cylinder chamber γ. A valve 37b is provided.

Further, in the damping force variable damper 3, a cylindrical electrode cylinder 38, which is a conductor, is inside 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 separated from the inner cylinder 34 and the outer cylinder 31. The electrode cylinder 38 is electrically connected to the high voltage supply device 5. In the electrode cylinder 38, the gap between the inner cylinder 34 and the electrode cylinder 38 is closed at the upper end and the lower end of the electrode cylinder 38 by the annular isolator 39 which is an electrically insulating material, and the outer cylinder 31 and the inner cylinder 38 are closed. It is electrically isolated from surrounding components such as the cylinder 34.

A voltage application flow path δ for applying a voltage to the flowing working fluid is formed between the electrode cylinder 38 and the inner cylinder 34, and the isolator 39 at the lower end of the electrode cylinder 38 has a voltage application flow path δ. An isolator communication hole 39a that communicates with the reservoir chamber α is provided.

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

When the piston rod 36 extends, the working fluid in the upper cylinder chamber β is pressurized by raising the piston 37 in the inner cylinder 34, and the working fluid in the upper cylinder chamber β passes through the inner cylinder communication hole 34a and the voltage application flow path δ. Inflow into. At this time, an amount of working fluid corresponding to the working fluid flowing into the voltage application flow path δ due to the rise 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, so that the working fluid in the lower cylinder chamber γ flows into the upper cylinder chamber β through the piston communication hole 37a. At this time, the working fluid pushed away by the volume increase of the piston rod 36 occupied 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.

The working fluid flowing into the voltage application flow path δ moves toward the isolator communication hole 39a in the voltage application flow path δ regardless of whether the piston rod 36 expands or contracts. Therefore, the working fluid in the voltage application flow path δ is formed between the inner cylinder 34 and the electrode cylinder 38 by applying the DC voltage supplied from the high voltage supply device 5 to the inner cylinder 34 and the electrode cylinder 38. The viscosity is adjusted according to the generated potential difference. As a result, the damping force required for the damping force variable 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 variable damping force damper 3 is shown in the drawing. .. Further, the variable damping force 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 unit 27, and a filter unit 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 shown so that the magnetic flux generated by energization of the primary coil 21a is interlinked with the secondary coil 21b. An inductive load wound around an omitted core. The primary coil 21a is connected to the vehicle-mounted battery 6 and a power supply voltage V _BAT is applied. The secondary coil 21b is connected to the variable damping force damper 3 to supply a boosted DC voltage to the variable damping force damper 3. More specifically, one end of the primary coil 21a is connected to the positive electrode of the vehicle-mounted battery 6 via the positive electrode wire 6a, and the other end of the primary coil 21a is connected to the negative electrode of the vehicle-mounted battery 6 via the negative electrode wire 6b. NS. Further, one end of the secondary coil 21b is connected to the electrode cylinder 38 of the variable damping force 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 variable damping force damper 3. It is connected via 3b. The negative electrode wire 6b and the inner cylinder wire 3b are connected to a ground such as the body ground of the vehicle 1. As shown by the black circles indicating the polarity (start of winding) of each coil in the figure, the primary coil 21a and the secondary coil 21b have opposite polarities to each other, and the input voltage of the primary coil 21a and the secondary coil are secondary. The output voltage of the coil 21b is in opposite phase to each other.

The main diode 22 is arranged on the electrode tubular wire 3a, the anode of the main diode 22 is connected to the secondary coil 21b, 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 a current to flow in one direction from the secondary coil 21b to the damping force variable damper 3 via the electrode tubular wire 3a.

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

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

The switching element 26 is arranged on the ground side of the negative electrode wire 6b with respect to the connection point to which the reflux wire 29 is connected. The control terminal of the switching element 26 is connected to the control circuit 10 via the driver unit 27, and performs a switching operation in which the switching element 26 is switched on and off based on the control signal output from the control circuit 10. When the switching element 26 is in the on state, the primary coil 21a and the ground are electrically conductive, and when the switching element 26 is in the off state, the primary coil 21a and the ground are electrically cut off. Will be done.

In the configuration shown, 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. Is connected to the driver unit 27. The switching element 26 is not limited to the n-channel MOSFET, and may be any semiconductor switch element that performs switching operation by inputting a control signal from the outside to the control terminal. For example, a bipolar transistor or an IGBT (Insulated Gate Bipolar Transistor) And so on.

The control circuit 10 calculates the target damping force as described above, and outputs the control signal generated according to the target damping force to the driver unit 27 to turn on / off the switching element 26 and energize the primary coil 21a. Performs normal processing to control. The driver unit 27 generates a drive signal for actually driving the switching element 26 based on the control signal, and outputs this drive signal to the 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 unit 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, and the PWM signal compares the command signal of the voltage level according to the duty with the carrier signal of a predetermined frequency. Is generated. As a result, the PWM signal becomes a rectangular wavy 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, when the PWM signal is H level, the switching element 26 is driven on, and when the PWM signal is L level, the switching element 26 is driven off. The driver unit 27 generates a gate drive signal for actually driving the switching element 26 based on the PWM signal, and outputs the gate drive signal to the gate terminal of the switching element 26.

Further, the control circuit 10 inputs and measures the voltage of the intermediate node between the primary coil 21a and the switching element 26 of the negative electrode wire 6b through the filter unit 28 that removes the high frequency component, and measures the intermediate. An abnormality detection process for detecting a short-circuit failure of the secondary coil 21b is performed based on the voltage of the node. The control circuit 10 functions as a 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 configuration shown in the figure, the control signal output from the switching element 26 is a PWM signal, the voltage of the intermediate node is defined as a drain voltage V _ds, and the current flowing through the switching element 26 is _{defined as a drain current I d} .

The microcomputer of the control circuit 10 is configured by connecting a processor such as a CPU (Central Processing Unit), a storage means including a volatile memory and a non-volatile memory, an input / output port, and the like so as to be communicable by an internal bus. The control circuit 10 performs the above-mentioned normal processing and abnormality detection processing by the processor reading the control program stored in the non-volatile memory into the volatile memory and executing the control program. However, it does not exclude that a part or all of the normal processing and the abnormality detection processing is performed by the hardware configuration.

Next, with reference to FIG. 4, an operation example of the high voltage supply device 5 in a normal state in which a short circuit failure does not occur in the secondary coil 21b of the high voltage supply device 5 will be described. Figure 4 is a schematic example of the operation of the high voltage supply device 5 at the time of normal, (a) shows the switching operation of the switching element 26, (b) shows a change with time of the drain current I _d, (c ) Indicates the time course of the drain voltage V _ds.

At time t _1, the switching element 26 is turned on the basis of the PWM signal output from the control circuit 10 (see FIG. 4 (a)), accumulation of excitation energy is started primary coil 21a is energized. The current or drain current _{I d} flowing through the primary coil 21a, and gradually increases under the influence of inherent inductance in the primary coil 21a (see Figure 4 (b)). As a result, the change in magnetic flux generated by the primary coil 21a causes an induced electromotive force to be generated in the secondary coil 21b through the core. However, since the secondary coil 21b has the opposite polarity to that of the primary coil 21a, the induced current of 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 during the previous off drive of the switching element 26 flows to the damping force variable damper 3. On the other hand, the drain voltage V _ds is approximately the ground potential (see FIG. 4 (c)).

In time _{t 2, the} when turned off based on the PWM signal switching device 26 is output from the control circuit 10 (see FIG. 4 (a)), the energization of the primary coil 21a is stopped, the drain current _{I d} does not flow ( 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 energizing 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 exciting energy stored 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 exciting energy is released.

Even if the switching element 26 is turned off, the drain voltage V _{ds does not immediately rise to the power supply voltage V BAT} , but gradually rises due to the influence of the counter electromotive force generated in the primary coil 21a (see FIG. 4 (c)). ). At this time, the 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 V _ds rises to a potential higher than the power supply voltage V _BAT (see FIG. 4 (c)). Here, let λ1 be the rate of increase _{of the drain voltage V ds} when the switching element 26 is turned off in the normal state. If all the exciting energy is released by the time the switching element 26 turns on and the induced current of the secondary coil 21b does not flow, the reflected voltage does not superimpose on the primary coil 21a, so that the drain voltage V _ds is the power supply voltage V _BAT. Converges to. The counter electromotive force generated in the primary coil 21a is attenuated by the freewheeling diode 24 and the consumption resistor 25, whereby the drain voltage _Vds is suppressed to be equal to or lower than the withstand voltage of the switching element 26.

At time t _3, the switching element 26 is turned off again on the basis of the PWM signal outputted from the control circuit 10, operation up to time t ₁ ~t ₃ of the high-voltage supply device 5 are repeated.

Next, with reference to FIG. 5, an operation example of the high voltage supply device 5 at the time of an abnormality in which a short circuit failure occurs in the secondary coil 21b of the high voltage supply device 5 will be described. Figure 5 is a schematic example of the operation of the high voltage supply device 5 for abnormality, (a) shows the switching operation of the switching element 26, (b) shows a change with time of the drain current I _d, (c ) Indicates the time course of the drain voltage V _ds.

When the _{switching element 26 is driven on at times t 11 to t 12} (see FIG. 5 (a)), no induced current flows through the secondary coil 21b as described above, so that the secondary coil 21b passes through the primary coil 21a. The reflected voltage from is not superimposed. Therefore, the drain voltage V _ds and the drain current I _d show the same time-dependent changes as the normal times t _{1 to t 2} (see FIGS. 5 (b) and 5 (c)).

At time _{t 12,} 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 is stopped, the drain current _{I d} does not flow ( See FIG. 5 (b)). At this time, since the inductance of the secondary coil 21b is reduced due to a short-circuit failure, an induced current larger than that in the normal state suddenly flows through the secondary coil 21b, and as a result, the reflected voltage superimposed on the primary coil 21a also increases. Increase. Therefore, the drain voltage V _ds also rises sharply and larger than in the normal state according to the reflected voltage from the secondary coil 21b (see FIG. 5C). _{Here, assuming that the rate of increase of the drain voltage V ds} when the switching element 26 is turned off at the time of abnormality is λ2, the rate of increase λ2 at the time of abnormality is larger than the rate of increase λ1 at the time of normal.

When the induced current due to the short-circuit failure of the secondary coil 21b is excessive, the drain voltage _Vds causes ringing that violently vibrates as shown by mutual induction between the primary coil 21a and the secondary coil 21b. Raise (see FIG. 5 (c)). Then, when all the exciting energy is released by the time the switching element 26 is turned on and the induced current of the secondary coil 21b does not flow, the reflected voltage is not superimposed on the primary coil 21a, so that the drain voltage _Vds is the power supply voltage. Converges to V _BAT. The counter electromotive force generated in the primary coil 21a is attenuated by passing through the freewheeling diode 24 and the consumption resistor 25, which is the same as in the normal state.

At time _{t 13,} the switching element 26 is turned off again on the basis of the PWM signal outputted from the control circuit 10, operation up to time _t 11 _{~t 13} of the high voltage supply device 5 are repeated.

_{As described above, since 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 time and the normal time, whether or not a short-circuit failure has occurred in the secondary coil 21b based on this change. Can be determined.

FIG. 6 shows an example of an abnormality detection process that the control circuit 10 repeatedly performs 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. The abnormality detection process shall be performed in parallel with the normal process.

In step S1 (abbreviated as "S1" in the figure; the same applies hereinafter), the control circuit 10 detects the turn-off of the switching element 26. 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 the turn-off of the switching element 26 when it detects that the gate drive signal output from the driver unit 27 has changed to a potential state (for example, L level) indicating the turn-off of the switching element 26. .. Then, when the control circuit 10 detects the turn-off of the switching element 26 (YES), the process proceeds to step S2, while when the turn-off of the switching element 26 is not detected (NO), steps S2 to S2. S4 is omitted, and step S1 is executed again.

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

However, at least one of the control cycle ΔT and the PWM signal cycle (or frequency) is the measurement of the _{two drain voltages V ds while the drain voltage V ds} is rising (before falling) due to the turn-off of the switching element 26. It is assumed that the value can be obtained. _{The measured values of the two drain voltages Vds} stored in a storage means such as a register may be erased by the next control cycle ΔT.

In step S3, the control circuit 10 determines whether or not the rate of change σ1 of _{the drain voltage V ds is larger than a predetermined threshold value.} Then, when the control circuit 10 _{determines that the rate of change σ1 of the drain voltage V ds} is larger than a predetermined threshold value (YES), the control circuit 10 determines that a short-circuit failure has occurred in the secondary coil 21b, and performs processing. Proceed to step S4. On the other hand, the control circuit 10, when a change rate σ1 of the drain voltage V _ds is equal to or less than the predetermined threshold value is determined not to short-circuit fault occurs in (NO), 2 coil 21b, step S4 Is omitted, and step S1 is executed again. If the measurement interval S is constant, it may be determined whether or not a short-circuit failure has occurred in the secondary coil 21b by comparing the change amount ΔVd of _{the drain voltage V ds with another threshold value.}

In step S4, the control circuit 10 performs an abnormality processing. The control circuit 10 is a power relay capable of stopping the output of the PWM signal and interrupting the continuity between the vehicle-mounted battery 6 and the primary coil 21a on the positive electrode line 6a as an abnormality processing when giving priority to suppressing the occurrence of a secondary failure. If is arranged, shut off the power relay, or at least one of them. Alternatively, the control circuit 10 reduces the duty (ratio of on-time) of the PWM signal to a predetermined value or less as an abnormality processing when giving priority to the continuation of the operation of the damping force variable damper 3. Regardless of which abnormality processing is performed, the control circuit 10 has a short-circuit failure of the secondary coil 21b to another electronic control device of the vehicle 1 via a communication network such as CAN (Controller Area Network). May be notified.

FIG. 8 shows a modified example of the abnormality detection process that the control circuit 10 repeatedly performs 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. The description of the processing content similar to 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 V ds} input and measured through the filter unit 28 and stores it in a storage means such as a register. The measured value of the drain voltage V _ds is stored so that the time series can be recognized, for example, it is associated with the order of storage or the order of control cycles.

In step S12, when the control circuit 10 detects the turn-off of the switching element 26 (YES) in the same manner as in step S1, the process proceeds to step S13. On the other hand, the control circuit 10, and if not detected turn-off of the switching element 26 erases the measurement value of the drain voltage _{V ds} stored at (NO), the immediately preceding step S11, omitting the step S13~S16 And 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 unit 28 and stores it in a storage means such as a register.

In step S14, the control circuit 10 calculates the rate of change σ2 of the _{drain voltage V ds} based on the measured values of the _{two drain voltages V ds, as in step S2.} Specifically, as shown in FIG. 9, the two drain voltages V _ds are acquired before and after _{the time t n when the turn-off of the switching element 26 is detected.} That is, two drain voltage _{V ds} is the time _t measured value _{Vds n-1} (previous value) of the previous time _{t n-1} to the first drain voltage _{V ds} acquired in step S11 in _n the time _{t n} subsequent It is the measured value Vds _{n + 1} (current value) of the _{second drain voltage V ds} acquired in step S13 at the time t _{n + 1 of.} The drain rate of change σ2 voltage _{V ds} is the time t measured value of _n-1 first drain voltage _{V ds} obtained by the _{Vds n-1, the} time _{t n + 1} is acquired in the second drain voltage V It is calculated by dividing the measured value of _{ds Vds n + 1} 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 acquired before and after _{the time t n when} the turn-off of the switching element 26 is detected, so that _{the measured value of the second drain voltage V ds} is obtained by the turn-off of the switching element 26. _This is to make it easier to acquire while ds is rising (before falling).

In step S15, similarly to step S3, when the control circuit 10 _{determines that the rate of change σ2 of the drain voltage V ds} is larger than a predetermined threshold value (YES), a short-circuit failure occurs in the secondary coil 21b. It is determined that there is, the process proceeds to step S16, and the abnormal case process is performed in the same manner as in step S4. On the other hand, the control circuit 10, when a change rate σ2 of the drain voltage V _ds is equal to or less than the predetermined threshold value is determined not to short-circuit fault occurs in (NO), 2 coil 21b, Step S16 Is omitted, and step S1 is executed again.

According to such a high voltage supply device 5, the drain voltage V due to the turn-off is noticed that there is a clear difference in the change of _{the drain voltage V ds} due to the turn-off of the switching element 26 between the abnormal time and the normal state. _{Based on} the change in ds (rate of change or amount of change), it is determined whether or not a short-circuit failure has occurred in the secondary coil 21b. Therefore, according to the high voltage supply device 5, even when compared with the configuration in which the overcurrent is detected from the comparison result between the _{drain voltage Vds when the switching element 26 is driven on and the predetermined threshold value, the configuration is secondary with a simple configuration.} It has a remarkable effect of being able to detect a short-circuit failure of the coil 21b.

In the abnormality detection process of the above embodiment (see FIGS. 6 and 7), while the drain voltage V _ds is increasing (before decreasing) due to _{the turn-off of the switching element 26, the two drain voltages V ds} are It is possible that the measured value cannot be obtained in time. In this case, assuming that the change _{in the drain voltage V ds} accompanying the turn-off of the switching element 26 is constant in each cycle of the PWM signal, the PWM cycle in which the measured value Vds _{n + 1 of the first drain voltage V ds} is acquired. another of the second after turn-off of the switching element 26 in the PWM period of the drain voltage _{V ds} measured value _{Vds n + 2} may be acquired later. 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 t _{n + 1} when the measured value Vds _{n + 1 of the first drain voltage V ds is acquired.} The measured value of the second drain voltage V _{ds may be acquired at the time specified.}

In the abnormality detection process of the above embodiment and its modified example (hereinafter referred to as "the embodiment or the like"), the _{rate of change σ1 and σ2 of the drain voltage V ds} was compared with a predetermined threshold value, but the secondary coil 21b A plurality of threshold values having different sizes may be provided in order to determine the failure level of the short circuit failure. For example, when two thresholds, large and small, are set, it can be determined as follows. When the rate of change σ1 and σ2 of the drain voltage V _ds is equal to or less than the smaller threshold value, it is determined that a short-circuit failure has not occurred in the secondary coil 21b. When the rate of change σ1 and σ2 of the drain voltage V _ds exceeds the smaller threshold value but is equal to or less than the larger threshold value, it is determined that a minor short-circuit failure has occurred in the secondary coil 21b. When the rate of change σ1 and σ2 of the drain voltage V _ds exceeds the larger threshold value, it is determined that a severe short-circuit failure has occurred in the secondary coil 21b.

If the failure level of the short-circuit failure of the secondary coil 21b is determined in this way, the content of the abnormality processing can be selected according to the failure level. For example, in the case of a minor short-circuit failure, the duty (ratio of on-time) of the PWM signal is reduced to a predetermined value or less, and the operation of the damping force variable damper 3 is continued. On the other hand, in the case of a severe short-circuit failure, at least one of the PWM signal output stop and the power relay cutoff is performed to suppress the occurrence of the secondary failure.

Although the invention made for the present inventor has been specifically described above based on the above-described embodiments, the present invention is not limited to the above-described embodiments and the like, and various changes can be made without departing from the gist thereof. It goes without saying that it is possible. Further, the technical matters described independently of each other in the above-described embodiments and the like can be appropriately combined as long as there is no technical contradiction.

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 current discontinuous mode or the current continuous mode. Here, the current discontinuous 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 being driven off. Further, the current continuous mode is a mode in which the switching element 26 is turned on before the induced current of the secondary coil 21b is stopped during the off driving of the switching element 26.

In the high voltage supply device 5, one damping force variable damper 3 corresponds to one booster circuit 20 and includes four booster circuits 20, but the number of booster circuits 20 is not limited to four. For example, in the high voltage supply device 5, two front wheel variable damping force dampers 3 correspond to one booster circuit 20, and two rear wheel variable damping force dampers 3 correspond to one booster circuit 20. One booster circuit 20 may be provided. Alternatively, the high voltage supply device 5 may include one booster circuit 20 in which four variable damping force dampers 3 on all wheels correspond to one booster circuit 20.

The abnormal processing is not limited to the one 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 and S12), or when the _{rate of change σ1 and σ2 of the drain voltage V ds} is equal to or less than a predetermined threshold value (steps S3 and 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 its use is not limited as long as it utilizes the function as a DC / DC converter using the transformer 21. No. Therefore, the power conversion device may be applied to the primary coil 21a after converting the AC power into DC power by a diode bridge or the like in a system provided with an AC power supply. Further, the power conversion device is not limited to the one that boosts the voltage, but may be one that steps down the voltage.

5 ... High voltage supply device, 6 ... In-vehicle battery, 6b ... Negative wire, 10 ... Control circuit, 20 ... Boost 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 and configured such that the magnetic flux generated by energization of the primary coil interlinks with the secondary coil.
A switching element arranged between the primary coil and the ground,
A voltage measuring means for measuring the voltage of the connection line connecting the primary coil and the switching element, and
A control means for turning the switching element on and off to control energization of the primary coil, and
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 the voltage of the connection line is larger than a predetermined threshold value. Power converter. The power conversion device according to claim 1, wherein the change in the voltage of the connection line is calculated from the voltage of the connection line before the turn-off and the voltage of the connection line after the turn-off. The power conversion device according to claim 1, wherein the change in the voltage of the connection line is calculated from the voltage of the connection line after the turn-off.

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