JP7196750B2 - power converter - Google Patents

Description

The present invention relates to power converters.

FIG. 8 is a circuit diagram of a conventional power converter described in Patent Document 1. As shown in FIG. The power conversion device shown in FIG. 8 is a bridge inverter that converts the DC power of the battery 3 into AC power to drive the motor 2 . This bridge inverter has three-phase arms A1, A2, A3 in which MOSFETs (F1-F6) are connected in parallel to IGBTs (S1-S6), respectively.

FIG. 9 is an operation explanatory diagram of the conventional power converter described in Patent Document 1. FIG. According to FIG. 9, the IGBT has the characteristic that the ON voltage is almost constant regardless of the current, whereas the MOSFET has the characteristic that the ON voltage is proportional to the current. Focusing on this point, the technique of Patent Document 1 is based on the current value It at which the ON voltage of the MOSFETs (F1 to F6) and the ON voltage of the IGBTs (S1 to S6) are balanced, and the MOSFETs (F1 to F6) are controlled. It switches whether to operate or to operate the IGBTs (S1 to S6). As described above, the technique of Patent Document 1 aims to improve the operating efficiency regardless of the magnitude of the current by switching the switch circuit to be operated depending on whether the detected current is equal to or less than the reference current value It. .

Japanese Patent Application Laid-Open No. 2002-078104

However, due to circuit errors and hysteresis settings, the switch circuit to be operated may be switched with a current value that deviates from the reference current value It. In such a case, even if the switching current is the same, the IGBT and the MOSFET have different on-state voltages, so the output voltage of the power converter may fluctuate.

Accordingly, the present disclosure provides a power conversion device capable of suppressing variations in output voltage when switching a switch circuit.

This disclosure is
a first switch circuit and a second switch circuit connected in parallel and having different characteristics with respect to current;
a current detection unit that detects current values of currents flowing through the first switch circuit and the second switch circuit;
a comparison unit that compares the current value detected by the current detection unit with a current threshold;
By adding a correction value for correcting the difference between the ON voltages of the first switch circuit and the second switch circuit at the current threshold to the reference voltage command for making the output voltage of the power converter constant, a command correction unit that calculates a correction voltage command;
When the comparison unit detects that the current value detected by the current detection unit crosses the current threshold, one of the first switch circuit and the second switch circuit that is stopped is switched. A power converter is provided, comprising: a command unit that operates a switch circuit according to the correction voltage command and stops the other switch circuit in operation.

According to the technology of the present disclosure, it is possible to provide a power conversion device capable of suppressing variations in output voltage when switching a switch circuit.

It is a circuit diagram which illustrates the structure of a power converter device. 3 is a control block diagram illustrating the configuration of a control circuit; FIG. FIG. 5 is a characteristic diagram illustrating the relationship between the current of the switching element of the first switch circuit and the ON voltage; FIG. 10 is a characteristic diagram illustrating the relationship between the current of the switching element of the second switch circuit and the ON voltage; FIG. 3 is a characteristic comparison diagram illustrating the relationship between the current of the switching element and the ON voltage; FIG. 5 is a characteristic comparison diagram illustrating the relationship between current and loss of a switching element; 5 is a time chart illustrating an operation when switching to the first switch circuit without correction; 7 is a time chart illustrating an operation when switching is performed with correction in the first switch circuit; 5 is a time chart illustrating an operation when switching to the second switch circuit without correction; FIG. 10 is a time chart illustrating an operation when switching is performed with correction in the second switch circuit; FIG. 1 is a conventional circuit diagram; FIG. FIG. 10 is an operation explanatory diagram of a conventional circuit;

Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings.

FIG. 1 is a diagram illustrating a configuration example of a power converter according to one embodiment. In FIG. 1, the power converter 1 is an insulated DC-DC converter having a primary side connected to a DC power supply 100 and a secondary side connected to an output load 200 . The power conversion device 1 converts direct current (DC) input from a DC power supply 100 into direct current (DC) output to an output load 200 .

The power converter 1 is connected in parallel to capacitors 16 and 17 connected in series, a first switch circuit 11 connected in parallel to the series circuit of the capacitors 16 and 17, and the first switch circuit 11. A second switch circuit 21 is provided on the primary side.

A series circuit of capacitors 16 and 17 receives input power from a DC power supply 100 at both ends thereof, and a DC voltage is applied thereto. In the first switch circuit 11, a first switching element 11a to which a first diode 11c is connected in parallel and a second switching element 11b to which a second diode 11d is connected in parallel are connected in series. circuit. In the second switch circuit 21, a third switching element 21a to which a third diode 21c is connected in parallel and a fourth switching element 21b to which a fourth diode 21d is connected in parallel are connected in series. circuit.

FIG. 1 illustrates a mode in which SiC-MOSFETs are used for the switching elements 11a and 11b, and SiC Schottky barrier diodes are used for the diodes 11c and 11d. On the other hand, a mode is illustrated in which Si-IGBTs are used for the switching elements 21a and 21b, and Si diodes are used for the diodes 21c and 21d. By applying a wide bandgap device such as SiC (silicon carbide) or GaN (gallium nitride) to the switching element, the loss of the switching element is reduced. MOSFET is an abbreviation for Metal Oxide Semiconductor Field Effect Transistor, and IGBT is an abbreviation for Insulated Gate Bipolar Transistor.

A mutual connection point (midpoint) between the first switching element 11a and the second switching element 11b and a mutual connection point (midpoint) between the third switching element 21a and the fourth switching element 21b are insulated. It is connected to one end of the primary winding of the transformer 19 . On the other hand, the mutual connection point (midpoint) between the capacitors 16 and 17 is connected to the other end of the primary winding of the isolation transformer 19 .

The power conversion device 1 includes an alternating current detector 22 such as a CT (Current Transformer) and temperature detectors 24 and 25 such as a thermistor. The alternating current detector 22 measures the current flowing through the first switch circuit 11 and the second switch circuit 21 and outputs a current measurement value corresponding to the measured current value to the control circuit 30 . In the form shown in FIG. 1, alternating current detector 22 measures the current flowing between switch circuits 11 and 21 and isolation transformer 19 . The first temperature detector 24 measures the temperature of the first switch circuit 11 and outputs a temperature measurement value corresponding to the measured temperature to the control circuit 30 . The second temperature detector 25 measures the temperature of the second switch circuit 21 and outputs a temperature measurement value corresponding to the measured temperature to the control circuit 30 .

The power converter 1 includes a rectifier circuit including rectifier diodes 12 to 15, a smoothing reactor 20 connected in series to the positive side of the rectifier circuit, and a smoothing capacitor 18 connected in parallel to the rectifier circuit via the smoothing reactor 20. and on the secondary side. The midpoint of the rectifier diodes 12 and 14 connected in series is connected to one end of the secondary winding of the isolation transformer 19 , and the midpoint of the rectifier diodes 13 and 15 connected in series is connected to the secondary winding of the isolation transformer 19 . It is connected to the other end of the secondary winding. One end of a smoothing reactor 20 is connected to the cathode sides of the rectifier diodes 12 and 13 . One end of a smoothing capacitor 18 is connected to the other end (output side end) of the smoothing reactor 20 , and the other end of the smoothing capacitor 18 is connected to anode sides of the rectifying diodes 14 and 15 .

The power conversion device 1 includes a DC voltage detector 23 that detects the output voltage of the power conversion device 1 . DC voltage detector 23 measures the output voltage of power converter 1 (in other words, the voltage of smoothing capacitor 18 ) and outputs a voltage measurement value corresponding to the measured voltage to control circuit 30 .

The power converter 1 includes a control circuit 30 , a first drive circuit 40 and a second drive circuit 50 . The control circuit 30 controls the output voltage of the power converter 1 to be constant based on the measured values input from the AC current detector 22 and the DC voltage detector 23, respectively. A PWM (Pulse Width Modulation) signal for the switch circuit 21 is calculated. The first drive circuit 40 controls switching of the switching elements 11 a and 11 b in the first switch circuit 11 according to the PWM signal for the first switch circuit 11 calculated by the control circuit 30 . The second drive circuit 50 controls switching of the switching elements 21 a and 21 b in the second switch circuit 21 according to the PWM signal for the second switch circuit 21 calculated by the control circuit 30 .

FIG. 2 is a control block diagram illustrating the configuration of the control circuit 30. As shown in FIG. Next, the configuration of the control circuit 30 shown in FIG. 2 will be described.

The control circuit 30 includes a switch switching calculation unit 300, an absolute value calculation unit 301, low-pass filters 302, 311, 317, a switching control unit 303, comparators 305, 306, 313, 319, an RS type flip-flop 307, and a voltage command calculation. It has a section 308 , switches 310 , 314 , 316 and 320 , adders 312 and 318 and a carrier generator 321 . Each function of the control circuit 30 shown in FIG. 2 is realized by a processor such as a CPU operating according to a program readable and stored in the memory.

A current measurement value ia input from the AC current detector 22 (see FIG. 1) is converted into an absolute value by an absolute value calculator 301, and is subjected to a filtering process to remove a carrier frequency component by a low-pass filter 302. FIG. The current value Ia, which is the result of filtering, is output to the switch switching calculation section 300 . In this manner, the AC current detector 22, the absolute value calculator 301, and the low-pass filter 302 form a current detector that detects the current value Ia of the current that flows through the first switch circuit 11 and the second switch circuit 21. be.

The switching control unit 303 uses the temperature T1 of the first switch circuit 11 detected by the temperature detector 24 and the temperature T2 of the second switch circuit 21 detected by the temperature detector 25 to determine the current threshold value Ith1. , Ith2. The first current threshold Ith1 is a switching threshold for switching the switch circuit to be operated from the second switch circuit 21 to the first switch circuit 11 . The second current threshold Ith2 is a switching threshold for switching the switch circuit to be operated from the first switch circuit 11 to the second switch circuit 21 . Current thresholds Ith1 and Ith2 are output to switch switching calculation section 300 .

Further, the switching control unit 303 uses the temperature T1 of the first switch circuit 11 detected by the temperature detector 24 and the temperature T2 of the second switch circuit 21 detected by the temperature detector 25 to determine the reference temperature. It has a reference correction calculator for calculating the correction values Vr1o and Vr2o. The first reference correction value Vr1o is a value used to correct the voltage difference that occurs in the output voltage of the power converter 1 when switching from the second switch circuit 21 to the first switch circuit 11 . The second reference correction value Vr2o is a value used to correct the voltage difference that occurs in the output voltage of the power conversion device 1 when switching from the first switch circuit 11 to the second switch circuit 21 . The first reference correction value Vr1o is output to the first command generator 330, and the second reference correction value Vr2o is output to the second command generator 340. FIG.

Next, an example of a method of calculating the current thresholds Ith1, Ith2 and the reference correction values Vr1o, Vr2o performed by the switching control section 303 will be described.

FIG. 3A is a characteristic diagram illustrating the relationship between the current of the switching element of the first switch circuit 11 and the ON voltage. FIG. 3B is a characteristic diagram illustrating the relationship between the current of the switching element of the second switch circuit 21 and the ON voltage. The ON voltage of a switching element represents the voltage between the main electrodes in the ON state of the switching element. In the case of a MOSFET, it is the voltage between the drain and the source, and in the case of an IGBT, it is the voltage between the collector and the emitter.

The current-voltage characteristics of the first switch circuit 11 and the second switch circuit 21 (that is, the ON voltage with respect to the current flowing between the main electrodes in the ON state of the switching element) vary depending on the temperature, as shown in FIGS. 3A and 3B. Change. Therefore, the switching control unit 303 uses the temperature T1 of the first switch circuit 11 to correct the current-voltage characteristic (hereinafter also referred to as characteristic C1) of the first switch circuit 11 . Similarly, the switching control unit 303 uses the temperature T2 of the second switch circuit 21 to correct the current-voltage characteristic (hereinafter also referred to as characteristic C2) of the second switch circuit 21 .

For example, the switching control unit 303 selects the characteristic data representing the characteristic C1 corresponding to the detected temperature T1 from the characteristic data representing the characteristic C1 stored in the memory for each temperature. Similarly, the switching control unit 303 selects the characteristic data representing the characteristic C2 corresponding to the detected temperature T2 from the characteristic data representing the characteristic C2 stored in the memory for each temperature.

Next, the switching control unit 303 uses the characteristic data of each of the switch circuits 11 and 21 selected by the temperature correction to intersect the first curve representing the characteristic C1 and the second curve representing the characteristic C2. The crossing current value Ith at the time is derived (see FIG. 4). The switching control unit 303 sets the first current threshold Ith1 to a value lower than the intersection current value Ith, and sets the second current threshold Ith2 to a value higher than the intersection current value Ith. For example, as shown in FIG. 4, when the temperature of the switch circuit is 150° C., the cross current value Ith is 90A. At this time, the first current threshold Ith1 is set to 70 A, which is a value lower than the cross current value Ith, and the second current threshold Ith2 is set to 110 A, which is a value higher than the cross current value Ith. good.

Next, the switching control unit 303 corrects the difference (on voltage difference ΔV1) between the ON voltage of the first switch circuit 11 and the ON voltage of the second switch circuit 21 at the first current threshold Ith1. A reference correction value Vr1o is calculated. Similarly, the switching control unit 303 corrects the difference (on voltage difference ΔV2) between the ON voltage of the first switch circuit 11 and the ON voltage of the second switch circuit 21 at the second current threshold Ith2. A reference correction value Vr2o is calculated. Note that the on-voltage of a switch circuit represents the sum of on-voltages of one or more switching elements included in the switch circuit.

The switch switching calculation section 300 has comparators 305 and 306 and a flip-flop 307 . Comparators 305 and 306 are comparators that compare current value Ia with current thresholds Ith1 and Ith2.

The switch switching calculation unit 300 compares the current value Ia, which is the result of the low-pass filter 302, with the first current threshold value Ith1 in the comparator 306. FIG. When the current value Ia is lower than the first current threshold Ith1, a high level signal is input to the reset terminal of the flip-flop 307 (R=1). As a result, the flip-flop 307 outputs a signal F (Q=0 (low level)) that operates the first switch circuit 11 that is inactive and stops the second switch circuit 21 that is in operation. When signal F is output, switches 310, 314, 316, and 320 switch from contact T to contact F.

On the other hand, the switch switching calculation unit 300 compares the current value Ia, which is the result of the low-pass filter 302, with the second current threshold Ith2 in the comparator 305. FIG. When the current value Ia is higher than the second current threshold Ith2, a high level signal is input to the set terminal of the flip-flop 307 (S=1). As a result, the flip-flop 307 outputs a signal T (Q=1 (high level)) that operates the second switch circuit 21 that is inactive and stops the first switch circuit 11 that is inactive. When the signal T is output, the switches 310, 314, 316, 320 are switched from the contact F to the contact T.

In this manner, the first current threshold Ith1 and the second current threshold Ith2 provide a hysteresis characteristic, making it possible to switch the switch circuit to be operated. As a result, the switch circuit can be stably switched, and the loss and heat generation of the switching element can be suppressed. As a result, for example, it is possible to reduce the weight of the cooling body that cools the power converter and improve the efficiency of the power converter.

Based on the voltage value of the output voltage Vo detected by the DC voltage detector 23, the voltage command calculation unit 308 calculates a reference voltage command Vi for making the voltage value of the output voltage Vo constant.

A first command generation unit 330 for the first switch circuit 11 uses a low-pass filter 317 to calculate a first correction value Vr1 to be added to the reference voltage command Vi based on a first reference correction value Vr1o. command correction unit. The first command corrector calculates the first corrected voltage command Vi1 for the first switch circuit 11 by adding the first correction value Vr1 to the reference voltage command Vi in the adder 318 . A carrier generator 321 outputs a triangular wave carrier with a predetermined carrier frequency. The first correction voltage command Vi1 and the triangular wave carrier are compared in magnitude by the comparator 319, and the comparison result is generated as the first pulse command P1 to be given to the first switch circuit 11. FIG. The first pulse command P1 is output to the first drive circuit 40 as a first PWM signal.

FIG. 6A illustrates a specific operation of switching the switch circuit to be operated from the second switch circuit 21 to the first switch circuit 11 without using the first correction value Vr1 (comparative example). When the current value Ia is greater than the first current threshold Ith1, the first switch circuit 11 is stopped and the second switch circuit 21 is operating. Next, when the current value Ia crosses and falls below the first current threshold Ith1, the first switch circuit 11 operates and the second switch circuit 21 stops. During this switching, the output voltage Vo temporarily fluctuates (rises) due to the on-voltage difference ΔV1 (decrease in on-voltage) at the first current threshold Ith1 (see a11). After that, the reference voltage command Vi from the voltage command calculator 308 changes so that the output voltage Vo becomes constant (see a12 and a13), so the output voltage Vo gradually returns to the original constant value.

FIG. 6B illustrates a specific operation of switching the switch circuit to be operated from the second switch circuit 21 to the first switch circuit 11 using the first correction value Vr1 (example). When the current value Ia is greater than the first current threshold Ith1, the first switch circuit 11 is stopped and the second switch circuit 21 is operating. Next, when the current value Ia crosses and falls below the first current threshold Ith1, the first switch circuit 11 operates and the second switch circuit 21 stops. At the time of switching, the first correction value Vr1 is added to the reference voltage command Vi for the first switch circuit 11 (see a15 and a16), thereby suppressing fluctuations in the output voltage Vo and keeping it substantially constant. (see a14). After that, the first correction value Vr1 added by the adder 318 is switched from the first reference correction value Vr1o to 0 by the switch 316, and gradually becomes 0 by the low-pass filter 317 (see a16). First correction value Vr1 added by adder 318 is compensated by voltage command calculation unit 308 .

Therefore, by previously compensating for the on-voltage difference ΔV1 at the first current threshold Ith1 using the first correction value Vr1, it is possible to suppress fluctuations in the output voltage Vo during switching of the switch circuit.

On the other hand, in FIG. 2, the second command generator 340 for the second switch circuit 21 applies the second correction value Vr2 to be added to the reference voltage command Vi based on the second reference correction value Vr2o to a low-pass filter. 311 has a second command correction unit. The second command correction unit calculates a second correction voltage command Vi2 for the second switch circuit 21 by adding the second correction value Vr2 to the reference voltage command Vi in the adder 312 . The second correction voltage command Vi2 and the triangular wave carrier are compared in magnitude by the comparator 313, and the comparison result is generated as the second pulse command P2 to be given to the second switch circuit 21. FIG. The second pulse command P2 is output to the second drive circuit 50 as a second PWM signal.

FIG. 7A illustrates a specific operation of switching the switch circuit to be operated from the first switch circuit 11 to the second switch circuit 21 without using the second correction value Vr2 (comparative example). When the current value Ia is smaller than the second current threshold Ith2, the first switch circuit 11 operates and the second switch circuit 21 is stopped. Next, when the current value Ia crosses and exceeds the second current threshold Ith2, the first switch circuit 11 is stopped and the second switch circuit 21 is stopped. At the time of this switching, the output voltage Vo temporarily fluctuates (rises) due to the on-voltage difference ΔV2 (decrease in on-voltage) at the second current threshold Ith2 (see a21). After that, the reference voltage command Vi from the voltage command calculator 308 changes so that the output voltage Vo becomes constant (see a22 and a23), so the output voltage Vo gradually returns to the original constant value.

FIG. 7B illustrates a specific operation of switching the switch circuit to be operated from the first switch circuit 11 to the second switch circuit 21 using the second correction value Vr2 (example). When the current value Ia is smaller than the second current threshold Ith2, the first switch circuit 11 operates and the second switch circuit 21 is stopped. Next, when the current value Ia crosses and exceeds the second current threshold Ith2, the first switch circuit 11 stops and the second switch circuit 21 operates. At the time of switching, the second correction value Vr2 is added to the reference voltage command Vi for the second switch circuit 21 (see a25 and a26), so that fluctuations in the output voltage Vo are suppressed and kept substantially constant. (see a24). After that, the second correction value Vr2 added by the adder 312 is switched from the second reference correction value Vr2o to 0 by the switch 310, and gradually becomes 0 by the low-pass filter 311 (see a27). Second correction value Vr2 added by adder 312 is compensated by voltage command calculation unit 308 .

Therefore, by previously compensating for the on-voltage difference ΔV2 at the second current threshold Ith2 using the second correction value Vr2, it is possible to suppress fluctuations in the output voltage Vo during switching of the switch circuit.

Thus, the power conversion device 1 includes a first switch circuit and a second switch circuit which are connected in parallel and have different on-state voltage characteristics with respect to current, and the first switch circuit and the second switch circuit. A current detection unit that detects the current value of the current flowing through the circuit, a comparison unit that compares the current value detected by the current detection unit with a current threshold, and a reference voltage for making the output voltage of the power converter constant. a command correcting unit for calculating a corrected voltage command by adding to the command a correction value for correcting a difference in ON voltage between the first switch circuit and the second switch circuit at the current threshold; When the comparison unit detects that the current value detected by the current detection unit crosses the current threshold, one of the first switch circuit and the second switch circuit that is stopped is switched. and a command unit that causes the circuit to operate according to the correction voltage command and stops the other switch circuit in operation. Therefore, it is possible to suppress fluctuations in the output voltage when the switch circuit to be operated, of the first switch circuit and the second switch circuit, is switched from one switch circuit to the other switch circuit.

In the above description, the switch circuit is switched using the current-on voltage characteristic of the switching circuit, but the switch circuit may be switched using the current-loss characteristic of the switching circuit shown in FIG. In this case, the current-loss characteristics of the first switch circuit 11 and the second switch circuit 21 (that is, the loss generated with respect to the current flowing between the main electrodes when the switching element is on) also change with temperature. Therefore, the switching control unit 303 uses the temperature T1 of the first switch circuit 11 to correct the current-loss characteristic (hereinafter also referred to as characteristic D1) of the first switch circuit 11 . Similarly, the switching control unit 303 uses the temperature T2 of the second switch circuit 21 to correct the current-loss characteristic (hereinafter also referred to as characteristic D2) of the second switch circuit 21 .

For example, the switching control unit 303 selects the characteristic data representing the characteristic D1 corresponding to the detected temperature T1 from the characteristic data representing the characteristic D1 stored in the memory for each temperature. Similarly, the switching control unit 303 selects the characteristic data representing the characteristic D2 corresponding to the detected temperature T2 from the characteristic data representing the characteristic D2 stored in the memory for each temperature.

Next, the switching control unit 303 uses the characteristic data of each of the switch circuits 11 and 21 selected by the temperature correction to intersect the first curve representing the characteristic D1 and the second curve representing the characteristic D2. The crossing current value Ith at the time is derived (see FIG. 5). The switching control unit 303 sets the first current threshold Ith1 to a value lower than the intersection current value Ith, and sets the second current threshold Ith2 to a value higher than the intersection current value Ith.

Next, the switching control unit 303 corrects the difference (on voltage difference ΔL1) between the ON voltage of the first switch circuit 11 and the ON voltage of the second switch circuit 21 at the first current threshold Ith1. A reference correction value Vr1o is calculated. Similarly, the switching control unit 303 corrects the difference (on voltage difference ΔL2) between the ON voltage of the first switch circuit 11 and the ON voltage of the second switch circuit 21 at the second current threshold Ith2. A reference correction value Vr2o is calculated. Note that the loss of the switch circuit represents the sum of losses of one or more switching elements included in the switch circuit. Subsequent control is the same as described above.

Although the power conversion device has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Various modifications and improvements such as combination or replacement with part or all of other embodiments are possible within the scope of the present invention.

For example, the power converter is not limited to a DC-DC converter that converts direct current to direct current. Specific examples include an inverter that converts DC to AC, a boost converter that boosts an input voltage and outputs it, a buck converter that steps down an input voltage and outputs it, and a buck-boost converter that boosts or steps down an input voltage before outputting it. be. Further, the number of switching elements included in each of the first switch circuit and the second switch circuit is not limited to a plurality (two in the case of the DC-DC converter described above), and may be one (for example, for converters such as boost choppers).

Also, the power conversion device may be used in a moving object such as a railroad vehicle or an automobile, or may be used in an electronic device such as a servo.

Further, if the first switch circuit and the second switch circuit have different characteristics with respect to current, the same type of switching elements (for example, the same type of switching elements with different sizes) may be used for both of the switch circuits. good.

Further, in the above-described embodiment, temperature correction is performed to switch the switch circuit, but the switch circuit may be switched without temperature correction.

1 power converter 11 first switch circuits 11a, 11b switching elements 11c, 11d diodes 12, 13, 14, 15 rectifier diodes 16, 17, 18 capacitor 19 isolation transformer 20 smoothing reactor 21 second switch circuits 21a, 21b switching Elements 21c, 21d Diode 22 AC current detector 23 DC voltage detectors 24, 25 Temperature detector 30 Control circuits 40, 50 Drive circuit 100 DC power supply 200 Output load 300 Switch switching calculation unit 301 Absolute value calculation units 302, 311, 317 Low-pass filter 303 Switching control units 305, 306, 313, 319 Comparator 307 Flip-flop 308 Voltage command calculation units 310, 314, 316, 320 Switches 312, 318 Adder 321 Carrier generator 330 First command generation unit 340 Second command generator of

Claims (9)

a first switch circuit and a second switch circuit connected in parallel and having different characteristics with respect to current;
a current detection unit that detects current values of currents flowing through the first switch circuit and the second switch circuit;
a comparison unit that compares the current value detected by the current detection unit with a current threshold;
Adding a correction value for correcting a difference in ON voltage between the first switch circuit and the second switch circuit at the current threshold to a reference voltage command for making the output voltage of the power converter constant. a command correction unit that calculates a correction voltage command by
When the comparison unit detects that the current value detected by the current detection unit crosses the current threshold, one of the first switch circuit and the second switch circuit that is stopped is switched. and a command unit that operates a switch circuit according to the correction voltage command and stops the other switch circuit in operation. a temperature detection unit that detects each temperature of the first switch circuit and the second switch circuit;
2. The power converter according to claim 1, further comprising a correction calculation section that calculates said correction value using each temperature detected by said temperature detection section. a temperature detection unit that detects each temperature of the first switch circuit and the second switch circuit;
The power converter according to claim 1, further comprising a threshold calculator that calculates said current threshold using each temperature detected by said temperature detector. a temperature detection unit that detects each temperature of the first switch circuit and the second switch circuit;
The power conversion apparatus according to claim 1, further comprising a calculation section that calculates said correction value and said current threshold using each temperature detected by said temperature detection section. the current thresholds include a first current threshold and a second current threshold different from the first current threshold;
The command correction unit adds to the reference voltage command a first correction value for correcting a difference in ON voltage between the first switch circuit and the second switch circuit at the first current threshold. calculates a first correction voltage command, and sets a second correction value for correcting a difference in ON voltage between the first switch circuit and the second switch circuit at the second current threshold as the reference Calculate a second correction voltage command by adding to the voltage command,
When the comparison unit detects that the current value detected by the current detection unit crosses the first current threshold, the command unit switches the one switch circuit being stopped to the first switch circuit. operating according to the correction voltage command, stopping the other switch circuit in operation, and detecting that the current value detected by the current detecting unit crosses the second current threshold by the comparing unit; 5. The apparatus according to any one of claims 1 to 4, wherein said one switch circuit in operation is stopped and said other switch circuit in operation is operated according to said second correction voltage command. Power converter. A crossing current value when a first curve representing characteristics of the first switch circuit with respect to current and a second curve representing characteristics of the second switch circuit with respect to current intersect is the first current threshold. and said second current threshold. The power converter according to any one of claims 1 to 6, wherein the current characteristics of the first switch circuit and the current characteristics of the second switch circuit are on-voltage characteristics of the respective circuits. . The power converter according to any one of claims 1 to 6, wherein the current characteristic of said first switch circuit and the current characteristic of said second switch circuit are loss characteristics of each circuit. 9. The power converter according to any one of claims 1 to 8, wherein at least one of said first switch circuit and said second switch circuit has at least one switching element that is a wide bandgap device. .

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