WO2013099060A1

WO2013099060A1 - Inverter device

Info

Publication number: WO2013099060A1
Application number: PCT/JP2012/005825
Authority: WO
Inventors: 松井　敬三
Original assignee: パナソニック株式会社
Priority date: 2011-12-27
Filing date: 2012-09-13
Publication date: 2013-07-04
Also published as: JP2013135553A; JP5857189B2; CN104040866B; CN104040866A

Abstract

This inverter device is equipped with: a switching circuit comprising multiple upper and lower arms; and a control unit for driving the switching circuit by means of a PWM modulation scheme. Switching components that constitute an upper-arm-side switching circuit and switching components that constitute a lower-arm-side switching circuit are composed of switching components of different types. The control unit shifts an average output voltage to the lower voltage side or to the higher voltage side with respect to the intermediate voltage of a source voltage supplied to the switching circuit on the basis of a condition that determines the magnitude relationship between on-resistances of the switching components that constitute the lower-arm-side switching circuit and on-resistances of the switching components that constitute the upper-arm-side switching circuit.

Description

Inverter device

The present invention relates to an inverter device which includes a plurality of switching elements, converts DC power into AC power of a desired frequency, and drives a load such as a motor.

Conventionally, in a so-called inverter device which converts input power from a power supply into AC power of a desired frequency and is used for motor drive, etc., upstream (upper arm side) and downstream (lower arm) according to application direction of power supply voltage A switching circuit having two series circuits of two switching elements on the side) is common. As switching elements, IGBTs (Insulated Gate Bipolar Transistors), which are insulated gate bipolar transistors, and MOSFETs, which are a type of field effect transistors, are widely used.

The IGBT is characterized by low efficiency at low load, but relatively high efficiency at high load, and also high switching speed. On the other hand, MOSFETs are characterized by high efficiency at low load, relatively low efficiency at high load, and high switching speed. Also, in general inverter circuits, most of the switching elements of the upper and lower arms of the switching circuit are constituted by the same element.

On the other hand, in the inverter device shown in Patent Document 1, two switching elements on the upstream side and the downstream side have a series circuit in which at least one switching element is a MOSFET and the other switching element is an IGBT. As a result, the loss of high voltage and high current output due to the voltage across the IGBT becoming constant becomes small, and the high frequency switching due to the fast on / off speed of the MOSFET is possible and low. The efficiency is improved by utilizing the characteristic that the loss at the time of voltage and low current output is small.

Further, in the inverter circuit shown in Patent Document 2, the switching element on the upper arm side of the switching circuit used to drive the DC motor is configured by an IGBT or MOSFET, and the switching element on the lower arm side is a bipolar transistor. It was configured. As described above, an IGBT or MOSFET capable of high-speed switching is used as the three-phase switching element on the upper arm side of the switching circuit, and a bipolar transistor is used as the three-phase switching element on the lower arm side. It is cheaper than using all IGBTs or MOSFETs, and enables finer control of switching and chopping than when using bipolar transistors. Furthermore, noise can be reduced by enabling deletion of electromagnetic noise when driving a direct current motor and control to reduce vibration due to resonance with the peripheral mechanism.

In the case of an inverter device in which the upper and lower arms of such a switching circuit are configured by different types of switching elements, the balance of the load applied to each switching element becomes uneven when driven by a normal switching pattern. For this reason, load may concentrate on one of the switching elements, and the drive range may be limited due to temperature rise.

In addition, since the conditions for increasing the efficiency of each switching element are different depending on the type of switching element, it is difficult to maximize the efficiency in consideration of the characteristics of the switching element when driven by a normal switching pattern. The

JP, 2007-129848, A Japanese Patent Application Laid-Open No. 7-31182

The inverter device of the present invention includes a switching circuit configured of a plurality of upper and lower arms, and a control unit that drives the switching circuit by a PWM modulation method. The switching element forming the upper arm side switching circuit and the switching element forming the lower arm side switching circuit are formed by different types of switching elements. The control unit switches the average output voltage based on a condition that determines the magnitude relationship between the on resistance of the switching element that configures the lower arm side switching circuit and the on resistance of the switching element that configures the upper arm side switching circuit. Shift to the lower voltage side or higher voltage side than the intermediate voltage of the power supply voltage supplied to the

With such a configuration, low-loss, high-speed switching elements are provided, and even under load conditions in which the lower arm switching elements have high efficiency, and even under load conditions in which the upper arm switching elements have high efficiency, An efficient inverter device is realized.

FIG. 1 is a block diagram of an inverter device according to a first embodiment of the present invention. FIG. 2 is a characteristic diagram showing characteristics of switching elements of the inverter device according to the first embodiment of the present invention. FIG. 3 is a timing chart showing an example of timing characteristics of switching in the PWM modulation method of the inverter device according to the first embodiment of the present invention. FIG. 4 is a characteristic diagram of an example showing characteristics of the amount of current flowing through switching elements on the upper arm side and the lower arm side in the inverter device according to the first embodiment of the present invention. FIG. 5 is a timing chart showing another example of the timing characteristic of switching in the PWM modulation method of the inverter device according to the first embodiment of the present invention. FIG. 6 is a characteristic diagram of another example showing the characteristics of the amount of current flowing in the switching elements on the upper arm side and the lower arm side in the inverter device according to the first embodiment of the present invention. FIG. 7 is a characteristic diagram showing switching characteristics of the output voltage with respect to the output current in the control unit of the inverter device according to the first embodiment of the present invention. FIG. 8 is a timing chart showing timing characteristics of switching in the PWM modulation method of the inverter device according to the first embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited by the embodiment.

Embodiment 1
FIG. 1 is a block diagram of an inverter device according to a first embodiment of the present invention. The alternating current power supplied from the alternating current power supply 1 is once converted into a direct current by the rectifier circuit 4 and the smoothing capacitor 5 and supplied to the inverter device 2. The inverter device 2 includes a switching circuit 20, a control unit 21, and

current detection units

28a and 28b. The switching circuit 20 includes an upper arm side switching circuit 20u including switching elements 22 to 24 connected to the high voltage side of the power supply voltage, and switching elements 25 to 27 connected to the low voltage side of the power supply voltage. The lower arm side switching circuit 20d is configured. The switching elements 22 to 24 are connected in series to the switching elements 25 to 27, respectively, to form a three-phase series circuit. The connection point between the switching elements 22-24 on the upper arm side and the switching elements 25-27 on the lower arm side in these series circuits is connected to the motor 3 which is a load. The

current detection units

28a and 28b detect two-phase output current values (current values flowing to the motor 3) in the three-phase series circuit, and the remaining one-phase output current values are detected two-phase output current values. Is obtained by calculation or the like. The control unit 21 further includes a comparison unit 29 that compares the output current value detected by the

current detection units

28 a and 28 b with a predetermined current value. The operation of the comparison unit 29 will be described later.

The control unit 21 controls the switching of the switching elements 22 to 27 so that the inverter device 2 outputs AC power that causes the motor 3 to rotate at a desired number of rotations. As a control method of switching, a general pulse width modulation (PWM modulation) method of controlling an output voltage by a time width of a drive pulse of a switching element is used.

Further, the control unit 21 drives the switching elements 22 to 27 based on the current value detected by the

current detection units

28a and 28b for detecting the current flowing to the motor 3.

As the switching elements 22 to 24 on the upper arm side, semiconductor devices such as IGBTs having high efficiency at high load are used. Reflux diodes 22a to 24a are connected in parallel to the switching elements 22 to 24, respectively. On the other hand, as the lower arm side switching elements 25 to 27, semiconductor devices such as MOSFETs capable of high speed switching and having a high efficiency at low load are used as compared with the upper arm side switching elements 22 to 24.

In addition, since a diode is configured in the device in this MOSFET, it is not necessary to connect freewheeling diodes in parallel. As described above, switching elements having different characteristics are used for the switching elements 22 to 24 on the upper arm side and the switching elements 25 to 27 on the lower arm side, and a drive method adapted to each characteristic is used, whereby the cost is reduced. With the configuration, high efficiency of the inverter device can be realized.

FIG. 2 is a characteristic diagram showing the characteristics of switching elements used in the inverter device according to the first embodiment of the present invention. FIG. 2 shows voltage-current characteristics of an IGBT as a switching element on the upper arm side and a MOSFET as a switching element on the lower arm side.

The characteristic curve of the IGBT shows the relationship between the collector-emitter voltage Vce (sat) (on voltage) and the collector current Ic when the IGBT is on. In the IGBT, as the collector current Ic increases, the increase of the voltage drop which is the collector-emitter voltage Vce decreases, and the slope of this characteristic curve consisting of the reciprocal of the on resistance of the switching element relatively increases. . Therefore, the loss generated in the switching element decreases as the load current (collector current Ic) increases.

On the other hand, the characteristic curve of the MOSFET shows the relationship between the drain current Id and the voltage drop which is the drain-source voltage Vds when the MOSFET is on. In the MOSFET, the relationship between the drain-source voltage Vds and the drain current Id is substantially linear as shown in FIG. Therefore, regardless of the value of the load current (drain current Id), the slope of this characteristic line is substantially constant, so that the on resistance of the switching element is constant regardless of the magnitude of the load current.

Comparing the characteristics of IGBT and MOSFET switching elements, when the load current value is smaller than I1 (the voltage drop is V1), the voltage drop is smaller in the MOSFET than in the IGBT (on resistance is smaller), that is, the switching element It can be seen that the loss caused by

On the contrary, when the load current value is larger than I1, it is understood that the voltage drop amount is smaller in the IGBT than in the MOSFET (the on resistance is smaller), that is, the loss generated in the switching element is smaller.

Therefore, when the load current value is smaller than I1 at which the voltage drop amount changes, more current flows through the MOSFET than the IGBT, and conversely, when the load current value is larger than I1, the IGBT is used more than the MOSFET. When a large amount of current flows, the loss per switching element is reduced and the efficiency tends to be high.

FIG. 8 is a timing chart showing timing characteristics of switching in the PWM modulation method of the conventional inverter device. In the case of this PWM modulation method, a voltage is output in a sine wave with respect to the phase angle of the rotor (not shown) of the motor 3.

The U-phase, V-phase, and W-phase output voltages are sine wave voltages each having a phase difference of 120 degrees. On the other hand, as shown in FIG. 8, a carrier signal voltage composed of a triangular wave having a predetermined carrier frequency with respect to the sine wave voltage is compared with the sine wave voltage. As a result of comparison, when the output voltage is larger than the carrier signal voltage, the upper arm side switching elements 22 to 24 are turned on by outputting a drive signal to the upper arm side switching elements 22 to 24 and vice versa. The switching elements 25 to 27 on the arm side are turned off.

On the other hand, when the output voltage is smaller than the carrier signal voltage, the lower arm side switching elements 25 to 27 are turned on by outputting a drive signal to the lower arm side switching elements 25 to 27, and conversely, the upper arm side The switching elements 22 to 24 are turned off. As a result, drive signals of switching elements 22 to 27 of U-phase upper arm, V-phase upper arm, W-phase upper arm, U-phase lower arm, V-phase lower arm, W-phase lower arm shown in the lower side of FIG. A waveform (U-phase upper drive to W-phase lower drive) is output.

FIG. 3 is a timing chart showing an example of timing characteristics of switching of the PWM modulation system of the inverter device according to the first embodiment of the present invention.

When the control unit 21 controls switching of the switching elements 22 to 27 and outputs a sine wave voltage to the motor 3 in accordance with the PWM modulation method, the voltage output to three phases (U phase, V phase, W phase) of the motor 3 The average output voltage which is an average value is set to 1/2 of the power supply voltage supplied to the switching circuit in a general inverter device. That is, the average output voltage of the inverter device is set to the voltage of the DC part, that is, the value Vdc / 2 which is half the voltage across the smoothing capacitor 5. Thereby, sine wave voltages having a phase difference of 120 degrees from each other are output from the inverter device to the motor 3.

On the other hand, in the case of the inverter device 2 according to the first embodiment of the present invention, when the output current value (load current value) output to the motor 3 is low, the average output voltage value is Vdc /, as shown in FIG. It is set to a value lower than 2 (in this case, Vdc / 8). That is, the control unit 21 shifts the average output voltage to a lower voltage side than the intermediate voltage of the power supply voltages supplied to the switching circuit 20. Although the average output voltage output to the motor 3 decreases, the line voltage applied between the terminals of the three-phase winding of the motor 3 is the same as that in the case of the sine wave voltage waveform shown in FIG. Therefore, the motor 3 performs the same operation. When the value of the output current to the motor 3 is smaller than I1 (FIG. 2), the efficiency of the inverter device 2 can be improved by outputting a voltage having a reduced average voltage to the motor 3.

The principle will be described with reference to FIG. FIG. 4 is an example of a characteristic diagram showing the characteristics of the amount of current flowing in the switching elements on the upper arm side and the lower arm side of the inverter device according to the first embodiment of the present invention. Here, the amount of current flowing through the switching element is a time integral value of the current flowing through the switching element.

FIG. 4 shows the switching elements 22 to 24 on the upper arm side and the switching elements 25 to 25 on the lower arm side when the average output voltage value of the inverter device 2 is set to a value lower than Vdc / 2 as shown in FIG. 27 shows the characteristics of the amount of current flowing.

When the average output voltage value of inverter device 2 is lower than Vdc / 2, the amount of current (the amount of lower arm current) flowing through switching elements 25 to 27 on the lower arm side is substantially equal to all average output voltage regions. And the amount of current flowing to the switching elements 22 to 24 on the upper arm side (upper arm current amount).

When the average output voltage value of inverter device 2 is lower than Vdc / 2, the time when the output voltage becomes smaller than the carrier signal voltage is longer than the time when the output voltage becomes larger than the carrier signal voltage. The drive signal waveform to drive is as shown in the lower side of FIG. Therefore, when the switching element of the inverter device 2 is driven by the drive signal waveform shown in FIG. 3, the on time of the switching elements 25 to 27 on the lower arm side is longer than the on time of the switching elements 22 to 24 on the upper arm side. become longer.

As a result, the amount of current which is the integral value of the current flowing in the MOSFET which is the switching element on the lower arm side becomes larger than the amount of current which is the integral value of the current flowing in the IGBT which is the switching element on the upper arm side. Further, in this case, since the output current value of the motor 3 is lower than I1, the efficiency of the MOSFET which is the switching element on the lower arm side is higher than that of the IGBT which is the switching element on the upper arm side. That is, the MOSFET which is the switching element on the lower arm side has a smaller on-resistance than the IGBT which is the switching element on the upper arm side. As a result, the loss of the inverter device, which is the sum of the losses of the switching elements on the upper arm side and the lower arm side, can be reduced as compared with the drive system having the average output voltage value Vdc / 2 shown in FIG.

That is, the efficiency of the upper arm IGBT is η (IGBT), the efficiency of the lower arm MOSFET is η (MOSFET), the amount of current flowing through the upper arm IGBT is P (IGBT), and the lower arm MOSFET is flowing When the amount of current is P (MOSFET), the total loss L (TOTAL) is given by (Expression 1) shown below.

(Formula 1)
L (TOTAL) ∝ P (IGBT) × (1-((IGBT)) + P (MOSFET) × (1-((MOSFET))
In this case, since η (MOSFET) is larger than η (IGBT) and P (MOSFET) is larger than P (IGBT), the total loss L (TOTAL) is P (MOSFET) and P (IGBT) Is reduced compared to the case where

FIG. 5 is a timing chart showing another example of the timing characteristic of switching of the PWM modulation system of the inverter device in the first embodiment of the present invention.

When the output current value output from inverter device 2 to motor 3 is larger than I1 shown in FIG. 2, as shown in FIG. 5, the average output voltage value of inverter device 2 is higher than Vdc / 2 (this value In this case, it is set to 7 × Vdc / 8). That is, the control unit 21 shifts the average output voltage to a higher voltage side than the intermediate voltage of the power supply voltages supplied to the switching circuit 20. Although the average output voltage output to the motor 3 increases, the line voltage applied between the terminals of the three-phase winding of the motor 3 is the same as in the case of FIG. In this case, the efficiency of the inverter device 2 can be improved by outputting to the motor 3 a voltage obtained by increasing the average voltage.

The principle will be described with reference to FIG. FIG. 6 is another example of the characteristic diagram showing the characteristics of the amount of current flowing in the switching elements on the upper arm side and the lower arm side of the inverter device according to the first embodiment of the present invention.

When the output current value output to the motor 3 is larger than I1, as shown in FIG. 5, the average output voltage value of the inverter device 2 is set to a value higher than Vdc / 2. When the inverter device 2 is operated as described above, as can be seen from the drive signal waveform of the switching element in FIG. 5, the on time of the switching elements 22 to 24 on the upper arm side It will be longer than 27 on-time. This is because, since the average output voltage is high, the time when the output voltage becomes larger than the carrier signal voltage is longer than the time when the output voltage becomes smaller than the carrier signal voltage.

As a result, the amount of current which is the integral value of the current flowing to the IGBT which is the switching element on the upper arm side is larger than the amount of current which is the integral value of the current flowing to the MOSFET which is the switching element on the lower arm side. Further, in this case, since the output current value is larger than I1, the IGBT as the switching element on the upper arm side has higher efficiency than the MOSFET as the switching element on the lower arm side. That is, the IGBT as the switching element on the upper arm side has a smaller on-resistance than the MOSFET as the switching element on the lower arm side. As a result, the loss of the inverter device 2 which is the sum of the losses of the switching elements on the upper arm side and the lower arm side can be reduced as compared with the driving method in which the average output voltage value shown in FIG. it can.

That is, since η (IGBT) is larger than η (MOSFET) and P (IGBT) is larger than P (MOSFET), the total loss L (TOTAL) is equal to P (MOSFET) and P (IGBT) It is reduced compared to the case.

FIG. 7 is a characteristic diagram showing switching characteristics of the average output voltage with respect to the output current in the control unit of the inverter device in the first embodiment of the present invention. The control unit 21 changes the three-phase alternating current average output voltage value output by the inverter device 2 based on the output current values detected by the

current detection units

28a and 28b. That is, the control unit 21 compares the magnitudes of the output current values detected by the

current detection units

28a and 28b with I1, which is a predetermined current value defined by the switching element on the upper arm side and the switching element on the lower arm side. And the comparison unit 29 that compares the The control unit 21 determines the magnitude relationship between the on resistance of the switching elements 22 to 24 on the upper arm side and the on resistance of the switching elements 25 to 27 on the lower arm side based on the determination result of the comparing unit 29. The average output voltage may be set based on the comparison result of In particular, when the output current value is I1, the average output voltage value is set to Vdc / 2.

Thereby, current flows evenly to the switching elements on the upper arm side and the lower arm side.

Furthermore, if the output current value is larger than I1, the average output voltage value is increased from Vdc / 2 according to the output current value. As a result, the amount of current flowing to the switching elements 22 to 24 on the upper arm side is made larger than the amount of current flowing to the switching elements 25 to 27 on the lower arm side, and the load of the switching elements 22 to 24 on the upper arm side is high. It makes it heavy and reduces the loss in the inverter apparatus 2 (switching circuit 20) total.

Conversely, if the output current value is smaller than I1, the average output voltage value is decreased from Vdc / 2 according to the output current value. As a result, the amount of current flowing through the switching elements 25 to 27 on the lower arm side is increased more than the amount of current flowing to the switching elements 22 to 24 on the upper arm side, and the load on the switching elements on the lower arm side with high efficiency is increased. The total loss of the inverter device 2 (switching circuit 20) is reduced.

Furthermore, in this case, P (IGBT) × (1-η (IGBT)), which is a loss generated in the IGBT as the switching element on the upper arm side, and a loss generated in the MOSFET as the switching element on the lower arm side P (MOSFET) × (1−η (MOSFET)) has almost equal values. Therefore, the loss balance of the switching elements on the upper arm side and the lower arm side is maintained, whereby the heat generation balance of the switching elements is maintained, and an inverter device with high reliability is realized.

In the first embodiment, the MOSFET is used as the lower arm side switching elements 25 to 27 as a high efficiency switching element at low load, and the IGBT is an upper arm side switching element 22 as a high efficiency switching element at high load. Used as ~ 24. However, when the MOSFET is used as the switching element 22 to 24 on the upper arm side as a high efficiency switching element at low load, and the IGBT is used as the switching element 25 to 27 on the lower arm side as a high efficiency switching element at high load Have the same effect.

In that case, if the output current value is larger than I1, the average output voltage value is decreased according to the output current value. As a result, the amount of current flowing to the lower arm side switching elements 25 to 27 is increased, the load on the lower arm side switching elements 25 to 27 with high efficiency is increased, and the total loss of the inverter device 2 (switching circuit 20) Reduce

Conversely, if the output current value is smaller than I1, the average output voltage value is increased according to the output current value. As a result, the amount of current flowing to the switching elements 22 to 24 on the upper arm side is increased, the load on the switching elements 22 to 24 on the upper arm side with high efficiency is increased, and the total loss of the inverter device 2 (switching circuit 20) Reduce

In the first embodiment, a MOSFET is used as a high efficiency switching element at low load, and an IGBT is used as a high efficiency switching element at high load, but other elements having similar characteristics may be used. Elements may be used. For example, semiconductor elements such as gallium nitride (GaN) transistors may be used instead of MOSFETs, and bipolar transistors may be used instead of IGBTs.

As described above, the inverter device of the present invention includes the switching circuit configured of the plurality of upper and lower arms, and the control unit that drives the switching circuit by the PWM modulation method. The switching element forming the upper arm side switching circuit and the switching element forming the lower arm side switching circuit are formed by different types of switching elements. The control unit switches the average output voltage based on a condition that determines the magnitude relationship between the on resistance of the switching element that configures the lower arm side switching circuit and the on resistance of the switching element that configures the upper arm side switching circuit. Shift to the lower voltage side or higher voltage side than the intermediate voltage of the power supply voltage supplied to the

Further, in the inverter device according to the present invention, the controller outputs an average output under the condition that the on resistance of the switching element constituting the lower arm side switching circuit is smaller than the on resistance of the switching element constituting the upper arm side switching circuit. The voltage is shifted to a lower voltage side than the intermediate voltage of the power supply voltage. Further, under the condition that the ON resistance of the switching element constituting the upper arm side switching circuit is smaller than the ON resistance of the switching element constituting the lower arm side switching circuit, the control unit sets the average output voltage to the middle of the power supply voltage. Shift to a higher voltage than the voltage.

The inverter device according to the present invention further includes a current detection unit that detects an output current value. The control unit determines a comparison unit that determines the magnitude relationship between the output current value detected by the current detection unit and the predetermined current value defined by the switching elements that constitute the upper arm switching circuit and the lower arm switching circuit. Have. The control unit determines, based on the determination result of the comparison unit, the magnitude relationship between the on resistance of the switching element forming the upper arm side switching circuit and the on resistance of the switching element forming the lower arm side switching circuit.

With such a configuration, it is possible to easily determine the load condition in which the upper arm switching element has high efficiency and the load condition in which the lower arm switching element has high efficiency.

Further, in the inverter device according to the present invention, the control unit shifts the average output voltage value in accordance with the magnitude of the output current value detected by the current detection unit.

With such a configuration, losses generated in the switching element on the upper arm side and the switching element on the lower arm side become substantially equal values. Therefore, the loss balance of the switching elements on the upper arm side and the lower arm side is maintained, whereby the heat generation balance of the switching elements is maintained, and an inverter device with high reliability is realized.

Further, in the inverter device of the present invention, different types of switching elements constituting the upper arm side switching circuit and the lower arm side switching circuit are a MOSFET and an IGBT.

With such a configuration, an inverter device with high conversion efficiency is realized regardless of load conditions.

Further, in the inverter device of the present invention, different types of switching elements constituting the upper arm side switching circuit and the lower arm side switching circuit are a GaN transistor and an IGBT.

As described above, the inverter device according to the present invention is used for an inverter device that reduces inverter circuit loss by optimally performing drive control of switching elements, and is useful for an inverter device with high efficiency and high reliability.

DESCRIPTION OF SYMBOLS 1 AC power supply 2 inverter apparatus 3 motor 4 rectifier circuit 5 smoothing capacitor 20 switching circuit 20 u upper arm side switching circuit 20 d lower arm side switching circuit 21 control part 22 to 24 upper arm side switching element 25 to 27 lower arm

side switching element

28a, 28b current detection unit 29 comparison unit

Claims

A switching circuit comprising a plurality of upper and lower arms,
An inverter device including a control unit that drives the switching circuit by a PWM modulation method;
The switching element constituting the upper arm side switching circuit and the switching element constituting the lower arm side switching circuit are constituted by different types of switching elements,
The control unit is an average output voltage based on a condition that determines the magnitude relationship between the on resistance of the switching element that configures the lower arm side switching circuit and the on resistance of the switching element that configures the upper arm side switching circuit. The inverter device is shifted to a lower voltage side or a higher voltage side than an intermediate voltage of the power supply voltage supplied to the switching circuit.
The control unit is configured to set the average output voltage to the power supply under the condition that the on resistance of the switching element forming the lower arm side switching circuit is smaller than the on resistance of the switching element forming the upper arm side switching circuit. Under the condition that the on-resistance of the switching element forming the upper arm side switching circuit is smaller than the on resistance of the switching element forming the lower arm side switching circuit by shifting the voltage to a lower voltage side than the intermediate voltage of the voltage. The inverter device according to claim 1, wherein the average output voltage is shifted to a higher voltage side than an intermediate voltage of the power supply voltage.
It further comprises a current detection unit that detects the output current value,
The control unit sets the magnitude relationship between the output current value detected by the current detection unit and a predetermined current value defined by switching elements constituting the upper arm side switching circuit and the lower arm side switching circuit. Have a comparator to determine
The control unit determines, based on the determination result of the comparison unit, the magnitude relationship between the on resistance of the switching element constituting the upper arm side switching circuit and the on resistance of the switching element constituting the lower arm side switching circuit. The inverter device according to claim 2, characterized in that:
The inverter device according to claim 3, wherein the control unit shifts the average output voltage value in accordance with the magnitude of the output current value detected by the current detection unit.
The inverter device according to claim 1, wherein the different types of switching elements constituting the upper arm side switching circuit and the lower arm side switching circuit are a MOSFET and an IGBT.
The inverter device according to claim 1, wherein the different types of switching elements constituting the upper arm side switching circuit and the lower arm side switching circuit are a GaN transistor and an IGBT.