Patent Description:
For example, Patent Literature <NUM> (<CIT>) discloses a known inverter device for driving a three-phase motor. The inverter device includes a bootstrap capacitor that obtains operating voltage for switching elements in order to drive an upper arm-side switching element.

<CIT> discloses an inverter device comprising: a printed wiring board; an intelligent power module mounted on a first surface of the printed wiring board, the intelligent power module including a package and an upper arm-side switching element and a lower arm-side switching element incorporated in the package and constituting at least an inverter circuit; and a bootstrap capacitor mounted on the first surface of the printed wiring board, the bootstrap capacitor being configured to be charged during an ON operation of the lower arm-side switching element and generate a potential higher than a low potential at the upper arm-side switching element.

However, a predetermined insulation distance required between the bootstrap capacitor and a terminal of an intelligent power module hinders high density integration of components. In addition, the insulation distance, when being considerably long, may cause superimposition of switching noise on a bootstrap circuit, resulting in malfunction of the intelligent power module.

Consequently, there is an issue of how to achieve high density integration of components while securing an insulation distance between a bootstrap capacitor and a terminal of an intelligent power module.

The invention is defined by the features of claim <NUM>. The dependent claims recite advantageous embodiments of the invention.

In an ordinary situation, no circuit is present on a printed wiring board directly below an intelligent power module. According to the inverter device of claim <NUM>, the bootstrap capacitor is placed between the printed wiring board and the intelligent power module. This configuration therefore allows the bootstrap capacitor and the intelligent power module to be placed in the same region in plan view while securing a required insulation distance between the bootstrap capacitor and a terminal of the intelligent power module. This configuration thus eliminates a possibility that the intelligent power module malfunctions, and achieves high density integration of the components.

Moreover, according to the inverter device of claim <NUM>, the bootstrap capacitor is placed below the low heat generation region. The bootstrap capacitor is therefore less susceptible to a thermal influence.

Furthermore, according to the inverter device of claim <NUM>, the bootstrap capacitor is placed below the control circuit that is smaller in heating value than the inverter circuit. The bootstrap capacitor is therefore less susceptible to a thermal influence of the inverter circuit.

Furthermore, according to the inverter device of claim <NUM>, the intelligent power module and the heat sink are placed beside the first surface of the printed wiring board. This configuration therefore achieves high integration of the components.

According to the inverter device of claim <NUM>, the intelligent power module and the converter are placed beside the first surface of the printed wiring board. This configuration therefore achieves high density integration of the components.

<FIG> is a circuit diagram illustrating connection between a three-phase motor <NUM> and a motor driver <NUM> including an inverter device according to an embodiment of the present disclosure. As illustrated in <FIG>, the motor driver <NUM> and the motor <NUM> constitute a system <NUM>. The inverter device includes at least an intelligent power module <NUM>.

The motor <NUM> is a three-phase brushless DC motor and includes a stator <NUM> and a rotor <NUM>. The stator <NUM> includes a U-phase drive coil Lu, a V-phase drive coil Lv, and a W-phase drive coil Lw that are star-connected. The drive coil Lu has a first end connected to a drive coil terminal TU of a U-phase wire extending from an inverter circuit <NUM>. The drive coil Lv has a first end connected to a drive coil terminal TV of a V-phase wire extending from the inverter circuit <NUM>. The drive coil Lw has a first end connected to a drive coil terminal TW of a W-phase wire extending from the inverter circuit <NUM>. The drive coils Lu, Lv, and Lw have second ends connected to each other as a terminal TN. The drive coils Lu, Lv, and Lw of the three phases generate, by rotation of the rotor <NUM>, an induced voltage according to the rotational speed and position of the rotor <NUM>.

The rotor <NUM> includes a multi-polar permanent magnet including an N-pole and an S-pole, and rotates about an axis of rotation with respect to the stator <NUM>.

The motor <NUM> is usable as, for example, a compressor motor and a fan motor in a heat pump-type air conditioner.

As illustrated in <FIG>, the motor driver <NUM> includes a rectifier <NUM>, a smoothing capacitor <NUM>, a voltage detector <NUM>, a current detector <NUM>, the intelligent power module <NUM>, and a microcomputer <NUM>. These components are mounted on a printed wiring board <NUM>.

The rectifier <NUM> is a bridge rectifier and includes four diodes D1a, D1b, D2a, and D2b. Specifically, the diodes D1a and D1b are connected in series, and the diodes D2a and D2b are connected in series. The diodes D1a and D2a each include a cathode terminal connected to a positive-side terminal of the smoothing capacitor <NUM> to function as a positive-side output terminal of the rectifier <NUM>. The diodes D1b and D2b each include an anode terminal connected to a negative-side terminal of the smoothing capacitor <NUM> to function as a negative-side output terminal of the rectifier <NUM>.

A node between the diode D1a and the diode D1b is connected to a first pole of a commercial power supply <NUM>. A node between the diode D2a and the diode D2b is connected to a second pole of the commercial power supply <NUM>. The rectifier <NUM> rectifies an alternating-current voltage output from the commercial power supply <NUM> to generate direct-current power, and supplies the direct-current power to the smoothing capacitor <NUM>.

The smoothing capacitor <NUM> has a first end connected to the positive-side output terminals of the rectifier <NUM> and a second end connected to the negative-side output terminals of the rectifier <NUM>. The smoothing capacitor <NUM> smooths a voltage rectified by the rectifier <NUM>. For convenience of the description, the voltage smoothed by the smoothing capacitor <NUM> is referred to as a direct-current voltage Vdc below.

The direct-current voltage Vdc is applied to the inverter circuit <NUM> connected to the output side of the smoothing capacitor <NUM>. The rectifier <NUM> and the smoothing capacitor <NUM> constitute a power supply <NUM> for the inverter circuit <NUM>.

Examples of the capacitor may include, but not limited to, an electrolytic capacitor, a film capacitor, and a tantalum capacitor. In this embodiment, the smoothing capacitor <NUM> is a film capacitor.

The voltage detector <NUM> is connected to the output side of the smoothing capacitor <NUM>, and is configured to detect a value of a voltage across the smoothing capacitor <NUM>, that is, a value of the direct-current voltage Vdc. For example, the voltage detector <NUM> includes two resistors connected in series, and the two resistors are connected in parallel with the smoothing capacitor <NUM> to divide the direct-current voltage Vdc. The voltage detector <NUM> outputs, to the microcomputer <NUM>, a value of a voltage at a node between the two resistors.

The current detector <NUM> is located between the smoothing capacitor <NUM> and the inverter circuit <NUM>, and is connected to the negative-side output terminal of the smoothing capacitor <NUM>. After startup of the motor <NUM>, the current detector <NUM> detects a motor current Im passing through the motor <NUM> as a sum of currents for the three phases.

The current detector <NUM> may be, for example, an amplifier circuit including a shunt resistor and an operational amplifier configured to amplify a voltage across the shunt resistor. The current detector <NUM> outputs the motor current thus detected to the microcomputer <NUM>.

The intelligent power module <NUM> is a component obtained by incorporating, in one module, the inverter circuit <NUM> including switching elements connected in series and a control circuit <NUM> having a gate control function for driving the inverter circuit <NUM>.

The inverter circuit <NUM> includes three upper arms connected in parallel and three lower arms connected in parallel. These upper and lower arms are provided for the U, V, and W-phase drive coils Lu, Lv, and Lw of the motor <NUM>, respectively, and are connected to the output side of the smoothing capacitor <NUM>.

As illustrated in <FIG>, the inverter circuit <NUM> includes a plurality of insulated gate bipolar transistors (IGBTs) (hereinafter, simply referred to as transistors) Q3a, Q3b, Q4a, Q4b, Q5a, and Q5b and a plurality of reflux diodes D3a, D3b, D4a, D4b, D5a, and D5b.

The transistors Q3a and Q3b are connected in series to constitute the upper and lower arms, and an output line extends from a node NU between the transistors Q3a and Q3b toward the U-phase drive coil Lu. The transistors Q4a and Q4b are connected in series to constitute the upper and lower arms, and an output line extends from a node NV between the transistors Q4a and Q4b toward the V-phase drive coil Lv. The transistors Q5a and Q5b are connected in series to constitute the upper and lower arms, and an output line extends from a node NW between the transistors Q5a and Q5b toward the W-phase drive coil Lw.

The diodes D3a to D5b are respectively connected in parallel with the transistors Q3a to Q5b with the collector terminal of each transistor connected to the cathode terminal of the corresponding diode and the emitter terminal of each transistor connected to the anode terminal of the corresponding diode. Each transistor and the corresponding diode, which are connected in parallel, constitute a switching element.

The inverter circuit <NUM> receives the direct-current voltage Vdc from the smoothing capacitor <NUM> and turns on and off the transistors Q3a to Q5b at timings instructed by the control circuit <NUM> to generate drive voltages SU, SV, and SW for driving the motor <NUM>. The drive voltage SU is output to the drive coil Lu of the motor <NUM> via the node NU between the transistors Q3a and Q3b. The drive voltage SV is output to the drive coil Lv of the motor <NUM> via the node NV between the transistors Q4a and Q4b. The drive voltage SW is output to the drive coil Lw of the motor <NUM> via the node NW between the transistors Q5a and Q5b.

In this embodiment, the inverter circuit <NUM> is a voltage source inverter. The inverter circuit <NUM> may alternatively be a current source inverter.

The control circuit <NUM> switches between the ON state and the OFF state of each of the transistors Q3a to Q5b of the inverter circuit <NUM>, based on a command voltage Vpwm from the microcomputer <NUM>. Specifically, the control circuit <NUM> generates gate control voltages Gu, Gx, Gv, Gy, Gw, and Gz to be respectively applied to the gates of the transistors Q3a, Q3b, Q4a, Q4b, Q5a, and Q5b such that the inverter circuit <NUM> outputs, to the motor <NUM>, pulsed drive voltages SU, SV, and SW in a duty ratio determined by the microcomputer <NUM>. The gate control voltages Gu, Gx, Gv, Gy, Gw, and Gz thus generated are respectively applied to the gate terminals of the transistors Q3a, Q3b, Q4a, Q4b, Q5a, and Q5b.

The microcomputer <NUM> is connected to the voltage detector <NUM>, the current detector <NUM>, and the control circuit <NUM>. In this embodiment, the microcomputer <NUM> drives the motor <NUM> by a rotor position sensorless method. The microcomputer <NUM> may alternatively drive the motor <NUM> by a sensor method in addition to the rotor position sensorless method.

The rotor position sensorless method refers to a method of driving the motor <NUM> by, for example, estimating the position and number of rotations of the rotor, performing PI control on the number of rotations, and performing PI control on the motor current, using various parameters indicating the characteristics of the motor <NUM>, a result of detection by the voltage detector <NUM> after the startup of the motor <NUM>, a result of detection by the current detector <NUM>, a predetermined mathematical formula model regarding the control of the motor <NUM>, and the like. Examples of the various parameters indicating the characteristics of the motor <NUM> may include, but not limited to, the winding resistance, inductance component, induced voltage, and number of poles of the used motor <NUM>. It should be noted that rotor position sensorless control is described in many patent literatures; therefore, refer to these patent literatures (e.g., <CIT>) for the details thereof.

The microcomputer <NUM> also performs protection control of monitoring a value detected by the voltage detector <NUM> and turning off the transistors Q3a to Q5b when the value detected by the voltage detector <NUM> exceeds a predetermined threshold value.

The control circuit <NUM> appropriately inputs a gate potential to each of the upper arm-side transistors Q3a, Q4a, and Q5a via a bootstrap circuit <NUM> disposed between each of the emitters of the transistors Q3a, Q4a, and Q5a and a positive electrode of a drive power supply Vb connected to a terminal Vcc.

A first bootstrap circuit 48A for a first control circuit 26A includes a first capacitor 45A, a first resistor 46A, and a first diode 47A. A second bootstrap circuit 48B for a second control circuit 26B includes a second capacitor 45B, a second resistor 46B, and a second diode 47B. A third bootstrap circuit 48C for a third control circuit 26C includes a third capacitor 45C, a third resistor 46C, and a third diode 47C.

In the following, a common description on the first bootstrap circuit 48A, the second bootstrap circuit 48B, and the third bootstrap circuit 48C will be given using an expression of bootstrap circuits <NUM>.

Likewise, a common description on the first capacitor 45A, the second capacitor 45B, and the third capacitor 45C will be given using an expression of capacitors <NUM>.

Likewise, a common description on the first resistor 46A, the second resistor 46B, and the third resistor 46C will be given using an expression of resistors <NUM>.

Likewise, a common description on the first diode 47A, the second diode 47B, and the third diode 47C will be given using an expression of diodes <NUM>.

It should be noted that the diodes <NUM> are omittable in a case where the intelligent power module <NUM> includes a diode for a bootstrap circuit.

As illustrated in <FIG>, the first capacitor 45A has a first end connected to a node between the emitter of the upper arm-side transistor Q3a and the collector of the lower arm-side transistor Q3b. The first capacitor 45A has a second end connected to the positive electrode of the drive power supply Vb via the first resistor 46A and the first diode 47A.

The first resistor 46A is provided for restricting a charge current passing through the first capacitor 45A. The first diode 47A has a forward direction oriented from the positive electrode of the drive power supply Vb toward the first capacitor 45A so as to prevent the first capacitor 45A from being discharged via the first resistor 46A.

The first control circuit 26A includes an upper arm-side control circuit 26Aa configured to receive a high potential from the first capacitor 45A in order to control the ON/OFF state of the transistor Q3a. The first control circuit 26A also includes a lower arm-side control circuit 26Ab configured to control the ON/OFF state of the transistor Q3b. However, since the emitter of the transistor Q3b is grounded, the lower arm-side control circuit 26Ab is capable of controlling the ON/OFF state of the transistor Q3b, using a potential at the positive electrode of the drive power supply Vb connected to the terminal Vcc.

The second capacitor 45B has a first end connected to a node between the emitter of the upper arm-side transistor Q4a and the collector of the lower arm-side transistor Q4b. The second capacitor 45B has a second end connected to the positive electrode of the drive power supply Vb via the second resistor 46B and the second diode 47B.

The second resistor 46B is provided for restricting a charge current passing through the second capacitor 45B. The second diode 47B has a forward direction oriented from the positive electrode of the drive power supply Vb toward the second capacitor 45B so as to prevent the second capacitor 45B from being discharged via the second resistor 46B.

The second control circuit 26B includes an upper arm-side control circuit 26Ba configured to receive a high potential from the second capacitor 45B in order to control the ON/OFF state of the transistor Q4a. The second control circuit 26B also includes a lower arm-side control circuit 26Bb configured to control the ON/OFF state of the transistor Q4b. However, since the emitter of the transistor Q4b is grounded, the lower arm-side control circuit 26Bb is capable of controlling the ON/OFF state of the transistor Q4b, using a potential at the positive electrode of the drive power supply Vb connected to the terminal Vcc.

The third capacitor 45C has a first end connected to a node between the emitter of the upper arm-side transistor Q5a and the collector of the lower arm-side transistor Q5b. The third capacitor 45C has a second end connected to the positive electrode of the drive power supply Vb via the third resistor 46C and the third diode 47C.

The third resistor 46C is provided for restricting a charge current passing through the third capacitor 45C. The third diode 47C has a forward direction oriented from the positive electrode of the drive power supply Vb toward the third capacitor 45C so as to prevent the third capacitor 45C from being discharged via the third resistor 46C.

The third control circuit 26C includes an upper arm-side control circuit 26Ca configured to receive a high potential from the third capacitor 45C in order to control the ON/OFF state of the transistor Q5a. The third control circuit 26C also includes a lower arm-side control circuit 26Cb configured to control the ON/OFF state of the transistor Q5b. However, since the emitter of the transistor Q5b is grounded, the lower arm-side control circuit 26Cb is capable of controlling the ON/OFF state of the transistor Q5b, using a potential at the positive electrode of the drive power supply Vb connected to the terminal Vcc.

<FIG> is a plan view of the intelligent power module <NUM>. As seen in front view of <FIG>, a package 43a incorporates therein the control circuit <NUM> located on a left side thereof and the inverter circuit <NUM> located on a right side thereof.

A first contact pin group P1 and a second contact pin group P2 protrude from a left end of the control circuit <NUM>. The first contact pin group P1 receives a potential at each capacitor <NUM>. The second contact pin group P2 receives a drive voltage and a control signal.

A third contact pin group P3 protrudes from a right end of the inverter circuit <NUM>. The third contact pin group P3 outputs power converted by the inverter circuit <NUM>.

<FIG> is a partial plan view of the printed wiring board <NUM> on which no components are mounted, and illustrates regions R1 to R3 where the capacitors <NUM> are respectively placed and a region R4 where the intelligent power module <NUM> is placed.

In <FIG>, the regions R1 to R3, each of which is surrounded by a chain double-dashed line, are regions where the capacitors <NUM> are respectively mounted. Specifically, the first capacitor 45A is mounted on the region R1, the second capacitor 45B is mounted on the region R2, and the third capacitor 45C is mounted on the region R3.

Also in <FIG>, the region R4, which is surrounded by a chain double-dashed line, is a region where the intelligent power module <NUM> is mounted. The regions R1 to R3 are located in the region R4.

The region R4 has a plurality of round hole lands located at its left end in front view. The contact pins protruding from the control circuit <NUM> of the intelligent power module <NUM> are respectively inserted in and soldered to the round hole lands.

The plurality of round hole lands include a first land group C1 provided for the first contact pin group P1 illustrated in <FIG>. The round hole lands in the first land group C1 are respectively connected to portions, where the electrodes of the capacitors <NUM> are soldered, via a conductive pattern.

The plurality of round hole lands also include a second land group C2 provided for the second contact pin group P2 illustrated in <FIG>. The second land group C2 is connected to the drive power supply Vb, the microcomputer <NUM>, and the like via the conductive pattern.

The region R4 also has a plurality of oblong hole lands located at its right end in front view. The contact pins protruding from the inverter circuit <NUM> are respectively inserted in and soldered to the oblong hole lands. The plurality of oblong hole lands include a third land group C3 provided for the third contact pin group P3 illustrated in <FIG>. The third land group C3 is connected to the motor <NUM> via the conductive pattern.

The regions R1 to R3 where the capacitors <NUM> are respectively mounted are located near the first land group C1 and are spaced away from the second land group C2 and the third land group C3 by a predetermined distance or more. In this embodiment, the predetermined distance is <NUM> or more in creepage distance and is <NUM> or more in spatial distance. This configuration therefore secures an insulation distance between the intelligent power module <NUM> and the capacitors <NUM> mounted on the printed wiring board <NUM>.

<FIG> is a side view of the capacitors <NUM> and the intelligent power module <NUM> each mounted on the printed wiring board <NUM>. As illustrated in <FIG> and <FIG>, since the regions R1 to R3 are located in the region R4, the capacitors <NUM> are mounted first, and the intelligent power module <NUM> is then mounted so as to be located above the capacitors <NUM>. The capacitors <NUM> are therefore located between a first surface <NUM> of the printed wiring board <NUM> and a first outer surface <NUM> of the intelligent power module <NUM>.

In the intelligent power module <NUM> illustrated in <FIG>, the inverter circuit <NUM> is located on the right side in front view, and the control circuit <NUM> is located on the left side in front view. The inverter circuit <NUM> is larger in heating value than the control circuit <NUM>. In this embodiment, therefore, the capacitors <NUM> are mounted so as to be located below the control circuit <NUM> such that the capacitors <NUM> are less susceptible to an influence of heat generated from the inverter circuit <NUM>.

As illustrated in <FIG>, a heat sink <NUM> is disposed on the intelligent power module <NUM> so as to encourage heat dissipation from the inverter circuit <NUM> heated to high temperatures. The intelligent power module <NUM> has the first outer surface <NUM> facing the first surface <NUM> of the printed wiring board <NUM>, and a second outer surface <NUM> farther from the printed wiring board <NUM> than the first outer surface <NUM> is. The heat sink <NUM> is disposed on the second outer surface <NUM>.

Therefore, the capacitors <NUM> are placed beside the first outer surface <NUM> and the heat sink <NUM> is placed beside the second outer surface <NUM> as seen from the first surface <NUM> of the printed wiring board <NUM>.

As a result, the intelligent power module <NUM> and the heat sink <NUM> are placed beside the first surface <NUM> of the printed wiring board <NUM>. This configuration thus achieves high integration of the components.

(<NUM>-<NUM>)
In the printed wiring board <NUM>, the regions R1 to R3 where the capacitors <NUM> are respectively mounted are located in the region R4 where the intelligent power module <NUM> is mounted. Therefore, the capacitors <NUM> mounted on the printed wiring board <NUM> are placed between the printed wiring board <NUM> and the intelligent power module <NUM>.

In a case of a known printed wiring board, the capacitors <NUM> are mounted outside the region where the intelligent power module <NUM> is mounted. This configuration therefore requires not only an insulation distance between the intelligent power module <NUM> and each capacitor <NUM>, but also an insulation distance between each capacitor <NUM> and another electric component. The use of the known printed wiring board thus leads to an increase in on-board space. Also in the known printed wiring board, there is a possibility that noise caused during operation of the transistors Q3a, Q4a, and Q5a is superimposed on the bootstrap circuits <NUM> to exert an adverse influence on another circuit or to cause malfunction of the intelligent power module <NUM>.

According to this embodiment, however, at least the areas of the regions R1 to R3 where the capacitors <NUM> are mounted and the area of the region corresponding to the insulation distance between the intelligent power module <NUM> and each capacitor <NUM> are reduced from the on-board space of the known printed wiring board.

This configuration therefore allows the capacitors <NUM> and the intelligent power module <NUM> to be placed in the same region in plan view while securing the required insulation distance. This configuration thus achieves high density integration of the components. This configuration also eliminates the possibility that the switching noise is superimposed on the bootstrap circuits <NUM> to exert an adverse influence on another circuit or to cause malfunction of the intelligent power module <NUM>.

(<NUM>-<NUM>)
The intelligent power module <NUM> includes the inverter circuit <NUM> and the control circuit <NUM> configured to control the inverter circuit <NUM>. The inverter circuit <NUM> is larger in heating value than the control circuit <NUM>. The capacitors <NUM> are placed between the printed wiring board <NUM> and the control circuit <NUM>. The capacitors <NUM> are therefore less susceptible to a thermal influence of the inverter circuit <NUM>.

(<NUM>-<NUM>)
The rectifier <NUM> is mounted on the first surface <NUM> of the printed wiring board <NUM>. The rectifier <NUM> converts an alternating-current voltage from the commercial power supply into a direct-current voltage, and supplies the direct-current voltage to the inverter circuit <NUM>. As a result, the intelligent power module <NUM> and the rectifier <NUM> are placed beside the first surface <NUM> of the printed wiring board <NUM>. This configuration therefore achieves high density integration of the components.

(<NUM>-<NUM>)
The intelligent power module <NUM> has the first outer surface <NUM> and the second outer surface <NUM>. The capacitors <NUM> are placed beside the first outer surface <NUM>. The heat sink <NUM> is placed beside the second outer surface <NUM>. As a result, the intelligent power module <NUM> and the heat sink <NUM> are placed beside the first surface <NUM> of the printed wiring board <NUM>. This configuration thus achieves high integration of the components.

(<NUM>-<NUM>)
The printed wiring board <NUM> has the plurality of lands in and to which the contact pins of the intelligent power module <NUM> are inserted and soldered. The first contact pin group P1, that receives a potential at each capacitor <NUM> is soldered to the first land group C1. The second contact pin group P2 that receives a potential at the drive power supply Vb and a control signal from the microcomputer <NUM> is soldered to the second land group C2. The capacitors <NUM> are placed beside the first contact pin group P1 at the position away from the second contact pin group P2 by the predetermined insulation distance.

<FIG> are side views of the intelligent power module <NUM> and its periphery in a case where the intelligent power module <NUM> and another power module <NUM> adjacent thereto share one heat sink <NUM>.

As illustrated in <FIG>, heretofore, a resin spacer Sp has been required for aligning the height of an intelligent power module <NUM> with the height of another power module <NUM> adjacent to the intelligent power module <NUM>.

According to this embodiment, as illustrated in <FIG>, each capacitor <NUM> placed between the printed wiring board <NUM> and the intelligent power module <NUM> serves as the resin spacer Sp. This configuration therefore eliminates the necessity of the resin spacer Sp. This configuration thus achieves reduction in number of components and high density integration of circuits.

While various embodiments of the present disclosure have been described herein above, it is to be appreciated that various changes in form and detail may be made without departing from the scope of the appended claims.

Claim 1:
An inverter device comprising:
a printed wiring board (<NUM>);
an intelligent power module (<NUM>) mounted on a first surface (<NUM>) of the printed wiring board (<NUM>),
the intelligent power module (<NUM>) including
a package and
an upper arm-side switching element and a lower arm-side switching element incorporated in the package and constituting at least an inverter circuit (<NUM>); and
a bootstrap capacitor (<NUM>) mounted on the first surface (<NUM>) of the printed wiring board (<NUM>),
the bootstrap capacitor (<NUM>) being configured to be charged during an ON operation of the lower arm-side switching element and generate a potential higher than a low potential at the upper arm-side switching element,
characterized in that:
the bootstrap capacitor (<NUM>) is placed between the printed wiring board (<NUM>) and the intelligent power module (<NUM>);
the intelligent power module (<NUM>) has at least two regions that are different in heating value from each other, and
the bootstrap capacitor (<NUM>) is placed between the printed wiring board (<NUM>) and a low heat generation region with a smaller heating value of the at least two regions;
the intelligent power module (<NUM>) further includes a control circuit (<NUM>) configured to control the inverter circuit (<NUM>), and
the bootstrap capacitor (<NUM>) is placed between the printed wiring board (<NUM>) and the control circuit (<NUM>) of the intelligent power module (<NUM>); and
the inverter device further comprises a heat sink (<NUM>) configured to encourage heat dissipation from the intelligent power module (<NUM>),
wherein
the intelligent power module (<NUM>) has a first outer surface (<NUM>) and a second outer surface (<NUM>),
the bootstrap capacitor (<NUM>) is placed beside the first outer surface (<NUM>), and
the heat sink (<NUM>) is placed beside the second outer surface (<NUM>).