Patent Publication Number: US-2023145005-A1

Title: Inverter device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of PCT International Application No. PCT/JP2021/024185, filed on Jun. 25, 2021, which claims priority under 35 U.S.C. 119(a) to Patent Application No. 2020-112083, filed in Japan on Jun. 29, 2020, all of which are hereby expressly incorporated by reference into the present application. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to an inverter device including a bootstrap circuit. 
     BACKGROUND ART 
     For example, Patent Literature 1 (WO2018-003827) 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. 
     SUMMARY 
     A first aspect is directed to an inverter device including a printed wiring board, an intelligent power module, and a bootstrap capacitor. The intelligent power module is mounted on a first surface of the printed wiring board. The intelligent power module includes 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. The bootstrap capacitor is mounted on the first surface of the printed wiring board. The bootstrap capacitor is charged during an ON operation of the lower arm-side switching element and generates a potential higher than a low potential at the upper arm-side switching element. The bootstrap capacitor is placed between the printed wiring board and the intelligent power module. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a circuit diagram illustrating connection between a three-phase motor and a motor driver including an inverter device according to an embodiment of the present disclosure. 
         FIG.  2    is a circuit diagram illustrating the connection between the three-phase motor and the inverter device in  FIG.  1   . 
         FIG.  3    is a plan view of an intelligent power module. 
         FIG.  4    is a partial plan view of a printed wiring board on which no components are mounted, and illustrates a region where a capacitor is placed and a region where the intelligent power module is placed. 
         FIG.  5    is a side view of the capacitor and the intelligent power module each mounted on the printed wiring board. 
         FIG.  6 A  is a side view of an intelligent power module and its periphery in a case where the intelligent power module and another power module adjacent thereto share one heat sink. 
         FIG.  6 B  is a side view of the intelligent power module and its periphery in a case where the intelligent power module and another power module adjacent thereto share one heat sink. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     (1) Overview 
       FIG.  1    is a circuit diagram illustrating connection between a three-phase motor  51  and a motor driver  10  including an inverter device according to an embodiment of the present disclosure. As illustrated in  FIG.  1   , the motor driver  10  and the motor  51  constitute a system  100 . The inverter device includes at least an intelligent power module  43 . 
     (1-1) Motor  51   
     The motor  51  is a three-phase brushless DC motor and includes a stator  52  and a rotor  53 . The stator  52  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  25 . 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  25 . 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  25 . 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  53 , an induced voltage according to the rotational speed and position of the rotor  53 . 
     The rotor  53  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  52 . 
     The motor  51  is usable as, for example, a compressor motor and a fan motor in a heat pump-type air conditioner. 
     (1-2) Motor Driver  10   
     As illustrated in  FIG.  1   , the motor driver  10  includes a rectifier  21 , a smoothing capacitor  22 , a voltage detector  23 , a current detector  24 , the intelligent power module  43 , and a microcomputer  80 . These components are mounted on a printed wiring board  40 . 
     (2) Specific Configuration of Motor Driver  10   
     (2-1) Rectifier  21   
     The rectifier  21  is a bridge rectifier and includes four diodes D 1   a , D 1   b , D 2   a , and D 2   b . Specifically, the diodes D 1   a  and D 1   b  are connected in series, and the diodes D 2   a  and D 2   b  are connected in series. The diodes D 1   a  and D 2   a  each include a cathode terminal connected to a positive-side terminal of the smoothing capacitor  22  to function as a positive-side output terminal of the rectifier  21 . The diodes D 1   b  and D 2   b  each include an anode terminal connected to a negative-side terminal of the smoothing capacitor  22  to function as a negative-side output terminal of the rectifier  21 . 
     A node between the diode D 1   a  and the diode D 1   b  is connected to a first pole of a commercial power supply  91 . A node between the diode D 2   a  and the diode D 2   b  is connected to a second pole of the commercial power supply  91 . The rectifier  21  rectifies an alternating-current voltage output from the commercial power supply  91  to generate direct-current power, and supplies the direct-current power to the smoothing capacitor  22 . 
     (2-2) Smoothing Capacitor  22   
     The smoothing capacitor  22  has a first end connected to the positive-side output terminals of the rectifier  21  and a second end connected to the negative-side output terminals of the rectifier  21 . The smoothing capacitor  22  smooths a voltage rectified by the rectifier  21 . For convenience of the description, the voltage smoothed by the smoothing capacitor  22  is referred to as a direct-current voltage Vdc below. 
     The direct-current voltage Vdc is applied to the inverter circuit  25  connected to the output side of the smoothing capacitor  22 . The rectifier  21  and the smoothing capacitor  22  constitute a power supply  20  for the inverter circuit  25 . 
     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  22  is a film capacitor. 
     (2-3) Voltage Detector  23   
     The voltage detector  23  is connected to the output side of the smoothing capacitor  22 , and is configured to detect a value of a voltage across the smoothing capacitor  22 , that is, a value of the direct-current voltage Vdc. For example, the voltage detector  23  includes two resistors connected in series, and the two resistors are connected in parallel with the smoothing capacitor  22  to divide the direct-current voltage Vdc. The voltage detector  23  outputs, to the microcomputer  80 , a value of a voltage at a node between the two resistors. 
     (2-4) Current Detector  24   
     The current detector  24  is located between the smoothing capacitor  22  and the inverter circuit  25 , and is connected to the negative-side output terminal of the smoothing capacitor  22 . After startup of the motor  51 , the current detector  24  detects a motor current Im passing through the motor  51  as a sum of currents for the three phases. 
     The current detector  24  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  24  outputs the motor current thus detected to the microcomputer  80 . 
     (2-5) Intelligent Power Module  43   
     The intelligent power module  43  is a component obtained by incorporating, in one module, the inverter circuit  25  including switching elements connected in series and a control circuit  26  having a gate control function for driving the inverter circuit  25 . 
     (2-5-1) Inverter Circuit  25   
     The inverter circuit  25  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  51 , respectively, and are connected to the output side of the smoothing capacitor  22 . 
     As illustrated in  FIG.  1   , the inverter circuit  25  includes a plurality of insulated gate bipolar transistors (IGBTs) (hereinafter, simply referred to as transistors) Q 3   a , Q 3   b , Q 4   a , Q 4   b , Q 5   a , and Q 5   b  and a plurality of reflux diodes D 3   a , D 3   b , D 4   a , D 4   b , D 5   a , and D 5   b.    
     The transistors Q 3   a  and Q 3   b  are connected in series to constitute the upper and lower arms, and an output line extends from a node NU between the transistors Q 3   a  and Q 3   b  toward the U-phase drive coil Lu. The transistors Q 4   a  and Q 4   b  are connected in series to constitute the upper and lower arms, and an output line extends from a node NV between the transistors Q 4   a  and Q 4   b  toward the V-phase drive coil Lv. The transistors Q 5   a  and Q 5   b  are connected in series to constitute the upper and lower arms, and an output line extends from a node NW between the transistors Q 5   a  and Q 5   b  toward the W-phase drive coil Lw. 
     The diodes D 3   a  to D 5   b  are respectively connected in parallel with the transistors Q 3   a  to Q 5   b  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  25  receives the direct-current voltage Vdc from the smoothing capacitor  22  and turns on and off the transistors Q 3   a  to Q 5   b  at timings instructed by the control circuit  26  to generate drive voltages SU, SV, and SW for driving the motor  51 . The drive voltage SU is output to the drive coil Lu of the motor  51  via the node NU between the transistors Q 3   a  and Q 3   b . The drive voltage SV is output to the drive coil Lv of the motor  51  via the node NV between the transistors Q 4   a  and Q 4   b . The drive voltage SW is output to the drive coil Lw of the motor  51  via the node NW between the transistors Q 5   a  and Q 5   b.    
     In this embodiment, the inverter circuit  25  is a voltage source inverter. The inverter circuit  25  may alternatively be a current source inverter. 
     (2-5-2) Control Circuit  26   
     The control circuit  26  switches between the ON state and the OFF state of each of the transistors Q 3   a  to Q 5   b  of the inverter circuit  25 , based on a command voltage Vpwm from the microcomputer  80 . Specifically, the control circuit  26  generates gate control voltages Gu, Gx, Gv, Gy, Gw, and Gz to be respectively applied to the gates of the transistors Q 3   a , Q 3   b , Q 4   a , Q 4   b , Q 5   a , and Q 5   b  such that the inverter circuit  25  outputs, to the motor  51 , pulsed drive voltages SU, SV, and SW in a duty ratio determined by the microcomputer  80 . The gate control voltages Gu, Gx, Gv, Gy, Gw, and Gz thus generated are respectively applied to the gate terminals of the transistors Q 3   a , Q 3   b , Q 4   a , Q 4   b , Q 5   a , and Q 5   b.    
     (2-6) Microcomputer  80   
     The microcomputer  80  is connected to the voltage detector  23 , the current detector  24 , and the control circuit  26 . In this embodiment, the microcomputer  80  drives the motor  51  by a rotor position sensorless method. The microcomputer  80  may alternatively drive the motor  51  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  51  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  51 , a result of detection by the voltage detector  23  after the startup of the motor  51 , a result of detection by the current detector  24 , a predetermined mathematical formula model regarding the control of the motor  51 , and the like. Examples of the various parameters indicating the characteristics of the motor  51  may include, but not limited to, the winding resistance, inductance component, induced voltage, and number of poles of the used motor  51 . It should be noted that rotor position sensorless control is described in many patent literatures; therefore, refer to these patent literatures (e.g., JP 2013-017289 A) for the details thereof. 
     The microcomputer  80  also performs protection control of monitoring a value detected by the voltage detector  23  and turning off the transistors Q 3   a  to Q 5   b  when the value detected by the voltage detector  23  exceeds a predetermined threshold value. 
     (2-7) Bootstrap Circuit  48   
     The control circuit  26  appropriately inputs a gate potential to each of the upper arm-side transistors Q 3   a , Q 4   a , and Q 5   a  via a bootstrap circuit  48  disposed between each of the emitters of the transistors Q 3   a , Q 4   a , and Q 5   a  and a positive electrode of a drive power supply Vb connected to a terminal Vcc. 
     A first bootstrap circuit  48 A for a first control circuit  26 A includes a first capacitor  45 A, a first resistor  46 A, and a first diode  47 A. A second bootstrap circuit  48 B for a second control circuit  26 B includes a second capacitor  45 B, a second resistor  46 B, and a second diode  47 B. A third bootstrap circuit  48 C for a third control circuit  26 C includes a third capacitor  45 C, a third resistor  46 C, and a third diode  47 C. 
     In the following, a common description on the first bootstrap circuit  48 A, the second bootstrap circuit  48 B, and the third bootstrap circuit  48 C will be given using an expression of bootstrap circuits  48 . 
     Likewise, a common description on the first capacitor  45 A, the second capacitor  45 B, and the third capacitor  45 C will be given using an expression of capacitors  45 . 
     Likewise, a common description on the first resistor  46 A, the second resistor  46 B, and the third resistor  46 C will be given using an expression of resistors  46 . 
     Likewise, a common description on the first diode  47 A, the second diode  47 B, and the third diode  47 C will be given using an expression of diodes  47 . 
     It should be noted that the diodes  47  are omittable in a case where the intelligent power module  43  includes a diode for a bootstrap circuit. 
     (2-7-1) First Control Circuit  26 A and First Capacitor  45 A 
     As illustrated in  FIG.  2   , the first capacitor  45 A has a first end connected to a node between the emitter of the upper arm-side transistor Q 3   a  and the collector of the lower arm-side transistor Q 3   b . The first capacitor  45 A has a second end connected to the positive electrode of the drive power supply Vb via the first resistor  46 A and the first diode  47 A. 
     The first resistor  46 A is provided for restricting a charge current passing through the first capacitor  45 A. The first diode  47 A has a forward direction oriented from the positive electrode of the drive power supply Vb toward the first capacitor  45 A so as to prevent the first capacitor  45 A from being discharged via the first resistor  46 A. 
     The first control circuit  26 A includes an upper arm-side control circuit  26 Aa configured to receive a high potential from the first capacitor  45 A in order to control the ON/OFF state of the transistor Q 3   a . The first control circuit  26 A also includes a lower arm-side control circuit  26 Ab configured to control the ON/OFF state of the transistor Q 3   b . However, since the emitter of the transistor Q 3   b  is grounded, the lower arm-side control circuit  26 Ab is capable of controlling the ON/OFF state of the transistor Q 3   b , using a potential at the positive electrode of the drive power supply Vb connected to the terminal Vcc. 
     (2-7-2) Second Control Circuit  26 B and Second Capacitor  45 B 
     The second capacitor  45 B has a first end connected to a node between the emitter of the upper arm-side transistor Q 4   a  and the collector of the lower arm-side transistor Q 4   b . The second capacitor  45 B has a second end connected to the positive electrode of the drive power supply Vb via the second resistor  46 B and the second diode  47 B. 
     The second resistor  46 B is provided for restricting a charge current passing through the second capacitor  45 B. The second diode  47 B has a forward direction oriented from the positive electrode of the drive power supply Vb toward the second capacitor  45 B so as to prevent the second capacitor  45 B from being discharged via the second resistor  46 B. 
     The second control circuit  26 B includes an upper arm-side control circuit  26 Ba configured to receive a high potential from the second capacitor  45 B in order to control the ON/OFF state of the transistor Q 4   a . The second control circuit  26 B also includes a lower arm-side control circuit  26 Bb configured to control the ON/OFF state of the transistor Q 4   b . However, since the emitter of the transistor Q 4   b  is grounded, the lower arm-side control circuit  26 Bb is capable of controlling the ON/OFF state of the transistor Q 4   b , using a potential at the positive electrode of the drive power supply Vb connected to the terminal Vcc. 
     (2-7-3) Third Control Circuit  26 C and Third Capacitor  45 C 
     The third capacitor  45 C has a first end connected to a node between the emitter of the upper arm-side transistor Q 5   a  and the collector of the lower arm-side transistor Q 5   b . The third capacitor  45 C has a second end connected to the positive electrode of the drive power supply Vb via the third resistor  46 C and the third diode  47 C. 
     The third resistor  46 C is provided for restricting a charge current passing through the third capacitor  45 C. The third diode  47 C has a forward direction oriented from the positive electrode of the drive power supply Vb toward the third capacitor  45 C so as to prevent the third capacitor  45 C from being discharged via the third resistor  46 C. 
     The third control circuit  26 C includes an upper arm-side control circuit  26 Ca configured to receive a high potential from the third capacitor  45 C in order to control the ON/OFF state of the transistor Q 5   a . The third control circuit  26 C also includes a lower arm-side control circuit  26 Cb configured to control the ON/OFF state of the transistor Q 5   b . However, since the emitter of the transistor Q 5   b  is grounded, the lower arm-side control circuit  26 Cb is capable of controlling the ON/OFF state of the transistor Q 5   b , using a potential at the positive electrode of the drive power supply Vb connected to the terminal Vcc. 
     (3) Placement of Intelligent Power Module  43  and Capacitors  45   
       FIG.  3    is a plan view of the intelligent power module  43 . As seen in front view of  FIG.  3   , a package  43   a  incorporates therein the control circuit  26  located on a left side thereof and the inverter circuit  25  located on a right side thereof. 
     A first contact pin group P 1  and a second contact pin group P 2  protrude from a left end of the control circuit  26 . The first contact pin group P 1  receives a potential at each capacitor  45 . The second contact pin group P 2  receives a drive voltage and a control signal. 
     A third contact pin group P 3  protrudes from a right end of the inverter circuit  25 . The third contact pin group P 3  outputs power converted by the inverter circuit  25 . 
       FIG.  4    is a partial plan view of the printed wiring board  40  on which no components are mounted, and illustrates regions R 1  to R 3  where the capacitors  45  are respectively placed and a region R 4  where the intelligent power module  43  is placed. 
     In  FIG.  4   , the regions R 1  to R 3 , each of which is surrounded by a chain double-dashed line, are regions where the capacitors  45  are respectively mounted. Specifically, the first capacitor  45 A is mounted on the region R 1 , the second capacitor  45 B is mounted on the region R 2 , and the third capacitor  45 C is mounted on the region R 3 . 
     Also in  FIG.  4   , the region R 4 , which is surrounded by a chain double-dashed line, is a region where the intelligent power module  43  is mounted. The regions R 1  to R 3  are located in the region R 4 . 
     The region R 4  has a plurality of round hole lands located at its left end in front view. The contact pins protruding from the control circuit  26  of the intelligent power module  43  are respectively inserted in and soldered to the round hole lands. 
     The plurality of round hole lands include a first land group C 1  provided for the first contact pin group P 1  illustrated in  FIG.  3   . The round hole lands in the first land group C 1  are respectively connected to portions, where the electrodes of the capacitors  45  are soldered, via a conductive pattern. 
     The plurality of round hole lands also include a second land group C 2  provided for the second contact pin group P 2  illustrated in  FIG.  3   . The second land group C 2  is connected to the drive power supply Vb, the microcomputer  80 , and the like via the conductive pattern. 
     The region R 4  also has a plurality of oblong hole lands located at its right end in front view. The contact pins protruding from the inverter circuit  25  are respectively inserted in and soldered to the oblong hole lands. The plurality of oblong hole lands include a third land group C 3  provided for the third contact pin group P 3  illustrated in  FIG.  3   . The third land group C 3  is connected to the motor  51  via the conductive pattern. 
     The regions R 1  to R 3  where the capacitors  45  are respectively mounted are located near the first land group C 1  and are spaced away from the second land group C 2  and the third land group C 3  by a predetermined distance or more. In this embodiment, the predetermined distance is 3.2 mm or more in creepage distance and is 2 mm or more in spatial distance. This configuration therefore secures an insulation distance between the intelligent power module  43  and the capacitors  45  mounted on the printed wiring board  40 . 
       FIG.  5    is a side view of the capacitors  45  and the intelligent power module  43  each mounted on the printed wiring board  40 . As illustrated in  FIGS.  4  and  5   , since the regions R 1  to R 3  are located in the region R 4 , the capacitors  45  are mounted first, and the intelligent power module  43  is then mounted so as to be located above the capacitors  45 . The capacitors  45  are therefore located between a first surface  401  of the printed wiring board  40  and a first outer surface  431  of the intelligent power module  43 . 
     In the intelligent power module  43  illustrated in  FIG.  5   , the inverter circuit  25  is located on the right side in front view, and the control circuit  26  is located on the left side in front view. The inverter circuit  25  is larger in heating value than the control circuit  26 . In this embodiment, therefore, the capacitors  45  are mounted so as to be located below the control circuit  26  such that the capacitors  45  are less susceptible to an influence of heat generated from the inverter circuit  25 . 
     As illustrated in  FIG.  5   , a heat sink  49  is disposed on the intelligent power module  43  so as to encourage heat dissipation from the inverter circuit  25  heated to high temperatures. The intelligent power module  43  has the first outer surface  431  facing the first surface  401  of the printed wiring board  40 , and a second outer surface  432  farther from the printed wiring board  40  than the first outer surface  431  is. The heat sink  49  is disposed on the second outer surface  432 . 
     Therefore, the capacitors  45  are placed beside the first outer surface  431  and the heat sink  49  is placed beside the second outer surface  432  as seen from the first surface  401  of the printed wiring board  40 . 
     As a result, the intelligent power module  43  and the heat sink  49  are placed beside the first surface  401  of the printed wiring board  40 . This configuration thus achieves high integration of the components. 
     (4) Features 
     (4-1) 
     In the printed wiring board  40 , the regions R 1  to R 3  where the capacitors  45  are respectively mounted are located in the region R 4  where the intelligent power module  43  is mounted. Therefore, the capacitors  45  mounted on the printed wiring board  40  are placed between the printed wiring board  40  and the intelligent power module  43 . 
     In a case of a known printed wiring board, the capacitors  45  are mounted outside the region where the intelligent power module  43  is mounted. This configuration therefore requires not only an insulation distance between the intelligent power module  43  and each capacitor  45 , but also an insulation distance between each capacitor  45  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 Q 3   a , Q 4   a , and Q 5   a  is superimposed on the bootstrap circuits  48  to exert an adverse influence on another circuit or to cause malfunction of the intelligent power module  43 . 
     According to this embodiment, however, at least the areas of the regions R 1  to R 3  where the capacitors  45  are mounted and the area of the region corresponding to the insulation distance between the intelligent power module  43  and each capacitor  45  are reduced from the on-board space of the known printed wiring board. 
     This configuration therefore allows the capacitors  45  and the intelligent power module  43  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  48  to exert an adverse influence on another circuit or to cause malfunction of the intelligent power module  43 . 
     (4-2) 
     The intelligent power module  43  includes the inverter circuit  25  and the control circuit  26  configured to control the inverter circuit  25 . The inverter circuit  25  is larger in heating value than the control circuit  26 . The capacitors  45  are placed between the printed wiring board  40  and the control circuit  26 . The capacitors  45  are therefore less susceptible to a thermal influence of the inverter circuit  25 . 
     (4-3) 
     The rectifier  21  is mounted on the first surface  401  of the printed wiring board  40 . The rectifier  21  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  25 . As a result, the intelligent power module  43  and the rectifier  21  are placed beside the first surface  401  of the printed wiring board  40 . This configuration therefore achieves high density integration of the components. 
     (4-4) 
     The intelligent power module  43  has the first outer surface  431  and the second outer surface  432 . The capacitors  45  are placed beside the first outer surface  431 . The heat sink  49  is placed beside the second outer surface  432 . As a result, the intelligent power module  43  and the heat sink  49  are placed beside the first surface  401  of the printed wiring board  40 . This configuration thus achieves high integration of the components. 
     (4-5) 
     The printed wiring board  40  has the plurality of lands in and to which the contact pins of the intelligent power module  43  are inserted and soldered. The first contact pin group P 1 , that receives a potential at each capacitor  45  is soldered to the first land group C 1 . The second contact pin group P 2  that receives a potential at the drive power supply Vb and a control signal from the microcomputer  80  is soldered to the second land group C 2 . The capacitors  45  are placed beside the first contact pin group P 1  at the position away from the second contact pin group P 2  by the predetermined insulation distance. 
     (5) Others 
       FIGS.  6 A and  6 B  are side views of the intelligent power module  43  and its periphery in a case where the intelligent power module  43  and another power module  143  adjacent thereto share one heat sink  49 . 
     As illustrated in  FIG.  6 A , heretofore, a resin spacer Sp has been required for aligning the height of an intelligent power module  43  with the height of another power module  143  adjacent to the intelligent power module  43 . 
     According to this embodiment, as illustrated in  FIG.  6 B , each capacitor  45  placed between the printed wiring board  40  and the intelligent power module  43  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 spirit and scope of the present disclosure presently or hereafter claimed. 
     EXPLANATION OF REFERENCE 
     
         
         
           
               21 : rectifier (converter) 
               25 : inverter circuit 
               26 : control circuit 
               40 : printed wiring board 
               43 : intelligent power module 
               45 : capacitor (bootstrap capacitor) 
               45 A: first capacitor (bootstrap capacitor) 
               45 B: second capacitor (bootstrap capacitor) 
               45 C: third capacitor (bootstrap capacitor) 
               49 : heat sink 
               401 : first surface 
               431 : first outer surface 
               432 : second outer surface 
             P 1 : first contact pin group (first terminal) 
             P 2 : second contact pin group (second terminal) 
           
         
       
    
     CITATION LIST 
     Patent Literature 
     
         
         
           
             Patent Literature 1: WO2018-003827