Power converter

Abstract

To reduce radiation noise.SOLUTION: A power conversion device includes a base with conductivity, a first insulating layer existing on the base, a positive electrode conductor including a positive electrode existing on the first insulating layer, a negative electrode conductor including a negative electrode existing on the first insulating layer, an intermediate electrode existing on the first insulating layer, a power conversion circuit including an upper arm connected between the positive electrode and the intermediate electrode and a lower arm connected between the negative electrode and the intermediate electrode, a first capacitor including a first end connected to the positive electrode conductor and a second end connected to the negative electrode conductor; a second capacitor including a third end connected to the positive electrode conductor between the first end and the positive electrode and a fourth end connected to the negative electrode conductor between the second end and the negative electrode and having smaller capacity than the first capacitor; and a third capacitor including a fifth end connected to the negative electrode conductor and a sixth end connected to the base.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a power conversion device.

Background Art

[0002] Conventionally, there has been known a technique for suppressing radiation noise of a power conversion device based on switching operations of semiconductor elements such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors) (for example, Patent Document 1).

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] In a power conversion device, a stray capacitance may be formed between an intermediate conductor connected between the upper arm semiconductor element and the lower arm semiconductor element and a conductive base such as a heat sink. In this case, if a noise current generated by the switching operation of the semiconductor element leaks to the base via the stray capacitance, radiation noise may increase.

[0005] The present disclosure provides a power conversion device capable of reducing radiation noise.

Means for Solving the Problem

[0006] In a first aspect, the power conversion device includes: a conductive base; a first insulating layer located on the base; a positive electrode conductor including a positive electrode located on the first insulating layer; A negative electrode conductor including a negative electrode located on the first insulating layer, An intermediate electrode located on the first insulating layer, A power conversion circuit including an upper arm connected between the positive electrode and the intermediate electrode and a lower arm connected between the negative electrode and the intermediate electrode, A first capacitor having a first end connected to the positive conductor and a second end connected to the negative conductor, A second capacitor having a smaller capacitance than the first capacitor, having a third end connected to the positive electrode conductor between the first end and the positive electrode, and a fourth end connected to the negative electrode conductor between the second end and the negative electrode. The device comprises a third capacitor having a fifth terminal connected to the negative electrode conductor and a sixth terminal connected to the base. [Effects of the Invention]

[0007] According to the technology disclosed herein, radiated noise from power converters can be reduced. [Brief explanation of the drawing]

[0008] [Figure 1] This is a circuit diagram showing one example configuration of the power conversion device according to the first embodiment. [Figure 2] This is a cross-sectional view showing an example configuration of a module installed in a power converter. [Figure 3] This diagram illustrates the common-mode current ic1 generated in the module. [Figure 4] This diagram illustrates the common-mode current ic2 generated in the module. [Figure 5] This is an equivalent circuit diagram of the ground path. [Figure 6] This is an equivalent circuit diagram of the noise bypass path. [Figure 7] This is a perspective view showing a first example of a structure to which the module in the first embodiment is attached. [Figure 8] This is a cross-sectional view showing a first example of a structure to which the module in the first embodiment is attached. [Figure 9] It is a plan view showing a first example of a structure to which a module is attached in the first embodiment. [Figure 10] It is a plan view showing a first example of a structure in which the grounding capacitor Cn' can be adjusted afterwards. [Figure 11] It is a plan view showing a second example of a structure in which the grounding capacitor Cn' can be adjusted afterwards. [Figure 12] It is a plan view showing a third example of a structure in which the grounding capacitor Cn' can be adjusted afterwards. [Figure 13] It is a perspective view showing a second example of a structure to which a module is attached in the first embodiment. [Figure 14] It is a circuit diagram showing a configuration example of the power converter according to the second embodiment. [Figure 15] It is a perspective view showing a first example of a structure to which a module is attached in the second embodiment. [Figure 16] It is a cross-sectional view showing a first example of a structure to which a module is attached in the second embodiment. DETAILED DESCRIPTION OF EMBODIMENTS

[0009] Embodiments are described below with reference to the drawings. It should be noted that the term "connection" is not limited to physical connection, and may include the meaning of connection at the same potential. For example, the statement that object A is connected to object B is not limited to the case where object A is conductively connected to object B, and may include the case where object A is conductively connected to object B at the same potential via object C.

[0010] FIG. 1 is a circuit diagram showing a configuration example of the power converter according to the first embodiment. The power converter 101 shown in FIG. 1 converts three-phase AC power input from an unillustrated AC power supply via input terminals R, S, and T into three-phase AC power of different frequencies, and outputs the converted power to an unillustrated load via output terminals Uo, Vo, and Wo. The AC power supply is, for example, a commercial power supply that supplies three-phase AC power, but is not limited thereto. The load is, for example, a motor driven by the AC power supplied from the power converter 101, but is not limited thereto.

[0011] The power converter 101 comprises input terminals R, S, T, output terminals Uo, Vo, Wo, ground terminals E, Eo, a heat sink 1, a converter circuit 10, a positive electrode conductor 30, a negative electrode conductor 40, a smoothing capacitor Cdc, a line-to-line capacitor Cpn, a ground-referenced capacitor Cn', and a module 201. The ground-referenced capacitor Cn' is also referred to as a grounding capacitor Cn'.

[0012] A first grounding cable (not shown) is externally connected to the first ground terminal E. The first ground terminal E is grounded to an external earth via the first grounding cable.

[0013] The heat sink 1 is an example of a conductive base. The heat sink 1 is a member for dissipating heat generated by the power converter 101. Since the heat sink 1 is connected to the ground terminal E, it is grounded to an external earth via the ground terminal E and the grounding cable.

[0014] The converter circuit 10 is a rectifier circuit that converts three-phase alternating current input from the input terminals R, S, T into direct current. The converter circuit 10 is, for example, a diode bridge circuit that converts alternating-current power into direct-current power, but is not limited thereto. The converter circuit 10 outputs the converted (rectified) direct-current voltage between the positive electrode conductor 30 and the negative electrode conductor 40.

[0015] The smoothing capacitor Cdc is a capacitive element having a first end 51 connected to the positive electrode conductor 30, and a second end 52 connected to the negative electrode conductor 40. The line-to-line capacitor Cpn is a capacitive element having a third end 53 connected to the positive electrode conductor 30 between the first end 51 and the positive terminal P, and a fourth end 54 connected to the negative electrode conductor 40 between the second end 52 and the negative terminal N. Note that the third end 53 may be connected to the positive electrode conductor 30 between the positive terminal P and a positive electrode 5c1 described later, and the fourth end 54 may be connected to the negative electrode conductor 40 between the negative terminal N and a negative electrode 5c3 described later.

[0016] The inter-wire capacitor Cpn has a smaller capacitance than the smoothing capacitor Cdc. The smoothing capacitor Cdc reduces the ripple in the DC voltage between the positive conductor 30 and the negative conductor 40, and smooths the DC voltage. The inter-wire capacitor Cpn reduces high-frequency noise more effectively than the ripple in the DC voltage between the positive conductor 30 and the negative conductor 40.

[0017] Module 201 is a semiconductor module comprising a package housing an inverter circuit 20. The inverter circuit 20 is a power conversion circuit that converts direct current between a positive conductor 30 and a negative conductor 40 into three-phase alternating current. The inverter circuit 20 has six switching elements S1, S2, S3, S4, S5, and S6. The switching elements S1, S2, S3, S4, S5, and S6 are semiconductor elements such as IGBTs.

[0018] The connection point between switching element S1 and switching element S4 is connected to the intermediate terminal U of module 201. The connection points between switching element S2 and switching element S5 are connected to the intermediate terminal V of module 201. The connection points between switching element S3 and switching element S6 are connected to the intermediate terminal W of module 201. The intermediate terminal U of the U phase, the intermediate terminal V of the V phase, and the intermediate terminal W of the W phase are connected to the output terminals Uo of the U phase, Vo of the V phase, and Wo of the W phase, respectively.

[0019] The second grounding terminal Eo is connected to an external second grounding cable (not shown). The second grounding terminal Eo is connected via the second grounding cable to the enclosure of a load (not shown) to which three-phase AC power is supplied from output terminals Uo, Vo, and Wo. The enclosure of the load (not shown) is connected to the heatsink 1 via the second grounding terminal Eo and is grounded to earth via the heatsink 1 and the first grounding terminal E.

[0020] Figure 2 shows an example configuration of a module provided in a power converter. The module 201 shown in Figure 2 is a semiconductor device that houses an inverter circuit 20. Figure 2 illustrates a cross-section of a V-phase half-bridge circuit in the inverter circuit 20, in which the switching element S2 of the upper arm and the switching element S5 of the lower arm are connected in series.

[0021] A U-phase half-bridge circuit, in which the switching element S1 on the upper arm and the switching element S4 on the lower arm are connected in series, has the same configuration as a V-phase half-bridge circuit. A W-phase half-bridge circuit, in which the switching element S3 on the upper arm and the switching element S6 on the lower arm are connected in series, has the same configuration as a V-phase half-bridge circuit. Therefore, the explanation of the cross-sectional configuration of the U-phase and W-phase half-bridge circuits will be omitted by referring to the following explanation of the cross-sectional configuration of the V-phase half-bridge circuit.

[0022] As shown in Figure 2, module 201 is fixed to heatsink 1 in contact with thermal compound 2. Thermal compound 2 stabilizes heat dissipation from module 201 to heatsink 1.

[0023] Module 201 comprises a case 7, an insulating substrate 5, a positive terminal P, a negative terminal N, an intermediate terminal V, a switching element S2, a switching element S5, and wiring 15, 16. Intermediate terminals U and W are not shown in the illustration.

[0024] Case 7 is an enclosure that houses the insulating substrate 5, switching elements S1 to S6, and wiring 15 and 16. A conductive base plate 3 is provided at the bottom of Case 7. The insulating substrate 5 is placed on the base plate 3, and the switching elements S1 to S6 are placed on top of the insulating substrate 5. Specific examples of the base plate 3 include a copper (Cu) substrate with high heat dissipation and an aluminum silicon carbide (Al-SiC) composite substrate. Case 7 is, for example, a resin package that encloses the insulating substrate 5, switching elements S1 to S6, and wiring 15 and 16.

[0025] The insulating substrate 5 is a substrate on which switching elements S1 to S6 are mounted. Specific examples of insulating substrates 5 include DCB (Direct Copper Bonding) substrates and AMB (Active Metal Blazing) substrates. The insulating substrate 5 is fixed onto the base plate 3 by a bonding material 4 such as solder. The bonding material 4 is interposed between the base plate 3 and the insulating substrate 5.

[0026] The insulating substrate 5 includes an insulating layer 5a, a conductor layer 5b, and a wiring layer 5c. The insulating layer 5a is, for example, a ceramic plate. The conductor layer 5b is provided on the lower surface of the insulating layer 5a and is a metal foil formed of, for example, a conductive metal such as copper. The conductor layer 5b is in contact with the base plate 3 by a bonding material 4 such as solder. The wiring layer 5c is provided on the upper surface of the insulating layer 5a and is a conductor layer formed of, for example, a conductive metal such as copper. The wiring layer 5c includes a positive electrode 5c1, an intermediate electrode 5c2, and a negative electrode 5c3.

[0027] The switching element S2 is a semiconductor element incorporated into the module 201, and is a semiconductor chip having electrodes on both its front surface 12 and back surface 13.

[0028] The switching element S2 has a front surface 12 on which an emitter electrode 11e and a gate electrode 11g are formed, and a back surface 13 on which a collector electrode 11c is formed. The collector electrode 11c is an example of a first main electrode of the switching element S2. The emitter electrode 11e is an example of a second main electrode of the switching element S2. The gate electrode 11g is an example of a control electrode of the switching element S2. The switching element S2 is fixed on the insulating substrate 5 on its back surface 13 by joining the collector electrode 11c to the positive electrode 5c1 with a bonding material 6a such as solder. The emitter electrode 11e is connected to the intermediate electrode 5c2 via wiring 15.

[0029] The switching element S5 is a semiconductor element incorporated into module 201, and is a semiconductor chip having electrodes on both its front surface 8 and back surface 9.

[0030] The switching element S5 has a front surface 8 on which an emitter electrode 14e and a gate electrode 14g are formed, and a back surface 9 on which a collector electrode 14c is formed. The collector electrode 14c is an example of a first main electrode of the switching element S5. The emitter electrode 14e is an example of a second main electrode of the switching element S5. The gate electrode 14g is an example of a control electrode of the switching element S5. The switching element S5 is fixed on the insulating substrate 5 on its back surface 9 by joining the collector electrode 14c to the intermediate electrode 5c2 with a bonding material 6b such as solder. The emitter electrode 14e is connected to the negative electrode 5c3 via wiring 16.

[0031] Switching elements S1 to S6 are formed from Si semiconductor elements or SiC semiconductor elements. Wires 15 and 16 are not limited to bonding wires, but may also be in other forms such as conductive plates. The number of each of the wires 15 and 16 is one or more.

[0032] The positive terminal P, negative terminal N, and intermediate terminals U, V, and W are external terminals for connecting module 201 to the outside. Each of these external terminals is formed into a cylindrical or flat shape using a conductive metal such as copper or aluminum.

[0033] The positive terminal P is a first main terminal connected to the positive electrode 5c1, and is, for example, a lead terminal extending upward from the positive electrode 5c1. The positive terminal P is electrically connected to the collector electrode 11c of the switching element S1 via the positive electrode 5c1. The positive terminal P and the positive electrode 5c1 may be defined as part of the positive electrode conductor 30 (Figure 1).

[0034] The negative terminal N is a second main terminal connected to the negative electrode 5c3, and is, for example, a lead terminal extending upward from the negative electrode 5c3. The negative terminal N is electrically connected to the emitter electrode 14e of the switching element S4 via the negative electrode 5c3 and the wiring 16. The negative terminal N, the negative electrode 5c3, and the wiring 16 may be defined as part of the negative electrode conductor 40 (Figure 1).

[0035] The intermediate terminal V is a V-phase terminal connected to the intermediate electrode 5c2, and is, for example, a lead terminal extending upward from the intermediate electrode 5c2. The intermediate terminal V is electrically connected to the emitter electrode 11e of the switching element S2 via the intermediate electrode 5c2 and the wiring 15, and is also electrically connected to the collector electrode 14c of the switching element S5 via the intermediate electrode 5c2.

[0036] In Figure 2, the insulating layer 5a is a dielectric layer sandwiched between the conductive wiring layer 5c (positive electrode 5c1, intermediate electrode 5c2, and negative electrode 5c3) and the conductive base plate 3. Since the positive electrode 5c1 and intermediate electrode 5c2 are not DC-connected (conductively) to the base plate 3, stray capacitance is formed between the positive electrode 5c1 and the base plate 3, and between the intermediate electrode 5c2 and the base plate 3. Also, if the negative electrode 5c3 is not DC-connected (conductively) to the base plate 3, stray capacitance is formed between the negative electrode 5c3 and the base plate 3.

[0037] As shown in Figures 1 and 2, a stray capacitance Cp is formed between the positive electrode 5c1 and the base plate 3, a stray capacitance Cn is formed between the negative electrode 5c3 and the base plate 3, and a stray capacitance Co is formed between the intermediate electrode 5c2 and the base plate 3. Note that the stray capacitance Co is formed not only between the intermediate electrode 5c2 of the V phase and the base plate 3 (see Figure 1), but also between the intermediate electrode 5c2 of the U phase and the base plate 3, and between the intermediate electrode 5c2 of the W phase and the base plate 3 (not shown).

[0038] Furthermore, in Figure 2, the insulating thermal compound 2 is a dielectric layer sandwiched between the conductive base plate 3 and the conductive heat sink 1. If the base plate 3 is not DC-connected (conductively) to the same potential as the heat sink 1, a stray capacitance Cg (see Figure 1) is formed between the base plate 3 and the heat sink 1.

[0039] When the switching element S2, etc., switches, the stray capacitance Co formed between the intermediate electrode 5c2 and the base plate 3 is charged and discharged, generating a noise current based on the charging and discharging of the stray capacitance Co. This noise current can be a cause of radiated noise from the power converter 101. Next, the mechanism of radiated noise generation caused by the charging and discharging of stray capacitance Co and means for reducing that radiated noise will be described.

[0040] As switching elements such as S2 are activated, two types of common-mode currents, ic1 and ic2, are generated from module 201.

[0041] Figure 3 is a diagram illustrating the common-mode current ic1. When switching elements such as the switching element S2 occur, a noise current ino is generated, charging and discharging the stray capacitance Co formed between the intermediate electrode 5c2 and the base plate 3. The stray capacitances Cp and Cn function as pathways for recovering the noise current ino. However, some of the noise current ino that cannot be recovered by the stray capacitances Cp and Cn may leak into the heatsink 1 via the stray capacitance Cg. This leaked current flows out to the ground terminal E as the common-mode current ic1. A portion of this current becomes a radiation source current, and noise is radiated from the cable.

[0042] The power converter 101 of the first embodiment includes a ground capacitor Cn' connected between the negative electrode conductor 40 and the base plate 3. The ground capacitor Cn' is a capacitive element having a fifth end 55 connected to the negative electrode conductor 40 and a sixth end 56 connected to the base plate 3. The ground capacitor Cn' functions as a path for recovering noise current ino, so the amount of noise current ino recovered is increased. As a result, the common-mode current ic1 leaking to the heat sink 1 is reduced, and thus the radiated noise generated by the common-mode current ic1 is reduced.

[0043] Figure 4 is a diagram illustrating the common-mode current ic2. The common-mode current ic2 is generated by an imbalance between the stray capacitance Cp formed between the positive electrode 5c1 and the base plate 3, and the stray capacitance Cn formed between the negative electrode 5c3 and the base plate 3. The normal-mode current in1, generated in conjunction with the switching of the switching element S1, is converted into the common-mode current ic2 output from module 201 due to the imbalance between the stray capacitances Cp and Cn. Therefore, the amount of common-mode current ic2 generated can be reduced by reducing the normal-mode current in1 itself, or by reducing the mode conversion ratio by balancing the stray capacitances Cp and Cn. When the amount of common-mode current ic2 generated is reduced, the radiated noise generated by the common-mode current ic2 is reduced.

[0044] The power converter 101 of the first embodiment includes an inter-line capacitor Cpn between the vicinity of the positive terminal P and the vicinity of the negative terminal N. The inter-line capacitor Cpn has the effect of reducing the high-frequency components of the normal mode current in1. Therefore, the common mode current ic2 generated by the mode conversion from normal mode to common mode is reduced, and the radiated noise generated by the common mode current ic2 is reduced.

[0045] These two types of common-mode components originate from the same switching and occur simultaneously, but they are independent events. Therefore, even if one common-mode current is addressed, the other common-mode current remains, resulting in a limited reduction in radiated noise.

[0046] The power converter 101 of the first embodiment is equipped with a ground capacitor Cn' and a line-to-line capacitor Cpn, which allows countermeasures to be taken against both common-mode currents ic1 and ic2, thus providing a significant effect in reducing radiated noise.

[0047] For example, in the radiated noise band above 30 MHz, the combined impedance Zbp of the noise bypass path including the ground capacitor Cn' becomes smaller than the combined impedance Zgnd of the ground path including the heatsink 1. As a result, the amount of current flowing through the noise bypass path increases, reducing the common-mode currents ic1 and ic2 leaking into the ground path, and consequently reducing the radiated noise.

[0048] Figure 5 is an equivalent circuit diagram of the ground path. The ground path 61 is a path between the base plate 3 and the ground terminal E, passing through the stray capacitance Cg and the heat sink 1. The combined impedance Zgnd of the ground path 61 is: Zgnd = |1 / (jωCg) + Rgnd + jωLgnd| ...Formula 1 It is expressed as follows.

[0049] In Equation 1, j represents the imaginary unit, ω represents the frequency of the current flowing through the ground path 61, Rgnd represents the resistance component of the ground path 61, and Lgnd represents the inductance component of the ground path 61. In addition, in Equation 1, Cg may include capacitances other than the stray capacitance between the base plate 3 and the heat sink 1 (for example, the capacitance of a capacitor element inserted between the base plate 3 and the heat sink 1).

[0050] Figure 6 is an equivalent circuit diagram of the noise bypass path. The noise bypass path 62 is a path that passes through a parallel circuit of stray capacitances Cp, Cn and ground capacitor Cn' between the positive conductor 30 or the negative conductor 40 and the base plate 3. The space between the positive conductor 30 and the negative conductor 40 can be considered a short circuit at high frequencies due to the inter-line capacitor Cpn. Therefore, the combined impedance Zbp of the noise bypass path 62 is: Zbp = |1 / (jωCn'+jωCp+jωCn)| ...Formula 2 It is expressed as follows.

[0051] In Equation 2, j represents the imaginary unit, ω represents the frequency of the current flowing through the noise bypass path 62, and Cn' represents the capacitance of the ground capacitor Cn'. The parasitic inductance and resistive impedance components of the ground capacitor Cn' are omitted but may be considered. In Equation 2, Cp may include capacitances other than the stray capacitance between the base plate 3 and the positive conductor 30 (for example, the capacitance of a capacitor element inserted between the base plate 3 and the positive conductor 30).

[0052] Therefore, using equations 1 and 2, Zbp <Zgnd In other words, |1 / (jωCn'+jωCp+jωCn)|<|1 / (jωCg)+Rgnd+jωLgnd| ...Formula 3 By adjusting the capacitance of the ground capacitor Cn' to a value that satisfies this condition, radiated noise is reduced.

[0053] For example, by adjusting the capacitance of the ground capacitor Cn' to between 100pF and 1000pF, the common-mode currents ic1 and ic2 are reduced, and radiated noise is reduced.

[0054] As described above, the power converter 101 of the first embodiment includes a thermal compound 2 located on a heat sink 1, a base plate 3 located on the thermal compound 2, and an insulating layer 5a located on the base plate 3, as shown in Figure 2. The power converter 101 also includes a positive electrode conductor 30 including a positive electrode 5c1 located on the insulating layer 5a, a negative electrode conductor 40 including a negative electrode 5c3 located on the insulating layer 5a, an intermediate electrode 5c2 located on the insulating layer 5a, and an inverter circuit 20 including switching elements S2 and S5. Furthermore, the power converter 101 includes a smoothing capacitor Cdc, a line-to-line capacitor Cpn, and a ground capacitor Cn'. Therefore, since the power converter 101 includes a ground capacitor Cn' and a line-to-line capacitor Cpn, both common-mode currents ic1 and ic2 can be reduced, and radiated noise caused by the common-mode currents ic1 and ic2 can be reduced.

[0055] In the first embodiment, the smoothing capacitor Cdc is an example of a first capacitor. The line-to-line capacitor Cpn is an example of a second capacitor. The ground capacitor Cn' is an example of a third capacitor. The heat sink 1 is an example of a conductive first base. The base plate 3 is an example of a conductive second base to which the sixth end of the third capacitor is connected. The insulating layer 5a is an example of a first insulating layer located on a conductive base. The thermal compound 2 is an example of a second insulating layer located between the first base and the second base.

[0056] Figure 7 is a perspective view showing a first example of a structure to which the module in the first embodiment is attached. Figure 8 is a cross-sectional view showing a first example of a structure to which the module in the first embodiment is attached. The structures shown in Figures 7 and 8 are examples of a type in which the base plate 3 is not connected DC-wise (conductively) to the heat sink 1 so that it is at the same potential.

[0057] Module 201 is fixed to heatsink 1 by bolts 22. When viewed from above, the base plate 3 protrudes from the module 201 package in a direction parallel to the substrate 23. The protruding portion of the base plate 3 has a structure (for example, a non-through screw hole 3a) that can be electrically connected to the lower end of the stud 21.

[0058] Figure 9 is a plan view showing a first example of a structure to which the module is mounted in the first embodiment. The power converter 101 has a substrate 23. The substrate 23 has a positive terminal P, a negative terminal N, and intermediate terminals U, V, W connected in a conductive manner. The substrate 23 has a positive electrode pattern 31 to which the positive electrode terminal P is connected in a conductive manner, a negative electrode pattern 41 to which the negative electrode terminal N is connected in a conductive manner, and a grounding pattern 42 to which the upper end of the stud 21 is connected in a conductive manner. The positive electrode pattern 31 formed on the substrate 23 may be defined as part of the positive electrode conductor 30. The negative electrode pattern 41 formed on the substrate 23 may be defined as part of the negative electrode conductor 40.

[0059] In this example, the ground capacitor Cn' is mounted on the circuit board 23. The fifth terminal 55 of the ground capacitor Cn' is connected to the negative electrode pattern 41, and the sixth terminal 56 of the ground capacitor Cn' is connected to the ground pattern 42. The ground pattern 42 is connected to the base plate 3 via the stud 21. Therefore, the sixth terminal 56 of the ground capacitor Cn' is connected to the base plate 3. By mounting the ground capacitor Cn' on the circuit board 23, it becomes easy to adjust the capacitance of the ground capacitor Cn' according to the degree of radiated noise generated by the common-mode current ic1.

[0060] The inter-line capacitor Cpn may also be mounted on the circuit board 23. The third terminal 53 of the inter-line capacitor Cpn is connected to the positive terminal pattern 31, and the fourth terminal 54 of the inter-line capacitor Cpn is connected to the negative terminal pattern 41. Mounting the inter-line capacitor Cpn on the circuit board 23 makes it easy to adjust the capacitance of the inter-line capacitor Cpn according to the degree of radiated noise generated by the common-mode current ic2. In the example shown in Figure 9, the ground capacitor Cn' and the inter-line capacitor Cpn are arranged such that the shortest distance between the fifth terminal 55 of the ground capacitor Cn' and the negative terminal N is longer than the shortest distance between the fourth terminal 54 of the inter-line capacitor Cpn and the negative terminal N. However, the ground capacitor Cn' and the line-to-line capacitor Cpn may be arranged such that the shortest distance between the fifth terminal 55 and the negative terminal N is equal to the shortest distance between the fourth terminal 54 and the negative terminal N, or the shortest distance between the fifth terminal 55 and the negative terminal N is shorter than the shortest distance between the fourth terminal 54 and the negative terminal N. By arranging the ground capacitor Cn' and the line-to-line capacitor Cpn such that the shortest distance between the fifth terminal 55 and the negative terminal N is shorter than the shortest distance between the fourth terminal 54 and the negative terminal N, the effect of reducing radiated noise caused by common-mode current is enhanced.

[0061] The smoothing capacitor Cdc may also be mounted on the substrate 23. The first terminal 51 of the smoothing capacitor Cdc is connected to the positive electrode pattern 31, and the second terminal 52 of the smoothing capacitor Cdc is connected to the negative electrode pattern 41. Mounting the smoothing capacitor Cdc on the substrate 23 makes it easy to adjust the capacitance of the smoothing capacitor Cdc according to the magnitude of the DC voltage ripple between the positive electrode pattern 31 and the negative electrode pattern 41.

[0062] Figure 10 is a plan view showing a first example of a structure in which the grounding capacitor Cn' can be adjusted later. The negative electrode pattern 41 and the grounding pattern 42 lands are pre-formed widely on the substrate 23 so that grounding capacitors of various sizes can be mounted. This makes it easy to adjust the capacitance of the grounding capacitor Cn' afterwards.

[0063] Figure 11 is a plan view showing a second example of a structure in which the grounding capacitor Cn' can be adjusted afterwards. One or more island-shaped patterns spaced apart from the negative electrode pattern 41 and one or more island-shaped patterns spaced apart from the grounding pattern 42 are pre-formed on the substrate 23 so that multiple grounding capacitors Cn' can be mounted in parallel connection. When used in parallel connection, jumpers 24 are installed between the island-shaped patterns, and when not used in parallel connection, the jumpers 24 are removed.

[0064] Figure 12 is a plan view showing a third example of a structure in which the grounding capacitor Cn' can be adjusted later. One or more island-shaped patterns spaced apart from the negative electrode pattern 41 and one or more island-shaped patterns spaced apart from the grounding pattern 42 are pre-formed on the substrate 23 so that multiple grounding capacitors Cn' can be mounted in series. By changing the way the jumper 24 is connected, it is possible to select whether or not to use them in series connection.

[0065] Figure 13 is a perspective view showing a second example of the structure to which the module in the first embodiment is attached. The structure shown in Figure 13 is an example of a type in which the base plate 3 is not connected DC-wise (conductively) to the heat sink 1 so that it is at the same potential.

[0066] Module 201 is fixed to the heatsink 1 by bolts 22. When viewed in plan, the base plate 3 protrudes from the module 201 package in a direction parallel to the substrate 23. The protruding portion of the base plate 3 has a structure (e.g., a conductive plate 3b) that can be electrically connected to the sixth terminal 56 of the ground capacitor Cn'. The fifth terminal 55 of the ground capacitor Cn' is connected to the negative terminal N by soldering or crimping. The negative terminal N may have a structure that can be electrically connected to the fifth terminal 55 of the ground capacitor Cn'. The inter-line capacitor Cpn may be built into module 201.

[0067] Figure 14 is a circuit diagram showing an example configuration of the power converter of the second embodiment. The power converter 102 of the second embodiment differs from the power converter 101 of the first embodiment in that the base plate 3 is connected DC-wise (conductively) so that it is at the same potential as the heat sink 1. In the second embodiment, a description of the same configuration, operation, and effects as in the first embodiment will be omitted by referring to the above description.

[0068] The power converter 102 of the second embodiment has the same structure as the power converter 101 of the first embodiment, as shown in Figure 2. Therefore, a stray capacitance Cp is formed between the positive electrode 5c1 and the base plate 3, a stray capacitance Cn is formed between the negative electrode 5c3 and the base plate 3, and a stray capacitance Co is formed between the intermediate electrode 5c2 and the base plate 3. However, in the second embodiment, the base plate 3 is connected DC-wise (conductively) to the same potential as the heat sink 1, so no stray capacitance Cg is formed between the base plate 3 and the heat sink 1.

[0069] Similar to the first embodiment, the power converter 102 of the second embodiment includes a ground capacitor Cn' connected between the negative electrode conductor 40 and the base plate 3. The ground capacitor Cn' functions as a path for recovering noise current ino via the stray capacitance Co, thus increasing the amount of noise current ino recovered. As a result, the common-mode current ic1 leaking to the heat sink 1 is reduced, and the radiated noise generated by the common-mode current ic1 is reduced.

[0070] Similar to the first embodiment, the power converter 102 of the second embodiment includes an inter-line capacitor Cpn between the vicinity of the positive terminal P and the vicinity of the negative terminal N. The inter-line capacitor Cpn reduces the common-mode current ic2 generated by the mode conversion from normal mode to common mode, and reduces the radiated noise generated by the common-mode current ic2.

[0071] The power converter 102 of the second embodiment includes a ground capacitor Cn' and a line capacitor Cpn, which reduces both common-mode currents ic1 and ic2, and thus reduces radiated noise caused by the common-mode currents ic1 and ic2.

[0072] In the second embodiment, the smoothing capacitor Cdc is an example of a first capacitor. The line-to-line capacitor Cpn is an example of a second capacitor. The ground capacitor Cn' is an example of a third capacitor. The heat sink 1 is an example of a conductive first base to which the sixth terminal 56 of the third capacitor is connected. The thermal compound 2 is an example of a second insulating layer located within the first base. The base plate 3 is an example of a conductive second base that is conductively connected to the first base and located on the second insulating layer.

[0073] Figure 15 is a perspective view showing a first example of a structure to which the module in the second embodiment is attached. Figure 16 is a cross-sectional view showing a first example of a structure to which the module in the second embodiment is attached. The structures shown in Figures 15 and 16 are examples of a type in which the base plate 3 is connected DC-wise (conductively) so that it is at the same potential as the heat sink 1.

[0074] Module 201 is fixed to heatsink 1 by bolts 22. Heatsink 1 has a structure (for example, a non-through screw hole 1a) that can be electrically connected to the lower end of the stud 21. The substrate 23 may be the same as the configuration shown in Figure 9.

[0075] As described above, embodiments have been explained, but these embodiments are presented as examples only, and the present invention is not limited by these embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, and modifications are possible without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0076] 1 Heatsink 2 Thermal Compound 3 Base plate 3a Screw hole 4,6a,6b Bonding material 5. Insulating substrate 5c1 positive electrode 5c2 intermediate pole 5c3 negative electrode 7 cases 8,12 surface 9,13 Back side 10 Converter Circuit 11,14 electrode 15,16 Wiring 20 Inverter Circuit 21 Stud 22 volts 23 circuit boards 24 Jumper 30 Positive conductor 31 Positive electrode pattern 40 Negative electrode conductor 41 Negative electrode pattern 42 Grounding Patterns 51 1st end 52 2nd end 53 3rd end 54 4th end 55 5th end 56 6th end 61 Ground Path 62 Noise Bypass Path 101 Power converter 201 Modules

Claims

1. A conductive base, A first insulating layer located on the base, A positive electrode conductor including a positive electrode located on the first insulating layer, A negative electrode conductor including a negative electrode located on the first insulating layer, An intermediate electrode located on the first insulating layer, A power conversion circuit including an upper arm connected between the positive electrode and the intermediate electrode and a lower arm connected between the negative electrode and the intermediate electrode, A first capacitor having a first end connected to the positive electrode conductor and a second end connected to the negative electrode conductor, A second capacitor having a smaller capacitance than the first capacitor, having a third end connected to the positive electrode conductor between the first end and the positive electrode, and a fourth end connected to the negative electrode conductor between the second end and the negative electrode. A power conversion device comprising a third capacitor having a fifth terminal connected to the negative electrode conductor and a sixth terminal connected to the base.

2. The negative electrode conductor includes a negative electrode terminal connected to the negative electrode. The power conversion device according to claim 1, wherein the second, fourth, and fifth ends are connected to the negative terminal.

3. Equipped with a circuit board, The negative electrode conductor includes a negative electrode pattern formed on the substrate. The power converter according to claim 2, wherein the second terminal, the fourth terminal, the fifth terminal and the negative terminal are connected to the negative electrode pattern.

4. The third capacitor is mounted on the substrate, as described in claim 3 of the power conversion device.

5. The power conversion device according to claim 4, wherein the second capacitor is mounted on the substrate.

6. The power conversion device according to any one of claims 1 to 5, wherein the base includes a conductive first base, a conductive second base to which the sixth end is connected, and a second insulating layer located between the first base and the second base.

7. When the capacitance between the first base and the second base is Cg, the capacitance between the positive electrode and the second base is Cp, the stray capacitance between the negative electrode and the second base is Cn, and the capacitance of the third capacitor is Cn', The power conversion device according to claim 6, wherein the combined impedance of the path through the first base and capacitance Cg is greater than the combined impedance of the parallel circuit of Cp, Cn, and Cn'.

8. The power conversion device according to any one of claims 1 to 5, wherein the base includes a conductive first base to which the sixth end is connected, a second insulating layer located on the first base, and a conductive second base electrically connected to the first base and located on the second insulating layer.

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