JP2012199466A - Power module - Google Patents

Abstract

A power module capable of reducing noise generated by resonance between a parasitic capacitance of a semiconductor element and an inductance of a wire connecting the semiconductor elements.
A plurality of semiconductor elements (11, 12), wires (36, 37, 39) connecting the plurality of semiconductor elements (11, 12), a loop coil (52), and a magnetic body (53). A noise absorber (51), the noise absorber (51) is disposed in the vicinity of at least one of the plurality of semiconductor elements (11, 12), and the loop surface of the loop coil (52) Of the wires connecting the semiconductor elements (11, 12), the wires are arranged along at least one of the wires (36, 37) that generate noise.
[Selection] Figure 2

Description

  The present invention relates to electromagnetic compatibility of a power module (power converter).

  In order to reduce the radiation noise from the power module, there is a technology that surrounds the electrode drawn from the semiconductor element with an individual noise absorber and embeds the noise absorber in a gelatinous sealing material for protecting the semiconductor element It is disclosed (see Patent Document 1).

JP 2004-207432 A

  Incidentally, in a configuration in which a plurality of semiconductor elements are connected in a power module, noise is generated due to resonance between the parasitic capacitance of the semiconductor elements and the inductance of the wire connecting the semiconductor elements.

  However, the technique of Patent Document 1 has a problem in that there is no effect of reducing noise against this noise.

  Therefore, an object of the present invention is to provide a power module that can reduce noise generated by resonance between the parasitic capacitance of a semiconductor element and the inductance of a wire connecting the semiconductor elements.

  The power module of the present invention includes a plurality of semiconductor elements, wires connecting the plurality of semiconductor elements, and a noise absorber made of a loop coil and a magnetic material. The noise absorber is disposed in the vicinity of at least one of the plurality of semiconductor elements, and the loop surface of the loop coil is disposed on at least one of the wires generating noise among the wires connecting the plurality of semiconductor elements. It is arranged along.

  According to the present invention, the loop coil is magnetically coupled to a resonance circuit (a circuit including a parasitic capacitance of a plurality of semiconductor elements and a wire inductance connecting the semiconductor elements) as a noise source, and a resistance component of the magnetic body. The noise component can be attenuated.

It is a circuit diagram of the three-phase inverter for motor drive of a 1st embodiment of the present invention. It is a schematic sectional drawing in the mounting state of a part of one power module of 1st Embodiment. It is a schematic plan view which shows element arrangement | positioning in the mounting state of a part of one power module of 1st Embodiment. It is a circuit operation | movement figure of one power module. It is a timing chart for demonstrating generation | occurrence | production of the noise inside a power module. It is an equivalent circuit diagram of the resonance circuit used as a noise source. It is a schematic sectional drawing in the mounting state of a part of one power module of 2nd Embodiment. It is a schematic plan view which shows element arrangement | positioning in the mounting state of a part of one power module of 2nd Embodiment. It is a schematic sectional drawing in the mounting state of a part of one power module of 3rd Embodiment. It is a schematic plan view which shows element arrangement | positioning in the mounting state of a part of one power module of 3rd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a circuit diagram of a three-phase inverter 14 for driving a motor provided with a power module 10 according to the first embodiment of the present invention. As shown in FIG. 1, one power module 10 has an IGBT (Insuated Gate Bipolar Transistor) 11 as a switching element and a free-wheeling diode 12 as a rectifying element, and each free-wheeling diode 12 is antiparallel to each IGBT 11. It is connected. This power module 10 is for one phase (one arm) of a three-phase inverter 14 for driving the AC motor 13. The electric power of the DC power supply 15 is converted by the smoothing capacitor 16 and the three power modules 10 into three-phase AC power for driving the automotive AC motor 13.

  Specifically, the inverter includes an external bus bar (output side) 21 that connects the AC motor 13 and the inverter 14, an external bus bar (P side) 22 that connects the DC power supply 15 and the inverter 14, and an external bus bar (N side) 23. I have. One power module 10 includes an output electrode 24 connected to an external bus bar (output side) 21, a P-type electrode 25 connected to an external bus bar (P side) 22, and an N-type electrode connected to an external bus bar (N side) 23. 26.

  FIG. 2 is a schematic sectional view of a part of one power module 10 in a mounted state, and FIG. 3 is a schematic plan view showing an element arrangement in a part of the mounted state of one power module 10. Although three power modules 10 are shown in FIG. 1, the configuration of each power module 10 is the same for all three. In FIG. 2, it is assumed that the upper side is the vertical upper side. Therefore, the flat power module 10 as a whole is placed in a horizontal position. 3 shows a state where the sealing material 40 and the resin lid 41 shown in FIG. 2 are removed.

  In the circuit diagram of FIG. 1, for a single power module 10, a plurality of semiconductor elements (hereinafter referred to as “multiple semiconductor elements”) in which an IGBT 11 and a free-wheeling diode 12 are connected in antiparallel are two vertically. Are lined up. On the other hand, in the mounting state shown in FIG. 3, three IGBTs 11 a to 11 c, three free-wheeling diodes 12 a to 12 c, and one of the two upper and lower semiconductor elements shown in FIG. 1 (part of one power module 10) Is used. That is, in FIG. 3, three semiconductor elements are arranged in the vertical direction at substantially equal intervals, and these three semiconductor elements are electrically connected in parallel. Although not shown in the figure, three IGBTs and three free-wheeling diodes are used for the other of the upper and lower two semiconductor elements shown in FIG. Thus, the reason why three semiconductor elements are connected in parallel is to increase the current capacity of the power module 10. The number of semiconductors connected in parallel is not limited to three.

  In the mounted state shown in FIG. 2, only one IGBT 11 and one free wheeling diode 12 are visible. In the case of “multiple semiconductor elements” in FIG. 2, among the three semiconductor elements 11a and 12a located in the upper stage of FIG. 3, the multiple semiconductor elements 11b and 12b located in the middle stage, and the multiple semiconductor elements 11c and 12c located in the lower stage. Any one of them. The same applies to the other members (36, 37, 38, 39) in FIG. 2 and the noise absorber 51 described later.

  It demonstrates from FIG. One power module 10 includes a base plate 31, a ceramic substrate 32 having an output electrode, a P-type electrode and an N-type electrode, a resin case 33, a plurality of semiconductor elements 11, 12 arranged (mounted) vertically above the ceramic substrate 32, etc. Consists of A cooler (not shown) is also provided for the purpose of cooling the semiconductor elements 11 and 12.

  The collector terminal of the IGBT 11 and the cathode terminal of the free-wheeling diode 12 are joined to the output electrode of the ceramic substrate 32 by a solder (not shown) so that the lower end of the vertical terminal is electrically conductive. The emitter terminal of the IGBT 11 is joined to the N-type electrode of the ceramic substrate 32 by a bonding wire 36. The anode terminal of the reflux diode 12 is also bonded to the N-type electrode of the ceramic substrate 32 by the bonding wire 37 so as to be electrically conductive. Further, an external terminal 38 is fixed to a resin case 33 erected on the outer periphery of the base plate 31, and the external terminal 38 and the base terminal of the IGBT 11 are connected by a bonding wire 39. Hereinafter, the bonding wire 36 is also referred to as an “emitter connection wire”. The bonding wire 37 is also referred to as an “anode connection wire”.

  The inside of the resin case 33 is sealed with a sealing material 40 that is a gel-like resin so that the surfaces of the plurality of semiconductor elements 11 and 12 do not oxidize or corrode when exposed to moisture or oxygen in the air. A vertical upper portion is covered with 41.

  In this way, the power module 10 is formed by arranging the plurality of semiconductor elements 11 and 12 constituting the main circuit of the inverter 14, wiring the connection terminals with the bonding wires 36, 37, and 39 and sealing them with a resin material or the like. is there. An inverter 14 is configured by combining a plurality of power modules 10. The current flowing through the external bus bar (output side) 21 is switched by the IGBT 11 to control the current output from the inverter 14.

  In this case, a circuit that resonates with the capacitance (parasitic capacitance) parasitic to the plurality of semiconductor elements 11 and 12 and the inductance of the bonding wires 36 and 37 that connect the plurality of semiconductor elements 11 and 12 (hereinafter, this circuit network is referred to as “resonance”). Circuit "). For this reason, when the IGBT 11 is switched, noise is generated due to resonance between the parasitic capacitances of the plurality of semiconductor elements 11 and 12 and the inductances of the bonding wires 36 and 37 and is emitted to the surroundings. When radiation noise is generated, there is a concern that when the inverter 14 configured by combining the power modules 10 is used for driving a motor of an electric vehicle or a hybrid vehicle, it adversely affects an electronic device (radio in an in-vehicle environment). The

  In order to cope with this problem, the electrodes drawn from the semiconductor element are surrounded by individual noise absorbers, and the noise absorbers are embedded in a gelatinous sealing material for protecting the semiconductor element elements, thereby reducing radiation noise. There are conventional techniques to reduce.

  However, even when the conventional technique is applied to the power module 10 of the present embodiment, the parasitic capacitance between the plurality of semiconductor elements 11 and 12 and the inductance of the bonding wires 36 and 37 connecting the plurality of semiconductor elements 11 and 12 are reduced. There is no effect of reducing noise generated by resonance. This is because, in the case of the prior art, even if the electrodes drawn from the plurality of semiconductor elements 11 and 12 are surrounded by individual noise absorbers, the bonding wires 36 and 37 connecting the plurality of semiconductor elements 11 and 12 pass through the electrodes. This is because there is no noise reduction effect.

  Therefore, in the first embodiment of the present invention, the noise absorber 51 is composed of a loop coil 52 and a ferrite bead 53 (magnetic material). The noise absorber 51 is disposed in the vicinity of at least one of the IGBT 11 and the free wheeling diode 12. Further, the loop surface of the loop coil 52 is disposed along at least one of the bonding wires 36 and 37 that generate noise among the wires connecting the plurality of semiconductor elements 11 and 12.

  This will be specifically described. Of the bonding wires connecting the plurality of semiconductor elements 11 and 12, there are two bonding wires that generate noise, namely, an emitter connection wire 36 of the IGBT 11 and an anode connection wire 37 of the reflux diode 12. Since each of the wires 36 and 37 has five wires, and a convex curve is drawn upward as shown in FIG. 2, noise is generated from each of the five emitter connection wires 36 and anode connection wires 37. Radiated to the surroundings.

  In FIG. 3, since three semiconductor devices are connected in parallel, noise is generated from the three emitter connection wires 36a, 36b, 36c and the three anode connection wires 37a, 37b, 37c along with the switching operation of the IGBT 11. Is emitted. Therefore, the first noise absorber 51a is disposed on the ceramic substrate 32 between the emitter connection wire 36a of the first IGBT 11a located in the upper part in FIG. 3 and the emitter connection wire 36b of the second IGBT 11b located in the center. Deploy. In FIG. 3, the second noise absorber 51 b is arranged on the ceramic substrate 32 between the emitter connection wire 36 b of the second IGBT 11 b and the emitter connection wire 36 c of the third IGBT 11 c located below. The configurations of the first and second noise absorbers 51a and 51b are the same. When three semiconductor elements 11 and 12 are arranged so as to be adjacent to each other as described above, a noise absorber is arranged between two adjacent IGBTs (emitter connection wires), thereby connecting adjacent emitters. Both noises generated from the wires can be efficiently attenuated.

  Next, the loop surface of the loop coil 52 is arranged along the emitter connection wire 36 of the IGBT 11. Here, the “loop coil” means that the conducting wire is not spirally wound a plurality of times, but the conducting wire has a single noose shape. The “loop surface” of the loop coil refers to a surface formed by one noose wire. Although the loop surface here is formed in a circular shape, the shape of the loop surface is not limited to a circular shape.

  “Along the loop surface along the emitter connection wire” means that the shortest distance between one end of the loop surface (for example, the right end in FIG. 2) and the emitter connection wire and the other end of the loop surface (for example, the left end in FIG. 2). ) And the shortest distance between the emitter connecting wires. For this reason, in FIG. 3, the loop surfaces of the loop coils 52a and 52b are in a positional relationship parallel to the adjacent emitter connection wires 36a to 36c.

  The loop coil 52 is provided for the purpose of urging magnetic coupling to a resonance circuit serving as a noise source, short-circuiting both ends of the ferrite bead 53, and converting the noise component into heat by the resistance component of the ferrite bead 53 to attenuate it. ing. Note that both ends (left and right ends in FIG. 2) of the ferrite bead 53 have input / output terminals (not shown).

  The ferrite bead 53 as a magnetic body aims at aggregating the magnetic field generated from the noise source, and in addition, for the purpose of attenuating the noise component magnetically coupled by the loop coil 12 by its own resistance. Provided. By selecting (setting) the one whose resistance component increases in the frequency band of the radiation noise to be attenuated, the noise in that frequency band is attenuated. For example, if the frequency band of radiation noise to be attenuated is in the vicinity of 100 MHz, ferrite beads whose loss (resistance component) increases in the vicinity of 100 MHz are selected. In the first embodiment, ferrite beads are employed as the magnetic material, but any magnetic material having characteristics similar to the ferrite beads may be used. Although the shape of the ferrite bead is a quadrangular prism, it is not limited to a quadrangular prism.

  The plurality of semiconductor elements 11 and 12, the emitter connection wire 36, the anode connection wire 37, and the like are portions to which a high voltage exceeding 40V is applied, that is, a strong electric portion. For this reason, the noise absorber 51 is disposed after securing a necessary insulation distance from the strong electrical site, and is mounted after being treated with a coating having a necessary withstand voltage. Here, the required insulation distance from the strong electrical site is determined in advance according to the required specifications. Further, the required withstand voltage required for the noise absorber 51 is determined in advance according to the required specifications.

  Inverter circuit operation in which noise is generated in one power module 10 and its timing will be described with reference to FIGS. FIG. 4 is a circuit operation diagram in which one power module 10 (one arm) is extracted from the inverter 14. In the power module 10, a P-side reflux diode 12A is connected to the P-side IGBT 11A, and an N-side reflux diode 12B is connected to the N-side IGBT 11B in antiparallel. An inductive load such as a motor is connected to the output terminal 55. The smoothing capacitor 16 is connected between the P terminal 56 and the N terminal 57, and the voltage between the P terminal 56 and the N terminal 57 is, for example, a constant value Vdc.

  As shown in FIG. 5, the timing of t1 from the state in which the current I circulates in the P-side return diode 12A during the off period (the short circuit prevention period of the upper and lower IGBTs 11A and 11B) of both the upper and lower IGBTs 11A and 11B. Thus, the N-side IGBT 11B is switched from OFF to ON. After the current If flowing through the P-side return diode 12A becomes negative from positive at the timing t2 slightly delayed from the switching timing of t1, the current returns to zero at the timing t3. That is, radiation noise is generated at the timing when the recovery current surrounded by a dotted line in FIG. 5 is generated.

  FIG. 6 shows an equivalent circuit of a resonance circuit serving as a noise source at this time. The noise source is a series of the inductance component L of the bonding wires 36 and 37 connecting the IGBT 11A and the freewheeling diode 12A, the parasitic capacitance C between the collector and emitter of the IGBT11, and the voltage change (voltage source) V of the P-side freewheeling diode 12A. Represented by a bond. Since the noise absorber 51 is magnetically coupled to a resonance circuit serving as a noise source and a resistance component is inserted in series, the noise absorber 51 functions to attenuate vibrations to the resonance circuit.

  In the first embodiment, the noise absorber 51 is disposed in the vicinity of the IGBT 11 and the loop surface of the loop coil 52 is disposed along the emitter connection wire 36. However, the noise absorber 51 is disposed in the vicinity of the free wheel diode 12. The loop surface of the loop coil 52 may be arranged along the anode connection wire 37.

  Here, the effect of this embodiment is demonstrated.

  According to the present embodiment, a plurality of semiconductor elements 11, 12 (a plurality of semiconductor elements), wires 36, 37, 39 connecting the plurality of semiconductor elements 11, 12, a loop coil 52 and a ferrite bead 53 (magnetic material). The noise absorber 51 is arranged in the vicinity of the IGBT 11 (at least one of a plurality of semiconductor elements), and the loop surface of the loop coil 52 is connected to the emitter connection wire 36 (a plurality of Since it is disposed along the wire connecting the semiconductor elements along at least one of the wires that generates noise, the resonance circuit (the parasitic capacitance of the plurality of semiconductor elements 11 and 12 and the semiconductors) in which the loop coil 52 serves as a noise source. Magnetically coupled to the inductance of the wires 36 and 37 connecting the elements), the ferrite beads 53 (magnetic It is possible to attenuate the noise components by the resistance of the).

  If the generated noise is reduced, it is not necessary to slow down the switching speed of the IGBT 11, and this does not increase the loss of the semiconductor element (11), so that the efficiency and output performance of the power module 10 are improved. When the inverter 14 configured by combining the power module 10 is used for driving a motor of an electric vehicle or a hybrid vehicle, noise generated is reduced, so that the audibility of the in-vehicle radio can be improved.

  According to the present embodiment, the loop coil 52 and the ferrite bead 53 (magnetic material) are connected in series, that is, both ends of the ferrite bead 53 (magnetic material) are short-circuited. Noise components can be attenuated.

  According to the present embodiment, since the ferrite bead 53 (magnetic body) whose resistance component increases in the frequency band of noise to be attenuated is selected as the magnetic body, the noise to be attenuated can be attenuated.

  According to the present embodiment, when a plurality of semiconductor elements 11 and 12 (a plurality of semiconductor elements) are connected in parallel and arranged adjacent to each other, the noise absorber 51 is arranged between the adjacent plurality of semiconductor elements 11 and 12. Therefore, both the noises generated from the adjacent emitter connection wires 36 can be efficiently attenuated.

  According to the present embodiment, since the noise absorber 51 is disposed after securing a necessary insulation distance, it is possible to improve the insulation from the strong electrical site.

  According to the present embodiment, since the noise absorber 51 is mounted after performing a coating process having a necessary withstand voltage, the necessary withstand voltage can be obtained.

(Second Embodiment)
7 is a schematic cross-sectional view of a part of one power module 10 according to the second embodiment in a mounted state. FIG. 8 is a schematic plan view showing an element arrangement in a part of mounted state of one power module. It replaces FIG. 2 and FIG. 3 of one embodiment. The same parts as those in FIGS. 2 and 3 are denoted by the same reference numerals. Here again, it is assumed that the upper side in FIG. In FIG. 8, the sealing material 40 and the resin lid 41 shown in FIG. 7 are removed.

  In the first embodiment, the plurality of semiconductor elements 11 and 12, the emitter connection wire 36, the anode connection wire 37, and the like are high voltage application portions (high power portions), so that the noise absorber 51 secures a necessary insulation distance from the high power portions. Said to arrange in. However, in the case of a required specification that requires a relatively large insulation distance, if the noise absorber 51 is disposed in the sealing material 40 below the resin lid 41, the necessary insulation distance from the strong electrical site cannot be secured. There is.

  Therefore, in the second embodiment, the noise absorber 51 is arranged outside the power module 10 in order to ensure the necessary insulation distance from the strong electrical site even in the case of a required specification where the necessary insulation distance is relatively large. Is. That is, as shown in FIG. 7, the noise absorber 51 is disposed on the resin lid 41 above the emitter connecting wire 36 of the IGBT 11. When the noise absorber 51 is disposed on the resin lid 41, noise is radiated from the vertically lower side to the noise absorber 51. Therefore, the loop surface of the loop coil 52 is disposed in the horizontal direction.

  In the mounted state shown in FIG. 8, the first noise absorber 51 a is arranged on the resin lid 41 above the emitter connection wire 36 a of the first IGBT 11 a. Similarly, the second noise absorber 51b is vertically above the emitter connecting wire 36b of the second IGBT 11b and on the resin lid 41, and the third noise absorber 51b is vertically above the emitter connecting wire 36c of the third IGBT 11c and on the resin lid 41. The noise absorber 51c is arranged. The loop surfaces of the loop coils 52a, 52b and 52c are arranged so as to be positioned in the horizontal direction.

  According to the second embodiment, since the noise absorber 51 is disposed outside the power module 10, it is possible to improve the insulation with a strong electrical site even in the case of a required specification with a relatively large required insulation distance. it can.

(Third embodiment)
FIG. 9 is a schematic cross-sectional view of a part of one power module 10 according to the third embodiment in a mounted state. FIG. 10 is a schematic plan view showing an element arrangement in a part of mounted state of one power module. It replaces FIG. 2 and FIG. 3 of one embodiment. The same parts as those in FIGS. 2 and 3 are denoted by the same reference numerals. Here again, it is assumed that the upper side in FIG. In FIG. 10, the sealing material 40 and the resin lid 41 shown in FIG. 9 are removed.

  In the third embodiment, the ferrite beads 53 are disposed outside the power module 10 while the loop coil 52 is disposed in the noise absorber 51 at the same position as in the first embodiment. That is, in the mounted state shown in FIG. 10, the first ferrite beads 53a are arranged on the resin lid 41 between the emitter connection wire 36a of the first IGBT 11a and the emitter connection wire 36b of the second IGBT 11b. Further, the second ferrite beads 53b are arranged on the resin lid 41 between the emitter connection wire 36b of the second IGBT 11b and the emitter connection wire 36c of the third IGBT 11c. Next, the loop surfaces of the loop coils 52a and 52b are arranged along the emitter connection wires 36a, 36b, and 36c of the first, second, and third IGBTs 11a, 11b, and 11c.

  9, the loop coil 52 (52a, 52b) hangs vertically downward from the ferrite bead 53 (53a, 53b), and the lower end of the loop coil 52 (52a, 52b) is near the ceramic substrate 32. To reach. The configurations of the first and second noise absorbers 51a and 51b are the same.

  The resin lid 41 has holes (not shown) through which the loop coils 52 (52a, 52b) pass. In the third embodiment, the loop surfaces of the loop coils 52a and 52b are rectangular, but the present invention is not limited to this.

  According to the third embodiment, since the ferrite beads 53 (magnetic material) are arranged outside the power module 10 while leaving the loop coil 52 in the power module 10, the intensity of radiation noise from the outside of the power module 10 is increased. The ferrite beads 53 can be adjusted according to the frequency band. For example, if the radiation noise generated from the emitter connection wire 36 and the anode connection wire 37 is relatively strong, the number of ferrite beads 53 is increased by the amount of the strong noise, and even when the radiation noise is relatively strong, the noise is increased. Can be suppressed. If the frequency band where the radiated noise is generated is different, by changing the type of ferrite bead that can attenuate the noise generated in the different frequency band, even if the frequency band where the radiated noise is generated is different, the noise is reduced. Can be suppressed.

  In the embodiment, the IGBT is described, but it goes without saying that the present invention is applicable to the case of a power MOSFET (Nch type, Pch type) or a power transistor (NPN type, PNP type).

10 Power Module 11 IGBT (Semiconductor Device)
12 Reflux diode (semiconductor element)
32 Ceramic substrate 51 Noise absorber 52 Loop coil 53 Ferrite beads (magnetic material)

Claims (10)

A plurality of semiconductor elements;
Wires connecting these semiconductor elements, and
A noise absorber made up of a loop coil and a magnetic material,
The noise absorber is disposed in the vicinity of at least one of the plurality of semiconductor elements, and the loop surface of the loop coil is aligned with at least one of the wires connecting the plurality of semiconductor elements that generates noise. A power module characterized by being arranged in a row.   The power module according to claim 1, wherein the loop coil and a magnetic body are connected in series.   The power module according to claim 1 or 2, wherein a magnetic body having a resistance component increasing in a frequency band of noise to be attenuated is selected as the magnetic body.   4. The semiconductor device according to claim 1, wherein when the semiconductor element is an NPN transistor, the loop surface of the loop coil is arranged along the emitter connection wire of the NPN transistor. The listed power module.   5. The power according to claim 1, wherein when the semiconductor element is a free-wheeling diode, the loop surface of the loop coil is arranged along the anode connection wire of the free-wheeling diode. module.   6. The device according to claim 1, wherein when the plurality of semiconductor elements are connected in parallel and arranged adjacent to each other, the noise absorber is arranged between the plurality of adjacent semiconductor elements. The power module described in one.   The power module according to any one of claims 1 to 6, wherein the noise absorber is disposed outside the power module.   The power module according to any one of claims 1 to 6, wherein only the magnetic body is disposed outside the power module.   The power module according to any one of claims 1 to 6, wherein the noise absorber is disposed after securing a necessary insulation distance.   The power module according to any one of claims 1 to 6, wherein the noise absorber is mounted after a coating process having a required withstand voltage is performed.

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