JP3777755B2 - Inverter device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inverter device that converts a DC voltage into an AC voltage.
[0002]
[Prior art]
Conventionally, in this type of inverter device, as shown in Japanese Patent Application Laid-Open No. 7-123738, a plurality of switching elements connected in series are arranged in a plane, and each terminal is electrically connected by a bus bar. Yes.
[0003]
[Problems to be solved by the invention]
However, when a plurality of switching elements are arranged in a plane in this way, there is a problem that the physique must be increased.
The present invention has been made in view of the above problems, and an object thereof is to reduce the size of an inverter device.
[0004]
[Means for Solving the Problems]
In order to achieve the above object, in the invention described in claim 1, at least two switching elements connected in series between the positive bus and the negative bus are stacked in the vertical direction, and the back electrode of the upper switching element and A surface electrode of the lower switching element is joined so as to be electrically conductive, and one side surface of each of the upper switching element and the lower switching element in one direction orthogonal to the vertical direction Are aligned, the other side surfaces facing the one side surface are displaced, and a region that is not stacked with the upper switching device is exposed on the surface side of the lower switching device. Further, a plurality of electrode pads of the lower switching element are formed .
[0005]
By adopting such a laminated structure, the inverter device can be miniaturized. Also, because they form an electrode pad in a region which is not laminated with the upper switching element on the surface side of the lower switching element, the electrode was taken out on the switching elements of the lower side even in the case of a stacked structure It can be carried out.
[0006]
The back electrode of the upper switching element and the surface electrode of the lower switching element can be joined together by brazing as in the second aspect of the invention. Moreover, if it joins on both sides of a plate-shaped electrode like invention of Claim 3 , the heat dissipation of a switching element can be performed favorably.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments shown in the drawings will be described below.
FIG. 1 shows a partial electrical connection diagram when a 4-level inverter is used as a multi-level power converter.
In the figure, capacitors 2, 3, and 4 are connected in series in parallel with the DC voltage source 1. A U-phase inverter arm 10 is provided between the positive bus 5 and the negative bus 6 of the inverter. The inverter arm 10 includes a plurality of semiconductor switching elements (vertical power MOS transistors in which current flows in the vertical direction) 11a to 11f, antiparallel diodes (flywheel diodes) 12a to 12f, and the output voltage level is changed. It is composed of diodes 13a to 13d that form current paths. Here, the switching elements 11a to 11c constitute an upper arm, and the switching elements 11d to 11f constitute a lower arm. Although not shown, the V-phase and W-phase inverter arms are also provided between the positive bus 5 and the negative bus 6 with the same configuration as the U-phase and using capacitors 2 to 4 in common.
[0008]
In such a configuration, on / off control of each switching element in the U-phase, V-phase, and W-phase inverter arms converts the DC voltage of the DC voltage source 1 into an AC voltage, and loads such as a three-phase AC (not shown) Drive the electric motor.
In the present embodiment, the switching elements 11a to 11c constituting the upper arm and the switching elements 11d to 11f constituting the lower arm are respectively laminated to form a single module. In FIG. 2, the typical external appearance structure of the structure which laminated | stacked switching element 11a-11c which comprises an upper arm is shown.
[0009]
As shown in the figure, the chip size is gradually reduced from the switching element 11a to the switching element 11c, and when these are stacked, the gate electrode pads 101, 111, 121 and the source of the switching elements 11a, 11b, 11c Each of the electrode pads 102, 112, and 122 does not overlap. That is, the switching elements 11a, 11b, and 11c are stacked stepwise, and the gate electrode pad and the source electrode pad are formed on the respective surfaces (the surfaces of the switching elements 11a and 11b that are not stacked with the upper switching element). Is to be formed. These gate electrode pads and source electrode pads are electrically connected to the outside by wire bonding. In addition, although the source electrode which makes a surface electrode is formed in the surface side of each switching element, the gate electrode pad and the source electrode pad are formed on the protective film which is not shown in figure formed on the source electrode. .
[0010]
In FIG. 3, the cross-sectional structure of the part which laminated | stacked switching element 11a-11c is shown. As shown in the figure, the switching elements 11a, 11b, and 11c have source electrodes 103, 113, and 123 formed as surface electrodes and drain electrodes 104, 114, and 124 formed as back electrodes. A known vertical MOS transistor in which current flows in the vertical direction is formed. The source electrode 103 of the switching element 11a and the drain electrode 114 of the switching element 11b, and the source electrode 113 of the switching element 11b and the drain electrode 124 of the switching element 11c are joined by brazing.
[0011]
With such a stacked structure, it is possible to cause a current to flow from the switching element 11a to the switching element 11c.
Further, the switching elements 11d to 11f constituting the lower arm also have a stacked structure, similarly to the switching elements 11a to 11c constituting the upper arm.
[0012]
Thus, by making a plurality of switching elements into a single module as a laminated structure, a small inverter device with low loss and low noise can be obtained.
In the above-described embodiment, the source electrode 103 of the switching element 11a and the drain electrode 114 of the switching element 11b, and the source electrode 113 of the switching element 11b and the drain electrode 124 of the switching element 11c are directly brazed. However, as shown in FIG. 4, metal plate electrodes 130 and 131 may be sandwiched between them, and may be joined by brazing. In this case, the heat dissipation of the switching element that is the power element can be improved.
[0013]
In the embodiment described above, the configuration when applied to a four-level inverter has been described. However, a three-level inverter or an inverter having five or more levels can have a stacked structure similar to the above.
[Brief description of the drawings]
FIG. 1 is a partial electrical connection diagram of a four-level inverter.
FIG. 2 is a schematic external view of a structure in which switching elements 11a to 11c constituting an upper arm are stacked.
FIG. 3 is a diagram showing a cross-sectional configuration of a portion where switching elements 11a to 11c are stacked.
FIG. 4 is a diagram showing another embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... DC voltage source, 2-4 ... Capacitor, 5 ... Positive bus, 6 ... Negative bus,
10 ... Inverter arm, 11a-11f ... Switching element,
12a to 12f: anti-parallel diode, 13a to 13d: diode,
101, 111, 121 ... gate electrode pads,
102, 112, 122 ... source electrode pads,
103, 113, 123 ... source electrodes as surface electrodes,
104, 114, 124: Drain electrodes as backside electrodes.

Claims (3)

At least two switching elements connected in series between the positive bus and the negative bus are stacked in the vertical direction so that the back electrode of the upper switching element and the surface electrode of the lower switching element are electrically connected. One side surface of each of the upper side switching element and the lower side switching element is aligned in one direction orthogonal to the up-down direction, and the other side surface facing the one side surface And a region not stacked with the upper switching element is exposed on the surface side of the lower switching element, and a plurality of electrode pads of the lower switching element are formed in the region. An inverter device characterized by that. The inverter device according to claim 1 , wherein a back electrode of the upper switching element and a surface electrode of the lower switching element are joined by brazing. 2. The inverter device according to claim 1 , wherein a back electrode of the upper switching element and a surface electrode of the lower switching element are joined with a plate electrode interposed therebetween.

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