Power semiconductor device

The present invention relates to a power semiconductor device, particularly a surge generated from a power semiconductor device.

Power semiconductor devices using power semiconductor elements are widely used. A power module is a combination of a plurality of power semiconductor elements (MOSFETs, IGBTs, etc.) together with their peripheral circuits in one package. It has advantages such as miniaturization due to high integration and easy wiring, and is used in many applications.

In power semiconductor devices, it is necessary to prevent adverse effects due to surges. For example, in the inverter circuit described in Japanese Patent Application Laid-Open No. 7-297695, the drive circuit for driving a power semiconductor element includes an overheat protection circuit for preventing overheating, but the overheat protection circuit is a reverse recovery of a flywheel diode. Malfunctions may occur due to sudden changes in current that occur at times. The control circuit has a common output terminal that outputs an alarm signal when an overcurrent or short-circuit current occurs, but a Schottky diode is placed between the common output terminal of the control circuit for the lower arm and the power supply terminal Vcc. By connecting to, the reverse current flows in the control IC board, and the malfunction of the overheat protection circuit is prevented. Alternatively, connect a capacitor between the common output terminal of the control circuit and the ground terminal GND to prevent fluctuations in the reference voltage in the control IC board.<patcit num="1"><text>Japanese Unexamined Patent Publication No. 7-297695</text></patcit>

<p> When a power semiconductor device is used, a peripheral circuit (gate drive circuit, photocoupler, etc.) that controls the power semiconductor element due to a surge generated inside the device, or an external signal generation circuit that supplies a signal to the gate drive circuit. (Microcomputer, etc.) may be destroyed. However, the inverter circuit described in Japanese Patent Application Laid-Open No. 7-297695 blocks surge voltage and surge current, and does not completely eliminate the influence on the connected peripheral devices. In this inverter circuit, a surge voltage is applied to the peripheral device or a surge current flows, which may cause damage to the peripheral device and increase electrical loss.</p><p> An object of the present invention is to provide a power semiconductor device that suppresses destruction of peripheral circuits due to an internal surge.</p>

<p> The first power semiconductor device according to the present invention is composed of a series circuit of a high-pressure side power switching semiconductor element and a low-pressure side power switching semiconductor element, and a DC voltage source can be connected to both ends of the series circuit. Moreover, the power switching semiconductor element capable of supplying an output voltage from the connection point between the high pressure side power switching semiconductor element and the low pressure side power switching semiconductor element, and the high pressure side power switching semiconductor element and the low pressure side power switching semiconductor. A flywheel diode antiparalleled to each element, a high pressure side drive circuit connected to the gate of the high pressure side power switching semiconductor element, a low pressure side drive circuit connected to the gate of the low pressure side power switching semiconductor element, the above. A control power supply circuit that supplies a power supply voltage to the low-voltage side drive circuit, and a diode that is connected in the forward direction between the low-voltage side drive circuit and the control power supply circuit are provided.<u style="single">The withstand voltage of the diode prevents the DC voltage input to the series circuit of the high-voltage side power switching semiconductor element and the low-voltage side power switching semiconductor element from being applied to the low-voltage side drive circuit. Is set to be larger than the DC voltage.</u>。 </p><p> The second power semiconductor device according to the present invention is composed of a series circuit of a high-pressure side power switching semiconductor element and a low-pressure side power switching semiconductor element, and a DC voltage source can be connected to both ends of the series circuit. Moreover, the power switching semiconductor element capable of supplying an output voltage from the connection point between the high pressure side power switching semiconductor element and the low pressure side power switching semiconductor element, and the high pressure side power switching semiconductor element and the low pressure side power switching semiconductor. A flywheel diode antiparalleled to each element, a high pressure side drive circuit connected to the gate of the high pressure side power switching semiconductor element, a low pressure side drive circuit connected to the gate of the low pressure side power switching semiconductor element, the above. It includes a control power supply circuit that supplies a power supply voltage to the low-voltage side drive circuit, and a diode that is connected in the forward direction to the input signal of the low-voltage side drive circuit.<u style="single">The withstand voltage of the diode prevents the DC voltage input to the series circuit of the high-voltage side power switching semiconductor element and the low-voltage side power switching semiconductor element from being applied to the low-voltage side drive circuit. Is set to be larger than the DC voltage.</u>。 </p><p> The third power semiconductor device according to the present invention is composed of a series circuit of a high-pressure side power switching semiconductor element and a low-pressure side power switching semiconductor element, and a DC voltage source can be connected to both ends of the series circuit. Moreover, the power switching semiconductor element capable of supplying an output voltage from the connection point between the high pressure side power switching semiconductor element and the low pressure side power switching semiconductor element, and the high pressure side power switching semiconductor element and the low pressure side power switching semiconductor. A flywheel diode antiparalleled to each element, a high pressure side drive circuit connected to the gate of the high pressure side power switching semiconductor element, a low pressure side drive circuit connected to the gate of the low pressure side power switching semiconductor element, the above. It includes a photocoupler that supplies an input signal to the low-voltage side drive circuit, and a diode that is connected in the forward direction between the low-voltage side drive circuit and the output terminal of the photocoupler.<u style="single">The withstand voltage of the diode prevents the DC voltage input to the series circuit of the high-voltage side power switching semiconductor element and the low-voltage side power switching semiconductor element from being applied to the low-voltage side drive circuit. Is set to be larger than the DC voltage.</u>.. Preferably, the capacitor and resistor are further grounded in parallel from the connection point between the diode and the input terminal of the low voltage side drive circuit.</p><p> The first to third power semiconductor devices preferably further provide a current detection resistor connected between the low-level side of the DC voltage source and the low-voltage side power switching semiconductor element. Be prepared.</p><p> The first to third power semiconductor devices further include, for example, the DC power supply connected to a series circuit of the high-voltage side power switching semiconductor element and the low-voltage side power switching semiconductor element. Be prepared.</p>

<p> Since the power semiconductor device suppresses the surge voltage and surge current generated internally and does not transmit the surge current to the peripheral device, it is possible to prevent the peripheral circuit of the power semiconductor device and the external circuit connected to the peripheral circuit from being destroyed.</p>

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference symbols indicate the same or equivalent.

Embodiment 1. FIG. 1 shows a three-phase motor drive circuit according to the first embodiment. The power module 10 including the power switching semiconductor elements (hereinafter referred to as power chips) 22 and 24 is connected in parallel to the DC power supply, and the DC voltage is supplied to the power chips 22 and 24 from the DC power supply. The DC power supply includes, for example, a diode bridge rectifier circuit 12 and a smoothing capacitor 14. The microcomputer (including the case of DSP etc.) 20 generates a control signal for the power chip and supplies it to the power module 10. The power module 10 generates three-phase alternating current in response to a control signal to drive the motor 18 with an L load.

In the power module 10, a series circuit consisting of three pairs of power chips 22 and 24 connected in series, respectively, is connected to the high level side and the low level side of the smoothing capacitor 14. The power chips 22 and 24 are, for example, power MOSFETs and IGBTs. A flywheel diode 26 is connected in antiparallel to each of the power chips 22 and 24. The three power chips 22 and the flywheel diode 26 connected to the high level side of the DC from the DC power supply form the upper arm, and the three power chips 24 and the flywheel diode 26 connected to the low level side thereof. Consists of the lower arm. The connection points between the power chips 22 and 24 of the upper arm and the lower arm are output terminals U, V or W to the three-phase motor 18. A control signal from the microcomputer 20 is supplied to the gate drive circuit (also simply referred to as a drive circuit; in this example, the gate drive ICs 28 and 30) provided for each gate of the power chips 22 and 24, and the gate drive ICs 28 and 30 are supplied. Supply the gate signal to the gates of the corresponding power chips 22 and 24 based on the control signal. The power chips 22 and 24 perform a switching operation in response to the gate signal. The gate drive IC 28 is also called an HV IC, the gate drive IC 30 is also called an LV IC, and a known gate drive circuit for a power switching element can be used. (The gate drive ICs 28 and 30 connected to the gates of the power chips in the center and the right side are connected in the same way, so the illustration is omitted.) The low level side of the DC from the DC power supply. A current detection resistor 16 is arranged between the lower arm and the lower arm, and the overcurrent flowing through the lower arm is detected by a voltage drop. (Note that the gate drive IC28, Reference numeral 30 denotes, more generally, a control circuit including an overcurrent protection function based on the voltage drop in the current detection resistor 16, but the description of the overcurrent protection function will be omitted. ) The microcomputer 20, the gate drive ICs 28 and 30, and the bridge 12 side of the current detection resistor 16 are commonly grounded. Further, from the control power supply circuit 34 external to the power module 10, a power supply voltage of, for example, 15 V is supplied to the gate drive ICs 28 and 30, and a power supply voltage of, for example, 5 V is supplied to the microcomputer 20. In the example of FIG. 1, the three-phase alternating current is rectified and supplied to the power module 10, but the two-phase alternating current may be rectified and supplied.

Here, the power supply terminal of the gate drive IC 30 for the lower arm is connected to the control power supply 34 of the gate drive IC 30 via the high withstand voltage diode 32. The reason for providing the high withstand voltage diode 32 connected in the forward direction between the gate drive IC 30 and the control power supply 34 is as follows. When the power chip 24 of the lower arm breaks with the emitter open due to a steep current change generated during the reverse recovery of the freewheel diode 26 at the turn-off of the power chip 24 of the lower arm, or when the current detection resistor 16 becomes open, etc. Surge voltage and surge current are generated in the wiring inside the power module. Due to this surge voltage and surge current, a high voltage is applied to the gate drive IC30 that drives the power chip 24, and a high voltage is also applied to the control power supply circuit 34 and the microcomputer 20 side of the gate drive IC30 to control the power supply. The circuit 34 and the microcomputer 20 may be destroyed. Therefore, in order to prevent this, a high withstand voltage diode 32 is inserted between the gate drive IC 30 and its control power supply line so that current does not flow toward the control power supply circuit 34, and the control power supply circuit 34 and the microcomputer 20 are inserted. Prevent the destruction of. Since the high withstand voltage diode 32 is inserted, the surge voltage and surge current generated in the power module wiring are blocked, and the influence on the connected peripheral devices can be reduced.

In this way, the diode 32 is used to prevent the high voltage input from the DC power supply from being applied to the control power supply circuit 34 of the drive IC 30 and the microcomputer 20 side. Therefore, the withstand voltage of the diode 32 is determined by the power module. The voltage is set higher than the voltage applied by the DC power supply connected to the input side. Therefore, for example, it is set to about the same as the withstand voltage of the smoothing capacitor 14, for example, 600V. The concept of withstand voltage is the same in other embodiments described below.

In the above description, the description has been made in relation to the configuration of the lower arm (power chip 24, gate drive IC 30), but the power chip 22 of the upper arm may also cause destruction of peripheral circuits. That is, when a surge voltage and a surge current are generated in the wiring in the power module, a high voltage may be applied to the gate drive IC 28 that drives the power chip 22. However, since the gate drive IC 28 for the upper arm is provided with a high voltage circuit section inside due to its configuration, the peripherals such as the control power supply circuit 34 and the microcomputer 20 side are compared with the gate drive IC 30 for the lower arm. It can be said that it is difficult to apply a high voltage to the device. However, in order to eliminate the influence on the peripheral devices connected to the power module 10, the power supply terminal of the gate drive IC 28 is also a control power supply circuit via the high withstand voltage diode 32, as in the gade drive IC 30. It is desirable to connect to 34 so that no current flows toward the control power supply circuit 34.

In that case, it is not necessary to individually connect the high withstand voltage diode 32 to the power supply terminals of the gate drive ICs 28 and 30. The power supply terminals may be shared by connecting the wirings from the power supply terminals of the gate drive ICs 28 and 30 to each other, and a high withstand voltage diode 32 may be provided between the shared power supply terminals and the control power supply circuit 34 ( See Figure 5). Further, the high withstand voltage diode 32 may be provided inside or outside the power module.

Embodiment 2. FIG. 2 shows a three-phase motor drive circuit according to the second embodiment. In this three-phase motor drive circuit, the difference from the circuit shown in FIG. 1 is that instead of inserting a high withstand voltage diode 32 between the gate drive IC 30 and its control power supply circuit 34, the microcomputer 20 controls the drive IC 30. A high withstand voltage diode 36 is inserted in the signal input line. By providing the diode 36 connected in the forward direction to the input signal of the drive IC 30, no current flows toward the microcomputer 20, so that the surge voltage and surge current generated in the power module wiring enter the microcomputer 20 side. Blocks and prevents the destruction of the control power supply circuit of the microcomputer 20 and the gate drive IC30.

Furthermore, it is desirable to insert a high withstand voltage diode 36 not only on the control signal input line side from the microcomputer 20 to the gate drive IC 30 but also on the control signal input line side to the gate drive IC 28 (see FIG. 5). ). As a result, the influence of the surge voltage and surge current generated in the power module 10 on peripheral devices (destruction of the control power supply circuit and the microcomputer) can be eliminated. The high withstand voltage diode 36 may be provided inside or outside the power module 10.

It is assumed that the control signal input lines of the gate drive ICs 28 and 30 in each embodiment of the present invention are grounded (pulled down) inside the IC via a resistor, but the present invention is not necessarily limited to this. It is not something that is done.

Embodiment 3. FIG. 3 shows a three-phase motor drive circuit according to a third embodiment. The difference from the circuit shown in FIG. 1 is that the photocoupler 38 is used to insulate the microcomputer 20 side from the power chips 22 and 24 in a direct current manner. The signal of the microcomputer 20 is connected to the light emitting element (diode) 40 side of the photocoupler 38, and the light receiving element (diode) 44 of the photocoupler 38 is reversely connected between the control power supply circuit 34 and the base of the transistor 42. The collector of the transistor 42 is connected to the gate drive IC 30 and the pull-up resistor 45. The emitter of the transistor 42 is grounded in common with the power module 10. Unlike the circuit shown in FIG. 1, a high withstand voltage diode 32 is not inserted between the gate drive IC 30 and its control power supply circuit 34.

In this three-phase motor drive circuit, when the power chip 24 of the lower arm is destroyed by opening the emitter, or when the current detection resistor 16 is opened, a high voltage is applied to the gate drive IC 30 that drives the power chip 24. Similarly, a high voltage is applied to the photocoupler 38, which may destroy the photocoupler 38. In order to suppress this, a high withstand voltage diode 46 is inserted so that no current flows toward the input signal line of the photocoupler 38. By providing the diode 46 connected in the forward direction between the gate drive IC 30 and the output terminal of the photocoupler 38, current does not flow toward the photocoupler 38, and the photocoupler 38 can be prevented from being destroyed.

Further, it is desirable to insert a high withstand voltage diode 46 not only between the gate drive IC 30 and the output terminal of the photocoupler 38 but also between the gate drive IC 28 and the output terminal of the photocoupler 38. As a result, the influence of the surge voltage and surge current generated in the power module 10 on peripheral devices (destruction of the photocoupler, etc.) can be almost eliminated.

Embodiment 4. In the three-phase motor drive circuit shown in FIG. 4, a high withstand voltage diode 46 is inserted into the input signal line of the photocoupler 38 to prevent the photocoupler 38 from being destroyed, and a capacitor is further formed, as in the circuit shown in FIG. Connect in parallel between 48, resistor 50, diode 46, gate drive IC30 and ground. The capacitor 48 constitutes an input filter.

When the light receiving side transistor of the photocoupler 38 becomes L level by inserting the capacitor 48 on the signal input side of the gate drive IC30, the discharge of the capacitor 48 due to the diode 46 is compared in the gate drive IC30. This is performed via a pull-down resistor having a high value, and a response delay occurs before the input signal of the gate drive IC 30 reaches the L level. Therefore, the delay time is shortened by inserting a resistor 50 in parallel with the capacitor 48. The time constant of the response by the capacitor 48 and the resistor 50 may be determined according to the desired response time.

Embodiment 5. As another embodiment, it is effective to combine the first embodiment and any of the second to fourth embodiments, and by using these combined circuits, the surge voltage generated in the power module 10 It is possible to eliminate the influence of the surge current on the peripheral circuits.

For example, FIG. 5 shows a three-phase motor drive circuit that combines embodiments 1 and 2. In this circuit, a high withstand voltage diode 32 connected to the power supply control circuit 34 and a high withstand voltage diode 36 connected to the input signal are used. In this figure, the high withstand voltage diodes 32 and 36 are not provided by adapting only to the gate drive IC30 for the lower arm as in the drive circuits shown in FIGS. 1 and 2, but the upper arm. It is also adapted to the gate drive IC 28 for use, and the details are as described in each embodiment. Here, one high-voltage side diode 32 is commonly connected to both the low-voltage side drive circuit 30 and the high-voltage side drive circuit 28. Further, although not shown, for example, in the three-phase motor drive circuit using the photocoupler shown in FIG. 3, a high withstand voltage diode 46 may be combined in addition to the high withstand voltage diode 32 by combining the first and third embodiments. ..

Although the power module has been mainly described in each of the above-described embodiments, a semiconductor current device in which the circuit elements included in the power module and the DC power supplies 12 and 14 are integrated may be provided. This has the advantages of easy wiring and easy assembly of application equipment.

<figref num="1">Drive circuit diagram of Embodiment 1</figref><figref num="2">Drive circuit diagram of the second embodiment</figref><figref num="3">Drive circuit diagram of Embodiment 3</figref><figref num="4">Drive circuit diagram of Embodiment 4</figref><figref num="5">Drive circuit diagram consisting of a combination of Embodiments 1 and 2.</figref>

Code description

22, 24 High-voltage side and low-voltage side power semiconductor switching elements, 26 FW diodes, 28,30 drive circuits (gate drive ICs), 32, 36 high-voltage diodes, 38 optocouplers, 46 high-voltage diodes, 48 capacitors, 50 resistors ..