JP2762651B2 - Drive circuit for power converter - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit of a power converter in which a drive power supply for a semiconductor switch element of a lower arm is shared.

[Conventional technology]

FIG. 3 is a circuit diagram showing a conventional example of a power converter in which a drive power supply for a semiconductor switch element of a lower arm is shared.

FIG. 3 shows a DC power supply 2 in which four main transistors 4, 5, 6, 7 as semiconductor switching elements are connected in a single-phase bridge.
2 shows a transistor inverter that converts DC power from the power supply and the smoothing capacitor 3 into AC power and supplies the AC power to the load 8. Note that freewheel diodes are separately connected to these four main transistors 4, 5, 6, 7 in antiparallel.

A drive signal is sent from the base drive circuit 10 to the bases of these main transistors constituting the inverter. According to this drive signal, the four main transistors 4,5,
The inverters 6 and 7 sequentially perform on / off operations to convert DC power into AC power. The drive circuit of the main transistors 4 and 5 constituting the upper arm of this inverter is:
Since it has nothing to do with the present invention, its illustration and description are omitted.

For the main transistors 6 and 7 constituting the lower arm, a common drive power supply 11 is prepared for both, and the drive transistor 12 is operated to interrupt the current from the drive power supply 11 to the base of the main transistor 6. I do. The base current of the main transistor 7 is turned on and off by the operation of the drive transistor 13. Therefore, even if the driving power supply 11 is common, the on / off operation can be performed separately from the main transistors 6 and 7. In addition, 14 is a wiring inductance existing in the base drive circuit.

In order to reduce the size and cost of the base drive circuit 10, it is effective to use a common drive power supply 11 for the lower arm, as shown in FIG.

[Problems to be solved by the invention]

FIG. 4 is a circuit diagram showing a current path in the conventional circuit shown in FIG.

Now, when the main transistor 4 and the freewheeling diode connected in anti-parallel to the main transistor 5 are conducting, and the current I ₀ flows between them and the load 8, the main transistor 7 is turned on. This main transistor 7
Rise is going very sharp large current (i.e. the sum of the currents of the reverse recovery current of the freewheeling diode and the return current I ₀₎ is to flow in.

Although most of the current is flowing in the smoothing capacitor 3 through the main circuit wiring inductance is little, a portion of the current I ₁ flows to the base drive circuit 10 via the emitter of the main transistor 7, the wiring inductance 14 , Flows through the path shown by the broken line toward the smoothing capacitor 3.

This shunt current I _1, the wiring inductance 14 of the base drive circuit 10, since the driving power source 11 as shown to induce a reverse voltage, or reduce the base-emitter voltage of the main transistor 7 Causes inconvenience such as generation of vibration.

Such a defect phenomenon is remarkable in that when a voltage-driven high-speed switching element such as a field-effect transistor is used, the gate drive voltage at turn-on decreases, the turn-on time increases, and the turn-on loss increases. Appears.

Therefore, an object of the present invention is to prevent a main circuit current from shunting to a drive circuit when a drive power supply for a lower arm semiconductor switch element of a power converter is shared.

[Means for solving the problem]

In order to achieve the above object, a drive circuit of the present invention provides a drive power supply for a semiconductor switch element of a lower arm in a power converter configured by bridge-connecting a semiconductor switch element and a diode in anti-parallel connection. In a power converter commonly provided for each lower arm, a line for transmitting a drive signal from the drive power supply to the semiconductor switch element of the lower arm and a return line of the drive signal are commonly penetrated. An iron core is provided separately for each of the semiconductor switch elements of the lower arm.

[Action]

The present invention relates to a magnetic flux generated in a line for sending a drive signal to be applied to a semiconductor switch element of a lower arm from a drive power supply,
The magnetic flux generated in the retrace of the drive signal cancels each other, so that the current for driving the semiconductor switch element flows without any trouble, but the main circuit current is prevented from being shunted to this drive circuit. Specifically, a configuration in which the transmission line and the return line of the drive signal are collectively passed through the center hole of the annular core is separately provided for each semiconductor switch element.

〔Example〕

 FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 1 shows a case of a transistor inverter as in the conventional circuit of FIG. 3, in which a DC power supply 2, a smoothing capacitor 3, four main transistors 4, 5, 6, 7, as semiconductor switching elements, a load, 8, base drive circuit 10, drive power supply 11,
Driving transistors 12 and 13, and wiring inductance
14 has the same names, uses, and functions as those already described for the conventional circuit of FIG. 3, and therefore description thereof is omitted.

In the present invention, an iron core 21 is provided between the drive transistor 12 and the main transistor 6, and an iron core 22 is provided between the drive transistor 13 and the main transistor 7. The return current is made to pass through the through-hole of each iron core.

As a result, the base drive current of the main transistor 7 (that is, the current in the path indicated by the broken line) reciprocates through the through hole of the iron core 22. At this time, the magnetic flux generated in the iron core 22 by the current in the forward path and the magnetic flux generated in the iron core 22 by the current in the return path cancel each other, so that the base drive current can flow through the iron core 22 without any trouble.

However, the main transistor 7
The current shunted from the main circuit through the wiring inductance 14 (ie, the current in the path indicated by the broken line)
Since the magnetic flux generated when passing through the core 22 and the iron core 21 is not canceled out, almost no current can flow through the path indicated by the broken line.

FIG. 2 is a structural diagram showing the structure of an iron core used in the circuit of the embodiment shown in FIG.

As shown in FIG. 2, a connection line 31 from the drive power supply 11 to the base of the main transistor and an emitter connection line 32 from the main transistor to the drive power supply 11 are twisted to form an iron core.
Pass through 21 through holes.

If the iron core 21 is made of a material having good square saturation characteristics, the above-mentioned shunt current can be almost completely blocked.

〔The invention's effect〕

According to the present invention, the power conversion device is provided by collectively passing a forward line and a return line of a drive current to be supplied to the semiconductor switch element constituting the power conversion device through an iron core having a through hole. When the drive power supply for the semiconductor switch element constituting the lower arm is made common, the current shunted to this drive circuit can be prevented, so that the drive circuit can be made smaller and less expensive by sharing the drive power supply. A propelling effect can be obtained, and a high-speed semiconductor switch element can be operated without any trouble.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a structural diagram showing the structure of an iron core used in the circuit of FIG. 1, and FIG. 3 is a semiconductor switch of a lower arm. FIG. 4 is a circuit diagram showing a conventional example of a power conversion device using a common element driving power supply, and FIG. 4 is a circuit diagram showing a current path in the conventional circuit shown in FIG. 2 ... DC power supply, 3 ... Smoothing capacitor, 4,5,6,7 ...
Main transistor as semiconductor switch element, 8 Load, 10 Base drive circuit, 11 Drive power supply, 12, 13
... Driving transistor, 14 ... Wiring inductance, 21,2
2 ... iron core, 31 ... base connection line of main transistor, 32
…… Emitter connection line of the main transistor.

Claims (1)

(57) [Claims] 1. An electric power converter in which a drive power supply for a semiconductor switch element of a lower arm is provided in common for each lower arm in a power converter configured by connecting a semiconductor switch element and a diode in anti-parallel connection in a bridge connection. In the conversion device, a wire for transmitting a drive signal from the drive power supply to the semiconductor switch element of the lower arm and a return wire of the drive signal are passed in common, and an iron core is passed through the semiconductor switch element of the lower arm. A driving circuit for a power converter, wherein the driving circuit is provided separately for each of the above.