JPH0515146A - Supplying circuit for base drive signal of parallel transistor - Google Patents

Abstract

PURPOSE:To positively prevent the branching of a collector current to an emitter connection line by connecting a common code reactor between a base connection line connecting bases of transistors to each other and emitter connection line. CONSTITUTION:One winding of the first common mode reactor 21 is connected to an emitter connection line 7 connecting transistors 11 and 12 to each other and the other winding of the reactor 21 is connected to the second emitter line 8 connecting the transistors 11 and 12 to each other. Similarly, each winding of the second common mode reactor 22 is connected to the emitter connection lines 7 and 8 connecting adjacent transistors 12 and 13 to each other. When such a constitution is used, the branching of a collector current to the first emitter line 7 can be prevented, because the collector current flows only to the second emitter connection line 8 and the branching of the current to the line 7 is blocked even when the current starts to flow to the line 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for supplying a base drive signal when a plurality of transistors are connected in parallel and used.

[0002]

2. Description of the Related Art Conventionally, when a plurality of transistors are connected in parallel and a common base drive signal is given to them, the connection line connecting each transistor should be shortest. The base drive signal is supplied from the central portion of the connection line so that the parallel transistors operate simultaneously. In addition, when the transistor has a large capacity, the emitter of each transistor has a main current so that the main current (that is, the current flowing from the collector to the emitter) does not affect the operation of the transistor by affecting the base current. The emitter terminal and the emitter terminal for the base current are separately provided, and the wiring for the main current and the wiring for the base current are separated.

FIG. 3 is a circuit diagram showing a conventional example of a circuit in which a plurality of transistors are arranged in parallel and a common base drive signal is supplied to them, and a case where three transistors are connected in parallel is shown. . That is, three transistors 1
The collectors 1, 12, and 13 are connected to each other by a collector connection line 5, and the bases are connected to each other by a base connection line 6. The emitters are connected to each other by a first emitter connection line 7 for supplying a base drive current. And a second emitter connection line 8 for passing a main current. Further, the base drive signal from the base drive circuit 4 is connected so as to be supplied from the central portion of the base connection line 6 and the first emitter connection line 7. In such a parallel connection configuration, the DC power supply 2 and the load 3 are connected between the collector and the emitter of each transistor, and the base drive signal from the base drive circuit 4 is given to the three transistors 11. , 12, 13 are operated simultaneously.

[0004]

As already described in the conventional circuit of FIG. 3, in the circuit in which a plurality of large capacity transistors are connected in parallel, the emitter of each transistor is connected to the first emitter connection line for the base drive signal. 7 and the second emitter connecting line 8 for the main current, that is, the collector current, are wired. Since these two connecting lines are electrically connected,
It is unavoidable that the collector current is shunted not only to the second emitter connecting line 8 but also to the first emitter connecting line 7. When the collector current is direct current or low frequency alternating current, this current is shunted in inverse proportion to the resistance value of both connecting lines, and in the case of high frequency alternating current, it is divided in inverse proportion to the reactance value of both connecting lines. However, in the case of a transistor, a high frequency alternating current becomes a problem. For example, the changing speed dI _C / dt of the collector current I _C when the transistor performs the switching operation.
Is 100 A / μsec, and the inductance L _{E of} the first emitter connecting line 7 is 0.05 μH (0.05 μH corresponds to a wiring length of 5 cm), the first emitter connecting line 7
The voltage drop V _E and these 100A / mu sec, a product of the 0.05MyuH, the 5 volts. Since the base drive signal is typically about 10 volts positive or negative, a voltage drop of 5 volts is a serious obstacle to the base drive signal.

FIG. 4 is a circuit diagram for explaining the problem of the conventional circuit shown in FIG. 3, but the illustration of the third transistor 13 is omitted in order to simplify the illustration. In FIG. 4, in order to turn on the first transistor 11, the base drive circuit 4 causes a base forward bias current I _{B1 to} flow from the base of the first transistor 11 to the emitter. On the other hand, a shunt of the collector current I _{C in} the first emitter connection line 7 causes a voltage drop of the polarity shown in the wiring inductance 17 of the first emitter connection line 7. since it is polar to prevent the bias current I _B1, the base forward bias current I _B1
Decreases, which causes a problem that the turn-on time increases and the turn-on loss increases. Reference numeral 18 denotes the wiring inductance of the second emitter connection line 8, and the collector current I _C that should flow to the second emitter connection line 8 due to the wiring inductance 18 is shunted to the first emitter connection line 7. .

FIG. 5 is a circuit diagram for explaining another problem of the conventional circuit shown in FIG. 3, but the description of the third transistor 13 is omitted here for the sake of simplicity. When the parallel transistor shown here constitutes the arm of the inverter, the freewheel diode 19 is connected in antiparallel to the parallel circuit of the transistors 11 and 12. Figure 5 shows this freewheel diode 19
It shows the reverse recovery time of. This free current change rate when the reverse recovery current I _D flowing into the wheel diode 19 is extinguished very fast, the second emitter connection line 8 the reverse recovery current I _D was flowing, the reverse recovery current I _D A voltage of the illustrated polarity is induced in the wiring inductance 18 in an attempt to keep the current flowing. Due to this induced voltage, a current I _{E circulates} between the second emitter connection line 8 and the first emitter connection line 7. At this time, since the transistors 11 and 12 are in the reverse bias state, the base reverse bias current I _B2 is flowing, but the induced voltage is the base reverse bias current I _B2.
Since the polarity _{blocks B2} , the base reverse bias current I _B2 may decrease and the transistor may turn on accidentally. At the time of reverse recovery of the freewheel diode 19, a voltage having a fast voltage change speed is applied between the cathode and the anode of the freewheel diode 19, that is, between the collector and emitter of the transistors 11 and 12 to reduce the junction capacitance between the collector and base of the transistor. After that, the voltage change rate deviation current flows into the base in the forward bias direction. Therefore, the decrease in the base reverse bias current I _B2 is apt to cause the transistor to be turned on erroneously, and the opposite arm element is turned on in the inverter, and this erroneous on may cause a serious accident such as arm short circuit or element damage. .

Therefore, an object of the present invention is to prevent the base drive signal applied to the parallel transistors from being affected and reduced by the collector current flowing between the parallel transistors.

[0008]

In order to achieve the above object, the base drive signal supply circuit of the present invention is such that the collectors of a plurality of transistors are commonly connected by a collector connection line and the emitters of the plurality of transistors are connected to each other. Provides a first emitter connection line that connects each emitter in common and a second emitter connection line that connects each emitter in common, connects each base in common by a base connection line, and drives a common base for each transistor. In a parallel transistor having a configuration in which a base drive circuit that supplies a signal is connected to the emitter connection line and the base connection line, two sets of windings insulated from each other are formed on the base connection line connecting adjacent transistors to each other. Insert one winding of a common mode reactor with a common core and connect the same adjacent transistors to each other. In that the first emitter connection line,
The other winding of the common mode reactor is inserted, or instead of the common mode reactor, the base connection line and the first emitter connection line connecting adjacent transistors are collectively packaged, and The wire shall be passed through this through hole of the iron core having the through hole.

[0009]

According to the present invention, a first emitter connection line for supplying a base drive signal and a second emitter connection line for supplying a collector current are separately wired to each emitter of transistors connected in parallel. However, either a common mode reactor is inserted between the base connection line connecting the bases of adjacent transistors and the above-mentioned first emitter connection line of the adjacent transistor, or both of these connection lines are connected. And the bundled connecting wire penetrates the iron core having the through hole. With such a configuration, a) the inductance of the first emitter connecting line viewed from the second emitter connecting line is increased to prevent the collector current from being shunted to the first emitter connecting line,
b) Overcoming this, the voltage induced by the collector current shunted to the first emitter connection line is also induced in the same direction in the base connection line by the action of the common mode reactor, so they cancel each other out when viewed from the base drive circuit side. In addition, the base drive signal is prevented from fluctuating, and c) the base drive circuit is in the common mode as viewed from the side, so that the base drive condition does not change at all. In this way, the parallel transistors are prevented from malfunctioning.

[0010]

1 is a circuit diagram showing a first embodiment of the present invention. In FIG. 1, a DC power supply 2, a load 3, a base drive circuit 4, a collector connection line 5, a base connection line 6, a first
The names, uses, and functions of the emitter connection line 7, the second emitter connection line 8, the first transistor 11, the second transistor 12, and the third transistor 13 are the same as those in the conventional circuit described above with reference to FIG. , These explanations are omitted.

In the circuit of the first embodiment shown in FIG. 1, the wiring for passing the base drive signal of the adjacent transistor, that is, the first wiring
One winding of the first common mode reactor 21 is inserted in the first emitter connection line 7 that connects the transistor 11 and the second transistor 12, and the same first transistor 11 and second transistor 12 are connected. This second common mode reactor 2 is connected to the second emitter connection line 8
Insert the other winding of 1. Similarly, the adjacent second
The windings of the second common mode reactor 22 are also inserted in the first emitter connection line 7 and the second emitter connection line 8 that connect the transistor 12 and the third transistor 13. With such a configuration, for example, even if the collector current I _C is shunted to the first emitter connection line 7, the collector current I _C flows only to the second emitter connection line 8 due to the reason described above, and the first emitter connection line 8 is connected. It is possible to prevent the shunt to the line 7. Therefore, it is possible to avoid the possibility that the base drive signal changes. When a freewheel diode is connected in antiparallel to a transistor, it is possible to avoid that the reverse recovery current flowing in the freewheel diode affects the base drive signal for the same reason as above. I can.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention. In the second embodiment circuit shown in FIG.
The first core 31 is used in place of the first common mode reactor 21 shown in the circuit of the first embodiment, and the second core is used.
Although the second iron core 32 is used instead of the common mode reactor 22, the other parts are the same as those of the first embodiment circuit of FIG. 1, and therefore the description of the same parts will be omitted.
The first iron core 31 and the second iron core 32 used in the circuit of the second embodiment are formed by winding, for example, a directional silicon steel strip in an annular shape, and collectively forming the first emitter connecting line 7 and the second emitter connecting line 8 together. The hole at the center of the annular core is made to penetrate. With such a configuration, the operation becomes the same as that of the common mode reactor described above.

[0013]

When a plurality of transistors are connected in parallel, conventionally, a first emitter connection line for supplying a base drive signal and a second emitter connection line for supplying a collector current are provided to each emitter of the transistors. Since wiring was done separately, the base current fluctuated due to the collector current, which could cause the transistor to malfunction.In this invention, however, the base connection connecting the bases of the transistors together A common mode reactor is inserted between the line and the above-mentioned first emitter connecting line to positively prevent the collector current from shunting to the first emitter connecting line. As a result, the base drive signal is not affected by the collector current, and it is possible to avoid the problem that the parallel transistors are erroneously turned on or off. In addition, instead of inserting the common mode reactor,
The same effect can be obtained by passing the first base connecting line and the first emitter connecting line together through the iron core having the through hole. In addition, when a freewheel diode is connected in parallel to a parallel transistor, the effect that the base drive signal fluctuates due to the reverse recovery current flowing through this freewheel diode and the transistor malfunctions can be similarly avoided. can get.

[Brief description of drawings]

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

FIG. 2 is a circuit diagram showing a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a conventional example of a circuit in which a plurality of transistors are arranged in parallel and a common base drive signal is supplied to them.

FIG. 4 is a circuit diagram illustrating a defect of the conventional circuit shown in FIG.

FIG. 5 is a circuit diagram illustrating another problem of the conventional circuit shown in FIG.

[Explanation of symbols]

2 DC power supply 3 Load 4 Base drive circuit 5 Collector connection line 6 Base connection line 7 First emitter connection line 8 Second emitter connection line 11 First transistor 12 Second transistor 13 Third transistor 17 Wiring of first emitter connection line 7 Inductance 18 Wiring of the second emitter connection line 8 Inductance 19 Free wheel diode 21 First common mode reactor 22 Second common mode reactor 31 First iron core 32 Second iron core I _B1 Base forward bias current I _B2 Base reverse bias current I _C transistor Collector current I _D Reverse recovery current of freewheel diode

Claims (2)

[Claims] 1. The collectors of a plurality of transistors are commonly connected by a collector connection line, and the emitters of the plurality of transistors are commonly connected to the same emitters as a first emitter connection line that connects the emitters in common. A second emitter connection line is provided, each base is commonly connected by the base connection line, and a base drive circuit that supplies a common base drive signal to each transistor is connected to the emitter connection line and the base connection line. In a parallel transistor, one of the windings of a common mode reactor having two sets of mutually insulated windings in a common iron core is inserted into the base connection line connecting adjacent transistors, and
A base driving signal supply circuit for parallel transistors, characterized in that the other winding of the common mode reactor is inserted into the first emitter connection line connecting the same adjacent transistors. 2. The collectors of a plurality of transistors are commonly connected by a collector connection line, and the emitters of the plurality of transistors are commonly connected to the same emitters as the first emitter connection line for connecting the emitters in common. A second emitter connection line is provided, each base is commonly connected by the base connection line, and a base drive circuit that supplies a common base drive signal to each transistor is connected to the emitter connection line and the base connection line. In the parallel transistor, the base connection line and the first emitter connection line that connect adjacent transistors to each other are bundled together, and the bundled line is passed through the through hole of the iron core having the through hole. And a base drive signal supply circuit for the parallel transistor.