JPH0819246A - Parallel connection circuit of semiconductor switch elements - Google Patents

Abstract

PURPOSE:To balance shared currents of a plurality of semiconductor switching devices when the devices are connected in parallel to each other without a selection work which makes the switching speeds of the respective devices uniform and without series connections of reactors and the respective devices. CONSTITUTION:A plurality of semiconductor switching devices and a gate driving circuit 4 common to the respective switching devices are provided. The respective semiconductor switching devices are connected in parallel to each other. When the gate driving circuit 4 is connected to the gates of the respective semiconductor switching devices with separated wires, separated common mode coils are inserted into respective circuits with which the gate driving circuit 4 is connected to the gates of the semiconductor switching devices. Or, respective lines with which the gate driving circuit 4 is connected to the gates of the semiconductor switching devices are separately made to pass through the piercing holes of cores which have piercing holes at their centers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parallel connection circuit for semiconductor switching devices, which is used when semiconductor switching devices operating at high speed are connected in parallel.

[0002]

2. Description of the Related Art FIG. 4 is a circuit diagram showing a conventional example in which semiconductor switching elements operating at high speed are connected in parallel and operated simultaneously. In this conventional circuit, collector terminals C1 and C2 of, for example, two insulated gate bipolar transistors (hereinafter abbreviated as IGBTs) 1 and 2 as a high-speed operation semiconductor switching element are coupled to each other and connected to a positive electrode side P of a DC power source. Then, the main emitter terminals E1 and E2 are coupled and connected to the negative electrode side N of the DC power supply, thereby forming a parallel connection circuit of the IGBT. A snubber circuit 3 is provided in these IGBTs 1 and 2.
Are connected in parallel to alleviate the surge voltage generated during switching operation.

The terminal G0 of the gate drive circuit 4 is connected to the gate terminal G1 of the IGBT1 via a gate resistor 5, and this terminal G0 is a separate wire via a gate resistor 6 to I.
It is connected to the gate terminal G2 of the GBT2. Further, the terminal E0 of the gate drive circuit 4 is connected to the auxiliary emitter terminal EX of the IGBT1, and the terminal E0 is connected to the auxiliary emitter terminal EY of the IGBT2. Thus, the two IGBTs 1 and 2 are simultaneously turned on / off in response to the gate current output by the gate drive circuit 4.

FIG. 5 is an equivalent circuit diagram showing a circuit equivalent to the conventional circuit of FIG. In this equivalent circuit, L _X1 is the auxiliary emitter terminal EX and the main emitter terminal E of the IGBT 1.
1 is a wiring inductance between L1 and L _Y2 is a wiring inductance between the auxiliary emitter terminal EY of the IGBT 2 and the main emitter terminal E2, and L _N is a wiring inductance between the main emitter terminal E1 and the main emitter terminal E2. Yes,
L ₀₁ is the wiring inductance between the gate terminal G 1 of the IGBT 1 and the gate drive circuit terminal G 0, and L ₀₂ is the IGBT 2
Is a wiring inductance between the gate terminal G2 and the gate drive circuit terminal G0, L _0X is a wiring inductance between the auxiliary emitter terminal EX of the IGBT 1 and the gate drive circuit terminal E 0, and L _0Y is an auxiliary emitter terminal E of the IGBT 2.
Each represents the wiring inductance between Y and the gate drive circuit terminal E0. C ₁ represents the gate-emitter capacitance of the IGBT ₁ and C ₂ represents the gate-emitter capacitance of the IGBT 2.

Since the gate drive circuit 4 common to the IGBTs 1 and 2 gives a turn-off command to both at the same time, both IG
If the collector current decrease rate BT1,2 are the same, the voltage V _X1 generated in the inductance L _X1 described above, since is equal to the voltage V _Y2 generated in the inductance L _Y2,
No current flows in the closed circuit composed of the auxiliary emitter terminal EX, the auxiliary emitter terminal EY, the main emitter terminal E2, and the main emitter terminal E1 in FIG. In the equivalent circuit of FIG. 5,
The current I _E = 0 flowing in the closed circuit constituted by L _X1 , L _N , L _Y2 , L _0Y and L _0X . If the current I _E is zero, the voltage V _0X generated by the inductance L _0X is zero, and the voltage V _0Y generated by the inductance L _0Y is also zero. Therefore IGBT
The discharge speed of the gate-emitter capacitance C ₁ of ₁ is a value determined by the resistance value of the gate resistor 5, the inductances L ₀₁ and L _0X, and the gate drive circuit 4, and the gate-emitter electrostatic capacitance of the IGBT 2 is The discharge rate of the capacitance C ₂ is a value determined by the resistance value of the gate resistor 6, the inductances L ₀₂ and L _0Y, and the gate drive circuit 4. That is, IGBTs 1 and 2
The effect of connecting and in parallel does not appear.

However, there is a difference in the turn-off speeds of the IGBTs 1 and 2, and for example, the IGBT 1 is the IGBT 2
It is assumed that the collector current at turn-off is larger and the current reduction rate is larger than that. The relationship at this time is Equation 1 below.

[0007]

[Equation 1]

At this time, the voltage generated in the wiring inductance L _X1 and the voltage generated in the wiring inductance L _Y2 are not the same, and the magnitude relationship is as shown in the following mathematical formula 2. This potential difference V _E is expressed by Equation 3.

[0009]

[Equation 2]

[0010]

(Equation 3)

Here, the wiring inductance L _0X between the gate drive circuit terminal E0 and the auxiliary emitter terminals EX and EY,
Since the wiring inductance L _N between the main emitter terminals E1 and E2 is extremely small compared to L _0Y , this L _N can be ignored. If L _N is neglected, the above-mentioned potential difference V _E is applied evenly to the wiring inductances L _0X and L _0Y . That is, the following formula 4 is established.

[0012]

[Equation 4]

[0013] Here, when the voltage of the gate-emitter capacitance C ₁ of the discharge path of IGBT1 and V _C1, the voltage V _C1 is expressed by Equation 5 below, the gate-emitter capacitance C of the IGBT2 The voltage V _C2 of the _second discharge path is expressed by Equation 6 below. However, V _G is the voltage of the gate drive circuit 4.

[0014]

(Equation 5)

[0015]

(Equation 6)

As is clear from these equations 5 and 6,
Due to the difference voltage V _E , the gate-emitter capacitance C ₁ of the IGBT 1 slows down the discharge, and the capacitance C ₁ discharges faster. In the IGBT, since the discharge speed of the gate-emitter capacitance and the turn-off speed are proportional to each other, the IGBT1 having a large current acts in the direction of decreasing the speed at the turn-off, and the IGBT2 having a small current increases the speed at the turn-off. It will act in the direction of doing. That is, this action promotes current imbalance when the IGBTs connected in parallel are turned off. Further, since this difference voltage V _E also acts in the direction of charging the gate-emitter capacitance, it causes a malfunction such as erroneously turning on the IGBT.

FIG. 6 is a graph showing changes in the current of each element when the semiconductor switch element is turned off in the conventional circuit of FIG. 4, in which the horizontal axis represents time and the vertical axis represents collector current. There is. In this graph, both the collector current I _C1 of the IGBT1 and the collector current I _{C2 of the} IGBT2 are shown by solid lines, and the current imbalance is finally expanded to an amount indicated by Z by the difference voltage V _E. There is.

When the IGBT is turned on, the current direction and the voltage direction are simply opposite to those in the case described above, so that the same operation occurs and the same problem occurs.

[0019]

As described above, when a plurality of semiconductor switching elements are connected in parallel as in the conventional case, a difference occurs in the electromotive force generated in the wiring inductance between the auxiliary emitter terminal and the main emitter terminal. Therefore, due to this difference voltage, the current imbalance when the semiconductor switch element operates is amplified. Therefore, in order to avoid the occurrence of such a problem, it is necessary to select and combine the semiconductor switching elements so that the switching speeds of the semiconductor switching elements are uniform, which requires time and effort for selection and combination, which makes the device expensive. There is a defect.

There is also a method of connecting a sharing reactor to the elements in series in order to balance the sharing current of each element, but in order to balance the sharing current at the time of switching, the sharing reactor must be connected inside the snubber circuit. Therefore, the jumping voltage at the time of switching becomes large, and the operating voltage must be kept lower than the withstand voltage of the element, which increases the number of elements connected in series and enlarges the device. There is also a problem that it will happen. Further, a high breakdown voltage element generally has a large saturation voltage and poor switching characteristics, so that the generated loss of the element increases and the conversion efficiency of the device decreases.

Therefore, an object of the present invention is to share the switching time without connecting a plurality of semiconductor switching elements in parallel without performing a sorting operation to make the switching speeds of the elements uniform or connecting a reactor to each element in series. To balance the current.

[0022]

In order to achieve the above-mentioned object, a parallel connection circuit for semiconductor switching elements according to the present invention comprises:
The semiconductor switch device includes a plurality of semiconductor switch elements and a drive circuit common to the semiconductor switch elements, the semiconductor switch elements are connected in parallel to each other, and the drive circuit and the control valve of the semiconductor switch element are connected to each other In a parallel connection circuit of semiconductor switch elements, in which a control electric wire for reciprocating a drive current for operating a switch element is separately provided for each semiconductor switch element, the control electric wire connecting the drive circuit and the control valve of the semiconductor switch element For each of the
A separate common mode coil shall be inserted.

Alternatively, an iron core having a through hole at the center is provided, and each of the control wires connecting the drive circuit and the control valve of the semiconductor switch element is passed through a separate through hole of the iron core. .

[0024]

[Function] When a plurality of semiconductor switching elements are connected in parallel and an operation signal is given from a common gate drive circuit to perform a switching operation at the same time, a wiring inductance between the main emitter terminal and the auxiliary emitter terminal of each element occurs. The differential voltage of the electromotive force is applied to the circuit that connects the gate drive circuit terminal and the auxiliary emitter terminal, but in the present invention, the control wire that connects the gate drive circuit and the control valve of each semiconductor switch element is used. Since a separate common mode coil or iron core is inserted, when a voltage difference is applied to the auxiliary emitter terminal circuit, an equivalent voltage is applied to the circuit connecting the gate drive circuit and the gate terminal. Occurs through.

However, in the path where the gate-emitter capacitance is discharged, the voltage on the emitter side and the voltage on the gate are applied with opposite polarities and thus cancel each other. Therefore, it is possible to avoid the phenomenon that the current imbalance of each element is increased by the difference voltage of the electromotive force generated in the wiring inductance between the auxiliary emitter terminal and the main emitter terminal during switching.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram showing a first embodiment of the present invention. This first embodiment circuit is a gate drive circuit terminal G
0 and a circuit for connecting the gate terminal G1 of the IGBT1 and
The common mode coil 10 is inserted in the circuit that connects the gate drive circuit terminal E0 and the auxiliary emitter terminal EX of the IGBT1, and the gate drive circuit terminal G0 and the IGBT.
The circuit for connecting the gate terminal G2 of T2 and the circuit for connecting the gate drive circuit terminal E0 and the auxiliary emitter terminal EY of the IGBT2 are inserted with the common mode coil 20. Are different, but everything else is the same.

FIG. 2 is an equivalent circuit diagram showing a circuit equivalent to the circuit of the first embodiment shown in FIG. 1, and the gate-emitter capacitances C ₁ and C ₂ shown in this equivalent circuit and the wiring. Inductances L _X1 , L _Y2 , L _N , L _0X , L _0Y , L ₀₁ , and L ₀₂ , voltages V _X1 and V _Y2 , and collector currents I _C1 and I _C2.
5 is the same as the case of the equivalent circuit of the conventional example circuit described above with reference to FIG.

Even in the equivalent circuit of FIG. 2, the IGBT 1 is I
If the current at turn-off and the current decrease rate are larger than those of the GBT2, the above-described relationships of Formulas 1, 2 and 3 are established. Here, the exciting inductance of the common mode coils 10 and 20 is the wiring inductance L _0X ,
Since it is much larger than L _0Y or L _N , the differential voltage V _E described in Formula 3 is applied equally to the common mode coil 10 and the common mode coil 20 as shown in Formula 7. . Here, V ₁₁ is the common mode coil 10
Is a voltage on the side of the auxiliary emitter terminal EX, and V ₂₁ is a voltage on the side of the auxiliary emitter terminal EY.

[0029]

(Equation 7)

At this time, the same voltage V ₁₂ appears on the gate terminal G1 side of the common mode coil 10, and the voltage V ₂₂ also appears on the gate terminal G2 side of the common mode coil 20. The voltage V _C1 of the discharge path of the gate-emitter capacitance C ₁ of the IGBT ₁ is represented by the following mathematical formula 8, and the IGBT
The voltage V _C2 of the discharge path of the gate-emitter capacitance C ₂ of ₂ is represented by the following formula 9.

[0031]

(Equation 8)

[0032]

[Equation 9]

As is clear from this relationship, the voltage V _E / 2, which has made the speed of discharging the gate-emitter capacitance unbalanced, cancels out on the auxiliary emitter terminal side and the gate terminal side of the common mode coil. You can see that it is done. Therefore, by inserting the common mode coil, the phenomenon of increasing the current imbalance at turn-off can be avoided. Further, since this difference voltage acts in the direction of charging the gate-emitter capacitance, there is a risk of erroneous turn-on in the past, but the charging voltage also disappears and malfunction can be resolved.

The dotted line shown in the above-mentioned graph of FIG. 6 shows the effect when the common mode coil is inserted, and the imbalance between the collector current I _C1 of the IGBT ₁ and the collector current I _{C2 of the} IGBT 2 is eliminated. It means that it is being done. At turn-on, the operation is the same except that the current and voltage directions are reversed. FIG. 3 is a circuit diagram showing a second embodiment of the present invention, but this second embodiment circuit does not have the common mode coil 10 and the common mode coil 20 in the first embodiment described above, but penetrates in the center. An iron core 30 having a hole and an iron core 40 are installed. The electric wire connecting the gate drive circuit terminal G0 and the gate terminal G1 of the IGBT1 and the electric wire connecting the gate drive circuit terminal E0 and the auxiliary emitter terminal EX of the IGBT1 are collectively passed through the through hole of the iron core 30 to form a gate. Drive circuit terminal G0 and IGBT2
The electric wire connecting the gate terminal G2 and the electric wire connecting the gate drive circuit terminal E0 and the auxiliary emitter terminal EY of the IGBT 2 are collectively passed through the through hole of the iron core 40.
With such a configuration, the iron core 30 and the iron core 40 have the common mode coil 10 and the common mode coil 20 described above.
You can get the same effect as.

[0035]

According to the present invention, when a plurality of semiconductor switch elements are connected in parallel and simultaneously turned on and off, it is not necessary to strictly select the switching speeds of the respective semiconductor switch elements, or Even if the current sharing reactor is not connected in series to each semiconductor switch element, current imbalance during switching can be avoided. Therefore, various effects described below can be obtained. a) Since the selection condition of the semiconductor switch element can be relaxed,
The cost of the device is reduced, and the device can be constructed inexpensively. b) It is possible to use an element having a lower breakdown voltage than in the case where the current sharing reactor is connected to the element in series. Low breakdown voltage elements generally have a lower saturation voltage than high breakdown voltage elements and have good switching characteristics, so the loss generated can be reduced.
The conversion efficiency of the device can be improved. c) The common mode coil and the iron core have a function of reducing the noise current that flows due to the abrupt potential change generated when the semiconductor switch element performs the switching operation, so that the malfunction of the control circuit is prevented and the reliability of the device is improved. Contribute.

[Brief description of drawings]

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

FIG. 2 is an equivalent circuit diagram showing a circuit equivalent to the circuit of the first embodiment of FIG.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention.

FIG. 4 is a circuit diagram showing a conventional example in which semiconductor switching devices operating at high speed are connected in parallel and operated simultaneously.

5 is an equivalent circuit diagram showing a circuit equivalent to the conventional circuit of FIG.

6 is a graph showing changes in current of each element when the semiconductor switch element is turned off in the conventional circuit of FIG.

[Explanation of symbols]

1, 2 IGBT 3 Snubber circuit 4 Gate drive circuit 5, 6 Gate resistance 10, 20 Common mode coil 30, 40 Iron core I _C1 Collector current of IGBT 1 I _C2 Collector current of IGBT 2 L ₀₁ Wiring inductance of gate terminal side circuit of IGBT 1 ₀₂ Wiring inductance of the circuit on the gate terminal side of the _IGBT2 L _0X Wiring inductance of the circuit on the auxiliary emitter terminal side of the _IGBT1 L _0Y Wiring inductance of the circuit on the auxiliary emitter terminal side of the _IGBT2 L _N Wiring inductance of the circuit connecting the main emitter terminals L _X1 Main of the IGBT1 Inductance between the main emitter and auxiliary emitter of the _Y2 IGBT2.

Claims (2)

[Claims] 1. A plurality of semiconductor switch elements and a drive circuit common to each of these semiconductor switch elements, wherein the semiconductor switch elements are connected in parallel to each other, and the drive circuit and the control valve for the semiconductor switch elements are connected to each other. In a parallel connection circuit of semiconductor switch elements, each of which is provided with a control electric wire for connecting and reciprocating a drive current for operating the semiconductor switch element, wherein the drive circuit and the control valve of the semiconductor switch element are connected to each other. A parallel connection circuit for semiconductor switching elements, wherein a separate common mode coil is inserted into each of the control wires to be connected. 2. A plurality of semiconductor switch elements and a drive circuit common to each of the semiconductor switch elements, wherein the semiconductor switch elements are connected in parallel with each other, and the drive circuit and the control valve for the semiconductor switch elements are connected to each other. In a parallel connection circuit of semiconductor switching elements in which a control electric wire for connecting and reciprocating a driving current for operating the semiconductor switching element is separately provided for each semiconductor switching element, an iron core having a through hole in a central portion is provided, and A parallel connection circuit for semiconductor switch elements, wherein each of the control wires connecting the drive circuit and the control valve of the semiconductor switch element is passed through a separate through hole of the iron core.