JP2006222593A - Apparatus and method of driving voltage drive type semiconductor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that it is difficult to set a time delay by the influence of the characteristic variation of a voltage drive type semiconductor device or a temperature characteristic since the switching of a drive is carried out by a plurality of drive circuits in the driving device of a conventional voltage drive type semiconductor element. <P>SOLUTION: A driving device 10 of a voltage drive type semiconductor device of such an insulated gate bipolar transistor, as IGBT 1 detects the modulus dVge/dt of the time variation of the gate voltage Vge of this IGBT 1 at the time of turning on of the IGBT 1, and performs the drive control of the IGBT1 based on the detected modules dVge/dt of the time variation. At the time of the above turning on, a first zone S1 where the modulus dVge/dt of the time variation of the gate voltage Vge becomes one or more threshold values Vth 1 and a second zone S2 where the modulus dVge/dt of the time variation of the gate voltage Vge becomes less than one threshold Vth 1 exists continued to the first zone S1. It is controlled so that the gate resistance value r in the second zone S2 may get lower values than the gate resistance value r in the first zone S1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a voltage-driven semiconductor element driving apparatus and method capable of reducing a turn-on loss while reducing a surge voltage generated at turn-on.

An IGBT (Insulated Gate Bipolar Transistor), a MOSGTO (Metal Oxide Gate Turn-Off Thyristor), and the like are so-called voltage-driven semiconductor elements that can control a current by a voltage applied to an insulated gate. Since the driving power is small, it is widely used for power supplies, inverters and the like.
At the time of turn-on in such a voltage-driven semiconductor element, if the gate resistance value is small, the collector current has a large rate of change over time, and a large surge voltage is generated. On the other hand, if the gate resistance value is large, the collector current is large. The rate of time change of the time becomes small, and the turn-on loss increases.

In order to solve such a problem, for example, as described in Patent Document 1, the surge voltage is reduced by setting the gate resistance value high at the start of turn-on and reducing the time change rate of the collector current. Then, drive control is performed to reduce the turn-on loss by switching the gate resistance to a low resistance value after a lapse of a certain time from the start of turn-on.
In this drive control, a plurality of drive circuits for voltage-driven semiconductor elements are prepared, and one drive circuit and the voltage-driven semiconductor element are connected via a high resistance gate resistor, A voltage-driven semiconductor element is connected via a gate resistor having a low resistance value, and the drive by one drive circuit and the drive by the other drive circuit are switched using a delay circuit, The value was switched.
In addition, switching between driving by one driving circuit and driving by the other driving circuit is performed by providing a detection circuit for the collector-emitter voltage Vce, the gate voltage Vge, and the collector current Ice, and detecting these values. There are also methods based on this.
JP-A-9-46201

However, as in the technique described in Patent Document 1 described above, when switching of driving by a plurality of driving circuits is performed using a delay circuit, it is affected by variations in characteristics of voltage-driven semiconductor elements and temperature characteristics. Therefore, since the delay time set by the delay circuit varies, it is difficult to set the delay time.
Further, in the detection circuit for detecting the collector-emitter voltage Vce, a high withstand voltage characteristic is required for the Zener diode included in the detection circuit, so that it is necessary to connect a plurality of Zener diodes in series, and the circuit scale Will become bigger. Furthermore, since the voltage Vce between the collector and the emitter is accompanied by voltage switching noise of another phase, there is a possibility that the voltage Vce between the collector and the emitter is erroneously detected.
In addition, when the gate voltage Vge is a detection target, the gate threshold voltage of the voltage-driven semiconductor element (the gate voltage at which the collector current Ice starts flowing) has temperature characteristics, and the temperature characteristics are different for each element. It becomes difficult to set the drive switching threshold in the gate voltage Vge detection circuit.

When the collector current Ice is to be detected, it is necessary to provide a sensing element for detecting the collector current Ice in parallel with the voltage-driven semiconductor element. However, a current is supplied to the voltage-driven semiconductor element and the sensing element. As a result, the detection accuracy of the collector current Ice at turn-on or turn-off deteriorates. Further, in a circuit in which a plurality of voltage-driven semiconductor elements are connected in parallel, the collector current Ice may not flow evenly through the plurality of voltage-driven semiconductor elements at turn-on or turn-off. Depending on the characteristics, there is a problem that the switching timing of the gate resistance value is shifted.
Further, the technique described in Patent Document 1 requires as many gate drive circuits as the number of gate resistors to be switched, which increases the circuit scale and provides a current drive capability for each gate drive circuit. This makes it difficult to reduce the size of the apparatus.

A voltage-driven semiconductor device driving apparatus and method for solving the above-described problems have the following characteristics.
That is, the voltage-driven semiconductor element driving device according to claim 1, wherein when the voltage-driven semiconductor element is turned on, the time change rate of the gate voltage of the voltage-driven semiconductor element is detected, and the detected gate is detected. The drive control of the voltage-driven semiconductor element is performed based on the time change rate of the voltage.
As a result, unlike the case where drive control is performed using a delay circuit, high-precision drive control can be performed without being affected by variations in characteristics and temperature characteristics of voltage-driven semiconductor elements. Can be easily set.

According to a second aspect of the present invention, at the time of turn-on, the first period in which the time change rate of the gate voltage is a certain value or more, and the time change rate of the gate voltage following the first period is less than a certain value. And the gate resistance value in the second section is controlled to be lower than the gate resistance value in the first section.
As a result, unlike the case where the gate resistance value is switched using a delay circuit, high-precision control can be performed without being affected by variations in characteristics of the voltage-driven semiconductor element and temperature characteristics. It is possible to easily set the value switching timing.
Furthermore, since high-precision control is possible, accurate switching control can be performed even when the time of the second section is shortened, and high-speed control is possible.
In addition, since the drive device can be configured by using an element having a low withstand voltage characteristic, the circuit scale can be reduced, and it is difficult to be affected by the switching noise of other phases, so that the occurrence of erroneous detection can be suppressed.

According to a third aspect of the present invention, the voltage-driven semiconductor element driving device includes a first gate resistor, a second gate resistor provided in parallel with the first gate resistor, and a first gate resistor. A first switching element connected to the second switching element and a second switching element connected to a second gate resistor, wherein the first section includes one of the first switching element and the second switching element. Is turned on, and both the first switching element and the second switching element are turned on in the second section.
Thereby, a drive circuit etc. can be reduced in size compared with the case where a gate drive circuit is provided for every gate resistance.

According to a fourth aspect of the present invention, the time change rate of the gate voltage of the voltage-driven semiconductor element is detected when the voltage-driven semiconductor element is turned on, and the time change rate of the gate voltage at the turn-on becomes a certain value or more. The gate resistance value in the second section where the time change rate of the gate voltage following the first section is less than a certain value is controlled to be lower than the gate resistance value in the first section.
As a result, unlike the case where the gate resistance value is switched using a delay circuit, high-precision control can be performed without being affected by variations in characteristics of the voltage-driven semiconductor element and temperature characteristics. It is possible to easily set the value switching timing.
Furthermore, since high-precision control is possible, accurate switching control can be performed even when the time of the second section is shortened, and high-speed control is possible.
In addition, since the drive device can be configured by using an element having a low withstand voltage characteristic, the circuit scale can be reduced, and it is difficult to be affected by the switching noise of other phases, so that the occurrence of erroneous detection can be suppressed.

According to the present invention, high-precision drive control of a voltage-driven semiconductor element can be performed, control conditions can be easily set, and high-speed control can be performed.
In addition, the circuit scale of the driving device can be reduced and the occurrence of erroneous detection can be suppressed.

  Next, modes for carrying out the present invention will be described with reference to the accompanying drawings.

First, a schematic configuration of a voltage-driven semiconductor element driving device according to the present invention will be described.
As shown in FIG. 1, the drive device 10 of the IGBT 1 that is a voltage-driven semiconductor element includes a switching element Q 1 and Q 3 for turning on the IGBT 1, a switching element Q 2 for turning off the IGBT 1, and a gate voltage Vge of the IGBT 1. A gate voltage change rate detection circuit 2 for detecting a change rate dVge / dt, a comparison circuit 3 for comparing a time change rate dVge / dt of the gate voltage Vge with a preset threshold value Vth1, and the turn-on switching A control circuit 4 that performs on / off control of the elements Q1 and Q3 and the switching element Q2 for turn-off, a driving power source 6 for the IGBT 1, and gate resistances R1, R2, and R3 of the IGBT 1 are provided.
A diode D is connected in parallel to the IGBT 1.

  The gate resistor R1 and the gate resistor R3, and the gate resistor R2 and the gate resistor R3 are connected in series, the gate resistor R1 and the gate resistor R2 are connected in parallel, and the switching element Q3 includes the gate resistor R1 and the gate resistor. The switching elements Q1 and Q2 are connected to the IGBT 1 through the gate resistance R2 and the gate resistance R3.

The control circuit 4 controls the switching elements Q1 and Q2 to be turned on and off at turn-on and turn-off, respectively, and controls the switching element Q3 from being turned on and off according to the output from the comparison circuit 3 at the time of turn-on. Do.
The on / off control of the switching element Q3 in the control circuit 4 is performed based on whether or not the time change rate dVge / dt of the gate voltage Vge input to the comparison circuit 3 is larger than the threshold value Vth1. That is, when a comparison result indicating that the time change rate dVge / dt is larger than the threshold value Vth1 is output from the comparison circuit 3, the switching element Q3 is turned off, and the time change rate dVge / dt is less than the threshold value Vth1. When the comparison result is output, the switching element Q3 is turned on.

The gate voltage change rate detection circuit 2 is composed of, for example, a CR differentiation circuit using a resistor and a capacitor. Further, as shown in FIG. 2, the gate voltage change rate detection circuit 2 can be configured by a differentiation circuit using an operational amplifier.
For example, six sets of the drive device 10 and the IGBT 1 configured as described above are provided, and an inverter for driving a three-phase motor is configured.

Next, the operation when the driving device 10 is turned on will be described with reference to the timing chart shown in FIG.
At the start of turn-on (time t1), an IGBT turn-on signal is first input to the control circuit 4 from the outside, and the switching element Q1 is turned on by the control circuit 4.

When the switching element Q1 is turned on, the IGBT 1 is charged in a state where the gate resistance value r of the IGBT 1 is a value obtained by adding the resistance value r2 of the gate resistance R2 and the resistance value r3 of the gate resistance R3.
That is, the gate resistance value r at the start of turn-on is “r = r2 + r3”.

  When charging of the IGBT 1 is started, the gate voltage Vge increases, and the time change rate dVge / dt of the gate voltage Vge detected by the gate voltage change rate detection circuit 2 exceeds the threshold value Vth1, so that the switching element Q3 is controlled. It is turned off by the circuit 4.

On the other hand, the gate voltage Vge rises from the start of turn-on, but the collector current Ice of the IGBT 1 does not flow until time t2 until the gate voltage Vge reaches the preset threshold value Vth2, and when the gate voltage Vge exceeds the threshold value Vth2 Start flowing.
The collector current Ice rises from the beginning of flow, and eventually settles to a steady value at time t3.

This period from the turn-on start time t1 to the time t3 when the collector current Ice becomes a steady value is referred to as a first section S1.
In the first section S1, the switching element Q3 is turned off, and only the switching element Q1 is on.

  In the first section S1, when the time change rate dIce / dt of the collector current Ice in the rising process is increased, a recovery surge voltage is generated in the diode D connected in parallel with the IGBT 1. When the recovery surge voltage is generated, the diode D and the IGBT 1 may be destroyed, or malfunction may be caused by noise generated due to the surge voltage.

  Accordingly, in the present control device 10, the gate resistance R2 and the gate resistance R3 are connected in series, and the gate resistance value r is set to a large value of r2 + r3, so that the time change rate dIce / dt of the collector current Ice at the time of rise is obtained. This reduces the generation of recovery surge voltage.

After time t3 when the collector current Ice becomes a steady value, the time change rate of the collector voltage Vce starts to decrease.
At this time, since the collector-gate capacitance Ccg of the IGBT 1 is charged, the gate voltage Vge becomes a constant value, the time change rate dVge / dt of the gate voltage Vge becomes 0, and becomes a value equal to or less than the threshold value Vth1.

After time t3, when the time rate of change dVge / dt of the gate voltage Vge becomes a value equal to or lower than the threshold value Vth1, the switching element Q3 is turned on by the control circuit 4, and the switching element Q1 and the switching element Q3 are both turned on. Become.
In this state, the gate resistance value r is “r = 1 / ((1 / r1) + (1 / r2)) + r3”. Here, r1 is the resistance value of the gate resistor R1.

After the time t3, when the collector voltage Vce decreases and reaches the saturation voltage, the gate voltage Vge starts to rise again. However, the time when the collector voltage Vce reaches the saturation voltage and the gate voltage Vge starts to rise is time t4. A period from time t3 to time t4 is referred to as a second section S2.
In the second section S2, the gate resistance value r is r = 1 / ((1 / r1) + (1 / r2)) + r3, which is smaller than the gate resistance value r = r2 + r3 in the first section. It is a value.

  As described above, in the second section S2, the turn-on is performed with a gate resistance value r lower than that in the first section S1, so that the second section S2 is turned on with the same gate resistance value r as that in the first section S1. The time of the second section S2 can be shortened, and as a result, turn-on loss can be reduced.

  Next, after the collector voltage Vce reaches the saturation voltage (after time t4), the gate voltage Vge starts increasing again. The gate voltage Vge rises until time t5 when the gate voltage Vge reaches the voltage of the driving power supply 6, and becomes constant after the gate voltage Vge reaches the voltage of the driving power supply 6.

  After time t4, while the gate voltage Vge is rising, the time change rate dVge / dt of the gate voltage Vge exceeds the threshold value Vth1, so the switching element Q3 is turned off, and the gate voltage Vge is the voltage of the driving power supply 6 After time t5 when reaching and becomes constant, the time change rate dVge / dt of the gate voltage Vge becomes equal to or lower than the threshold value Vth1, so that the switching element Q3 is turned on. In addition, the time after t4 (including time t5 and after) is referred to as a third section S3.

In the third section S3, since both the collector current Ice and the collector voltage Vce are in a steady state showing steady values, the gate resistance value r, that is, the on / off state of the switching element Q3 depends on the recovery surge voltage and turn-on loss. It does not relate to the size of.
Therefore, it does not matter whether the switching element Q3 is on-controlled or off-controlled.

  Here, when the gate resistance value r at turn-on is set to r = r2 + r3 through the first section S1 and the second section S2, and the gate resistance value is constant, the gate voltage Vge, the collector current Ice, the collector voltage Waveforms of Vce and turn-on loss P are shown in FIG.

  Further, the gate resistance value r at the time of turn-on is set to r = r2 + r3 in the first section S1, and in the second section S2, r = 1 / ((1 / r1) + () smaller than the value in the first section S1. FIG. 5 shows waveforms of the gate voltage Vge, the collector current Ice, the collector voltage Vce, and the turn-on loss P when the gate resistance value is switched by setting 1 / r2)) + r3.

According to FIG. 4 and FIG. 5, the magnitude of the peak value Ip of the collector current Ice indicating the recovery surge voltage is the same when the gate resistance value is constant and when the gate resistance value is switched.
On the other hand, the time tb of the second section S2 when the gate resistance value is switched as shown in FIG. 5 is shorter than the time ta of the second section S2 when the gate resistance value is constant as shown in FIG. It can be seen that is decreasing.

As described above, in the present driving device 10, the first section S1 and the second section are set so that the gate resistance value S2 in the second section S2 is smaller than the gate resistance value S1 in the first section S1. The gate resistance value r is switched between S2 and S2.
In this case, since the switching of the gate resistance value r is performed based on the time rate of change dVge / dt of the gate voltage Vge detected by the gate voltage change rate detection circuit 2, the switching is performed using a delay circuit. As described above, it is possible to perform highly accurate control without being affected by variations in the characteristics of the IGBT 1 and temperature characteristics, and it is possible to easily set the switching timing of the gate resistance value r.

That is, even if the absolute value of the gate voltage Vge varies due to the characteristic variation for each IGBT 1 or the influence of the temperature characteristic, the time change rate dVge / dt obtained by differentiating the gate voltage Vge is substantially constant. Setting of Vth1 becomes easy.
Furthermore, since control with high accuracy is possible, accurate switching control can be performed even when the time tb of the second section S2 is shortened, and high-speed control is possible.

The gate voltage change rate detection circuit 2 and the comparison circuit 3 are circuits for differentiating and comparing the gate voltage Vge, and the normal gate voltage Vge usually takes a value in the range of −15V to 15V or 0V to 15V. The gate voltage change rate detection circuit 2 and the comparison circuit 3 can also be configured using elements having low breakdown voltage characteristics (for example, 35 V or less), and the circuit scale can be reduced.
Further, the gate-emitter capacitance of the IGBT 1 is a huge capacitor of about 0.001 μF to 0.1 μF, and the gate voltage Vge is a voltage generated in this capacitive load. It is hard to be influenced by. Therefore, the gate voltage change rate detection circuit 2 can suppress the occurrence of erroneous detection.

In addition, the gate voltage Vge is flat in the second section S2 at the time of turn-on, but the gate voltage Vge at this time has variations in temperature characteristics and each IGBT1, and therefore the detection target is the gate voltage Vge. It is difficult to set a threshold value for.
However, since the time change rate dVge / dt of the gate voltage Vge is hardly affected by variations in temperature characteristics and for each IGBT1, it is easy to set the threshold value Vth1.

Further, when the gate resistance value r is switched based on the time rate of change dVge / dt, it is not necessary to provide a sensing element as in the case where the collector current Ice is a detection target, and the detection accuracy is deteriorated. Nor.
Furthermore, as shown in FIG. 6, even in a circuit in which a plurality of IGBTs 1 and IGBTs 1 ′ are connected in parallel, the switching timing does not deviate (in FIG. 6, the diode D is omitted).

Further, since the switching of the gate resistance value r is performed by switching the switching element Q3 on and off while the switching element Q1 is always on, as compared with the case where a gate driving circuit is provided for each gate resistance. The drive circuit can be reduced in size.
Further, since the time change rate dVge / dt of the gate voltage Vge at the turn-on basically shows a positive value, the gate voltage change rate detection circuit 2 for handling the signal can be configured with a single power source. Simplification and miniaturization can be realized.

  Further, in the present driving device 10, the gate resistance value r is set high in the first section S1, which is the initial stage of turn-on, and switching is performed slowly, and the gate resistance value r is set low in the second section S2 that follows. However, it is possible to perform switching in three stages.

That is, the first section S1 is divided into a section from time t1 to time t2 and a section from time t2 to time t3, and the gate resistance value r is set low in the section from time t1 to time t2 (switching). Switching is performed fast (by turning on the element Q3), and switching is performed slowly by setting the gate resistance value r high (turning off the switching element Q3) in the period from time t2 to time t3. In the second section S2, the switching element Q3 is turned on in the same way as in the case of two divisions, and fast switching is performed.
Thereby, the recovery surge voltage can be suppressed while shortening the turn-on time.

  However, when the switching divided into three stages is performed, the response time of the gate voltage change rate detection circuit 2, the comparison circuit 3, and the control circuit 4 in the first section S1 divided into two sections Due to the influence of the switching time of the switching element Q3, the switching timing of the switching element Q3 from the on state to the off state is delayed, and when the collector current Ice starts to change, switching is performed quickly, and the recovery surge voltage increases. There is a risk of ending up.

  On the other hand, when switching is performed in two stages, even if the switching timing from the state in which the switching element Q3 in the first section S1 is turned off to the state in which the second section S2 is turned on is delayed, The recovery surge voltage does not increase, and the drive device 10 is controlled in a stable direction.

It is a circuit diagram which shows the drive device of IGBT concerning this invention. 6 is a circuit diagram showing another embodiment of the gate voltage change rate detection circuit 2. FIG. It is a figure which shows the timing chart at the time of turn-on. It is a figure which shows the waveform of a gate voltage, a collector current, a collector voltage, and a turn-on loss at the time of setting the gate resistance value at the time of turn-on constant throughout a 1st area and a 2nd area. It is a figure which shows the waveform of a gate voltage, collector current, collector voltage, and a turn-on loss at the time of switching the gate resistance value at the time of turn-on so that the 2nd area may become smaller than a 1st area. It is a circuit diagram which shows the drive device at the time of connecting several IGBT in parallel.

Explanation of symbols

1 IGBT
2 Gate voltage change rate detection circuit 3 Comparison circuit 4 Control circuit R1, R2, R3 Gate resistance Q1, Q2, Q3 Switching element dVge / dt Time change rate (of gate voltage) Ice collector current Vge Gate voltage Vce Collector voltage P Turn-on loss

Claims (4)

A driving device for a voltage-driven semiconductor element,
When the voltage-driven semiconductor element is turned on, a time change rate of the gate voltage of the voltage-driven semiconductor element is detected, and drive control of the voltage-driven semiconductor element is performed based on the detected time change rate of the gate voltage. A drive device for a voltage-driven semiconductor element. At the time of turn-on, there is a first interval in which the time change rate of the gate voltage is equal to or greater than a certain value, and a second interval following the first interval in which the time change rate of the gate voltage is less than a certain value. ,
2. The voltage-driven semiconductor element driving device according to claim 1, wherein the gate resistance value in the second section is controlled to be lower than the gate resistance value in the first section. The voltage-driven semiconductor element driving device comprises:
A first gate resistor and a second gate resistor provided in parallel with the first gate resistor;
A first switching element connected to the first gate resistance, and a second switching element connected to the second gate resistance,
Either the first switching element or the second switching element is turned on in the first section, and both the first switching element and the second switching element are turned on in the second section. 3. The voltage driving type semiconductor device driving apparatus according to claim 1, wherein the driving device is a voltage driving type semiconductor device. When the voltage driven semiconductor element is turned on, the time change rate of the gate voltage of the voltage driven semiconductor element is detected,
A second interval in which the time change rate of the gate voltage is less than a constant value, following the first interval, rather than the gate resistance value in the first interval in which the change rate of the gate voltage at the turn-on time is a certain value or more. A method for driving a voltage-driven semiconductor element, characterized in that the gate resistance value is controlled to be low.

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