Drive circuit for a power semiconductor device

• US 20030180997A1
• Filed: 01/16/2003
• Published: 09/25/2003
• Est. Priority Date: 01/17/2002
• Status: Active Grant

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Ohi, Takeshi, Nakayama, Yasushi, Hashido, Ryuichi
• Granted Patent: US 6,967,519 B2
• Time in Patent Office: Days
• US Class Current: 438/200
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H03K 17/08128 in composite switches
• CPC Class Codes: H03K 17/168 in composite switches

Abstract

A drive circuit for a power semiconductor device includes: a sampling signal generating circuit for detecting that an input control signal instructs OFF and outputting a sampling signal at the time instant of start of a Miller period of time of an IGBT; a gate voltage detecting circuit for detecting a Miller voltage of the IGBE at the timing when the sampling signal is inputted and outputting, when the Miller voltage is equal to or larger than a threshold, an over-current detection signal; and a gate voltage controlling circuit for controlling, in response to the over-current detection signal, a gate voltage of the IGBT in such a way that the IGBT is turned OFF at slower speed than in the normal state. Thus, it is possible to suppress a surge voltage which is generated when the IGBT is turned OFF during the flow of an over-current.

Claims

1. A drive circuit for driving a power semiconductor device, comprising:

a switching circuit for receiving as its input an input control signal from the outside to carry out switching of ON/OFF of the power semiconductor device;

a sampling signal generating circuit for detecting the input control signal to output, when the input control signal commands OFF, a sampling signal substantially at the time instant of start of a Miller period of time of the power semiconductor device;

a gate voltage detecting circuit connected to the gate line of the power semiconductor device for detecting a Miller voltage of the power semiconductor device at the timing when the sampling signal is inputted thereto and outputting, when the Miller voltage is equal to or larger than a predetermined threshold, an over-current detection signal; and

a gate voltage controlling circuit connected to the gate line of the power semiconductor device for controlling, in response to the over-current detection signal from the gate voltage detecting circuit, the gate voltage of the power semiconductor device in such a way that the power semiconductor device is turned OFF at slower speed than in the normal case.

3. A drive circuit for driving a power semiconductor device according to claim 1, wherein one of the sampling signal generating circuit and the timing detecting circuit is composed of:

a delay circuit having a resistor and a capacitor; and

a buffer.

4. A drive circuit for driving a power semiconductor device according to claim 1, wherein one of the sampling signal generating circuit and the timing detecting circuit is composed of:

a reference voltage generating circuit for outputting a predetermined reference voltage which is previously set;

a delay circuit having a resistor and a capacitor; and

a voltage comparator for detecting whether an output voltage from the delay circuit is larger or smaller than the reference voltage.

5. A drive circuit for driving a power semiconductor device according to claim 3, wherein one of the sampling signal generating circuit and the timing detecting circuit further includes a diode which is connected in parallel with the resistor in such a way that the input control signal direction becomes the forward direction.

6. A drive circuit for driving a power semiconductor device according to claim 1, wherein an output period of time in one of the sampling signal generating circuit and the timing detecting circuit is set in such a way as to be shorter than the Miller period of time of the power semiconductor device.

7. A drive circuit for driving a power semiconductor device according to claim 1, wherein an output period of time in one of the sampling signal generating circuit and the timing detecting circuit is set so as to fall within a fixed period of time from a time point when the gate voltage begins to decrease in accordance with an OFF-command of the input control signal.

8. A drive circuit for driving a power semiconductor device according to claim 1, wherein an output period of time in one of the sampling signal generating circuit and the timing-detecting circuit depends on a power source voltage and becomes later in time as the power source voltage is further decreased.

9. A drive circuit for driving a power semiconductor device according to claim 1, wherein the gate voltage detecting circuit comprises:

a voltage amplifier connected to the gate line of the power semiconductor device for amplifying the gate voltage up to a predetermined level; and

a switch which is connected to the voltage amplifier and the state of which is switched on the basis of a signal outputted from one of the sampling signal generating circuit and the timing detecting circuit.

10. A drive circuit for driving a power semiconductor device according to claim 1, wherein the gate voltage detecting circuit comprises:

a reference voltage generating circuit for outputting a predetermined reference voltage which is previously set;

a voltage comparator connected to the gate line of the power semiconductor device for detecting whether the gate voltage of the power semiconductor device is larger or smaller than the reference voltage; and

a switch which is connected to the voltage comparator and the state of which is switched on the basis of a signal outputted from one of the sampling signal generating circuit and the timing detecting circuit.

11. A drive circuit for driving a power semiconductor device according to claim 1, wherein the gate voltage detecting circuit outputs the over-current detection signal when a current equal to or larger then a certain value flows, without changing the detection level with respect to an over-current even in the case where the Miller voltage is changed due to a change in a power source voltage of the drive circuit.

12. A drive circuit or driving a power semiconductor device according to claim 1, wherein the gate voltage detecting circuit outputs the over-current detection signal when a current equal to or larger than a certain value flows, without changing the detection level with respect to an over-current even in the case where a temperature of the drive circuit is changed.

13. A drive circuit for driving a power semiconductor device according to claim 1,

wherein the gate voltage controlling circuit comprises:

a MOS transistor which is connected to the gate voltage detecting circuit and the state of which is switched on the basis of a signal outputted front the gate voltage detecting circuit; and

a Zener diode which is connected between the gate line of the power semiconductor device and the MOS transistor.

14. A drive circuit for driving a power semiconductor device according to claim 1, wherein:

the gate voltage controlling circuit comprises;

a MOS transistor which is connected to the gate voltage detecting circuit and the state of which is switched on the basis of a signal outputted from the gate voltage detecting circuit; and

a resistor which is connected between the gate line of the power semiconductor device and the MOS transistor; and

an output from the MOS transistor is coupled to a switch on the OFF side of the switching circuit.

2. A drive circuit for driving a power semiconductor device, comprising:

a switching circuit for receiving as its input an input control signal from the outside to carry out switching of ON/OFF of the power semiconductor device;

a timing detecting circuit connected to the gate line of the power semiconductor device for detecting a Miller period of time of the power semiconductor device to output a timing signal substantially at the time instant of start of the Miller period of time of the power semiconductor device;

a gate voltage detecting circuit connected to the gate line of the power semiconductor device for detecting a Miller voltage of the power semiconductor device at the timing when the timing signal is inputted thereto and outputting, when the Miller voltage is equal to or larger than a predetermined threshold, an over-current detection signal; and

a gate voltage controlling circuit connected to the gate line of the power semiconductor device for controlling, in response to the over-current detection signal from the gate voltage detecting circuit, the gate voltage of the power semi conductor device in such a way that the power semiconductor device is turned OFF at slower speed than in the normal case.

15. A drive circuit for driving a power semiconductor device, comprising:

a switching circuit for receiving as its input an input control signal from the outside to carry out switching of ON/OFF of the power semiconductor device;

a sampling signal generating circuit for detecting the input control signal to output, when the input control signal commands OFF, a sampling signal substantially at the time instant of start of a Miller period of time of the power semiconductor device;

a gate voltage detecting circuit connected to the gate line of the power semiconductor device for detecting a Miller voltage of the power semiconductor device at the timing when the sampling signal is inputted thereto and outputting, when the Miller voltage is equal to or larger than a predetermined threshold, an over-current detection signal;

an over-current detection circuit which detects a gate voltage in the ON state and outputs an over-current detection signal in the ON state by detecting an over-current on the basis of an increase in gate voltage; and

a gate voltage controlling circuit connected to the gate line of the power semiconductor device for controlling, in response to one of the over-current detection signal from the gate voltage detecting circuit and the over-current detection signal in the ON state from the over-current detection circuit, the gate voltage of the power semiconductor device in such a way that the power semiconductor device is turned OFF at slower speed than in the normal case.