Drive circuit for power element

1. A drive circuit for turning on/off a power element which is configured to control a main current flow between a first main electrode and a second main electrode in response to a drive signal applied to a control electrode, the drive circuit comprising:

a first series circuit which includes a first semiconductor switching element and a second semiconductor switching element connected in series with a semiconductor element or a constant voltage element therebetween, which is provided between a power supply terminal and a ground terminal, wherein the semiconductor element or the constant voltage element has a positive temperature characteristic, and wherein a series connection point of the second semiconductor switching element provided on the ground terminal side and the semiconductor element or the constant voltage element having the positive temperature characteristic is connected to the control electrode of the power element;

a second series circuit which includes a third semiconductor switching element and a fourth semiconductor switching element connected in series, which is provided between the power supply terminal and the ground terminal, wherein a series connection point of the third semiconductor switching element and the fourth semiconductor switching element is connected to the second main electrode of the power element; and

a control circuit which is configured to control turn-on/off of the power element by turning on/off the first to fourth semiconductor switching elements in association with one another in response to a control signal.

2. The drive circuit according to claim 1 ,

wherein the semiconductor element having the positive temperature characteristic includes a Zener diode of which a reverse breakdown voltage increases with temperature increase, and

wherein the first series circuit is configured to change a voltage applied to the control electrode of the power element in accordance with a change in an operation voltage threshold value of the power element when the first semiconductor switching element is turned on.

3. The drive circuit according to claim 1 ,

wherein the constant voltage element includes a temperature-compensated constant-voltage diode circuit which is configured to generate a constant reverse breakdown voltage regardless of temperature change, and

wherein the first series circuit is configured to apply, when the first semiconductor switching element is turned on, a voltage necessary for turning the power element on regardless of a change in an operation voltage threshold value of the power element.

4. The drive circuit according to claim 1 ,

wherein in a normal operation for turning the power element on/off, the control circuit is configured to:

turn the power element on by turning on each of the first and fourth semiconductor switching elements and turning off each of the second and third semiconductor switching elements, and

turn the power element off by turning off each of the first and fourth semiconductor switching elements and turning on each of the second and third semiconductor switching elements.

5. The drive circuit according to claim 1 ,

wherein at a time of forcibly turning the power element off, the control circuit is configured to turn on each of the first and third semiconductor switching elements and turn off each of the second and fourth semiconductor switching elements.

6. The drive circuit according to claim 1 ,

wherein at a time of forcibly turtling the power element off, the control circuit is configured to turn on each of the second and fourth semiconductor switching elements and turn off each of the first and third semiconductor switching elements.

7. The drive circuit according to claim 1 ,

wherein the power element includes an IGBT which includes the control electrode as a gate, the first main electrode as a collector, and the second main electrode as an emitter, and

wherein each of the first to fourth semiconductor switching elements includes a MOS-FET which is configured to be turned on/off in response to a voltage applied to a gate thereof from the control circuit.

8. The drive circuit according to claim 1 ,

wherein the power element includes an N-type power MOS-FET which includes the control electrode as a gate, the first main electrode as a drain, and the second main electrode as a source, and

wherein each of the first to fourth semiconductor switching elements includes a MOS-FET which is configured to be turned on/off in response to a voltage applied to a gate thereof from the control circuit.