POWER CIRCUIT

• US 20100045361A1
• Filed: 08/20/2008
• Published: 02/25/2010
• Est. Priority Date: 08/20/2008
• Status: Active Grant

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Kanschat, Peter, Deboy, Gerald, Jansen, Uwe
• Granted Patent: US 8,638,129 B2
• Time in Patent Office: Days
• US Class Current: 327/383
• CPC Class Codes: H03K 17/06 Modifications for ensuring a fully conducting state

Abstract

A power circuit. One embodiment provides a circuit for driving a power transistor having a control electrode and a load path. The circuit includes a driver circuit configured to change the power transistor to a completely on or off state with the aid of a control signal supplied to the control electrode. A series circuit includes a semiconductor switching element and a capacitor. The series circuit is connected in parallel with the load path and the capacitor provides a supply voltage for the driver circuit.

Claims

1. A circuit for driving a power transistor having a control electrode and a load path, the circuit comprising:

a driver circuit configured to change the power transistor to a completely on or off state with the aid of a control signal supplied to the control electrode;

a series circuit comprising a semiconductor switching element and a capacitor, the series circuit being coupled in parallel with the load path and the capacitor providing a supply voltage for the driver circuit,

the driver circuit being configured to drive the power transistor, in the event of the supply voltage falling below a first threshold value, with the aid of the control signal in such a manner that a voltage drop across the load path of the power transistor is higher than the threshold value.

2. The circuit of claim 1, comprising wherein the driver circuit is configured to at least partially discharge the control electrode if the supply voltage falls below the first threshold value.

3. The circuit of claim 1, comprising wherein the driver circuit is configured to drive the control electrode to the off state with the aid of the control signal if the supply voltage falls below a second threshold value.

4. The circuit of claim 1, comprising wherein the driver circuit is configured to discharge the control electrode for a predefined amount of time using a gate current.

5. The circuit of claim 1, comprising wherein the driver circuit is configured to reduce the charge of the control electrode by a predefined amount of charge.

6. The circuit of claim 1, comprising wherein the driver circuit is configured to drive the semiconductor switching element to the on state if the supply voltage falls below the first threshold value and to drive the switching element to the off state again if the supply voltage exceeds a third threshold value.

7. The circuit of claim 1, comprising a pulse generator configured to trigger a partial discharge of the control electrode if the supply voltage falls below the first threshold value.

8. A method for driving a power transistor having a control electrode and a load path, a driver circuit for driving the power transistor being supplied by a capacitor which provides a supply voltage, and the method comprising:

driving the control electrode in accordance with an input signal with the aid of a control signal in such a manner that the power transistor is changed to an on state;

driving the control electrode with the aid of the control signal in such a manner that a voltage drop across the load path of the power transistor becomes higher than a threshold value in the event of the supply voltage falling below the first threshold value.

9. The method of claim 8, comprising at least partially discharging the control electrode if the supply voltage falls below the first threshold value.

10. The method of claim 8, comprising driving the control electrode to the off state with the aid of the control signal if the supply voltage falls below a second threshold value.

11. The method of claim 8, comprising discharging the control electrode for a predefined amount of time using a gate current.

12. The method of claim 8, comprising reducing the charge of the control electrode by a predefined amount of charge.

13. A power circuit comprising:

a power transistor having a control electrode and a load path;

a supply circuit comprising;

a driver circuit configured to change the power transistor to a completely on or off state with the aid of a control signal supplied to the control electrode; and

a series circuit comprising a semiconductor switching element and a capacitor, the series circuit being connected in parallel with the load path and the capacitor providing a supply voltage for the driver circuit,

the driver circuit configured to drive the power transistor, in the event of the supply voltage falling below a first threshold value, with the aid of the control signal in such a manner that a voltage drop across the load path of the power transistor is higher than the threshold value.

14. The circuit of claim 13, comprising wherein the driver circuit is configured to at least partially discharge the control electrode if the supply voltage falls below the first threshold value.

15. The circuit of claim 13, comprising wherein the driver circuit is configured to drive the control electrode to the off state with the aid of the control signal if the supply voltage falls below a second threshold value.

16. The circuit of claim 13, comprising wherein the driver circuit is configured to discharge the control electrode for a predefined amount of time using a gate current.

17. The circuit of claim 13, comprising wherein the driver circuit is configured to reduce the charge of the control electrode by a predefined amount of charge.

18. The circuit of claim 15, comprising wherein the driver circuit is configured to drive the semiconductor switching element to the on state if the supply voltage falls below the first threshold value and to drive the switching element to the off state again if the supply voltage exceeds a third threshold value.

19. The circuit of claim 13, comprising a pulse generator which is configured to trigger a partial discharge of the control electrode if the supply voltage falls below the first threshold value.

20. A method comprising:

providing a power transistor having a control electrode and a load path, and a driver circuit for driving the power transistor being supplied by a capacitor which provides a supply voltage;

driving the control electrode in accordance with an input signal with the aid of a control signal in such a manner that the power transistor is changed to an on state; and

driving the control electrode with the aid of the control signal in such a manner that a voltage drop across the load path of the power transistor becomes higher than a threshold value in the event of the supply voltage falling below the first threshold value.

21. The method of claim 20, comprising at least partially discharging the control electrode if the supply voltage falls below the first threshold value.

22. The method of claim 21, comprising driving the control electrode to the off state with the aid of the control signal if the supply voltage falls below a second threshold value.

23. The method of claim 22, comprising discharging the control electrode for a predefined amount of time using a gate current.

24. The method of claim 23, comprising reducing the charge of the control electrode by a predefined amount of charge.