Modulated transformer-coupled gate control signaling method and apparatus

• US 7,656,687 B2
• Filed: 12/11/2007
• Issued: 02/02/2010
• Est. Priority Date: 12/11/2007
• Status: Active Grant

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Melanson, John L.
• Primary Examiner(s): Vu; Bao Q
• Application Number:
  US11/954,202
• Publication Number:
  US 20090147544A1
• Time in Patent Office: 784 Days
• Field of Search: 363/34, 363/20, 363/21.01, 363/15, 363/16, 363/95, 363/97
• US Class Current: 363/34
• CPC Class Codes: H02M 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
• CPC Class Codes: H03K 17/691 using transformer coupling

Abstract

A modulated transformer-coupled gate control signaling method and apparatus provides reduction of circuit complexity and robust design characteristics in switching power circuits having a transformer-coupled gate drive. A modulated control signal at a rate substantially higher than the switching circuit gate control rate is provided from the controller circuit to a demodulator via transformer coupling. Power for the demodulator can be obtained by rectifying the modulated control signal at the demodulator, or from another transformer winding. The modulation scheme is chosen to have a DC average value of zero, eliminating any magnetization current management requirements. The modulated control signal may carry redundant control information and/or may encode additional information to provide a more sophisticated gate drive control, such as oversampled gate control information.

Claims

1. A circuit, comprising:

a switching power stage for producing a switched power output at a switching rate and having at least one power switching transistor;

a switching control circuit for determining a turn-on time and a turn-off time of the at least one power switching transistor at the switching rate, and having an output generated at a modulated rate that is greater than the switching rate;

a transformer for coupling the output of the switching control circuit to the at least one power switching transistor, whereby the at least one transistor has a gate that is DC isolated from the switching control circuit, wherein a first winding of the transformer is connected to the switching control circuit; and

a demodulator circuit connected to at least one second winding of the transformer and having an output coupled to the gate of the at least one power switching transistor, wherein the output of the demodulator is at least one gate control signal generated at the switching rate from a control signal received from the at least one second winding at the modulated rate, and wherein a single period of the at least one gate control signal is generated in conformity with redundant or differing information contained in multiple periods of the output of the switching control circuit.

2. The circuit of claim 1, further comprising a rectifier circuit connected to the at least one second winding of the transformer for generating a DC voltage from the control signal present on the at least one second winding at the modulated rate, wherein an output of the rectifier circuit provides power to the demodulator circuit.

3. The circuit of claim 1, wherein the turn-on time and turn-off time of the at least one power switching transistor are determined by the demodulator circuit from differing information provided in multiple periods of the control signal.

4. The circuit of claim 1, wherein redundant information specifying the turn-on time and turn-off time of the at least one power switching transistor is provided by the output of the switching control circuit in multiple periods of the control signal.

5. The circuit of claim 1, wherein the demodulator circuit comprises a reference clock generator for generating a reference clock having a rate substantially higher than the switching rate.

6. The circuit of claim 5, wherein the demodulator circuit further comprises logic for storing information provided in multiple periods of the control signal and for determining the turn-off time and turn-on time of the at least one power switching transistor from the stored information.

27. The circuit of claim 1, wherein the at least one power switching transistor comprises multiple power switching transistors, wherein the at least one gate control signal comprises multiple corresponding gate control signals, and wherein the control signal encodes differing information in multiple periods of the control signal for generating the multiple corresponding gate control signals.

7. A method for controlling a switching power stage, comprising:

generating a modulated control signal for controlling a turn-on time and a turn-off time of a transistor of the switching power stage at a switching rate of the switching power stage, wherein the modulated control signal is generated at a modulated rate greater than the switching rate of the switching power stage;

transformer isolating the modulated control signal to provide a DC isolated control signal to at least one power switching transistor of the switching power stage; and

demodulating the DC isolated control signal from the modulated rate to generate at least one gate control signal that controls the at least one power switching transistor at the switching rate, and wherein a single period of the at least one gate control signal is generated in conformity with redundant or differing information contained in multiple periods of the modulated control signal.

8. The method of claim 7, further comprising generating a DC power supply from a winding of the transformer to operate a demodulator for performing the demodulating.

9. The method of claim 7, wherein the at least one power switching transistor is a first switching device of the switching power stage and further comprising providing another control signal directly from an integrated circuit that provides the control signal to control a second switching device of the switching power stage that is not transformer isolated.

10. The method of claim 7, wherein the demodulating determines the turn-on time and turn-off time of the at least one power switching transistor from differing information provided in multiple periods of the modulated control signal.

11. The method of claim 10, wherein the demodulating comprises generating a reference signal from the modulated control signal at a rate substantially higher than the switching rate.

12. The method of claim 11, further comprising:

detecting information in multiple periods of the modulated control signal using the reference signal; and

controlling the turn-on time and the turn-off time of the transistor of the switching power stage in conformity with the detected information.

28. The method of claim 7, wherein the at least one power switching transistor comprises multiple power switching transistors, and wherein the demodulating generates the multiple corresponding gate control signals from differing information encoded in the control signal.

13. An integrated circuit, comprising:

a pair of terminals for connection to an output winding of a transformer having a control signal imposed from an input winding carrying information for controlling a switching power stage, wherein the switching power stage produces a switched power output at a switching rate and includes at least one power switching transistor, and wherein the control signal carries said information at a modulated rate that is greater than the switching rate; and

a demodulator circuit having inputs coupled to the pair of terminals and having an output coupled to a driver circuit for controlling the gate of the at least one power switching transistor, wherein the output of the demodulator is at least one gate control signal generated at the switching rate from a signal received by the pair of terminals from the output winding that contains the information at the modulated rate, and wherein a single period of the at least one gate control signal is generated in conformity with redundant or differing information contained in multiple periods of the control signal.

14. The integrated circuit of claim 13, further comprising a rectifier circuit connected to the pair of terminals for generating a DC voltage from the control signal, wherein an output of the rectifier circuit provides power to the demodulator circuit.

15. The integrated circuit of claim 13, wherein a turn-on time and turn-off time of the at least one power switching transistor are determined by the demodulator circuit from differing information provided in multiple periods of the control signal.

16. The integrated circuit of claim 13, wherein redundant information specifying a turn-on time and turn-off time of the at least one power switching transistor are detected by the demodulator circuit in multiple periods of the output of the control signal.

17. The integrated circuit of claim 13, wherein the demodulator circuit comprises a reference clock generator for generating a reference clock having a rate substantially higher than the switching rate.

18. The integrated circuit of claim 13, further comprising:

at least one additional pair of terminals for connection to an output winding of at least one other transformer for imposing at least one other control signal for controlling at least one other corresponding switching power stage, wherein the at least one other control signal also carries information at a modulated rate that is greater than the switching rate; and

at least one additional demodulator having inputs coupled to the at least one additional pair of terminals and having an output coupled to at least one other driver circuit for controlling the gate of the at least one other power switching transistor, wherein the output of the at least one other demodulator is another gate control signal generated at the switching rate from a signal received by the at least one other pair of terminals.

19. The integrated circuit of claim 18, wherein the at least one additional pair of terminals comprises two pairs of terminals, wherein the at least one transformer comprises two transformers, and wherein the at least one other corresponding switching power stage comprises two switching power stages, whereby three-phase power switching control is provided.

29. The integrated circuit of claim 13, wherein the at least one power switching transistor comprises multiple power switching transistors, and wherein the at least one gate control signal comprises multiple corresponding gate control signals, and wherein the control signal encodes differing information in multiple periods of the control signal for generating the multiple corresponding gate control signals.

20. An integrated circuit, comprising:

a pair of terminals for connection to an input winding of a transformer for imposing a control signal carrying information for controlling a switching power stage coupled to an output winding of the transformer, wherein the switching power stage produces a switched power output at a switching rate and includes at least one power switching transistor, and wherein the control signal carries said information at a modulated rate that is greater than the switching rate; and

a switching control circuit having an output coupled to at least one of the pair of terminals for determining a turn-on time and a turn-off time of the at least one power switching transistor and generating the control signal at a modulated rate that is greater than the switching rate, and wherein the control signal encodes redundant or differing information in multiple periods of the control signal for generating at least one gate control signal that controls the at least one power switching transistor.

21. The integrated circuit of claim 20, wherein the turn-on time and turn-off time of the at least one power switching transistor are encoded in the control signal by differing information provided in multiple periods of the output of the switching control circuit.

22. The integrated circuit of claim 20, wherein redundant information specifying the turn-on time and turn-off time of the at least one power switching transistor is provided by the output of the switching control circuit in multiple periods of the output of the switching control circuit.

23. The integrated circuit of claim 20, further comprising at least one additional terminal for supplying a control signal coupled via a direct current path to a gate of a transistor of the switching power stage.

24. The integrated circuit of claim 20, further comprising at least one additional pair of terminals for connection to an input winding of at least one other transformer for imposing at least one other control signal for controlling at least one other corresponding switching power stage coupled to an output winding of the at least one other transformer, and wherein the at least one other control signal also carries information at a modulated rate that is greater than the switching rate.

25. The integrated circuit of claim 24, wherein the at least one additional pair of terminals comprises two pairs of terminals, wherein the at least one transformer comprises two transformers, and wherein the at least one other corresponding switching power stage comprises two switching power stages, whereby three-phase power switching control is provided.

26. The integrated circuit of claim 20, wherein the at least one power switching transistor comprises multiple power switching transistors, wherein the at least one gate control signal comprises multiple corresponding gate control signals, and wherein the control signal encodes differing information in multiple periods of the control signal for generating the multiple corresponding gate control signals.

30. A circuit, comprising:

a switching power stage for producing a switched power output at a switching rate and having at least one power switching transistor;

a switching control circuit for determining a turn-on time and a turn-off time of the at least one power switching transistor at the switching rate, and having an output generated at a modulated rate that is greater than the switching rate;

a transformer for coupling the output of the switching control circuit to the at least one power switching transistor, whereby the at least one transistor has a gate that is DC isolated from the switching control circuit, wherein a first winding of the transformer is connected to the switching control circuit; and

a demodulator circuit connected to at least one second winding of the transformer and having an output coupled to the gate of the at least one power switching transistor, wherein the output of the demodulator is at least one gate control signal generated at the switching rate from a control signal received from the at least one second winding at the modulated rate, and wherein the control signal encodes further information provided at a second output of the demodulator.

31. A method for controlling a switching power stage, comprising:

generating a modulated control signal for controlling a turn-on time and a turn-off time of a transistor of the switching power stage at a switching rate of the switching power stage, wherein the modulated control signal is generated at a modulated rate greater than the switching rate of the switching power stage;

transformer isolating the modulated control signal to provide a DC isolated control signal to at least one power switching transistor of the switching power stage; and

demodulating the DC isolated control signal from the modulated rate to generate at least one gate control signal that controls the at least one power switching transistor at the switching rate from first information encoded in the modulated control signal and generating at least one other signal from second information encoded in the modulated control signal.