Switching mode power converter using coded signal control

• US 9,093,911 B2
• Filed: 04/17/2013
• Issued: 07/28/2015
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Flextronics America LLC (Flextronics International Limited)
• Original Assignee: Flextronics America LLC (Flextronics International Limited)
• Inventors: Telefus, Mark
• Primary Examiner(s): Dole, Timothy J
• Assistant Examiner(s): AHMED, YUSEF A
• Application Number:
  US13/865,064
• Publication Number:
  US 20140268901A1
• Time in Patent Office: 832 Days
• Field of Search: 363 16- 19, 363 2101- 2118, 363/34, 363/44, 363/84, 363/89, 363 97- 98, 363125-127
• US Class Current: 1/1
• CPC Class Codes: H02M 3/33576 having at least one active switching element at the secondary side of an isolation transformer

Abstract

A switched mode power converter includes a feedback mechanism by which a coded train of pulses with well defined integrity is generated on a secondary side of the power converter and transmitted to the primary side for decoding and application by a waveform analyzer to regulate the power converter output. The pulse train is modulated by a secondary side controller and transmitted across an isolation galvanic barrier. The main transformer is used as the signal transmitter from the secondary side to the primary side of the power converter. The coded pulse train is recognized by a controller on the primary side and translated into a regulating driving signal for a main switching element. The transmitted coded pulse train can be embedded with very high frequency modulation that allows the isolation galvanic barrier to act as a capacitive signal transmitter.

Claims

1. A method of controlling a switching mode power converter comprising:

a. configuring a switching mode power converter comprising a transformer, an output circuit coupled to a secondary winding of the transformer, a first switch coupled to a primary winding of the transformer and a first controller coupled to the first switch, wherein the output circuit comprises a second switch coupled to the secondary winding of the transformer and a second controller coupled to the second switch;

b. measuring an output characteristic of the output circuit;

c. driving the second switch by the second controller to generate a coded signal, wherein the coded signal comprises coded control information based on the output characteristic, the coded signal further comprises a pulse train signal having a modulated plurality of voltage pulses;

d. transmitting the coded signal from the output circuit to the first controller;

e. decoding the coded signal by the first controller to identify the control information;

f. generating a driving signal according to the control information; and

g. driving the first switch using the driving signal to regulate the output characteristic.

2. The method of claim 1 wherein the modulated plurality of voltages pulses is modulated by modulating one or more of a pulse amplitude, a pulse frequency, a pulse width, a pulse delay, and a number of pulse cycles.

3. The method of claim 1 wherein the coded signal is transmitted during an OFF period of the first switch.

4. The method of claim 1 wherein the output characteristic is one or more of an output voltage, an output current, and an output power of the power converter.

5. The method of claim 1 wherein the control information comprises the output characteristic.

6. The method of claim 1 wherein the control information comprises a control instruction.

7. The method of claim 1 wherein generating the coded signal comprises generating and applying a driving signal to the second switch to turn the second switch on and off according to a determined pattern resulting in a modulated plurality of voltage pulses across the second winding of the transformer.

8. The method of claim 7 wherein turning the second switch on enables a negative secondary current through the secondary winding.

9. The method of claim 8 wherein enabling the negative secondary current comprises enabling an alternative current path from an output capacitor in the output circuit to the secondary winding.

10. The method of claim 1 wherein the secondary winding is magnetically coupled to an auxiliary winding, and the auxiliary winding is coupled to the first controller, further wherein transmitting the coded signal comprises using the magnetic coupling between the secondary winding and the auxiliary winding to transmit the coded signal from the output circuit to the first controller.

11. The method of claim 1 wherein transmitting the coded signal comprises using a parasitic capacitance between a primary side and a secondary side of the power converter.

12. The method of claim 11 wherein the parasitic capacitance comprises a parasitic capacitance of the transformer.

13. The method of claim 11 wherein the parasitic capacitance comprises an inherent capacitance of a printed circuit board onto which the power converter is assembled, wherein the inherent capacitance is a result of a component layout on either side of an isolation galvanic barrier.

14. The method of claim 1 wherein the first switch comprises a first transistor and the second switch comprises a second transistor.

15. The method of claim 1 wherein the coded signal is applied across the secondary winding of the transformer.

16. A switching mode power converter comprising:

a. a transformer having a primary winding coupled to an input supply voltage and a secondary winding;

b. a first switch coupled in series to the primary winding;

c. a first controller coupled to the first switch, wherein the first controller is configured to turn the first switch ON and OFF;

d. a second switch coupled in series to the secondary winding;

e. a second controller coupled to the second switch, wherein the second controller is configured to turn the second switch ON and OFF;

f. a sensing circuit coupled to the secondary winding and the second controller, wherein the sensing circuit is configured to sense an output characteristic of the power converter,

wherein the second controller is configured to generate a first driving signal to drive the second switch, wherein the first driving signal is configured to selectively turn ON and OFF the second switch to generate a coded signal that comprises coded control information based on the output characteristic, the coded signal further comprises a pulse train signal having a modulated plurality of voltage pulses, further wherein the transformer is configured as a signal transmitter to transmit the coded signal from a secondary side of the transformer to a primary side of the transformer, wherein the first controller is configured to decode the coded signal to identify the control information, generate a second driving signal according to the control information, and drive the first switch using the second driving signal to regulate the output characteristic.

17. The power converter of claim 16 wherein the modulated plurality of voltages pulses is modulated by modulating one or more of a pulse amplitude, a pulse frequency, a pulse width, a pulse delay, and a number of pulse cycles.

18. The power converter of claim 16 wherein the coded signal is transmitted during an OFF period of the first switch.

19. The power converter of claim 16 wherein the output characteristic is one or more of an output voltage, an output current, and an output power of the power converter.

20. The power converter of claim 16 wherein the control information comprises the output characteristic.

21. The power converter of claim 16 wherein the control information comprises a control instruction.

22. The power converter of claim 16 further comprising an auxiliary winding coupled to the first controller, wherein the auxiliary winding is magnetically coupled to the secondary winding.

23. The power converter of claim 22 wherein the transformer is configured to transmit the coded signal from the secondary winding to the auxiliary winding using the magnetic coupling between the secondary winding and the auxiliary winding.

24. The power converter of claim 22 wherein the transformer is configured to transmit the coded signal from the secondary winding to the auxiliary winding using a parasitic capacitance between a primary side and a secondary side of the power converter.

25. The power converter of claim 24 wherein the parasitic capacitance comprises a parasitic capacitance of the transformer.

26. The power converter of claim 24 wherein the parasitic capacitance comprises an inherent capacitance of a printed circuit board onto which the power converter is assembled, wherein the inherent capacitance is a result of a component layout on either side of an isolation galvanic barrier.

27. The power converter of claim 16 wherein the first switch comprises a first transistor and the second switch comprises a second transistor.

28. The power converter of claim 16 wherein the sensing circuit comprises a voltage divider circuit.

29. The power converter of claim 16 further comprising a diode coupled in series with the secondary winding and in parallel to the second switch and an output capacitor coupled in series to the diode, wherein the diode is configured to enable current flow from the secondary winding to the output capacitor when forward-biased.

30. The power converter of claim 29 wherein when the second switch is ON, an alternative current path is formed between the output capacitor and the secondary winding of the transformer, further wherein a negative secondary current flows from the output capacitor to the secondary winding via the alternative current path.

31. The power converter of claim 30 wherein the negative secondary current is generated as discharge from the output capacitor when the alternative current path is formed.

32. The power converter of claim 30 wherein the second switch, the second controller, the diode and the output capacitor comprise an output circuit, further wherein the output circuit is configured as a bi-directional current flow circuit, wherein a first current flow direction corresponds to positive secondary current from the secondary winding to the output capacitor and to an output of the output circuit to deliver power, and a second current flow direction corresponds to negative secondary current from the output capacitor to the secondary winding to provide control for switching the first switch coupled to the primary winding.

33. The power converter of claim 16 wherein the power converter is configured as one of a flyback-type power converter circuit, a forward-type power converter circuit, a push-pull-type power converter circuit, a half-bridge-type power converter circuit, and a full-bridge-type power converter circuit.

34. The power converter of claim 16 wherein the coded signal is applied across the secondary winding of the transformer.