CONTROL DATA DETERMINATION FROM PRIMARY-SIDE SENSING OF A SECONDARY-SIDE VOLTAGE IN A SWITCHING POWER CONVERTER

• US 20120306406A1
• Filed: 06/01/2012
• Published: 12/06/2012
• Est. Priority Date: 06/03/2011
• Status: Active Grant

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Grisamore, Robert T., He, Zhaohui
• Granted Patent: US 9,313,840 B2
• Time in Patent Office: Days
• US Class Current: 315/294
• CPC Class Codes: H02M 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/385 using flyback topology
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A power distribution system includes controller of a switching power converter to control the switching power converter and determine one or more switching power converter control parameters. In at least one embodiment, the controller determines the one or more switching power converter control parameters using a resonant period factor from a reflected secondary-side voltage and an occurrence of an approximate zero voltage crossing of the secondary-side voltage during a resonant period of the secondary-side voltage. In at least one embodiment, the switching power converter control parameters include (i) an estimated time of a minimum value of the secondary-side voltage during the resonant period and (ii) an estimated time at which a current in the secondary-side of the transformer decayed to approximately zero.

Claims

1. A method comprising:

receiving a sense signal from a primary-side of a transformer of a switching power converter, wherein the sense signal represents a secondary-side voltage across a secondary-side of the transformer;

determining one or more times between approximately zero crossings of the secondary-side voltage during one or more resonant periods of the secondary-side voltage, wherein each resonant period occurs after the secondary-side voltage decreases to zero and before a current in the primary-side of the transformer increases from approximately zero;

determining one or more resonant period factors from the one or more times between approximately zero crossings of the secondary-side voltage; and

determining one or more switching power converter control parameters using (i) the one or more resonant period factors and (ii) an occurrence of an approximate zero voltage crossing of the secondary-side voltage during a resonant period of the secondary-side voltage.

2. The method of claim 1 wherein the one or more switching power converter control parameters comprise an estimated time at which a current in the secondary-side of the transformer decayed to approximately zero.

3. The method of claim 2 wherein the one or more resonant period factors comprise a time that equals approximately one-fourth of the resonant period, and determining one or more switching power converter control parameters further comprises:

during a cycle of a switch controlling current in the primary-side of the transformer, subtracting the resonant period factor from a time of a first approximately zero voltage crossing of the resonant period to determine an estimated time at which a current in the secondary-side of the transformer decayed to approximately zero.

4. The method of claim 1 wherein the one or more switching power converter control parameters comprise an estimated time of a minimum value of the secondary-side voltage during the resonant period.

5. The method of claim 4 wherein the one or more resonant period factors comprise a time that equals approximately one-fourth of the resonant period, and determining one or more switching power converter control parameters further comprises:

during a cycle of a switch controlling current in the primary-side of the transformer, adding the resonant period factor to a time of a first approximately zero voltage crossing of the resonant period to determine an estimated time of a minimum value of the secondary-side voltage during the resonant period.

6. The method of claim 4 further comprising:

causing the switch controlling the current in the primary-side of the transformer to conduct one-quarter period after a detected zero voltage crossing of the secondary-side voltage.

7. The method of claim 1 wherein the one or more switching power converter control parameters comprise (i) an estimated time of a minimum value of the secondary-side voltage during the resonant period and (ii) an estimated time at which a current in the secondary-side of the transformer decayed to approximately zero.

8. The method of claim 1 wherein the signal representing the secondary-side voltage across a secondary-side of the transformer is a reflected secondary-side voltage across an auxiliary winding of the transformer coupled to the secondary-side of the transformer.

9. The method of claim 1 wherein:

determining each time between approximately zero crossings of the secondary-side voltage during one or more resonant periods of the secondary-side voltage comprises;

allowing the secondary-side voltage to resonate for at least one-half period between adjacent zero crossings; and

determining the one or more resonant period factors from the one or more times between approximately zero crossings of the secondary-side voltage comprises;

averaging times between multiple adjacent approximately zero crossings of the secondary-side voltage multiple at least one-half resonant periods to determine an average of the resonant period factors.

10. The method of claim 1 further comprising:

determining one or more times between approximately zero crossings of the secondary-side voltage during one or more resonant periods of the secondary-side voltage when an input voltage to the primary-side of the transformer is sufficient to reverse bias a body diode of a switch that controls current in the primary-side of the transformer.

11. The method of claim 1 further comprising:

detecting the approximately zero crossings of the secondary-side voltage.

12. The method of claim 1 further comprising:

generating a control signal to control power provided to a load.

13. The method of claim 12 wherein the load comprises one or more light emitting diodes.

14. An apparatus comprising:

a controller wherein the controller includes an input to receive a sense signal from a primary-side of a transformer of a switching power converter, wherein the sense signal represents a secondary-side voltage across a secondary-side of the transformer, and the controller is capable to;

determine one or more times between approximately zero crossings of the secondary-side voltage during one or more resonant periods of the secondary-side voltage, wherein each resonant period occurs after the secondary-side voltage decreases to zero and before a current in the primary-side of the transformer increases from approximately zero;

determine one or more resonant period factors from the one or more times between approximately zero crossings of the secondary-side voltage; and

determine one or more switching power converter control parameters using (i) the one or more resonant period factors and (ii) an occurrence of an approximate zero voltage crossing of the secondary-side voltage during a resonant period of the secondary-side voltage.

15. The apparatus of claim 14 wherein the one or more switching power converter control parameters comprise an estimated time at which a current in the secondary-side of the transformer decayed to approximately zero.

16. The apparatus of claim 15 wherein the one or more resonant period factors comprise a time that equals approximately one-fourth of the resonant period, and to determine the one or more switching power converter control parameters, the controller is further capable to:

during a cycle of a switch controlling current in the primary-side of the transformer, subtract the resonant period factor from a time of a first approximately zero voltage crossing of the resonant period to determine an estimated time at which a current in the secondary-side of the transformer decayed to approximately zero.

17. The apparatus of claim 14 wherein the one or more switching power converter control parameters comprise an estimated time of a minimum value of the secondary-side voltage during the resonant period.

18. The apparatus of claim 14 wherein the one or more resonant period factors comprise a time that equals approximately one-fourth of the resonant period, and to determine the one or more switching power converter control parameters, the controller is further capable to:

during a cycle of a switch controlling current in the primary-side of the transformer, add the resonant period factor to a time of a first approximately zero voltage crossing of the resonant period to determine an estimated time of a minimum value of the secondary-side voltage during the resonant period.

19. The apparatus of claim 18, the controller is further capable to:

cause the switch controlling the current in the primary-side of the transformer to conduct one-quarter period after a detected zero voltage crossing of the secondary-side voltage.

20. The apparatus of claim 14 wherein the one or more switching power converter control parameters comprise (i) an estimated time of a minimum value of the secondary-side voltage during the resonant period and (ii) an estimated time at which a current in the secondary-side of the transformer decayed to approximately zero.

21. The apparatus of claim 14 wherein the signal representing the secondary-side voltage across a secondary-side of the transformer is a reflected secondary-side voltage across an auxiliary winding of the transformer coupled to the secondary-side of the transformer.

22. The apparatus of claim 14 wherein:

to determine each time between approximately zero crossings of the secondary-side voltage during one or more resonant periods of the secondary-side voltage, controller is further capable to;

allow the secondary-side voltage to resonate for at least one-half period between adjacent zero crossings; and

to determine the one or more resonant period factors from the one or more times between approximately zero crossings of the secondary-side voltage, the controller is further capable to;

average times between multiple adjacent approximately zero crossings of the secondary-side voltage multiple at least one-half resonant periods to determine an average of the resonant period factors.

23. The apparatus of claim 14 wherein the controller is further capable to:

determine one or more times between approximately zero crossings of the secondary-side voltage during one or more resonant periods of the secondary-side voltage when an input voltage to the primary-side of the transformer is sufficient to reverse bias a body diode of a switch that controls current in the primary-side of the transformer.

24. The apparatus of claim 14 wherein the controller is further capable to:

detect the approximately zero crossings of the secondary-side voltage.

25. The apparatus of claim 14 wherein the controller is further capable to:

generate a control signal to control power provided to a load.

26. The apparatus of claim 25 wherein the load comprises one or more light emitting diodes.

27. An apparatus comprising:

a switching power converter, wherein the switching power converter includes a transformer having a primary-side and a secondary-side;

a controller wherein the controller includes an input to receive a sense signal from the primary-side of the transformer of the switching power converter, wherein the sense signal represents a secondary-side voltage across the secondary-side of the transformer, and the controller is capable to;

determine one or more times between approximately zero crossings of the secondary-side voltage during one or more resonant periods of the secondary-side voltage, wherein each resonant period occurs after the secondary-side voltage decreases to zero and before a current in the primary-side of the transformer increases from approximately zero;

determine one or more resonant period factors from the one or more times between approximately zero crossings of the secondary-side voltage; and

determine one or more switching power converter control parameters using (i) the one or more resonant period factors and (ii) an occurrence of an approximate zero voltage crossing of the secondary-side voltage during a resonant period of the secondary-side voltage; and

a load coupled to the secondary-side of the transformer of the switching power converter.

28. The apparatus of claim 27 wherein the load comprises one or more light emitting diodes.