Utilizing secondary-side conduction time parameters of a switching power converter to provide energy to a load

• US 9,024,541 B2
• Filed: 03/07/2014
• Issued: 05/05/2015
• Est. Priority Date: 03/07/2013
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Xie, Yanhui, Kost, Michael A., Melanson, John L., He, Zhaohui, Franklin, Chris M.
• Primary Examiner(s): Le, Tung X
• Application Number:
  US14/201,050
• Publication Number:
  US 20140252981A1
• Time in Patent Office: 424 Days
• Field of Search: 315/209.R, 315/224, 315/225, 315/274, 315/276, 315/287, 315/291, 315/297, 315/307, 315/360, 363/21.12
• US Class Current: 315/307
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/38 using boost topology
• 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]

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 switching power converter utilizes a transformer to transfer energy from a primary-side of the transformer to a secondary-side of the transformer. In at least one embodiment, the switching power converter control parameters includes a secondary-side conduction time delay that represents a time delay between when the primary-side ceases conducting a primary-side current and the secondary-side begins to conduct a secondary-side current. In at least one embodiment, determining and accounting for this secondary-side conduction time delay increases the prediction accuracy of the secondary-side current value and accurate delivery of energy to a load when the controller does not directly sense the secondary-side current provided to the load.

Claims

1. A method comprising:

receiving one or more signals from a switching power converter;

processing the one or more signals to determine an approximate secondary-side conduction time delay that begins when at least one of the signals indicates cessation of primary-side current conduction in a transformer of the switching power converter and ends when conduction begins in a secondary-side current in the transformer;

determining the secondary-side current conduction time utilizing the secondary-side conduction time delay;

determining an approximate amount of charge transferred to the secondary-side of the transformer using the determined secondary-side current conduction time; and

generating a current control signal to control power delivered to a load coupled to the switching power converter based on the determined approximate amount of charge transferred to the secondary-side of the transformer.

2. The method of claim 1 wherein determining the approximate secondary-side conduction time delay further comprises:

sensing a signal representing a secondary-side voltage of a transformer of the switching power converter; and

based on at least one value of the sensed signal, determining the approximate secondary-side conduction time delay.

3. The method of claim 2 wherein the transformer further includes an auxiliary secondary-side winding, and the signal representing the secondary-side voltage of a transformer of the switching power converter comprises an auxiliary voltage across the auxiliary secondary-side winding.

4. The method of claim 3 wherein the value of the sensed signal represents a zero crossing of the auxiliary voltage and determining the approximate secondary-side conduction time delay comprises:

determining an elapsed time between cessation of the primary-side current conduction until sensing the zero crossing of the auxiliary voltage; and

determining the approximate secondary-side conduction time delay using the determined elapsed time.

5. The method of claim 4 wherein determining the approximate secondary-side conduction time delay using the determined elapsed time comprises:

multiplying the elapsed time by a value greater than one to determine the approximate secondary-side conduction time delay.

6. The method of claim 3 wherein the value of the sensed signal represents a zero crossing of the auxiliary voltage and determining the approximate secondary-side conduction time delay comprises:

determining a first elapsed time from when a pulse of a current control signal for the switching power converter ends that coincides with cessation of the primary-side current conduction and when a zero crossing detection signal received by the controller indicates a zero crossing of the auxiliary voltage;

determining a second elapsed time between the end of the first elapsed time cessation of the primary-side current conduction until determining that a first mathematical derivative of the auxiliary voltage is zero; and

adding the first and second elapsed times to determine the approximate secondary-side conduction time delay.

7. The method of claim 1 wherein determining the approximate secondary-side conduction time delay further comprises:

sensing a signal representing a drain voltage of a current control switch coupled to the primary-side of the transformer to control current in the primary-side;

processing the sensed signal representing the drain voltage to determine an elapsed time between cessation of the primary-side current conduction and when a first mathematical derivative of the signal equals zero; and

determining the approximate secondary-side conduction time delay using the determined elapsed time.

8. The method of claim 1 further comprising:

generating a control signal to turn the switch “

OFF”

;

determining a resonant period T_RES of a secondary-side voltage;

detecting zero crossings of the secondary-side voltage;

determining an estimated secondary-side current conduction time period T_2EST, wherein T_2EST equals an elapsed time from when the switch turns “

OFF” and

detection of a second zero crossing of the secondary-side voltage; and

determining the approximate secondary-side transformer current conduction time to equal T_2EST−

T_RES/4−

the secondary-side conduction time delay.

9. The method of claim 1 wherein the control switch is a field effect transistor (FET) coupled between a primary-side winding of the transformer and a reference voltage and determining the approximate secondary-side conduction time delay comprises:

sensing a drain voltage of the FET;

determining a first derivative of the drain voltage; and

determining the approximate secondary-side conduction time delay from when the FET is turned “

OFF”

until the first derivative of the drain voltage equals zero.

10. The method of claim 1 wherein the control switch is a field effect transistor (FET) coupled between a primary-side winding of the transformer and a reference voltage and determining the approximate secondary-side conduction time delay comprises:

generating a control signal to turn the FET “

OFF”

at a time t₀;

detecting a zero crossing of a signal representing a voltage on a secondary-side of the transformer, wherein the detected zero crossing occurs at a time t₁;

determining an elapsed time period T_d1 wherein T_d1=t₁−

t₀;

determining an elapsed time period T_d2 from t₁ until a drain voltage of the FET reaches a maximum value during the cycle of the FET; and

determining the approximate secondary-side conduction time delay equal to T_d1+T_d2.

11. The method of claim 10 further comprising:

generate a control signal to turn the switch “

OFF”

;

determining a resonant period T_RES of a secondary-side voltage;

detecting zero crossings of the secondary-side voltage;

determining an estimated secondary-side current conduction time period T_2EST, wherein T_2EST equals an elapsed time from when the switch turns “

OFF” and

detection of a second zero crossing of the secondary-side voltage; and

determining the approximate secondary-side transformer current conduction time to equal T_2EST−

T_RES/4−

T_d1−

T_d2.

12. The method of claim 1 wherein the load comprises one or more light emitting diodes.

13. The method of claim 1 wherein cessation of the primary-side current conduction in the transformer until conduction begins in a secondary-side current in the transformer occurs during a single cycle of a control switch that controls current in the flyback-type switching power converter.

14. The method of claim 1 wherein the switching power converter is a flyback-type switching power converter.

15. The method of claim 1 wherein:

the switching power converter includes a field effect transistor (FET) to control primary-side current conduction;

receiving one or more signals from the switching power converter comprises receiving a signal representing a gate voltage of the FET; and

processing the one or more signals to determine an approximate secondary-side conduction time delay comprises processing the signal representing the gate voltage of the FET to determine the approximate secondary-side conduction time delay.

16. An apparatus comprising:

a controller configured to;

receive one or more signals from a switching power converter;

process the one or more signals to determine an approximate secondary-side conduction time delay that begins when at least one of the signals indicates cessation of primary-side current conduction in a transformer of the switching power converter and ends when conduction begins in a secondary-side current in the transformer;

determine the secondary-side current conduction time utilizing the secondary-side conduction time delay;

determine an approximate amount of charge transferred to the secondary-side of the transformer using the determined secondary-side current conduction time; and

generate a current control signal to control power delivered to a load coupled to the switching power converter based on the determined approximate amount of charge transferred to the secondary-side of the transformer.

17. The apparatus of claim 16 wherein to determine the approximate secondary-side conduction time delay, the controller is further configured to:

sense a signal representing a secondary-side voltage of a transformer of the switching power converter; and

based on at least one value of the sensed signal, determine the approximate secondary-side conduction time delay.

18. The apparatus of claim 17 wherein the transformer further includes an auxiliary secondary-side winding, and the signal representing the secondary-side voltage of a transformer of the switching power converter comprises an auxiliary voltage across the auxiliary secondary-side winding.

19. The apparatus of claim 18 wherein the value of the sensed signal represents a zero crossing of the auxiliary voltage and to determine the approximate secondary-side conduction time delay the controller is further configured to:

determine an elapsed time between cessation of the primary-side current conduction until sensing the zero crossing of the auxiliary voltage; and

determine the approximate secondary-side conduction time delay using the determined elapsed time.

20. The apparatus of claim 19 wherein to determine the approximate secondary-side conduction time delay using the determined elapsed time the controller is further configured to:

multiply the elapsed time by a value greater than one to determine the approximate secondary-side conduction time delay.

21. The apparatus of claim 18 wherein the value of the sensed signal represents a zero crossing of the auxiliary voltage and to determine the approximate secondary-side conduction time delay, the controller is further configured to:

determine a first elapsed time from when a pulse of a current control signal for the switching power converter ends that coincides with cessation of the primary-side current conduction and when a zero crossing detection signal received by the controller indicates a zero crossing of the auxiliary voltage;

determine a second elapsed time between the end of the first elapsed time cessation of the primary-side current conduction until determining that a first mathematical derivative of the auxiliary voltage is zero; and

add the first and second elapsed times to determine the approximate secondary-side conduction time delay.

22. The apparatus of claim 16 wherein to determine the approximate secondary-side conduction time delay, the controller is further configured to:

sense a signal representing a drain voltage of a current control switch coupled to the primary-side of the transformer to control current in the primary-side;

process the sensed signal representing the drain voltage to determine an elapsed time between cessation of the primary-side current conduction and when a first mathematical derivative of the signal equals zero; and

determine the approximate secondary-side conduction time delay using the determined elapsed time.

23. The apparatus of claim 16 the controller is further configured to:

generate a control signal to turn the switch “

OFF”

;

determine a resonant period T_RES of a secondary-side voltage;

detect zero crossings of the secondary-side voltage;

determine an estimated secondary-side current conduction time period T_2EST, wherein T_2EST equals an elapsed time from when the switch turns “

OFF” and

detection of a second zero crossing of the secondary-side voltage; and

determine the approximate secondary-side transformer current conduction time to equal T_2EST−

T_RES/4−

the secondary-side conduction time delay.

24. The apparatus of claim 16 wherein the control switch is a field effect transistor (FET) coupled between a primary-side winding of the transformer and a reference voltage and to determine the approximate secondary-side conduction time delay, the controller is further configured to:

sense a drain voltage of the FET;

determine a first derivative of the drain voltage; and

determine the approximate secondary-side conduction time delay from when the FET is turned “

OFF”

until the first derivative of the drain voltage equals zero.

25. The apparatus of claim 16 wherein the control switch is a field effect transistor (FET) coupled between a primary-side winding of the transformer and a reference voltage and to determine the approximate secondary-side conduction time delay the controller is further configured to:

generate a control signal to turn the FET “

OFF”

at a time t₀;

detect a zero crossing of a signal representing a voltage on a secondary-side of the transformer, wherein the detected zero crossing occurs at a time t₁;

determine an elapsed time period T_d1, wherein T_d1=t₁−

t₀;

determine an elapsed time period T_d2 from t₁ until a drain voltage of the FET reaches a maximum value during the cycle of the FET; and

determine the approximate secondary-side conduction time delay equal to T_d1+T_d2.

26. The apparatus of claim 25 the controller is further configured to:

generate a control signal to turn the switch “

OFF”

;

determine a resonant period T_RES of a secondary-side voltage;

detect zero crossings of the secondary-side voltage;

determine an estimated secondary-side current conduction time period T_2EST, wherein T_2EST equals an elapsed time from when the switch turns “

OFF” and

detection of a second zero crossing of the secondary-side voltage; and

determine the approximate secondary-side transformer current conduction time to equal T_2EST−

T_RES/4−

T_d1−

T_d2.

27. The apparatus of claim 16 wherein the load comprises one or more light emitting diodes.

28. The apparatus of claim 16 wherein cessation of the primary-side current conduction in the transformer until conduction begins in a secondary-side current in the transformer occurs during a single cycle of a control switch that controls current in the flyback-type switching power converter.

29. The apparatus of claim 16 wherein the controller comprises an integrated circuit.

30. The apparatus of claim 16 wherein the switching power converter is a flyback-type switching power converter.

31. The apparatus of claim 16 wherein the switching power converter include a field effect transistor (FET) to control primary-side current conduction and the one or more signals from the switching power converter comprises a signal representing a gate voltage of the FET, and the controller is further configured to:

process the one or more signals to determine an approximate secondary-side conduction time delay comprises processing the signal representing the gate voltage of the FET to determine the approximate secondary-side conduction time delay.

32. A lamp comprising:

a switching power converter;

a load coupled to the switching power converter; and

a controller coupled to the switching power converter to control the switching power converter, wherein the controller is configured to;

receive one or more signals from the switching power converter;

process the one or more signals to determine an approximate secondary-side conduction time delay that occurs from cessation of primary-side current conduction in a transformer of the switching power converter until conduction begins in a secondary-side current in the transformer;

determine the secondary-side current conduction time utilizing the secondary-side conduction time delay;

determine an approximate amount of charge transferred to the secondary-side of the transformer using the determined secondary-side current conduction time; and

generate a current control signal to control power delivered to a load coupled to the switching power converter based on the determined approximate amount of charge transferred to the secondary-side of the transformer.

33. The lamp of claim 32 wherein the load comprises one or more light emitting diodes.