RESONANT SWITCHING POWER CONVERTER WITH BURST MODE TRANSITION SHAPING

• US 20100020570A1
• Filed: 09/30/2008
• Published: 01/28/2010
• Est. Priority Date: 07/25/2008
• Status: Active Grant

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Melanson, John L., Gaetano, Mauro L.
• Granted Patent: US 8,014,176 B2
• Time in Patent Office: Days
• US Class Current: 363/26
• CPC Class Codes: H01F 2038/026 non-linear inductive arrangements for converters, e.g. with additional windings
• CPC Class Codes: H01F 3/10 Composite arrangements of magnetic circuits
• CPC Class Codes: H01F 3/14 Constrictions; Gaps, e.g. air-gaps in magnetic shunt paths H01F3/12
• CPC Class Codes: H01F 38/02 for non-linear operation
• CPC Class Codes: H01F 38/08 High-leakage transformers or inductances
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 1/42 Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
• 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 resonant switching power converter having burst mode transitioning operates during low or zero load conditions with reduced audible noise and component stresses, while improving efficiency. Pulse bursts are generated with a beginning and/or ending pulse duration that differs from mid-burst pulse durations, in order to reduce an amplitude of transients otherwise generated at the beginning and/or end of the bursts. Alternatively, the spacing between the pulses at the beginning and/or end of the bursts may differ from the spacing between the pulses in the middle of the bursts to reduce the transient(s). A number of pulses at the beginning and/or end of the burst can also be set with gradually varying durations, to further reduce component stress and audible vibration in a transformer that couples the resonant tank to the output of the converter.

Claims

1. A resonant switching power circuit, comprising:

a resonant circuit including at least one inductance and at least one capacitance for transferring energy to an output of the resonant switching power circuit;

a switching circuit coupled to the resonant circuit for transferring energy from an input voltage source to the resonant circuit; and

a control circuit for controlling the switching circuit, wherein the control circuit has a burst mode of operation in which a number of pulses are generated in bursts to provide the energy to the output of the resonant switching power circuit intermittently when energy demand at the output of the resonant switching power circuit is low, and wherein the pulses within the bursts have a non-uniform pattern such that at least one transient at the start or end of the burst is reduced in amplitude.

2. The resonant switching power circuit of claim 1, wherein at least one ending pulse of the bursts has a predetermined duration that differs from another predetermined duration of pulses in a middle of the bursts.

3. The resonant switching power circuit of claim 1, wherein at least one beginning pulse of the bursts has another predetermined duration that differs from the duration of the pulses in the middle of the bursts.

4. The resonant switching power circuit of claim 1, wherein a time interval between an initial two pulses of the bursts differs from another time interval between a second pulse and a third pulse of the bursts.

5. The resonant switching power circuit of claim 1, wherein the at least one ending pulse of the bursts is a single pulse.

6. The resonant switching power circuit of claim 5, wherein the predetermined duration of the at least one ending pulse of the bursts is substantially equal to half of the another predetermined duration of the pulses in the middle of the bursts.

7. The resonant switching power circuit of claim 1, wherein the at least one ending pulse of the bursts comprises at least two pulses.

8. The resonant switching power circuit of claim 7, wherein a polarity of a first pulse of the bursts is alternated between the bursts.

9. The resonant switching power circuit of claim 8, wherein the at least two pulses have durations such that a non-zero voltage offset is present at the output of the switching circuit after both of the at least two pulses have terminated, wherein first pulses of the bursts have the same polarity as the non-zero voltage offset, whereby a voltage step at the output of the switching circuit due to the first pulses of the bursts is reduced in magnitude.

10. The resonant switching power circuit of claim 1, wherein a polarity of a first pulse of the bursts is alternated between the bursts.

11. The resonant switching power circuit of claim 1, wherein the number of pulses in each burst is an even number of pulses.

12. The resonant switching power circuit of claim 1, wherein a start time of at least one ending pulse of the bursts is delayed such that a non-zero voltage offset is present at the output of the switching circuit after the at least one ending pulse has terminated, wherein first pulses of the bursts have the same polarity as the offset present at the output of the switching circuit at the start of the first pulses of the bursts, whereby a voltage step at the output of the switching circuit due to the first pulses of the bursts is reduced in magnitude.

13. A method of reducing transient amplitude during low power burst mode operation in a resonant switching power circuit, the method comprising:

transferring energy to an output of the resonant switching power circuit from a resonant tank circuit;

transferring energy from an input voltage source to the resonant circuit by operating a switching circuit; and

operating the switching circuit in the burst mode, in which a number of pulses are generated in bursts to provide the energy to the output of the resonant switching power circuit intermittently when energy demand at the output of the resonant switching power circuit is low, and wherein the pulses within the bursts have a non-uniform pattern such that at least one transient at the start or end of the burst is reduced in amplitude.

14. The method of claim 13, wherein at least one ending pulse of the bursts has a predetermined duration that differs from another predetermined duration of pulses in a middle of the bursts.

15. The method of claim 13, wherein at least one beginning pulse of the bursts has another predetermined duration that differs from the duration of the pulses in the middle of the bursts.

16. The method of claim 13, wherein a time interval between an initial two pulses of the bursts differs from another time interval between a second pulse and a third pulse of the bursts.

17. The method of claim 13, wherein the at least one ending pulse of the bursts is a single pulse.

18. The method of claim 17, wherein the predetermined duration of the at least one ending pulse of the bursts is substantially equal to half of the another predetermined duration of the pulses in the middle of the bursts.

19. The method of claim 13, wherein the at least one ending pulse of the bursts comprises at least two pulses.

20. The method of claim 19, wherein a polarity of a first pulse of the bursts is alternated between the bursts.

21. The method of claim 20, wherein the at least two pulses have durations such that a non-zero voltage offset is present at the output of the switching circuit after both of the at least two pulses have terminated, wherein the at least two pulses have durations such that a non-zero voltage offset is present at the output of the switching circuit after both of the at least two pulses have terminated, wherein first pulses of the bursts have the same polarity as the non-zero voltage offset, whereby a voltage step at the output of the switching circuit due to the first pulses of the bursts is reduced in magnitude.

22. The method of claim 13, wherein a polarity of a first pulse of the bursts is alternated between the bursts.

23. The method of claim 13, wherein the number of pulses in each burst is an even number of pulses.

24. The method of claim 13, wherein a start time of at least one ending pulse of the bursts is delayed such that a non-zero voltage offset is present at the output of the switching circuit after the at least one ending pulse has terminated, wherein first pulses of the bursts have the same polarity as the offset present at the output of the switching circuit at the start of the first pulses of the bursts, whereby a voltage step at the output of the switching circuit due to the first pulses of the bursts is reduced in magnitude.

25. An integrated circuit controller, integrated on a single die, for a controlling a resonant switching power converter, wherein the integrated circuit controller provides control signals to a switching circuit having a low-power burst mode, in which a number of pulses are generated in bursts when energy demand at an output of the resonant switching power converter is low, and wherein the pulses within the bursts have a non-uniform pattern such that at least one transient at the start or end of the burst is reduced in amplitude.

26. The integrated circuit controller of claim 25, wherein at least one beginning or ending pulse of the bursts has another predetermined duration that differs from the duration of the pulses in the middle of the bursts.

27. The integrated circuit controller of claim 26, wherein the switching circuit is integrated on the die.