Low energy transfer mode for auxiliary power supply operation in a cascaded switching power converter
First Claim
1. A cascaded power converter, comprising:
- a first switched-power circuit having an input coupled to a power source and an output coupled to an intermediate node; and
a second switched-power circuit having an input coupled to the intermediate node and an output providing an output of the cascaded power converter, wherein the second switched-power circuit includes a magnetic coupling element for coupling the input of the second switched-power circuit to the output of the first switched-power circuit and having a primary winding and an auxiliary winding, wherein the second switched-power supply includes a control circuit that causes the second switched-power circuit to operate in a low energy transfer operating mode when a voltage at the intermediate node is below a normal operating voltage or when the output of the cascaded power converter is effectively disabled by the control circuit stopping normal switching operation of the second switched-power circuit, wherein in the low energy transfer operating mode, energy sufficient to operate the control circuit from the auxiliary winding is transferred to the auxiliary winding.
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Accused Products
Abstract
A cascaded power converter having an auxiliary power supply operated from the second switching power stage provides efficient operation by activating the auxiliary power supply early in the startup process. A low energy transfer operating mode is initiated in the second switching power stage to charge the auxiliary power supply output without generating significant disruption at the load. After the first switching power stage is started and the intermediate node voltage has increased to a level sufficient to operate the second switching power stage, the final switching power stage enters a normal operating mode. The low energy transfer operating mode has a substantially reduced switching rate and pulse width from that of the normal operating mode.
292 Citations
30 Claims
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1. A cascaded power converter, comprising:
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a first switched-power circuit having an input coupled to a power source and an output coupled to an intermediate node; and a second switched-power circuit having an input coupled to the intermediate node and an output providing an output of the cascaded power converter, wherein the second switched-power circuit includes a magnetic coupling element for coupling the input of the second switched-power circuit to the output of the first switched-power circuit and having a primary winding and an auxiliary winding, wherein the second switched-power supply includes a control circuit that causes the second switched-power circuit to operate in a low energy transfer operating mode when a voltage at the intermediate node is below a normal operating voltage or when the output of the cascaded power converter is effectively disabled by the control circuit stopping normal switching operation of the second switched-power circuit, wherein in the low energy transfer operating mode, energy sufficient to operate the control circuit from the auxiliary winding is transferred to the auxiliary winding. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of controlling a cascaded power converter comprising a first switched-power circuit having an input coupled to a power source and an output coupled to an input of a second switched-power circuit, the method comprising:
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providing a voltage from the power source to the input of the second switched-power circuit; determining that an intermediate voltage at the input of the second switched power circuit is below a normal operating voltage or that the output of the cascaded power converter is effectively disabled by stopping normal switching operation of the second switched-power circuit as an indication that insufficient energy to operate control circuits of the cascaded power converter would be available from an auxiliary winding of a magnetic coupling element of the second switched-power circuit; in response to the indication, operating the second switched-power circuit in a low energy transfer operating mode in which sufficient energy is transferred through the auxiliary winding to operate the control circuit; and generating an auxiliary power supply output for operating at least one of the first switched-power circuit or the second switched-power circuit from a voltage across the auxiliary winding. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. An integrated circuit for controlling a cascaded power converter, comprising:
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a first switch control circuit for operating a power factor converter that generates a DC voltage at an intermediate node from an AC power source; and a second switch control circuit for operating a DC-DC converter having an input coupled to the intermediate node and an output providing an output of the cascaded power converter, wherein the DC-DC converter includes a magnetic coupling element for coupling the input of the DC-DC converter to the output of the cascaded power converter and having a primary winding and an auxiliary winding, wherein the second switch control circuit includes a controller that causes the DC-DC converter to operate in a low energy transfer operating mode when a voltage at the intermediate node is below a normal operating voltage or when the output of the cascaded power converter is effectively disabled by the controller circuit stopping normal switching operation of the DC-DC converter, wherein in the low energy transfer operating mode, energy sufficient to operate the controller is transferred to the auxiliary winding. - View Dependent Claims (24, 25, 26, 27, 28, 29)
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30. A cascaded power converter, comprising:
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multiple switching power stages coupled together in a cascade, wherein an input of a first one of the multiple switching power stages is provided from an input power source; an auxiliary power supply having an input coupled to an auxiliary winding provided on a magnetic coupling element of a second one of the multiple switching power stages, wherein the input has an intermediate voltage; and a control circuit for operating the second one of the multiple switching power stages in a low energy transfer operating mode having at least one of a pulse width or a switching rate substantially lower than another switching rate and another pulse width of a normal operating mode of the second one of the multiple switching power stages, and wherein the control circuit operates the cascaded power converter in the normal operating mode after the first one of the switching power stages has started and the intermediate voltage has reached a level sufficient to operate the second one of the switching power stages.
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Specification