LOW ENERGY TRANSFER MODE FOR AUXILIARY POWER SUPPLY OPERATION IN A CASCADED SWITCHING POWER CONVERTER
First Claim
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:
- 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 converter;
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.
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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.
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Citations
26 Claims
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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 converter; 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 (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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18-1. The integrated circuit of claim 17, wherein in the low energy transfer operating mode, the second switch control circuit has a first pulse repetition rate substantially lower than a second pulse repetition rate of the second switched-power circuit during ordinary operation of the second switched-power circuit.
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19-2. The integrated circuit of claim 18, wherein in the low energy transfer operating mode, the second switch control circuit has a fixed narrowed pulse width substantially shorter than an operating pulse width of the DC-DC converter during ordinary operation of the DC-DC converter.
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20-3. The integrated circuit of claim 18, wherein the second pulse repetition rate is greater than or equal to five times the first pulse repetition rate.
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21-4. The integrated circuit of claim 17, further comprising an auxiliary power supply circuit having a selectable operating mode and having an input coupled to the auxiliary winding and an auxiliary power supply output for supplying power to the control circuit, wherein in a first operating mode of the auxiliary power supply circuit, a first voltage of the auxiliary power supply output is greater than a second voltage of the auxiliary power supply output when the auxiliary power supply circuit is in the second operating mode.
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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 second switched-power circuit includes a magnetic coupling element for coupling the input of the second switched-power circuit to the output of the switched-power circuit and having a primary winding and an auxiliary winding, wherein the second switch control circuit 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 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)
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26. 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