Switching power converter and method of controlling output voltage thereof using predictive sensing of magnetic flux
First Claim
1. A control circuit for controlling a switching power converter, wherein said switching power converter includes a power magnetic element having at least one power winding, a second winding, a switching circuit for periodically energizing said at least one power winding, wherein said control circuit controls said switching circuit, and wherein said control circuit comprises:
- an integrator having an input coupled to said second winding for providing an output representing an amount of magnetic energy storage in said power magnetic element;
a comparison circuit for detecting when said output of said integrator indicates that said amount of magnetic energy storage has reached a level substantially equal to zero;
a sampling circuit having a signal input coupled to said second winding and a control input coupled to an output of said comparison circuit for sampling a voltage of said second winding in conformity with said integrator indicating that said amount of magnetic energy storage has reached said substantially zero level; and
a switch control circuit having an output coupled to said switching circuit and having an input coupled to an output of said sampling circuit, whereby said switching circuit is controlled in conformity with said sampled voltage.
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Accused Products
Abstract
A switching power converter and method of controlling an output voltage thereof using predictive sensing of magnetic flux provides a low-cost switching power converter via primary-side control using a primary-side winding. An integrator generates a voltage that represents flux within a magnetic element by integrating a primary-side winding voltage. A detection circuit detects the end of a half-cycle of post-conduction resonance that occurs in the power magnetic element subsequent to zero energy level in the power magnetic element. The integrator voltage is stored at the end of the half-cycle and is used to determine a sampling point prior to or equal to the start of post-conduction resonance in a subsequent switching cycle of the power converter. The primary-side winding voltage is then sampled at the sampling point, providing an indication of the output voltage of the power converter by which the output voltage of the converter can be controlled.
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Citations
31 Claims
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1. A control circuit for controlling a switching power converter, wherein said switching power converter includes a power magnetic element having at least one power winding, a second winding, a switching circuit for periodically energizing said at least one power winding, wherein said control circuit controls said switching circuit, and wherein said control circuit comprises:
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an integrator having an input coupled to said second winding for providing an output representing an amount of magnetic energy storage in said power magnetic element; a comparison circuit for detecting when said output of said integrator indicates that said amount of magnetic energy storage has reached a level substantially equal to zero; a sampling circuit having a signal input coupled to said second winding and a control input coupled to an output of said comparison circuit for sampling a voltage of said second winding in conformity with said integrator indicating that said amount of magnetic energy storage has reached said substantially zero level; and a switch control circuit having an output coupled to said switching circuit and having an input coupled to an output of said sampling circuit, whereby said switching circuit is controlled in conformity with said sampled voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A control circuit for controlling a switching power converter, wherein said switching power converter includes a power magnetic element having at least one power winding and a second winding, a switching circuit for periodically energizing said at least one power winding, wherein said control circuit control said switching circuit, said wherein said control circuit comprises:
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a first detection circuit having an input coupled to said second winding for detecting a zero magnetic energy storage cycle point of a post-conduction resonance condition of said power magnetic element; a second detection circuit coupled to an output of said first detection circuit for detecting a beginning of a subsequent post-conduction resonance condition of said power magnetic element in conformity with an output of said first detection circuit that indicates said detected zero magnetic energy storage cycle point; a sampling circuit having a control input coupled to said second detection circuit for sampling a voltage of said second winding at a time preceding or equal to said beginning of said subsequent post-conduction resonance condition; and a switch control circuit having an output coupled to said switching circuit and having an input coupled to an output of said sampling circuit, whereby said switching circuit is controlled in conformity with said sampled voltage. - View Dependent Claims (15, 16, 17)
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18. A method of controlling a switching power converter, comprising:
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periodically energizing a power magnetic storage element; sensing magnetic flux in said power magnetic storage element via a second winding; integrating a first voltage across said second winding to determine a second voltage corresponding to a level of magnetic energy storage in said power magnetic storage element; comparing said second voltage to a threshold to determine a sampling time at which said level of magnetic energy storage is substantially equal to zero; sampling said first voltage at said sampling time; and controlling subsequent energizing of said magnetic storage element in conformity with said sampled first voltage. - View Dependent Claims (19, 20, 21, 22, 23)
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24. A method of controlling a switching power converter, comprising:
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periodically energizing a magnetic storage element; sensing magnetic flux in said magnetic storage element via a second winding; first detecting a zero magnetic energy storage cycle point of a post-conduction resonance condition of said power magnetic storage element in conformity with said sensed magnetic flux; second detecting a beginning of a subsequent post-conduction resonance condition of said power magnetic element in conformity with a result of said first detecting; sampling a voltage of said second winding at a time preceding or equal to said beginning of said subsequent post-conduction resonance condition; and controlling subsequent energizing of said magnetic storage element in conformity with said sampled voltage. - View Dependent Claims (25, 26, 27)
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28. A switching power converter comprising:
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a power magnetic element having at least one power winding and a second winding; a switching circuit for periodically energizing said at least one power winding; and a control circuit, comprising; an integrator having an input coupled to said second winding for providing an output representing an amount of magnetic energy storage in said power magnetic element, a comparison circuit for detecting when said output of said integrator indicates that said amount of magnetic energy storage has reached a level substantially equal to zero, a sampling circuit having a signal input coupled to said second winding and a control input coupled to an output of said comparison circuit for sampling a voltage of said second winding in conformity with said integrator indicating that said amount of magnetic energy storage has reached said substantially zero level, and a switch control circuit having an output coupled to said switching circuit and having an input coupled to an output of said sampling circuit, whereby said switching circuit is controlled in conformity with said sampled voltage. - View Dependent Claims (29, 30, 31)
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Specification