VARIABLE BLANKING FREQUENCY FOR RESONANT CONVERTERS
First Claim
Patent Images
1. A power supply comprising:
- a feedback circuit that is configured to generate a feedback voltage that is indicative of a load condition of the power supply;
a transistor that is connected to a primary winding of a transformer; and
a controller integrated circuit (IC) comprising a first pin that is configured to receive the feedback voltage and a second pin that is configured to output a drive signal to a gate of the transistor to control a switching operation of the transistor by quasi-resonant switching,wherein the controller IC is configured to adjust the feedback voltage with a programming voltage to generate an adjusted feedback voltage, to turn off the transistor based on the feedback voltage, to detect a resonant ring on a node of the transistor when the transistor is turned off, to prevent the transistor from being turned on during a blanking time, to adjust the blanking time based on the adjusted feedback voltage, and to turn on the transistor based on a level of the resonant ring after expiration of the blanking time.
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Abstract
A power supply includes a transistor that is connected to a primary winding of a transformer. A controller controls a switching operation of the transistor by quasi-resonant switching. The controller receives a feedback voltage and adjusts the feedback voltage to adjust a blanking frequency, which is an inverse of a blanking time during which the transistor is prevented from being turned on. The controller turns on the transistor after expiration of the blanking time based on a level of a resonant ring.
23 Citations
20 Claims
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1. A power supply comprising:
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a feedback circuit that is configured to generate a feedback voltage that is indicative of a load condition of the power supply; a transistor that is connected to a primary winding of a transformer; and a controller integrated circuit (IC) comprising a first pin that is configured to receive the feedback voltage and a second pin that is configured to output a drive signal to a gate of the transistor to control a switching operation of the transistor by quasi-resonant switching, wherein the controller IC is configured to adjust the feedback voltage with a programming voltage to generate an adjusted feedback voltage, to turn off the transistor based on the feedback voltage, to detect a resonant ring on a node of the transistor when the transistor is turned off, to prevent the transistor from being turned on during a blanking time, to adjust the blanking time based on the adjusted feedback voltage, and to turn on the transistor based on a level of the resonant ring after expiration of the blanking time. - View Dependent Claims (2, 3, 4, 5)
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6. A controller integrated circuit (IC) for a power supply:
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a driver that is configured to drive a transistor that is connected to a primary winding of the power supply; a valley detection circuit that is configured to detect a resonant valley of a resonant ring on a primary side of the power supply when the transistor is turned off; and a blanking frequency generator that is configured to generate a blanking time based on a feedback signal that is indicative of a load condition of the power supply, and to adjust the feedback signal based on a level of an input line voltage to the power supply, wherein the controller IC is configured to turn off the transistor based on the feedback signal, to prevent the transistor from being turned on during the blanking time, and to turn on the transistor in response to detecting the resonant valley after expiration of the blanking time. - View Dependent Claims (7, 8, 9, 10, 11)
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12. A power supply comprising:
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a transformer comprising a primary winding and a secondary winding; a feedback circuit that is configured to generate a feedback voltage indicative of a load condition of the power supply; a transistor that is coupled to the primary winding of the transformer; and a controller that is configured to control a switching operation of the transistor in accordance with quasi-resonant (QR) switching, to detect a line voltage input to the power supply, to turn off the transistor based on the feedback voltage, to detect a resonant ring when the transistor is turned off, to prevent the transistor from being turned on during a blanking time, to adjust the blanking time based on the detected line voltage, and to turn on the transistor based on a level of the resonant ring after expiration of the blanking time. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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Specification