Power converter and control method therefor
AssigneeSemiconductor Components Industries, LLC
InventorsYung-I Chang, Kuo-Hsien Huang
Life of this patent
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Abstract
A power converter and a control method therefor are provided. The power converter includes a transformer, synchronous rectifier and a control circuit. A primary side of the transformer receives an input voltage, and a secondary side of the transformer generates a sensing signal. The synchronous rectifier is coupled to the secondary side of the transformer. The control circuit receives the sensing signal and detects a changing slope of the sensing signal, and accordingly generates a control signal to control the synchronous rectifier to be turned on or turned off, so as to regulate an output voltage of the power converter.
Claims20
A control circuit for a synchronous rectifier comprising:
- the control circuit configured to form a control signal to control the synchronous rectifier wherein the synchronous rectifier is configured to be coupled to a secondary winding of a transformer and conduct a secondary current of the transformer;
- the control circuit configured to receive a sense signal from the secondary winding wherein the sense signal is representative of the secondary current;
- the control circuit configured to enable the synchronous rectifier, determine a value of the sense signal at one or more time intervals after enabling the synchronous rectifier, and use the value and the one or more time intervals to determine another time interval for a substantially zero crossing of the secondary current, and to disable the synchronous rectifier at substantially the another time interval.
A method of forming a synchronous rectifier control circuit comprising:
- configuring the control circuit to form a control signal to control the synchronous rectifier for controlling a secondary current of a secondary winding of a transformer;
- configuring the control circuit to receive a sense signal that is representative of the secondary current;
- and
- forming the control circuit to determine a first value of the sense signal, to delay a first time interval and determine a second value of the sense signal, to use the first time interval and the first and second values to determine a time length at which the secondary current will be substantially zero, and to disable the synchronous rectifier substantially at expiration of the time length.
A method of forming a synchronous rectifier control circuit comprising:
- forming the control circuit to control the synchronous rectifier for controlling a secondary current of a secondary winding of a transformer, and to receive a sense signal that is representative of the secondary current;
- and
- configuring the control circuit to determine a slope of the sense signal during at least a portion of a first time interval that the synchronous rectifier is enabled, to determine from the slope a second time interval for a substantially zero crossing of the secondary current, and to disable the synchronous rectifier according to the second time interval.
A control circuit for a synchronous rectifier comprising:
- the control circuit configured to form a control signal to control the synchronous rectifier wherein the synchronous rectifier is configured to be coupled to a secondary winding of a transformer and conduct a secondary current of the transformer;
- the control circuit configured to receive a sense signal from the secondary winding wherein the sense signal is representative of the secondary current;
- the control circuit configured to enable the synchronous rectifier, determine a value of the sense signal at one or more time intervals after enabling the synchronous rectifier, and use the value and the one or more time intervals to determine another time interval for a substantially zero crossing of the secondary current, and to disable the synchronous rectifier at substantially the another time interval wherein the control circuit includes a sampling circuit having one or more storage elements configured to sample and store the value of the sense signal.
Dependencies are inferred from the claim text.