Drive circuits for synchronous rectifiers
AssigneeLambda Electronics, Inc.
InventorIsaac Cohen
Life of this patent
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Abstract
A method and system for providing synchronous rectification in power converters that includes controlling turnoff of a synchronous rectifier according to a timing signal representative of the switching time of a switch that is coupled to input of the power converter. Such a timing signal may be obtained directly or indirectly in various ways; for example, by sensing the voltage across the primary switch, or by sensing the drive voltage of the primary switch. Additional alternatives in an isolated converter having a transformer with a primary winding that is selectively coupled to the electrical power source includes sensing the primary winding voltage, for example, by directly sensing the primary voltage or by sensing the voltage across an auxiliary winding that is closely coupled to the primary winding.
Claims44
A power converter, comprising:
- a primary switch that repetitively switches between a conductive state and a substantially non-conductive state to selectively connect an input of said power converter to an electrical power source;
- a detection circuit that senses the approximate switch timing of said primary switch to provide a timing signal representative of the primary switch timing;
- and
- a rectifier device that includes a conduction control terminal and a bi-directional conduction path selectively enabled by said conduction control terminal, such that when said conduction control terminal is driven ON said bi-directional conduction path is activated to conduct an output current provided to an output of said power converter, and when said conduction control terminal is driven OFF said bi-directional conduction path is de-activated, wherein said conduction control terminal is driven OFF based on said timing signal to de-activate said bi-directional conduction path at a time such that the magnitude of the current conducted by said rectifier device is not substantial relative to the magnitude of the output current and such that substantial cross-conduction does not occur.
A power converter comprising:
- a primary switch that repetitively switches between a conductive state and a substantially non-conductive state to selectively connect an input of said power converter to an electrical power source;
- a rectifier that includes a conduction control terminal and a bi-directional conduction path selectively enabled by said conduction control terminal, such that when said conduction control terminal is driven ON said bi-directional conduction path is activated to conduct an output current provided to an output of said power converter, and when said conduction control terminal is driven OFF said bi-directional conduction path is de-activated;
- and
- a drive control circuit that provides a timing signal representative of the approximate switch timing of said primary switch and that, based on said timing signal, drives said conduction control terminal OFF to de-activate said bi-directional conduction path at a time such that the magnitude of the current conducted by said rectifier device is not substantial relative to the magnitude of the output current and such that substantial cross-conduction does not occur.
Dependencies are inferred from the claim text.