Pwm controller for synchronous rectifier of flyback power converter

a technology of synchronous rectifier and flyback power converter, which is applied in the direction of power conversion system, dc-dc conversion, climate sustainability, etc., can solve problems such as increasing complexity
US20060018135A1Active Publication Date: 2006-01-26SEMICON COMPONENTS IND LLC
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Patent Information

Authority / Receiving Office
US · United States
Current Assignee / Owner
SEMICON COMPONENTS IND LLC
Publication Date
2006-01-26

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Abstract

A synchronous rectifier PWM (SR-PWM) controller controls a MOSFET in response to the value of a secondary current and the status of a synchronous signal for both discontinuous and continuous operation mode. The secondary current is generated in a secondary circuit and is detected by two threshold-detection terminals of the SR-PWM controller. The SR-PWM controller produces the synchronous signal by detecting a switching signal of the transformer via a detection terminal of the SR-PWM controller. Furthermore, a delay-time is inserted after the MOSFET is turned off and before the next switching cycle starts to ensure a proper operation of the MOSFET. In one embodiment, an equivalent series resistance (ESR) of an output capacitor can be used as a sensor to detect the secondary current. Therefore, no additional current sensor is required and the efficiency can be improved.
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Description

BACKGROUND OF THE INVENTION

[0001] 1. Filed of the Invention

[0002] The present invention relates to a pulse width modulation (PWM) controller of flyback power converter, and more particularly, to a synchronous rectifier PWM controller (SR-PWM) for a flyback power converter to improve efficiency of power conversion.

[0003] 2. Description of Related Art

[0004] Power converters have been frequently used for converting an unregulated power source to a constant voltage source. Among various power converters, flyback topology is the most common one. A transformer having a primary winding and a secondary winding is the major part of a flyback power converter. In application, the primary winding is connected to the unregulated power source, preferably a DC voltage source, and a switching device is connected to the primary winding to switch on and off the connection between the unregulated power source and the primary winding. A rectifying diode is typically connected to the secondary windi...

Claims

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