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

Active Publication Date: 2006-01-26
SEMICON COMPONENTS IND LLC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0026]FIG. 9 is a schematic diagram illustrating a SR-PWM controller for control the synchronou

Problems solved by technology

Furthermore, in the above approaches, the transformer requires an additional auxiliary winding to gene

Method used

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  • Pwm controller for synchronous rectifier of flyback power converter
  • Pwm controller for synchronous rectifier of flyback power converter
  • Pwm controller for synchronous rectifier of flyback power converter

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Embodiment Construction

[0027] Referring to FIG. 4, it illustrates a Synchronous Rectifier PWM (SR-PWM) controller 50 for a flyback power converter according to one embodiment of the present invention. In FIG. 4, the flyback power converter includes a transformer 10 having a primary winding NP coupled to a primary circuit and a secondary winding NS coupled to a secondary circuit. In the primary circuit, the primary winding NP is coupled between an input voltage source VIN and a switching device 5. The secondary circuit includess a MOSFET 20, an output capacitor 30, and the SR-PWM controller 50. A drain of the MOSFET 20 is connected to a terminal B of the secondary winding NS. The output capacitor 30 is connected between a terminal A of the secondary winding NS and an output terminal of the secondary circuit. The SR-PWM controller 50 is coupled to the MOSFET 20. A resistor 90 serves as a current sensor, which is coupled between a source of the MOSFET 20 and a negative terminal of the output capacitor 30. Th...

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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.

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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Application Information

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IPC IPC(8): H02M3/335
CPCY02B70/1475H02M3/33592Y02B70/10
Inventor YANG, TA-YUNGKUO, JUN-JIECHEN, TSO MIN
Owner SEMICON COMPONENTS IND LLC
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