Patent ID: 6400583
Filing Date: 2002-06-04
Classification: H02M,Y02B

Abstract:
A flyback converter with synchronous rectifying, comprising:a power source; a flyback switch circuit coupled to said power source to output a high frequency pulse; a transformer having a primary coil coupled to said flyback switch circuit to receive said high frequency pulse, the transformer having two secondary coils including a master source and a sub-source; a synchronous switch connected with a first diode and receiving a sequence driving pulse, the synchronous switch turned on simultaneously with said output diode, and connected to a load, the synchronous switch including an equivalent conducting resistance; a synchronous rectifier coupled to said sub-source, and coupled with the equivalent conducting resistor of said synchronous switch to output a signal; a logic circuit coupled to said sub-source via a second diode and a capacitor, and receiving said signal from said synchronous rectifier to output a signal to avoid vibration of said sequence driving pulse; a fast charging/discharging path coupled between said sub-source and a gate electrode of said synchronous switch; and, a buffer coupled between said fast charging/discharging path and said master source, and receiving said signal from said logic circuit to output said sequence driving pulse to drive said synchronous switch to be turned on simultaneously; wherein, said equivalent conducting resistor of said synchronous switch detects the current of said load to enable said synchronous rectifier, said logic circuit and said buffer to sequentially output said sequence driving pulse for said synchronous switch.