Patent ID: 6081432
Filing Date: 2000-06-27
Classification: H02M,Y02B

Abstract:
A circuit comprising:a transformer including primary and secondary windings;a first switch for coupling a first input voltage to said transformer;a second switch for coupling a reset voltage to said transformer;a rectification circuit including a first synchronous rectifier for coupling said secondary winding to an output lead and a second synchronous rectifier for serving as a freewheeling diode, said first and second synchronous rectifiers including control leads coupled to said transformer; anda control circuit for controlling said first and second switches, and for providing a delay between the time said second switch opens and said first switch closes and for providing a delay between the time said first switch opens and said second switch closes, said delays being sufficiently long to ensure that said first and second synchronous rectifiers are not simultaneously conducting, said control circuit including:a duty cycle control circuit having first and second input terminals coupled to output leads of said rectification circuit, and having an output terminal;a first RC delay circuit coupled between said output terminal of the said duty cycle control circuit and a control terminal of said first switch;a first diode having an anode coupled to said control terminal of said first switch and a cathode coupled to said output terminal of said duty cycle control circuit;a second RC delay circuit coupled to said output terminal of said duty cycle control circuit and coupled a control terminal of said second switch; anda second diode having an anode coupled to said control terminal of said second switch and a cathode coupled to a first reference voltage rail.