INTRODUCTION Three different configurations that an L6561 based flyback converter can assume have been identified They are illustrated in fig Configurations a and b are basically conventional flyback converters The former works in TM Transi tion Mode i e on the boundarybetween continuous and discontinuous inductor current mode therefore at a frequency depending on both input voltage and output current The latter works at a fixed frequency imposed by the synchronisation signal and is there fore completely equivalent to a flyback converter based on a standard PWM controller Configuration c which most exploits the aptitude of the L6561 for performing power factor correction works in TM too but quite differently: the input ca pacitance is so small that the input voltage is very close to a rectified sinusoid Besides the control loop has a narrow bandwidth so as to be little sensitive to the twice mains frequency ripple appearing at the output

INTRODUCTION Three different configurations that an L6561-based flyback converter can assume have been identified. They are illustrated in fig. 1. Configurations a) and b) are basically conventional flyback converters. The former works in TM (Transi- tion Mode, i.e. on the boundarybetween continuous and discontinuous inductor current mode), therefore at a frequency depending on both input voltage and output current. The latter works at a fixed frequency, imposed by the synchronisation signal, and is there- fore completely equivalent to a flyback converter based on a standard PWM controller. Configuration c), which most exploits the aptitude of the L6561 for performing power factor correction, works in TM too but quite differently: the input ca- pacitance is so small that the input voltage is very close to a rectified sinusoid. Besides, the control loop has a narrow bandwidth so as to be little sensitive to the twice mains frequency ripple appearing at the output. March 2000 ? AN1059 APPLICATION NOTE DESIGN EQUATIONS OF HIGH-POWER-FACTOR FLYBACK CONVERTERS BASED ON THE L6561 by Claudio Adragna Despite specific for Power Factor Correction circuits using boost topology, the L6561 can be suc- cessfully used to control flyback converters. Among the various configurations that an L6561-based flyback converter can assume, the high-PF one is particularly interesting because of both its peculiar- ity and the advantages it is able to offer.

• power smps


• large output


• converter


• rms line


• lp ?


• output capacitance


• pf


• high-pf flyback


• primary current