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
Claudio Adragna