Test results and significant waveforms

AN4077

14/33

Doc ID 022997 Rev 1

In

Figure 16 and Figure 17 the detail of the waveforms at switching frequency allows the

operation of the transition mode control to be seen: once the inductor has transferred all the

energy stored, a falling edge on the ZCD pin (pin #11) is detected and it triggers a new ON-

time by setting the gate drive high. As soon as the current signal on the CS pin (pin #4) has

reached the level programmed by the internal multiplier circuitry according to the input

mains instantaneous voltage and the error amplifier output level, the gate drive is set low

and MOSFET conduction is stopped. A following OFF-time transfers the energy stored in

the inductor into the output capacitor and to the load. At the end of the current conduction a

new demagnetization is detected by the ZCD that provides for a new ON-time of the

MOSFET.

Figure 14.

L6564H 100 W TM PFC

demonstration board: Vds and

full load

Figure 15.

L6564H 100 W TM PFC

demonstration board: zoom of Vds

50 Hz-full load

AM11508v1

CH1: Q1 Drain voltage

CH2: MULT voltage - Pin # 3

-

CH4: L 2 inductor current

AM11509v1

CH1: Q1 Drain voltage

CH2: MULT voltage - Pin # 3

-

CH4: L 2 inductor current