Functional check

AN3089

12/25

DocID16493 Rev 2

switching frequency has been set at 165 kHz. For this reason, the L6566B skips the first

valley signal on ZCD and switches on the MOSFET at the second negative-going edge.

3.1

Standby and no load operation

In Figure 8 and Figure 9, some no load waveforms are captured. As shown, the L6566B

works in the burst mode. When the feedback voltage at the COMP pin falls below 2.65 V

(typical), the IC is disabled and its consumption is reduced. The chip is re-enabled as the

voltage on the COMP pin rises over this threshold again. Therefore, the residual

consumption of the PFC control circuitry is minimized to a negligible level.

Figure 6. Flyback stage waveforms at 115 V –

60 Hz – light-load

Figure 7. Flyback stage waveforms at 230 V –

50 Hz – light-load

CH1: drain voltage

CH2: CS pin voltage

CH1: drain voltage

CH2: CS pin voltage

CH3: ZCD pin

CH4: bulk voltage

CH3: ZCD pin

CH4: bulk voltage

Figure 8. No load operation at 90 V – 50 Hz

Figure 9. No load operation at 265 V – 50 Hz

CH1: drain voltage

CH2: COMP pin

CH1: drain voltage

CH2: COMP pin

CH3: Output voltage

CH4: bulk voltage

CH3: Output voltage

CH4: bulk voltage