AN2994 Datasheet, PDF (18/38 Pages) STMicroelectronics – 400 W FOT-controlled PFC pre-regulator with the L6563S

Test results and significant waveforms
AN2994
2.4
Start-up and RUN pin
Figure 27 and Figure 28 show the waveforms during the start-up of the circuit, at mains
plug-in. The Vcc voltage rises up to the turn-on threshold, and the L6563S starts the
operation. For a short time the energy is supplied by the Vcc capacitor, then the auxiliary
winding and the charge pump circuit take over. At the same time, the output voltage rises
from the peak value of the rectified mains to the nominal value of the PFC output voltage.
The good phase margin of the compensation network allows a clean start-up, without any
large overshoot.
Figure 27. EVL6563S-400W start-up
at 90 Vac, 60 Hz, full load
Figure 28. EVL6563S-400W start-up
at 265 Vac, 50 Hz, full load
CH1: Output voltage
CH2: Pin #14 - Vcc voltage
CH3: Pin #10 - RUN
CH4: Pin #13 - Gate drive
CH1: Output voltage
CH2: Pin #14 - Vcc voltage
CH3: Pin #10 - RUN
CH4: Pin #13 - Gate drive
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Doc ID 15796 Rev 2