Datasheet

AN3119 Test results and significant waveforms
Doc ID 16849 Rev 2 19/32
4.4 Startup operation
Figure 29 and 30 show the waveforms during the startup of the circuit at mains plug-in.
The R5 and R11 startup resistors charge the Vcc C9 capacitor, therefore Vcc voltage rises
up to the turn-on threshold, and the L6563S starts operating. For a short time the energy is
supplied by the Vcc capacitor, and then the auxiliary winding with the charge pump circuit
takes over.
Because the startup resistors are always connected to the mains, their power consumption
during normal operation might affect the efficiency of the power supply once it operates at
light load. Therefore the value of the startup resistors must be found as a compromise
between the startup time at minimum input mains and the power dissipation at maximum
input mains.
In Figure 28 and 29 the waveforms during startup of the circuit at mains plug-in are shown.
Notice that because the Vcc voltage rise depends on the input voltage, the wake-up time is
dependent on the input mains voltage.
The same figures show that the output voltage rises from the peak value of the rectified
mains to the nominal value of the PFC output voltage and the good phase margin of the
compensation network allows a clean startup without overshoot.
Figure 29. EVL6563S-250W TM PFC: startup at
90 Vac-60 Hz - full load
Figure 30. EVL6563S-250W TM PFC: startup at
265 Vac-50 Hz - full load
CH1: PFC output voltage
CH2: Vcc voltage (pin #14)
CH3: RUN (pin #10)
CH4: gate drive (pin #13)
CH1: PFC output voltage
CH2: Vcc voltage (pin #14)
CH3: RUN (pin #10)
CH4: gate drive (pin #13)