R2A20111SP/DD

REJ03F0231-0100 Rev.1.00 Mar 28, 2007

Page 21 of 40

5-1. Power-Supply Startup Operation

When the AC voltage is applied, the PFC-ON pin voltage starts to rise up. After it has reached 0.82 V, the voltage on

the SS pin starts to be discharged and PFC operation is started with the soft-start function. Once the PFC operation is

started, the voltage on the FB pin rises and is controlled so that it reaches 2.5 V.

Full-wave rectified AC

PFC-ON

SS

CAO

SS

CAO

FB

0.82V

2.5V

PFC output voltage

Figure 9 Waveform in Startup Operation

5-2. Operation when the Power-Supply Stops

When the supply of AC voltage stops, both of the PFC output voltage and the voltage on the FB pin fall. When the

voltage on the FB pin is lower than 0.52 V, the PFC operation stops and the SS pin is reset.

Full-wave rectified AC

FB

SS

0.52V

OUT

Figure 10 Waveform in Stop Operation

Note: When the PFC output voltage is driving light load, the PFC output voltage falls slowly, and the PFC-hold

function may be activated before the voltage on the FB pin falls to 0.52 V. In this case, the PFC hold function

operates, stopping output on the OUT pin and resetting the SS pin.