Datasheet

Test results and significant waveforms AN2994
16/38 Doc ID 15796 Rev 2
Figure 25 shows the circuit’s behavior in the case of a mains dip: as previously described,
the internal circuitry has detected the decreasing of the mains voltage and has activated the
C
FF
internal fast discharge. As you can see in this case, the output voltage changes but
within a few mains cycles it comes back to the nominal value. The situation is different if we
check the performance of a controller without the V
FF
function. Figure 26 shows the
behavior of a PFC using the L6562A operating in FOT and delivering a similar output power:
in the case of a mains dip from 140 to 90 Vac, the output voltage variation is not very
different but the output voltage requires a longer time to restore the original value.
Doing tests with a wider voltage variation (for example, 265 to 90 Vac) the output voltage
variation of a PFC without the voltage feed-forward fast discharge is much more
emphasized.
Figure 23. EVL6563S-400W input mains surge
from 90 Vac to 140 Vac, full load,
C
FF
= 1 µF
Figure 24. L6562A FOT input mains surge
from 90 Vac to 140 Vac, full load,
NO V
FF
input
CH1: Output voltage CH1: Output voltage
CH2: Input rectified mains voltage CH2: Input rectified mains voltage
CH3: V
FF
voltage - pin #5 CH4: Input current
CH4: Input current