BW6562A Datasheet, PDF (10/15 Pages) Bruckewell Technology LTD – High PFC LED Driver

BW6562A High PFC LED Driver
layout. It is strongly recommended to adopt a smaller RC
filter for higher power application to avoid the CS pin
being damaged by the negative turn-on spike.
Multiplier
The internal multiplier takes two inputs, one from a portion
of the instantaneous rectified line voltage (via pin 3 MULT)
and the other from the output of the E/A (via pin 2 COMP),
to feed the PWM comparator to determine the exact
instant when the MOSFET is to be switched off. The
output of multiplier would be rectified sinusoid as similar as
instantaneous rectified line voltage different only with
scaling factor determined by output of E/A. The output is
then fed into PWM comparator to compare with current
sense clamp voltage V_CS (at 1.08V), to switch MOSFET
off.
The formula governing all parameters is given by
multiplier output :
V_CS K V_MULT (V_COMP – 2.5)
(21)
where K is the multiplier gain. System designer needs to
calculate R1 and R2, for different input mains
circumstances. Figure 1 and 2 explain multiplier
characteristics and V_CS clamps vs. T_J respectively.
Output Drive Stage
An output stage of a push-pull buffer, with typical
+800mA/-600mA driving capability is incorporated to
drive a power MOSFET directly. The output voltage is
clamped at 12V to protect the MOSFET gate even when
the V_CC voltage is higher than 12V.
Figure 1. Multiplier Characteristics
Figure 2. V_CS clamps vs. T_J
© 2012 Bruckewell Technology Corp., Ltd.
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