STEVAL-ILL013V1 Datasheet, PDF (7/43 Pages) STMicroelectronics – 80 W offline LED driver with PFC

Design concept
UM0670
Figure 3 illustrates a high PF boost converter design concept. Two additional features are
implemented in the application and these improvements are shown in the blue segments.
The first improves circuit behavior during startup (see Section 10.1 for a description) and the
second allows the dimming of the LED down to 0%, or no LED brightness (description
provided in Section 10.2).
Figure 4 shows the design concept of a modified buck converter with a dimming function.
The output LED current is adjusted by setting the proper sense resistor size via the jumpers
(to adjust maximum LED current), together with the proper setting of the capacitor used in
the FOT network (adjust minimum LED current). The external PWM generator provides
a PWM signal between 0 and 100% for brightness regulation. This signal is connected
through a diode to the current sense pin and allows control of LED brightness.
Figure 3. High PF boost converter design concept
VIN = 88 V
to 265 V AC
Vc = 16 V
Supplying PWM generator with ST7LITEU05
Supplying L6562A in modified BUCK converter
STTH1L06
Input EMI filter
ZCD COMP INV
D104
VCC _{L6562A GD}
MULT
GND
CS
C110
C107
STP8NM50FP
VOUT = 400 V
Proper startup
Allowing
0% dimming
AM00413
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Doc ID 15327 Rev 2