STMicroelectronics L6562A Evaluation Board STEVAL-ILL016V2 STEVAL-ILL016V2 STEVAL-ILL016V2 Fiche De Données

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To generate the synchronization signal on the ZCD pin, the typical approach requires the 
connection between the pin and an auxiliary winding of the boost inductor through a limiting 
resistor. When the device is supplied by the cascaded DC-DC converter, it is necessary to 
introduce a supplementary winding to the PFC choke just to operate the ZCD pin.

Another solution could be implemented by simply connecting the ZCD pin to the drain of the 
power MOSFET through an R-C network as shown in figure 3: in this way the high-
frequency edges experienced by the drain will be transferred to the ZCD pin, hence arming 
and triggering the ZCD comparator. 

Also in this case the resistance value must be properly chosen to limit the current 
sourced/sunk by the ZCD pin. In typical applications with output voltages around 400V, 
recommended values for these components are 22pF (or 33pF) for C

ZCD

 and 330k  for 

R

ZCD

. With these values proper operation is guaranteed even with few volts difference 

between the regulated output voltage and the peak input voltage

 

L6562A

C

ZCD

R

ZCD

5

ZCD