STMicroelectronics EVALHVLED815W10 and EVALHVLED815W15 Evaluation Board for the Offline LED Driver with Primary-Sensing and High Power Fact EVALHVLED815W10 データシート

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DocID023409  Rev 5

Ultimately, this will result in a low-frequency intermittent operation (hiccup mode operation), 
with very low stress on the power circuit. This special condition is illustrated in the timing 
diagram of 

Referring to the principle application schematic in 

, two contributions are 

added on the CS pin in order to implement the high power factor capability (trough R

PF

 

resistor) and keeping a good line regulation (trough R

OS

 resistor). The application 

schematic on 

 is intended for a single range input voltage. For wide range 

application a different reference schematic can be used; refer to AN4346 application note 
for further details.

Through the R

PF

 resistor a contribution proportional to the input voltage is added on the CS 

pin: as a consequence the input current is proportional to the input voltage during the line 
period, implementing a high power factor correction. The contribution proportional to the 
input voltage is generated using the auxiliary winding, as a consequence a diode in series to 
the R

PF

 resistor is needed.

Through the R

OS

 resistor a positive contribution proportional to the average value of the 

input voltage is added on the CS pin in order to keep a good line regulation.

The voltage contribution proportional to the average value of the input voltage is generated 
trough the low pass filter R

A

/R

B

 resistor and C

OS

 capacitor. A diode in series to the R

A

/R

B

 

resistor is suggested to avoid the discharge of C

OS

 capacitor in any condition.

The R

1

 resistor between CS and SOURCE pin is needed to add on the CS pin also the 

contribution proportional the output current trough the R

SENSE

 resistor. 

AM13571v1

V

DS

Vcc

ON

Vcc

OFF

Vcc

rest

Secondary diode is shorted here

t

t

t

V

CS

1 V

Two switching cycles

V

CC

Vcs

dis