STMicroelectronics EVALHVLED815W10 and EVALHVLED815W15 Evaluation Board for the Offline LED Driver with Primary-Sensing and High Power Fact EVALHVLED815W10 Hoja De Datos
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EVALHVLED815W10
Device description
HVLED815PF
26/34
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
with very low stress on the power circuit. This special condition is illustrated in the timing
diagram of
Figure 21. Hiccup mode OCP: timing diagram
4.11
High power factor implementation
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
application a different reference schematic can be used; refer to AN4346 application note
for further details.
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
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
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