STMicroelectronics LED815 Evaluation Boards EVALHVLED815W15 EVALHVLED815W15 데이터 시트
제품 코드
EVALHVLED815W15
HVLED815PF
Device description
Doc ID 023409 Rev 4
27/36
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 on
, 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 the dedicated application note for further details.
schematic can be used; refer to the dedicated 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
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 ROS 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.
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 R1 resistor between CS and SOURCE pin is needed to add on the CS pin also the
contribution proportional the output current trough the R
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