NCL30051LEDGEVB ON Semiconductor, NCL30051LEDGEVB Datasheet - Page 5

• Manufacturer Part Number: NCL30051LEDGEVB
• Description: Power Management IC Development Tools 90-265VAC 60W ISO CC EVB
• Manufacturer: ON Semiconductor
• Type: Power Factor Correctionr

Specifications of NCL30051LEDGEVB

• Rohs: yes
• Product: Evaluation Boards
• Tool Is For Evaluation Of: NCL30051
• Input Voltage: 90 VAC to 265 VAC
• Output Voltage: 35 V to 50 V
• Output Current: 1.5 A

Secondary Side Circuitry
the full−wave, center−tap rectifier, and the associated
secondary side circuitry are shown in the schematic of
Figure 3. The secondary rectifier D16 is a dual Schottky
device and, because of the symmetrical duty ratio, only a
modest amount of capacitive filtering is necessary to
attenuate the high frequency output ripple. In this design a
paralleled pair of 4.7 mF, 100 Vdc film capacitors were used.
the NCS1002 CVCC controller. The specific sensing
circuitry is essentially identical to that used in
ON Semiconductor application note AND8470 for the
NCL30001 LED controller and will only be briefly
described here.
The output current is sensed by resistor R22 and the dc
output current level can be adjusted by changing R26. If
PWM dimming is used, the circuit of Q5, C22, R31 and R32
form a sample and hold circuit that prevents the current pulse
interruptions through current sense resistor R22 from
corrupting the dc current sense information presented to
pin 6 of U4B. This keeps the peak current output level
constant during PWM dimming.
The secondary winding of the half−bridge transformer,
The current and voltage sensing circuitry is based around
Current regulation is accomplished by section B of U4.
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of R28 and R29 and U4A. The maximum output voltage can
be adjusted by the value of R28 and is set to approximately
50 V in this application.
pulse width of the PFC MOSFET by pulling compensation
pin 8 low on the main controller U1. In this way the bulk
output voltage of the PFC is regulated so as to provide a
correct high voltage dc input to the resonant half−bridge
converter. The amplifier whose output is lowest will be
dominant, thus providing constant current, constant voltage
control with a smooth transition at the CVCC knee. To
minimize the Miller capacitance effects of optocoupler U3’s
photo transistor to the feedback loop, R15 and D13 have
been added to force extra current through the opto transistor
without loading pin 8 of U1.
resistor network R14, R18, and R19, this divider is set via
R19 such that this “inner” voltage loop is closed when the
bulk voltage reaches 550 Vdc so as to not prematurely
interfere with the secondary voltage loop of U4A. Note that
if the secondary voltage feedback loop were to fail, the inner
PFC voltage feedback loop would clamp the bulk voltage to
approximately 550 Vdc.
Output voltage sensing is achieved via the sense divider
Both amplifiers drive optocoupler U3 which controls the
Since the PFC also senses the bulk output voltage via