NCP1203D60R2G (IC901): PWM control, high-voltage startup current. The circuit unit
has functions such as over-current protection, over-voltage protection, output
short-circuit protection and etc. The function of each pin and the inside circuit diagram
are as follows:
Pin
No.
Pin
Name
Function Pin Description
1 Adj
Adjust the skipping
peak current
This pin lets you adjust the level at which the cycle
skipping process takes place. Shorting this pin to ground,
permanently disables the skip cycle feature.
2 FB
Sets the peak
current setpoint
By connecting an optocoupler to this pin, the peak current
setpoint is adjusted accordingly to the output power
demand. Skip cycle occurs when FB falls below Vpin1.
3 CS Current sense input
This pin senses the primary current and routes it to the
internal comparator via an L.E.B.
4 GND The IC ground −
5 Drv Driving pulses The driver’s output to an external MOSFET.
6 VCC Supplies the IC
This pin is connected to an external bulk capacitor of
typically 22 F.
7 NC −
This unconnected pin ensures adequate creepage
distance.
8 HV
Ensure a clean and
lossless startup
sequence
Connected to the high−voltage rail, this pin injects a
constant current into the VCC capacitor during the startup
sequence.
ViewSonic Corporation VA503b-1_ VA503m-1
24
Confidential - Do Not Copy
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