FP133

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Rev. 0.9

9/10

RS

FP133

LOAD

Is

RG1

RG2

RL

REF

CA

FPO

CSO

GND

IF

R3

FP384x

1

2

Io

R1

R2

Adaptor secondary Voltage Feedback / Over Loading Protection circuit

The above circuit is a simple application for AC / DC adaptor over loading protection (OCP)

function with output voltage feedback.

to equation (2). Once the internal shutdown comparator’s inverting input, which is connected to CSO

FP384x PWM IC will change the NMOS drive terminal to a minimum duty cycle current limitation for

secondary side over current protection. The primary side auxiliary voltage can no longer maintain the

FP384x power supply. The FP384x will be shutdown until AC line start-up voltage restart the PWM IC.

The FP133 voltage shunt regulator responses the output voltage change with R1 and R2. The

feedback current will flow from photo-coupler to FP133 CA pin (pin4) and generates the feedback

voltage signal to PWM IC FP384x.