HF01B00/01/02/03/04

–OFF LINE HIGH VOLTAGE QUASI RESONANT REGULATOR

HF01B00/01/02/03/04 Rev. 1.2

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12

4/9/2013

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Leading Edge Blanking (LEB)

In normal operation, the primary peak current is

sensed by a shunt resistor between the Source

pin and Ground. The turn-off threshold of the

When the voltage drop of shunt resistor reaches

Vsense, the MOSFET turns off.

During start-up and over-load condition, the

primary peak current threshold is internally

3.3V to avoid excessive output power and lower

the voltage rating of the switch.

In order to avoid turning off the MOSFET by mis-

trigger spikes shortly after the switch turns on,

the IC implements a 320ns leading edge blanking.

During blanking time, any trigger signal on

source pin is blocked. Figure 11 shows the

primary current sense waveform and the leading

edge blanking.

320ns

Figure 11

—Leading Edge Blanking