HF01B00/01/02/03/04–OFF LINE HIGH VOLTAGE QUASI RESONANT REGULATOR
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
MOSFET is set by FB voltage, Vsense=VFB/3.3.
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
limited to 1V even if VFB voltage is larger than
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
HF01B00/01/02/03/04 Rev. 1.2
4/9/2013 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
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