Centralion 400VA - Active Clamp Circuit Function; Output Voltage Pull-Down; Clamp Circuit Control

G. Active Clamp
The purpose of Clamp circuitry (Figure S-5) is to pull down the output voltage while two
sets of Inverter MOSET are OFF. The Clamp circuitry is active during the period of zero Volt.
of square wave at battery mode.
The Q22 is activated while the CLAMP-OFF signal (from pin 27 of CPU) goes to HI .
If either one of the two MOSFET sets turn on (Q20/Q24 or Q023/Q25), the CLAMP-OFF
signals will remain HI.
When UPS at line mode, the CLAMP-OFF signal remains HI. This turns on U07 to turn
off Q22. At this time the Clamp circuitry is not active. When the CLAMP-OFF is LOW, U07
turns OFF and Q22 turns on. This pulls down output voltage to approximately zero at battery
mode. Figure W-8 illustrates the relationship of the output waveforms and the CLAMP-OFF
signal.
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