Pulse Width Modulation Circuit of NE555

Published:2011/7/17 10:22:00 Author:Michel | Keyword: Pulse Width, Modulation Circuit | From:SeekIC

The above picture is pulse width modulation circuit composed of NE555.This circuit needs push-pull control pulse to generate switch power supply.NE555(1) is 40KFZ oscillator and its output triggers the trigger composed of NE555(2) monomultivibrator and gate circuits G1 and G2,which makes its oscillation frequency decline to 20kHZ and output two pulse signals via G3 and G4 push-pull.When control voltage is in lowest condition,NE555(1) oscillates on 40kHZ,NE555(2) pulse width is in widest situation.At this time,the dutyfactoris biggest,NE555(2) pulse becomes narrow as the control voltage increases.And if NE555(2) pulse width is in its narrowest condition,VT1 stops and NE555(1) oscillation frequency declines and the dutyfactor becomes less.If the control voltage is close to power source voltage, the NE555 (1) stop oscillatiing and the dutyfactor is zero.



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