LOW_VOLTAGE_POWER_CONTROLLER

Published:2009/6/23 3:19:00 Author:May | From:SeekIC

The circuit has a duty-cycle generator that will produce an output varytng from fully off to fully on and pulses of any duty cycle in between the two extremes.This method of operation is called PWM (pulse zuidth moduhtion) The circuit can be fed fromany dc supply source of between 10 to 15 V Half of an LM556 dual oscillator／timer and U2 a(1/4 of an LM339 quad comparator) combine to form a voltage to-pulse-width converter The first half of thedual os dilator/timer(U1-a) is configured as an astable oscillator，generating a continuously oscillating ramp voltage Op amp U2-a compares the voltage at its noninverting input (pin 5)—which is connected to pins 2 and 6 of U1-a—to the voltage at its inverting input(pin 4) The op amp will producea low output f R1’s wiper voltage lb higher than the instantaneous voltage that is present at pins 2 and 6 of U1-a，The output of U2-a at pin 2 will have an on/off ratio that is proportional to the voltageat R1＇s wiper.The output of U2-a is fed to U1-b，which is used to buffer the signal，The low－impedance，pulsedoutput of U1-b at pin 9 is fed to the gate of MOSFET Q1，driving it on or off The circuit also has apower-input detector，built around U2-band and LED1. If the input power is OK，LED1 will shut off.Diode D1 is used to Suppress the reverse voltage spikes that are generated by inductive loads during turn off；without that diode，the MOSFET might be destroyed．If the circuit will not be usedto drive inductive loads(motors)，D1 can be eliminated.



Reprinted Url Of This Article:
http://www.seekic.com/circuit_diagram/Control_Circuit/LOW_VOLTAGE_POWER_CONTROLLER.html

Print this Page | Comments | Reading(3)