Control of constant voltage and constant current circuit composed of current amplifier

Published:2011/7/18 2:51:00 Author:Fiona | Keyword: current amplifier, constant voltage and constant current | From:SeekIC

Constantvoltage circuit working principle:U2,ICIB,R6,R7,VD4,R10 and U1 form the voltage control loop. U2 (TL431) is a precision voltage regulator, cathode K and the control electrode R directly shorts circuit to form the precision 2.5V reference voltage. R4 is U2's current-limiting resistor.2.5V reference voltage is sent to the inverting input ICIB (6 pin) by the resistor R5; and non-inverting input (5 pin) is set by R6, R7's partial pressure ratio.If the output voltage rises,the UR7's voltage rises too,this voltage compares to the negative terminal 2.5V reference voltage,7-pin outputs error signal,and then becomes into a current signal through the VD4 and RIO,inflows the optocoupler's LED, and then through the feedback control and network control to make the primary side PWM output duty cycle,so that the output voltage is in the constant state.



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