hi friends,
I want a dc constant current limiting circuit without so much heating any components for my lead acid battery charger. have any idea to solve my problem?
please help!
Thanks for reply
yes i know pwm tecnique, but i have not any practical circuit diagrams,
I work with some pwm circuit but i can't manage it. current controling is easy but keep it constant with varying load is dificult. feed back voltage manage from shunt is another problem. so i looking for practical circuit diagrams. I know fundamental low but that is important for beginners!
Thanks for reply
yes i know pwm tecnique, but i have not any practical circuit diagrams,
I work with some pwm circuit but i can't manage it. current controling is easy but keep it constant with varying load is dificult. feed back voltage manage from shunt is another problem. so i looking for practical circuit diagrams. I know fundamental low but that is important for beginners!
That is why a true current source has an effing big inductor any change in load (as long as teh resultant voltage doesn't get too close to the source voltage rail) is fine.
A simple chopper cct is all that is needed with a suitable current-sense in the coil free-wheel path
hero999
thanks for circuit diagrams.but I don't understand how it works as a constant current mode? I think in put voltage must be ac(~) ok i will test it in my lab.
I told u my own plan,at first i make a voltage controled pwm circuit and invert this pwm signal to drive npn or n chanel power mosfet in switch mode in negetive side and place a very low velue shunt resister for low heat desipation and amplify shunt voltage from respect to ground and feed this voltage as a pwm control voltage. is it ok?or not ok?
Tr1 carries most of the current to RL, normally R1 biases Tr1 on.
R2 is a current sensing resistor when the voltage across it exceeds about 0.6V it turns on D1 which diverts Tr1's base current through RL causing it to turn off.
D1 will remain on until the power supply is interrupted.
C1 and R3 provide a short time delay to prevent any capacitance in RL from tripping it.
Again thanks for promt reply, now i understand your posted circuit. This is fine
for electronic fuse if it modify to auto reset then it will be meet my purpose.
because when i drow over current tr1 will cut off by scr and if auto reset again and again it will act as a constant current source but tr1 must be full on in every time resulting nominal heat will produce by tr1. My aim is how can
minimise power desipation as low as posible. whatever out put current be pulsed it will no problem for charging 12v lead acid battery.
My reson is charging a lead acid battery in near heat free constant current mode. linear constant current circuit prouduce much more heat in small box it is very unlike for me.
No it isn't, it's a resetable electronic fuse, you just disconnect and reconnect the load and it resets - D1 doesn't remain latched when the current's interrupted.
No it isn't, it's a resetable electronic fuse, you just disconnect and reconnect the load and it resets - D1 doesn't remain latched when the current's interrupted.