is this battery backup with charging capability ok

[nikhil arora]

The ckt which i have shown is for giving battery backup to a system which should work continuosly, system req 5V and i have used 12 v battery , now when the light goes, the battery is connected to ckt via diode and when the battery is near to danger level of discharge it should cuttoff itself from the load.
and when the ac power is regain then the battery should charge but little faster,


100 ohm resistor should be changed to 47ohm

 

[Roff]

I don't understand how it's supposed to work, but maybe if you fix Q4 and/or D4, it will make more sense. Current cannot flow through them as drawn. Is Q4 supposed to be an NPN?

 

[nikhil arora]

q3 and q4 makes circuit to switch off the current when battery voltage falls to critical value med power transitor Q4 is switch on and off by q3.

ur suggestions are very much welcome.

 

[Roff]

q3 and q4 makes circuit to switch off the current when battery voltage falls to critical value med power transitor Q4 is switch on and off by q3.

ur suggestions are very much welcome.

You didn't answer my question: Is Q4 supposed to be an NPN?

 

[nikhil arora]

sorry sir q4 is is pnp and it is connected in wrong way so plz invert it.

 

[nikhil arora]

THIS IS THE NEW CKT WHICH I AM POSTING. NOW THIS WON'T CONFUSE U MUCH.

HERE Q1 IS USED FOR SWITCHING BETWEEN SLOW AND FAST CHARGE.
R2 CAN BE CHANGED AS REQUIRED FOR FAST CHARGING.

 

[Roff]

THIS IS THE NEW CKT WHICH I AM POSTING. NOW THIS WON'T CONFUSE U MUCH.

HERE Q1 IS USED FOR SWITCHING BETWEEN SLOW AND FAST CHARGE.
R2 CAN BE CHANGED AS REQUIRED FOR FAST CHARGING.

You're correct. That is much easier to understand.
It looks good to me.

 

[nikhil arora]

now i am through with power supply design
with the help of this forum,
thanks for help.

 

[Roff]

now i am through with power supply design
with the help of this forum,
thanks for help.

I hope this is not for a commercial product. The temperature coefficient of your 12V charger regulator is about 35mV/deg C. This is probably OK in a home environment, where the temperature is controlled, but from 0 to 40 degrees, the voltage will change by about -1.4 volts. I would think this is too big a range for a battery maintenance voltage.

 

[nikhil arora]

Thank you for pointing out this problem in the above ckt.
At present the working condition of this will be at home and offices where temperature will not change much. so we can go ahead.

But when I will upgrade my product i surely add this.
i will remember ur suggestion
thank you once again
electronics god.