Hi,
I am having some problems with the circuit posted below.
The circuit is a basic regulator, that works in the following way:
The LED provides a 1.8v reference at the base of the BD140 and the resulting 1.1v at its emitter causes 2.34ma
to flow through its 470 Ohm emitter resistor and through the 3.3k resistor at its collector. This gives 7.7v at the BDX37's base and so 7v at it's emitter.
This works fine for voltages up to 36v, but the problem is, with some 48v power sources (batteries OR power supplies), I get surges through the circuit,
which causes overvoltage to the 100uF 25v capacitor which then blows.
I've tried running bigger capacitors at the front end, but no matter what I do, occasionally when powered from 48v the circuit will allow a much higher
voltage through which blows up all the stuff that is expecting no more than +7v !
Can anyone suggest anything else I can try to stop parts blowing up when 48v is applied?
It doesn't happen all the time, but occasionally it does, which makes the circuit unstable.
Thanks for any and all input!
I am having some problems with the circuit posted below.
The circuit is a basic regulator, that works in the following way:
The LED provides a 1.8v reference at the base of the BD140 and the resulting 1.1v at its emitter causes 2.34ma
to flow through its 470 Ohm emitter resistor and through the 3.3k resistor at its collector. This gives 7.7v at the BDX37's base and so 7v at it's emitter.
This works fine for voltages up to 36v, but the problem is, with some 48v power sources (batteries OR power supplies), I get surges through the circuit,
which causes overvoltage to the 100uF 25v capacitor which then blows.
I've tried running bigger capacitors at the front end, but no matter what I do, occasionally when powered from 48v the circuit will allow a much higher
voltage through which blows up all the stuff that is expecting no more than +7v !
Can anyone suggest anything else I can try to stop parts blowing up when 48v is applied?
It doesn't happen all the time, but occasionally it does, which makes the circuit unstable.
Thanks for any and all input!