Electronics > Beginners

Discrete Regulated power supply

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GigaJoe:
silly ideas:  dif amp - darlington,   output from a zener going to another zener - that would be a vref;

mike_mike:
Hello,
Is there any way to add more than 2 power transistors in the attached schematic ?
I don't need more output current, just more power transistors in parallel. It is enough to add more transistors with emitter resistors in parallel or I need to make other modification ?
The maximum output current set by P3 will be 5A and maximum output voltage set by P4 will be 27-28V.

not1xor1:

--- Quote from: mike_mike on March 06, 2019, 06:42:14 pm ---Hello,
Is there any way to add more than 2 power transistors in the attached schematic ?
I don't need more output current, just more power transistors in parallel. It is enough to add more transistors with emitter resistors in parallel or I need to make other modification ?
The maximum output current set by P3 will be 5A and maximum output voltage set by P4 will be 27-28V.

--- End quote ---

yes, you can  :D
that PSU is already so bad that there is no chance you can make it worse  >:D

Cliff Matthews:
@not1xor1 - If he adds one or 2 more, shouldn't he at least upgrade the PNP driver to a TIP42c or similar?? (Ic = 6a)

IanMacdonald:
Yes, I would advise a TIP42C as a more substantial driver. You could also look at using 2N3773's instead of the 2N3055s. They are not much more expensive and are quite a bit higher rated.  Especially in voltage. (Which matters more than it might seem because the current handling of a transistor drops off quite rapidly as you approach its voltage rating - known as secondary breakdown.)

Other useful mod is that you can make P1 and P2 'bad wiper safe' by adding a high value resistor from the wiper to the minimum volts/current end. Say 220k. This will ensure that the supply goes to min output instead of max if the wiper goes open circuit.

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