13.8V 20A Stabilized regulator by 7912,2N3055 Schematic Diagrams Comments Off on 13.8V 20A Stabilized regulator by 7912,2N3055
This is circuit Power Supply regulator 13.8V 20A.
Use part Electronics IC 7912 and Transistor 2N3055 x 6.
It is High Current power supply and easy circuit.
The starting problem was to recycle some things: chassis, transfomer, heat sinks etc: what to do?
A power supply, of course !
This time I’ve stabilized the negative side using 6 cheap 2N3055 with collector directly mounted on the chassis.
My transformer was 220/19V;
you can calculate the power it can give by the core dimension, but I’ve preferred use a practical way:
I’ve used a 100 meter / 1,5 mm wire and measured its resistance; it was about 1,1 ohm; so I’ve connected it to the output of the transformer; after about 30 seconds the transformer was still cold; well, due to the Ohm’s law, the trasformer was able to supply at least 19 / 1,1 = 15-18 ampere: OK, it was good.
Rectifier bridge’s diode usually see a voltage of Vout x 2,828, so it’s better to use one with a PIV 3 or 4 time bigger than the output voltage (19×3=57V);
same words for the current: a 50Ampere bridge has been used.
At first I’ve used a 25A one and infact after few test it has broken.
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For a bridge rectifier you must use the following formula to calcule the amount of needed capacitance:
C= 1,8 x (I / VR)
where I is the max current and VR is the max ripple;
if a stabilizer follows the capacitors (as here), then you can use a value 40% lower than the calculated one; in my power supply I’ve used 2x 22000 microF / 40VL.
The working voltage of capacitor should be at least 40 % bigger than the output voltage.
I’ve used a LM7912.
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