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.
TRANSFORMER
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

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.

CAPACITOR FILTER

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.

STABILIZER IC
I’ve used a LM7912.
Read More Source:http://www.qsl.net/iz7ath/web/02_brew/20_ps7912/index.htm
thank you.

This entry was posted on Monday, October 1st, 2007 at 10:49 pm and is filed under high current power supply, Power supply.

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