Here is 12 volt power supply 20A , USE LM7912 and 2N3055 .
It easy circuit , Low cost. see detail more in image.
This power supply is the result of the use of components at hand (junk box). The core of the project is a number of 2N3055 transistors and a transformer with a 16 volt 18 amp secondary winding.
As it is constructed using the parts I had available at the time it may not be the most cost effective design if all parts are purchased new.
Rather than use a more conventional arrangement with a positive supply it was easier to use a negative supply and make use of a 7912 negative regulator as the voltage control. Then by using available NPN transistors to boost output, an output up to 20 amps can be obtained at 12 volts.
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