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Digitally controller PSU


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To have a 35VDC regulated output, the circuit needs a 30VAC transformer. 30 x 1.414= 42.4V peak, minus 2V for the rectifier bridge and minus 1V of ripple in the filter capacitor = 39.4V unregulated.

If you power a 5VDC/4A regulator from unregulated 39.4V then the heat in the series pass transistor is (39.4V - 5V) x 4A= 138W. Two power transistors on a huge heatsink is needed.

If you have an adjustable output voltage supply going down to 0V (maybe when shorted) then its series pass transistor will heat with 39.4V x 3A= 118.2W and will need two power transistors on a huge heatsink.
The negative adustable output voltage supply will need the same.

If you have a 24VDC/5A supply then its series pass transistor will heat with (39.4V - 24V) x 5A= 77W and will need one or two power transistors on a huge heatsink.

The above totals 15A. The transformer should be rated at the peak voltage of 42.4V x 15A= 636VA.

If all the power is used at the outputs of this supply then you can heat your entire neighbourhood with it! It will be enormous! It will be expensive!

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