# Phase Controlled High Current Variable Power Supply

Discussion in 'General Electronics Chat' started by surfline, Dec 2, 2009.

1. ### surfline Thread Starter Active Member

Aug 12, 2009
36
0
Our current project is to create a variable power supply from 2-30V that can handle up to 15 amps of current. We decided against using a voltage regulator in which the input is 30 Volts (From transformer & Diode bridge) and the output would either stay at 30 volts or drop to the desired voltage through the LM338 voltage regulator. We decided against this because of the excessive power that would be dissipated through that regulator going from 30 to potentially 2 volts at 15 amps of current.

Our alternative method of creating this power supply was to phase control the 110V, 60Hz input, through the use of Triac's, Diac's, and POT's. Essentially we are using a light dimmer circuit in an attempt to reduce the average voltage and power dissipation. We would then send our chopped up AC signal into the transformer -> diode bridge -> smoothing capacitors. Our goal was to be able to control the output voltage through the light dimmer circuit, specifically through the variable resistor (by controlling the average voltage of the AC signal).

The major problem we are having is trying to simulate this through circuit through SPICE programs. We have tried Pspice, hSpice, LTSpice, but our simulation's start getting convergence errors, time step too small errors, and have funky results.

The light dimmer circuit simulated pretty well, however when we connect the transformer as the load instead of a resistor, it doesn't work well. It only phase controls for the first cycle.

Is the concept wrong here or is it just that the software can't handle it? How would you simulate this correctly?

Blue Sin wave = V1 (input)
Red line = voltage at primary winding of transformer
Blue line = voltage at secondary winding of transformer

Thanks.

Surfline

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2. ### masa6614 Active Member

Nov 9, 2008
48
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I dont know much about your concept, but if you're using Pspice, i've found this helpful for convergence problems. Goodluck!

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