1.2 - 32 volt power supply

Discussion in 'The Projects Forum' started by walcen, Sep 18, 2011.

  1. walcen

    Thread Starter New Member

    Aug 6, 2009

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    Very interesting reading indeed.

    I too am preparing to build a bench power supply such as mentioned above using a rewound MOT to cater for heavy load, and I, as a layman!!! also was under the assumption that the lm338 could simply adjust voltage from 1.2 to 32 volts with a maximum supply voltage, Doh.

    I must farther educate myself.

    Using multiple regulators would increase the load capacity but if the load requirements are say 5 amp and one used three or more regulators, would they share the heat dissipation?

    And if one were to wind multi taps on a transformer to apply varying input voltages to the rectifier via a rotary switch, and then used a pot to vary the voltage on the regulator, would this be an acceptable method?

    And what would be the maximum allowable voltage between taps for the regulator to operate efficiently between 1.2 to 32 volts.

    So many questions, so little time :(.

    Kindest regards to all

  2. k7elp60

    AAC Fanatic!

    Nov 4, 2008
    I understand what you say and the problems you face with such a powersupply. I wanted to build one similar to your idea. I used a LM338K on a large heatsink and I discovered that at times it would shut down when I thought it sould not. I finally realized that even thou I thought everything was okey, the internal circuitry of the LM338K sensed a overload condition. I went back to a LM723 and a darlington series pass transistor 2N6284 with external current limit resistors. I decided I didnot need to go below 6V so I have 2 ranges. 6-12V@ 8A and 12-28V@ 4A. I used the transformer in FW center tapped and FW bridge for the two ranges.
  3. DickCappels


    Aug 21, 2008
    I have used such a bench power supply (LM317 + LM337) to obtain the range of ±1.25 to approx 25 VDC since those ICs became available. They work fine as long as I don't draw too much current. In the rare case of overloading, the thermal protection and sometimes the current limit on the chips took over. Most of my circuits don't take much power.