Here the bench variable power supply with voltage output range of 0-100V, output current 2A. The power supplies with low voltage and moderate current can be found in the most of engineering labs also available on the most of electronic stores, but the higher voltage supplies capable of several amperes of output current are difficult to find. We solved this difficulty in our lab by constructing the power supply supply shown in following diagram:
The circuit is used an IC (U1), an LT1270 high performance switching regulator constructed in a SEPIC topology, which permits the output to get altered higher or lower than the input voltage. The process is identical to that of a flyback converter, however the primary and secondary windings are coupled together by capacitor C1. This enables the primary and secondary windings to share current, minimizing copper reduction; furthermore, it removes the snubbing circuitry and losses found in flyback converters.
The converter is specially designed to work from an input of 40V to 60V, delivered by a line transformer, diode bridge and filter capacitor (not shown in this circuit design). Output voltage is linearly varied from 0V to 100V by using potentiometer R20.
The current is restricted by two independent loops. The first current limit loop is individual controlled over a range of 0A to 8A by setting potentiometer R21. This setting isn’t going to interact with alterations in output voltage. A second current limit loop restricts the highest available current as a function of voltage (parts R1-R5 and U2), minimizing component stress. Under any given operating condition, the lower of the two loops will take control. Optimum accessible output current is highest at low output voltage configurations (about 8A), and reduces to 2A at 100V output.