Dr. Sidra Fareed

It is a high voltage DC Power supply which is mostly used for the testing of insulation of high voltage cables. The circuit design is based upon a NAND gate based analog circuit, Flyback converter and Cockcroft Walton voltage multiplier. First of all, 220V AC supply from WAPDA is stepped down by a center tapped AC transformer which gives positive and negative 12V RMS voltage. 12V and 24V AC signals are applied to NAND gate based analog circuit which generates a variable frequency PWM signal. This signal is 5V PWM signal with an offset of 24V. This signal is fed to Flyback converter which gives a variable 5kV DC signal. Flyback output decreases with the decrease in frequency of PWM signal and increases with the increase in frequency of PWM signal. So, by controlling the frequency of PWM signal, output voltage is being controlled. The output of Flyback converter is fed to Cockcroft multiplier which gives a variable 50 kV DC signals finally at the output. The output voltage can be measured by a high voltage Electrostatic voltmeter. The output voltage can also be measured using a potential divider circuit which has been used as measuring circuit for our project. The whole circuit has been simulated in MATLAB and desired results have been obtained. Following figure shows the snapshot of circuit design on MATLAB.

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