lal@uni-tel.com

The design of this high voltage transformerless source is given in figure (please contact me for the circuit diagram lal@uni-tel.com).

1. Uses a single PP3 rechargeable battery or a nickel cadmium battery pack to generate more than 100V pulses.
2. Avoids pulse transformers mainly because of a) Cumbersome calculations involved in the design of an efficient one, b) Poor current transfer and c) High output resistance.
3. Simple switching design.
4. Non - inverter type of design avoiding a) High standby current b) difficulty in rectifying the output to a constant voltage,
5. Non switch - mode type which generally have a a) High standby power consumption b) Limited output voltage generally to 50V.
6. Low current drain - economy of battery operation.
7. Low output impedance.

The working principle of the circuit is as follows :- A square wave of amplitude nearly to the supply rails is applied to a voltage multiplier consisting of a capacitor diode bank. A multivibrator (CD 4047B) generating nearly 200kHz was used for this purpose and is made to drive a push-pull combination of P and N channel MOSFET’S. 16 multiplier stages were used to generate approx. 130V. These stages can be reduced or increased to get the required output voltage, with Vout = n x Vin, where n is the number of stages and Vin here = 9V.

In order to regulate and control the output, a comparator was used which gives a low when the reference value was less than a predetermined level. It therefore switches ON and OFF the multivibrator depending on the setting of the potentiometer. Therefore the high voltage generated by the circuit could be set at any voltage between 1.5-130V. Capacitors in the multiplier circuits are polystyrene types, which intrinsically have low leakage. The comparator IC2 maybe replaced by a CMOS version (in our prototype we checked with an Intersil ICL 7611 and the quiescent current was only 30m A) for low current drain from the 9V battery. Even though the voltages generated by this converter is limited to <150V, it is advisable to take proper precautions while handling the output.

 NOTES

1. WE the authors are aware that many improvements and refinements can be made, but the idea is to keep it simple as possible, and executed by anyone who can make a circuit board and has the patience !!!!.

Mains-powered and also equipment like the one described above contains high AC voltages. These can be potentially lethal. If you do not know how to safely handle the inside of equipment containing high voltages, please do not attempt to open the equipment. Before carrying out any work inside equipment containing high Voltages, ensure that you disconnect the battery powering it AND/OR disconnect the Unit from the Mains. Opening any kind of electronic equipment and modifying it will almost always invalidate your warranty. There is also a likelihood that workshops will refuse to repair custom modified equipment or that they will charge significantly more. (2) The information included herein is provided as-is, with no warranties expressed or implied. No resposibility on the part of the author is assumed for the technical accuracy of the information given herein or the use or mis-use of said information.

 The information on this site is Copyright © 1998 of Dr.LAL. You may link to these pages or print them out for your own personal use, but no parts of these pages can be reproduced, sold, or transmitted in any form without my explicit written permission. By copying or paraphrasing the intellectual property on this page, you're automatically signing a binding contract and agreeing to be billed $1000 payable immediately. © Dr LAL's Homepage (CKT.DESIGN) 1998.

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