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|Using Parallel Multipliers for 100kV Downhole Neutron Tube Power Supplies|
|Keywords: high voltage power supplies, voltage multiplier circuits, downhole neutron tube|
|Operating 100kV downhole neutron tube power supplies at temperatures above 150 ºC yield low operating efficiency due to excessive diode leakage in the series Cockroft - Walton multipliers typically used. Such circuits are usually limited to less than twelve stages due to N3 voltage regulation effects resulting in immoderate potentials across the switching rectifiers. This paper discusses the merits of using parallel multipliers with 30 stages or more to achieve higher conversion efficiencies at elevated temperatures in tools with 1.3 inch (32mm) diameters. By minimizing the per-stage voltage, definite improvements are realized due to reductions in reverse current leakage per device. Efficiencies of up to 50% may be achieved at 175 ºC operating temperature by this technique. In addition, ripple voltages present on the output are not a function of the number of multiplying stages in parallel designs.|
|Gary Hanington, Chief Scientist
American High Voltage