Patent ID: 7710086
Filing Date: 2010-05-04
Classification: H02M,Y02B,Y10S

Abstract:
1. A high voltage power supply comprising: DC-DC converter having a low voltage input to which an input current is applied and a high voltage output at which an output current and an output voltage are developed; a first voltage controlled resistor comprising an MOS photo relay having a photo diode to which said input voltage is applied and a pair of series connected MOS switches defining said first voltage controlled resistor, said photo diode emitting light in response to said input voltage wherein variation in said input voltage causes a corresponding variation in said light, said switches being operative to develop a current in said switches proportionally in response to said light such that said current in said switches determines a resistance of said first voltage controlled resistor, said first voltage controlled resistor being electrically coupled to said high voltage output in parallel with said DC-DC converter and having a control input wherein a resistance of said first voltage controlled resistor is determined by an input voltage applied to said control input of said first voltage controlled resistor; a feedback circuit operatively connected between said high voltage output of said DC-DC converter and said control input of said first voltage controlled resistor, said feedback circuit being responsive to each of a reference voltage and a feedback signal proportional to said output voltage and operative to develop said input voltage which varies as a function of variation in said feedback signal, said first voltage controlled resistor in response to variation of said input voltage being operative to vary said resistance such that variation of said resistance is in opposition to a variation of said output voltage to maintain said output voltage substantially constant; a second voltage controlled resistor electrically coupled to said high voltage output of said DC-DC converter wherein said second voltage controlled resistor is electrically connected in series between said high voltage output and a load, said second voltage controlled resistor having a control input wherein a resistance of said second voltage controlled resistor is determined by a float control voltage applied to said control input of said second voltage controlled resistor; and a float control circuit operative to develop said float control voltage in response to said reference voltage and a bias voltage.