Regulated power supply circuit

A high voltage regulated DC power supply circuit comprising a full wave rectification stage for rectifying an input voltage of alternating current and a regulating stage capable of regulating an output voltage from the rectification stage in excess of 1 kV, the regulating stage having a primary voltage regulating circuit and a secondary voltage regulating circuit, the primary voltage regulating circuit having an open-loop configuration including a MOSFET-type device connected in a source-follower configuration, a primary voltage reference element for limiting a gate reference voltage to a gate of the MOSFET-type device to a maximum gate reference voltage, and a plurality of current limiting elements connected in series with the primary voltage reference element for limiting bias current to the gate and for sharing major portions of the output voltage from the rectification stage, and the primary voltage regulating circuit being directly cascaded to the secondary voltage regulating circuit in a voltage sharing configuration without a feedback or clamping circuit at an output from the MOSFET-type device, the MOSFET-type device arranged to operate in two modes, namely a first saturated on mode, in which the output voltage from the rectification stage is less than the maximum gate reference voltage, and the output from the MOSFET-type device follows the output voltage from the rectification stage, and a second on mode, in which the output voltage from the rectification stage exceeds the maximum gate reference voltage determined by the primary voltage reference element, and the output from the MOSFET-type device is held at approximately the maximum gate reference voltage provided by the primary voltage reference element, the power supply circuit being capable of handling an input voltage which exceeds a maximum-voltage rating of the MOSFET-type device.