A photomultiplier high-voltage power supply incorporating a ceramic transformer driven by frequency modulation

This paper describes the circuit and operation of a photomultiplier high-voltage power supply incorporating a ceramic transformer instead of a conventional magnetic one. The ceramic transformer, being constructed from a ceramic bar, utilizes the piezoelectric effect to generate high voltage. As no magnetic material is present, no leakage of magnetic flux occurs such that the power supply can be operated under a strong magnetic field. The transformer shows a sharp resonance, after which voltage amplification is dependent on frequency. Transformer output is stabilized by feedback utilizing frequency dependence, i.e., after rectification, the output high voltage is fed back to a voltage-controlled oscillator that adjusts the oscillation frequency according to the output voltage of an error amplifier that compares the output high voltage with a reference voltage. This photomultiplier high-voltage power supply provides high voltage from 1500 to 2500 V at a 20-M/spl Omega/; load, where the load is a breeder of the photomultiplier. The magnitude of voltage ripples is at a prescribed level when the load is 20 M/spl Omega/. Ripple magnitude is proportional to load current. Voltage ripples limit the load current to the photomultiplier.