High voltage power supply module operating in magnetic field

Abstract

The article describes a high voltage power supply module incorporating a ceramic transformer. The high voltage power supply module incorporates a ceramic transformer which utilizes piezoelectric effect to generate high voltage. The ceramic transformer is constructed from a ceramic bar and does not include any magnetic material. The module can work without a loss of efficiency under a magnetic field of 1.5 tesla. The module includes feedback to stabilize the high voltage output, supplying from 3000 V to 4000 V with a load of more than 10 MΩ at efficiency higher than 60 percent. A supply voltage of 5 V is high enough to provide the high voltage from 3000 V to 4000 V at a load of more than 10 MΩ. The module will be soon commercially available from a Japanese company. The module is provided with interface for a Neuron chip, a programming device processing a variety of input and output capabilities. The chip can also communicate with other Neuron chips over a twisted-pair cable, which allows establishing a high voltage control network consisting of a number of the modules which are interfaced by the Neuron chips individually. The functions of the module kept under the control of the chip are managed through the network. The chip turns on and off the module and sets the output high voltage. The chip detects the short circuit of the output high voltage and controls its recovery. The chip also monitors the output current. Thus the modules are monitored and controlled through the network. I. HIGH VOLTAGE POWER SUPPLY MODULE The high voltage power supply module includes feedback to stabilize the high voltage output, supplying from 3000 V to 4000 V with a load of more than 10 MΩ at efficiency higher than 60 percent under a magnetic field of 1.5 tesla [1]-[4]. A Japanese company1, trying to improve the performance and to reduce the size of the module, will soon makes a compact high voltage power supply module commercially available. The module incorporates a ceramic transformer. The ceramic transformer takes the place of the conventional magnetic transformer. The ceramic transformer utilizes piezoelectric effect to generate high voltage. The ceramic transformer is NF Corporation http://www.nfcorp.co.jp constructed from a ceramic bar and does not include any magnetic material. So the transformer is free of leakage of magnetic flux and can be operated efficiently under a magnetic field. The transformer is shaped symmetrically in the lengthwise direction and operated in the longitudinal vibration mode. The maximum power rating of the ceramic transformer is about 4 W. In a high voltage control network, each module is interfaced by a Neuron chip2. Neuron chips enable the high voltage power supply modules to network intelligently. Neuron chips have all the built-in communications and control functions to implement LonWorks3 nodes. These nodes may the be easily integrated into highly-reliable distributed intelligent control networks called LonWorks network. Most functions of the module is brought under the control of the Neuron chip. So function of the module kept under the control of the Neuron chip is managed through the network. The module is turned on and off through the network. The high voltage is set through the network. The output current is also monitored through the network. Short-circuiting the high voltage is detected by the Neuron chip and reported through the network. The Neuron chip is enabled to recover the high voltage from feedback breakdown, for example, caused by the short-circuiting. II. FEEDBACK The high voltage power supply is composed of divider resistors, an error amplifier, a voltage controlled oscillator (VCO), a driver circuit, the ceramic transformer and a Cockcroft-Walton (CW) circuit (Fig. 1). The VCO generates a driving frequency for a sinusoidal voltage wave which drives the ceramic transformer. The VCO supplies the driving frequency to the driver circuit where the sinusoidal voltage wave is generated synchronized with the driving frequency. The sinusoidal voltage wave is amplified in voltage by the transformer and then supplied to a Cockroft-Walton (CW) circuit where the sinusoidal wave is amplified further in voltage and rectified. A high voltage is produced at the output of the CW circuit. Neuron is a registered trademark of Echelon Corporation. LonWorks is a registered trademark of Echelon Corporation. R eg ul at or ESJA98 x6 x6 3nF 100nF