A frequency generator for generating a working frequency for a transmission signal of a rail contact of an axle counter includes a series resonant circuit having a transmitter coil unit of the rail contact and a capacitor. The frequency generator has an inverter, the output of which is connected to the capacitor. The inverter is configured to generate an oscillating voltage and to feed the generated oscillating voltage to the transmitter coil unit of the rail contact via the capacitor. A current transformer synchronizes the output voltage of the inverter to the current in the series resonant circuit. A start-up circuit electrically connected to the inverter is configured to trigger the inverter and to be electrically connected to an input power supply. The frequency generator is a robust and effective circuit for generation of magnetic fields where manufacturing effort and expensive components can be reduced.

Disclosed is a resonant type high frequency power supply device provided with a power element that performs a switching operation, the power supply device including a high frequency pulse drive circuit 1 that transmits a pulse-shaped voltage signal having a high frequency exceeding 2 MHz to the power element to drive the power element, wherein a voltage signal from the high frequency pulse drive circuit 1 is subjected to partial resonance by an impedance of a signal line of the voltage signal and a parasitic capacitance of the power element.

A photoionization detector sensor equipped with a temperature compensating and output adjustable ultraviolet lamp driver for supplying an alternating current signal to the ultraviolet lamp effective to light the ultraviolet lamp with direct current supplied from both a first variable voltage supply circuit and a second temperature sensitive fixed voltage supply circuit, and method of standardizing output of the photoionization detector sensor by adjusting the voltage supplied to the driver by the first variable voltage supply circuit so that future reported values will more closely approximate actual values.

A high-frequency power supply apparatus for supplying high-frequency power to a load the impedance of which greatly fluctuates is provided, wherein a stable high-frequency current is always maintained without having overcurrent or overvoltage generated in a drive circuit thereof. In the high-frequency power supply apparatus, a constant-current conversion circuit is connected between an LCR series resonant circuit and a half-bridge drive circuit, high-frequency current of the LCR series resonant circuit is controlled by the voltage of the half-bridge drive circuit, and a constant-current function is applied to impedance variation of the load. Due to the constant-current conversion circuit, the gate of a MOSFET of the half-bridge drive circuit is driven with a parallel capacitor using a transformer inserted in the LCR series resonant circuit, and the phases of the high-frequency current of the LCR series resonant circuit and the output of the half-bridge drive circuit are maintained to be constant.

An inverter circuit comprises: a primary-side circuit including a plurality of self-excited oscillator circuits connected to a DC power supply; and a secondary-side circuit for outputting the multi-phase AC powers in accordance with the oscillations of the self-excited oscillator circuits. Each of the self-excited oscillator circuits includes power transmission coils, a resonant capacitor, a pair of switching elements, a drive coil, and a phase-shift filter. The respective control electrodes of the pair of switching elements are applied with voltages from the drive coil of another one of the self-excited oscillator circuits. The phase of the voltage applied to each of the electrodes of the pair of switching elements is shifted in association with the action of at least the phase-shift filter, with respect to each of the self-excited oscillator circuits, by a phase-shift amount according to the number of phases of output power.