The isolation device such as a pulse transformer (75) is coupled to the pulse generator for transferring the pulse signal.

The power supply converting unit comprises a pulse transformer (3) and a switch control circuit (2).

The pulse transformer, controlled by the pulse width modulator, in turn controls the switching of the H-bridge network, preferably to within 50 nanoseconds.

An isolation device such as pulse transformer or. small capacitors is coupled to the pulse signal generator for transferring the pulse signal through an isolation barrier of a transformer.

The impedance of said resistor (54) at a noise frequency is less than the circuit impedance of the pulse transformer (42) side.