PURPOSE: To make a transformer light in weight and small in size at a low cost by a construction wherein an amplification oscillation circuit generating a peak pulse is connected to a primary coil and a secondary coil formed of a very thin wire and wound in a larger number and having a smaller diameter than the one of the primary coil is used as the output side.

CONSTITUTION: When a current flows to a base of a transistor(TR) 3, a low current of high voltage flows to a collector, and the current flows through the base decreases. Accordingly, the collector current of the TR 3 becomes 0. At this time, a peak pulse current flows through the secondary coil of a transformer 7. When the collector current becomes 0, a current flows to the base of the TR 3, peak pulse is generated and oscillation of low current and high voltage takes place. Since the peak pulse rises sharply and has an acute angl, however, a peak voltage is instantaneous and the primary coil is not burnt. Due to this peak pulse, an output is obtained in the secondary coil by a mutual induction. At this time, too, the peak voltage is instantaneous and the secondary coil is not burnt.