PROBLEM: To generate a self-oscillation in a stable manner and at a low cost in a self-oscillating radio frequency oscillation circuit for high-power applications used for plasma generation in an ICP emission spectrometer or for other purposes.
SOLUTION: A secondary winding 38 of a starting transformer is arranged in an LC resonance circuit 30 including an induction coil 9, capacitor 36 and other elements. A starter 6, e.g. a Clapp oscillator circuit, is connected to a primary winding 5 magnetically coupled with the winding 38. A radio-frequency current is induced in the LC resonance circuit 30 through the primary and secondary windings 5 and 38 by energizing the starter 6 for a certain period of time in a starting phase. As a result, electric current flows through the secondary windings 11, 14, 17 and 20 in a full-bridge drive circuit 10 which are magnetically coupled with primary windings 32, 33, 34 and 35, respectively, whereby voltage is developed between the gate and source of MOSFETs 13, 16, 19 and 22, causing these MOSFETs 13, 16, 19 and 22 to begin an ON/OFF operation, whereby the self-oscillation is started.