| 摘要 |
In a preionization discharge circuit 10, when a switch SW14 is turned on, an electric current i10 from a constant current source 13 flows through a loop of a coil L12, en electrode 11A and the switch SW14. When it is assumed that an inductance of the coil L12 is L (H) and the current i10 flowing through the coil L12 is I (A), energy EL of (1/2).L.I 2 is accumulated in the coil 12. Meanwhile, in a preionization discharge control section 40, a preionization discharge timing signal (namely, a corona emission timing signal) Ydt is output to the switch SW14 after lapse of a time ty (=Tds-tyd) after a pulse oscillation synchronizing signal TRL is received so that preionization discharge is caused earlier by a preset time tyd than the preionization discharge timing signal Ydt. When the switch SW14 is switched from on to off according to the corona emission timing signal Ydt, the energy EL accumulated in the coil L12 is abruptly supplied to the electrode 11A of the preionization electrode 11. Then, an electric field is produced between the electrode 11A and an electrode plate 11C and, when the electric field of the preionization electrode 11 rises to a predetermined preionization start electric field, a corona discharge is produced in a tube 11B as a dielectric of the preionization electrode 11 to flow an electric current i11, and a main discharge gap 3 is preionized before the main discharge is caused by main discharge electrodes 1 and 2.
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