| 摘要 |
PROBLEM TO BE SOLVED: To achieve an efficient protection against a transient phenomenon and a pulse voltage using a relatively small number of relatively inexpensive components by an arrangement wherein a branch circuit includes a series circuit of a varistor and a break over diode BOD. SOLUTION: When a switching element S is conducted to apply an AC voltage between input terminals K1 and K2, the AC voltage is rectified through a diode bridge D. When a capacitor C is charged, a DC voltage is induced across the capacitor C during a steady operation thereof. When the switching element S is switched to a nonconducting state, a ballast circuit B is switched off to generate a pulse voltage through a coil L and the capacitor C and the pulse voltage is applied to the output end of the diode bridge D. When the pulse voltage has a large amplitude, a series circuit of a varistor V and a BOD DD is conducted. Consequently, the pulse voltage is damped significantly and occurrence of a transient phenomenon in the voltage supply line can be suppressed significantly. |
