| 摘要 |
PURPOSE:To facilitate the cooperative protection together with a filter circuit in accordance with a load by providing a control circuit between either a switching circuit element for an active filter circuit or the output side of the active filter circuit and a switching element for a lighting circuit. CONSTITUTION:A control circuit 8 is disposed between either a switching element 2 for an active filter circuit 3 or the output of the active filter circuit 3 and switching circuits 6a, 6b. With this arrangement, an input for the circuit 3 can be obtained in accordance with a condition of the discharge lamp load, and accordingly, the cooperative protection with the circuit 3 can be facilitated. That is, the input voltage of the circuit and the current wave shape are controlled in phase so that a full-wave rectifying circuit 1 rectifies an a.c. voltage 9 through a filter circuit 10 in order to obtain a high power factor with no harmonic distortion. Further, the circuit 3 may obtain a high d.c. voltage higher than the a.c. voltage, which is then applied to a discharge lamp circuit 7 comprising a half-bridge circuit so as to alternately turn on and off the elements 6a, 6b, and accordingly, a discharge lamp 4 is turned on through a choke 5. |
