| 摘要 |
PURPOSE:To reduce and adjust the light output of a discharge lamp by controlling the ratio of the on-periods of a pair of switching elements in an inverter circuit when the on-period of the switching element in a chopper circuit is decreased so as to reduce the light output of the discharge lamp. CONSTITUTION:A chopper circuit 2 has an inductance L which is stored with energy by the output current from a rectifying circuit B when a transistor Q2 is turned on and discharges the energy to a smoothing capacitor Co when it is turned off, an inverter circuit 1 has a pair of transistors Q1, Q2 turned on in turn, and a connecting capacitor C3 connected in series between both ends of one transistor Q1 end a load circuit including a discharge lamp 1a. When the on-period of the transistor Q2 in the chopper circuit 2 is decreased, the ratio of the on-periods of a pair of transistors Q1, Q2 in the inverter circuit 1 is controlled so as to reduce the light output of the discharge lamp 1a. The light output of the discharge lamp can be thereby reduced and adjusted. |
