| 摘要 |
PURPOSE: To reduce the fluctuations in a lamp current and power by controlling a switch, so that the phase angle between bidirectional voltage and bidirectional current when return signal increases. CONSTITUTION: A power source circuit 10 has a circuit 18 for supplying DC base line voltage to a base line conductor 14, a resonance low circuit 121 having a plurality of resonance impedances and switched Q1, Q2. The circuit 12 has a first resonance impedance in series with a gas discharge lamp, and a second resonance impedance parallel to the discharge lamp, and the switches Q1, Q2 are connected in series between the base line conductor 14 and a ground conductor 16. Further, the power source circuit 10 has a serial half-bridge converting device for applying a bidirectional voltage between both ends of the circuit 12 for inducing a bidirectional current, and a circuit 44 for generating a return signal showing the current within a second resonance impedance. When the return signal is increased, the switches Q1, Q2 are controlled by return circuits 30, 32 so that the phase angle between the bidirectional voltage and the bidirectional current is reduced, whereby the fluctuation of current and power of the lamp is minimized. |
