| 摘要 |
PURPOSE:To operate an electric discharge lamp stably when light dimming is deepened in the case where a load is the electric discharge lamp by adjusting electric power to be supplied to the load without changing frequency. CONSTITUTION:Switching elements S1, S2 and S3, S4 are connected in series to DC electric power supply, and an inductor L1, a capacitor C2 and a load Z are connected between connecting points of the switching elements S1, S2 and S3, S4. The on-and-off timing of the switching elements S3 and S4 is varied to the on-and-off timing of the switching elements S1 and S2 within range up to a phase dislocated by 180 degrees from the phase. The simultaneous on-time of the switching elements S1, S4 and S2, S3 in diagonal positions is changed, and electric power to be supplied to the load Z is adjusted without changing switching frequencies. The switching frequencies of the switching elements S1 and S4 are made to coincide with each other, and the switching frequencies of the S2 and S3 are made different from each other, and positive and negative supply electric powers to a resonance circuit are made unbalanced, and DC component is supplied to the load Z, and for example, in the case where the load Z is an electric discharge lamp, flickering due to putting-out or moving stripes can be prevented from being caused. |
