Abstract: A ballast for a discharge lamp includes a DC-DC converter which provides a regulated DC output so as to start and keep operating the lamp. A controller is included to give a closed-loop control for regulating the DC output based upon a monitored DC output. The controller also provides an open-loop control which interrupts the closed-loop control for a limited period immediately after the initiation of the lamp discharge in order to supplement a sufficient lamp current which would not expected with the closed-loop control, thereby successfully complementing the lamp start and proceeding to the stable lamp operation.

Abstract: An improved ballast for a discharge lamp includes a DC-DC converter which receives an input DC voltage from a voltage source to provide a pre-starting voltage to make the lamp ready for being ignited or started. The DC-DC converter has a switching element which is driven to turn on and off for generating the pre-starting voltage. A start-accelerating means in included in the ballast in order to vary at least one of the switching frequency and the on-period of the switching element based upon the monitored input DC voltage in a direction of accelerating the increase of the output DC voltage to the pre-starting voltage until the output DC voltage reaches the pre-starting voltage.

Abstract: A power source device includes a voltage converting means to input side of which a DC voltage source is connected and to output side of which a capacitance element and a load circuit are connected, while a control circuit is connected to the voltage converting means and the load circuit, the latter circuit having a load impedance made lower upon starting of a load in the load circuit than that in stable lighting of the load, wherein such control constant as oscillation frequency and duty are made to be substantially constant at the time of the starting and stable lighting of the load, and a switching means in the voltage converting means is turned OFF when the capacitance element has a voltage below a predetermined value.