Abstract: An apparatus is provided for driving a discharge lamp, the discharge lamp having first and second electrodes, each of the first and second electrodes having first and second terminals. The apparatus includes a switching circuit coupled to the first terminals of the first and second electrodes of the discharge lamp for supplying a high frequency signal to the discharge lamp for igniting the discharge lamp. A starting circuit is provided connected to the second terminals of the first and second electrodes of the discharge lamp and including an inductor and capacitor connected in parallel across the discharge lamp. Alternately, a thermister is provided between parallel connected conductor and capacitor and one of the second terminals of the first electrode of the discharge lamp. Furthermore, circuitry is provided which is connected between the switching circuit and the thermister for deactivating the switching circuit when the thermister is heated to a specified temperature.

Abstract: A high pressure discharge lamp apparatus comprises:a discharge tube and a current limiting device such as a choke coil connected in series for connection across an A.C. power source, anda pulse generator connected by its output terminal in parallel to the discharge tube,the apparatus is characterized in that:said pulse generator impresses reignition pulses on said discharge tube at least during a period defined as from a zero-cross point of the source voltage of the power source to a phase defined by a peak of reignition voltage of lamp voltage waveform when no reignition pulse is impressed on the discharge tube, thereby retaining lamp current of the discharge tube without forming zero-current period,thereby the lamp is stably lit with such a high lamp voltage as is almost equal to the power source voltage and the power of reignition pulse can be saved without harming stability of lighting. Thus a stable lighting of the high pressure discharge lamp with a a high power efficiency becomes possible.

Abstract: In a high pressure discharge lamp apparatus comprising a discharge tube and a current limiting device connected in series, an over-current protecting semiconductor switching device such as a triac (TC) is further connected in series to said discharge tube,the triac (TC) being controlled of its firing angle responding to an output of a current detection circuit which detects a change of the lamp current through a change of the lamp voltage, anda pulse generator is further connected in parallel to the discharge tube and gives reignition pulse thereto at least during the zero-current period in each cycle of the lamp current.