Abstract: A discharge lamp lighting circuit 1 includes a direct current-alternating current converting circuit 3, a starting circuit 4, controlling means 15 for controlling power, switching elements 5H, 5L driven by the controlling means 15 and a series LC resonance circuit (7p, 8, 9). A frequency modulating circuit is provided for restraining acoustic resonance by modulating a frequency of driving the switching element. When a basic frequency related to the drive frequency is equal to or higher than 1 MHz, a modulation width is set to be equal to or higher than 20 kHz.

Abstract: A discharge lamp lighting circuit 1 includes an electric power supply part and a control part. The control part generates a control signal (Sc) for controlling the magnitude of electric power based on a lamp voltage (VL) of a discharge lamp. The electric power supply part supplies the electric power based on the control signal (Sc) from the control part to the discharge lamp. The control part has a differential computation part for differentiating a lamp voltage corresponding signal (VS) with respect to time and generating a first differential signal Sd1 (=dVS/dt), and an integral computation part for integrating a second differential signal (Sd2) which monotonously increases and decreases as the first differential signal (Sd1) increases and decreases with respect to time and generating a first integral signal (Si1), and generates the control signal (Sc) so that the electric power decreases with an increase in the first integral signal (Si1).

Abstract: A discharge lamp lighting circuit includes a power supplying portion having a half bridge inverter for converting an output of a DC power supply into AC power, and a bridge driver for driving the half bridge inverter, and a control portion for generating a control signal S1 to control a driving frequency F of the bridge driver. The control portion has a random number generating circuit for generating a random number signal and changes the driving frequency F in accordance with the random number signal at a time interval of N/F, wherein N is an integer of one or more.

Abstract: A discharge lamp lighting circuit supplies an AC power for lighting a discharge lamp. The discharge lamp lighting circuit includes a power supply portion for supplying the AC power to the discharge lamp and a control portion for controlling the magnitude of the AC power. The power supply portion includes a series resonance circuit including transistors, a transformer, a capacitor and an inductor and a bridge driver for driving the transistors. The control portion controls the bridge driver so that the AC power increases intermittently. Thus, as the temperature of electrodes can be increased while suppressing the temporal average value of the supplied power within a rated power, the movement of a luminous point at the time of lighting the discharge lamp with a high frequency can be suppressed.

Abstract: A discharge lamp lighting circuit 1 includes an electric power supply part and a control part. The control part generates a control signal (Sc) for controlling the magnitude of electric power based on a lamp voltage (VL) of a discharge lamp. The electric power supply part supplies the electric power based on the control signal (Sc) from the control part to the discharge lamp. The control part has a differential computation part for differentiating a lamp voltage corresponding signal (VS) with respect to time and generating a first differential signal Sd1 (=dVS/dt), and an integral computation part for integrating a second differential signal (Sd2) which monotonously increases and decreases as the first differential signal (Sd1) increases and decreases with respect to time and generating a first integral signal (Si1), and generates the control signal (Sc) so that the electric power decreases with an increase in the first integral signal (Si1).

Abstract: A discharge lamp lighting circuit 1 includes a direct current-alternating current converting circuit 3, a starting circuit 4, controlling means 15 for controlling power, switching elements 5H, 5L driven by the controlling means 15 and a series LC resonance circuit (7p, 8, 9). A frequency modulating circuit is provided for restraining acoustic resonance by modulating a frequency of driving the switching element. When a basic frequency related to the drive frequency is equal to or higher than 1 MHz, a modulation width is set to be equal to or higher than 20 kHz.