Abstract: Two high-pressure discharge lampbanks and transformers thereof are connected via a cross connection manner. The two lamp banks include the same number of high-pressure discharge lamps, and the transformers are in a number corresponding to that of lamps in each lamp bank. All the transformers have two outputs, namely, first and second outputs, at a secondary side thereof. First outputs of all the transformers are separately connected to the lamps in a first one of the two high-pressure discharge lamp banks while second outputs of all the transformers are separately connected to the lamps in a second one of the two high-pressure discharge lamp banks. Thereby, lamps in the same lamp bank are maintained at a voltage having the same phase and have a small potential difference among them to avoid interference noises.

Abstract: A brightness-regulating voltage-transforming circuit includes a pulse-width modulator (PWM); a transformer connected at a secondary side to a high-pressure discharge lamp; a voltage-transforming circuit having two transistors connected at bases to outputs of the PWM for the latter to control working frequencies thereof; and a brightness control circuit including a transistor connected at a collector to a middle tap of the transformer and at a base to the PWM for the PWM to control the lamp brightness, and a diode connected at an end to a juncture of a primary side of the transformer and an end of a buffer inductance, and at another end to a voltage source. When the transistor of the brightness control circuit is cut out, energy stored in the buffer inductance is regenerated and sent to the voltage source via the diode, enabling the lamp to have reduced noise interference and increased working efficiency.