568 results about "Lamp current" patented technology

Disclosed a high pressure discharge lamp driving apparatus for driving a high pressure discharge lamp during a stable operation thereof with an AC lamp current alternating for opposite half-cycle periods, the apparatus comprising an AC lamp current supply for supplying the AC lamp current to the high pressure discharge lamp, a detector for detecting the output AC lamp current to the high pressure discharge lamp, a controller responsive to the detector for controlling the AC supply to output the AC lamp current with a waveform which is characterized by that (i) a mean value in the second half of each half-cycle period is larger than the means value of the first half of each half-cycle period, (ii) no pulse current is contained in the second half of each half-cycle period, (iii) the AC lamp current has a maximum value immediately after polarity change between the positive and negative half-cycle periods, and (iv) the AC lamp current has also a waveform defined by that the ratio (d / a) of the maximum value (d) of the AC lamp current and a mean value (a) of the AC lamp current in its each half-cycle period satisfies a following equation.

An electronic ballast for high intensity gas discharge lamps where the wave form of the lamp current is square wave providing acoustic resonance and flickering free operation. The circuit, having high efficiency, operates in a wide temperature range providing ideal ballast curve and reliable ignition for the lamps. Furthermore, significant energy saving can be achieved by its externally controlled built in dimming capability.

In a lamp operation controller and a method thereof, for obtaining a stable light emission, simply and certainly, without necessity of detection of a parameter accompanying discharge, the lamp operation controller, for operating a discharge lamp having a pair of electrodes, which are disposed at both ends of a light emission tube to have a predetermined distance therebetween, converts electric power of an electric power source 1, through an inverter, into alternating voltage and alternating current, changing the polarity thereof continuously and alternately, so as to produce operating current, and apply that across the pair of the electrodes of the discharge lamp, thereby letting the lamp to emit a light. A driver circuit provides a pulse at a trailing edge of the lamp current or the lamp voltage to be supplied when the discharge lamp emits the light, and also determine amplitude of the pulse, in accordance with fluctuation on the lamp voltage (VL) with respect to lighting time of the discharge lamp, which is measured in advance.