U.S. Philips Corporation

Hans G Ganser

Hans Peter Stormberg

Ralf Schafer

Hanns Ernst Fischer

Gunther Hans Derra

Dieter Leers

Pieter Postma

Klaus B Lohn

Martin Ossmann

Holger Moench

Rob Snijkers

Reinhard Kersten

Rolf Schafer

Thomas V Kr&uuml;cken

Ralf Sch/a/ Fer

A circuit for operating a high pressure discharge lamp comprising input terminals for connection to a supply voltage source, output terminals for connecting the high pressure discharge lamp, and apparatus, coupled to the input terminals, for supplying an alternating lamp current to the high pressure discharge lamp. The lamp current in each period has a mean value Im. At the start of each period, the lamp current is lowered with respect to the mean value Im so as to allow for stable diffuse attachment on the cathodic phase electrode. The circuit is particularly suited for operating a lamp in an optical projection system.

Long life discharge lamp operating circuit with reduced lamp flicker

A circuit arrangement is provided for operating a high pressure discharge lamp with a lamp current which, in successive periods, has opposite polarities. The lamp is provided with at least two main electrodes being spaced an electrode distance from each other. The circuit arrangement includes input terminals for connection to a supply source, output terminals for connection to the high pressure discharge lamp, and an element, coupled to the input terminals, for supplying the lamp current to the high pressure discharge lamp, which current, in successive periods, has a predetermined shape. The circuit arrangement is provided with an element for detecting a first parameter indicative of the electrode distance and forming a first signal dependent on the first parameter and with an element for reshaping the lamp current, in successive periods, in dependence of the thus formed first signal.

Circuit arrangement for operating a high-pressure discharge lamp

A circuit for operating a discharge lamp having circut input terminals for connection to a supply voltage source and an inverter coupled to the circuit input terminals for generating an AC voltage at a frequency f from a supply voltage supplied by the supply voltage source. A piezotransformer has transformer input terminals coupled to the inverter output terminals. Terminals for lamp connection are coupled to the inverter output terminals and is provided for detecting whether the lamp has ignited. A protective device is coupled between the output terminals of the inverter and the transformer output terminals so that the inverter is effectively protected against damage due to ignition pulses generated by the piezotransformer.

Discharge lamp operating circuit using piezoelectric transformer and

A circuit arrangement for operating a lamp has circuit input terminals for connection to a supply voltage source. An inverter is coupled to the circuit input terminals for generating an AC voltage with a frequency f from a supply voltage supplied by the supply voltage source and includes inverter output terminals. A piezotransformer has input terminals coupled to the inverter output terminals. Terminals for lamp connection are coupled to the inverter output terminals. A detector detects whether the lamp has ignited. The transformer input terminals are connected to the inverter output terminals only by means of passive components and the inverter comprises means coupled to the detector for changing the frequency f in response to the ignition of the lamp. The circuit arrangement is simple and inexpensive and need not provide a device for switching the piezotransformer out of the circuit after ignition of the lamp.

Inventer-ballast using a piezoelectric transformer

The invention relates to a measuring circuit for detecting the amount of deposited electrode material on the wall of a lamp vessel of a discharge lamp by measuring the power of infrared radiation within a specific wavelength range, comprising a detector for generating an electrical signal constituting a measure for the power of the infrared light in said specific wave length range. According to the invention the measuring is done in a time lapse starting after a predetermined time interval following the extinguishing of the discharge lamp. An increased accuracy of the measurement is thereby realized.

Circuit arrangement for detecting the amount of deposited electrode

A circuit arrangement for operating a high pressure discharge lamp includes input terminals for connection to a supply voltage source and an apparatus coupled to the input terminals for supplying an alternating lamp current to the high pressure discharge lamp. A device (III) is provided for generating a current pulse in each half period of the lamp current. This current pulse has the same polarity as the lamp current and is superimposed on the lamp current in the latter part of a predetermined fraction of the half periods of the lamp current. The circuit substantially suppresses flickering of the discharge arc during lamp operation.

High pressure lamp operating circuit with suppression of lamp flicker

A circuit arrangement for A.C. operation of high-pressure gas discharge lamps comprising a mains alternating voltage source and a high-frequency oscillator (3) supplied with direct current and which produces a high-frequency current through the lamp superimposed on the mains alternating lamp current. The oscillator comprises a high-frequency transformer (7) and a transistor (11) connected in series with the transformer primary (8). The transistor can be periodically switched on an off. A secondary (9) of the transformer is connected in series with the lamp. Losses are reduced if the ratio between the switching-on and switching-off time (duty cycle) of the transistor (11) is chosen so small that the effective value of the high-frequency current coupled into the lamp lies between 0.05 and 5% of the mains alternating lamp current. An auxiliary device (16 to 19, 25) interrupts the periodic switching of the transistor (11) outside the proximity of the zero passages of the mains alternating lamp current.

Circuit arrangement for A.C. operation of high-pressure gas discharge

A circuit arrangement for adjusting the operating voltage of high-pressure gas discharge lamps to a given nominal value, comprises a controllable current limiter connected in series with the lamp and an adjustment circuit (3) for controlling the latter. The output signal of the adjustment circuit is determined by the difference between a given desired value determining the nominal lamp operating voltage and an actual value dependent upon the instantaneous lamp operating voltage. In parallel with the lamp (1) a heating element (5) is arranged which is in thermal contact with a temperature-dependent electrical element (6), which produces the actual voltage dependent upon the instantaneous lamp operating voltage.

Circuit arrangement for adjusting the operating voltage of high-pressure

An electrode having a self-supporting cylindrical open coil of tungsten or molybdenum wire having a lead wire of tungsten or molybdenum passed coaxially through the coil and connected thereto. The turns of the coil engage each other. The central lead wire has a smaller diameter than the coil wire, this thin portion extending to a location just before the outermost turn of the coil.

Heatable electrode for high-pressure gas discharge lamps

A circuit arrangement for operating a high-pressure gas discharge lamp (3) with a pulsatory direct current produced from an alternating voltage supply (A, B) via a full-wave rectifier (1). The output of the full-wave rectifier is shunted by a series arrangement of a diode (4) and a capacitor (5). The capacitor (5) has a value of 10 nF to 1 .mu.F and a resistor (6), which is high-ohmic with respect to a current limiter (2) in series with the lamp (3), is connected in a current circuit between the end of the capacitor facing the diode and the lamp (3). As a result, a low re-ignition voltage is attained during the head-up phase of the lamp.

Circuit arrangement for operating a high-pressure gas discharge lamp

A method of operating a high-pressure metal vapor discharge lamp at a periodic operating voltage of more than 500 Hz wherein the operating voltage is suddenly varied in phase at intervals, and preferably also wobbled in frequency, in order to avoid acoustic resonances in the lamp.

Method of operating a high-pressure metal vapor discharge lamp and

A circuit arrangement for operating high-pressure gas discharge lamps (6) with a current of higher frequency comprising a switching mains section including a switching transistor (4) and a control device (9), in which an upper and a lower reference current level (O,U) are produced. The switching transistor is switched to the non-conducting state when the lamp current exceeds the upper level (O) and is switched to the conducting state when this current falls below the lower level (U). The interval between the reference current levels (O,U) is more than 10% of the average lamp current and a further intermediate reference current level (M) is provided at which the switching transistor is switched each time at a predetermined number of passages of the lamp current through the intermediate reference current level.

Circuit arrangement for operating high-pressure gas discharge lamps

A circuit arrangement for starting and operating a high-pressure gas discharge lamp having an outer starting electrode connected to an igniter. A full-wave rectifier (1) is connected to an alternating voltage supply (A, B) and has an output shunted by a series arrangement of a diode (4) and a capacitor (5). The capacitor is discharged in part through the lamp (3) after each half period of the alternating voltage. A resistor (6), which is high-ohmic with respect to a current limiter (2), is connected in the current circuit between the end of the capacitor (5) facing the diode (4) and the lamp (3). Thus, starting of the lamp is facilitated.

Circuit arrangement for starting and operating a high-pressure gas

A circuit arrangement for operating a high-pressure gas discharge lamp (14) with high frequency current in which a direct voltage is supplied to a transistor bridge (5 to 8) having a transverse branch in which is arranged a choke coil (13). The clock (switching) frequency of the transistor bridge is varied within each period of the AC mains alternating voltage in dependence upon the current derived from the AC mains voltage.

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Stolberg, Germany

Hans G Ganser