U.S. Philips Corporation

Meerten Luursema

Hubertus M Chermin

Herman Adrianus Smulders

Hilbert Palmers

Jaap Rozenboom

Nicolaas H Reijnders

Frederik H Alkema

A circuit arrangement for operating a high-pressure discharge lamp provided with a ballast circuit VI for generating a current through the high-pressure discharge lamp from a supply voltage. A controller is provided for controlling the power consumed by the high-pressure discharge lamp. The run-up behavior of the high-pressure discharge lamp is governed by an apparatus III for controlling the luminous flux of the high-pressure discharge lamp and by a device IV for the automatic activation of the controller after the run-up of the high-pressure discharge lamp. As a result, the luminous flux of a high-pressure discharge lamp operated by the circuit arrangement has the same, substantially constant value during substantially the entire time duration of the run-up of the high-pressure discharge lamp as during stationary lamp operation.

High pressure discharge lamp operating circuit with light control during

A circuit arrangement for operating a high-pressure discharge lamp such that the high-pressure discharge lamp supplies a luminous flux of at least 60% of the nominal luminous flux within 1 s after ignition. The circuit arrangement is made up of a static converter for generating a DC voltage, a commutator provided with lamp connection terminals, a circuit for current stabilization during stable lamp operation by control of the static converter, and a circuit responsive to an instantaneous lamp voltage signal for operating the lamp with an increased run-up current and an increased power as compared with nominal rated operation during a lamp run-up period. A further circuit is provided so that the operation at the increased power includes at least a portion of the lamp run-up period for transition to normal operation. During this portion the increased power has a falling characteristic with a time constant that is independent of lamp voltage.

Discharge lamp power control circuit with reduced light fluctuations

A switching device for operating a lamp (4) by means of a pulse-shaped voltage (V1) in which switching means (3) generate the pulse-shaped voltage (V1) from an input voltage. The amplitude of the pulse-shaped voltage (V1) is proportional to the input voltage. A pulse width modulator (2) supplies control pulses to the switching means and a first auxiliary circuit (S1) generates a first signal that is derived from the pulse-shaped voltage (V1). The first signal is proportional to the average value of the pulse-shaped voltage. A control device (1) makes the first signal substantially equal to a second signal by supplying a control signal to the pulse width modulator. A second auxiliary circuit (S2) generates the second signal, which is inversely proportional to the input voltage, whereby the switching device is able to operate the lamp at a voltage with a constant effective value.

Switching device

A circuit for operating a discharge lamp (1) by means of a direct voltage. The circuit comprises direct voltage terminals (A,B) for connection of a direct voltage source, alternating voltage output terminals (K,L) for connection to the discharge lamp, a direct voltage/alternating voltage sine converter (3), and a current limiter (5) for limiting the current through the lamp in its operating condition. A controllable direct voltage converter (2) is coupled between the sine converter and the direct voltage input terminals.

Circuit arrangement for operating a high-pressure discharge lamp

An electrical device for igniting and supplying a low-pressure mercury vapor discharge lamp (11) provided with two preheatable electrodes (12,13). A series arrangement (12, 4, 14, 13) comprising the two lamp electrodes (12, 13), a PTC resistor (14) and a second winding (4) of a transformer fed back negatively with respect to a first winding (3) thereof is connected to a connection point of the first transforming winding. This series arrangement (12, 4, 14, 13) is further connected to a second connection point of the first transformer winding (3). Thus, the electrical device will readily ignite and supply the lamp and will also protect the PTC resistor of the electrical device should the lamp fail to ignite even with lamp electrodes that are uninterrupted.

Discharge lamp circuit with protected PTC resistor

An energization arrangement for a discharge lamp includes a DC/AC converter to which a discharge lamp (81) is connected. The lamp is shunted by a relay contact (90) to obtain an electric circuit through which two electrodes (83, 84) of the lamp can be preheated. It is advantageous to insure that the relay contact is closed before a voltage occurs between the electrodes of the lamp. This prevents the lamp from exhibiting a transient flash at too cold electrodes. A timing circuit (40-47) ensures that the relay contact remains closed for about 1 second, after which the lamp ignites with warm electrodes. No electrical losses occur in the relay winding (30) during operation of the lamp.

High efficiency converter for discharge lamps

A control circuit for a DC-AC converter which improves the efficiency of the converter and enables it to operate at a higher frequency using the same semiconductor switches. The residual voltage across the conductive switch (9, 10) of the converter is compared with a reference voltage (23) via an analog OR-gate (26) and the control signal for the conductive switch is controlled such that the residual voltage is set to a desired value.

Control circuit for a DC-AC converter

Electronic flashgun having a rotatable reflector accommodating a discharge lamp, the reflector having means to move filters in front of the flash discharge lamp. The filters are inserted via an elongate coverable aperture (5) in an end partition (2a).

Electronic flashgun

The invention relates to an electronic flashgun comprising an arithmetic unit (9) for computing a diaphragm stop number-distance combination, the arithmetic unit comprising a transparent element (11) with a pointer (10). This element is connected to a neutral density filter disc (21) having a variable density and located in front of a light cell (6) provided at the light exit side of the flashgun. The pointer directly indicates a diaphragm stop number on a diaphragm stop number scale (13) of the arithmetic unit.

An arrangement for starting and operating a low-pressure mercury vapor discharge lamp provided with preheatable electrodes. The lamp is supplied from a battery via two direct-to-alternating current converters connected between the battery and the lamp. One converter is a voltage-controlled converter which exclusively effects the preheating of the electrodes, whereas the other converter supplies the lamp current only. This arrangement provides reliable ignition and operation of the lamp even in the case of a large variation in the battery voltage.

Electric device for starting and feeding a metal vapor discharge lamp

A device for starting a discharge lamp by means of a transistor starter provided with an auxiliary transistor for stopping the starting procedure if the lamp fails to ignite. A zener diode is included in the control circuit of the auxiliary transistor, a capacitor is connected in parallel across the lamp, and a self-inductor is included in the connection from the lamp to the main transistor. The auxiliary transistor has a second function in that, by the action of the zener diode, the auxiliary transistor delays the conduction of the main transistor so that a large rise of the voltage between the lamp electrodes is produced, which provides a more reliable ignition of the lamp within a large temperature range.

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Eindhoven, Netherlands

Meerten Luursema