U.S. Philips Corporation

Koninklijke Philips Corporation N.v.

Frans Slegers

Anton Cornelis Blom

Hendrik J Blankers

Christofher Daniel Charles Hooijer

Thijs Oosterbaan

Nicolaas J De Jong

Johannes H Otten

Johannis Antonie Amerens Toonen

Bernardus J Ter Bogt

Johannes H Nellen

Johannus W Kole

An ignition circuit for igniting a gas discharge lamp generates a high voltage gas breakdown pulse by building up a current through a primary winding of a transformer. After a predetermined period and thus when a predetermined current flows through the primary winding, a capacitance is switched in series with said primary winding, thereby generating said high voltage gas breakdown pulse in a secondary winding of said transformer. After generating the high voltage pulse, the capacitance is short-circuited in order to preserve energy in the primary winding. The preserved energy is employed to build up energy again for a next high voltage pulse in a short time. At a high repetition rate and high voltage of the generated pulses, the ignition circuit according to the present invention is also suitable for driving the gas discharge lamp during a take-over period following the gas breakdown of the lamp for heating the lamp electrodes.

Multi-pulse ignition circuit for a gas discharge lamp

During stationary operation a circuit arrangement for operating a high-pressure discharge lamp supplies a direct current to the lamp which is commutated at a low-frequency. During take-over, between ignition and stationary operation, a high frequency current is supplied to the lamp after each commutation during a time interval that is shorter than half a cycle of the commutation. By supplying the lamp in this way, it forms a smaller load during take-over, so that the requirements that the circuit arrangement has to meet are less severe.

Circuit arrangement for operating a discharge lamp

A circuit arrangement for igniting a high pressure discharge lamp includes a secondary winding of a pulse transformer which is at least partially capacitively shunted forming a tuned filter. The tuned filter preferably forms a band pass filter for passing the second harmonic of the signal produced by a pulse generator. An increase in the supply of current during take-over results thereby minimizing the time required for ignition.

Ignition scheme for a high pressure discharge lamp

A circuit arrangement is provided with a controlled switch which is controlled by means of a periodic switching signal for operating an oscillation circuit at a frequency f, and with a control circuit for generating the periodic switching signal. The control circuit comprises a pulse width generator for generating a periodic square wave signal with a half cycle duration which is adjustable in steps of a value T and which has a value of at least t. The circuit arrangement is characterized in that, with 2*(t+N1*T)&lt;1/f&lt;2*(t+(N1+1)*T) in which N1 is an integer number, the periodic switching signal is built up from a repetitive chain of square wave signals with a repetition cycle which comprises n1 half cycles of a duration t+N1*T and n2 half cycles of a duration t+N2*T, wherein N2 is &gt;N1 and is an integer number.

Oscillation circuit driven alternately by two different square wave

In an ignition circuit for a high-pressure discharge lamp having a pulse generating circuit in which ignition pulses are generated by a voltage-dependent breakdown element and a pulse transformer, a bandpass circuit has been inserted between the secondary winding of the pulse transformer and the discharge lamp. The bandpass filter is tuned to the fundamental frequency or a harmonic of the pulses generated by the pulse generation circuit.

Discharge lamp ignition circuit having a bandpass filter connecting the

The invention relates to a circuit arrangement for igniting a high-pressure discharge lamp (L), provided with input terminals (C,D) for connection to a commutating supply source with a square-wave supply voltage; a pulse-generating circuit (IV) provided with a voltage-dependent breakdown element (3) and with a voltage-raising network (2) formed by a network of rectifiers and capacitors; a pulse transformer (1); and an electrical connection between a secondary winding (12) of the pulse transformer and lamp connection terminals (E,F). The voltage-raising network (2) is in addition provided with inductors means (21, 22). The result of this is that a strongly increased voltage is available across the breakdown element substantially instantaneously after each commutation of the commutating supply voltage.

High-pressure discharge lamp igniting circuit in which the

A circuit for high-frequency operation of a discharge lamp. The circuit includes a load branch provided with terminals for connection to the discharge lamp and with an electrode heating transformer having a primary winding and secondary windings. Each secondary winding is shunted by a branch comprising an electrode of the discharge lamp. At least one switching element generates a high-frequency current through the load branch from a supply voltage. A control circuit generates a control signal for rendering the switching element conducting and non-conducting at a high frequency. A dimmer circuit is coupled to the control circuit for adjusting the frequency of the control signal. Each branch shunting a secondary winding of the transformer also includes an inductive element and a capacitive element and has a resonance frequency which is different from the resonance frequency of the load branch. Thus, a discharge lamp operated by this circuit can be dimmed over a wide range and provides a comparatively long electrode life and with very little blackening at the ends of the discharge vessel.

Discharge lamp operating circuit with frequency control of dimming and

The generator comprises a ferromagnetic core (1) having a primary winding (3) and a secondary winding which comprises a number of concentric secondary coils (7A-7F), which are wound with the same winding senses and have substantially the same number of turns and are provided with a layer of insulating material (9A-9E) between every two consecutive coils. The high-voltage portion of the generator is formed by a number of sections (19A, 19B, 19C), each of which comprises at least two series-arranged secondary coils (7A-7F), the number of secondary coils being equal for all sections and the last coil of each section being arranged in series with a rectifier (13A, 13B, 13C). All sections are arranged in series such that the rectifiers have the same forward directions.

Generator for generating a high d.c. voltage

A degaussing circuit for a color television receiver, in which the degaussing coil is in series with a PTC thermistor to which an NTC thermistor is thermally coupled and which is at the same time a protection resistance for a supply voltage circuit in the receiver.

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Eindhoven, Netherlands

Frans Slegers