U.S. Philips Corporation

Henk Houkes

Pieter Postma

Paul R Veldman

Andreas C Van Veghel

Franciscus H Lammers

Jan W Denneman

Andreas G Van Veghel

A DC-AC converter for igniting and supplying a gas discharge lamp (1). The converter has two input terminals (C, D) to be connected to a DC voltage source. The input terminals are interconnected by means of a series arrangement that includes a load circuit comprising at least the lamp (1) and an induction coil (5), and a first semiconductor switching element (6) including a freewheel diode. The load circuit is bridged by a circuit including a second semiconductor switching element (7) with a freewheel diode. The semiconductor switching elements (6, 7) are provided with control circuits for rendering said switching elements alternately conducting. The control circuit (9) of switching element (7) has a voltage measuring point which is connected via a rectifier element (10) to the control circuit (8) of the first switching element.

High frequency ballast for a gas discharge lamp

A DC-AC converter for igniting and supplying a low-pressure discharge lamp, e.g. an electrodeless low-pressure gas discharge lamp. The converter has two input terminals (9, 10) for connection to a d.c. voltage source. The input terminals are connected to a series arrangement controlled semiconductor switching element (12), a first coil (14) and a parallel circuit having the discharge lamp 15 in one of its branches. The control electrode and a main electrode of the controlled semiconductor switching element are connected together by means of a secondary winding (21) of a transformer (17) having a primary winding (16) that forms a part of the parallel circuit. The converter includes a starter circuit comprising a resistor (28) connected between a main electrode and the control electrode of the semiconductor switching element and a capacitor (29) coupled between the control electrode and one end of the secondary winding (21) of the transformer.

DC-AC converter for igniting and supplying a discharge lamp

An electrodeless low-pressure discharge lamp comprising a lamp vessel (1) which is sealed in a vacuum-tight manner and is filled with a metal vapor (for example mercury) and a rare gas, this lamp being provided with a core (4) of magnetic material (for example ferrite), while during operation of the lamp, and electric field is produced in the lamp vessel by means of a winding arranged to surround this core and a high-frequency supply unit connected thereto, the lamp vessel further being provided with an internal transparent conductive layer (11) and an external conductive layer (12), which during operation of the lamp is connected to one of the mains conductors and which together with the internal conductive layer (11) forms a capacitor.

Electrodeless low-pressure discharge lamp

An electrodeless low-pressure discharge lamp having a lamp vessel (1), a core (3) of magnetic material, a first winding (7) arranged to surround the core and connected to a high-frequency supply unit (4), one of the lead-in wires of this winding being electrically connected to a lead-in wire of a second winding (11) with a free end (12), while during operation of the lamp the potential drop between the ends of the second winding is substantially equal to the potential drop between the ends of the first winding and the potential drops in the two windings vary in opposite senses. Interference currents at the supply mains to which the lamp is connected are then strongly suppressed.

A discharge lamp having a sealed glass vessel filled with gas and a metal vapor, operated with a supply at a frequency of at least 20 kHz. An interference-suppressing conductive layer is arranged on a wall surface surrounding the discharge, and connected to an electric supply lead-in wire. Preferably, a plurality of insulated metal rings, on the outside of the wall, also surround the discharge.

Discharge lamp with interference shielding

A frequency converter for supplying an electrodeless discharge lamp comprises a VMOS controlled semiconductor switching element and a parallel circuit including an electric coil coupled to a discharge path of the lamp. A control circuit of the switching element includes a transformer which, in combination with two Zener diodes, results in a low-loss control circuit for the VMOS and, hence, an increased system efficiency.

Frequency converter for supplying an electrodeless discharge lamp

A Darlington pair having a high-voltage power transistor for a line deflection circuit and/or a switched-mode power supply. The drive circuit comprises two current paths, namely a switch-on path coupled to the base electrode of the high-voltage power transistor and which comprises a switched-mode current source, and a switch-off path which comprises an inductance, a substantially constant-voltage source and a switch and which is included between the base and emitter electrode of the high-voltage power transistor, the switched current flowing while the switch is cut-off and vice versa.

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Eindhoven, Netherlands

Henk Houkes