Glow discharge tube ignition circuit for electric discharge tube

Claim 2

An arrangement for starting and operating an electric discharge tube having two electrodes comprising, two input terminals adapted to be connected to an alternating voltage source, the cold ignition voltage of the discharge tube being higher than the voltage of the alternating voltage source, an inductor, means connecting the series arrangement of the inductor and the discharge tube across said two input terminals, auxiliary circuit means including a controlled semiconductor rectifier coupled to the input terminals and to the tube electrodes for generating ignition voltage between the tube electrodes before the tube is ignited of a value which is higher than the voltage of the alternating voltage source, and means connecting the electrodes of the discharge tube together through a glow discharge starter whose ignition voltage is higher than the voltage of the alternating volTage source and lower than the voltage to be generated by the auxiliary circuit means.

Claim 3

An arrangement as claimed in claim 1 wherein the auxiliary circuit means bridges at least a part of said series arrangement and the two electrodes of the discharge tube are preheated electrodes and the series arrangement connected to the input terminals also includes a capacitor which is present in a part of the series arrangement not bridged by the auxiliary circuit means, characterized in that the glow discharge starter is connected to those ends of the tube electrodes which are remote from the input terminals.

Claim 4

An arrangement as claimed in claim 2 wherein the auxiliary circuit means including the controlled semiconductor rectifier is connected to one end of one of the tube electrodes remote from the input terminals of the arrangement.

Claim 5

An arrangement as claimed in claim 1 wherein the auxiliary circuit means bridges the series arrangement of the tube and the inductor.

Claim 6

An arrangement as claimed in claim 2 in which a control circuit of the controlled semiconductor rectifier includes a second series arrangement of a second capacitor and a voltage breakdown element with the breakdown element connected to a control electrode of the controlled semiconductor rectifier, and means connecting a third series arrangement of a first resistor and the second capacitor in parallel with a branch of the auxiliary circuit means including the controlled semiconductor rectifier.

Claim 7

An arrangement as claimed in claim 5, in which the second capacitor is shunted by the main electrode circuit of a transistor, characterized in that a voltage derived from the tube current is applied between the base and a main electrode of said transistor so that the transistor conducts when the tube operates, the voltage across the second capacitor then being lower than the threshold voltage of the breakdown element so as to inhibit the passage of a control pulse to the controlled semiconductor rectifier.

Claim 8

An arrangement as claimed in claim 6, wherein the base of the transistor is connected through a third capacitor to the emitter of said transistor and the connection between said base and the third capacitor is connected through a diode to a tap on the inductor.

Claim 9

An arrangement as claimed in claim 2 adapted for connection to an alternating voltage source of approximately 220 volts, characterized in that the discharge tube is a low-pressure mercury vapour discharge lamp having an operating voltage of approximately 180 volts.

Claim 10

Apparatus for starting and operating an electric discharge tube from a source of alternating current comprising, a pair of input terminals for connection to said source, an inductor, means connecting the inductor and the tube in series circuit across the input terminals, auxiliary circuit means having a first branch including a controlled semiconductor rectifier connected in shunt with a part of said series circuit and operative to generate a voltage across the tube electrodes before the tube is ignited of a value higher than the voltage of the alternating current source, said tube having a pair of electrodes defining a discharge path in the tube and a cold ignition voltage that is higher than the voltage of the alternating current source, a glow discharge starter having an ignition voltage higher than the voltage of the alternating current source and lower than the voltage generated by the auxiliary circuit means, and means connecting the glow discharge starter across the tube electrodes so as to provide a current path from the input terminals through the tube electrodes and the glow discharge starter than shunts the tube discharge path.

Claim 11

Apparatus for starting and operating an electric discharge tube from a source of alternating current comprising, a pair of input terminals for connection to said source, an inductor, means connecting the inductor and the tube in series circuit across the input terminals, auxiliary circuit means having a first branch including a controlled semiconductor rectifier connected in shunt with a part of said series circuit and operative to generate a voltage across the tube electrodes before the tube is ignited of a value higher than the voltage of the alternating current source, said tube having a pair of electrodes defining a discharge path in the tube and a cold ignition voltage that is higher than the voltage of the alternating current source, a glow discharge starter having an ignition voltage higher than the voltage of the alternating current source and lower than the voltage generated by the auxiliary circuit means, and means connecting the glow discharge starter across the tube electrodes so as to provide a current path from the input terminals through the tube electrodes and the glow discharge starter than shunts the tube discharge path.

Claim 12

Apparatus as claimed in claim 9 further comprising a capacitor connected in series with the inductor and the tube across the input terminals so that the capacitor is charged via the controlled semiconductor rectifier during alternate half cycles of the alternating current source to produce a voltage muLtiplier effect.

Claim 13

Apparatus as claimed in claim 10 wherein the auxiliary circuit means is connected between one tube electrode and a junction between the capacitor and the inductor.

Claim 14

Apparatus as claimed in claim 9 wherein the auxiliary circuit means includes a second branch in parallel with the first branch and including a capacitor with a charge path coupled to said input terminals, and a voltage breakdown element coupling the capacitor to the control electrode of the controlled semiconductor rectifier for periodically applying a trigger pulse thereto during alternate half cycles of the alternating current source.

Claim 15

Apparatus as claimed in claim 12 further comprising a switching element connected in shunt with the capacitor and responsive to the flow of tube current to limit the capacitor voltage to a value below the trigger level of the breakdown element thereby to inhibit said trigger pulses when the discharge tube is conductive.

Claim 16

Apparatus as claimed in claim 12 further comprising a second capacitor connected in series with the inductor and the tube across the input terminals so that the capacitor is charged via the controlled semiconductor rectifier during alternate half cycles of the alternating current source.

Claim 17

Apparatus as claimed in claim 9 wherein said first branch of the auxiliary circuit means is connected between one tube electrode and one input terminal such that the one tube electrode completes the current path from the input terminals to the first branch.