GB2083720A

GB2083720A - Lamp ignition device

Info

Publication number: GB2083720A
Application number: GB8127210A
Authority: GB
Original assignee: Helvar Oy AB
Current assignee: Helvar Oy AB
Priority date: 1980-09-10
Filing date: 1981-09-09
Publication date: 1982-03-24
Also published as: FI61599C; FI61599B; GB2083720B; FI802848A

Abstract

An electronic ignition device for a gaseous-discharge lamp comprises an electronic switching means, such as a triac (U2), connected in series with a transformer (N1/N2) and connected to be controlled by a voltage distribution circuit (R1, R2), so that the switching means (U2) becomes conductive on each half-wave of the mains voltage. A capacitor (C1) is connected parallel with the switching means (U2) and is connected to the tapping point of transformer (N1/N2), with the same series connection as the transformer (N1/N2) and switching means (U2), parallel with capacitor (C1), is connected a parallel connection formed by a diode (U1) and a capacitor (C2). <IMAGE>

Description

SPECIFICATION Lamp ignition device The present invention relates to an electronic ignition device for a gaseous-discharge lamp, said device comprising an electronic switching means, such as a triac, connected in series with an econo mically connected transformer and connected to be controlled by a voltage distribution circuit, so that the switching means opens (the triac becomes conductive) on each half-wave of the mains voltage, a capacitor being connected parallel with the switch ing means and being connected to a tapping point of the transformer.

Several hundreds of different circuits have been suggested to electronic ignitation means of a gaseous discharge lamp. Those do not, however, fulfil all requirements set for the ignition of a gaseous discharge lamp. Several commercially available electronic ignition devices produce, during the ignition phase, disturbing noise as a result of too great a direct-current component. With one conven tional electronic ignition device of the above type, the gradual growing of an ignition voltage peak is effected by successive half-cycles, the incandesc ence time becoming relatively long. In addition, this particular ignition device is embodied on the same iron core as is a choke, which is why it cannot be used as a separate replaceable ignition device.Most of the available ignition systems are not capable of providing sufficiently great ignition voltage peaks to effect the ignition of recently introduced new 26 mm gaseous-discharge lamps. The same is true with the ignition of other lamps, such as ring-discharge lamps, U-lamps and red-discharge lamps which are hard to ignite.The above mentioned 26 mm dicharge lamps are nevertheless expected to be come the most popular lamps in the market by virtue of their better light efficiency and colour of light An object of the invention is to provide an improved electronic ignition device for a gaseous discharge lamp, said device producing an ignition accelerating direct-current component of such a magnitude that it does not generate disturbing noise, and said device generating ignition pulses being so effective that even the lamps with difficult ignition characteristics can be rapidly ignited.

According to the present invention there is provided an electronic ignition device for a gaseousdischarge lamp, said device comprising an electro nic switching means connected in series with an economically connected transformer and connected to be controlled by a voltage distribution circuit, so that said switching means opens on each half-wave of the mains voltage, a capacitor being connected parallel with the switching means and being con nected to the tapping point of the transformer, wherein with the same series connection as the transformer and the switching means, and parallel with the aforesaid capacitor there is connected a parallel connection formed by a diode and a further capacitor.

In the accompanying drawings: Figure lisa circuit diagram of the gaseousdischarge lamp electronic ignition device of the invention; Figure 2 shows connection of the ignition device with the lamp circuit, the ignition device being able to be connected to the holder of a regular glow lamp ignition device with no re-installations; Figure 3 shows the mains current during ignition; Figure 4 shows the lamp voltage measured over the ignition device during ignition; Figure 5 shows the mains current if the lamp is not ignited; and Figure 6 shows the shape and temporal location of ignition current Ii with respect to the mains voltage Uv.

An ignition device 1 is intended to be connected in series with the electrodes of a discharge lamp 3 and in parallel with lamp 3. Terminals 2 of the ignition device are connected to the holder of a regular glow lamp ignition device, re-installations being unnecessary. A conventional choke 4 is connected in series with lamp 3. Between the terminals of the ignition device is connected a transformer N1/N2, which is economically connected in series, a parallel connection of a diode U1 and a capacitor C2, as well as a triac U2. Parallel with these is connected a capacitor C1, coupled to the tapping point of transformer N1/N2. The grid of triac U2 is connected via a resistance R3 and a diac U3 to a voltage distribution circuit, provided by resistances R1 and R2 and further fitted with a time constant capacitor C2.

Operation of the ignition connection is as follows.

When the mains voltage rises during a positive half-cycle in such a manner that the voltage of voltage distribution circuit R1, R2 and that of the time constant capacitor C3 rises to the triggering voltage of diac U3, triac U2 will be triggered by means of diac U3 into a conductive state and the current passes through diode U1. Since capacitor C1 is at the moment aiso charged, its discharging through winding N1 generates, by means of transformation ratio N1/N2, a major voltage peak over the discharge lamp.

The function of this half-cycle is to heat the cathodes of a discharge lamp and to just sensitize the lamp to the ignitable state. During the following half-cycle, by means of the above-mentioned time constantvoltage distribution circuit, triac U2 will again be triggered into a conductive state. Thus, there is a charge in capacitor C1 which discharges through capacitor C2 whose charging state was nearly zero.

Hence, the voltage peak generated in the economically connected transformer N1/N2 ignites the lamp.

The lamp is capable of igniting, since triac U2 does not remain in conductive state, as was the case during the preceding half-cycle. This results from the fact that there remains no so-called maintaining current (diode U1 in blocking direction). Figure 3 shows an ignition voltage peak by which the lamp has been ignited.

If the lamp is faulty and, thus, does not ignite after reasonable time, a PTC-resistance in the circuit is heated and switches off operation of the ignition device. A minor rest current will only remain to maintain the PTC-resistance sufficiency warm. The mains current lo, involved in such a situation, is illustrated in Figure 5.

It will be noted that an ignition device according to the invention is capable of providing, by means of simple connection, a quick and efficient ignition which is nevertheless economic in view of the cathodes of a lamp.

Claims

1. An electronic ignition device for a gaseous discharge lamp, said device comprising an electronic switching means connected in series with an economically connected transformer and connected to be controlled by a voltage distribution circuit, so that said switching means opens on each half-wave of the mains voltage, a capacitor being connected parallel with the switching means and being connected to the tapping point of the transformer, wherein with the same series connection as the transformer and the switching means, and parallel with the aforesaid capacitor where is connected a parallel connection formed by a diode and a further capacitor.

2. A device as claimed in Claim 1, wherein by means of a time constant capacitor connected to said voltage distribution circuit, said switching means is arranged to be opened at the same position of each half-wave.

3. A device as claimed in Claim 1 or 2, wherein the said series connection circuit, comprising the transformer, the parallel connection formed by the diode and further capacitor, and electronic switching means, is further provided with a PCT-resistance for stopping the function of said ignition device after a given number of ignition pulses.

4. A device as claimed in any preceding claim, wherein the said electronic switching means comprises a triac.

5. An electronic ignition device substantially as herein described with reference to the accompanying drawings.