JPH0243298B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a discharge lamp starting device.

Recently, so-called electronic starters have been proposed that can immediately start discharge lamps and are small and use semiconductor switch elements such as thyristors, pulse transformers, etc.; Various discharge lamp starting devices using switch elements have also been proposed.

An example of this is shown in a block diagram in FIG.

In Fig. 1, when commercial power supply V _s is applied, ballast 1, filament F 1 of lamp 2, normally closed thermal switch ₃ , main heater 8, filament
A preheating current flows through F ₂ and heats both lamp filaments F ₁ and F ₂ . The preheating current flowing through the main heater 8 heats the main bimetal 3b of the thermal switch 3, and after a certain period of time, the contacts 4a and 4b are opened, and the lamp 2 is turned on due to the generation of a kick voltage due to the inductance of the ballast 1. The lighting determination circuit 5 detects that the lamp is lit, and drives the drive circuit 6 to turn on the holding heater 7.
The thermal switch 3 is kept in an open state to maintain the lighted state.

The present invention was proposed in order to improve the discharge lamp starting performance of such a device, and in a discharge lamp starting device using a switch element for generating a kick voltage,
It is an object of the present invention to provide a discharge lamp starting device which improves the starting performance of a discharge lamp by increasing the pulse-like kick voltage generated by a ballast when a contact is opened.

Although there are various contact materials for switch elements, conventionally AgCdO and AgSnO ₂ have been used as contact materials in the above device.
This material is generally widely used for interrupting current, and has excellent welding resistance, which prevents the transfer phenomenon that occurs when DC is interrupted (the contact material on the negative side scatters and adheres to the contact on the positive side). When used in a discharge lamp starting device, a diode is inserted in series in the preliminary circuit to create a half-wave preheating method, and even if the preheating current is increased. , does not cause dislocation or welding, and has an excellent lifespan.

However, the present inventor has found that the contact material of the switch element is closely related to the starting performance of the discharge lamp in the discharge lamp starting device.

In other words, while various materials were examined, AgCdO
It has been found that, while materials such as AgSnO ₂ and AgSnO 2 have excellent lifespans as described above, their performance is not sufficient in terms of the starting performance of discharge lamps, which is the primary function of discharge lamp starting devices. Furthermore, since the W-based material has a very high contact resistance, it is necessary to make the contact pressure of the contact point very large. As a starter, it takes a long time to start, and if the contact pressure is increased, the capacity of the external heater must be increased to separate the contacts.Furthermore, the contact resistance increases over the lifespan, resulting in poor continuity. have. After further consideration, Pd,
It has been found that the starting performance of discharge lamps is significantly improved by using AgPd for the contacts. In other words, Pd-based contacts have high pulse voltage, low contact resistance, and long life, making them ideal as contact materials for starters.

This seems to be due to the following reasons. That is, AgCdO and AgSnO ₂ have a small minimum arc current, while Pd and AgPd have a large minimum arc current. The minimum arc current means that even if the contacts open, the two contacts are electrically connected by arc discharge, and the current continues to flow during that time. and,
When the current value falls below a certain value I _nio , the arc discharge disappears and the current is electrically cut off. this
The I _nio value is called the minimum arc current. Therefore,
The smaller the I _nio of the contact, the smaller the generated pulse voltage value will be when used in a discharge lamp starting device having the above-described circuit configuration. Therefore, if Pd or AgPd is used as the contact material, since these have a larger minimum arc current value than the previously described contact materials, the generated pulse voltage is also higher and starting performance is improved.

FIG. 2 shows an embodiment of the present invention. In general, the thermal switch 3 has bimetals 3a and 3b made of the same material facing each other at room temperature, as shown in Figure 2A, and compensates for changes in the ambient temperature so that the contact pressure does not change. be. In other words, 3a and 3b deform by the same distance in the same direction as the ambient temperature changes, and the contact pressure remains constant. However, when the ambient temperature decreases and the temperature becomes low, the thermal switch changes as shown in FIG. 2B, and the contact point changes. Therefore, contact materials with a large minimum arc current (for example, Pd,
AgPd) and other parts are AgCdO or
If the structure uses AgSnO ₂ -based contact material,
At low temperatures, the bimetals deform each other and come into contact at the shaded areas in Figure 2 (b) (contacts with large minimum arc current), so the value of the generated pulse voltage can be increased at low temperatures. The starting performance of the discharge lamp can be improved. In other words, in general, discharge lamps have particularly poor starting performance at low temperatures, but at normal temperatures it is less of a problem than at low temperatures.On the other hand, materials with a large minimum arc current generally have poor welding resistance compared to materials with a small minimum arc current. Therefore, if a material with a large minimum arc current is used as a contact only at low temperatures, the life of the contact can be sufficiently extended while improving the starting performance.

As described above, the present invention provides a device for starting a discharge lamp using the kick voltage when the switch element is opened, in which Pd or Pd is used as the contact material of the switch element.
The use of AgPd has the effect of significantly improving the starting performance of the discharge lamp.

[Brief explanation of the drawing]

FIG. 1 shows a general discharge lamp starting device, and FIGS. 2A and 2B show bimetal contacts in the starting device of the present invention. 3a, 3b...bimetal, 4a, 4b...contact, 5...layer of insulator.

Claims (1)

[Claims] 1. A power source is connected to the power supply side terminals of both filaments of the discharge lamp through at least an inductive current limiting element, a switch element is connected between the non-power supply side terminals of both said filaments, and when the switch element is opened, said current limiting element is connected. A discharge lamp starting device for starting a discharge lamp by a kick voltage generated in an element, characterized in that palladium or silver palladium is used as a contact point of a switch element.