JPH031918Y2 - - Google Patents

Description

[Detailed explanation of the idea] This invention relates to a discharge lamp lighting device.

Discharge lamps for copying machines or facsimile machines are required to light up instantly when a lighting signal is applied, and for this purpose the filament is always preheated when the lamp is not lit. on the other hand
For FL lamps, it is necessary to stop preheating the filament while the lamp is lit. Therefore, when using this type of lamp, it is required to control the filament to stop or start preheating depending on whether the lamp is lit or not. By the way, some FL lamps of this type have fins installed on both sides of the filament in order to increase the lamp current.

FIG. 1 shows a filament mechanism, in which F is a filament, and both sides of the filament are supported by struts S.
The column S is supported by a glass stem or the like.
Fins P supported by respective supports S are arranged on both sides of the filament F. A portion of the lamp current flows into the fin P to cope with the increase.

When using a discharge lamp with a filament of this kind of configuration, when the lighting circuit is turned off to turn off the discharge lamp as described above, at that moment electrons are still floating near the filament. When the preheating circuit is operated and a preheating voltage is applied to the filament, discharge may occur between the fins P, resulting in a short circuit. In such a state, an overcurrent will flow through the support S, and there is a risk that the filament structure will be damaged.

The purpose of this invention is to prevent damage to the filament when the discharge lamp is turned off even if the discharge lamp has a filament with fins and is constantly preheated to enable instant lighting.

An embodiment of this invention will be explained with reference to FIG. 1
2 is a discharge lamp, 2 is a lighting circuit, and 3 is a heating circuit.
As shown in FIG. 1, a discharge lamp 1 having a filament with fins is used. The lighting circuit 2 can have any configuration, but in the example shown in the figure, since the power supply terminal 4 to which a DC power source is connected is used, it is preferable that the lighting circuit 2 be configured by a high frequency inverter, for example. That is, a high frequency inverter that oscillates high frequency waves using the DC voltage applied to the power supply terminal 4 as an operating voltage is used as the lighting circuit 2. Although the heating circuit 3 can have any arbitrary configuration, it may also be configured to heat each filament by supplying a DC voltage applied to the power supply terminal 4 to each filament. The lighting circuit 2 operates while the signal _P1 is applied to light the discharge lamp 1. In addition, the heating circuit 3 is
It operates during the period when the signal P ₂ is applied to heat the filament.

Reference numeral 5 denotes a terminal to which a lighting signal is applied, and the transistor 6 is turned on by this lighting signal. Due to this turning on, a signal _P1 is given to the lighting circuit 2.
Since transistor 7 is also turned on when transistor 6 is turned on, transistor 8 is turned off.
Therefore, transistor 9, which had been on until then, is turned off. Due to this turning off, the signal _P2 that had been applied to the heating circuit 3 until then disappears.
That is, when the lighting circuit 2 lights the discharge lamp 1, the heating circuit 3 stops preheating the filament.

On the other hand, as the transistor 6 is turned on, the capacitor 10 is charged via the transistor 6 and the resistor 11 which are turned on. If the supply of the lighting signal currently applied to the terminal 5 is cut off, the transistor 6 will be turned off, so the signal to the lighting circuit 2 will be turned off.
Discharge lamp 1 goes out before P ₂ is finished. Also, when the transistor 6 is turned off, the transistor 7 tries to be turned off, but the capacitor 10 is connected to the diode 1.
2. Since a discharge current flows through the resistor 13 to the base of the transistor 7, the transistor 7 cannot be turned off immediately. When this discharge continues for a certain period of time and the discharge current decreases, the transistor 7 is turned off. This off turns transistor 8 on,
Transistor 9 is also turned on, and heating circuit 3 is now turned on.
A signal P ₂ is applied to the filament and the filament begins to heat up. That is, when the lighting circuit 2 stops lighting the discharge lamp 1, the heating voltage is not immediately applied to the filament by the heating circuit 3. The heating voltage is only applied after a certain period of time determined by the discharge time constant of the capacitor 10. By setting this time longer than the time sufficient for the floating electrons in the vicinity of the filament to disappear, damage to the filament structure can be reliably prevented even when a heating voltage is applied.

In the above description, it is understood that the capacitor charging/discharging circuit consisting of the resistor 11, the capacitor 10, and the resistor 13 constitutes the timer circuit 14. It is clear that this type of timer circuit 14 is not limited to the configuration shown in the figure.

As detailed above, according to this invention, in the structure in which the filament is heated even when the discharge lamp is turned off, the heating voltage is not applied immediately after the lamp is turned off, but is applied after the required time. , it is possible to reliably prevent damage to the filament structure.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a filament structure, and FIG. 2 is a circuit diagram showing an embodiment of this invention. 2...Lighting circuit, 3...Heating circuit, 14...Timer circuit.

Claims (1)

[Scope of utility model registration request] a lighting circuit that starts and lights a discharge lamp; and a heating circuit that cuts off the supply of heating voltage to the filament when the discharge lamp is lit by the lighting circuit and supplies the heating voltage when the discharge lamp is turned off. A discharge lamp lighting device comprising: a timer circuit that outputs a signal for delaying the supply of the heating voltage to the filament for a certain period of time when the discharge lamp is turned off.