JPH0324759B2 - - Google Patents

Description

[Detailed description of the invention] (Technical field) The present invention relates to a discharge lamp lighting device.

(Background Art) For the purpose of miniaturizing lamps or replacing incandescent lamps, fluorescent lamps with tube diameters smaller than conventional ones and bent have been proposed and are being put into practical use. FIG. 1 is a perspective view showing an example of such a lamp, in which an inner tube 4 bent into a U-shape is placed in a discharge space 3 that is kept airtight by an outer tube 1 and a stem (button stem) 2. This is a small fluorescent lamp that houses two tubes, and the inner surface of the U-shaped inner tube 4 is coated with a fluorescent material 5. Further, one end of the U-shaped inner tube 4 is hermetically fixed around the electrode 6 by glass welding, and the other open end 7 is used to cause discharge between the two electrodes 6, 6. In addition, in the figure, 8 is a lighting device part, and 9 is a screw cap.

In order to make such a lamp sufficiently compact and to obtain a sufficient luminous flux, it is effective to make the inner tube 4 thin and long and to make the outer tube 1 small. As shown in FIG. 2, in a lamp with such a double tube structure, heat is diffused over the entire volume of the outer tube 1, compared to a lamp made smaller by simply bending the discharge tube 10. This has the effect of keeping the coldest point temperature of the pipe wall low. However, with the demand for smaller size and higher luminous flux, even if such a configuration is adopted, it is inevitable that the temperature at the coldest point of the tube wall at room temperature will be considerably higher than the temperature that provides the highest efficiency.

Here, the tube wall coldest point temperature refers to the discharge tube (outer tube)
The mercury vapor pressure inside the tube is determined at this temperature, and the highest efficiency luminous flux is achieved at approximately 40℃ under the conditions of the number of argon filled gas Torr and the number of mercury mmTorr, and the lamp voltage and lamp Current, lamp power, etc. also tend to change with maximum or minimum values around this temperature.

FIG. 3 shows an example of the ambient temperature characteristics actually measured using the lamp shown in FIG. The lamp voltage, lamp current, lamp power, and luminous flux after entering the equilibrium state (stable lighting) were measured by changing the ambient temperature from -10°C to 50°C. Each measurement value when the ambient temperature is 25℃ (room temperature) is expressed as 100%, and Figure 4 shows the temperature at the coldest point of the tube wall (temperature at the top of outer tube 1) and lamp voltage at the time of the above measurement. The relationship is expressed as a rate of change. From the maximum value of the lamp voltage in these two characteristic diagrams, the lamp shown in Figure 1 is a lamp with characteristics such that the temperature of the coldest point on the tube wall is approximately 40°C when the ambient temperature is approximately 0°C. It can be seen that when the lamp is used at a temperature of 25°C, the temperature at the coldest point on the tube wall is approximately 65°C. In this way, in the lamp shown in FIG. 1, the tube wall temperature is higher than that of a normal lamp, so the luminous flux reaches its maximum when the ambient temperature is around 0° C., and the lamp voltage also reaches its maximum around that temperature.

Now, if we consider the case where such a lamp is lit at room temperature (approximately 25 degrees Celsius), the temperature at the coldest point on the tube wall will gradually rise from room temperature, which is the same as the ambient temperature at the time of startup, until it reaches the maximum value of the lamp voltage. Equilibrium occurs after the process.
In other words, Figure 5 shows the actual measured values (measured at an ambient temperature of 25°C).
As shown in , several minutes after startup (the temperature at the coldest point on the tube wall at startup is naturally 25℃), the temperature at the coldest point on the tube wall (approximately 40℃) at which the lamp voltage reaches its maximum is reached; The voltage decreases and reaches equilibrium (the temperature at the coldest point on the tube wall at that time is approximately 65°C as mentioned above). Therefore, when optimal lighting circuit constants are set based on the lighting characteristics at room temperature, flickering or turning off may occur during the process after startup until equilibrium is reached. The reason for this is that when the circuit constants are set as described above, the lamp voltage becomes approximately 120% of the equilibrium value several minutes after starting, and there is a period when the lamp re-ignition voltage is higher than the power supply voltage. This is because when the state higher than the voltage is small, it will flicker (incomplete lighting), and when it is large, it will turn off.

Furthermore, when a lamp like the one described above is lit at a low ambient temperature, for example, when it is lit at an ambient temperature of 0°C, as is clear from Figure 3, even after equilibrium, the lamp voltage remains approximately 120% of that at room temperature. For the above-mentioned reason, there was a possibility that flickering or fading may occur even after equilibration. Conventionally, in such cases, circuit design focused on characteristics at low ambient temperatures.
In practice, it is often used at an ambient temperature around room temperature, and the secondary voltage of the ballast is increased due to temporary high lamp voltage, resulting in larger equipment, increased power loss,
This led to an increase in costs.

(Object of the Invention) The present invention was made in view of the above-mentioned drawbacks, and its purpose is to provide a low-pressure discharge lamp in which the temperature at the coldest point of the tube wall at room temperature is approximately 20°C or more higher than the temperature that provides the highest efficiency luminous flux. To provide a discharge lamp lighting device which prevents flickering and turning-off phenomena that often occur until the lamp reaches an equilibrium state after starting, and improves startability.

(Disclosure of the Invention) Fig. 6 is a circuit diagram showing an embodiment of the present invention, which consists of a series circuit of an auxiliary impedance B' and a switch S in parallel with an impedance B that determines the lighting characteristics at room temperature. is connected, and the switch S is turned off at a temperature equal to or higher than the temperature of the coldest point on the tube wall at which the lamp voltage of the fluorescent lamp FL reaches its maximum (hereinafter referred to as the switching temperature). Vs is a commercial power supply, and G is a glow starter. Incidentally, the auxiliary impedance B' may be constituted by a resistor.

FIG. 7 is a schematic diagram showing an example in which the present invention is applied to a lamp as shown in FIG. 1, using a bimetallic structure as the switch S. In such a case, the switch S is attached to the stem 2 of the lamp, and the lamp is This detects the temperature of the second part of the stem, which has a clear correlation with the temperature of the coldest point on the tube wall. Furthermore, since the stem 2 portion does not contribute to the light emission of the lamp, there is an advantage that the characteristics will not be affected if the search switch S is attached to this portion.

Next, the operation of the above embodiment will be explained. As mentioned above, the switch S is configured to detect a temperature that is correlated with the temperature of the coldest point on the tube wall of the lamp FL, and to turn off at a temperature equal to or higher than the temperature of the coldest point on the tube wall at which the lamp voltage becomes maximum. Therefore, below the switching temperature, switch S turns on and auxiliary impedance B' is connected in parallel to impedance B, so more lamp current flows than when only impedance B is used, resulting in a negative characteristic relationship. The lamp voltage (fluorescent lamps have a negative lamp voltage-lamp current characteristic) decreases. Therefore, as shown in Fig. 5 (indicated by the dotted line in Fig. 8), the fluctuation process of the lamp voltage after starting at room temperature until the lamp reaches equilibrium will have the characteristics as shown by the solid line in Fig. 8. The temporary rise in lamp voltage that occurred in conventional lamps was suppressed, and the accompanying flickering and fading phenomena were eliminated.

In addition, in fluorescent lamps, when the temperature of the lamp is sufficiently cool, the vapor pressure of mercury is low, which makes it difficult to light, especially at low temperatures.One of the factors that determines the ease of starting is the Although the lamp voltage may be sufficiently low compared to the secondary voltage of the ballast, according to the present invention, as described above, the switch S is in the on state immediately after starting when the tube wall temperature is low, so the lamp voltage is low. This also improves the starting performance of the lamp.

(Effects of the Invention) As described above, the present invention provides that the temperature of the coldest point of the tube wall at room temperature is about 20°C lower than the temperature that provides the highest efficiency luminous flux.
In a discharge lamp lighting device that uses a high-pressure discharge lamp as a power source and lights it via a ballast, the ballast is connected in parallel with an impedance that determines the lighting characteristics at room temperature, an auxiliary impedance, and a series circuit of a switch element. In addition, the switch element is turned off at a temperature equal to or higher than the temperature of the coldest point of the tube wall at which the lamp voltage reaches its maximum, so that the lamp is balanced after starting when the lamp is lit at room temperature. The flickering and extinguishing phenomena caused by the temporary increase in lamp voltage that occur during It was possible to achieve a stable and nearly optimal lighting condition, and also to improve startability.

[Brief explanation of the drawing]

Figure 1 is a perspective view of a conventional compact fluorescent lamp, Figure 2 is a perspective view of a conventional compact fluorescent lamp;
The figure is a perspective view of a conventional bending type fluorescent lamp, Figure 3 is a diagram showing an example of the ambient temperature characteristics actually measured with the lamp shown in Figure 1, and Figure 4 is a diagram showing the temperature of the coldest point on the tube wall of the same lamp. Voltage characteristic diagram; Figure 5 is a lamp voltage characteristic diagram with respect to elapsed time after starting the same as above; Figure 6 is a circuit diagram showing an embodiment of the present invention; Figure 7 is an example in which the present invention is applied to a small fluorescent lamp. FIG. 8 is a diagram showing lamp voltage characteristics with respect to elapsed time after starting according to the present invention. FL...Low pressure discharge lamp, Vs...Power supply, B...Impedance, B'...Auxiliary impedance, S...
...Switch.

Claims (1)

[Claims] 1. In a discharge lamp lighting device that is powered by a low-pressure discharge lamp whose tube wall coldest point temperature at room temperature is about 20°C or more higher than the temperature that gives the highest efficiency luminous flux and is lit via a ballast, the ballast is operated at room temperature. An impedance that determines the lighting characteristics of the lamp, an auxiliary impedance, and a series circuit of a switch element are connected in parallel, and the switch element is turned off at a temperature equal to or higher than the temperature of the coldest point on the tube wall at which the lamp voltage is maximum. A discharge lamp lighting device characterized by: