JPH0332201B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fast-phase discharge lamp ballast used in a saturated metal vapor pressure lamp such as a high-pressure sodium lamp.

In general, the lifespan of high-pressure sodium lamps is limited by the wear of the electrodes during normal lighting, or the sodium metal sealed inside the arc tube gradually coming out of the arc tube over a long period of time until the end of its life. It is generally said that this causes the lamp to go out as a result of the lamp voltage gradually rising due to a loss of balance between the lamp voltage and the temperature of the coldest part inside the arc tube. Therefore, it is said that the lifespan of this type of lamp is determined by the increase in lamp voltage.

For this reason, the arc tube of an unused lamp is designed to be filled with extra sodium amalgam in advance in order to alleviate the rise in lamp voltage as much as possible. However, when using such lamps, the lamp is usually covered with a reflective shade or housed in a fixture, which forces the ambient temperature of the lamp to rise, causing the temperature of the coldest part inside the arc tube to drop. The lamp voltage rises, and excess sodium metal inside the arc tube evaporates, resulting in an increase in lamp voltage.The lamp voltage has the property of increasing in proportion to the lamp usage time.

On the other hand, ballasts used in such lamps include slow-phase ballasts and fast-phase ballasts.
First, Figure 1 shows the high-pressure sodium lamp NH360 (lamp rating: lamp power 360W, lamp voltage 130W,
A lamp current of 3.3A) is turned on using a slow-phase ballast, and its lamp voltage-lamp current characteristics ( _L -
_L ) and lamp voltage-lamp power characteristics ( _L-
This slow-phase ballast does not cause the lamp to turn off or flicker, but the input current at startup is large and the fluctuation characteristics of the power supply voltage are large _. be. On the other hand, there are two types of such slow phase ballasts: a single yoke type slow phase ballast and a leaky transformer type slow phase transformer. The properties of these two types are approximately the same. On the other hand, there are two types of phase-advancing ballasts: a single-choke type phase-advancing ballast that combines a single-ch yoke and a capacitor, and a leakage transformer type phase-advancing ballast. Among these, the characteristics of the single-choke type fast-phase ballast are substantially similar to those of the above-mentioned slow-phase ballast, and the leaky transformer type fast-phase ballast exhibits the following characteristics. That is, as shown in FIG. 2, this leakage transformer type phase-advanced ballast has a primary coil 3 and a secondary coil 4 in a central leg 2 surrounded by side legs 1, and a leakage magnetic component is generated between the two coils. A slit 6 is formed in the central leg 2 on the side of the secondary coil 4, and a lamp and a capacitor are connected in series to the secondary coil 4. FIG. 3 shows the lamp voltage-lamp current characteristics and lamp voltage-lamp power characteristics when the high-pressure sodium lamp NH360 is lit. According to this leakage transformer type phase-advanced ballast, It can be said that it is preferable to use a leakage transformer type phase advance type ballast because the input current at the time of starting is small and the fluctuation characteristics of the power supply voltage fluctuate less than the phase slow type ballast. However, as shown in the characteristic diagram, due to the influence of the L-C resonance of the circuit, the lamp current locally increases after a certain lamp voltage value, which causes the lamp ambient temperature to rise. This further promotes the increase in lamp voltage. This synergistic effect causes the lamp to turn off or flicker, resulting in a short lifespan. For this reason, leaky transformer type phase advance type ballasts have not been put to practical use in the past.

The present invention has been made in view of these points, and takes advantage of the advantages of input characteristics and fluctuation characteristics while eliminating lamp extinguishing due to lamp voltage increases.
The object of the present invention is to obtain a phase advance type discharge lamp ballast that can extend the life of the lamp.

The present invention focuses on the difference in characteristics between the slow-phase type and the phase-advanced type, and by making the characteristics of the phase-leading type approach the characteristics of the slow-phase type under predetermined conditions, when the lamp voltage increases, the lamp can be turned on as well as the slow-phase type. The structure is such that the current can be reduced and the increase in lamp power can be suppressed, thereby eliminating the possibility of the lamp going out.

An embodiment of the present invention will be described based on FIGS. 4 to 7. Components that are the same as those shown in FIGS. 1 to 3 are designated by the same reference numerals. First, in this embodiment, whereas in a conventional leaky transformer type phase-advancing ballast, the coupling ratio k between the primary coil 3 and the secondary coil 4 is set to k=0.8.
By appropriately selecting the leakage magnetic shunt 5 and the slit 6, the coupling ratio k was changed to 0.5, 0.55, and 0.6, and the lamp voltage-lamp current characteristics and lamp voltage-lamp current characteristics were measured. , the characteristics shown in FIG. 5 were obtained.
According to this, by reducing the coupling ratio k such as k = 0.5 or 0.55, even if it is a fast phase type, it approaches the characteristics of a slow phase type, the lamp power has the maximum value, and the lamp voltage increases. In this case, the lamp current decreases in the same way as the slow phase type, and the rise in lamp power can be suppressed. Therefore, if the lamp is made close to a slow-phase type through appropriate adjustment, the lamp will not turn off or flicker even if the lamp voltage increases, and its life will not be shortened. Regarding this point, we conducted more detailed measurements and found that, based on the lamp voltage-lamp power characteristics of the slow-phase test ballast (indicated by TB in Figure 5), the characteristics of the slow-phase test ballast (indicated by TB in Figure 5) If the maximum lamp voltage is set to a lamp voltage within 130% of the lamp voltage that gives the maximum lamp power, it is possible to practically eliminate fading and flickering without any problem. On the other hand, looking at this from the perspective of the coupling rate k, k = 0.35~
Good results were obtained when the value was within the range of 0.55.

The reason why such a slow-phase test ballast is used as a standard is that various standards specify the characteristics of this slow-phase test ballast, and using this as a standard makes it easier to understand the various characteristics. It is.

By the way, in order to make the coupling ratio k smaller than that of the conventional leaky transformer type phase advance type ballast,
Enlarging the slit 6 and reducing the leakage magnetic shunt 5
There are two elements to increasing the cross-sectional area of .
Therefore, one or both of them may be adjusted. However, if the slit 6 is simply made larger, the lamp current waveform at startup becomes worse as shown in Figure 6 (actually measured waveform), and the lamp life tends to be shortened. It can be said that there is a limit to how small it can be made. Therefore, if the coupling ratio k is decreased by increasing the cross section of the other element, the leakage magnetic shunt 5,
The lamp current waveform at startup can be improved as shown in FIG. 7 (actually measured waveform). in particular,
Good results were obtained when the cross section of the leakage magnetic shunt 5 was made equal to or larger than the cross section of the side leg 1.

As described above, even if the ballast is of a leaky transformer type, the maximum lamp power can be obtained at a lamp voltage within 130% of the lamp voltage that gives the maximum value of the lamp power in the characteristics of the lagging phase test ballast. Because it has close to a slow phase characteristic, it takes advantage of the advantages of a leaky transformer type phase advance type ballast in that the input current at startup is small and the power supply voltage fluctuates little, but even when the lamp voltage increases. By reducing the lamp current, it is possible to suppress the increase in lamp power, so that the lamp does not go out and its life can be extended.

[Brief explanation of the drawing]

Fig. 1 is a characteristic diagram of a slow-phase ballast, Fig. 2 is a side view showing a conventional leakage transformer type fast-phase ballast,
Fig. 3 is its characteristic diagram, Fig. 4 is a side view showing an embodiment of the present invention, Fig. 5 is its characteristic diagram, and Figs. 6 and 7 are lamp current waveform diagrams at startup determined by actual measurements. It is. 3...Primary coil, 4...Secondary coil, 5...Leakage magnetic shunt, 6...Slit.

Claims (1)

[Claims] 1. A leakage transformer comprising a primary coil and a secondary coil, a leakage magnetic shunt between the primary coil and the secondary coil, and a slit in the iron core on the side of the secondary coil. In a phase-advancing discharge lamp ballast in which a metal vapor pressure lamp and a capacitor are connected in series, the primary coil can be improved by increasing the size of the slit, increasing the cross-sectional area of the leakage magnetic shunt, or both. The coupling ratio between the saturated metal vapor pressure type lamp and the secondary coil is adjusted to suppress the increase in lamp power even if the lamp voltage increases, and the lamp voltage at the maximum power of the saturated metal vapor pressure type lamp is stabilized for the slow phase type test. A phase-advancing discharge lamp ballast characterized in that the lamp power in the lamp characteristics is within 130% of the maximum lamp voltage.