JPS602757B2 - discharge lamp lighting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a discharge lamp lighting device, and its purpose is to provide a discharge lamp lighting device that is small and lightweight, has excellent electrical characteristics, and can reliably light a discharge lamp. It is in.

FIG. 1 shows an example of a circuit of a discharge lamp lighting device which is the basis of the present invention.
A first closed circuit is formed by connecting a discharge lamp 4 through a current limiting element consisting of a series connection of a main capacitor 2 and a main capacitor 2;
A switching element 8 is connected to the non-power terminal of both filament electrodes 5, 5 of the discharge lamp 4, and a current limiting element, AC power source 3,
A second closed circuit including a switching element 8 is formed, and the switching element 8 is closed at a constant phase in the latter half of each half cycle of the AC power supply 3 at least when the discharge lamp 4 is lit. .

In such a circuit, when the AC power supply 3 is turned on, the switching element 8 closes as shown in FIG. A current ls as shown in FIG.
flows and sufficiently heats the filament electrodes 5, 5, and the main capacitor 2 is efficiently charged due to the strong vibration action between the inductance element 1 and the filament electrodes 5, 5, and the electric charge is accumulated, resulting in a state as shown in Fig. 2. Indicates high terminal voltage Vc.

Next, when the phase switching element 8 is opened, the main capacitor 2, which has been charged to a high voltage Vc, does not lose its discharge circuit, and the charging and tumultuous pressure Vc and the power supply voltage V are superimposed on this high voltage, as shown in FIG. A rectangular wave voltage is applied to the discharge lamp 4.
When a capacitor 4 is connected in parallel to the switching element 8 in the circuit shown in Figure 1, due to the transient oscillating current immediately after the switching element 8 is opened, the voltage waveform shown in Figure 2 is applied to both ends of the discharge lamp 4. Furthermore, an oscillating voltage can be added to apply a voltage with a higher peak value. In this way, the discharge lamp 4 can be started quickly by alternately applying heat to the filament and applying high voltage. The discharge lamp lighting device on which the present invention is based operates as described above,
Due to the circuit operation described above, there is a close relationship between the thermal current and the voltage applied to the lamp. For example, when the firing angle 8 of the switching element 8 shown in FIG. 2A is increased, the thermal current increases and the voltage applied to the discharge lamp also increases. FLR40, FLRII
When conducting experiments using a discharge lamp such as a dish, the voltage applied to the discharge lamp was rather low when an appropriate preheating current was applied, and it was found that starting the discharge lamp was uncertain at low and high temperatures. Furthermore, there is a problem in that if the applied voltage is set appropriately, the child thermal current becomes too large. Flowing an excessive heating current to ensure starting lighting not only shortens the life of the discharge lamp, but also requires increasing the rated current capacity of the switching element 8. Further, when the current increases, magnetic saturation of the iron core of the inductance element 1 occurs, and the preheating current increases rapidly when the voltage of the AC power source 4 exceeds the rated value. Therefore, in order to suppress this, the capacity of the inductance element must be increased, resulting in a large and expensive device. As mentioned above, there is also a method of connecting a capacitor in parallel to the switching element 8 to superimpose an oscillating voltage on the voltage of the tree shown in FIG. 2. Although this circuit is effective to some extent, its effectiveness is limited and When the switching element 8 is opened in the upper phase direction, the charge of the parallel capacitor is suddenly discharged through the switching element 8, which increases the load on the switching element 8. The present invention has been proposed in view of the above-mentioned drawbacks, and will be described in detail below with reference to an embodiment circuit shown in FIG.

The embodiment of FIG. 3 is constructed by connecting a parallel circuit of a capacitor 6 and a diode 7 of relatively large capacity in series with the switching element 8 in the basic circuit of FIG. When the AC power supply 3 is turned on and the switching element 8 performs the same switching operation as in the circuit of FIG. 1, the forward current of the diode 7 flows through the diode 7, and the reverse current flows through the capacitor 6. A DC voltage of the polarity shown appears in the parallel circuit of capacitor 6 and diode 7. This DC voltage also appears on the main capacitor 2 with the polarity shown. As a result, a waveform as shown in FIG. 4 is added to both ends of the discharge lamp 4, which is the water waveform in FIG. 2 plus a DC component. In this way, although only in one direction, the peak value of the voltage applied to the lamp increases, so that the discharge lamp 4 can be reliably started without increasing the preheating current more than necessary. In addition, capacitor 6,
By inserting the parallel circuit of the diode 7, the capacitance in the circuit decreases and the current increases slightly, but this can be restored by adjusting the firing angle 8 of the switching element 8, and by increasing the capacitance of the capacitor 6. , which can be ignored in practice.
Furthermore, as described in the circuit of FIG. 1, it is also possible to connect a small capacitor in parallel with the discharge lamp 4 or the switching element 8 to superimpose an oscillating voltage on the waveform of FIG. 4. Further, as is clear from the circuit configuration in FIG. 3, since the capacitor 6 is short-circuited in one direction by the diode 7, a DC capacitor such as an electrolytic capacitor can be used.
The present invention connects one end of both filament electrodes of a discharge lamp to both ends of an AC power supply through a series circuit of an inductance element and a main capacitor, and connects a parallel circuit of a capacitor and a diode, and a series circuit of a switching element. It is connected between the non-power side ends of the filaments on both sides of the lamp, and the switching element is closed in the latter half of each half cycle of the power supply voltage at least at the time of starting, so that the rectangular wave height obtained by opening and closing the switching element is A DC voltage component can be superimposed on the voltage, and the discharge lamp can be started reliably with the high voltage, and the discharge lamp can be started at a low power supply voltage, and the power supply voltage is approximately at or below the discharge sustaining voltage of the discharge lamp. The discharge lamp is started and turned on, and even after lighting, the switching element continues to switch, and for a certain period of time during each half cycle of the power supply, the discharge lamp is short-circuited to increase the charging pressure of the main capacitor, and in the next half cycle, the main capacitor is charged. If the stored charge and the power supply voltage are superimposed and added to the discharge lamp, and used as a method to ensure the re-ignition of the discharge lamp, the starting effect becomes even more reliable. Even if it is applied to a non-preheating type discharge lamp or a non-preheating type discharge lamp, it is possible to reduce the current of the switching element, make the inductance element smaller, and reduce the cost.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a basic example of a discharge lamp lighting device that is the basis of the present invention, FIG. 4 is an explanatory diagram of the operation of the circuit shown in FIG. 3, where 1 is an inductance element, 2 is a main capacitor, 3 is an AC power supply, 4 is a discharge lamp, 5 is a filament electrode, 6 is a capacitor, 7 is a diode,
8 is a switching element. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. Connect one end of each filament electrode on both sides of the discharge lamp to both ends of the AC power supply through a series circuit of an inductance element and a main capacitor, and connect a parallel circuit of a capacitor and a diode and a series circuit of a switching element to both sides of the discharge lamp. 1. A discharge lamp lighting device, characterized in that the switching element is connected between the non-power supply side ends of the filament and closes in the latter half of each half cycle of the power supply voltage at least at the time of starting.