JPH04129196A - Metal halide lamp lighting device - Google Patents

Abstract

PURPOSE:To greatly lengthen the life by installing a series resonance circuit set such that resonance a frequency becomes equal to the output frequency of an inverter and connecting a metal halide lamp in parallel to the capacitor. CONSTITUTION:In an inverter 8 is driven to light up a metal halide lamp 9, the impedance (r) of the metal halide lamp 9 connected to a capacitor 8b in parallel is infinite under the condition before lighting and has no effect on a resonance phenomenon, so that series resonance phenomenon takes place in a series resonance circuit 8. In a perfect resonance condition, the terminal voltage of this capacitor 8b becomes a high voltage, and this high voltage is applied as a discharge start voltage to the lamp 9. When the lamp 9 starts discharge with application of this high voltage, the impedance (r) of this lamp 9 decreases rapidly, so that series resonance stops. Thereafter, the temperature of lighting tube rises up, and resultantly, the impedance (r) becomes large and is kept at a fixed stable and as a result, the tube voltage of the lamp 9 is stabilized, too.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a lighting device for a metal halide lamp, which is a type of mercury lamp.

<Prior art> Such metal halide lamps are structurally similar to other mercury lamps, or have various metal halides in addition to mercury and argon sealed in the arc tube as light-emitting substances. It emits light unique to metals and has excellent light color and color rendering properties that are close to sunlight, so it is widely used in various lighting devices.

On the other hand, the discharge starting voltage during lighting is considerably higher than that of general mercury lamps, so in the past, special ballasts were used,
An igniter is built into the arc tube so that high voltage is obtained only when starting the lighting.

<Problem to be solved by the invention> However, the device using a dedicated ballast is heavy and large;
On the other hand, if the igniter is built-in, it not only increases the cost considerably, but also has the disadvantage of having a very short lifespan.

The present invention has been made in view of these conventional problems, and a technical object thereof is to provide a metal halide lamp lighting device that is inexpensive, lightweight, and has a sufficient lifespan.

Means for Solving the Problems> In the present invention, as a technical means for achieving the above-mentioned problems, a metal halide lamp lighting device is configured as follows. That is, it consists of an inverter that supplies high-frequency output to the metal halide lamp, and a reactor and a capacitor connected in series between the high-frequency output terminals of this inverter.
It is characterized by comprising a series resonant circuit whose resonant frequency is set to be equal to the output frequency of the inverter, and a metal halide lamp connected in parallel to the capacitor.

<Function> When high-frequency power is output from the inverter when lighting a metal halide lamp, series resonance occurs in the series resonant circuit due to this high-frequency output, and the combined impedance at this time becomes extremely small, causing a high voltage generated across the capacitor. The voltage is applied to the metal halide lamp as the discharge starting voltage. When the metal halide lamp starts discharging and lights up due to the application of this high voltage, the impedance of the arc tube of the metal halide lamp decreases rapidly, and since this metal halide lamp is connected in parallel to the capacitor of the series resonant circuit, the series resonant circuit series resonance stops, the combined impedance of the series resonant circuit increases, and the voltage supplied to the metal halide lamp drops to a level that can maintain discharge.

This metal halide lamp lighting device uses a high frequency inverter as a ballast and has an LC series resonant circuit connected to it.Moreover, since the series resonant circuit resonates at the high frequency of the inverter, a reactor with small inductance and capacitance is used. and capacitors can be used, and it can be constructed at low cost, and
It is much lighter than those that use a dedicated ballast, and since it is not built into the arc tube, it can maintain a sufficient lifespan.

<Example> Hereinafter, a preferred example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a block configuration of an embodiment of the present invention, in which a DC power supply section 1 includes, for example, a commercial AC power source that steps down or steps up the voltage in a power transformer, performs full-wave rectification, and further smoothes it into DC power. This DC power is then supplied to a push-pull type or bridge type inverter 7.

The current setting block 2 connects the DC power supply section 1 to the inverter 7.
Outputs a current setting value signal that is inversely proportional to the DC voltage supplied to the

The current control block 3 detects the output current of the DC power supply section 1 with the current detection section 4 and converts the input detected current so that it matches the current setting value signal of the current setting block 2.

When the current signal that is inversely proportional to the DC voltage output from the current control block 3 is amplified by the pulse width modulation circuit 5 and modulated into a pulse width, for example, the output DC voltage of the DC power supply section 1 changes to become higher. The pulse width becomes smaller accordingly. A drive circuit 6 drives and controls an inverter 7 using the output of the pulse width modulation circuit 5 as a control signal,
The metal halide lamp 9 is turned on by the high frequency output of the inverter 7. Here, since the current supplied to the inverter 7 created by the current setting block 2 and the current control block 3 is exactly inversely proportional to the DC voltage supplied to the inverter 7, as a result, the power supplied to the inverter 7 is It is always constant regardless of fluctuations in the DC voltage, and the power supplied from the inverter 7 to the metal halide lamp 9 is also always constant after lighting has stabilized, so that the light color does not change due to fluctuations in the DC voltage.

As a feature of the present invention, a series resonant circuit 8 in which a reactor 8a and a capacitor 8b are connected in series is provided between the high frequency output terminals of the inverter 7, and a metal halide lamp 9 is connected in parallel to the capacitor 8b. . Furthermore, the resonant frequency of the series resonant circuit 8 is the same as that of the inverter 7.
is set equal to the output frequency of In reality, the ability of the inverter 7 is limited, so it cannot be made to resonate completely at its fundamental frequency. Therefore, since the output waveform of the inverter 7 is a square wave, it is caused to resonate with the third harmonic or the fifth harmonic. In any case, since the output of the inverter 7 is a high frequency, series resonance can be easily caused by using reactor 8a and capacitor 8b that have small inductance and capacitance C, respectively. Note that R in the figure represents a resistance included in the reactor 8A, and r represents the impedance (resistance) of the metal halide lamp 9.

When the inverter 8 is driven by the operation described above when lighting the metal halide lamp 9, the capacitor 8b
The impedance r of the metal halide lamp 9 connected in parallel with the lamp 9 is infinite before lighting and has no influence on the resonance phenomenon, so a series resonance phenomenon occurs in the series resonance circuit 8. Combined impedance Z at this time
In a completely resonant state, ω2LC=1 from ωL=1/ωC, so 1−ω2LC=0, and the previous equation becomes Z=R. At this time, the current I flowing through the series resonant circuit 8 is l =
V/R, and the terminal voltage of reactor 8a is (jωL
) I, and the terminal voltage Vc of the capacitor 8b is I/jωC
becomes. Terminal voltage V of this capacitor 8b. As shown in FIG. 2, the phase is delayed by 90 degrees with respect to the output voltage V of the inverter 9 and becomes a high voltage of about 500 to 2000 V, and this high voltage is applied to the metal halide lamp 9 as a discharge starting voltage.

When the metal halide lamp 9 starts discharging due to the application of this high voltage, the impedance r of the lamp 9 rapidly decreases and series resonance stops. The combined impedance Z at this time is as follows. Since jωCr<1, the above equation can be regarded as z=r + R + jωL. The tube voltage of the metal halide lamp 9 at this time is shown by vector OA in FIG. Thereafter, as the temperature of the arc tube rises, the impedance r increases and is maintained at a constant stable value, and accordingly, the tube voltage of the metal halide lamp 9 also changes as a vector along the circumferential locus shown in FIG. It is stable at about 80 to 130V as indicated by OB.

After this lighting, the high frequency inverter 7, which functions as a ballast, lights the light with high luminous efficiency, and the inductance of the reactor 8a functions to suppress the current peak value of the pulse width modulation waveform of the inverter 7.

<Effects of the Invention> As described above, according to the metal halide lamp lighting device of the present invention, a high-frequency inverter is used as a power supply source, and a series resonant circuit is provided at the high-frequency output terminal of this inverter, so that the metal halide lamp lighting device of the present invention has a configuration in which a series resonant circuit is provided at the high-frequency output terminal of the inverter. The structure is extremely simple, and a high voltage can be generated using the series resonance phenomenon, and the series resonance can be stopped due to the decrease in the impedance of the lamp due to discharge, and a steady voltage can be supplied from the inverter after lighting. It can be produced at a low cost, is much lighter than one using a dedicated ballast, and has a much longer lifespan than one with a built-in igniter, providing extremely significant practical effects.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a vector diagram showing the voltage supplied to the lamp. 7... Inverter 8... Series resonant circuit 8a... Reactor 8b... Capacitor 9... Metal halide lamp

Claims (1)

[Claims] (1) A series resonant circuit consisting of an inverter that supplies high-frequency output to a metal halide lamp, a reactor and a capacitor connected in series between the high-frequency output terminals of this inverter, and whose resonant frequency is set to be equal to the output frequency of the inverter. 1. A metal halide lamp lighting device comprising: a metal halide lamp connected in parallel to the capacitor.