JPH06275391A - Lighting method for metal halide lamp and device thereof - Google Patents

Abstract

PURPOSE:To stably light the whole kind or quality of a methal halide lamp by one kind light and simple ballast by superimposing low-frequency AC components on high-frequency lighting current to make the amplitude modulation ratio of the current waveform of high-frequency lamp current to be applied between lamp electrodes 40% or more. CONSTITUTION:High voltage is applied to a metal halide lamp 1 by charging/ discharging a starting capacitor C2 to light a lamp 1. The high voltage is stopped after lighting to feed prescribed electric power to the lamp 1 by the resonance circuit of a reactor L and a capacitor C1. Concurrently with lightning, a half bridge invertor 2 repeats ON/OFF alternately to the oscillation frequency of the oscillation circuit 4 to convert a current direction by a high frequency to flow current to the lamp 1. Low-frequency A.C. components are superimposed on D.C. by a modulation circuit 5 inserted in series in D.C. to amplitude- modulate lamp current, and its modulation ratio is made 40% or more. Consequently lighting can be stably made nevertheless the dispersion of the kind or quality of a metal halide lamp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel lighting device for a metal halide lamp.

[0002]

2. Description of the Related Art Conventionally, as a method for lighting a metal halide lamp, there are a low frequency lighting method mainly using an iron core ballast and a comparatively new high frequency FM modulation method developed thereafter.

A low frequency lighting method using an iron core ballast will be briefly described. The low frequency lighting method is a method of lighting a metal halide lamp at a frequency of 5 kHz or less, and a commercial frequency of 50 to 60 Hz is generally used. Such low frequency lighting can stably light the metal halide lamp, but firstly, the weight and volume of the iron core ballast are very large, and the circuit is complicated, which is a major factor of cost increase. It is difficult to replace the usage of incandescent bulbs that are used, and there is a limit to the installation posture that the metal halide lamp must be installed horizontally for low frequency lighting.In addition, the metal halide lamp is installed horizontally. As a result, the lighting beam formed between the electrodes curves upward, and the temperature at the top of the light-emitting part is high and the temperature at the bottom is low, which tends to cause uneven temperature distribution. There is also a drawback that it will contact the vessel and damage the envelope,
There were issues such as weight reduction of ballast, cost reduction by simplification, and straightness of beam.

In order to meet such demand, a high frequency FM modulation system has been proposed. High-frequency lighting of metal halide lamps (for example, 5 kHz to 200 kHz)
Then, the straightness of the beam can be secured, and the weight of the ballast and the circuit can be simplified. However, when lighting in such a high frequency region, a phenomenon in which the beam fluctuates or disappears due to an acoustic resonance phenomenon peculiar to a metal halide lamp frequently occurs. Such a phenomenon does not occur in all the high frequency regions, and stable lighting is possible in the frequency region of an extremely narrow range. Such a frequency range is called a “frequency window”, but this “frequency window” is slightly different due to fluctuations in the ambient temperature of the ballast and variations in the characteristics of each ballast. It could not be said that the lighting could be performed stably.

As a typical example of the high frequency FM modulation system,
A method in which a modulation frequency of 100 to 120 Hz is superimposed on a lighting frequency of 22.5 kHz and modulation is performed within a range of 22.5 kHz ± 2.5 kHz is actually proposed. According to this method, the effect of expanding the "frequency window" was recognized, and the metal halide lamp could be lit more stably in the high frequency region.

However, the metal halide lamps are very difficult to manufacture and the quality thereof varies greatly, and not all the same kind metal halide lamps have a "frequency window" in the same frequency region. Therefore, when the same non-defective metal halide lamp is replaced to replace the burned metal halide lamp, it may rarely turn on. Also, additives (iodide) in the envelope
The "frequency window" varies significantly depending on the type of the metal halide lamp, and even with the high frequency FM modulation method, there is a type of metal halide lamp that does not light at all with one type of ballast, and there is a ballast that can handle all metal halide lamps with one type of ballast. There wasn't. In a high frequency region of 200 kHz or more, noise is extremely large and an interference radio wave is emitted to the surroundings, so that it cannot be used.

[0007]

As can be seen from the above description, the expansion of applications of metal halide lamps can be stably lit without being affected by variations in the quality of the ballast or the metal halide lamps. It is possible to reduce the size and weight of the ballast, and to use one type of ballast for all metal halide lamps. The present invention has been made to solve the above problems,
An object of the invention is to overcome the above problems by superimposing a low frequency component on a high frequency lighting current.

[0008]

According to the method of the present invention, the amplitude modulation rate of the current waveform of the high frequency lamp current applied between the lamp electrodes is 40% or more by superimposing the low frequency AC component on the high frequency lighting current. It is characterized by that. According to this, all the metal halide lamps (1) and their quality variations can be overcome by the low-frequency AC component, and stable lighting can be achieved.

According to claim 2, "a half-bridge inverter (2) for converting the direction of the current applied to the metal halide lamp (1) at a high frequency, and a drive circuit (3) for driving the inverter (2). ) And an oscillating circuit (4) that regulates the switching frequency of the inverter (2), in a metal halide lamp lighting device (A), a modulation circuit (5) that superimposes a low-frequency AC component on a DC current is It is connected in series to the bridge inverter (2) ”. According to this, not only can the metal halide lamp (A) be stably controlled by the low-frequency AC component, but also the circuit can be downsized and simplified.

[0010]

The present invention will be described in detail below with reference to the illustrated embodiments, but the present invention is not limited thereto. FIG. 1 is a circuit diagram of an embodiment of the circuit of the present invention, which mainly comprises a DC power supply (6), a modulation circuit (5), a drive circuit (3), an oscillation circuit (4) and the like. The drive circuit (3) has a switching element (Tr
1) Half bridge inverter with (Tr2) connected in series
(2) is installed and the drive circuit (3)
The inverter (2) is on / off controlled. The starting capacitor (C2) and the metal halide lamp (1) are connected in parallel, one end of the reactor (L) is the connection point of the switching elements (Tr1) (Tr2), and the other end is the metal halide lamp (1). Each is connected to one connection end of the starting resonance capacitor (C2).

One of the switching elements for the inverter (2) is connected to the other connecting end of the metal halide lamp (1) and the starting resonance capacitor (C2) via the capacitor (C1).
It is connected to (Tr2). Also, DC power supply (6), modulation circuit
(5) and the inverter (2) are connected in series. The DC power supply (6) is generally one that rectifies commercial current into DC.

The oscillation circuit (4) is connected to the drive circuit (3), and the oscillation circuit (4) oscillates an oscillation frequency set in accordance with the "frequency window". In this embodiment, 22
Although kHz (or 15 kHz or the like) is selected, it is of course not limited to this.

The modulation circuit (5) is, for example, a known circuit in which a rectifier (5a), a chopper (5b) and a smoothing coil (5c) are connected in series, and a low frequency AC component is superimposed on an input DC current. To do. In this embodiment, 100 or 120
The low frequency AC component of Hz shall be superimposed. The method of superposition is not particularly limited, but one method is to use a DC power supply.
When AC is converted to DC in (6) and used, the capacity of smoothing capacitors (C3) (C4) inserted in parallel with a pair of rectifier diodes (D1) (D2) as shown in Fig. 3 should be reduced. By
A low frequency AC ripple may be superimposed on the rectified DC, or a low frequency AC ripple may be superimposed on the DC through a transformer (H) as shown in FIG.

The metal halide lamp (1) is lit using the circuit of FIG. 1 configured as described above. First, a high voltage is applied to the metal halide lamp (1) by charging and discharging the starting capacitor (C2). ) Is applied to light the metal halide lamp (1). After lighting, the high voltage is stopped and the specified power is supplied to the lamp (1) by the resonance circuit of the reactor (L) and the capacitor (C1). At the same time as lighting, the half bridge inverter (2) repeats on and off alternately according to the oscillation frequency of the oscillation circuit (4),
The current is passed through the metal halide lamp (1) while converting the direction of the current at the high frequency. Here, since the low frequency AC component is superimposed on the DC current by the modulation circuit (5) inserted in series with the DC current, amplitude modulation occurs in the lamp current as shown in FIG. However, since the modulation circuit (5) only superimposes the low-frequency AC component on the DC current, the frequency is the oscillation frequency output from the oscillation circuit (4) as it is, and the frequency itself is not modulated. In other words, the frequency of the lamp current is constant and the amplitude change is large. Amplitude modulation rate is expressed by the following formula, the value obtained by subtracting the minimum amplitude (B) from the maximum amplitude (A) of the lamp current, the value obtained by adding the minimum amplitude (B) to the maximum amplitude (A) of the lamp current. And the value obtained by multiplying by 100 is 40% or more. The amplitude modulation rate = (A−B) ÷ (A + B) × 100.

As described in the conventional example, the low-frequency lighting can be stably lit regardless of the type of metal halide lamp and the variation in its quality. However, since the ballast is large and heavy, there is a fatal defect that practical applications are limited. However, according to the method of the present invention, since the low-frequency AC component is superposed on the high-frequency current, the low-frequency AC component is lit stably regardless of the type of all metal halide lamps (1) and quality variations. It has the effect of being able to do things. On the other hand, the circuit configuration is basically high-frequency lighting, so it is simple, does not require a heavy transformer, and can be made lightweight.

[0016]

According to the present invention, by superimposing a low-frequency AC component on a high-frequency lighting current of a constant frequency, the amplitude modulation rate of the current waveform of the high-frequency lamp current applied between the lamp electrodes is 40% or more. As a result, the low-frequency AC component of the high-frequency lighting current has the effect of enabling stable lighting regardless of the types of all metal halide lamps and variations in quality, while the circuit configuration is Basically it is high frequency lighting, so it's easy,
It does not require a heavy transformer and can be made lighter, and one kind of lightweight and simplified ballast enables stable lighting of metal halide lamps regardless of variations of all kinds or quality. I was able to do it.

Further, the circuit structure is simple in that a modulation circuit for superimposing a low frequency AC component on a DC current is connected in series to a half bridge inverter, and the ballast can be made simple and lightweight.

[Brief description of drawings]

FIG. 1 is a ballast circuit diagram of one embodiment of the present invention.

FIG. 2 is a lamp current waveform diagram of the present invention.

FIG. 3 is an exemplary diagram of an amplitude modulation circuit that superimposes a low-frequency AC ripple according to the present invention.

FIG. 4 is another exemplary diagram of an amplitude modulation circuit that superimposes a low-frequency AC ripple according to the present invention.

[Explanation of symbols] (A) ... Metal halide lamp lighting device (1) ... Metal halide lamp (2) ... Half bridge inverter (3) ... Drive circuit (4) ... Oscillation circuit (5) ... Modulation circuit

Claims (2)

[Claims] 1. A method of superimposing a low-frequency alternating current component on a high-frequency lighting current having a constant frequency so that the amplitude modulation rate of the current waveform of the high-frequency lamp current applied between the lamp electrodes is 40% or more. How to turn on the characteristic metal halide lamp. 2. A metal halide comprising a half bridge inverter for converting the direction of the current applied to the metal halide lamp at a high frequency, a drive circuit for driving the inverter, and an oscillator circuit for defining the switching frequency of the inverter. In the lamp lighting device, a metal halide lamp lighting device characterized in that a modulation circuit for superimposing a low-frequency AC component on a DC current is connected in series to a half-bridge inverter.