JP2001093694A - Discharge lamp lighting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp lighting apparatus capable of giving a sufficient preheating current to the filament, when the lamp is off, and capable of completely turning off the lamp without a tube end of the discharge lamp glowing during the stand-by time. SOLUTION: This discharge lamp lighting apparatus comprises a DC power supply, an inverter circuit for inverting the output of the DC power supply to high-frequency power, a resonance circuit connected to the output of the inverter circuit, a discharge lamp driven by the resonance of the resonance circuit, an inverter control circuit for varying the output of the inverter circuit, and a modulated light control circuit for light modulation control and on/off control of the discharge lamp by inputting a light modulation signal from the outside. When the discharge lamp is off, at least two levels of pre-heating currents are fed to the filament of the discharge lamp switched with a prescribed cycle. A first period Tb, when the level of the pre-heating current If, is set high and a second period Ta, when the level of the pre-heating current is set low, are switched alternately, and the first period Tb is set sufficiently shorter than a second period Ta.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device in which a discharge lamp can be dimmed by an inverter circuit.

[0002]

2. Description of the Related Art FIG. 5 is a circuit diagram of a conventional discharge lamp lighting device. An inverter circuit 1 is connected between the positive and negative poles of the DC power source E.
Are connected to a series circuit of a pair of switching elements Q1 and Q2. The discharge lamp 2 is connected to one switching element Q2 via a resonance inductor L and a coupling capacitor Co. A resonance capacitor C is connected in parallel between the non-power supply terminals of the filament of the discharge lamp 2. The inductor L and the capacitor C form a series resonance circuit. The capacitor C also serves as a preheating current supply path for the discharge lamp 2. Switching elements Q1, Q2
Are alternately turned on and off by the output of the inverter control circuit 3. A dimming control circuit 4 is connected to the inverter control circuit 3, and the dimming signal from the outside makes it possible to control turning off / on of the discharge lamp 2 and dimming control. Thus, the discharge lamp lighting device of FIG. 5 functions as a dimming stabilizer. Here, the dimming signal from the outside is generally a DC voltage or an on-duty variable PW
The M signal is used. Hereinafter, the dimming signal will be described as an on-duty variable PWM signal.

FIG. 6 shows an example of the relationship between the dimming signal and the light output of the discharge lamp 2. When the on-duty of the dimming signal is detected to be 95% or more, the discharge lamp 2
Is turned off. It is well known that the oscillation of the inverter circuit 1 may be stopped in order to turn off the discharge lamp 2. Alternatively, a circuit for shutting off the power supply E may be provided, but in this case, a large-capacity switching element is required. When the discharge lamp 2 is turned off by stopping the oscillation of the inverter circuit 1 or turning off the power supply E, when starting the discharge lamp 2 from the turned-off state, a high voltage necessary for starting is used so as not to impair the life of the filament. Before applying the voltage between both ends of the discharge lamp 2, it is necessary to give a sufficient preheating current to the filament. The preheating current at this time is hereinafter referred to as “preceding preheating”.

[0004] FIG. 7 shows a state in which the light-off state is started through a pre-heating operation.
3 shows a voltage waveform applied between both ends of a discharge lamp when lighting. Since the pre-heating time of the filament is generally required to be 1 to 2 seconds, a longer time is required from the light-off state to the light-on state, and the filament does not follow the operation speed of the light control signal. For example, consider a case where the on-duty is reduced from 100% at a speed of 20% / sec in a dimming ballast having dimming characteristics as shown in FIG. When the on-duty = 95% is detected and the pre-heating time has elapsed by 1 second, the on-duty has already been 75%. Here, even if the starting voltage is applied and the discharge lamp is turned on instantaneously, the discharge lamp is turned on rapidly in a high output state (point M), so that a sense of discomfort is felt.

[0005] In order to solve this problem, as means for turning off the discharge lamp, the oscillation frequency of the inverter circuit is made higher or the DC voltage supplied to the inverter circuit is reduced, so that the discharge lamp is not turned on. A method of continuously supplying a preheating current to the filament was adopted. The preheating current at this time is hereinafter referred to as “standby preheating”. This eliminates the need for advance preheating at the time of startup, and enables immediate lighting.

However, when a sufficient current is constantly supplied to the filament, as shown in FIG. 9, the stray capacitance Cs between the reflector 5 of the lighting equipment and the discharge lamp 2 causes a path indicated by a broken line. There is a problem that current flows and the tube end of the discharge lamp 2 slightly shines.

As described above, when the oscillation of the inverter circuit 1 is completely stopped to completely turn off the discharge lamp 2,
The followability to the operation of the dimming signal is deteriorated, and if the standby preheating current is continuously supplied to the discharge lamp 2 in order to improve the followability, a problem that the tube end of the discharge lamp 2 shines occurs.

The present invention has been made in view of the above points, and aims to provide a sufficient standby preheating current to the filament when the lamp is turned off, and to illuminate the end of the discharge lamp during the standby. It is an object of the present invention to provide a discharge lamp lighting device that can be completely turned off.

[0009]

In order to solve the above-mentioned problems, in a discharge lamp lighting device according to the present invention, as shown in FIG. An inverter circuit 1 for converting power, a resonance circuit connected to the output of the inverter circuit 1, a discharge lamp 2 driven by the resonance action of the resonance circuit, and an inverter control circuit 3 for making the output of the inverter circuit 1 variable. And a dimming control circuit 4 for inputting a dimming signal from the outside and performing dimming control and extinguishing / lighting control of the discharge lamp 2 in a discharge lamp lighting device. As means for giving a standby preheating current), as shown in FIG. 1, at least two levels of preheating current are switched and supplied to the filament of the discharge lamp 2 at a predetermined cycle.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram for explaining the operation of the first embodiment of the present invention. In the present embodiment, in a discharge lamp lighting device having a circuit configuration as shown in FIG. 5, as a means for supplying a preheating current, the oscillation frequency of the inverter circuit at the time of normal lighting is sufficiently higher than a level at which the discharge lamp 2 cannot maintain discharge. To operate the inverter circuit 1. In order to stop the supply of the preheating current, the oscillation of the inverter circuit 1 is stopped. That is, the inverter circuit 1 is operated intermittently,
A standby preheating current as shown in FIG. 1 is supplied to the discharge lamp 2 which is turned off.

In FIG. 1, the discharge lamp 2 does not light during the period Ta because the inverter circuit 1 has stopped oscillating. Of course, the current shown by the broken line in FIG. 9 does not naturally flow, so that the tube end of the discharge lamp 2 does not shine.
Next, during the period Tb in FIG. At this time, a current may flow through a path shown by a broken line in FIG. 9. However, if the period of Tb is made sufficiently shorter than the period of Ta, the tube end of the discharge lamp 2 becomes as shown in FIG. Light emission requires a certain rise time, and the human eye has an afterimage characteristic, so that it is possible to make the light level at which the light from the tube end of the discharge lamp 2 can hardly be visually recognized. . On the other hand, under the condition as shown in FIG.
The time when the tube end of the discharge lamp 2 is shining is long, and the light of the tube end of the discharge lamp 2 is visually sensed by the afterimage characteristics of the eyes. As described above, it is desirable that the time of Tb is approximately １ ／ or less of the time of Ta from the viewpoint of the afterimage characteristics of the eyes.

In order to start the discharge lamp 2 instantaneously without preheating from the light-off state, it is necessary to preheat the filament of the discharge lamp 2 which is turned off, as described above. No need to continue. It suffices if the filament temperature can be kept above a certain level. That is,
Even if the preheating current is given as shown in FIG.
And the magnitude of the preheating current If are appropriately set, and T
It suffices to minimize the decrease in the filament temperature during the period a so that the filament temperature can be maintained at a certain level or higher.

In the embodiment shown in FIG. 1, an example in which the supply and stop of the preheating current are periodically repeated has been described. However, as shown in FIG. 3, it is not always necessary to completely stop the supply of the preheating current. A slight preheating current that does not contribute to light emission at the tube end of the electric lamp 2 may be given. Specifically, the oscillation frequency of the inverter circuit 1 during the period Ta in FIG. 3 is set to be sufficiently higher than the oscillation frequency during the period Tb, or the DC voltage supplied to the inverter circuit 1 during the period Ta is reduced. I just need. In order to reduce the DC voltage supplied to the inverter circuit 1, the output voltage of the booster circuit 6 provided before the inverter circuit 1 may be changed as shown in FIG. This booster circuit 6 is connected to a commercial AC power supply AC via a rectifier circuit 7 and also serves as an input power factor improvement circuit.

FIG. 4 shows still another embodiment of the present invention. In the example of FIG. 3, the magnitude of the preheating current is rapidly changed, but the preheating current may be continuously changed as shown in FIG.

[0015]

According to the present invention, a DC power supply, an inverter circuit for converting the output of the DC power supply to high-frequency power, a resonance circuit connected to the output of the inverter circuit, and a resonance circuit driven by the resonance circuit Discharge lamp, a discharge lamp, an inverter control circuit for varying the output of the inverter circuit, and a dimming control circuit for inputting a dimming signal from the outside and controlling the dimming of the discharge lamp and turning off / on the lighting. In the lighting device, when the discharge lamp is turned off, at least two levels of preheating current are switched and supplied at predetermined intervals to the filament of the discharge lamp, so that when the discharge lamp is turned off, the end of the discharge lamp is illuminated. Thus, it is possible to realize a discharge lamp lighting device capable of starting the discharge lamp instantaneously without simultaneously reducing the life of the filament.

[Brief description of the drawings]

FIG. 1 is a waveform chart for explaining the operation of the first embodiment of the present invention.

FIG. 2 is a waveform diagram showing a relationship between an intermittent energization cycle of a preheating current and light emission at a lamp tube end according to the present invention.

FIG. 3 is a waveform chart for explaining the operation of the second embodiment of the present invention.

FIG. 4 is a waveform chart for explaining the operation of the third embodiment of the present invention.

FIG. 5 is a circuit diagram of a conventional discharge lamp lighting device.

FIG. 6 is a characteristic diagram showing a dimming characteristic of a conventional discharge lamp lighting device.

FIG. 7 is a waveform diagram showing a lamp voltage at the time of starting the conventional discharge lamp lighting device.

FIG. 8 is an explanatory diagram illustrating an operation of starting from a dimming state by a conventional discharge lamp lighting device.

FIG. 9 is a circuit diagram for explaining a problem of a conventional example.

[Explanation of symbols]

 Reference Signs List 1 inverter circuit 2 discharge lamp 3 inverter control circuit 4 dimming control circuit

Claims (14)

[Claims] A DC power supply; an inverter circuit for converting an output of the DC power supply into high-frequency power; a resonance circuit connected to an output of the inverter circuit; a discharge lamp driven by a resonance operation of the resonance circuit; A discharge lamp lighting device comprising: an inverter control circuit for changing the output of the circuit; and a dimming control circuit for inputting a dimming signal from the outside and performing dimming control and extinguishing / lighting control of the discharge lamp. A discharge lamp lighting device characterized in that at the time of turning off, at least two levels of preheating current are switched and supplied at predetermined intervals to a filament of the discharge lamp. 2. The preheating current according to claim 1, wherein one of the at least two levels of preheating current has a level of 0.
A discharge lamp lighting device, characterized in that: 3. The discharge lamp lighting device according to claim 1, wherein the preheating current is supplied by an oscillating operation of an inverter circuit, and the oscillating operation is changed to make the preheating current variable. 4. A frequency according to claim 3, wherein the switching element of the inverter circuit is sufficiently higher than the natural oscillation frequency of the resonance circuit during the period of supplying the preheating current when the discharge lamp is turned off, and the lighting of the discharge lamp cannot be maintained. A discharge lamp lighting device characterized in that the discharge lamp lighting device is driven on and off by the device. 5. The preheating current according to claim 1, wherein the preheating current is supplied by an oscillating operation of the inverter circuit, and the level of the DC voltage supplied to the inverter circuit is variable as a means for varying a supply amount of the preheating current. Discharge lamp lighting device characterized by the above-mentioned. 6. The circuit according to claim 5, wherein the means for varying the level of the DC voltage supplied to the inverter circuit is a chopper circuit for improving an input power factor from a commercial AC power supply. Lighting device. 7. The dimming signal is a duty-variable PWM.
2. The discharge lamp lighting device according to claim 1, wherein the control circuit is configured to turn off the discharge lamp when the duty of the dimming signal is equal to or greater than a predetermined value. 8. The dimming control circuit according to claim 1, wherein when the duty of the dimming signal falls below the predetermined value, the starting voltage is immediately applied to the discharge lamp. Discharge lamp lighting device. 9. A first period in which the level of the preheating current is set high and a second period in which the level of the preheating current is set low are alternately switched, and the first period is compared with the second period. Discharge lamp lighting device, wherein the discharge lamp lighting device is set to be sufficiently short. 10. The discharge lamp lighting device according to claim 9, wherein the first period is set to be as short as the time required for the light emission at the tube end of the discharge lamp to rise. 11. The ratio of the first period to the second period and the level of the preheating current in the first period are such that the temperature of the filament is maintained at a temperature at which the filament can be started and turned on without omitting the preceding preheating period. The discharge lamp lighting device according to claim 9, wherein the discharge lamp lighting device is set. 12. The discharge lamp lighting according to claim 9, wherein the first period is set to be shorter than a period in which light emission at a tube end of the discharge lamp can be visually confirmed by the afterimage characteristics of human eyes. apparatus. 13. The discharge lamp lighting device according to claim 9, wherein the level of the preheating current is switched discontinuously between the first period and the second period. 14. The discharge lamp lighting device according to claim 9, wherein a third period in which the level of the preheating current continuously changes is provided between the first period and the second period.