JPH04272697A - Lighting device for discharge lamp - Google Patents

Abstract

PURPOSE:To provide an optimum quick rise in the quantity of light by switching the output frequency of an inverter to a preset pattern in accordance with the result of detection of lamp voltage or lamp current when discharge is started. CONSTITUTION:When a lighting switch is on, a starting high voltage is applied to a discharge lamp 4 from a high voltage generating circuit 3 and then lighting of the discharge lamp 4 is maintained by the output of an inverter 5. In this case, a lamp voltage detecting circuit 7 detects lamp voltage or lamp current at the start of discharge of the discharge lamp 4 and determines from the detected value whether lighting of the lamp 4 is started or restarted. A pattern changeover switch 11 is turned in accordance with the result of the detection. If the result indicates the start of lighting, the output of a starting frequency pattern 9 is selected, while if the restart of lighting is indicated the output of a restarting frequency pattern generating circuit 10 is selected and input to an inverter driving circuit 6: Then the range of variation in the quantity of light at the lighting of the lamp becomes narrow and a quick rise in the quantity of light is provided and the same light quantity characteristics are provided at the start and restart of lighting of the lamp.

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 that can provide an optimum light intensity rise.

0002

2. Description of the Related Art FIG. 5 is a block diagram showing the circuit configuration of a general discharge lamp lighting device as disclosed in, for example, Japanese Patent Laid-Open No. 2-215097. In the figure, 1 is a DC power supply, 2 is a DC-DC converter that converts the DC to DC and boosts the voltage, 3 is a high voltage generation circuit that outputs a high voltage to start the discharge lamp 4, and 5 is a discharge lamp. An inverter that outputs alternating current power for lighting the electric lamp 4; 6 an inverter drive circuit that drives the inverter 5; 7 a lamp voltage detection circuit that detects the lamp voltage at the start of discharge of the discharge lamp 4; The voltage changeover switch 8 is switched.

In the discharge lamp lighting device configured as described above, when the lighting switch is turned on, the power supply 1 is turned on.
DC power is supplied to the DC-DC converter 2 from D
The C-DC converter 2 operates, and a high frequency high voltage for starting is applied from the high voltage generating circuit 3 to the discharge lamp 4. Then, when the discharge lamp 4 starts discharging and the lamp voltage detection circuit 7 detects a predetermined lamp voltage, the changeover switch 8 is switched, and the AC voltage from the inverter 5 is applied to the discharge lamp 4. The discharge lamp 4 remains lit.

FIG. 6 shows the light quantity characteristics when the discharge lamp is turned on. In a discharge lamp 4 such as a GDL of this type, when the input power at the time of lighting is constant, the amount of light changes significantly over time after the start of discharge as shown in the figure. However, this amount of light becomes constant after a few seconds and becomes stable. This change in light amount differs between when the discharge lamp 4 is started (cold start) and when restarted with a short turn-off time (hot start).

[0005]

[Problems to be Solved by the Invention] Since the conventional discharge lamp lighting device is constructed as described above, there is a large change in the amount of light after the start of discharge during lighting, and an optimum rise in the amount of light cannot be obtained. There was a problem in that the light quantity characteristics were significantly different between the time of starting and the time of restarting.

[0006] This invention was made in order to solve the above-mentioned problems, and the range of change in the amount of light during lighting is small, an optimum rise in the amount of light can be obtained, and the difference between starting and restarting is small. The object of the present invention is to provide a discharge lamp lighting device that can obtain similar light quantity characteristics.

[0007]

[Means for Solving the Problems] A discharge lamp lighting device according to the present invention includes an inverter that supplies alternating current power for lighting to a discharge lamp, and a detection circuit that detects a lamp voltage or a lamp current when the discharge lamp starts discharging. and is configured to switch the output frequency of the inverter to a preset pattern according to the detection result of the detection circuit.

[0008]

[Operation] In the discharge lamp lighting device of the present invention, the lamp voltage or lamp current is detected at the start of discharge of the discharge lamp,
Based on the detection results, the output of the inverter is switched to a preset pattern. Therefore, it is possible to control the lamp power of the discharge lamp suitable for starting and restarting.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the circuit configuration of a discharge lamp lighting device according to an embodiment of the present invention, and the same reference numerals as in FIG. 5 indicate the same components. In the figure, 1 is a DC power supply, 2 is a DC-DC converter that boosts the power supply voltage, 3 is a high voltage generation circuit that provides a high frequency high voltage to the discharge lamp 4, and 5 is an AC power supply for lighting the discharge lamp 4. An inverter 6 supplies the inverter, an inverter drive circuit 6 drives the inverter 5, and a lamp voltage detection circuit 7 detects the lamp voltage at the start of discharge of the discharge lamp 4. A voltage changeover switch 8 is switched based on the detection output.

Reference numeral 9 denotes a starting frequency pattern generation circuit which outputs an optimum driving frequency pattern for the inverter 5 at the time of starting;
Reference numeral 10 indicates a restart frequency pattern generation circuit which outputs the optimum drive frequency pattern of the inverter 5 at the time of restart, and reference numeral 11 indicates the output frequency of the inverter 5 in accordance with the detection result of the lamp voltage detection circuit 7 by each pattern generation circuit 9, 10. This is a pattern changeover switch that changes to a preset pattern.

Next, the operation will be explained. When the lighting switch is turned on, a high voltage for starting is first applied from the high voltage generating circuit 3 to the discharge lamp 4 as in the conventional case, and then the discharge lamp 4 is maintained in a lit state by the output of the inverter 5. . At this time, the lamp voltage detection circuit 7 detects the lamp voltage when the discharge lamp 4 starts discharging, and determines whether it is starting or restarting from the detected value. Then, depending on the detection result, the pattern changeover switch 11 is switched, and if it is the time of starting, the output of the starting frequency pattern generation circuit 9 is selected, and if it is determined that it is the time of restarting, the output of the restarting frequency pattern generation circuit 10 is selected.
The selected output is inputted to the inverter drive circuit 6.

FIG. 2 shows the starting frequency pattern generation circuit 9.
FIG. 3 shows the restart frequency pattern set in the restart frequency pattern generation circuit 10. In either case, the frequency is shifted to, for example, about 2 kHz to 10 kHz within a few seconds (5 to 10 seconds) from the start of discharge, and the lamp power of the discharge lamp 4 is changed by switching such a frequency pattern at the time of starting and restarting. As shown in Figure 4, by controlling the amount of light, it is possible to obtain a small change in the amount of light during lighting and a rapid rise in the amount of light, and also to obtain similar light amount characteristics at the time of starting and restarting. It will be done. Note that the lamp voltage at the time of starting this discharge is about 0 to 10 V at the time of starting, and about 20 to 40 V at the time of restarting.

Here, in the above circuit, the lamp voltage at the start of discharge is detected to control whether to start or restart, but the lamp current at the start of discharge is detected to determine whether to start or restart. You can do it like this. That is, when the discharge lamp 4 is started, the gas pressure within the lamp is low, and when restarted, the gas pressure is high. Therefore, at the start of discharge, the lamp voltage (voltage between electrodes) and lamp current are different between when starting and when restarting. By detecting this and switching the output pattern of the inverter 5, it is possible to always obtain an optimum rise in the amount of light, and it becomes possible to obtain an ideal light source.

[0014]

As described above, according to the present invention, the lamp voltage or lamp current is detected when the discharge lamp starts discharging, and the output of the inverter is switched to a preset frequency pattern based on the detection result. Changes in the amount of light when the discharge lamp is turned on are small, a rapid rise in the optimum amount of light can be obtained, and the same light amount characteristics can be obtained when starting and restarting.

[Brief explanation of the drawing]

[Figure 1] Block diagram showing one embodiment of this invention

[Figure 2] Explanatory diagram showing an example of a starting frequency pattern

[Figure 3
] Explanatory diagram showing an example of restart frequency pattern

[Figure 4
] Light intensity characteristic diagram of the discharge lamp in Figure 1

[Figure 5] Block diagram showing a conventional example

[Figure 6] Light intensity characteristic diagram of the discharge lamp in Figure 5

[Explanation of symbols]

4 Discharge lamp 5 Inverter 6 Inverter drive circuit 7 Lamp voltage detection circuit 9 Starting frequency pattern generation circuit 10 Restarting frequency pattern generation circuit 11 Pattern changeover switch Note that the same reference numerals in the drawings indicate the same or equivalent parts.

Claims (1)

[Claims] 1. An inverter that supplies alternating current power for lighting to a discharge lamp, and a detection circuit that detects lamp voltage or lamp current at the start of discharge of the discharge lamp, and adjusts the output of the inverter according to the detection result of the detection circuit. A discharge lamp lighting device characterized by switching the frequency to a preset pattern.