JPH04272700A - Lighting device for discharge lamp - Google Patents

Abstract

PURPOSE:To prevent discharge from being stopped halfway by gradually increasing the output frequency of an inverter used for lighting a discharge lamp in such a manner that a predetermined time is taken for the output frequency to be increased, so as to dim the light of the discharge lamp. CONSTITUTION:When a lighting switch 2 is on, a starting high voltage is applied to a discharge lamp 5 and then the output of an inverter 6 keeps the discharge lamp 5 lighting. When a dimming switch 10 is on under those conditions, a frequency setting circuit 11 gradually increases the output frequency of an inverter 6 to a fixed frequency via an inverter driving circuit 7: Then the discharge lamp 5 is gradually shifted to its dimming state while a predetermined time is taken for the lamp to be shifted to that state : trouble that may arise when the lamp is shifted to that state within a short time is thus avoided while preventing discharge from being stopped halfway and hence the discharge lamp 5 from being turned off.

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 capable of reducing the light of a discharge lamp.

0002

2. Description of the Related Art FIG. 3 is a block diagram showing a circuit configuration of a general discharge lamp lighting device as disclosed in, for example, Japanese Unexamined Patent Publication No. 2-215097. In the figure, 1 is a DC power supply, 2 is a lighting switch, 3 is a DC-DC converter that converts DC to DC, 4 is a high voltage generation circuit that outputs a high voltage to start the discharge lamp 5, and 6 is a discharge lamp. An inverter that outputs alternating current power for lighting the lamp 5, 7 an inverter drive circuit that drives the inverter 6, and 8 a discharge lamp 5.
A discharge detection circuit detects the discharge state of the battery, and the changeover switch 9 is changed according to the detection result.

In the discharge lamp lighting device configured as described above, when the lighting switch 2 is turned on, DC power is supplied from the power source 1 to the DC-DC converter 3.
The DC-DC converter 3 operates, and a high voltage for starting is applied from the high voltage generating circuit 4 to the discharge lamp 5. Then, when the discharge lamp 5 starts discharging and the discharge detection circuit 8 detects this, the changeover switch 9 is changed over, and the AC voltage from the inverter 6 is applied to the discharge lamp 5. Keep it lit.

0004

[Problems to be Solved by the Invention] Since the conventional discharge lamp lighting device is constructed as described above, when the discharge lamp is used as a headlight of a vehicle, for example, it is necessary to dim the discharge lamp while waiting at a traffic light. However, once the lighting switch is turned OFF, it takes time for the light intensity to stabilize the next time it is turned on, and the lamp power must be suddenly reduced to dim the discharge lamp. Then, there was a problem that the discharge stopped and the light went out.

[0005] This invention was made to solve the above-mentioned problems, and aims to provide a discharge lamp lighting device that can reduce the light of the discharge lamp and prevent the discharge from stopping. There is.

[0006]

[Means for Solving the Problems] A discharge lamp lighting device according to the present invention includes an inverter that outputs alternating current power for lighting the discharge lamp, a dimmer switch that brings the discharge lamp into a dimming state, and a dimming switch that dims the discharge lamp. The apparatus is equipped with a frequency setting circuit that gradually increases the output frequency of the inverter over a predetermined period of time when the optical switch is turned on, thereby dimming the discharge lamp.

[0007]

[Operation] In the discharge lamp lighting device of the present invention, a dimmer switch is provided, and when the dimmer switch is turned on,
The output frequency of the inverter gradually increases, and the discharge lamp enters a dimmed state after a predetermined period of time.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing a circuit configuration of a discharge lamp lighting device according to an embodiment of the present invention, and the same reference numerals as in FIG. 3 indicate the same components. In the figure, 1 is a DC power source such as a battery, 2 is a lighting switch, and 3 is a DC-DC
Converter, 4 is a high voltage generation circuit, 5 is a discharge lamp, 6 is an inverter that outputs AC power for lighting the discharge lamp 5, 7 is an inverter drive circuit that drives and controls this inverter 6,
Reference numeral 8 denotes a discharge detection circuit for detecting the discharge state of the discharge lamp 5, and depending on the detection result, the output of the high voltage generation circuit 4 or the output of the inverter 6 is selected and a changeover switch 9 is switched. 10
11 is a dimming switch for putting the discharge lamp 5 into a dimming state;
is the inverter 6 when this dimmer switch 10 is turned on.
This frequency setting circuit sets the frequency in the inverter drive circuit 7 by gradually increasing the output frequency over a predetermined period of time to dim the discharge lamp 5.

Next, the operation will be explained. When the lighting switch 2 is turned on, a high voltage for starting is first applied to the discharge lamp 5 as in the conventional case, and thereafter the discharge lamp 5 is maintained in a lit state by the output of the inverter 6. Then, when the dimmer switch 10 is turned on while the discharge lamp 5 is in the lit state,
The frequency setting circuit 11 gradually increases the output frequency of the inverter 6 to a constant frequency via the inverter drive circuit 7, and shifts the discharge lamp 5 to a dimming state over a predetermined period of time. FIG. 2 shows a frequency setting pattern during this dimming, and it takes several seconds, for example, to achieve the dimming.

Here, in order to reduce the amount of light from the discharge lamp 5, it is sufficient to reduce the electric power given to the discharge lamp 5, and when driving it with the inverter 6, it is sufficient to increase its frequency. However, if this frequency is suddenly increased, that is, if the lamp power is decreased in a short period of time, the discharge may stop due to the characteristics of the discharge lamp 5. Therefore, in this embodiment, the frequency of the inverter 6 is gradually increased after the dimmer switch 10 is turned on. Therefore, the discharge is prevented from stopping and the discharge lamp 5 does not go out.

[0011]

[Effects of the Invention] As described above, according to the present invention, a dimmer switch is provided, and when the dimmer switch is turned on, the output frequency of the inverter is gradually increased to dim the discharge lamp. This has the effect that the discharge lamp can be brought into a dimmed state and that the interruption of discharge can be prevented.

[Brief explanation of the drawing]

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

[Figure 2] Explanatory diagram showing frequency setting pattern during dimming

[Figure 3] Block diagram showing a conventional example

[Explanation of symbols]

5 Discharge lamp 6 Inverter 7 Inverter drive circuit 10 Dimmer switch 11 Frequency setting circuit Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An inverter that outputs alternating current power for lighting a discharge lamp, a dimmer switch that puts the discharge lamp in a dimming state, and a predetermined output frequency of the inverter when the dimmer switch is turned on. A discharge lamp lighting device characterized by comprising a frequency setting circuit that gradually increases the frequency over time to dim the discharge lamp.