JPH05326185A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To stably light-control a discharge lamp to a low luminous flux range by superposing a DC current of a level capable of keeping the discharge in low luminous flux light control to a high frequency current followed by application to the discharge lamp. CONSTITUTION:A discharge lamp lighting device for low luminous flux light control lighting is provided with a temperature detecting part 6 for detecting the ambient temperature and a light control part 3 for increasing DC power at low temperature according to the ambient temperature detected by the temperature detecting part 6. Since the temperature detecting part 6 for detecting the ambient temperature is provided to control the device so that the DC superposed power is increased at the time of low luminous flux lighting at low temperature, the flicker and lighting failure of a discharge lamp 1 can be solved.

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 for stably lighting a discharge lamp in a low luminous flux region.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram of a conventional discharge lamp dimming lighting device (Japanese Patent Application No. 1-75572). This lighting device includes a low-pressure mercury discharge lamp 1, a high-frequency power supply 2 that supplies high-frequency power to the discharge lamp 1, and a dimming control unit 3 that dims the discharge lamp 1 from an arc discharge region to a glow discharge region.
DC power superimposing means 4 for superimposing DC power of a level capable of maintaining discharge during dimming of low luminous flux on the high frequency power,
It is possible to adjust light to a low luminous flux level. The specific circuit diagram is shown in FIG.

The circuit configuration shown in FIG. 5 will be described below. The commercial AC power supply Vs is connected to the AC input terminal of the diode bridge DB1. Diode bridge DB
A smoothing capacitor C1 is connected to the DC output terminal of 1. A series circuit of MOS transistors Q1 and Q2 is connected in parallel to both ends of the capacitor C1.
A primary winding of the high frequency transformer T2 is connected to both ends of the MOS transistor Q2 via a capacitor C3 for cutting a direct current component, and a power supply side terminal of a filament of the discharge lamp 1 is connected to the both ends of the MOS transistor Q2 via an inductor L2. ing. A capacitor C4 for energizing resonance and preheating current is connected in parallel between the non-power supply side terminals of the filament of the discharge lamp 1. The secondary winding output of the high frequency transformer T2 is rectified by the diode D1 and smoothed by the capacitor C6 to obtain a DC voltage. The capacitor C6 is connected to one end of the discharge lamp 1 via the inductor L1 and is connected to the other end of the discharge lamp 1 via the diode D2 and the MOS transistor Q3. The inductor L1 is for blocking high frequencies and prevents the high frequency voltage applied to the discharge lamp 1 from leaking to the capacitor C6. The inductor L2 constitutes an LC series resonance circuit together with the capacitor C4, and the discharge lamp 1 is started and lit by the resonance voltage generated across the capacitor C4. Capacitor C
Reference numeral 3 is for DC cutting, has a capacity sufficiently larger than that of the capacitor C4, and does not contribute to resonance. C7 is a DC cut capacitor of the high frequency transformer T2.

The commercial AC power source Vs is connected via a step-down transformer T1 to the AC input terminal of a diode bridge DB2, and the DC output terminal of the diode bridge DB2 is connected to a parallel circuit of a capacitor C2 and a zener diode ZD1. DC low voltage Vc obtained in the capacitor C2
c is supplied to the inverter control unit S. A first control signal is supplied between terminals a and b connected between the gate and source of the MOS transistor Q1. Also, M
The second control signal is supplied between the terminal c connected to the gate of the OS transistor Q2 and the ground point. The first control signal and the second control signal do not become High level at the same time, and the first period in which the first control signal is High level and the second control signal is Low level; A second period in which the second control signal is at the Low level at the same time, a third period in which the first control signal is at the Low level and the second control signal is at the High level, and the first and second control signals are At the same time, the fourth period in which the Low level is set is repeated in the same order.

In the first period, the MOS transistor Q1
Is turned on, the MOS transistor Q2 is turned off, and the path from the positive terminal of the capacitor C1 through the MOS transistor Q1, the capacitor C3 for cutting the direct current component, the load circuit including the high frequency transformer T2 and the discharge lamp 1, and the negative terminal of the capacitor C1. An electric current flows. In the second period, the MOS transistors Q1 and Q2 are simultaneously turned off, and the oscillating current of the load circuit flows through the built-in anti-parallel diode parasitic between the drain and source of the MOS transistor Q2. Third
In the period of, the MOS transistor Q1 is turned off, the MOS transistor Q2 is turned on, and the capacitor C3 for cutting the direct current component serves as a power source, so
A current flows through the path returning to the capacitor C3 via the transistor Q2 and the load circuit. In the fourth period, the MOS transistors Q1 and Q2 are turned off at the same time, and the oscillating current of the load circuit flows through the built-in anti-parallel diode parasitic between the drain and source of the MOS transistor Q1. In this way, a high frequency alternating current flows through the load circuit. The switching frequency of the MOS transistors Q1 and Q2 is generally set to be slightly higher than the natural vibration frequency of the load circuit.

A third control signal is supplied between the terminal d connected to the gate of the MOS transistor Q3 and the ground point. By this third control signal, the MOS transistor Q
3 becomes conductive when the luminous flux is low, and since DC power is superimposed on the discharge lamp 1, the discharge lamp 1 does not easily go out.

As a dimming method, the inverter control unit 3 is controlled by a dimming signal supplied to the inverter control unit 3.
A frequency control method for adjusting the power supplied to the discharge lamp 1 by changing the resonance state of the inductor L2 and the capacitor C4 by changing the frequency of the high frequency signal supplied to the gates of the MOS transistors Q1 and Q2 from ing.

[0008]

In the above-mentioned conventional example, the discharge lamp 1 is stably lit even at a low luminous flux at room temperature.
At low temperature (10 ° C. or less), there is a problem that the discharge lamp 1 flickers or disappears.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a discharge lamp lighting device capable of maintaining stable lighting with a low luminous flux at such a low temperature. is there.

[0010]

According to the present invention, in order to solve the above-mentioned problems, as shown in FIG.
A high frequency power source 2 for supplying high frequency power to the discharge lamp 1 via a first impedance element Z1 and a direct current power source 5 for supplying direct current power to the discharge lamp 1 via a second impedance element Z2. In a discharge lamp lighting device for low-beam dimming lighting, the temperature detecting unit 6 detects an ambient temperature, and a dimming control for increasing the DC power at a low temperature according to the ambient temperature detected by the temperature detecting unit 6. It is characterized in that part 3 is provided.

[0011]

In the discharge lamp lighting device of the present invention, the temperature detecting unit 6 for detecting the ambient temperature is provided in this manner, and the DC superposition power is controlled to increase when the low luminous flux is lit at a low temperature. Therefore, the flicker and the extinction of the discharge lamp 1 can be eliminated.

[0012]

FIG. 2 is a circuit diagram of a first embodiment of the present invention.
In the figure, the circuit configuration and the operation other than the circuit section A surrounded by the dotted line are the same as those of the conventional example, and therefore, the same portions are denoted by the same reference numerals and the duplicate description will be omitted. The circuit section A surrounded by the dotted line is a DC superimposed voltage changing section, and is composed of voltage dividing resistors Rx and Ry and a positive temperature coefficient thermistor PCT. Resistance value Rt of PTC thermistor PCT
Is Rn at 25 ° C. and R ₀ at 0 ° C., R ₀ <Rn. Therefore, the DC superimposed voltage Vs is Vsn at 25 ° C.,
Assuming Vs ₀ at 0 ° C., Vsn <Vs ₀ . That is, the DC superimposed voltage Vs ₀ at a low temperature becomes higher than the DC superimposed voltage Vsn at room temperature, and even when the low luminous flux is lit at a low temperature, the discharge lamp 1 can be prevented from extinguishing and flickering, and thus stable. It is possible to realize the turned on.

FIG. 3 is a circuit diagram of the second embodiment of the present invention. In the figure, the circuit configuration and the operation other than the circuit portion B surrounded by the dotted line are the same as those of the conventional example, and therefore, the same portions will be denoted by the same reference numerals and redundant description will be omitted. The circuit portion B surrounded by the dotted line is a DC superimposed voltage changing portion, and includes a resistor Rx, a Zener diode ZD2, diodes D3 and D4, and a transistor Q4. The diodes D3 and D4 are used as temperature detecting elements and detect the temperature by the change in the forward voltage due to the temperature change. When ambient temperature decreases, diode D
Since the forward voltage of D3 and D4 increases, the transistor Q
Since the base potential of No. 4 rises and the emitter potential also rises following this, the DC superimposed voltage can be increased. As a result, it is possible to increase the DC superimposed voltage at low temperature, prevent the discharge lamp 1 from extinguishing and flicker even during low luminous flux lighting at low temperature, and realize stable lighting.

[0014]

According to the discharge lamp lighting device of the present invention, the DC power of a level capable of maintaining the discharge during the dimming of the low luminous flux is applied to the discharge lamp by superimposing it on the high frequency power. In addition, the discharge lamp can be prevented from going out and flickering, and dimming control of the discharge lamp can be stably performed up to the low luminous flux area.Furthermore, a temperature detection unit is provided to generate DC superimposition power when the low luminous flux is lit at low temperature. Since the number is increased, there is an effect that even when the low luminous flux is lit at a low temperature, the discharge lamp does not go out and flickers and a stable lighting state can be maintained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of the present invention.

FIG. 2 is a circuit diagram of a first embodiment of the present invention.

FIG. 3 is a circuit diagram of a second embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a conventional example.

FIG. 5 is a specific circuit diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 discharge lamp 2 high frequency power supply 3 dimming control section 4 DC power superimposing means 5 DC power supply 6 temperature detection section Z1 first impedance element Z2 second impedance element

Claims (1)

[Claims] 1. A discharge lamp, a high frequency power supply for supplying high frequency power to the discharge lamp via a first impedance element, and a direct current power supply for supplying direct current power to the discharge lamp via a second impedance element. In a discharge lamp lighting device for low luminous flux dimming lighting, including: a temperature detection unit that detects an ambient temperature; and a dimming control unit that increases the DC power at a low temperature according to the ambient temperature detected by the temperature detection unit. And a discharge lamp lighting device.