JPH07282985A - Discharge lamp lighting device - Google Patents

Abstract

(57) [Summary] [Purpose] To make it possible to start and light up smoothly without going out. [Configuration] Step-up DC power supply circuit 3 and step-up DC power supply circuit 3
And an inverter circuit 4 connected between the output terminals for supplying lighting power to the high-pressure discharge lamp 5 and a lighting control circuit for detecting the output voltage and output current of the step-up DC power supply circuit 3 and controlling the lighting of the high-pressure discharge lamp 5. And 28. The lighting control circuit 28 is provided with a detection circuit 29 for detecting the extinguishing time of the high pressure discharge lamp 5, and changes the output voltage of the step-up DC power supply circuit 3 immediately before the high pressure discharge lamp 5 is turned on. can get.

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 starting and lighting a high pressure discharge lamp such as a metal halide lamp.

[0002]

2. Description of the Related Art A discharge lamp lighting device for starting and lighting a high pressure discharge lamp such as a metal halide lamp has a circuit configuration shown in FIG. In this case, the inverter circuit 4 is connected between the DC output terminals a and b of the step-up DC power supply circuit 3 connected to the DC power supply 1 via the power switch 2, and a metal halide lamp or the like is formed between the output terminals of the inverter circuit 4. The high-pressure discharge lamp 5 is connected via the secondary windings 7a and 7b of the pulse transformer 6. The pulse transformer 6 constitutes a starting circuit 8.

The primary winding of the step-up transformer 9 of the step-up DC power supply circuit 3 is connected to the DC power supply 1 via a power switch 2 and an FET (hereinafter referred to as a switch element) 10, and the gate of the switch element 10 has a drive circuit. 11 is connected. A rectifying / smoothing circuit including a diode 12 and a capacitor 13 is connected to the secondary winding of the step-up transformer 9, and a voltage detecting circuit 14 is connected between the output terminals thereof via a current detecting resistor 15. ing.
A DC output voltage Vd is output between the DC output terminals a and b.

The inverter circuit 4 comprises four bridge-connected FETs (hereinafter referred to as switch elements) 16 to 19
And a drive circuit 20 connected to the gates of the two switch elements 16 and 17, and two switch elements 18 and 1.
Drive circuit 21 connected to each gate of 9,
A capacitor 22 is connected in parallel to a series connection body of the high-voltage discharge lamp 5 which is a load of the inverter circuit 4 and the secondary windings 7 a and 7 b of the pulse transformer 6.

The primary winding 7c of the pulse transformer 6 has an F
An ET (hereinafter referred to as a switch element) 23 and a capacitor 24 are connected, and a DC output voltage Vd between the DC output terminals a and b is applied to the capacitor 24 through a diode 25. The drive circuit 26 is connected to the gate of the switch element 23, and the detection signals of the voltage detection circuit 14 and the current detection resistor 15 are input, and the control signals are output to the drive circuits 11, 20, 21, and 26, respectively. A control circuit 27 is provided.

The drive circuit 11 receiving the control signal from the lighting control circuit 27 repeatedly turns on the switch element 10.
Since it is turned off, a rectangular wave AC voltage is induced in the secondary winding of the step-up transformer 9, and this AC voltage is applied to the diode 12
And is rectified and smoothed by the capacitor 13.

Both drive circuits 20 of the inverter circuit 4,
21 receives the control signal from the lighting control circuit 27, and operates in a phase opposite to each other at a low frequency of about 400 Hz that does not cause an acoustic resonance phenomenon in the discharge lamp 5. That is, when both the switch elements 16 and 19 are turned on (or off), the switch operation in which both the switch elements 17 and 18 are turned off (or on) has a predetermined pause period (dead time) between them. Repeated.

While the switch elements 16 and 19 are kept in the ON state, the switch element 16, the secondary winding 7a of the pulse transformer 6, the high-voltage discharge lamp 5, the secondary winding 7b of the pulse transformer 6 and the switch are connected from the DC output terminal a. A current flows through the element 19 in a path reaching the terminal b. Then, while the switch elements 17 and 18 are kept in the ON state, the switch element 18, the secondary winding 7b of the pulse transformer 6, the high-voltage discharge lamp 5, the secondary winding 7a of the pulse transformer 6 and the switch are connected from the DC output terminal a. A current flows through the element 17 along the path to the terminal b. Therefore, a rectangular wave voltage obtained by alternating the DC output voltage Vd between the DC output terminals a and b is applied to the high pressure discharge lamp 5.

When a control signal for starting the start is sent from the lighting control circuit 27 to the drive circuit 26, the drive circuit 2
6 repeatedly turns on / off the switch element 23. Therefore, the pulse transformer 6 operates as a flyback transformer, and repeatedly applies a high voltage starting pulse to the high pressure discharge lamp 5. The voltage between both terminals of the capacitor 22 immediately before starting is charged to a value substantially equal to the DC output voltage Vd when there is no load.

During the ON period Ton of the switch element 23, the current flowing through the primary winding 7c continues to increase with a gradient of Vd / Lp (Lp is the inductance of the primary winding 7c), and its peak current becomes Ton.Vd / Lp. . When the switch element 23 turns off, the primary winding 7c of the pulse transformer 6
The energy stored in is transferred to the secondary windings 7a and 7b, and the high-voltage pulse of 10 and several KV or more induced in the secondary windings 7a and 7b is applied to the high-pressure discharge lamp 5 as a starting pulse. Since the high-voltage pulse current flows back through the capacitor 22, it does not flow back to the inverter circuit 4.

As shown in FIG. 6, the high-pressure discharge lamp 5 made conductive by the starting pulse enters the glow discharge state, but since the high-pressure pulse is continuously applied thereafter, the re-ignition is repeated and the arc discharge state is repeated. Move to. And
When a control signal is sent to the driver circuit 26 from the lighting control circuit 27 that detects a decrease in the DC output voltage, the operation of the starting circuit 8 is stopped, and the high-pressure discharge lamp 5 receives the rectangular wave AC power supplied from the inverter circuit 4. It will continue to light stably.

Since the impedance of the secondary windings 7a and 7b of the pulse transformer 6 is very small and the discharge lamp 5 is turned on at a low frequency of about 400 Hz, the current limiting action of the secondary windings 7a and 7b is almost zero. Absent. Therefore, the discharge lamp 5 can be stably turned on by the constant current output function of the step-up DC power supply circuit 3.

The DC output voltage Vd immediately before the high-pressure discharge lamp 5 becomes conductive by the start-up pulse is in the no-load state, and therefore shows the maximum value. The DC output voltage Vd during the constant voltage operation period is controlled by the voltage detection circuit 14 by the lighting control circuit 2
7, the lighting control circuit 27 controls the drive circuit 11. The drive circuit 11 controls the on / off duty of the switch element 10 in order to keep the DC output voltage Vd at a predetermined value. The DC output voltage Vd during the constant voltage operation period serves as an energy source for accelerating thermionic emission of the main electrode for the high-pressure discharge lamp 5 immediately before entering the conductive state.

[0014]

Since the DC output voltage Vd during the constant voltage operation period is constant regardless of the inside condition of the high pressure discharge lamp 5, the enclosed substances such as mercury and metal halides, which are enclosed in the pipe, are particularly preferable. At the time of re-ignition where the pressure becomes high, the lamp current and lamp voltage will be repeatedly turned on and off due to polarity reversal, which causes problems such as flickering of light at startup and defective lighting. It was

Therefore, an object of the present invention is to provide a discharge lamp lighting device which can be smoothly started and lit without causing extinction.

[0016]

According to the present invention, in order to achieve the above-mentioned objects, lighting power is supplied to a high-voltage discharge lamp by being connected between a step-up DC power supply circuit and an output terminal of the step-up DC power supply circuit. The high voltage discharge lamp includes an inverter circuit and a lighting control circuit that detects the output voltage and output current of the step-up DC power supply circuit and controls the lighting of the high pressure discharge lamp. There is provided a discharge lamp lighting device characterized by being provided with an extinguishing prevention circuit for changing an output voltage of a step-up DC power supply circuit immediately before lighting.

[0017]

In the present invention, the output voltage of the step-up DC power supply circuit immediately before the high-pressure discharge lamp is lit is changed by detecting the extinction time of the high-pressure discharge lamp, so that sufficient heat is applied to the main electrode of the high-pressure discharge lamp at startup. It is possible to provide a discharge lamp lighting device that can give electron emission energy and that has good starting characteristics without extinguishing.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

The circuit configuration shown in FIG. 1 is basically different from the circuit configuration shown in FIG. 5 in that a lighting control circuit shown by reference numeral 28 is provided with a turn-off time detection circuit 29. Since there is no fundamental difference in the other configurations, corresponding components are designated by the same reference numerals.

However, the drive circuit 11, which is controlled by the lighting control circuit 28, changes the ON / OFF duty of the switch element 10 in accordance with the fluctuation of the DC output voltage Vd detected by the voltage detection circuit 14. by this,
The output voltage Vd of the step-up DC power supply circuit 3 is controlled to a predetermined value, but the on / off duty of the switch element 10 is determined so that the output current of the step-up DC power supply circuit 3 does not exceed a predetermined upper limit. It also has a function.

In the present embodiment, the constant current function of the output current of the step-up DC power supply circuit 3 has priority over the constant voltage function of the output voltage, and the on / off duty of the switch element 10 is determined. That is, when the output current of the boost DC power supply circuit 3 is less than or equal to the upper limit value for a load in a certain state, the boost DC power supply circuit 3 performs a constant voltage operation. However, when the load condition of the step-up DC power supply circuit 3 changes and a current exceeding the output current limit value tries to flow, the constant current operation works even if the output voltage becomes less than the set value, and the output exceeding the set value is output. No current is passed.

FIG. 2 shows the configuration of each main part of the lighting control circuit 28 and the extinction time detection circuit 29. In this case, the lighting control circuit 28 is the integrated circuit 3 for the switching regulator.
0, a lighting determination circuit 31, and set voltage circuits 32 and 33. The output terminals of the voltage detection circuit 14 and the current detection resistor 15 of the step-up DC power supply circuit 3 are connected to the positive input terminal of the error amplifier EA1 and the negative input terminal of the error amplifier EA2 of the integrated circuit 30, respectively. There is. Further, the oscillation output terminals E1 and E2 of the integrated circuit 30 are connected to the drive circuit 12 of the step-up DC power supply circuit 3.

The integrated circuit 30 compares the output current and output voltage of the step-up DC power supply circuit 3 with the set voltage of the set voltage circuits 32 and 30, and oscillates the output E within the range not exceeding the set level.
The duty ratios of 1 and E2 are controlled. The lighting determination circuit 31 receives the detection voltage of the voltage detection circuit 14 of the step-up DC power supply circuit 3 and outputs an “H” signal when the high-pressure discharge lamp 5 is on and an “L” signal when it is off. have.

On the other hand, the extinguishing time detecting circuit 29 receives the output signal of the lighting discriminating circuit 31 and detects the extinguishing time of the high pressure discharge lamp 5, and the extinguishing time detector 3.
4 and a bias circuit with timer 35 for controlling the positive input terminal potential of the error amplifier EA1.

The extinction time detector 34 converts the extinction time into a voltage with a time constant of several tens of seconds, and outputs a higher voltage as the extinction time is shorter. Further, the bias circuit 35 receives the output signal of the light-off time detector 34 and receives the output signal from the voltage detection circuit 1
4 has a function of applying a negative bias to the output signal.

The error amplifier EA1 controls the output voltage Vd during no load (constant voltage operation) until the high-pressure discharge lamp 5 becomes conductive. This is the output voltage V
The voltage value divided by the voltage detection circuit 14 for detecting d is
It is determined when the output value of the set voltage circuit 33 is reached. That is, by applying a negative bias to the resistance-divided voltage value in the voltage detection circuit 14, the output voltage Vd in the constant voltage operation is raised. Bias circuit 3
The output terminal of the lighting determination circuit 31 is connected to the reset terminal of No. 5, and when the high-pressure discharge lamp 5 is turned on, reset is applied and the bias value becomes zero.

FIG. 3 shows the operation timing of the lighting control circuit 28 and the extinguishing time detection circuit 29. The output signal of the lighting determination circuit 31 is "H" when the light is on, and "L" when the light is off.
Becomes The extinction time detection circuit 29 integrates and inverts and amplifies this signal to generate an output having a waveform as shown in the figure. Two cases, A and B, are assumed for the output during relighting depending on the length of the light-off time. It can be seen that B having a short turn-off time has a larger output than A having a long turn-off time.

FIG. 4 shows changes in the output voltage Vd of the step-up DC power supply circuit 3 during the constant voltage operation. B having a short extinction time has a larger negative bias applied to the output voltage of the voltage detection circuit 14 than A having a long extinction time, and thus the output voltage Vd during the constant voltage operation becomes higher. This means that the shorter the turn-off time of the high-pressure discharge lamp 5 is and the higher the pressure of the metal enclosure such as the metal halide enclosed in the lamp, the more sufficient thermoelectrons for the main electrode of the high-pressure discharge lamp 5. This means that discharge energy can be given, and it is possible to obtain a discharge lamp lighting device having good starting characteristics without extinguishing.

In the above embodiment, the boost DC power supply circuit 3
A flyback DC / DC converter is used for the above, but a DC / DC converter such as a forward method or a push-pull method can be used. Further, the inverter circuit 4 does not have to be the full bridge type, and may be the half bridge type. Further, a voltage other than a resistor can be used to detect the voltage or current with respect to the lamp load, and a semiconductor element other than EFT can be used as the switch element. Further, instead of using the FET or the pulse transformer as the starting means of the discharge lamp, a discharge gap or the like may be used.

Further, in the above-mentioned embodiment, the positive input terminal potential of the error amplifier of the switching regulator integrated circuit is controlled, but the output voltage of the lamp voltage supply circuit may be controlled without depending on such a configuration. Of course it is good.

Further, an example of lighting the discharge lamp with a rectangular wave voltage having a low frequency of 400 Hz has been shown, but if the discharge lamp does not cause harmful phenomena such as electrophoresis and acoustic resonance, it can be used for high frequency lighting. Applicable.

[0032]

As described above, according to the present invention, the extinguishing time at the time of starting the discharge lamp is detected, the output voltage immediately before the lighting of the discharge lamp is changed, and the discharge lamp is smoothly shifted to the arc discharge state. Therefore, the discharge lamp lighting device having good starting characteristics without extinguishing can be obtained.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram of a discharge lamp lighting device according to an embodiment of the present invention.

FIG. 2 is an electric circuit diagram of a main part of a discharge lamp lighting device according to an embodiment of the present invention.

FIG. 3 is an output waveform diagram of a main part of the discharge lamp lighting device according to the embodiment of the present invention.

FIG. 4 is a lamp voltage waveform diagram of a discharge lamp lighting device according to an embodiment of the present invention.

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

FIG. 6 is a waveform diagram of a lamp voltage / lamp current of a conventional discharge lamp lighting device.

[Explanation of symbols]

 3 step-up DC power supply circuit 4 inverter circuit 5 high-voltage discharge lamp 8 starting circuit 28 lighting control circuit 29 extinguishing time detection circuit 30 integrated circuit 31 lighting discrimination circuit 34 extinguishing time detector 35 bias circuit

Claims (1)

[Claims] 1. A step-up DC power supply circuit, an inverter circuit connected between output terminals of the step-up DC power supply circuit to supply lighting power to a high-pressure discharge lamp, and an output voltage and an output current of the step-up DC power supply circuit are detected. A lighting control circuit for controlling lighting of the high-pressure discharge lamp is provided, and the lighting control circuit detects an extinguishing prevention circuit that detects an off time of the high-pressure discharge lamp and changes the output voltage of the boost DC power supply circuit immediately before lighting of the high-pressure discharge lamp. Discharge lamp lighting device characterized by being attached.