JPH07335388A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To provide a discharge lamp lighting device in which a discharge lamp can be smoothly started without failure, and stably lighted. CONSTITUTION:This discharge lamp lighting device has a step-up DC power source circuit 3, an inverter circuit 4 connected between the output terminals of the step-up DC power source circuit 3 to supply AC power to a high pressure discharge lamp 5, and a lighting control circuit 28 for detecting the output voltage and output current of the step-up DC power source circuit 3 to control the lighting of the high pressure discharge lamp. The lighting control circuit 28 detects the extinguishing time of the high pressure discharge lamp 5 at starting together with an extinguishing time detecting circuit 29 and a timer circuit 32 attached thereto, and changes the operating frequency of the inverter circuit 4 over one cycle or more on the basis of this.

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 driver 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
A driver circuit 20 connected to the gates of the two switch elements 16 and 17, and two switch elements 18 and 1
And a driver 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. A driver circuit 26 is connected to the gate of the switch element 23, and a lighting control circuit 27 that receives the detection signals of the voltage detection circuit 14 and the current detection resistor 15 controls the driver circuits 11, 20, 21, and 26. Give a signal.

The driver 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 driver 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 high pressure 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) is repeated with a predetermined pause period (dead time) in between. Be done.

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, the rectangular wave AC 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 driver circuit 26, the driver circuit 2
6 repeatedly turns on / off the switch element 23. Therefore, the pulse transformer 6 operates as a flyback transformer and repeatedly supplies the high-voltage discharge lamp 5 with a high-voltage starting pulse. The capacitor 22 just before starting,
The charging voltage is approximately 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 value is Ton.Vd / Lp. Become. Switch element 23
Turns off, the primary winding 7 of the pulse transformer 6
The energy stored in c is transmitted to the secondary windings 7a and 7b and induced by the secondary windings 7a and 7b.
The above high-voltage pulse 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.

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 supplied thereafter, the re-ignition is repeated to shift to the arc discharge state. Then, from the lighting control circuit 27 that detects the decrease in the DC output voltage Vd to the driver circuit 26.
When the control signal is sent to, the operation of the starting circuit 8 is stopped, and the high-pressure discharge lamp 5 continues to be lit stably with the rectangular wave AC power supplied from the inverter circuit 4.

Since the secondary windings 7a and 7b of the pulse transformer 6 have a very small inductance and the high pressure discharge lamp 5 is lit at a low frequency of about 400 Hz, the current limiting action of the secondary windings 7a and 7b does not occur. Almost never
The high-voltage discharge lamp 5 continues to be lit stably 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 driver circuit 11. The driver circuit 11 controls the on / off duty of the switch element 10 in order to maintain 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.

By the way, in the discharge lamp lighting device thus constructed, as shown in FIG. 8, the voltage applied to the high pressure discharge lamp 5 is accompanied by an instantaneously high re-ignition voltage when the polarity is reversed. This is because the high pressure discharge lamp 5 immediately after the current quiescent period accompanying the reversal of polarity requires a transiently large electron emission energy. Particularly, at the time of starting, a considerable amount of energy is required to make the main electrodes of the high-pressure discharge lamp 5 electrically conductive and to shift to a stable arc discharge state.

[0015]

Therefore, as shown in FIG. 9, a re-ignition voltage higher than that during stable lighting is applied for a while from the start of starting, and during this period the ignition and the extinguishing are extinguished. It is unavoidable that and occur repeatedly, which leads to the problem of flickering of light and defective lighting. It should be noted that such a problem does not occur if the lighting is direct current lighting or lighting at a low frequency. However, direct current lighting shortens the life of the lamp due to stress on the lamp electrodes and bias of ions. Further, when the lamp is lit at a low frequency, the lamp operation becomes unstable during the stable lighting period, which causes a problem such as flickering of light.

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

[0017]

According to the present invention, in order to achieve the above-described object, a step-up DC power supply circuit is connected between output terminals of the step-up DC power supply circuit to supply a rectangular wave output to a high-voltage discharge lamp. And a lighting control circuit that controls the lighting of the high-pressure discharge lamp by detecting the output voltage and output current of the step-up DC power supply circuit, and the lighting control circuit detects the turn-off time of the high-pressure discharge lamp at the time of starting. As a result, a discharge lamp lighting device is provided, which is provided with an extinguishing prevention circuit for changing the operating frequency of the inverter circuit for a period of one cycle or more.

[0018]

In the present invention, the operating frequency of the inverter circuit is changed for a period of one cycle or more by detecting the extinction time of the high pressure discharge lamp at the time of starting, so that the high pressure discharge lamp can be extinguished at the time of starting. It can be driven at a frequency that is not present, and can smoothly transition to an arc discharge state.

[0019]

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. 7 in that the lighting control circuit denoted by reference numeral 28 includes a turn-off time detection circuit 29, an oscillation circuit 30, a frequency control circuit 31, and The timer circuit 32 is attached. Since there is no fundamental difference in the other configurations, corresponding components are designated by the same reference numerals.

The lighting control circuit 28 is the lighting control circuit 2 described above.
As in the case of No. 7, in addition to having the function of controlling the driver circuits 11, 20, 21, and 26, it also has the control function of receiving and operating the output signal of the light-off time detection circuit 29. The driver circuit 11 changes the on / off / duty of the switch element 10 in accordance with the variation of the DC output voltage Vd detected by the voltage detection circuit 14, so that the output voltage Vd of the boost DC power supply circuit 3 is always controlled to a predetermined value. To be done. However, the on / off duty of the switch element 10 is set so that the output current of the step-up DC power supply circuit 3 does not exceed a predetermined upper limit. Further, the constant current function of the output current of the step-up DC power supply circuit 3 is prioritized over the constant voltage function of the output voltage. That is, if the output current of the step-up DC power supply circuit 3 is less than or equal to the upper limit value for a load in a certain state, the step-up DC power supply circuit 3 performs a constant voltage operation. However, if the load condition of the step-up DC power supply circuit 3 changes and the current exceeds the output current limit value and the current tries to flow, the constant current operation works even if the output voltage is less than the set value, and the set value is exceeded. The output current does not flow.

Lighting control circuit 28, extinguishing time detection circuit 2
The configurations of 9, the oscillator circuit 30, the frequency control circuit 31, and the like are shown in FIGS. The lighting control circuit 28 includes a lighting determination circuit 33 that determines the lighting state of the high-voltage discharge lamp 5 by receiving the detection output of the voltage detection circuit 14 of the step-up DC power supply circuit 3, and the turn-off time detection circuit 29 determines the high-voltage discharge. The off time of the lamp 5 is detected. Further, the oscillation circuit 30 controls the operating frequency of the inverter circuit 4, and the timer circuit 32 receives the detection output of the light-off time detection circuit 29 and causes the frequency control circuit 31 to operate for a fixed time.

The lighting determination circuit 33 is a step-up DC power supply circuit 3
Receiving the detection voltage of the voltage detection circuit 14 which receives the output voltage Vd of
When the lamp is turned off, the "L" signal is output. The turn-off time detection circuit 29 time-integrates each of the “H” and “L” signals of the turn-on determination circuit 33 with a certain time constant,
The inverted amplified signal TDET is output. Therefore, the longer the turn-off time is, the higher the inverted amplified signal TDET becomes.

The frequency control circuit 31 is the turn-off time detection circuit 2
The output signal TDET of 9 is received, and the frequency of the oscillation circuit 30 is controlled according to the extinction time. The timer circuit 32 receives the output signal TDET of the turn-off time detection circuit 29 and operates the frequency control circuit 31 according to the turn-off time, and the operating time becomes shorter as the turn-off time becomes longer.

When the switching regulator control IC 34 of the oscillator circuit 30 is an integrated circuit SG3524 manufactured by TI, for example, the oscillation frequency f can be controlled only by changing the current flowing to the RT terminal with the resistor 35 or the like. The frequency control circuit 31 is connected to the resistor 35 in parallel via a switch 36. The switch 36 is controlled to open and close by the timer circuit 32, and the timer circuit 3
2 is controlled by the potential of the output signal TDET of the turn-off time detection circuit 29. That is, the frequency control circuit 31 operates and the oscillation frequency of the oscillation circuit 30 is changed only during the period when the switch 36 is held in the ON state by the timer circuit 32.

The frequency control circuit 31 comprises a resistor 37, an operational amplifier 38, a resistor 39, a transistor 40 and a resistor 41, and the current flowing through the resistor 41 is the off time detection circuit 2
It changes depending on the potential of the output signal TDET of 9 and the oscillation frequency of the oscillation circuit 30 changes. Then, the frequency control circuit 31 is connected in parallel to the resistor 35, whereby the oscillation frequency f switches to an oscillation frequency f ′ lower than that. Further, the output signal TD of the turn-off time detection circuit 29
When the potential of ET is high, the oscillation frequency f'is also high,
When the potential of TDET is low, the oscillation frequency f'is also low.

The high-pressure discharge lamp 5 has a higher temperature as the extinguishing time is shorter, and the gas pressure in the tube is higher. Therefore, it is difficult to shift to stable lighting after arc discharge. If the inverter circuit 4 inverts the polarity during this period, the inverter circuit 4 easily disappears. Therefore, if the oscillation frequency f ′ is set as low as possible to reduce the polarity inversion, stable lighting can be smoothly performed.

After shifting to stable lighting, the timer circuit 32
Causes the switch circuit 36 to open, the oscillator circuit 30 outputs an oscillation frequency f suitable for lighting. Oscillation frequency f '
Is low, if the operation period of the frequency control circuit 31 is set within a half cycle of the lighting frequency f ′, DC lighting occurs for a moment, so that the electrodes of the high-pressure discharge lamp 5 are adversely affected and high-voltage discharge occurs. There are inconveniences such as shortening the life of the lamp 5. Therefore, the operating period of the frequency control circuit 31 is set to be one cycle or more of the lighting frequency f ′, and the lower the oscillation frequency, the longer the operating period. When the extinguishing time is long, the tube wall temperature of the high-pressure discharge lamp 5 is low, and the unstable period after arc discharge is short. Therefore, the high frequency discharge lamp 5 is lit while keeping the oscillation frequency f ′ high.

FIG. 4 illustrates the relationship between the turn-off time and the signal TDET. Further, FIG. 5 shows the relationship between the oscillation frequency f ′ and the timer operating time with respect to the turn-off time. FIG. 6 shows the relationship between the output signal of the timer circuit 32 and the lighting waveform of the high pressure discharge lamp 5.

In the above embodiment, the boost DC power supply circuit 3
Although a flyback DC / DC converter was used for the
A C converter can be used. Further, the inverter circuit 4 does not have to be a full bridge type, and other inverter circuits such as a half bridge type can be used. Further, the timer circuit 32 may have any configuration as long as it can set the time of one cycle or more of the oscillation frequency f ′. In addition, something other than a resistor can be used to detect the voltage or current with respect to the lamp load. In addition, the switch element is E
A semiconductor element other than FT can be used. Instead of using the FET or the pulse transformer as the starting means of the discharge lamp, a discharge gap or the like can be used.

Although the step-up DC power supply circuit 3 is controlled in the above embodiment, the inverter circuit 4 may be controlled or the output of the lamp current supply means may be controlled. Furthermore, 400H
Although the high-pressure discharge lamp 5 was lit with a rectangular wave voltage of a low frequency of about z, it is also applicable to high-frequency lighting as long as the high-pressure discharge lamp 5 does not cause harmful phenomena such as electrophoresis and acoustic resonance. it can.

[0032]

As described above, according to the present invention, the operating frequency of the inverter circuit is changed based on the extinguishing time at the time of starting the high pressure discharge lamp, so that the high pressure discharge lamp can be smoothly transitioned to the arc discharge state. As a result, it is possible to obtain a discharge lamp lighting device having good starting characteristics without extinguishing.

[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 a block diagram of a main part of a discharge lamp lighting device according to an embodiment of the present invention.

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

FIG. 4 is an output waveform diagram of a turn-off time detection circuit according to an embodiment of the present invention.

FIG. 5 is an operation characteristic diagram of a timer circuit according to an embodiment of the present invention.

FIG. 6 is a waveform chart of each part in the lighting operation of the discharge lamp lighting device according to the embodiment of the present invention.

FIG. 7 is an electric circuit diagram of a conventional discharge lamp lighting device.

FIG. 8 is a waveform diagram of a lamp voltage / lamp current of a conventional discharge lamp lighting device.

FIG. 9 is a waveform diagram of the re-ignition voltage of the conventional discharge lamp lighting device.

[Explanation of symbols]

 3 step-up DC power supply circuit 4 inverter circuit 5 high-pressure discharge lamp 8 starting circuit 28 lighting control circuit 29 extinguishing time detection circuit 31 frequency control circuit 32 timer 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 a rectangular wave output to a high-pressure discharge lamp, and an output voltage and an output current of the step-up DC power supply circuit are detected. And a lighting control circuit for controlling lighting of the high pressure discharge lamp. The lighting control circuit detects the extinguishing time of the high pressure discharge lamp at the time of start-up to change the operating frequency of the inverter circuit for a period of one cycle or more. Discharge lamp lighting device, which is equipped with a protection circuit.