JP2000323289A - Driving method for discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To elongate the life and improve the efficiency by alternately repeating operations of continuously impressing pulse voltage at the same polarity for a plurality of times and then continuously impressing it to the other same polarity at plurality of times, at least, between a pair of electrodes. SOLUTION: A pulse voltage from a pulse generating means 1 is distributed to two or more pulses impressed continuously to the same polarity by changeover of a switch at a prescribed period and fed to lighting circuits A, B 3, 4 composed of FET 5, 6, 6, resonant capacitors 7, 8, and a transformer 9 respectively. The pulsed voltage of the inverse polarity is generated by the generation of a back electromotive force and a prescribed waveform positive and negative voltage pulses are alternately and repeatedly impressed between electrodes 11, 12 covered with, for example, a dielectric layer of a planar fluorescent lamp. This distribution can periodically change over between the positive and negative polarities of the electrodes 11, 12 without loading too much to one of them, and the period of distributing it to the positive and the negative is set to every plurality of pulses so as to reduce the power loss in a transformer or the like based on the change of the polarity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge device which emits visible light, ultraviolet light, etc., and more particularly to a discharge device used for indoor / outdoor illumination, display, or a light source for a liquid crystal display backlight. It relates to a driving method.

[0002]

2. Description of the Related Art There are various methods for driving a light source using discharge, for example, a fluorescent lamp for illumination or display, a flat discharge device, or the like. A conventional method of driving an inverter for lighting a liquid crystal backlight is disclosed in, for example, Japanese Patent Application Laid-Open No. 63-11096.
As shown in FIG. 2, the fluorescent lamp is turned on using a sine wave of several tens of kHz. For the discharge tube, a cold cathode or hot cathode fluorescent lamp having a tube diameter of about 3 to 6 mm is used, for example, mercury and argon are sealed inside the discharge tube, and ultraviolet rays generated by discharge excite the phosphor, It emits light and illuminates the liquid crystal panel to display characters and images.

A general lighting lamp has a commercial frequency of 5
It is common to turn on at 0 or 60 Hz, but some lamps turn on at tens of kHz.

A method for driving a flat lamp is described in, for example, Japanese Patent Application Laid-Open No. 9-199285.
Lighting is performed using a pulse voltage of kHz, and FIG. 3 shows an example of the pulse voltage. (A) in the figure
The pulse is only on the positive voltage side, and (b) in the figure is a pulse that is alternately divided into positive and negative for each pulse.

[0005]

However, the discharge device using the above driving method has a problem that the light emission efficiency is reduced and the power consumption is increased particularly when the diameter of the discharge tube is reduced.

In a flat fluorescent lamp, when a unipolar pulse is applied, the phosphor near the electrode on the negative polarity side is more severely degraded than the phosphor near the electrode on the positive polarity side due to collision of cations, resulting in a short life. There was a problem of becoming. As a countermeasure against the deterioration of the phosphor near the electrode on the negative polarity side, there is a method of applying a pulse voltage alternately divided into positive and negative for each pulse. However, there is a problem that power efficiency in a transformer or the like causes a reduction in circuit efficiency. .

An object of the present invention is to provide a method of driving a discharge device which has been made to solve the above-mentioned problem and has a long life and high efficiency.

[0008]

According to the present invention, the above object is achieved by the following constitution.

(1) At least one pair of electrodes is provided,
In a discharge device for applying a pulse voltage between the electrodes,
A method for driving a discharge device, characterized in that an operation of continuously applying two or more pulse voltages of the same polarity and subsequently applying two or more pulse voltages of another same polarity is alternately repeated.

(2) In a discharge device in which at least one pair of electrodes is provided outside the discharge space and applies a pulse voltage to the electrodes, the pulse voltage is continuously applied to the same polarity for two times.
A method for driving a discharge device, characterized in that an operation of applying two or more successively of the same polarity is alternately repeated after applying more than one.

(3) At least one pair of electrodes is provided, and in the discharge space, either a rare gas or mercury is sealed alone or as a mixture of two or more types, and a pulse voltage is applied to the electrodes. In the discharge device having means for applying a pulse voltage, the operation of continuously applying two or more pulse voltages having the same polarity and then continuously applying two or more pulse voltages having the same polarity is alternately repeated. Driving method of discharge device.

(4) At least one pair of electrodes is provided, the electrodes are covered with a dielectric layer, and the discharge space is filled with a rare gas or mercury alone or as a mixture of two or more kinds. A pulse light source and a discharge device having means for applying a pulse voltage to the electrode, applying two or more pulse voltages to the same polarity continuously, and then applying two or more pulses to the other same polarity. A driving method for a discharge device, characterized by alternately repeating the operation of applying the voltage.

(5) An illuminating device using the discharge device driving method according to any one of (1) to (4).

(6) A liquid crystal display device using the method for driving a discharge device according to any one of (1) to (4).

By using such a driving method,
Both effects of high efficiency by applying a plurality of pulses continuously with the same polarity and prolonging the life by inverting the polarity of pulses applied at a relatively long cycle can be obtained.

[0016]

FIG. 1 is a circuit diagram showing one embodiment of a method for driving a discharge device according to the present invention. In the figure, 1 is a pulse generating means, 2 is a switch means, and 3 is a lighting circuit A, which comprises an FET 5, a resonance capacitor 7, and a transformer 9. Reference numeral 4 denotes a lighting circuit B, which includes an FET 6, a resonance capacitor 8, and a transformer 9. The lighting circuit A is, for example, a circuit that generates a negative voltage pulse, and the lighting circuit B is
The lighting circuit A is a circuit for generating, for example, a positive voltage pulse having the opposite polarity. Reference numeral 10 denotes a discharge lamp. The discharge lamp 10 is provided with, for example, electrodes 11 and 12 covered with a dielectric layer.
A flat fluorescent lamp in which either a rare gas or mercury is used alone or a mixture of two or more is sealed.

FIG. 2 is an operation explanatory diagram of the circuit diagram of FIG. Pulse voltage (a) generated by pulse generating means 1
Is sent to the switch means 2. In the switch means 2,
The switch is switched at the cycle shown in (b), and the pulse of (a) is divided into two or more pulses applied continuously with the same polarity as shown in (c) and (d), and (d) is a lighting circuit. A and (c) are supplied to the lighting circuit B. The pulse (c) supplied to the lighting circuit B is input to the gate of the FET 6, and the FET 6 is turned on during a period when the voltage of the pulse (c) is high.
Then, the FET 6 is turned off during a low voltage period. Similarly, the pulse (d) supplied to the lighting circuit A is input to the gate of the FET 5, and during a period when the voltage of the pulse (d) is high,
ET5 is turned on, and FET5 is turned off during a low voltage period.

As described above, the pulses (c) and (d) cause F
When the ET 5 and the FET 6 are turned on / off, a voltage waveform shown in FIG. 2E is generated on the primary side of the transformer 9. The waveform in FIG. 2E is connected to the drain of the FET 5 among the primary terminals of the transformer 9 with reference to the terminal 14 connected to the drain of the FET 6 among the primary terminals of the transformer 9. 3 shows a voltage waveform of a terminal 15.

In FIG. 2, when the voltage of the pulse (c) attains a high voltage state at the time (I), the FET 6 is turned on.
Then, the terminal 14 becomes almost the same potential as the 0 [V] potential. The number of turns between the terminals 15 and 16 and between the terminals 16 and 14 of the transformer 9 are the same. The midpoint 16 of the transformer 9 is the DC power supply 1
3 has the same potential as the voltage E, and the terminal 15-
Since the number of turns is the same between 16 and 16-14, the terminal 1
5 has a voltage of 2E.

While the voltage of the pulse (c) is in the high voltage state, the terminal 15 keeps the voltage of 2E, but the voltage of the pulse (c) changes to the low voltage state at the time of FIG.
Abruptly changes from the ON state to the OFF state, a back electromotive voltage is generated by the action of the primary side inductance of the transformer 9. Then, as shown in FIGS. 2 (e) and (II), (I) to (I)
A pulse-like voltage of the polarity opposite to the polarity at the time of I) is generated. The pulse-like voltage waveform generated at this time is determined by the inductance of the transformer primary side and the capacitance of the resonance capacitors 7 and 8, and the resonance attenuates with time,
Eventually, the potential difference between the terminal 15 and the terminal 14 disappears.

Next, at the time of (III), the pulse (c)
Is high, a voltage of 2E is generated at the terminal 15 in the same manner as the operation at the time (I), and the operations (I) to (II) are repeated thereafter.

Next, at the time (IV), the FET 5 is turned on, so that the terminal 15 becomes 0 [V] potential. At that time,
A voltage of 2E is generated at the terminal 14. (E) is terminal 14
Since the voltage waveform of the terminal 15 is based on the reference voltage, the terminal 15 has a voltage waveform lower by 2E than the terminal 14.

The times of (V) to (VI) are (II) to (III)
This is the time when the back electromotive voltage appears as in the case of.

As described above, according to the configuration of FIG.
A voltage waveform as shown in FIG. 2E appears on the primary side of the transformer 9, and the waveform of FIG.
A voltage waveform boosted at a magnification corresponding to the next turn ratio is generated.

FIG. 2F shows a waveform on the secondary side. (F)
In step (I)-(II), the boosted voltage appearing on the secondary side during the period when the FET 5 or 6 is ON is, for example, 500 [V], which is lower than the discharge starting voltage. Set the primary-secondary turns ratio. The starting voltage required for lighting is obtained by a back electromotive voltage of, for example, about 2500 [V] generated at the moment when the FET 5 or 6 transitions from ON to OFF, such as at (II) or (V).

When the discharge lamp is turned on using the waveform of (f), the positive and negative polarities of the electrodes are switched periodically by dividing the pulses into positive and negative, and a large load is applied to only one side of the electrodes. Is eliminated, resulting in a longer life. In addition, by setting a plurality of positive / negative periods instead of one pulse, power loss in a transformer or the like caused by a change in polarity can be reduced, and high efficiency can be achieved.

In the present invention, a flat fluorescent lamp whose electrodes are covered with a dielectric material is used as the discharge lamp, but other discharge lamps may be used.

In the present invention, the back electromotive voltage is used as the pulse generating means. However, a pulse voltage for starting the discharge lamp may be generated by other methods.

If the method for driving a discharge device according to the present invention is applied to a lighting device, a lighting device having a long life and high efficiency can be obtained.

When the method for driving a discharge device according to the present invention is applied to a liquid crystal display device, a liquid crystal display device having a long life and high efficiency can be obtained.

[0031]

As described above, according to the driving method of the present invention, after two or more pulse voltages applied to the electrode are continuously applied to the same polarity, two or more pulse voltages are applied continuously to the other same polarity. By repeating the operation of applying the above alternately,
A highly efficient and long-life discharge device can be obtained.

[Brief description of the drawings]

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

FIG. 2 is an operation explanatory diagram of the circuit in FIG. 1;

FIG. 3 is a voltage waveform diagram for explaining a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pulse generation means, 2 ... Switch means, 3 ... Lighting circuit A, 4 ... Lighting circuit B, 5,6 ... FET, 7,8 ... Resonant capacitor, 9 ... Transformer, 10 ... Discharge lamp, 11,12 ...
Electrodes, 13 ... DC power supply, 14, 15, 16 ... Terminals.

Claims (6)

[Claims] In a discharge device provided with at least one pair of electrodes and applying a pulse voltage between the electrodes, after continuously applying two or more pulse voltages of the same polarity,
A method of driving a discharge device, characterized by alternately repeating another operation of applying two or more voltages of the same polarity. 2. A discharge apparatus, wherein at least one pair of electrodes is provided outside a discharge space, and a pulse voltage is applied to the electrodes. A method for driving a discharge device, characterized by alternately repeating the operation of applying two or more voltages of the same polarity continuously. 3. A flat light source in which at least one pair of electrodes is provided and in which a rare gas or mercury is sealed alone or in a mixture of two or more kinds, a pulse voltage is applied to the electrodes. A discharge device having a means for applying the pulse voltage, wherein the operation of continuously applying two or more pulse voltages having the same polarity and then continuously applying two or more pulse voltages having the same polarity is alternately repeated. How to drive the device. 4. At least one pair of electrodes is provided, the electrode is covered with a dielectric layer, and a rare gas or mercury alone or a mixture of two or more kinds is sealed in a discharge space. In a discharge device having a flat light source and means for applying a pulse voltage to the electrode, two or more pulse voltages are successively applied to the same polarity, and then two or more pulses are continuously applied to the other same polarity. A driving method of a discharge device, characterized by alternately repeating an operation of applying. 5. An illuminating device using the method for driving a discharging device according to claim 1. 6. A liquid crystal display device using the method for driving a discharge device according to claim 1.