JPH0822894A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To accelerate a moving fringe at the potential difference of oscillating voltages to produce the effect of preventing fringed emission that cannot be recognized by the human eye by making the primary windings of a voltage step-up transformer asymmetrical. CONSTITUTION:An inverter 4 is connected to the middle point (d) of the primary winding 10-1 of the voltage step-up transformer 10 of a push-pull inverter from a DC power supply 3 and the power line of an input terminal (a) via a constant current inductor 5. The inverter is connected to collectors at both ends of each switching transistor 6, 7 via the primary windings of the transformer, and a resonant capacitor 9 is connected between both ends of each primary winding. The feedback winding of the voltage step-up transformer 10 is connected to the base of each switching transistor 6, 7. Preferably the primary windings of the voltage step-up transformer 10 differ in the number of turns by one or two. A discharge lamp 2 is connected via a ballast capacitor 12 to a secondary winding 10-2 as a load.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot cathode type and a cold cathode type small diameter fluorescent lamp lighting device, and more particularly to a backlight lighting device for a liquid crystal display device.

[0002]

2. Description of the Related Art In order to prevent striped light emission of a discharge lamp (lamp) at low temperature and at the beginning of lighting, the lamp voltage at low temperature and at the beginning of lighting may be asymmetrical. Many measures have been taken such as inserting a parallel circuit of a diode and a resistor as shown in FIG. 1 into the lamp.

[0003]

This conventional striped light emission countermeasure method requires the addition of a separate circuit to prevent the striped light emission, and the increase in the number of circuit element parts and the substrate of the lighting circuit resulting therefrom. This was a cause of increase in mounting area and price.

An object of the present invention is to provide a lighting device capable of taking measures without inserting a striped light emission preventing circuit which has been conventionally required.

[0005]

In order to achieve the above object, the present invention relates to a hot cathode type small-diameter fluorescent lamp lighting device, and more particularly to a constituent element of a lighting circuit of a backlight inverter of a liquid crystal display device. The number of turns of each of the push-pull resonance primary side windings of the voltage boosting transformer, which is one of the
2 turns, the other is 11 with a winding diameter of φ0.2
Turn and change the number of turns on the primary side.

[0006]

For example, each of primary devices for push-pull resonance of a voltage boosting transformer, which is one of the components of a lighting circuit of a small-sized fluorescent lamp of a hot cathode type, in particular, a backlight inverter of a liquid crystal display device. By making the windings asymmetrical, the moving fringes generated by the potential difference of the oscillating voltage are accelerated so that they cannot be seen by human eyes, so that the moving fringes cannot be visually recognized.

On the other hand, if the potential difference is too large, a cataphoresis phenomenon, which is basically present in fluorescent lamps, occurs, and mercury in the lamp tube approaches one side, and light emission is about half, which is not preferable. Therefore, the difference in the number of turns is most preferably about 1 to 2 turns.

[0008]

FIG. 2 is a circuit diagram of a discharge lamp lighting device for a cold cathode lamp according to an embodiment of the present invention. In the figure, a power source 3 is connected to a DC power source and is connected to a high frequency lighting circuit via a constant current inductor 5. The inverter 4 is a push-pull type inverter and is composed of a pair of switching transistors 6 and 7, a bias resistor 8, a resonance capacitor 9 and a voltage boosting transformer 10 which is a feature of the present invention.

In this case, the inverter 4 includes a constant current inductor 5 from the DC power source 3, the power source line of the input terminal a.
Is connected to the midpoint d of the primary winding 10-1 of the voltage boosting transformer 10 via a transformer and is connected to the collectors of both ends of the switching transistors 6 and 7 via the transformer primary side winding to cause resonance between both ends of the primary winding. The capacitor 9 is connected, and the feedback winding of the voltage boosting transformer is connected to the bases of the switching transistors 6 and 7. Then, the secondary winding 10-2 of the voltage boosting transformer is connected as a load to the discharge lamp 2 via the ballast capacitor 12.

By providing a preheating circuit 11 for supplying a filament current to the electrodes of the hot cathode lamp at both ends of the lamp 2 of FIG. 2, the same effect can be obtained as a hot cathode lamp lighting circuit.

[0011]

In the past, measures were taken such as inserting a parallel circuit of a diode and a resistor into a lamp to prevent striped light emission, but according to the present invention, it is not necessary to add the number of parts of circuit elements. Therefore, it is possible to reduce the board mounting area and the cost of the discharge lamp lighting circuit.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a conventional moving fringe countermeasure.

FIG. 2 is a circuit diagram of a discharge lamp lighting device for a cold cathode lamp according to an embodiment of the present invention.

[Explanation of symbols]

 1 ... Circuit for countermeasure against moving stripes, 2 ... Discharge lamp.

Claims (1)

[Claims] 1. A high-frequency lighting circuit including a voltage boosting transformer and two switching elements connected to both ends of a primary side winding of the transformer to push-pull drive the primary winding. A device for lighting a discharge lamp, wherein the number of turns of each push-pull resonance winding of the primary winding of the transformer is asymmetric.