JPH04298995A - Lighting device for multiple light tubes - Google Patents

Abstract

PURPOSE:To surely prevent generation of a flicker while contriving miniaturization and type thinness of a device. CONSTITUTION:A single main inverter circuit 2 constituted by using a positive feedback amplifying circuit 3 having an oscillating function and one or two or more subinverter circuits 4 constituted by using an amplifier 5 having constitution similar to partly at least constitution of the positive feedback amplifying circuit 3 further inputting partly an oscillation signal Si thereof are provided.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for multiple light tubes suitable for use as a backlight for a liquid crystal display panel in a portable computer or the like.

0002

[Prior Art] Generally, a liquid crystal display panel with a built-in backlight is used for the display section of a portable computer called a handy personal computer. multiple fluorescent tubes are used.

By the way, this type of portable computer is required to be thinner in order to improve portability. For this reason, a lighting device (inverter device) for lighting a fluorescent tube is configured with a plurality of inverter circuits to prevent the size of a transformer and the like that would occur if the lighting device were configured as a single unit.

FIG. 2 shows such a conventional lighting device 30. As shown in FIG. The lighting device 30 includes a first inverter circuit 31 and a second inverter circuit 32, each of which lights three fluorescent tubes. Each inverter circuit 31 and 32 has the same configuration,
That is, the inverter circuit 31 is configured using a positive feedback amplifier circuit 35 including a choke transformer 33 and an output transformer 34, and the inverter circuit 32 is configured using a positive feedback amplifier circuit 38 including a choke transformer 36 and an output transformer 37. As a result, it is possible to reduce the size of the transformer per inverter circuit, and also to reduce the size and thickness of the entire circuit.

[0005]

However, the conventional lighting device 30 has the following problems. That is, each of the inverter circuits 31 and 32 has variations in oscillation frequency due to differences in component characteristics, etc., but in particular, since they are constructed from products of the same lot, variations in oscillation frequency are likely to occur at frequencies that are close to each other. Therefore, even if the operating frequency is as high as 30 kHz, for example, the difference in oscillation frequency due to variations is about several tens of Hz, which causes flickering.

The present invention solves the problems that exist in the conventional technology, and provides a lighting device for multiple light tubes that can be made smaller and thinner, and can reliably prevent the occurrence of flickering. For the purpose of providing.

[0007]

[Means for Solving the Problems] The present invention provides a plurality of fluorescent tubes L.
When configuring the lighting device 1 for multiple light tubes that lights...
In particular, a single main inverter circuit 2 configured using a positive feedback amplifier circuit 3 having an oscillation function, and a positive feedback amplifier circuit 3 having the same configuration as at least a part of the positive feedback amplifier circuit 3, An amplifier 5 which receives as input a part of the oscillation signal Si of
It is characterized by comprising one (or two or more) sub-inverter circuits 4 configured using.

[0008]

[Operation] According to the lighting device 1 for multiple lamp tubes according to the present invention, there is only one main inverter circuit 2 having an oscillation function, and the other sub-inverter circuit 4 receives the oscillation signal Si oscillated from the main inverter circuit 2. It functions as a mere amplifier 5 for amplification. Therefore, the operating frequencies of the sub inverter circuit 4 and the main inverter circuit 2 are completely the same and synchronized.

Furthermore, since the amplifier 5 in the sub-inverter circuit 4 has the same configuration as at least a part of the positive feedback amplifier circuit 3 in the main inverter circuit 2, Fluctuations in brightness and the like can also be matched between the inverter circuits 2 and 4.

0010

Embodiments Next, preferred embodiments of the present invention will be described in detail with reference to the drawings.

First, the configuration of a lighting device 1 for multiple lamp tubes according to the present invention will be explained with reference to FIG.

The lighting device 1 is roughly divided into a main inverter circuit 2.
and a sub-inverter circuit 4.

The main inverter circuit 2 is constructed using a positive feedback amplifier circuit 3 having a self-oscillation function. The positive feedback amplifier circuit 3 has transistors Q1 and Q2, and the transistor Q1
, Q2 are grounded to the ground line G, and their collectors are respectively connected to both ends of the primary winding N1 of the output transformer T1. Further, a choke transformer Tc is connected to the power supply line 10, and the center tap of the primary winding N1 is connected to the output side of the choke transformer Tc. On the other hand, each base of transistors Q1 and Q2 is connected to a resistor R
1. A feedback winding Nf connected to the output side of the choke transformer Tc via R2 and provided on the output transformer T1.
is connected to each transistor Q via feedback resistors R3 and R4.
Connect to the bases of 1 and Q2 respectively. Further, a capacitor C1 is connected between the collectors of transistors Q1 and Q2. Furthermore, one end of the secondary winding N2 in the output transformer T1 is grounded, and the other end is connected to the capacitors C2, C3,
It is connected to the first output terminal 12, second output terminal 13, and third output terminal 14 via C4. In addition, the earth output terminal 11
is grounded. Three fluorescent tubes L... are connected between each output terminal 12, 13, 14 and the ground output terminal 11, respectively.

On the other hand, the sub-inverter circuit 4 has transistors Q3 and Q4, each emitter of which is grounded, and each collector connected to an output transformer T2.
are respectively connected to both ends of the primary winding M1. Further, the center tap of the primary winding M1 is connected to the output side of the choke transformer Tc, and each transistor Q3 and Q4 is connected to the output side of the choke transformer Tc.
A capacitor C5 is connected between the collectors of. On the other hand, one end of the secondary winding M2 in the output transformer T2 is grounded,
The other end is connected to the fourth output terminal 16, the fifth output terminal 17, and the sixth output terminal 18 via capacitors C6, C7, and C8, respectively. Note that the earth output terminal 15 is grounded. Then, each output terminal 16, 17, 18 and the ground output terminal 1
Between 5 and 5, there are three fluorescent tubes (similar to the main inverter circuit 2 side).
(not shown). The above configuration coincides with a part of the configuration of the positive feedback amplifier circuit 3, and constitutes an ordinary amplifier 5. Thereby, for example, variations in brightness and the like due to dynamic characteristic changes such as temperature rise are made consistent between the inverter circuits 2 and 4. And each transistor Q3, Q4
The base of is connected to both ends of the feedback winding Nf via balance resistors R5 and R6.

Next, the operation of the lighting device 1 for multiple light tubes will be explained.

First, the positive feedback amplifier circuit 3 in the main inverter circuit 2 forms a positive feedback loop with the feedback winding Nf and the feedback resistors R3 and R4, and self-oscillates. The oscillation signal (feedback signal) Si is amplified and outputted via the output transformer T1 to light the fluorescent tubes L connected to the respective output terminals 12, 13, 14. Note that the oscillation frequency is determined by the resonance frequency based on the capacitors C1, C2, C3, and C4 and the output transformer T1.

On the other hand, the oscillation signal Si is simultaneously applied to the sub-inverter circuit 4, amplified by the amplification function of the amplifier 5, outputted via the output transformer T2, and connected to each output terminal 16, 17, 18. light up the fluorescent tubes. As a result, the operating frequencies of the main inverter circuit 2 and the sub-inverter circuit 4 completely match. Note that the output balance between the main inverter circuit 2 and the sub-inverter circuit 4 can be adjusted by balance resistors R5 and R6.

The embodiments have been described in detail above, but
The invention is not limited to such embodiments. For example, two or more sub-inverter circuits may be provided. Further, although the case where the present invention is applied to a backlight of a liquid crystal display panel is illustrated, this does not preclude application to other uses. In addition, the detailed circuit configuration, quantity, etc. may be arbitrarily changed without departing from the gist of the present invention.

[0019]

As described above, the lighting device for multiple light tubes according to the present invention includes a single main inverter circuit configured using a positive feedback amplifier circuit having an oscillation function, and at least a part of the positive feedback amplifier circuit. Since the sub-inverter circuit is configured using an amplifier that has the same configuration as the configuration and inputs a part of the oscillation signal of the positive feedback amplifier circuit, the operating frequencies of the multiple inverter circuits completely match, This brings about the remarkable effect of making the device smaller and thinner and reliably preventing the occurrence of flickering.

[Brief explanation of drawings]

FIG. 1 is an electrical circuit diagram of the main parts of a lighting device for multiple light tubes according to the present invention,

[Fig. 2] Electrical circuit diagram of the main parts of a lighting device for multiple light tubes according to the conventional technology,

[Explanation of symbols]

1. Lighting device 2 Main inverter circuit 3 Positive feedback amplifier circuit 4 Sub-inverter circuit L Fluorescent tube Si oscillation signal

Claims (2)

[Claims] 1. A multi-light tube lighting device for lighting a plurality of fluorescent tubes, comprising: a single main inverter circuit configured using a positive feedback amplifier circuit having an oscillation function; and at least a portion of the positive feedback amplifier circuit. A multi-light tube comprising one or more sub-inverter circuits configured using an amplifier having the same configuration as that of the positive feedback amplifier circuit and inputting a part of the oscillation signal of the positive feedback amplifier circuit. lighting device. 2. The lighting device for multiple light tubes according to claim 1, wherein the lighting device is used for a backlight of a liquid crystal display panel.