JP2005071681A - High voltage transformer and electric-discharge lamp driving circuit using this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To output high voltage corresponding to a long electric-discharge lamp maintaining conventional insulation performance in a secondary side coil of a high voltage transformer. <P>SOLUTION: The AC voltage applied to a primary winding 150 is raised to generate prescribed AC voltage in secondary high-voltage windings 110a, 110b. The secondary high-voltage windings 110a, 110b are provided with two independent high voltage windings (110a, 110b), winding directions of high voltage windings (110a, 110b) are opposite to each other, and phases of output voltages of high voltage windings (110a, 110b) are shifted to each other by 180 degrees. Thereby, the applied voltage to the electric-discharge lamp to be connected is substantially increased. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to, for example, a high-pressure transformer used in a lighting circuit for a discharge lamp for a backlight in a liquid crystal display panel and a discharge lamp driving circuit using the same, and more particularly to simultaneously lighting a plurality of discharge lamps used in a DC / AC inverter circuit. The present invention relates to a high-pressure transformer and a discharge lamp driving circuit using the same.

  2. Description of the Related Art Conventionally, for example, it has been known that several cold cathode discharge lamps (hereinafter referred to as CCFLs) are simultaneously discharged and lit for backlights of various liquid crystal display panels used in notebook computers and the like. Yes. In this way, by using several CCFLs or more, it is possible to meet demands for higher brightness and uniform illumination of the liquid crystal display panel.

  As a circuit for lighting this type of CCFL, an inverter circuit is generally used which starts a discharge by converting a DC voltage of about 12V into a high frequency voltage of about 60 kHz and about 2000 V using a high voltage transformer. In addition, after the start of the discharge, the inverter circuit controls the high frequency voltage to be lowered to about 800 V necessary for maintaining the discharge of the CCFL.

  As a high-voltage transformer (inverter transformer) used in such an inverter circuit, for example, one mounted on a discharge lamp driving circuit as shown in FIG. 6 described in Patent Document 1 below is known.

  This discharge lamp drive circuit is configured to apply a high voltage generated by a high voltage winding 210 as a secondary winding to the CCFL 220 via a connection connector 230. Note that the phase of the output voltage of the high voltage winding 210 is in phase with the phase of the input voltage of the primary winding 240 (see FIG. 7A) as shown in FIG. b)), or a state (not shown) that is in reverse phase to the phase of the input voltage of the primary winding 240.

  It is also known that two high-voltage windings 210 are provided in parallel, each connected to a CCFL, and two CCFLs can be turned on by one high-voltage transformer.

JP-A-5-89989

  However, along with the increase in size of today's liquid crystal display panels, it has become necessary to use a longer CCFL for the backlight than the conventional CCFL. It is demanded to make it. Therefore, it is possible to increase the number of turns of the secondary winding and increase the step-up ratio to further increase the output voltage on the secondary side. It is considered difficult to increase the voltage to about 1000 V without significant increase in manufacturing cost, and it has been practically difficult to drive a long CCFL by a conventional method.

  The present invention has been made in view of such circumstances, and it is possible to output a high voltage at a low cost corresponding to a long discharge lamp while maintaining the conventional insulation performance in the secondary winding. An object is to provide a high-voltage transformer. Another object of the present invention is to provide a discharge lamp driving circuit using such a high-pressure transformer.

The high-voltage transformer of the present invention capable of achieving such an object is used for lighting a discharge lamp that boosts an AC voltage applied to a primary winding and generates a predetermined AC voltage in a secondary winding. In the high voltage transformer of
The secondary winding portion includes two high-voltage windings that generate AC voltages independent of each other, and the winding directions of the high-voltage windings are opposite to each other so that the phases of the output voltages are shifted from each other by 180 degrees. It is comprised so that it may become. It is characterized by the above.

  Moreover, it is preferable that the number of turns of the two high-voltage windings is substantially the same.

  In the high-voltage transformer of the present invention, it is preferable that the primary winding and the secondary winding are packaged integrally.

  The discharge lamp driving circuit of the present invention is characterized in that the high-voltage transformer is mounted.

  According to the high-voltage transformer of the present invention, the secondary side winding is constituted by two independent high-voltage windings, and the winding directions of the high-voltage windings are opposite to each other. Are shifted from each other by 180 degrees.

  Therefore, by connecting the high-voltage windings to both terminals of the discharge lamp, it is possible to apply a voltage twice as high as that of a single high-voltage winding. A sufficient lighting start voltage can be supplied.

  In addition, since the output voltage of each high-voltage winding is the same as the conventional one, there is no need to improve the insulation performance in the secondary winding, and the cost increase can be suppressed.

  Further, by connecting one long discharge lamp to the two high-voltage windings, it is possible to obtain the same brightness as when two discharge lamps are connected as in the prior art. In this case, the number of connection connectors can be reduced to one, and the cost can be reduced. In particular, when a long discharge lamp such as a U-shape is used as a backlight for a liquid crystal display device or the like, it can have an illumination function equivalent to two straight tube CCFLs, so the number of connection connectors is reduced. In addition, the manufacturing cost can be reduced.

  Further, the voltage applied to the discharge lamp can be increased efficiently by making the number of turns of the two high-voltage windings substantially the same.

  Further, by integrally packaging the secondary side winding composed of the primary side winding and the two high voltage windings, the assembling work of the liquid crystal display device and the like can be facilitated, and the manufacturing cost can be reduced.

  In addition, according to the discharge lamp driving circuit of the present invention, it is possible to enjoy the effects of the high-voltage transformer described above.

  Hereinafter, a high voltage transformer according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  Fig.5 (a) is a top view which shows the inside of the high voltage transformer based on Embodiment of this invention, FIG.5 (b) is a longitudinal cross-sectional view of this high voltage transformer.

  The high-voltage transformer of the present embodiment is an inverter transformer used in a DC / AC inverter circuit. As shown in FIGS. 5A and 5B, a core 1a made of a pair of upper and lower ferrites facing each other, The primary winding 2 and the two secondary high-voltage windings 3a and 3b are arranged between 1b. The primary winding 2 is wound in a state of being fitted in a groove on the inner wall surface of the lower core 1b, while two secondary high-voltage windings arranged inside the primary winding. The wires 3a and 3b are wound around each of the bobbins 4a and 4b having both the left and right hooks.

Each component constituting the high-voltage transformer such as the primary winding 2 and the secondary high-voltage windings 3a and 3b is housed in a case 5 and packaged.
Further, as shown by arrows in FIG. 5A, the secondary high-voltage windings 3a and 3b have their winding directions opposite to each other, so that the secondary high-voltage windings 3a and 3b The output voltages are configured to be 180 degrees out of phase with each other.

<First Embodiment>
FIG. 1 is a circuit diagram showing a first embodiment of a discharge lamp driving circuit equipped with a high-voltage transformer of the present invention.

  As shown in FIG. 1, the discharge lamp driving circuit according to the first embodiment uses a Royer oscillation circuit 40 on the primary side, and two secondary high-voltage windings 10a and 10b on the secondary side. However, the winding directions are opposite to each other, and one long U-shaped CCFL 20 is connected to both the secondary high-voltage windings 10a and 10b via the connection connector 30. . The CCFL to be connected may have another shape.

  In the discharge lamp driving circuit having such a configuration, the Royer oscillation circuit 40 supplied with a voltage from the DC power supply line (Vcc) generates an AC voltage. The high-voltage transformer boosts this AC voltage input to the primary-side winding 50 and generates a high-voltage AC voltage from the two secondary-side high-voltage windings 10a and 10b. Here, the number of turns of the two secondary high-voltage windings 10a and 10b is set to be equal to each other. Further, one secondary high voltage winding 10a and the other secondary high voltage winding 10b are both grounded at the end of the high voltage winding.

  Further, as shown in FIG. 2, the phase of the output voltage (b) of one secondary side high-voltage winding 10a is in phase with the phase of the input voltage (a) of the primary side winding 50, and the other The phase of the output voltage (c) of the secondary side high voltage winding 10b is opposite to the phase of the input voltage (a) of the primary side winding 50 by 180 degrees. Thus, since the phases of the output voltages (b) and (c) of the two secondary high-voltage windings 10a and 10b are shifted from each other by 180 degrees, the applied voltage (d) to the CCFL 20 The difference between the output voltages of the high-voltage windings 10a and 10b is such that an output voltage twice that of the conventional discharge lamp drive circuit can be obtained, and the long U-shaped CCFL 20 can be driven to light.

Thus, for example, when the CCFL 20 is used as a backlight of a liquid crystal display panel, the same lighting effect as that provided by arranging two conventional straight tube CCFLs can be obtained. Furthermore, since only one connection connector 30 is required, the manufacturing cost can be reduced.
2 (a), (b), (c), and (d) show the voltage phases at the positions (a), (b), (c), and (d) in FIG. 1, respectively. Yes.

<Second Embodiment>
FIG. 3 is a circuit diagram showing a second embodiment of a discharge lamp driving circuit equipped with the high-voltage transformer of the present invention.

  As shown in FIG. 3, the discharge lamp driving circuit according to the second embodiment uses a full bridge circuit 140 on the primary side, and two secondary high-voltage windings 110a and 110b are provided on the secondary side. However, the winding directions are opposite to each other, and a single long straight tubular CCFL 120 is connected to both the secondary high-voltage windings 110a and 110b. The CCFL to be connected may have another shape.

  The full bridge circuit 140 and the lighting control unit 160 connected to the primary side of the high voltage transformer constitute an inverter circuit.

  In the discharge lamp driving circuit having such a configuration, the full bridge circuit 140 supplied with a voltage from the DC power supply line (Vcc) generates an AC voltage (rectangular wave shape). The high voltage transformer boosts this AC voltage input to the primary side winding 150 to generate a high voltage AC voltage from the two secondary side high voltage windings 110a and 110b. In the second embodiment as well, the number of turns of the two secondary high-voltage windings 110a and 110b is set to be equal to each other as in the first embodiment. Further, one secondary side high voltage winding 110a and the other secondary side high voltage winding 110b are both grounded at the end of the high voltage winding.

  Further, as shown in FIG. 4, the phase of the output voltage (b) of one secondary side high voltage winding 110a is in phase with the phase (rectangular wave) of the input voltage (a) of the primary side winding 150. The phase of the output voltage (c) of the other secondary side high voltage winding 110b is opposite to the phase (rectangular wave) of the input voltage (a) of the primary side winding 150 by 180 degrees. Yes. Thus, since the phases of the output voltages (b) and (c) of the two secondary high-voltage windings 110a and 110b are shifted from each other by 180 degrees, the applied voltage (d) to the CCFL 120 is The difference between the output voltages of the high-voltage windings 110a and 110b is such that an output voltage that is twice that of the conventional discharge lamp driving circuit can be obtained.

Thus, for example, when the CCFL 120 is used as a backlight of a liquid crystal display panel, it is possible to cope with a large screen rather than using a CCFL having a conventional length. Furthermore, since only one connection connector (not shown) is required, a significant increase in manufacturing cost can be avoided.
4 (a), (b), (c), and (d) show the voltage phases at the positions (a), (b), (c), and (d) in FIG. 3, respectively. Yes.

<Other embodiments>
The high-voltage transformer of the present invention is not limited to an inverter transformer, and can be applied to other various transformers.

  In addition, the arrangement of the primary winding and the secondary winding is not limited to that shown in FIG. 5, but a closed magnetic circuit structure type with an E-shaped core facing or an I-shaped core opened. Various types of arrangements known in the art, such as a magnetic path structure type, can be used.

  Further, the turns ratio of the two high-voltage windings constituting the secondary winding portion is not limited to 1: 1, and other winding ratios can be appropriately selected.

  The core used for the high-voltage transformer is preferably formed of ferrite, but other materials such as permalloy, sendust, iron carbonyl, etc. can be used, and a dust core obtained by compression molding these fine powders is used. You can also

  Further, the discharge lamp is not limited to the CCFL, and other discharge lamps such as a fluorescent lamp can be used.

  Further, the shape of the discharge lamp is not limited to a straight tube type or a U-shape, and a bent tube having a plurality of bent portions in a folded shape, a spiral tube, or the like can be used. By using a bent tube or the like, when used as a backlight discharge lamp or the like of a liquid crystal display device, the number of the lamps used can be reduced to obtain the same brightness as the conventional one.

The circuit diagram which shows the discharge lamp drive circuit which concerns on 1st Embodiment carrying the high voltage | pressure transformer of this invention Explanatory drawing of the input-output voltage in each part of the discharge lamp drive circuit which concerns on 1st Embodiment shown in FIG. The circuit diagram which shows the discharge lamp drive circuit which concerns on 2nd Embodiment carrying the high voltage | pressure transformer of this invention Explanatory drawing of the input-output voltage in each part of the discharge lamp drive circuit which concerns on 2nd Embodiment shown in FIG. The top view (a) and longitudinal section (b) which show the inside of the high voltage transformer concerning the embodiment of the present invention Circuit diagram showing a discharge lamp drive circuit equipped with a conventional high-voltage transformer Explanatory diagram of input / output voltage in each part of a discharge lamp drive circuit equipped with a conventional high-voltage transformer

Explanation of symbols

1a, 1b Core 2 Primary winding 3a, 3b Secondary winding (secondary high voltage winding)
4a, 4b Bobbin 5 Case 10a, 10b Secondary winding (secondary high voltage winding)
20 CCFL (Cold Cathode Discharge Lamp)
30 connection connector 40 Royer oscillation circuit 50 primary winding 110a, 110b secondary winding (secondary high voltage winding)
120 CCFL (Cold Cathode Discharge Lamp)
140 Full Bridge Circuit 150 Primary Side Winding 160 Lighting Control Unit 210 Secondary Side Winding (Secondary Side High Voltage Winding)
220 CCFL (Cold Cathode Discharge Lamp)
230 Connector 240 Primary winding

Claims (4)

In a high voltage transformer for lighting a discharge lamp that boosts an alternating voltage applied to a primary winding and generates a predetermined alternating voltage in a secondary winding,
The secondary winding portion includes two high-voltage windings that generate AC voltages independent of each other, and the winding directions of the high-voltage windings are opposite to each other so that the phases of the output voltages are shifted from each other by 180 degrees. A high-voltage transformer characterized by being configured as follows.   2. The high voltage transformer according to claim 1, wherein the number of turns of the two high voltage windings is substantially the same.   3. The high voltage transformer according to claim 1, wherein the primary side winding and the secondary side winding are packaged integrally.   A discharge lamp drive circuit comprising the high-pressure transformer according to any one of claims 1 to 3.

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