JP2007188660A - Discharge tube lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge tube lighting device capable of correcting uneven distribution of a high luminance part on a surface light source.
When the current value of one of the primary winding and the secondary winding of the balance coil T1 increases and the other current value decreases, an imbalance occurs in the magnetic flux of the balance coil T1. As a result, magnetic fluxes that are not offset are generated. In the balance coil T1, the magnetic flux acts to decrease the current value in the winding having the increased current value, and increases the current value in the winding having the decreased current value. Suppresses the deviation of the current value flowing through the winding. Then, a voltage is supplied to the transformer T2 and the transformer T3 via the balance coil T1.
[Selection] Figure 2

Description

  The present invention relates to a discharge tube lighting device for lighting a discharge tube at a high frequency, and more particularly to a multi-lamp discharge tube lighting device.

  Conventionally, a liquid crystal display device having a backlight is used for a display unit such as a computer. Among such liquid crystal display devices, in particular, in a large surface light source such as a liquid crystal television, the luminance of the surface light source is required to be uniform. For this reason, in the case of the one-side high-voltage driving method, a mechanism for detecting the current flowing in each cold cathode tube and feeding it back to the control circuit to keep the tube current constant has been provided.

  However, as the size of the cold cathode tube becomes longer, the discharge voltage of the cold cathode tube becomes higher and the impedance of the cold cathode tube also becomes higher, so that a difference in brightness occurs between the high pressure side and the low pressure side of the cold cathode tube. Realization of uniform light emission on the light emitting surface has been desired.

  Therefore, in recent years, a method of supplying a voltage from both plates of a cold cathode tube has been used by a double-sided high voltage driving method of driving a cold cathode tube by supplying current from both sides of a surface light source.

  However, it is difficult to balance the voltages supplied from both electrodes. If the balance is poor, the amount of light emitted is biased, and the luminance of the surface light source cannot be made uniform.

In view of such problems, conventionally, the output imbalance generated in the combination of the high-voltage drive system on both sides and the high-efficiency inverter circuit including two resonant circuit configurations different in phase by 180 degrees on the secondary side of the transformer is high. A surface light source discharge tube parallel lighting system that corrects output imbalance by coupling outputs through a withstand voltage current transformer and matching the resonance frequencies of these resonance circuits has been proposed (see Patent Document 1). ).
JP-A-2005-203347

  However, in a conventional surface light source discharge tube parallel lighting system, a current transformer having a high withstand voltage that can be used as a boosted voltage is used to couple the current output from the transformer secondary side through the current transformer. Had to use.

  In order to solve the conventional problems, the present invention includes a discharge tube that is turned on when voltage is supplied from both electrodes, and the phase of the voltage supplied to one electrode of the discharge tube is the same as that of the other electrode of the discharge tube. In the discharge tube lighting device, the first voltage supply means for supplying a voltage to one electrode of the discharge tube and the second voltage supply for supplying a voltage to the other electrode of the discharge tube in the discharge tube lighting device, which is opposite in phase to the supplied voltage And a current value supplied to the first voltage supply means and supplied to the first voltage supply means and the second voltage supply means when a pulse voltage generated in synchronization with the oscillation frequency of the oscillator is supplied. And equicurrent supply means for suppressing deviation from the current value supplied to the second voltage supply means.

  Further, according to the present invention, the first voltage supply means and the second voltage supply means are each constituted by a transformer, and the equal current supply means is connected to the primary side winding of the first voltage supply means from one end. While supplying current to one end, supplying current to one end of the primary side winding of the second voltage supply means, and supplying voltage from the secondary side winding of the first voltage supply means to one electrode of the discharge tube A voltage is supplied from the secondary winding of the second voltage supply means to the other electrode of the discharge tube.

  Further, according to the present invention, the equal current supply means is supplied with a pulse voltage from one end of the primary side winding and one end of the secondary side winding, and is wound between the primary side winding and the secondary side winding. The first transformer has a line ratio of 1: 1, and the first voltage supply means has one end of the primary winding connected to the other end of the primary winding of the first transformer, and a secondary winding. The transformer is configured to supply voltage from one end of the wire to one electrode of the discharge tube, and the second voltage supply means connects one end of the primary winding to the other end of the secondary winding of the first transformer. And a transformer that supplies a voltage from one end of the secondary winding to the other electrode of the discharge tube.

  Further, according to the present invention, N is a positive number, and the equal current supply means has a second transformer in which the winding ratio between the primary side winding and the secondary side winding is 1: N, the primary side winding, and 2 A third transformer having a winding ratio of 1 to N with the secondary winding, and one end of the secondary winding of the second transformer is connected to one end of the secondary winding of the third transformer; The other end of the secondary winding of the second transformer is connected to the other end of the secondary winding of the third transformer, and one end of the primary winding of the second transformer and the primary winding of the third transformer. The first voltage supply means is configured such that one end of the primary side winding is connected to the other end of the primary side winding of the second transformer so that the secondary side winding A transformer for supplying a voltage from one end to one electrode of the discharge tube. The second voltage supply means is connected to the other end of the primary side winding of the third transformer by connecting one end of the primary side winding to the secondary. Side winding Characterized in that from one end trans supplying a voltage to the other electrode of the discharge tube.

  The present invention further includes a first inductor and a second inductor, wherein the equal current supply means, the first voltage supply means, and the first inductor are connected in series in an arbitrary order, and the equal current supply means and the second voltage supply are provided. The means and the second inductor are connected in series in an arbitrary order.

  Furthermore, the present invention includes an inductor connected to the other end of the primary side winding of the first voltage supply means and the other end of the primary side winding of the second voltage supply means. .

  Furthermore, the present invention is characterized by comprising an inductor connected to the other end of the equal current supply means.

  Furthermore, the present invention is characterized by comprising a plurality of discharge tubes.

  Furthermore, the present invention is characterized in that the discharge tube used is a cold cathode tube.

  According to the discharge tube lighting device of the present invention, the current is shunted before being boosted by the transformer. Therefore, the balance coil used for the current shunting does not have to have a high breakdown voltage.

  Furthermore, a discharge tube lighting device provided with a surface light source having uniform luminance can be provided by causing the discharge tube to emit light uniformly by balancing the output with high precision by this balance coil.

  When the balance coil is configured by using a plurality of transformers, two inverter circuits can be formed, and these inverter circuits can be arranged near the electrodes of the discharge tube, respectively. By arranging in this way, the distance from the electrode to the inverter circuit can be shortened. Thereby, fluctuations in the current value due to stray capacitance generated between the electric wire and other metal portions can be suppressed, and wiring is facilitated.

  Furthermore, in this discharge tube lighting device, the timing of voltage application to the discharge tube is set by the oscillator regardless of the resonance circuit, so that the discharge tube is not affected by the parasitic capacitance of the winding or the cold cathode tube. The luminance can be maintained uniformly and stably.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a schematic diagram of a configuration example of a discharge tube lighting device in an embodiment of the present invention. The discharge tube lighting device shown in the present embodiment includes a liquid crystal panel 1a, an inverter circuit 2a, and a DC power source 3a as main components. Inside the liquid crystal panel 1a, a backlight provided with a plurality of cold cathode tubes is provided. The inverter circuit 2a includes, as main components, a transformer 4a, a transformer 4b, a balance coil 5a, and a high-frequency oscillation circuit 6a. The voltage supplied from the DC power supply 3a is boosted by the transformer 4a and the transformer 4b, so that the liquid crystal panel 1a It is supplied to a cold cathode tube arranged inside.

  The balance coil 5a supplies the current supplied from the high frequency oscillation circuit 6a to the transformer 4a and the transformer 4b. The balance coil 5a is a transformer having a one-to-one winding ratio between the primary side winding and the secondary side winding, and the current value supplied from the balance coil 5a to the transformer 4a and the balance coil 5a The deviation from the current value supplied to the transformer 4b is suppressed. A voltage is supplied to the cold cathode tubes arranged inside the liquid crystal panel 1a through the transformers 4a and 4b, and a voltage is applied to the electrodes on both sides. The voltage applied from the electrodes on both sides is different in phase by 180 degrees by setting the winding directions of the primary side winding and the secondary side winding in each transformer to be opposite.

  Next, an example of a specific circuit configuration of the discharge tube lighting device will be described with reference to the drawings. FIG. 2 is a circuit diagram showing a configuration example of the discharge tube lighting device. The inverter circuit 1 is provided with a balance coil T1, a transformer T2, and a transformer T3. The balance coil T1 is a transformer having a one-to-one winding ratio between the primary side winding and the secondary side winding.

  Here, when the current value of one of the primary side winding and the secondary side winding of the balance coil T1 increases and the other current value decreases, an imbalance occurs in the magnetic flux of the balance coil T1. , Magnetic fluxes that are not offset are generated. In the balance coil T1, the magnetic flux acts to decrease the current value in the winding with the increased current value, and increases the current value in the winding with the decreased current value. Suppresses the deviation of the current value flowing through the winding. Then, a voltage is supplied to the transformer T2 and the transformer T3 via the balance coil T1. Here, the transformer T2 and the transformer T3 have the same winding ratio.

  A voltage supplied from the power supply is supplied to the balance coil T1, the transformer T2, and the transformer T3 in synchronization with the timing when the oscillator Os1 and the oscillator Os2 are turned on / off. Here, the timing at which the oscillator Os1 and the oscillator Os2 oscillate is adjusted by an adjustment circuit (not shown) that adjusts the oscillation timing so that the tube current value of the discharge tube becomes constant. By adjusting the oscillation timing, the tube current value of the discharge tube is kept constant.

  With the above configuration, a voltage having the voltage waveform shown in FIG. 3A is generated at the contact P1, and a voltage having the voltage waveform shown in FIG. 3B is generated at the contact P2. Thereby, a voltage having a voltage waveform shown in FIG. 3C is generated between the contact P1 and the contact P2. Since the current flowing between the contact P1 and the contact P2 is kept equal in the primary side winding and the secondary side winding of the balance coil T1, the same voltage is generated from the transformer T2 and the transformer T3. Become. As a result, a voltage having the voltage waveform shown in FIG. 3D is generated at the point A on the secondary side of the transformer T2. Further, a voltage having a voltage waveform shown in FIG. 3E is generated at a point B on the secondary side of the transformer T3.

  A voltage having such a voltage waveform is supplied to both electrodes of the cold cathode tube, and voltages having opposite phases with the same amplitude are applied to the cold cathode tube from both electrodes.

  Furthermore, the distance from the electrode of the cold cathode tube to the inverter circuit is shortened, and the stray capacitance generated between the electric wire that supplies the voltage to the cold cathode tube and the metal panel that supports the liquid crystal panel 1a is reduced. It is also possible to suppress a decrease in the current value flowing from 2a to the cold cathode tube. An example of such a discharge tube lighting device is shown in FIG. In FIG. 4, an inverter circuit 2 and an inverter circuit 3 are circuits that convert a DC voltage into an AC voltage and supply the AC voltage to a cold cathode tube.

  In FIG. 2, the parts denoted by the same reference numerals as used are the same as the parts shown in FIG. 2. The transformer T4 and the transformer T5 are transformers having a winding ratio of 1: N (N is a positive number). One end of the secondary side winding of the transformer T5 and one end of the secondary side winding of the transformer T4 are connected, and the other end of the secondary side winding of the transformer T5 and the other end of the secondary side winding of the transformer T4 Is connected.

  Due to the action of the magnetic flux described above, an equal current flows through the primary side winding of the transformer T5 and the primary side winding of the transformer T4, and the secondary side winding of the transformer T5 and the secondary side winding of the transformer T4 No current flows, and the occurrence of a divergence between the current value flowing through the primary side winding of the transformer T5 and the current value flowing through the primary side winding of the transformer T4 is suppressed. As described above, even when the transformer T4 and the transformer T5 are used instead of the balance coil T1, the same operation as that of the balance coil T1 can be performed.

  Furthermore, as shown in FIG. 5, one end of the secondary side winding of the transformer T4 and the secondary side winding of the transformer T5 may be grounded.

  Further, as shown in FIG. 6, the inductor L1 may be disposed between the balance coil T1 and the transformer T2, and the inductor L2 may be disposed between the balance coil T1 and the transformer T3. The connection order of the inductor L1, the balance coil T1, and the transformer T2 is arbitrary. Further, the connecting order of the inductor L2, the balance coil T1, and the transformer T3 is arbitrary.

  Conventionally, transformers with poor coupling and high leakage flux had to be used with transformers with good coupling and low leakage flux, but it was necessary to compensate for the reduced inductance. It was. With this configuration, when a transformer having a high coupling degree and a small leakage flux is used for the transformer T2, the inductor L1 can compensate for the decrease in inductance. Further, when a transformer having a good coupling degree and a small leakage magnetic flux is used for the transformer T3, the inductor L2 can compensate for the decrease in inductance. That is, according to this configuration, it is possible to use a transformer with a good coupling degree and a small leakage flux for the transformers T2 and T3.

  Further, one end of the primary side winding of the transformer T2 is connected to one end of the primary side winding of the balance coil T1, and one end of the primary side winding of the transformer T3 is one end of the secondary side winding of the balance coil T1. When the inductor is connected to the other end of the primary side winding of the transformer T2 and the other end of the primary side winding of the transformer T3, the inductance decrease of the inductor is complemented by the inductance of the inductor. Therefore, a transformer having a good coupling degree and a small leakage flux can be used for the transformer T2 and the transformer T3.

  One end of the primary side winding of the transformer T2 is connected to one end of the primary side winding of the balance coil T1, and one end of the primary side winding of the transformer T3 is one end of the secondary side winding of the balance coil T1. When the inductor is connected to the other end of the secondary winding of the balance coil T1 connected to the other end of the primary winding of the balance coil T1, the inductance of the inductor causes the inductance to be reduced. Since the decrease is complemented, a transformer having a good coupling degree and a small leakage flux can be used for the transformer T2 and the transformer T3.

  According to the discharge tube lighting device of the present invention, it is possible to prevent unevenness of the luminance distribution in the surface light source and to emit light with a good balance. In particular, the present invention is useful when used in a backlight of a liquid crystal display device.

Schematic of the discharge tube lighting device in the embodiment The figure which shows the structural example of the discharge tube lighting device in an Example The wave form diagram which shows the operation | movement of the discharge tube lighting device in an Example The figure which shows the structural example of the discharge tube lighting device in an Example The figure which shows the structural example of the discharge tube lighting device in an Example The figure which shows the structural example of the discharge tube lighting device in an Example

Explanation of symbols

1, 2, 3 Inverter circuit T1 Balance coils T2, T3, T4, T5 Transformers Os1, Os2 Oscillators P1, P2, P3, P4 Contacts A, B Points L1, L2 Inductors

Claims (9)

A discharge tube that is lit by being supplied with voltage from both electrodes, the phase of the voltage supplied to one electrode of the discharge tube is opposite to the phase of the voltage supplied to the other electrode of the discharge tube, In the discharge tube lighting device, the first voltage supply means for supplying voltage to one electrode of the discharge tube, the second voltage supply means for supplying voltage to the other electrode of the discharge tube, and the oscillation frequency of the oscillator When the generated pulse voltage is supplied, current is supplied to the first voltage supply means and the second voltage supply means, and the current value supplied to the first voltage supply means and the second voltage supply means A discharge tube lighting device comprising: an equal current supply unit that suppresses a deviation from a current value supplied to the battery. The first voltage supply means and the second voltage supply means are each configured by a transformer, and the equal current supply means is connected from one end to one end of the primary side winding of the first voltage supply means. While supplying a current, a current is supplied to one end of the primary side winding of the second voltage supply means, and a voltage is supplied from the secondary side winding of the first voltage supply means to one electrode of the discharge tube. The discharge tube lighting device according to claim 1, wherein a voltage is supplied from the secondary winding of the second voltage supply means to the other electrode of the discharge tube. The equal current supply means is supplied with the pulse voltage from one end of the primary side winding and one end of the secondary side winding, and the winding ratio of the primary side winding to the secondary side winding is 1. A first transformer that is a pair, wherein one end of the primary side winding is connected to the other end of the primary side winding of the first transformer, and one end of the secondary side winding. The second voltage supply means connects one end of the primary side winding with the other end of the secondary side winding of the first transformer. The discharge tube lighting device according to claim 2, further comprising a transformer that supplies a voltage from one end of the secondary winding to the other electrode of the discharge tube. N is a positive number, and the equal current supply means includes a second transformer having a winding ratio of 1: N between the primary side winding and the secondary side winding, a primary side winding, and a secondary side winding. And a third transformer having a winding ratio of 1 to N, one end of the secondary winding of the second transformer is connected to one end of the secondary winding of the third transformer, and the second transformer The other end of the secondary winding of the transformer is connected to the other end of the secondary winding of the third transformer, and one end of the primary winding of the second transformer and the primary winding of the third transformer. The pulse voltage is supplied from one end of the wire, and the first voltage supply means is configured such that one end of the primary side winding is connected to the other end of the primary side winding of the second transformer. A transformer for supplying a voltage from one end of the winding to one electrode of the discharge tube, wherein the second voltage supply means has one end of the primary winding wound on the primary winding of the third transformer; Of being connected to the other end is trans supplying a voltage to the other electrode of the discharge tube from one end of the secondary winding, the discharge tube lighting apparatus according to claim 2, characterized in that. A first inductor and a second inductor, wherein the equal current supply means, the first voltage supply means and the first inductor are connected in series in an arbitrary order; the equal current supply means and the second voltage supply means; The discharge tube lighting device according to any one of claims 1 and 2, wherein the second inductor is connected in series in an arbitrary order. 3. An inductor connected to the other end of the primary side winding of the first voltage supply means and the other end of the primary side winding of the second voltage supply means. The discharge tube lighting device according to 1. The discharge tube lighting device according to claim 2, further comprising an inductor connected to the other end of the equal current supply means. The discharge tube lighting device according to claim 1, comprising a plurality of the discharge tubes. The discharge tube lighting device according to any one of claims 1 to 8, wherein the discharge tube is a cold cathode tube.

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