KR20040101057A - Inverter transformer and discharge lamp lighting apparatus using the same - Google Patents

Abstract

PURPOSE: An inverter transformer and a switch for an illuminating lamp using the same are provided to prevent a short circuit by reducing a voltage applied on each node by using one inverter transformer for two or four illuminating lamps. CONSTITUTION: An inverter transformer includes one primary winding(1) and two secondary windings(2a,2b). The secondary windings are electrically coupled with the primary winding and have the same winding number to the primary wiring. Intermediate taps are extracted from each of the secondary windings. Alternatively, the inverter transformer includes first and second bobbins, one primary wiring, first and second secondary windings wound around the first bobbin, and third and fourth secondary windings wound around the second bobbin. The first through fourth secondary windings are electrically coupled with the primary wiring having identical inductances.

Description

Inverter transformer and discharge lamp lighting device using it {INVERTER TRANSFORMER AND DISCHARGE LAMP LIGHTING APPARATUS USING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device suitable for a large liquid crystal monitor having a backlight discharge lamp attached to the rear surface of a liquid crystal display panel. The present invention relates to a magnetic leakage inverter transformer capable of extracting two sets of high voltage outputs, and an inverter. A discharge lamp lighting device using a transformer.

As the magnetic leakage type two-output inverter transformer of this kind, there is one disclosed in Japanese Patent Application Laid-Open No. 2001-126937, for example. As shown in Fig. 8, this inverter transformer is provided with two secondary windings 2a and 2b of the same number of turns, which are electromagnetically coupled to one primary winding 1 with the same coupling degree. Lead wires at both ends of the secondary winding 2a are wound and soldered to the connection portions 21a and 22a of the terminals 21 and 22, respectively, and lead wires at both ends of the secondary winding 2b are respectively connected to the terminals 31 and 32. It is wound up and soldered to 31a, 32a. In the case where there are a plurality of discharge lamps, using this transformer can reduce the installation area rather than using two single-output transformers.

9 shows an example of the use of such inverter transformer T. In FIG. Discharge lamps 40a and 40b are connected to the other ends of the secondary windings 2a and 2b having one end grounded, respectively. Q1 and Q2 are push-pull switching transistors, R is a bias resistor, C is a resonant capacitor connected in parallel to the primary winding 1, 4 is a feedback winding, and 5 is used for frequency synchronization with another driving circuit. It is a synchronous winding. The intermediate tap of the primary winding 1 is connected to the input terminal 3 via the choke coil L. As shown in FIG. Then, a DC voltage is applied to the input terminal 3 to output the high frequency voltage of the sine wave to the secondary windings 2a and 2b, and to light the two discharge lamps 40a and 40b with the AC voltage in phase.

As the size of the liquid crystal monitor increases, the discharge lamp becomes longer, and when the large-screen monitor is 40 inches or more, the discharge lamp becomes a length of 85 cm or more. For example, as shown in FIG. 12, about 12 to 20 discharge lamps 40 are arranged behind the screen 6. In order to light such a long discharge lamp, a high kick-off voltage of 1800 Vrms is required, and a high voltage of 1200 Vrms or more must always be applied to the electrode of the discharge lamp even after the lighting. Since high voltage is applied, not only corona discharge occurs easily but also electric field noise may occur in the liquid crystal panel.

The backlight module using a long discharge lamp has a large capacity and a large leakage current. As a result, as shown by the broken line A in FIG. 11, the brightness difference a of the left end and the right end of a discharge lamp became large, and there existed a problem that the brightness difference a of 100 candelas generate | occur | produces at most. This luminance difference (a) appears as luminance unevenness of the liquid crystal panel.

Thus, as shown in FIG. 10, even when the two discharge lamps 40a and 40b are turned on, two inverter transformers T1 and T2 are used to apply an antiphase voltage to the electrodes at both ends of the discharge lamps 40a and 40b. Inverter circuits of double voltage driving are used. Each of the synchronous windings 5 of the inverter transformers T1 and T2 is connected to each other to synchronize in an inverted phase. In this case, the center portions of the discharge lamps 40a and 40b are alternatingly at zero potential. Since the voltage applied to the electrodes at both ends is reduced by half, the influence of the electric field is reduced, and as shown in the solid line B in FIG. 11, the luminance difference b due to the position of the discharge lamp is also reduced.

By the way, in the structure of FIG. 10, two inverter transformers of two output types are required for two discharge lamps. Moreover, since the cable which connects the synchronous windings 5 located in the distant position left and right is necessary, assembly is cumbersome and cost becomes high. In addition, when a large number of discharge lamps are turned on, since a plurality of sets of the apparatus of FIG. 10 are used, there existed a fault which the nonuniformity of phase characteristics generate | occur | produced between them.

An object of the present invention is to provide an inverter transformer capable of extracting two high voltage outputs from one inverter transformer, and a discharge lamp lighting device that is easy to assemble and uses less luminance unevenness using the inverter transformer.

1 is a plan view of an essential part showing one embodiment of an inverter transformer of the present invention;

2 is a plan view of an essential part showing another embodiment of the inverter transformer of the present invention;

3 is a circuit diagram of the inverter transformer shown in FIG. 2;

4 is a circuit diagram showing a first embodiment of a discharge lamp lighting apparatus according to the present invention;

5 is a circuit diagram of a main part similarly showing the second embodiment;

6 is a circuit diagram showing a third embodiment in the same manner;

7 is a circuit diagram of an essential part showing a fourth embodiment similarly;

8 is an essential part plan view showing one example of a conventional inverter transformer.

9 is a circuit diagram showing a configuration example of a conventional discharge lamp lighting apparatus;

10 is a circuit diagram showing another configuration example of a conventional discharge lamp lighting apparatus;

11 is a luminance distribution diagram of a discharge lamp,

12 is a rear view showing an arrangement of a conventional discharge lamp,

Fig. 13 is a rear view showing an arrangement example of a discharge lamp according to the present invention.

(Explanation of the sign)

1 primary winding

2 secondary winding

40 discharge lamp

T inverter transformer

The first inverter transformer according to the present invention includes one primary winding 1 and two secondary windings 2a and 2b of the same number of turns that are electromagnetically coupled to the primary winding 1 with the same coupling degree, It is characterized by a configuration in which an intermediate tap is derived from each of the secondary windings 2a and 2b.

The second inverter transformer according to the present invention includes four secondary windings 2a, which are electromagnetically coupled to the bobbins 20 and 30, one primary winding 1, and the primary winding 1 with the same bonding degree. 2b, 2c, and 2d, two secondary windings 2a and 2b are wound around the bobbin 20, and two secondary windings 2c and 2d are wound around the bobbin 30. . This inverter transformer is configured to be able to obtain a function equivalent to that of the first inverter transformer by connecting a part of the secondary windings to an external circuit and to easily add a discharge lamp current detection function.

Furthermore, the discharge lamp lighting device according to the present invention includes a plurality of discharge lamps 40 having electrodes at both ends of one inverter transformer, and grounds or closes the intermediate taps of the respective secondary windings 2a and 2b as they are. It is characterized by a configuration of grounding through a resistor and simultaneously connecting both ends of each of the secondary windings 2a and 2b to electrodes of different discharge lamps 40 and applying an alternating phase AC voltage to both ends of each discharge lamp.

(Example)

1 is a plan view showing one embodiment of an inverter transformer T according to the present invention. In addition, in the following drawings, the same code | symbol is attached | subjected and demonstrated to the part corresponding to a conventional example. One insulating bobbin 10 and two bobbins 20 and 30 are attached on the lower core 50 with the side surfaces facing each other. The bobbin 10 is wound around the primary winding 1 and the feedback winding in the same manner as the conventional art, and connected to the terminal 12 having the lead wire provided on the side surface. The bobbins 20 and 30 are respectively wound with secondary windings 2a and 2b of the same number of turns, which are electromagnetically coupled to the primary winding 1 with the same bonding degree.

The lower core 50 made of a magnetic body is provided with legs 51, 52, 53 protruding upwards, and elongated protrusions 54 for magnetic shunt. The leg 51 is inserted in the center of the primary winding 1, and the legs 52 and 53 are inserted in the center of the secondary windings 2a and 2b, respectively. An upper core having a flat plate shape (not shown) abuts against the legs 51, 52, 53 of the lower core 50 to form a closed path. The primary winding 1 and the secondary windings 2a and 2b are electromagnetically coupled by the pair of upper and lower cores 50. The projection 54 is located between the two secondary windings 2a and 2b and the primary winding 1, and serves to weaken the electromagnetic coupling between the windings.

This inverter transformer T differs from the conventional one shown in FIG. 8 in that the intermediate taps are derived from the secondary windings 2a and 2b, respectively. That is, the terminal 23 and the terminal 33 are additionally provided in the bobbin 20 and the bobbin 30, respectively, and the intermediate tab of the secondary winding 2a is connected to the connection part 23a of the terminal 23. The intermediate tap of the secondary winding 2b is connected to the connecting portion 33a of the terminal 33. In addition, the secondary windings 2a and 2b in the inverter transformer of FIG. 1 increase the number of turns than the conventional inverter transformer of FIG.

2 is a plan view showing another embodiment of the inverter transformer T according to the present invention. Four terminals 21 to 24 and 31 to 34 are attached to the bobbins 20 and 30, respectively. Two secondary windings 2a and 2b are wound around one bobbin 20. The high voltage end of the secondary winding 2a is connected to the terminal 21, and the low voltage side end is connected to the terminal 23. The end on the high voltage side of the secondary winding 2b is connected to the terminal 22, and the end on the low voltage side is connected to the terminal 24.

Two secondary windings 2c and 2d are wound around the other bobbin 30. The end on the high voltage side of the secondary winding 2c is connected to the terminal 31, and the end on the low voltage side is connected to the terminal 33. The end on the high voltage side of the secondary winding 2d is connected to the terminal 32, and the end on the low voltage side is connected to the terminal 34. As shown in FIG. Four secondary windings 2a, 2b, 2c, and 2d have the same inductance and are electromagnetically coupled to the primary winding 1 with the same coupling rate.

3 is a connection diagram of the inverter transformer T shown in FIG. 2. When the terminal 23 and the terminal 24, the terminal 33, and the terminal 34 are commonly connected to an external circuit, respectively, the terminals 23 and 24 are the secondary winding 2a + the secondary winding 2b. It becomes an intermediate | middle tap of and the terminals 33 and 34 become an intermediate | middle tap of the secondary winding 2c + the secondary winding 2d. Therefore, when connected externally in this way, this inverter transformer becomes circuit equivalent to the inverter transformer of FIG.

4 is a connection diagram showing an embodiment of a discharge lamp lighting apparatus using the inverter transformer as shown in FIG. The two discharge lamps 40a and 40b which consist of U-shaped pipe | tubes which have electrodes at both ends are lighted using one inverter transformer T. As shown in FIG. The intermediate tabs of the secondary windings 2a and 2b are grounded together. Both ends of the secondary winding 2a are connected to electrodes at both ends of the discharge lamp 40a, and both ends of the secondary winding 2b are connected to electrodes at both ends of the discharge lamp 40b. At both ends of the discharge lamps 40a and 40b, an alternating-phase AC voltage is applied to drive the double voltage. In addition, the circuit of the primary side of inverter transformer T is the same structure as the prior art example of FIG.

The U-shaped pipe is characteristically equivalent to the connection of two straight pipes in series. Therefore, you may comprise like FIG. 5 instead of the circuit of FIG. Four discharge lamps 40 are used for one inverter transformer T, the middle taps of the respective secondary windings 2a and 2b are grounded, and in series at both ends of the respective secondary windings 2a and 2b. The two discharge lamps 40 connected are connected. At both ends of the two discharge lamps 40 connected in series, an alternating-phase AC voltage is applied.

5 is a connection diagram showing a second embodiment of the present invention. By arranging two sets of discharge lamp lighting circuits having the circuit configuration shown in FIG. 5 in a symmetrical manner, as shown in FIG. 13, the straight discharge lamps 40 are arranged in two columns on the screen 6. Since the discharge lamp 40 arrange | positions electrodes in the form which faces outward, connection of the inverter transformer T and the discharge lamp 40 becomes easy, and it is suitable. When discharging lamps 40 are arranged at the same screen size as shown in FIG. 13, the luminance unevenness and the applied voltage in the horizontal width direction of the screen 6 are approximately half of when discharging lamps 40 are arranged as shown in FIG. 12. . In addition, although the example which arrange | positioned the discharge lamp 40 in 2 columns was shown in FIG. 13, you may make it the structure which rotates the whole 90 degrees, and arranges the discharge lamp 40 in 2 horizontal rows.

FIG. 6 is a connection diagram showing an embodiment of a discharge lamp lighting apparatus using the inverter transformer T of FIGS. 2 and 3. In this embodiment, the two U-shaped discharge lamps 40 having electrodes at both ends are turned on using one inverter transformer T. Between the terminal 21 on the high voltage side of the secondary winding 2a and the terminal 22 on the high voltage side of the secondary winding 2b, the terminal 31 on the high voltage side of the secondary winding 2c and the secondary winding ( A discharge lamp 40 is connected between the terminals 32 on the high voltage side of 2d), respectively.

The terminal 24 on the low voltage side of the secondary winding 2b and the terminal 34 on the low voltage side of the secondary winding 2d are grounded as it is, and the terminals 23 and 2 on the low voltage side of the secondary winding 2a are grounded. The terminal 33 on the low voltage side of the secondary winding 2c is grounded through a resistor R1 and a resistor R2 for detecting a discharge lamp current, respectively. The connection point between the secondary winding 2a and the resistor R1 and the connection point between the secondary winding 2c and the resistor R2 are all connected to a discharge lamp current detection circuit (not shown). By detecting the discharge lamp current, a protection circuit or the like provided when an abnormality occurs in the discharge lamp 40 can be configured. Both ends of the discharge lamp 40 are applied with an alternating-phase AC voltage and driven at a double voltage. The circuit on the primary side of the inverter transformer T has the same configuration as the conventional example of FIG. 9.

FIG. 7 is a connection diagram of a discharge lamp lighting apparatus constructed using the inverter transformer T of FIG. 2. This apparatus uses four straight discharge lamps 40 of straight tube type for one inverter transformer T. Between the terminal 21 on the high voltage side of the secondary winding 2a and the terminal 22 on the high voltage side of the secondary winding 2b, the terminal 31 on the high voltage side of the secondary winding 2c and the secondary winding ( Two discharge lamps 40 connected in series are respectively connected between the terminals 32 on the high voltage side of 2d). At both ends of the two discharge lamps 40 connected in series, an alternating-phase AC voltage is applied.

6 shows an example in which the terminals 24 and 34 on the low voltage side of the secondary windings 2b and 2d are grounded as they are, but as shown in FIG. 7, these terminals 24 and 34 are also used for detecting a discharge lamp current. May be grounded through the resistors R3 and R4. In this manner, when the discharge lamp currents on both sides are detected, there is an advantage that the current non-uniformity on both electrode sides of the discharge lamp due to the dislocation of the discharge lamp or the inclination of the discharge lamp in the backlight module can be detected.

According to the present invention, by using one inverter transformer per two or four discharge lamps, a discharge lamp lighting device of high voltage driving can be realized, and the number of use of transformers can be greatly reduced. When the discharge lamps are arranged in two rows, the voltage applied to each electrode is reduced by half compared to the one-row arrangement, so that there is less possibility of the rare short, and the discharge lamps are shortened and the strength is improved. Since the phase synchronization and the connection cable between the two rows of lighting devices are unnecessary, the assembly is easy and the extra space can be omitted. In addition, the wiring distance can be shortened, so that non-uniformity of phase characteristics does not occur, and a discharge lamp lighting device with less luminance unevenness can be obtained.

Claims (6)

In an inverter transformer having one primary winding and two secondary windings of the same number of turns that are electromagnetically coupled to the primary winding with the same coupling rate, An inverter transformer, wherein an intermediate tap is derived from each of the secondary windings. The first and second bobbins, With one primary winding, First and second secondary windings wound around the first bobbin, Third and fourth secondary windings wound on the second bobbin, Each of the first to fourth secondary windings has the same inductance and is electromagnetically coupled to the primary windings with the same coupling. The inverter transformer according to claim 1, Four discharge lamps are provided for one inverter transformer, The middle tap of each of the secondary windings is grounded, and two discharge lamps connected in series are connected to both ends of each of the secondary windings, and an AC voltage in reverse phase is applied to both ends of the two discharge lamps connected in series. Discharge lamp lighting device The inverter transformer according to claim 1, Two U-type discharge lamps are provided for one inverter transformer, A grounding lamp lighting device comprising: grounding an intermediate tap of each of the secondary windings, connecting the discharge lamps to both ends of each of the secondary windings, and applying an alternating-phase AC voltage to both ends of each of the discharge lamps. The inverter transformer according to claim 2, For one inverter transformer, two U-shaped discharge lamps are provided, One of the discharge lamps is connected between the terminal on the high voltage side of the first secondary winding and the terminal on the high voltage side of the second secondary winding, and the terminal on the high voltage side of the third secondary winding The other of the discharge lamps is connected between the terminals on the high voltage side of the fourth secondary winding, and an AC voltage in reverse phase is applied to both ends of each of the discharge lamps, At least one of the terminal on the low voltage side and the terminal on the low voltage side of the second secondary winding is grounded through a resistor, and the terminal on the low voltage side of the third secondary winding and the low voltage of the fourth secondary winding A discharge lamp lighting device characterized in that at least one of the terminals on the side is grounded through a resistor. The inverter transformer according to claim 2, For one inverter transformer, four discharge lamps are provided, Two discharge lamps connected in series between the terminal on the high voltage side of the first secondary winding and the terminal on the high voltage side of the second secondary winding are connected, and the terminal on the high voltage side of the third secondary winding is connected. And two discharge lamps connected in series between the terminals on the high voltage side of the fourth secondary winding, and applying an AC voltage in reverse phase to both ends of the two discharge lamps connected in series, At least one of the terminal on the low voltage side of the secondary winding and the terminal on the low voltage side of the second secondary winding are grounded through a resistor, and the terminal on the low voltage side of the third secondary winding and the fourth secondary A discharge lamp lighting device characterized in that at least one of the terminals on the low voltage side of the winding is grounded through a resistor.