JP2005012176A - Inverter transformer and discharge lamp lighting device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inverter transformer which can take out two kinds of high voltage output from one inverter transformer, and a discharge lamp lighting device using the inverter transformer which is easily assembled, and has small luminance unevenness. <P>SOLUTION: The transformer has one primary winding 1 and two secondary windings 2a, 2b having same number of turns which electromagnetically couple to the primary winding 1 in the equal coupling degree, in which a middle tap is derived from the secondary windings 2a, 2b. And in the discharge lamp lighting device equipped with such the inverter transformer, a plurality of discharge lamps 40 having electrodes in both ends are used on each transformer. The middle tap of each secondary windings 2a, 2b is grounded, both ends of each secondary windings 2a, 2b is connected to electrodes of different discharge lamp 40, and opposite phase AC voltage is applied to both ends of each discharge lamp 40. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a discharge lamp lighting device suitable for a large-sized liquid crystal monitor in which a discharge lamp for backlight is attached to the back of a liquid crystal display panel, and a magnetic leakage type capable of taking out two sets of high voltage outputs by one unit. The present invention relates to an inverter transformer and a discharge lamp lighting device using the inverter transformer.

An example of this type of magnetic leakage type two-output inverter transformer is disclosed in Patent Document 1. As shown in FIG. 8, the inverter transformer is provided with two secondary windings 2a and 2b having the same number of turns and electromagnetically coupled to one primary winding 1 with the same degree of coupling. The lead wires at both ends of the secondary winding 2a are wound around the connecting portions 21a and 22a of the terminals 21 and 22, respectively, and the lead wires at both ends of the secondary winding 2b are connected to the connecting portions 31a and 31a of the terminals 31, 32, respectively. It is wound around 32a and soldered. If this transformer is used when there are a plurality of discharge lamps, the mounting area can be reduced as compared to using two single-output transformers.
JP 2001-126937 A

  FIG. 9 shows an example of use of such an inverter transformer T. Discharge lamps 40a and 40b are respectively connected to the other ends of the secondary windings 2a and 2b whose one ends are grounded. Q1 and Q2 are push-pull connected 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 for frequency synchronization with other drive circuits. It is a synchronous winding used for The intermediate tap of the primary winding 1 is connected to the input terminal 3 via the choke coil L. Then, a DC voltage is applied to the input terminal 3, a sine wave high-frequency voltage is output to the secondary windings 2a and 2b, and the two discharge lamps 40a and 40b are turned on with an AC voltage having the same phase. .

  With the increase in size of the liquid crystal monitor, the discharge lamp has become longer, and when the screen becomes 40 inches or larger, the discharge lamp becomes 85 cm or longer. For example, as shown in FIG. 12, about 12 to 20 discharge lamps 40 are arranged on the back side of the screen 6. In order to light such a long discharge lamp, a kick-off voltage as high as 1800 Vrms is required, and it is necessary to always apply a high voltage of 1200 Vrms or more to the electrode of the discharge lamp even after lighting. Since a high voltage is applied, not only corona discharge is likely to occur, but also electric field noise may occur in the liquid crystal panel.

  A backlight module using a long discharge lamp has a large stray capacity and a large leakage current. As a result, as indicated by a broken line A in FIG. 11, the luminance difference a between the left end and the right end of the discharge lamp becomes large, and there is a problem that a luminance difference a of 100 candela at maximum occurs. This luminance difference a appears as luminance unevenness of the liquid crystal panel.

  Therefore, as shown in FIG. 10, in order to turn on the two discharge lamps 40a and 40b, two inverter transformers T1 and T2 are used to apply reverse phase voltages to the electrodes at both ends of the discharge lamps 40a and 40b. A double voltage drive inverter circuit as described above is used. The synchronous windings 5 of the respective inverter transformers T1 and T2 are connected to each other so as to be synchronized with an inverted phase. In this case, the central part of the discharge lamps 40a and 40b is zero potential in an alternating manner. Since the voltage applied to the electrodes at both ends is halved, the influence of the electric field is reduced, and the luminance difference b depending on the position of the discharge lamp is also reduced as shown by the solid line B in FIG.

  However, in the configuration of FIG. 10, two output-type inverter transformers are required for each two discharge lamps. Further, since a cable for connecting the synchronous windings 5 located far from each other to the left and right is required, the assembly is troublesome and the cost is increased. In addition, when a large number of discharge lamps are lit, a plurality of sets of the apparatus shown in FIG. 10 are used, so that there is a disadvantage that variations in phase characteristics occur between them.

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

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

  The second inverter transformer according to the present invention includes bobbins 20 and 30, one primary winding 1, and four secondary windings 2a, 2b, and 2c that are electromagnetically coupled to the primary winding 1 with the same degree of coupling. 2d, and 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 has a configuration in which a function equivalent to that of the first inverter transformer can be obtained by connecting a part of the secondary winding with an external circuit, and a discharge lamp current detection function can be easily added.

  Furthermore, the discharge lamp lighting device according to the present invention includes a plurality of discharge lamps 40 attached to one inverter transformer and having electrodes at both ends, and the intermediate taps of the secondary windings 2a and 2b are directly grounded or resistanceally connected. , And both ends of the secondary windings 2a and 2b are connected to electrodes of different discharge lamps 40, and opposite-phase AC voltages are applied to both ends of the respective discharge lamps.

  According to the present invention, a high voltage drive discharge lamp lighting device can be realized by using one inverter transformer per two or four discharge lamps, and the number of transformers used can be greatly reduced. When the discharge lamps are arranged in two rows, the voltage applied to each electrode is halved compared to the single row arrangement, and the possibility of rare short-circuiting is reduced, and the discharge lamp is shortened and the strength is improved. Since phase synchronization and connection cables between the two rows of lighting devices are not required, assembly is easy and extra space can be saved. In addition, it is possible to shorten the wiring distance so that the phase characteristics do not vary, and a discharge lamp lighting device with little luminance unevenness can be obtained.

  FIG. 1 shows an embodiment of an inverter transformer T. In the following drawings, portions corresponding to those of the conventional example will be described with the same reference numerals. One insulating bobbin 10 and two bobbins 20 and 30 are mounted on the lower core 50 with their side surfaces facing each other. The bobbin 10 is wound with the primary winding 1 and the feedback winding as in the conventional case, and the lead wire is connected to the terminal 12 attached to the side surface. Bobbins 20 and 30 are respectively wound with secondary windings 2a and 2b having the same number of turns and electromagnetically coupled to the primary winding 1 with the same degree of coupling.

  The lower core 50 made of a magnetic material is formed with legs 51, 52, 53 protruding upward and an elongated protrusion 54 for magnetic shunting. The leg 51 is inserted into the center of the primary winding 1, and the legs 52 and 53 are inserted into the centers of the secondary windings 2a and 2b, respectively. A flat upper core (not shown) is abutted against the legs 51, 52, 53 of the lower core 50 to form a closed magnetic circuit. The primary winding 1 and the secondary windings 2a and 2b are electromagnetically coupled by the pair of upper core and lower core 50. The protrusion 54 is located between the two secondary windings 2a, 2b and the primary winding 1, and acts to weaken electromagnetic coupling between the windings.

  This inverter transformer T is different from the conventional one shown in FIG. 8 in that an intermediate tap is derived from each of the secondary windings 2a and 2b. That is, the bobbin 20 and the bobbin 30 are respectively provided with an additional terminal 23 and a terminal 33, and the intermediate tap of the secondary winding 2a is connected to the connecting portion 23a of the terminal 23, and the intermediate tap of the secondary winding 2b is provided. It is connected to the connection part 33a of the terminal 33. Further, the secondary windings 2a and 2b in the inverter transformer of FIG. 1 are assumed to have more turns than the conventional inverter transformer of FIG.

  FIG. 2 shows another embodiment of the inverter transformer T. In FIG. Four terminals 21 to 24 and 31 to 34 are attached to the bobbins 20 and 30, respectively. On one bobbin 20, two secondary windings 2a and 2b are wound. The end of the secondary winding 2 a on the high voltage side is connected to the terminal 21, and the end on the low voltage side is connected to the terminal 23. The end of the secondary winding 2b on the high voltage side is connected to the terminal 22, and the end on the low voltage side is connected to the terminal 24.

  On the other bobbin 30, two secondary windings 2c and 2d are wound. The end of the secondary winding 2 c on the high voltage side is connected to the terminal 31, and the end on the low voltage side is connected to the terminal 33. The end of the secondary winding 2d on the high voltage side is connected to the terminal 32, and the end on the low voltage side is connected to the terminal 34. The four secondary windings 2a, 2b, 2c, and 2d have the same inductance and are electromagnetically coupled to the primary winding 1 with the same degree of coupling.

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

  FIG. 4 shows an embodiment of a discharge lamp lighting device using an inverter transformer as shown in FIG. Two discharge lamps 40a and 40b made of U-shaped tubes having electrodes at both ends are lit using a single inverter transformer T. The intermediate taps of the secondary windings 2a and 2b are both grounded. 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. The opposite-phase AC voltage is applied to both ends of the discharge lamps 40a and 40b, and the discharge lamps 40a and 40b are driven with a double voltage. The primary side circuit of the inverter transformer T has the same configuration as that of the conventional example of FIG.

  The U-shaped pipe is characteristically equivalent to a series of two straight pipes connected in series. Therefore, the configuration shown in FIG. 5 may be used instead of the circuit shown in FIG. Four discharge lamps 40 are used for one inverter transformer T, the intermediate taps of the secondary windings 2a and 2b are grounded, and the two ends of the secondary windings 2a and 2b are connected in series. The two discharge lamps 40 are connected. A reverse phase AC voltage is applied to both ends of the two discharge lamps 40 connected in series.

  By arranging two sets of the circuit of FIG. 5 symmetrically, it is possible to configure a configuration in which straight discharge lamps 40 are arranged in two vertical rows with respect to the screen 6 as shown in FIG. Since the discharge lamps 40 are arranged in such a manner that the electrodes are directed outward, the connection between the inverter transformer T and the discharge lamp 40 is easy and convenient. When the discharge lamp 40 is arranged with 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 about half that when the discharge lamp 40 is arranged as shown in FIG. Although FIG. 13 shows an example in which the discharge lamps 40 are arranged in two vertical rows, the entire configuration may be rotated 90 degrees so that the discharge lamps 40 are arranged in two horizontal rows.

  FIG. 6 shows an embodiment of a discharge lamp lighting device using the inverter transformer T of FIGS. In this configuration, two U-shaped discharge lamps 40 having electrodes at both ends are lit using one inverter transformer T. Between the high voltage side terminal 21 of the secondary winding 2a and the high voltage side terminal 22 of the secondary winding 2b, the high voltage side terminal 31 of the secondary winding 2c and the high voltage side of the secondary winding 2d The discharge lamps 40 are connected between the terminals 32, respectively.

  The low voltage side terminal 24 of the secondary winding 2b and the low voltage side terminal 34 of the secondary winding 2d are grounded as they are, and the low voltage side terminal 23 of the secondary winding 2a and the low voltage of the secondary winding 2c are low. The voltage-side terminal 33 is grounded via a discharge lamp current detection resistor R1 and a resistor R2, 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 both connected to a discharge lamp current detection circuit (not shown). By detecting the discharge lamp current, it is possible to configure a protection circuit or the like provided when an abnormality occurs in the discharge lamp 40. An opposite-phase AC voltage is applied to both ends of the discharge lamp 40 and is driven with a double voltage. The circuit on the primary side of the inverter transformer T has the same configuration as the conventional example of FIG.

  A discharge lamp lighting device as shown in FIG. 7 can also be configured using the inverter transformer T of FIG. Four straight tube type discharge lamps 40 are used for one inverter transformer T. Between the high voltage side terminal 21 of the secondary winding 2a and the high voltage side terminal 22 of the secondary winding 2b, the high voltage side terminal 31 of the secondary winding 2c and the high voltage of the secondary winding 2d Two discharge lamps 40 connected in series are connected to the terminal 32 on the side. A reverse phase AC voltage is applied to both ends of the two discharge lamps 40 connected in series.

  FIG. 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. As shown in FIG. 7, these terminals 24 and 34 are also used for detecting the discharge lamp current. It may be grounded through resistors R3 and R4. Thus, when it is set as the structure which detects the discharge lamp current of both sides, there exists an advantage which can detect the variation in the electric current of the both sides of the discharge lamp resulting from the mounting | wearing shift | offset | difference of a discharge lamp, inclination, etc. in a backlight module.

The top view of the principal part which shows one Example of the inverter transformer of this invention The top view of the principal part which shows the other Example of an inverter transformer Circuit diagram of the inverter transformer Circuit diagram showing a first embodiment of a discharge lamp lighting device The circuit diagram of the principal part showing the second embodiment A circuit diagram showing the third embodiment. The circuit diagram of the principal part showing the fourth embodiment Plan view of the main part showing a conventional example of an inverter transformer Circuit diagram showing a configuration example of a conventional discharge lamp lighting device The circuit diagram which shows the other structural example of the conventional discharge lamp lighting device Luminance distribution chart of discharge lamp Rear view showing the arrangement of a conventional discharge lamp The rear view which shows the example of arrangement | positioning of the discharge lamp by this invention

Explanation of symbols

1 Primary winding 2 Secondary winding T Inverter transformer
40 discharge lamp

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 degree of coupling, the intermediate tap is derived from each secondary winding. A featured inverter transformer. First and second bobbins, one primary winding,
First and second secondary windings wound around a first bobbin;
A third and fourth secondary winding wound around a second bobbin,
Each of the first to fourth secondary windings has the same inductance and is electromagnetically coupled to the primary winding with the same degree of coupling.   The inverter transformer according to claim 1 and four discharge lamps per inverter transformer are provided, and the intermediate tap of each secondary winding is grounded, and two discharge lamps connected in series are connected to each secondary transformer. A discharge lamp lighting device characterized in that an AC voltage having opposite phases is applied to both ends of two discharge lamps connected in series, connected to both ends of a winding.   The inverter transformer of claim 1 and two U-shaped discharge lamps per one inverter transformer, and grounding the intermediate tap of each secondary winding, respectively, at each end of each secondary winding A discharge lamp lighting device, characterized in that a discharge lamp is connected and an AC voltage having opposite phases is applied to both ends of each discharge lamp. 3. An inverter transformer according to claim 2 and two U-shaped discharge lamps per one inverter transformer, a high-voltage side terminal of the first secondary winding, and a second secondary winding The first discharge lamp is connected between the high-voltage side terminal of the third secondary winding and the high-voltage side terminal of the fourth secondary winding. The second discharge lamps are connected to each other, an alternating voltage of opposite phase is applied to both ends of each discharge lamp, and the low voltage side terminal of the first secondary winding and the low voltage of the second secondary winding are applied. At least one of the voltage side terminals is grounded via a resistor, and the low voltage side terminal of the third secondary winding and the low voltage side terminal of the fourth secondary winding are connected. A discharge lamp lighting device characterized in that it is grounded. 4. One inverter transformer according to claim 2, comprising four discharge lamps, between the high voltage side terminal of the first secondary winding and the high voltage side terminal of the second secondary winding. Two discharge lamps connected in series with each other, and two connected in series between the high voltage side terminal of the third secondary winding and the high voltage side terminal of the fourth secondary winding The discharge lamps of the first secondary winding and the second secondary winding of the first secondary winding are applied to both ends of the two discharge lamps connected in series. At least one of the terminals on the low voltage side is grounded through a resistor, and the terminal on the low voltage side of the third secondary winding and the terminal on the low voltage side of the fourth secondary winding are at least one resistor. A discharge lamp lighting device characterized in that the discharge lamp lighting device is grounded.

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