JP2000124045A - Inverter transformer and discharge lamp lighting circuit - Google Patents

Abstract

[PROBLEMS] To provide the same number of inverter transformers as discharge lamps, occupy a large mounting space, and increase the size of the discharge lamp lighting circuit. An inverter transformer is provided with secondary windings 71 and 73 having the same number of turns at symmetrical positions with respect to a primary winding 72, and a primary winding 72, a secondary winding 71, and a primary winding. 72 and the secondary winding 73 are electromagnetically coupled with substantially the same degree of coupling. The lighting circuit includes a first series circuit in which the inverter transformer 70, the secondary winding 71 and the discharge lamp 1 are connected in series, and a second circuit in which the secondary winding 73 and the discharge lamp 2 are connected in series. A series circuit is provided, and both ends of the first series circuit and the second series circuit are grounded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter for illuminating a cold cathode discharge tube or the like (hereinafter referred to as a discharge lamp) for illuminating the back of a liquid crystal display device, and more particularly to an inverter transformer capable of two-output or double-voltage output. And a discharge lamp lighting circuit using the inverter transformer.

[0002]

2. Description of the Related Art As the size of a liquid crystal display screen increases, a plurality of discharge lamps for illuminating the back surface thereof have been used. Since the inverter transformer for lighting the discharge lamp is generally of a one-output type, a plurality of inverter transformers are used in accordance with the number of discharge lamps. For example, when the screen size is 14 inches, two to four inverter transformers are used. Many inverter transformers are mounted, for example, eight for 18 inches and ten for 20 inches.

[0003]

As a result, a large space on the printed circuit board is occupied by the inverter transformer, and there is a problem that the discharge lamp lighting circuit becomes large. Also, the discharge lamp lighting circuit is configured as shown in FIG.
Lighting of two discharge lamps 1 and 2 with one inverter transformer 5 is also conventionally performed. That is, one end of the secondary winding 6 of the inverter transformer 5 is connected to the discharge lamps 1 and 2 via the ballast capacitors C1 and C2, respectively. However, in this configuration, the discharge lamp 2
Since the main current flows, the wire diameter of the secondary winding 6 becomes large and large, and one of the discharge lamps 1 and 2 does not light up, so that the ballast capacitors C1 and C2 cannot be omitted. was there. Therefore, the present invention has a structure in which a plurality of outputs can be obtained with one inverter transformer. In addition, the present invention provides a discharge lamp lighting circuit using such an inverter transformer,
An object of the present invention is to realize a discharge lamp lighting circuit capable of lighting a plurality of discharge lamps simultaneously with a simple circuit configuration.

[0004]

An inverter transformer according to the present invention has first and second secondary windings having the same number of turns arranged symmetrically with respect to the primary winding. It is characterized in that the first secondary winding, the primary winding and the second secondary winding are each electromagnetically coupled with substantially the same degree of coupling.
Further, the discharge lamp lighting circuit according to the present invention includes an inverter transformer configured as described above, a first series circuit formed by connecting the first secondary winding and the first discharge lamp in series, and a second series circuit. A second series circuit formed by connecting a secondary winding and a second discharge lamp in series is provided, and both ends of the first series circuit and the second series circuit are grounded.

[0005]

FIG. 1 is a front sectional view showing an embodiment of an inverter transformer according to the present invention, and FIG. 2 is a plan view. 10, 20, 30
Are insulating bobbins arranged in a line at equal intervals on the same plane. The bobbin 10 is formed by integrally forming an upper flange 11, a lower flange 13, and a cylindrical winding shaft 12, and a plurality of terminals are provided on one side surface of the lower flange 13.
41 and 42 are installed. Bobbin 20 is upper tsuba 21 and lower tsuba 23,
In addition, a rectangular cylindrical winding shaft 22 having rounded corners is integrally formed, and a plurality of terminals 45 are mounted on one side surface (upper side in FIG. 2) of the lower flange 23. The bobbin 30 is a bobbin having substantially the same shape as the bobbin 10, in which an upper flange 31, a lower flange 33, and a cylindrical winding shaft 32 are integrally formed, and a plurality of terminals 46 and 47 are attached to one side surface of the lower flange 33. is there.

The upper flange 11 and the lower flange 13 are partially thinned by providing cutouts 14 and 15 on the upper surface of the upper flange 11 and the lower surface of the lower flange 13 respectively. Bobbin 30
Similar notches 34 and 35 are also provided on the upper surface of 31 and the lower surface of lower flange 33, respectively. Notches 24 and 25 are provided on the upper surface of the upper flange 21 and the lower surface of the lower flange 23 of the bobbin 20, respectively, so that the upper flange 21 and the lower flange 23 are provided.
Is partially thinned. These notches 14, 15
The cores described later are fitted into the notches 34 and 35 and the notches 24 and 25. Also, one side of the lower collar 13 of the bobbin 10 and the bobbin
On one side of the lower collar 33, a slit reaching up to near the winding shaft
16 and 36 are provided respectively.

The terminals 41 and 42 attached to the lower flange 13 of the bobbin 10
Are divided into a terminal 41 for connecting a lead wire of the secondary winding 71 and a terminal 42 for external connection, as is apparent from FIG. That is, the terminal 42 and the short terminal 41 are paired one by one.
It is configured to be integrally connected inside. Bobbin 30
The same applies to the terminals 46 and 47 attached to the lower collar 33,
The terminal 46 is for connecting a lead wire of the secondary winding 73, and the terminal 47 is for external connection.

A low voltage side primary winding 72 is wound around the winding shaft 22 of the central bobbin 20, and its lead wire is connected to the terminal 45. A secondary winding 71 on the high voltage side is wound around the winding shaft 12 of the bobbin 10, and a lead wire is drawn out from the slit 16 under the lower flange 13 in order to increase the dielectric strength, and then connected to the shorter terminal 41. It is. Another high voltage side secondary winding 73 is wound around the winding shaft 32 of the bobbin 30, and a lead wire is drawn out from the slit 36 below the lower flange 33, and then connected to the shorter terminal 46. The two secondary windings 71 and 73 have the same number of turns and are located symmetrically about the primary winding 72.

Reference numerals 50 and 60 denote a pair of cores made of a magnetic material. The lower core 50 having an E-shaped cross section has a rectangular plate-like portion and column-shaped outer legs 51 and 53 integrally formed at both ends thereof, and a prism having a rounded corner formed integrally at the center. Center leg of
It consists of 52. The core 50 has its outer leg 51, central leg 52,
The outer legs 53 are inserted into the holes of the winding shafts 12, 22, and 32, respectively, butted against a square plate-shaped core 60 via a non-magnetic spacer 5 to prevent magnetic saturation, thereby forming a closed magnetic path. I have. As a result, the secondary winding 71 and the secondary winding 73, which are symmetrical with respect to the primary winding 72,
Electromagnetic coupling to 72 is exactly the same.

A part of the core 50 is a cutout of the bobbin 10, 20, 30.
Fitted in 15, 25, 35, the lower surface of the core 50 and the bobbin
The positions of the lower surfaces of 10, 20, and 30 are aligned. The core 60 has cutouts 14, 24, of three bobbins 10, 20, 30.
Fitted in 34. Three bobbins 10, 20, 30
Are bonded to each other by bonding the cores 50 and 60 to each other.
And the core 60 are fixed.

In order to assemble the inverter transformer, first, a secondary winding 71 is wound around a winding shaft 12 and lead wires are connected to terminals.
A bobbin 10 connected to 41, a bobbin 20 with a primary winding 72 wound around a winding shaft 22 and a lead wire connected to a terminal 45, and a secondary winding 73 wound around a winding shaft 32 and a lead wire connected to a terminal 46. Prepare the prepared bobbin 30. The bobbin 1 is inserted while the outer legs 51 and 53 are inserted into the holes of the reels 12 and 32, and the center leg 52 is inserted into the hole of the reel 22.
After placing 0, 20, and 30 on the core 50, the core 60 is
It should just adhere to. As a result, a two-output inverter transformer having external connection terminals 42 and 47 on two opposing sides and a terminal 45 on another side is completed.

In such an inverter transformer, a projection 54 projecting toward the core 60 between the primary winding 72 and the secondary winding 71 as shown in FIG. The protrusion 55 projecting toward the core 60 between the lines 73 is
The primary winding 72 and the secondary winding by forming on the upper surface of 50
A two-output inverter transformer with reduced electromagnetic coupling between 71 and 73 can be configured.

Further, the bobbin 20 in the transformer shown in FIG.
By adding a fourth bobbin to the side surface (the surface opposite to the side surface to which the terminal 45 is attached) and providing a third secondary winding,
An output type inverter transformer can also be configured.
In this case, while increasing the dimensions of the cores 50, 60, etc.,
An outer leg inserted into the fourth bobbin is added to the core 50, and the three secondary windings are electromagnetically coupled to the primary winding 72 with the same degree of coupling.

In the inverter transformer described above, a secondary winding 71, a primary winding 72, and a secondary winding 73 are wound around winding shafts 12, 22, and 32 extending in the vertical direction. It is of a type whose central axis directions are parallel to each other. However, according to the present invention, an inverter in which the primary winding 72 and the secondary windings 71 and 73 are wound on one bobbin 80 as shown in FIG. 4, and the central axes of the windings 71, 72 and 73 are on the same straight line. It is also applicable to transformers.

The bobbin 80 has three winding grooves 8 partitioned by a flange 85.
1, 82, 83 are provided. The primary winding 72 is wound around the center winding groove 82, and the secondary winding 71 and the secondary winding 73 are wound around the two outer winding grooves 81 and 83, respectively. The secondary windings 71 and 73 on the high voltage side are each divided into a plurality of parts and wound by small flanges 86 so as to prevent dielectric breakdown. A pair of cores 90 and 95 having an E-shaped cross section have respective central legs 91 and 96 inserted into holes 88 passing through the bobbin 80 to form a closed magnetic circuit.

FIG. 5 shows an example of an inverter circuit in which two discharge lamps 1 and 2 are simultaneously turned on using the two-output inverter transformer 70 of the present invention. 74 is omitted in the above description of the inverter transformer.
A feedback winding wound around the primary winding 72 with the primary winding 72 and connected to the terminal 45 with a lead wire. Q1 and Q2 are switching transistors connected in a push-pull connection, R is a bias resistor, C _C is a resonance capacitor connected in parallel with the primary winding 72, and an intermediate tap of the primary winding 72 is a choke coil L
To an input power supply (not shown).

The other end of the secondary winding 71 whose one end is grounded is connected in series to the discharge lamp 1 via a ballast capacitor C1, and the other end of the discharge lamp 1 is grounded. The other end of the secondary winding 73 whose one end is grounded is connected in series to the discharge lamp 2 via a ballast capacitor C2, and the other end of the discharge lamp 2 is grounded. It should be noted that a configuration in which the ballast capacitors C1 and C2 are omitted by using an inverter transformer as shown in FIG. 3 in which the electromagnetic coupling between the primary winding 72 and the secondary windings 71 and 73 is weakened can be used.

In the inverter circuit shown in FIG. 5, an inverter transformer is used as two outputs to turn on two discharge lamps. However, as shown in FIG. 6, this inverter transformer is used as a double voltage one output type. Can also. That is, the secondary winding 71 and the secondary winding 73 of the inverter transformer 70
Are grounded, and the non-grounded ends of the secondary winding 71 and the secondary winding 73 are connected to both ends of the discharge lamp 3 via ballast capacitors C1 and C2, respectively. This is for lighting one discharge lamp 3 at twice the voltage. The primary side of the inverter transformer 70 has the same configuration as the circuit of FIG. Also in the case of this one-output type, the inverter transformer 70 includes a primary winding 72 and a secondary winding 71 as shown in FIG.
By using a configuration in which the electromagnetic coupling between the 73 is weakened, the ballast capacitors C1 and C2 can be omitted.

[0019]

According to the inverter transformer and the discharge lamp lighting circuit of the present invention, two discharge lamps can be simultaneously lit by one inverter transformer, so that the mounting area and the mounting area are smaller than when two inverter transformers are used. Cost can be reduced.
In addition, since the driving frequencies of the respective discharge lamps are the same, there is no occurrence of beat noise or flicker. Also,
The ballast capacitor can be omitted, and it can be used as a double voltage output type. Further, the inverter transformer of the present invention can be configured to be thin, and secondary windings can be arranged at both ends. Therefore, there is an advantage that layout can be easily performed when used in a large-sized liquid crystal monitor in which discharge lamps are mounted one above and below a liquid crystal panel. .

[Brief description of the drawings]

FIG. 1 is a front sectional view showing a first embodiment of an inverter transformer according to the present invention.

FIG. 2 is a plan view of the inverter transformer.

FIG. 3 is a front sectional view showing a second embodiment of the inverter transformer of the present invention.

FIG. 4 is a front sectional view showing a third embodiment of the inverter transformer of the present invention.

FIG. 5 is a circuit diagram showing a first embodiment of a discharge lamp lighting circuit according to the present invention.

FIG. 6 is a circuit diagram showing a discharge lamp lighting circuit according to a second embodiment of the present invention.

FIG. 7 is a circuit diagram showing a conventional example of a discharge lamp lighting circuit.

[Explanation of symbols]

 10, 20, 30 Bobbin 50, 60 Core 71, 73 Secondary winding 72 Primary winding

Claims (8)

[Claims] 1. A primary winding, a first secondary winding, and a primary winding, wherein first and second secondary windings having the same number of turns are respectively arranged at symmetrical positions around the primary winding. And a second secondary winding electromagnetically coupled with substantially the same degree of coupling. 2. The method according to claim 1, wherein the first, second, and third elements are arranged on substantially the same plane.
A third bobbin, a primary winding wound around a central bobbin winding shaft, a first secondary winding wound around a first bobbin winding shaft, and a third bobbin winding shaft 2. The inverter transformer according to claim 1, wherein a second secondary winding is wound around the second secondary winding. 3. A pair of cores which abut each other to form a closed magnetic circuit, wherein a central leg formed substantially at the center of at least one of the cores is inserted into a hole of a winding shaft of a second bobbin, and at least one of the cores is provided. 3. The inverter transformer according to claim 2, wherein outer legs formed at both ends of the first and second bobbins are inserted into holes of a bobbin of the first bobbin and holes of a bobbin of the third bobbin, respectively, and the pair of cores sandwich the bobbin. . 4. A bobbin having three winding grooves separated by a flange, a primary winding wound around a central winding groove, and a first secondary winding and a second winding wound around two outer winding grooves, respectively. 2. The inverter transformer according to claim 1, wherein the secondary winding is wound. 5. The inverter transformer according to claim 1, wherein
A first series circuit formed by connecting a secondary winding of the first discharge lamp in series with a second series circuit formed by connecting a second secondary winding and the second discharge lamp in series. A discharge lamp lighting circuit, wherein both ends of a first series circuit and a second series circuit are grounded. 6. The first secondary winding and the first discharge lamp are connected in series via a first ballast capacitor, and the second secondary winding and the second discharge lamp are connected to a second ballast capacitor. 6. The discharge lamp lighting circuit according to claim 5, wherein the discharge lamp lighting circuit is connected in series via a switch. 7. An inverter transformer according to claim 1, further comprising one discharge lamp, wherein one ends of the first and second secondary windings are respectively grounded, and the first and second secondary windings are connected to each other. A discharge lamp lighting circuit, wherein the other end is connected to both ends of the discharge lamp. 8. The first secondary winding and the discharge lamp are connected via a first ballast capacitor, and the second secondary winding and the discharge lamp are connected via a second ballast capacitor. A discharge lamp lighting circuit according to claim 7.