JP2008227421A - Transformer for inverter circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transformer capable of constructing an inexpensive inverter circuit without using a double-sided printed wiring board provided with an expensive high-voltage capacitor and a component mount prohibited area, and so on. <P>SOLUTION: The transformer comprises a first winding 11; a second winding 12 receiving the magnetic flux of the first winding; a reel 13a around which the first winding and the second winding are wound and having a magnetic core-insertion hole 13c; a bobbin 13 having a plurality of connecting terminals 14, 14 connected to each of an end 11a of the first winding and an end 12a of the second winding; and a pair of cores 15, 15 which has magnetic legs inserted in the magnetic core-insertion hole 13c of the bobbin and magnetically connects the first winding with the second winding; and is provided with an electrode generating a capacitance for adjustment between the second winding and it in the magnetic core-insertion hole of bobbin which the second winding is wound. Therefore it is possible to incorporate a capacitive component resonating with a leakage inductance in the transformer for the inverter circuit and to construct the inexpensive inverter circuit without using the double-sided printed wiring board provided with the expensive high-voltage capacitor and the component mount prohibited area, and so on. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to an inverter circuit transformer, and more specifically to an inverter circuit transformer used in a backlight inverter circuit of a display panel of an electronic device such as a liquid crystal TV or a car navigation device.

Electronic devices such as liquid crystal TVs and car navigation devices are equipped with backlight devices using cold cathode fluorescent tubes and other discharge tubes. In order to light these discharge tubes, an inverter circuit is used to obtain a high voltage power source from a low voltage DC power source.

As a conventional inverter circuit, for example, as shown in FIG. 15, a parasitic capacitance 107 generated in a secondary circuit such as a parasitic capacitance generated between the windings of the transformer 101 and a parasitic capacitance generated around the discharge tube 103 is a secondary side. A circuit that forms a leakage inductance of a circuit and a resonance circuit and supplies a high voltage to the discharge tube 103 has been proposed. Then, it has been proposed to add the auxiliary capacitor 105 in parallel with the discharge tube 103 when the parasitic capacitance 107 generated in the secondary circuit does not reach the calculated value of the series resonance.

Further, in the conventional inverter circuit, an expensive high withstand voltage capacitor is used as the ballast capacitor connected to the secondary side circuit. In order to reduce the cost of the electronic device, for example, as shown in FIG. As described above, Patent Document 2 proposes to use the interlayer capacitance of the substrate 250 as a ballast capacitor in a cold cathode tube lighting device of a liquid crystal display.
JP 7-67357 A JP 2005-63941 A

In the inverter circuit described in the latter background art, the ballast capacitor is replaced by the interlayer capacitance of the substrate. However, in order to obtain the capacitance, the opposing area of the electrodes is required, and further, different potentials are used. In order to secure a withstand voltage between the wiring pattern and the mounted component, it is necessary to provide a prohibited area for wiring pattern and component mounting, which hinders downsizing. In addition, in order to obtain an interlayer capacitance in the substrate, it is necessary to use a multilayer wiring board, a double-sided printed board or the like, and there is a problem that this method cannot be applied when a cheaper single-sided printed wiring board is used.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inverter circuit transformer that can solve the above-described problems and can constitute an inverter circuit at low cost without using an expensive high-voltage capacitor or a double-sided printed wiring board provided with a component mounting prohibited area. It is to provide.

In order to achieve the object, a transformer for an inverter circuit according to the present invention includes (1) a primary winding, a secondary winding magnetically coupled to the primary winding, and a magnetic core insertion hole. A bobbin having a winding frame around which a secondary winding is wound, a plurality of connection terminals to which an end of the primary winding and an end of the secondary winding are respectively connected, and a magnetic core insertion hole of the bobbin In a transformer for an inverter circuit having a pair of cores having a magnetic leg inserted into the core and magnetically coupling the primary winding and the secondary winding, the bobbin magnetic core around which the secondary winding is wound An electrode for generating an adjustment capacitor between the secondary winding and the secondary winding is disposed in the insertion hole. (... hereinafter referred to as first problem solving means)

Also, one of the main forms of the inverter circuit transformer is (2) characterized in that the electrode is a metal plate. (... hereinafter referred to as second problem solving means)

In another form of the inverter circuit transformer, (3) the metal plate is bent along a gap between the magnetic leg and the winding frame. (... hereinafter referred to as third problem solving means)

One of the other main forms of the inverter circuit transformer of the present invention is (4) characterized in that the electrode is a conductive film formed on the surface of the magnetic leg. (... hereinafter referred to as fourth problem solving means)

In another form of the inverter circuit transformer of the present invention, (5) the connection terminal of the bobbin includes a connection piece for contacting the conductive film. (... Hereinafter referred to as fifth problem solving means.)

One of the other main forms of the inverter circuit transformer of the present invention is (6) the electrode connected to the terminal to which the end of the secondary winding is connected. (... Hereinafter referred to as sixth problem solving means)

The operation of the first problem solving means is as follows. That is, since an electrode for generating an adjusting capacitance with the secondary winding is disposed in the magnetic core insertion hole of the bobbin around which the secondary winding is wound, the leakage of the secondary circuit A capacitance component that resonates with the inductance can be incorporated in the inverter circuit transformer.

The operation of the second problem solving means is as follows. That is, since the electrode is a metal plate, it is easy to make adjustments such as providing a width dimension, a length dimension, and a notch according to the capacitance to be acquired.

The operation of the third problem solving means is as follows. That is, since the metal plate is bent along the gap between the magnetic leg and the winding frame, a large capacitance can be obtained.

The operation of the fourth problem solving means is as follows. That is, since the electrode is a conductive film formed on the surface of the magnetic leg, it can be stably produced without variation in capacitance.

The operation of the fifth problem solving means is as follows. That is, since the connection terminal of the bobbin includes a connection piece for contacting the conductive film, the assembly is easy.

The operation of the sixth problem solving means is as follows. That is, since the electrode is connected to the terminal to which the end of the secondary winding is connected, a part of the circuit wiring can be omitted.

According to the inverter circuit transformer of the present invention, an electrostatic capacitance component that resonates with the leakage inductance can be built in the inverter circuit transformer, so that an expensive high-voltage capacitor, a double-sided printed wiring board provided with a component mounting prohibited area, and the like It is possible to provide an inverter circuit transformer capable of constructing an inverter circuit at low cost without using the. The above object and other objects, structural features, and operational effects of the present invention will become apparent from the following description and the accompanying drawings.

Hereinafter, a first embodiment of an inverter circuit transformer of the present invention will be described with reference to FIGS. FIG. 1 is an external perspective view showing the overall structure of the inverter circuit transformer 10 of the first embodiment. FIG. 2 is a longitudinal sectional view taken along line AA of FIG. 1 showing the internal structure of the inverter circuit transformer 10 of this embodiment. FIG. 3 is an exploded perspective view for explaining the internal structure of the inverter circuit transformer 10 of the present embodiment. FIG. 4 is an equivalent circuit diagram of the inverter circuit transformer 10 of the present embodiment. FIG. 5 is a circuit diagram showing an example of an inverter circuit to which the inverter circuit transformer 10 of the present embodiment is applied. FIG. 6 is a circuit diagram showing another example of an inverter circuit to which the inverter circuit transformer 10 of the present embodiment is applied.

As shown in FIGS. 1 and 2, the inverter circuit transformer 10 of this embodiment includes a primary winding 11, a secondary winding 12, a bobbin 13 around which the primary winding and the secondary winding are wound, A set of cores 15 and 15 mounted on the bobbin is provided. Specifically, the inverter circuit transformer 10 of the present embodiment is magnetically coupled by the primary winding 11 and the pair of cores 15 and 15 through substantially the same magnetic path as the magnetic flux generated from the primary winding 11. A secondary winding 12, a magnetic core insertion hole 13c, a winding frame 13a around which the primary winding 11 and the secondary winding 12 are wound, an end 11a of the primary winding 11, and the secondary winding .. Are provided with a plurality of connection terminals 14, 14... To which the end portions 12 a are respectively connected, and a magnetic leg 15 a inserted into the magnetic core insertion hole 13 c of the bobbin 13. And a pair of cores 15 and 15 for magnetically coupling the secondary winding 12 to each other. An electrode 16 is provided in the magnetic core insertion hole 13c of the bobbin 13 around which the secondary winding 12 is wound.

Next, the inverter circuit transformer 10 of the present embodiment will be described more specifically with reference to FIG. The bobbin 13 has a winding frame 13a and bases 13b and 13b provided at one end and the other end of the winding frame, respectively, and a magnetic core insertion hole so as to penetrate the center of the winding frame 13a. 13c is formed. In the winding frame 13a, a region where the primary winding 11 is wound and a region where the secondary winding 12 is wound are divided by a scissors, and a region where the secondary winding 12 is wound is , And is further divided into a plurality of regions. A plurality of connection terminals 14 and 14 are planted on the bases 13b and 13b, respectively. The plurality of connection terminals 14 and 14 are configured by a terminal portion 14a on one end side and a planting portion 14b embedded in the base 13b on the other end side. In addition, one of the plurality of connection terminals 14 planted on a base 13b provided at an end portion on the region side around which the secondary winding 12 is wound is formed in a substantially U-order shape. Yes. The connection terminal 14 is a planting portion 14b in which the U-shaped bottom is embedded in the base 13b, and a terminal portion 14a on one end side and a connection piece 14c on the other end side of the base 13b. It protrudes from the end face substantially in parallel. The primary winding 11 is wound around an area for winding the primary winding 11 in the winding frame 13 a of the bobbin 13, and its end portions 11 a and 11 a are connected to one base of the bobbin 13. The insulating coating was peeled off to a plurality of connection terminals 14 that were pulled out to the distal end side of the base 13b through a drawing groove omitted in the drawing formed in the lower portion of the base 13b, It is tangled in a state and is conductively connected to the connection terminal 14 by solder or the like. The secondary winding 12 uses an insulation-coated conductive wire having a thinner wire diameter than the primary winding 11, and is used to wind the secondary winding 12 out of the winding frame 13 a of the bobbin 13. The plurality of partitioned regions are sequentially wound from one end side toward the center flange of the bobbin 13, and the end portions 12 a and 12 a are formed below the other base 13 b of the bobbin 13. It is pulled out to the front end side of the base 13b through a drawing groove not shown in the drawing, and is entangled in a state where the insulating coating is peeled off to a plurality of connection terminals 14 implanted in the base 13b, and solder or the like Thus, the connection terminal 14 is conductively connected. A nonmagnetic metal plate such as copper having a thickness of about 0.1 mm is inserted as the electrode 16 in the magnetic core insertion hole 13c in the region where the secondary winding 12 of the bobbin 13 is wound. A lead piece 16a is provided on one end side of the metal plate, and the leading end of the lead piece 16a is bent along the end surface of the base 13b and the connection of the substantially U-shaped connection terminal 14 is made. A hole 16b through which the piece 14c is inserted is formed. In addition, an insulating sheet 17 described later is inserted into the magnetic core insertion hole 13c in the region where the secondary winding 12 of the bobbin 13 is wound so as to overlap the electrode 16. Each of the pair of cores 15 and 15 is made of a magnetic material such as Mn—Zn-based ferrite and has an E shape in plan view. The core 15 has a structure in which a magnetic leg 15a arranged at the center and a pair of side magnetic legs 15b arranged on both sides thereof are connected by a yoke 15c. The cross-sectional area of the magnetic leg 15a arranged at the center is configured to be equal to the sum of the cross-sectional areas of the side magnetic legs 15b arranged on both sides. The pair of cores 15, 15 are inserted into the magnetic core insertion holes 13 c of the bobbin 13 at the ends of the magnetic legs 15 a, 15 a arranged at the center, respectively, and the magnetic legs 15 a, 15 a are connected to each other and on both sides. The arranged side magnetic legs 15b and 15b are arranged so that the end surfaces thereof are brought into contact with each other, and are fixed to the bobbin by an adhesive, an adhesive tape, a fixing fitting having spring properties, or the like omitted in the drawing.

A preferred embodiment of the primary winding 11 is as follows. That is, the primary winding 11 is wound around the winding frame 13a of the bobbin 13, and is preferably an insulation-coated conductor, such as a polyurethane resin-coated copper wire, a polyester resin-coated copper wire, or an enamel resin-coated wire. A conducting wire or the like is more preferable. Further, the metal wire of the primary winding 11 is not limited to a single wire, and may be a stranded wire. Further, the metal wire of the primary winding 11 is not limited to a circular cross-sectional shape, and a rectangular wire having a rectangular cross-sectional shape, a square wire having a square cross-sectional shape, or the like may be used. Moreover, you may use the self-bonding wire which coat | covered the outer periphery of the said insulation coating conducting wire with low melting-point resin. Ends 11a and 11a of the primary winding 11 are in a state in which the insulating coating is peeled off from a plurality of connection terminals 14 and 14 planted on a base 13b provided at one end of the bobbin 13, respectively. It is preferable that the contact is electrically connected by solder or the like.

A preferred embodiment of the secondary winding 12 is as follows. That is, the secondary winding 12 is preferably divided into a plurality of regions divided around the winding frame 13a of the bobbin 13 and wound. Further, like the primary winding, an insulation-coated conductive wire is preferable, and a polyurethane resin-coated copper wire, a polyester resin-coated copper wire, an enamel resin-coated conductive wire, and the like are more preferable. Further, the metal wire of the secondary winding 12 is not limited to a single wire, and may be a stranded wire. The metal wire of the secondary winding 12 is not limited to a circular cross-sectional shape, and a rectangular wire having a rectangular cross-sectional shape, a square wire having a square cross-sectional shape, or the like may be used. Moreover, you may use the self-bonding wire which coat | covered the outer periphery of the said insulation coating conducting wire with low melting-point resin. Since it is necessary to increase the number of turns of the secondary winding 12 in order to generate a high voltage, it is generally preferable that the wire diameter of the secondary winding 12 is smaller than the wire diameter of the primary winding 11. . Further, the end portions 12 a and 12 a of the secondary winding 12 are plurally implanted in a base 13 b provided at one end portion of the bobbin 13, similarly to the end portion 11 a of the primary winding 11. It is preferable that the connecting terminals 14 and 14 are peeled off in a state where the insulating coating is peeled off, and are electrically connected by soldering or the like.

A preferred embodiment of the bobbin 13 is as follows. That is, as the material of the bobbin 13, an insulating resin is preferable, and an insulating resin such as a phenol resin, a polyester resin, or a liquid crystal polymer that has heat resistance and can be injection-molded with the plurality of connection terminals 14 and 14 is used. More preferred. The bobbin 13 preferably includes a winding frame 13a and a base 13b provided at one end and the other end of the winding frame 13a. However, the bobbin 13 is not limited to this. For example, a plurality of discharge tubes are provided. In what has what is called a twin structure provided with the some secondary winding for making it light, a base may be further provided in the intermediate area of the said winding frame 13a, and a connection terminal may be planted in this base. In the winding frame 13a of the bobbin 13, it is preferable that a region where the primary winding 11 is wound and a region where the secondary winding 12 is wound are separated by a hook. Moreover, it is preferable that the area | region where the said secondary winding 12 is wound is further divided into plurality by the wrinkles. It is preferable that a bridging groove for sequentially winding the secondary winding 12 is provided between adjacent regions on a ridge that divides the region around which the secondary winding 12 is wound. The base 13b of the bobbin 13 is preferably provided with connection terminals 14 and 14 to which the end portion 11a of the primary winding 11 or the end portion 12a of the secondary winding 12 is fixed. As the connection terminals 14 and 14 to be planted on the base 13b, a so-called Galwin type is preferable when surface mounting is performed on a substrate on which an inverter circuit is formed and reflow soldering is performed. When the connection terminal is inserted into the through hole and is flow soldered, a pin type that penetrates the base 13b vertically is preferable. It is preferable that the magnetic core insertion hole 13c of the bobbin 13 is formed so as to penetrate the center of the winding frame 12a. The magnetic core insertion hole 13c of the winding frame 13a in the region where the secondary winding 12 is wound is inserted with the electrode 16 and the insulating sheet 17 together with the magnetic core 15a disposed in the center of the core 15. Therefore, it is preferable that the outer diameter of the magnetic core 15a disposed in the center of the core 15 is slightly larger.

Next, a preferred embodiment of the connection terminal 14 is as follows. That is, it is preferable that the connection terminal 14 includes a planting portion 14b embedded in the base 13b and a terminal portion 14a protruding from the base 13b.

Next, a preferred embodiment of the core 15 is as follows. That is, as the material of the core 15, various magnetic materials such as Mn—Zn ferrite, Ni—Zn ferrite, dust core, laminated metal plate and the like can be used. The magnetic material preferably has a high insulating property such as Ni—Zn ferrite, but is not limited thereto, and may be a low insulating material such as Mn—Zn ferrite. . Further, the outer surface of the core of the low-insulating magnetic material may be used by being coated with an insulating resin such as a fluororesin, or insulated between a magnetic leg 15a of the core 15 and an electrode 16 described later. A sheet 17 may be inserted. As the structure of the core 15, it is preferable to have a magnetic leg 15a to be inserted into the magnetic core insertion hole 13c of the bobbin 13 and form a magnetic path as a set for the convenience of assembly. The external shape of the pair of cores 15 and 15 is preferably an EE type, an EI type, or a low I type in order to obtain a thin inverter circuit transformer. However, the present invention is not limited to this. For example, in order to be accommodated along the frame portion of the liquid crystal panel, a U-U shape, a UI shape, or the like may be used.

Next, a preferred embodiment of the electrode 16 is as follows. That is, the electrode 16 is inserted into the magnetic core insertion hole 13c in the region where the secondary winding 12 of the bobbin 13 is wound together with the magnetic leg 15a disposed in the center of the core 15. is there. The electrode 16 is preferably a nonmagnetic metal plate such as a copper foil. When a metal plate is used as the electrode 16, it is preferable to have a lead piece 16a on one end side of the metal plate. The lead piece 16a is preferably connected to the connection terminal 14 planted on the base 13b of the bobbin 13. However, the present invention is not limited to this, and for example, a wiring pattern of a circuit board forming an inverter circuit A direct conductive connection may be used. Moreover, when connecting the said drawer | drawing-out piece 16a to the said connection terminal 14, it is preferable to provide the hole 16b engaged with the connection piece 14c of the said connection terminal, a notch, etc. The electrode 16 is not limited to a metal plate. For example, the electrode 16 is formed on the surface of the magnetic leg 15a inserted through the magnetic core insertion hole 13c of the bobbin 13 as a coating film or a plating film of a conductive paste. May be. When the electrode 16 is formed as a conductive film on the surface of the magnetic leg 15 a of the core 15, the core 15 made of a highly insulating magnetic material such as Ni—Zn ferrite is used as the material of the core 15. However, the present invention is not limited to this, and it is possible to use a low-insulating core whose surface is previously coated with an insulating resin such as a fluororesin. When the core 15 made of the low-insulating magnetic material is used without insulating coating on the surface of the magnetic leg 15a of the core 15, for example, a fluorine resin is interposed between the electrode 16 and the magnetic leg 15a of the core 15. It is preferable to sandwich an insulating sheet made of the like.

The inverter circuit transformer 10 of the present embodiment will be described with reference to an equivalent circuit shown in FIG. That is, one end of the electrode 16 facing the secondary winding 16 via the winding frame 13a of the bobbin 13 in parallel with the magnetic leg 15a of the core 15 connects the one end 12a of the secondary winding 12 and the connection terminal 14. Are electrically connected.

Next, an example of an inverter circuit using the inverter circuit transformer 10 of the present embodiment will be described with reference to FIG. The inverter circuit of the present embodiment includes an inverter circuit transformer TF of the present embodiment, a DC power source Vcc connected to the primary winding of the transformer TF, a switching circuit SW connected to the primary winding, and the transformer A cold cathode discharge tube CCFL connected to one end of the secondary winding of the TF, a current detection circuit connected to the other end of the secondary winding, the other end of the secondary winding and the ground And a drive control circuit that controls the switching circuit SW based on the current value obtained by the current detection circuit.

The inverter circuit transformer 10 according to the present embodiment generates an adjustment capacity between the secondary winding 12 and the magnetic core insertion hole 13c of the bobbin 13 around which the secondary winding 12 is wound. Since the electrode 16 is provided, a capacitance component that resonates with the leakage inductance of the secondary circuit is built in the inverter circuit transformer 10. For this reason, it is possible to omit the use of an expensive external high-voltage capacitor or provision of a prohibited area such as a wiring pattern or component mounting on a multilayer wiring board or a double-sided printed wiring board for acquiring an interlayer capacitance. .

Further, in the inverter circuit transformer 10 of the present embodiment, the electrode 16 is a metal plate, and therefore, the dimensions can be easily adjusted according to the adjustment capacity to be acquired.

Further, in the inverter circuit transformer 10 of the present embodiment, since the electrode 16 is connected to the connection terminal 14a to which the end of the secondary winding 12 is connected, the inverter circuit adjustment capacitor is connected. A part of the circuit wiring can be omitted.

The operation of the inverter circuit is as follows. That is, a DC voltage input from a DC power source Vcc is converted into a high frequency voltage by the switching circuit SW and boosted by the inverter circuit transformer TF. At this time, the leakage inductance on the secondary side of the inverter circuit transformer TF, the parasitic capacitance generated around the adjustment capacitor and the discharge tube built in the inverter circuit transformer TF, and the secondary winding of the inverter transformer TF A parasitic capacitance between lines and a resonance circuit are formed, and a high voltage is supplied to the cold cathode discharge tube CCFL. Obtained by the current detection circuit connected to the other end side of the secondary winding, the resistor R connected between the other end side of the secondary winding and the ground, and the current detection circuit The drive control circuit that controls the switching circuit SW based on the current value drives the switching circuit SW so that the current value flowing through the cold cathode discharge tube CCFL becomes a desired value.

Next, another example of the inverter circuit using the inverter circuit transformer of the present embodiment will be described with reference to FIG. The inverter circuit of the present embodiment includes an inverter circuit transformer TF of the present embodiment, a DC power source Vcc connected to the primary winding of the transformer TF, a switching circuit SW connected to the primary winding, and the transformer A cold cathode discharge tube CCFL connected to one end of the secondary winding of the TF, a voltage detection circuit connected to the other end of the secondary winding, the other end of the secondary winding and the ground And a drive control circuit for controlling the switching circuit based on the voltage value obtained by the voltage detection circuit. According to this, an inverter circuit can be configured using an inexpensive low-voltage capacitor C2 having a capacitance of several thousand pF.

The operation of the inverter circuit is as follows. A DC voltage input from the DC power source Vcc is converted into a high frequency voltage by the switching circuit SW and boosted by the inverter circuit transformer TF. At this time, the leakage inductance on the secondary side of the inverter circuit transformer TF, the parasitic capacitance generated around the adjustment capacitor and the discharge tube built in the inverter circuit transformer TF, and the secondary of the inverter transformer A parasitic capacitance between the windings and a resonance circuit are formed, and a high voltage is supplied to the discharge tube. The parasitic capacitance generated around the adjustment capacitor C1 and the discharge tube and the parasitic capacitance between the secondary windings of the inverter transformer are several tens of pF, so the other end side of the secondary winding and the ground Is very small compared to the low-voltage capacitor C2 having a capacitance of several thousand pF connected between the two. Therefore, the influence of the low-voltage capacitor C2 is negligible on the resonance circuit. An inverter by controlling the switching circuit SW by a drive control circuit based on the voltage value detected by the voltage detection circuit with respect to the output voltage of the secondary winding divided by the divided voltage of the adjustment capacitor C1 and the low-voltage capacitor C2. The switching circuit SW is driven so that the output voltage of the secondary winding of the circuit transformer TF becomes a desired value.

Next, a second embodiment of the inverter circuit transformer of the present invention will be described with reference to FIG. FIG. 7 is an exploded perspective view for explaining the internal structure of the inverter circuit transformer 20 of the present embodiment.

As shown in FIG. 7, the inverter circuit transformer 20 of the present embodiment includes a primary winding 21, a secondary winding 22, a bobbin 23 around which the primary winding 21 and the secondary winding 22 are wound, and the bobbin. 23 and a set of cores 25 and 25 attached to 23. Specifically, the inverter circuit transformer 20 of the present embodiment includes a primary winding 21, a secondary winding 22 that receives the magnetic flux of the primary winding 21, and a magnetic core insertion hole 23c. And a plurality of connection terminals 24, 24,... To which a winding frame 23a around which the secondary winding 22 is wound and an end portion 21a of the primary winding 21 and an end portion 22a of the secondary winding 22 are respectively connected. A pair of cores 25 and 25, each having a magnetic leg 25a inserted into the magnetic core insertion hole 23c of the bobbin 23 and magnetically coupling the primary winding 21 and the secondary winding 22. It is what you have. An electrode 26 is provided in the magnetic core insertion hole 23c of the bobbin 23 around which the secondary winding 22 is wound. The first difference of the inverter circuit transformer 20 of the present embodiment from the inverter circuit transformer 10 of the first embodiment is that the surface of the core 25 is covered with a fluororesin, not shown, as the core 25. A ferrite core is used, thereby omitting the insulating sheet 17 inserted between the electrodes 16 in the above embodiment. The second difference of the inverter circuit transformer 20 of the present embodiment from the inverter circuit transformer 10 of the first embodiment is that the metal plate as the electrode 26 includes the outer peripheral surface of the magnetic leg 25a and the winding frame. It is bent along the gap with 23a and has a substantially U-shaped cross section. Thereby, a larger capacitance can be obtained as compared with the previous embodiment. Since other configurations and operational effects are the same as those of the inverter circuit transformer 10 of the first embodiment, the description thereof is omitted.

Next, a third embodiment of the inverter circuit transformer of the present invention will be described with reference to FIGS. FIG. 8 is an external perspective view for explaining the overall structure of the inverter circuit transformer 30 of the third embodiment. FIG. 9 is a longitudinal sectional view taken along line BB in FIG. 8 showing the internal structure of the inverter circuit transformer 30 of the present embodiment. FIG. 10 is an exploded perspective view for explaining the internal structure of the inverter circuit transformer 30 of the present embodiment. FIG. 11 is an equivalent circuit diagram of the inverter circuit transformer 30 of the present embodiment. FIG. 12 is a circuit diagram showing an example of an inverter circuit to which the inverter circuit transformer 30 of the present embodiment is applied.

The inverter circuit transformer 30 of the present embodiment has a so-called twin structure including a plurality of secondary windings 32 and 32 for lighting a plurality of discharge tubes. As shown in FIGS. 8 and 9, the inverter circuit transformer 30 of the present embodiment includes a primary winding 31, a pair of secondary windings 32, 32 respectively disposed between the primary winding 31 and the primary winding 31. A bobbin 33 around which the primary winding 31 and the secondary windings 32 and 32 are wound and a pair of cores 35 and 35 attached to the bobbin are provided. Specifically, the inverter circuit transformer 30 of the present embodiment includes a primary winding 31, a pair of secondary windings 32 and 32 that receive magnetic flux of the primary winding 31, and a magnetic core insertion hole 33 c. A winding frame 33a around which the primary winding 31 and the pair of secondary windings 32 and 32 are wound, and an end portion 31a of the primary winding 31 and end portions 32a and 32a of the secondary windings 32 and 32, respectively. A bobbin 33 having a plurality of connection terminals 34, 34,... Connected, and a magnetic leg 35a inserted into a magnetic core insertion hole 33c of the bobbin 33, the primary winding 31 and the secondary windings 32, 32 And a pair of cores 35 and 35 for magnetically coupling the two. Electrodes 36 and 36 for generating adjustment capacitances between the secondary windings 32 and 32 are respectively arranged in the magnetic core insertion holes 33c of the bobbin 33 around which the secondary windings 32 and 32 are wound. It is installed.

Next, the inverter circuit transformer 30 of the present embodiment will be described more specifically with reference to FIG. The bobbin 33 includes a winding frame 33a, bases 33b and 33b provided at one and other ends of the winding frame, and two bases 33b and 33b provided therebetween, A magnetic core insertion hole 33c is formed so as to penetrate the center of the winding frame 33a. In the winding frame 33a, a region where the primary winding 31 is wound and a region where the secondary windings 32 and 32 are wound with the region interposed therebetween are divided by scissors, and the secondary winding The region around which 32 and 32 are wound is further divided into a plurality of regions by a hook. A plurality of connection terminals 34, 34 are planted in the bases 33 b, 33 b at one and other ends of the bobbin 33 so as to penetrate the base 33 b vertically. Further, in the two bases 33b and 33b provided in the middle, the connection terminals 34 and 34 are respectively planted so as to vertically penetrate the base 33b in the same manner as described above. The connection terminals 34 and 34 are composed of a terminal portion 34a on the lower end side, a connection piece 34c on the upper end side, and a planting portion 34b embedded in the intermediate writing base 33b. The primary winding 31 is wound around an area for winding the primary winding 31 in the winding frame 33 a of the bobbin 33, and its end portions 31 a and 31 a are wound around the winding frame of the bobbin 33. In the middle of 33a, two bases 33b and 33b are connected to the connection terminals 34 and 34 which are planted in the state where the insulation coating is peeled off and conductively connected to the connection terminal 34 by solder or the like. Yes. The secondary winding 32 uses an insulation-coated conductive wire having a thinner wire diameter than the primary winding 31, and is used for winding the secondary winding 32 in the winding frame 33 a of the bobbin 33. The plurality of divided regions are sequentially wound from one end side toward the middle flange of the bobbin 33, and the end portions 32a and 32a are formed below the base 33b at the end portion of the bobbin 33. The lead wire 33 is pulled out to the distal end side of the base 33b through a drawing groove (not shown), and is tangled in a state where the insulating coating is peeled off to a plurality of connection terminals 34 implanted in the base 33b. For example, the connection terminal 34 is electrically conductively connected. In the magnetic core insertion hole 33c in the region where the secondary winding 32 of the bobbin 33 is wound, as in the second embodiment, the electrode 36 has a thickness of about 0.1 mm such as copper. A magnetic metal plate is bent along the gap between the outer peripheral surface of the magnetic leg 35a and the winding frame 33a, and the cross section is formed in a substantially U shape and inserted. A lead piece 36a is provided on one end side of the metal plate, the tip of the lead piece 36a is bent along the end surface of the base 33b, and the connection piece 34c of the connection terminal 34 is engaged. A cutout 36b is formed. Each of the pair of cores 35 and 35 is made of a magnetic material such as Mn—Zn-based ferrite, and the surface thereof is covered with a fluorine resin (not shown) so that the shape in plan view is an E shape. The core 35 has a structure in which a magnetic leg 35a disposed in the center and a pair of side magnetic legs 35b, 35b disposed on both sides thereof are connected by a yoke 35c. The cross-sectional area of the magnetic leg 35a disposed at the center is configured to be equal to the sum of the cross-sectional areas of the side magnetic legs 35b and 35b disposed on both sides. The pair of cores 35, 35 are inserted into the magnetic core insertion holes 33 c of the bobbin 33 at the tips of the magnetic legs 35 a, 35 a arranged at the center, respectively, The arranged side magnetic legs 35b and 35b are arranged so that the end surfaces thereof are brought into contact with each other, and are fixed to the bobbin by an adhesive, an adhesive tape, a fixing fitting having a spring property, or the like omitted in the drawing.

Next, the inverter circuit transformer 30 of the present embodiment will be described with reference to an equivalent circuit shown in FIG. That is, one end 32a of the secondary winding 32 is one end side of the electrodes 36, 36 facing the secondary windings 36, 36 in parallel with the magnetic legs 35a of the core 35 via the winding frame 33a of the bobbin 33. Are electrically connected via a connection terminal 34.

Next, an example of an inverter circuit using the inverter circuit transformer 30 of the present embodiment will be described with reference to FIG. The inverter circuit of the present embodiment includes an inverter circuit transformer TF of the present embodiment, a DC power source Vcc connected to the primary winding of the transformer TF, a switching circuit SW connected to the primary winding, and the transformer A cold cathode discharge tube CCFL1, CCFL2 connected to one end of each of the pair of secondary windings of TF, a current detection circuit connected to the other end of each of the secondary windings, Each includes resistors R1 and R2 connected between the other end side and the ground, and a drive control circuit for controlling the switching circuit SW based on a current value obtained by the current detection circuit.

The operation of the inverter circuit is as follows. A DC voltage input from a DC power supply Vcc is converted into a high frequency voltage by the switching circuit SW and boosted by the inverter circuit transformer TF. There are two secondary windings so that the secondary side of the inverter circuit transformer TF has two outputs. Each secondary winding has a leakage inductance and is incorporated in the inverter circuit transformer TF. A resonant circuit is formed with the parasitic capacitance generated around the adjustment capacitor and the discharge tube corresponding to each of them and the parasitic capacitance between the secondary windings of the inverter transformer. Supply voltage. In each secondary winding, a current detection circuit connected to the other end of the secondary winding, resistors R1 and R2 connected between the other end of the secondary winding and the ground, The switching circuit SW is driven by the drive control circuit that controls the switching circuit SW based on the current value obtained by the current detection circuit so that the current value flowing through the cold cathode discharge tubes CCFL1 and CCFL2 becomes a desired value.

Next, a fourth embodiment of the inverter circuit transformer of the present invention will be described with reference to FIGS. FIG. 13 is a longitudinal sectional view showing the internal structure of the inverter circuit transformer 40 of the fourth embodiment. FIG. 14 is an exploded perspective view for explaining the internal structure of the inverter circuit transformer 40 of the present embodiment.

As shown in FIGS. 13 and 14, the inverter circuit transformer 40 of the present embodiment includes a primary winding 41, a secondary winding 42, and a bobbin 43 around which the primary winding 41 and the secondary winding 42 are wound. And a pair of cores 45, 45 attached to the bobbin 43. Specifically, the inverter circuit transformer 40 of the present embodiment includes a primary winding 41, a secondary winding 42 that receives the magnetic flux of the primary winding 41, and a magnetic core insertion hole 43 c. A plurality of connection terminals 44, 44,... To which a winding frame 43a around which the secondary winding 42 is wound and an end 41a of the primary winding 41 and an end 42a of the secondary winding 42 are connected, respectively. A pair of cores 45 and 45, each having a magnetic leg 45a inserted into the magnetic core insertion hole 43c of the bobbin 43 and magnetically coupling the primary winding 41 and the secondary winding 42. It is what you have. An electrode 46 is provided in the magnetic core insertion hole 43c of the bobbin 43 around which the secondary winding 42 is wound so as to generate an adjustment capacitor with the secondary winding 42. The first difference of the inverter circuit transformer 40 of the present embodiment from the inverter circuit transformer 10 of the first embodiment is that the surface of the core 45 is covered with a fluororesin (not shown). A ferrite core is used, thereby omitting the insulating sheet 17 inserted between the electrodes 16 in the above embodiment. The second difference of the inverter circuit transformer 40 of the present embodiment from the inverter circuit transformer 10 of the first embodiment is that the electrode 46 serves as a side surface of the yoke 45c from the surface of the magnetic leg 45 of the core 45. A conductive film formed by printing is used. For this reason, it can be stably produced without variation in capacitance. The third difference of the inverter circuit transformer 40 of the present embodiment from the inverter circuit transformer 10 of the first embodiment is that the connection terminal 44 of the bobbin 43 is in contact with the conductive film. A piece 44c is provided. Thereby, the assembly of the inverter circuit transformer 40 is easy. Since other configurations and operational effects are the same as those of the inverter circuit transformer 10 of the first embodiment, the description thereof is omitted.

In the above embodiments, the EE type is used as a set of cores. However, the present invention is not limited to this, but the EI type, the Ro type, the UU type, the UI type, etc. However, there is no difference in the operational effects of the present invention.

The present invention is suitable as a transformer for an inverter circuit of various electronic devices having a backlight such as a liquid crystal TV.

1 is an external perspective view showing an overall structure of a first embodiment of an inverter circuit transformer of the present invention. It is a longitudinal cross-sectional view in the AA line of the said FIG. 1 which shows the internal structure of the transformer for inverter circuits of the said embodiment. It is a disassembled perspective view for demonstrating the internal structure of the transformer for inverter circuits of the said embodiment. It is an equivalent circuit diagram of the transformer for inverter circuits of the embodiment. It is a circuit diagram which shows an example of the inverter circuit to which the transformer for inverter circuits of the said embodiment is applied. It is a circuit diagram which shows the other example of the inverter circuit to which the transformer for inverter circuits of the said embodiment is applied. It is a disassembled perspective view for demonstrating the internal structure of 2nd Embodiment of the transformer for inverter circuits of this invention. It is an external appearance perspective view which shows the whole structure of 3rd Embodiment of the transformer for inverter circuits of this invention. It is a longitudinal cross-sectional view in the BB line of the said FIG. 8 which shows the internal structure of the transformer for inverter circuits of the said embodiment. It is a disassembled perspective view for demonstrating the internal structure of the transformer for inverter circuits of the said embodiment. It is an equivalent circuit diagram of the transformer for inverter circuits of the embodiment. It is a circuit diagram which shows an example of the inverter circuit to which the transformer for inverter circuits of the said embodiment is applied. It is a longitudinal cross-sectional view which shows the internal structure of 4th Embodiment of the transformer for inverter circuits of this invention. It is a disassembled perspective view for demonstrating the internal structure of the transformer for inverter circuits of the said embodiment. It is a circuit diagram which shows an example of background art. It is sectional drawing which shows the other example of background art.

Explanation of symbols

10: Transformer for inverter circuit 11: Primary winding 11a: End portion 12: Secondary winding 12a: End portion 13: Bobbin 13a: Winding frame 13b: Base 13c: Magnetic core insertion hole 14: Connection terminal 14a: Terminal portion 14b: implanted portion 14c: connection piece 15: core 15a: magnetic leg 15b: side magnetic leg 15c: yoke 16: electrode 17: insulating sheet 20: inverter circuit transformer 21: primary winding 21a: end 22: secondary Winding 22a: End 23: Bobbin 23a: Winding frame 23b: Base 23c: Magnetic core insertion hole 24: Connection terminal 24a: Terminal part 24b: Planting part 24c: Connection piece 25: Core 25a: Magnetic leg 25b: Side Magnetic leg 25c: Yoke 26: Electrode 30: Inverter circuit transformer 31: Primary winding 31a: End 32: Secondary winding 32a: End 33: Bobbin 33a: Winding frame 33b: Base 33c: Magnetic core insertion hole 34 Connection terminal 34a: Terminal part 34b: Planting part 34c: Connection piece 35: Core 35a: Magnetic leg 35b: Side magnetic leg 35c: Yoke 36: Electrode 40: Inverter circuit transformer 41: Primary winding 41a: End part 42: Secondary winding 42a: End 43: Bobbin 43a: Winding frame 43b: Base 43c: Magnetic core insertion hole 44: Connection terminal 44a: Terminal 44b: Planting part 44c: Connection piece 45: Core 45a: Magnetic leg 45b : Side magnetic leg 45c: Yoke 46: Electrode 50: Inverter circuit transformer 51: Primary winding 51a: End 52: Secondary winding 52a: End 53: Bobbin 53a: Winding frame 53b: Base 53c: Magnetic core Insertion hole 54: Connection terminal 54a: Terminal part 54b: Planting part 54c: Connection piece 55: Core 55a: Magnetic leg 56: Electrodes C1, C2: Capacitor CCFL: Cold cathode discharge tube SW: Switching circuit TF: To Nsu R, R1, R2: resistance Vcc: power source

Claims (6)

A primary winding, a secondary winding magnetically coupled to the primary winding, a winding frame provided with a magnetic core insertion hole, around which the primary winding and the secondary winding are wound, and an end of the primary winding A bobbin having a plurality of connection terminals to which the end of the secondary winding is connected, and a magnetic leg to be inserted into the magnetic core insertion hole of the bobbin, and the primary winding and the secondary winding. In a transformer for an inverter circuit having a pair of cores to be magnetically coupled, an adjustment capacitance is generated between the secondary winding in a magnetic core insertion hole of a bobbin around which the secondary winding is wound. An inverter circuit transformer comprising electrodes. The inverter circuit transformer according to claim 1, wherein the electrode is a metal plate. 3. The inverter circuit transformer according to claim 2, wherein the metal plate is bent along a gap between the magnetic leg and the winding frame. 2. The inverter circuit transformer according to claim 1, wherein the electrode is a conductive film formed on a surface of the magnetic leg. The inverter circuit transformer according to claim 4, wherein the connection terminal of the bobbin includes a connection piece for contacting the conductive film. 2. The inverter circuit transformer according to claim 1, wherein the electrode is connected to a terminal to which an end of the secondary winding is connected.

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