JP2009176989A - Transformer unit for resonance type switching power supply circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem in a resonance type transformer wherein, the volume of a transformer unit is increased because a winding occupation rate is degraded when a litz wire is used for suppressing eddy current. <P>SOLUTION: This transformer unit for a resonance type switching power supply circuit is provided with: a transformer part 14 having a closed magnetic circuit core, and a primary winding 16 and a secondary winding 17 laminated and wound in a laminated form; and a choke coil part 15 serially connected to the primary winding 16, wherein a coupling coefficient between the primary winding 16 and secondary winding 17 is set not smaller than 0.995. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transformer unit for a resonant switching power supply circuit used in various electronic devices.

  A conventional resonant switching power supply circuit transformer unit will be described below with reference to the drawings.

  FIG. 8 is an exploded perspective view of a conventional transformer unit for a resonance type switching power supply circuit. A through hole 4 is provided in a bobbin 3 around which a primary winding 1 and a secondary winding 2 are wound, and an E-shaped magnetic core 5 is provided. By inserting the middle leg 6 into the through-hole 4 of the bobbin 3, a transformer unit having a closed magnetic path is configured.

For example, Patent Document 1 is known as prior art document information relating to the invention of this application.
JP 2001-230133 A

  In the conventional transformer unit, a leakage inductance Ll corresponding to about 10 to 20% of the inductance value L is used as a parameter for determining the operating frequency of the switching power supply in the resonant switching power supply circuit shown in FIG. In order to obtain the leakage inductance Ll, the coupling between the primary winding 1 and the secondary winding 2 of the transformer unit 8 of the transformer unit 7 is a loose coupling of about 0.80 to 0.95 as a coupling coefficient value. It was. Here, when the coupling between the primary winding 1 and the secondary winding 2 is loosely coupled, the partition 9 separating the primary winding 1 and the secondary winding 2 is provided on the bobbin 3 shown in FIG. The distance between the primary winding 1 and the secondary winding 2 was obtained. In the case of this form, the magnetic flux generation state by the primary winding 1 when an electric signal is applied to the primary winding 1 and the secondary winding 2 as an example is shown in FIG. As shown in FIG. 10, there is a magnetic flux φ <b> 1 that is the main flow passing through the magnetic core 5 including the middle leg 6 located in the core portion 10 of the primary winding 1 and the secondary winding 2. At the same time, there exists a leakage magnetic flux φ2 that flows through the conductor portion 11 in a state where the passage of the core portion 10 of the secondary winding 2 is incomplete, that is, a flow passing through a shortcut.

  Since this leakage flux φ2 crosses not the core portion 10 of the secondary winding 2 but the conductor portion 11 itself, an eddy current 12 is generated in the conductor portion 11. And since the loss by the eddy current 12 occurs, as a result, the heat due to the loss causes the temperature of the transformer unit 7 to rise. As countermeasures for this, by using a litz wire in which thin wires are twisted in the primary winding 1 and the secondary winding 2, the eddy current 12 is divided and subdivided, and the temperature rise is suppressed by reducing the eddy current. Was.

  However, when a litz wire is used, there is a problem that the volume of the transformer unit 7 increases because the winding space factor deteriorates.

  Therefore, the present invention provides a transformer unit for a resonant switching power supply circuit that can be reduced in size and thickness.

And to achieve this goal,
A transformer unit having a closed magnetic circuit core and a primary winding and a secondary winding wound in layers;
The choke coil portion connected in series with the primary winding,
The coupling coefficient between the primary winding and the secondary winding is 0.995 or more.

  According to the present invention, since the magnetic flux interlinking with the conductor part of the primary winding and the secondary winding can be greatly reduced, the temperature rise can be suppressed without using a litz wire for the winding, resulting in a small size, The present invention makes it possible to provide a transformer unit for a resonant switching power supply circuit having a reduced thickness.

  Hereinafter, a transformer unit according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a circuit diagram of a transformer unit in a resonant switching power supply circuit according to a first embodiment of the present invention. Here, the transformer unit is configured by a device in which the transformer section 14 and the choke coil section 15 are separated.

  FIG. 2 is an exploded perspective view of the above-described transformer unit 14. The transformer unit 14 of the transformer unit winds a primary winding 16 and a secondary winding 17, and includes a bobbin 19 having a through hole 18, and a through hole 18. The middle leg 21 is inserted from both sides, and each middle leg 21 is abutted to form a closed magnetic path. At this time, each of the magnetic cores 20 forms a closed magnetic path in a state of being abutted without forming a magnetic gap or a state of being abutted through a minute magnetic gap. As a matter of course, the middle leg 21 forms a state in which no magnetic gap is formed, or a state in which the middle leg 21 abuts through a minute magnetic gap.

  FIG. 3 shows the choke coil portion 15 of the transformer unit. The winding portion 24 is wound around the bobbin 23 having the through hole 22, and the magnetic leg 26 of the magnetic core 25 is inserted into the through hole 22 to form a closed magnetic circuit. Forming.

  The transformer section 14 shown in FIG. 1 is a resonant switching power supply circuit, and is not a flyback type that stores and releases energy, so that the primary winding 16 and the secondary winding 17 are in a harmonized operation. Winding direction or connection to become the winding specification.

  The transformer shown in FIG. 2 does not have a magnetic gap, or has a configuration in which an inductance value is adjusted by a minute magnetic gap of about 0.1 to 0.2 mm, so that it is not necessary to take great consideration of magnetic saturation. At the same time, the coupling coefficient between the primary winding 16 and the secondary winding 17 is 0.995 or more. Furthermore, as shown in FIG. 4, the primary winding 16 and the secondary winding 17 are layered and wound in the same winding groove 27 of the bobbin 19 in layers without being divided or separated. Yes. At the same time, the primary winding end portion 16a of the primary winding 16 and the secondary winding end portion 17a of the secondary winding 17 are substantially aligned with each other. That is, the length dimensions of the primary winding 16 and the secondary winding 17 in the axial direction of the core 28 are substantially equal.

  In this configuration, when the coupling coefficient between the primary winding 16 and the secondary winding 17 is 0.995 or more, an electrical signal is applied to the primary winding 16 and the secondary winding 17. The magnetic flux generated in the primary winding 16 and the secondary winding 17 is almost all the magnetic flux φ3 passing through the magnetic core 20 including the middle leg 21 located in the core portion 28 as an effective magnetic path. The magnetic flux φ3 is linked to the primary winding 16 and the secondary winding 17. That is, the leakage magnetic flux φ4 across the conductor 29 can be drastically reduced.

  As a result, the eddy current generated in the conductor 29 of the primary winding 16 and the secondary winding 17 becomes very small. Therefore, when the litz wire is not used for the conductor 29 of the primary winding 16 and the secondary winding 17 Also, a configuration that suppresses the temperature rise is possible.

  Therefore, by using a single wire, the space factor of the primary winding 16 and the secondary winding 17 in the bobbin 19 can be increased, and the transformer can be reduced in size and thickness.

  Further, as described above, the transformer section 14 generates very little leakage magnetic flux. Therefore, when the transformer section 14 is close to or attached to a metal such as a chassis or cabinet of a set (not shown) provided with the circuit of FIG. However, it is difficult to generate heat in the chassis and cabinet, and energy loss can be kept low. At the same time, it is possible to make it difficult to influence the surrounding electric circuit. Therefore, it is possible to eliminate spatial restrictions related to implementation.

  Here, the above-described coupling coefficient of 0.995 or more will be described. The coupling coefficient between the primary winding 16 and the secondary winding 17 and the primary winding 16 and the secondary winding 17 in the case where a single wire is used for the primary winding 16 and the secondary winding 17 in the transformer unit 14 of FIG. FIG. 5 shows the relationship with the temperature rise.

  Since the general transformer temperature class is class E (maximum allowable winding temperature ≦ 105 ° C.), assuming that the temperature around the transformer is 50 ° C., the allowable value for the temperature rise of the transformer itself is 55K. It is necessary to do the following. Therefore, when this value of 55K is read from FIG. 5, the coupling coefficient is an area corresponding to 0.995 or more.

  That is, by setting the coupling coefficient to a very high value, the temperature rise can be further suppressed, so that the diameter of the conductor to be used can be reduced, and the transformer can be made smaller and thinner.

  Further, as shown in FIG. 4, when the primary winding 16 and the secondary winding 17 are brought into close contact with each other and wound in an overlapping manner, the primary winding 16 and the secondary winding 17 are insulated from the proximity state. As a means for enhancing the property, it is preferable to use a three-layer insulated wire for the single conductor 29. Thereby, since insulation can be maintained even when the degree of adhesion is further strengthened, the transformer section 14 can be further reduced in size and thickness.

(Embodiment 2)
In the second embodiment, the coupling coefficient is further increased to reduce the leakage magnetic flux. As shown in FIGS. 6 and 7, the primary winding 16 and the secondary winding 17 of the transformer section 14 are arranged as a bifilar winding so that the primary winding 16 and the secondary winding 17 are disposed adjacent to each other. It is possible to increase the facing area between the line 16 and the secondary winding 17. And the primary side lamination | stacking edge part 16b of the primary winding 16 and the secondary side lamination | stacking edge part 17b of the secondary winding 17 are made into the position made to correspond substantially. That is, the length dimensions of the primary winding 16 and the secondary winding 17 in the axial direction of the core 28 are substantially equal. Thereby, the coupling coefficient between the primary winding 16 and the secondary winding 17 can be remarkably increased, and the temperature rise can be significantly reduced.

  Further, it is possible to reduce the thickness by incorporating the middle leg 21 in the vertical direction with respect to the mounting surface 30 with the magnetic core 20 having a flat shape. Furthermore, the heat generated from the primary winding 16 and the secondary winding 17 can be easily transmitted to the mounting surface 30 in a large area and at a short distance through the bobbin 19 and the magnetic core 20, thereby reducing leakage flux. At the same time, the heat dissipation can be improved.

  The transformer unit of the present invention has the effect of reducing leakage magnetic flux by increasing the degree of coupling between the primary side winding and the secondary side winding in the transformer section, and enabling miniaturization and thinning. Useful in electronic equipment.

1 is a circuit diagram of a resonant switching power supply according to a first embodiment of the present invention. The disassembled perspective view of the trans | transformer part in 1st embodiment of this invention. The disassembled perspective view of the choke coil part in 1st embodiment of this invention Sectional drawing of the transformer part in 1st embodiment of this invention Relationship diagram between the coupling coefficient of the transformer and the temperature rise in the first embodiment of the present invention Sectional drawing of the transformer part and mounting surface in 2nd embodiment of this invention The disassembled perspective view of the trans | transformer part in 2nd embodiment of this invention. Exploded perspective view of a conventional transformer Circuit diagram of resonant switching power supply using conventional transformer Cross section of a conventional transformer

Explanation of symbols

14 Transformer 15 Choke Coil 16 Primary Winding 17 Secondary Winding 18 Through Hole 19 Bobbin 20 Magnetic Core 21 Middle Leg

Claims (5)

A transformer unit having a closed magnetic circuit core and a primary winding and a secondary winding wound in layers;
A choke coil portion connected in series with the primary winding,
A transformer unit for a resonant switching power supply circuit in which a coupling coefficient between the primary winding and the secondary winding is 0.995 or more. The transformer unit for a resonance type switching power supply circuit according to claim 1, wherein the primary winding and the secondary winding have a summing polarity. 2. The transformer unit for a resonance type switching power supply circuit according to claim 1, wherein a magnetic gap is not formed in the closed magnetic circuit core of the transformer unit. The transformer unit for a resonance type switching power supply circuit according to claim 1, wherein at least one of the primary winding and the secondary winding uses a three-layer insulated wire. The transformer unit for a resonant switching power supply circuit according to claim 1, wherein the primary winding and the secondary winding are bifilar windings.

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