JPH08236364A - Surface-mounting type choke coil - Google Patents

Abstract

PURPOSE: To obtain a smoothing choke coil having decreased stray capacitance and series resistance, which decreases output ripple factor to enhanced efficiency, wherein the choke coil is used in a thin-type power supply device which is driven by a high-frequency inverter and equipped with a rectifying circuit and a smoothing circuit. CONSTITUTION: A coated flat copper wire is wound edgewise on the center leg 31 of an EE-shaped thin dust core 3 for the formation of a coil 5. The lower end of the coil 5 is led out to the one side of the core 3, and the coil 5 is provided in parallel with the bottom of the core 3 up to an end 55 turning back at a turning part 53. A flat joint 54 is connected to a board through such a manner that the coating film of the coated flat copper with is stripped off. The upper end of the coil 5 is led out to the other side of the core 3 and processed the same as above. A choke coil 1 of this constitution is mechanically supported on a board from both the sides of the core 3 with the flat joints 54 and 58 and electrically connected to the board.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface mount type choke coil, and more particularly to a surface mount type choke coil to be mounted on a thin power supply device having a rectifier circuit driven by a high frequency inverter.

[0002]

2. Description of the Related Art In mobile OA equipment and communication terminals, the size of the main body is small and thin, so that the power source is naturally required to be small and thin. Conventionally, this type of thin power supply device has several 10
Driven by a 0kHz high-frequency inverter, a circuit consisting of a rectifying diode, a choke coil for smoothing, and a capacitor is often used. The circuit is mounted by mounting surface-mounted components of thin dimensions on a metal substrate. With this structure, an output of 10 W and a thickness of 3 mm to 5 mm can be obtained.

The smoothing circuit in this thin power supply device is shown in FIG.
Shown in A high frequency of several 100 kHz is rectified by the diodes 2 and 4 and smoothed by the choke coil 1 and the capacitor 10 to generate a desired DC output between the output terminals 6 and 8. In this circuit, the diodes 2 and 4 form a rectifier circuit of a so-called forward converter.

When the operating frequency of the inverter is increased in this type of thin power supply device, the constants of the smoothing choke coil 1 and the capacitor 10 are reduced in inverse proportion to the frequency, and hence the dimensions are also reduced. The equivalent circuit of the choke coil 1 is composed of a pure inductance L, a series resistance R, and a parallel capacitance C, as shown in FIG. When the inductance L becomes small, the resistance R and the capacitance C cannot be ignored, and it is necessary to keep their values small. This is because the resistance R causes power loss in proportion to the current value, and the electrostatic capacitance C acts to increase the output ripple.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a smoothing choke coil used in a thin power supply device while satisfying the height dimension restriction and at the same time keeping the series resistance component and the parallel capacitance component low. To do.

[0006]

In order to solve this problem, the present invention proposes the following means. A coil is formed by winding a coated rectangular wire around the legs of the core in an edgewise manner, and both ends of this coil are pulled out to mutually opposite sides of the core and the coating is peeled off to form a pair of flat joints. We propose a surface mount type choke coil.

Further, the pair of flat joints are arranged substantially in parallel with the bottom of the core substantially in parallel with each other. The pair of flat joints mechanically supports the substrate and at the same time electrically. It is also proposed to be connected. It is also proposed that the pair of flat joints are arranged in a direction orthogonal to the core rather than parallel to it.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 shows an embodiment of a surface mount type choke coil according to the present invention, (a) showing a top view and (b) showing a side view. Inductance 7μH, DC output current 12
In A, the inverter frequency is used at about 250kHz. The height is 5 mm.

The structure will be described in detail. So-called E
A rectangular copper wire is wound edgewise around the central leg 31 of the core 3 made of an E-shaped dust core as the coil 5. Central leg 31
Must have a circular cross section. Inner circumference of coil 5
Although 59 has a slight gap in the central leg 31 of the core 3, there is also a contacting portion. The inner peripheral portion 59 of the coil 5 has a slight gap with the central leg 31 of the core 3, but there is also a contact portion. This rectangular copper wire has a thin insulating coating formed on its surface and has a sufficient withstand voltage for the voltage used, so that the coil 5 may come into contact with the core 3. The outer peripheral portion 51 of the coil 3 is left with a relatively large window 32 of about 1 mm from the core 3. In addition, a gap 52 is provided between the windings of the coil 3 wound edgewise. This slight gap 52 serves to reduce the inter-winding capacitance.

Next, the structure of both terminals of the coil 5 will be described. The lower end of the coil 5 is pulled out to one side of the core 3 and folded back at a folding part 53, and the end 55 is arranged substantially parallel to the bottom of the core 3. This flat joint portion 54 is prepared by peeling off the coating of the coated rectangular copper wire and connecting it to a substrate (not shown). Further, the upper end of the coil 5 is pulled out to the opposite side of the core 3 and is similarly folded back at the folding portion 56, and the end portion 57 is arranged substantially parallel to the bottom portion of the core 3. The flat joint portion 58 is also processed in the same manner as the flat joint portion 54. The choke coil 1 is mechanically supported on both sides of the core 3 by the flat joints 54 and 58, and at the same time electrically connected. Then, the central leg 31 of the core 3 and the coil 5 are bonded with a resin having a good electric insulating property, for example, an epoxy resin. Also core 3
Similarly, the joint portions 33 and 34 are bonded together.

The choke coil 1 thus constructed
Insulates the coil 5 only by covering the winding material, does not use a bobbin or special insulating material, and separates the lead wires from both sides of the core 3 to suppress the stray capacitance to a lower level. be able to. Further, the flat joints 54 and 58, which are both terminals of the winding, do not generate unnecessary resistance because the winding material itself is directly used. The flat joints 54 and 58 of the coil 5 have a mechanically balanced arrangement when they are surface-mounted on the substrate at the same time, and they have the advantage of not increasing the height. In addition, the folds 53 and 56 allow the flat joint 54 and
The area of 58 can be made large along the bottom surface of the core 3. Further, the choke coil 1 is properly supported on the substrate by the elastic force of the folded portions 53 and 56.

FIG. 4 shows a second embodiment of the surface mount type choke coil according to the present invention. Elements in FIG. 4 having the same reference numerals as those in FIG. 3 correspond to the same elements. In this embodiment, both sides of the coil 5 are bent at one end along the direction in which the central leg 31 extends, and both ends 55 and 57 are arranged at right angles to the bottom of the core 3. In this embodiment, there is an advantage that the equivalent capacitance formed by the ends 55 and 57 at the bottom of the core 3 is slightly reduced.

In the above embodiment, the core shape is E
The present invention is not limited to the E shape, and the present invention can be similarly applied to core shapes such as EI, UU, and UI. Also, the space 52 between the lines of the coil 5
Regarding this, this is not essential in the present invention, and the size of the spacing portion 52 may be selected as necessary. The same applies to the window 32 of the core 3.

[0014]

Since the present invention has the characteristics as described above, the stray capacitance and series resistance of the smoothing choke coil are suppressed in the thin power supply device to further reduce the output ripple value and enhance the efficiency. . In addition, it is economical with very few constituent materials.

[Brief description of drawings]

FIG. 1 shows a smoothing circuit in a thin power supply device.

FIG. 2 shows an equivalent circuit of a choke coil.

FIG. 3 shows an embodiment of a surface-mounted choke coil according to the present invention.

FIG. 4 shows a second embodiment of the surface mount choke coil according to the present invention.

[Explanation of symbols]

1 ... Choke coil 2 ... Diode 3 ... Core
4 ... Diode 5 ... Coil 6, 8 ... Output terminal 11, 12 ... Terminal 31 ... Central leg 32 ... Window part 33, 34 ... Joint part 51 ... Outer peripheral part 52 ... Spacing part 53 ... Folding part 54 ... Flat joint part 55 ... End 56 ... Folded part 57 ... End 58 ... Flat joint 59
… Inner circumference

Claims (3)

[Claims] Claim: What is claimed is: 1. A coated rectangular wire is wound around the leg of the core in an edgewise manner to form a coil. Both ends of the coil are pulled out to opposite sides of the core, and the coated rectangular wire is peeled off to form a pair. A surface mount type choke coil, characterized in that a flat joint portion of is formed. 2. The pair of flat joints are arranged substantially parallel to the bottom of the core in substantially the same plane, and are mechanically supported on the substrate by the pair of flat joints and at the same time electrically. The surface mount choke coil according to claim 1, wherein the surface mount choke coil is connected to 3. The pair of flat joints are arranged substantially in the same plane as the bottom of the core in a substantially right-angled direction, and are mechanically supported by the pair of flat joints at the same time as being electrically supported. The surface-mounted choke coil according to claim 1, wherein the surface-mounted choke coil is electrically connected.