JPS6349111Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a small DC/DC converter that is integrally assembled on a magnetic circuit board.

The first relatively small capacity DC/DC converter
A ringing chain converter type DC/DC converter as shown in the figure is well known. The input that is supplied through the input filter consisting of a choke coil L1 and capacitors C1 and C2 is converted into voltage or polarity by a blocking oscillation circuit having an oscillation transformer T and an oscillation transistor Q, and is then passed through an output filter consisting of a choke coil L2 and capacitors C3 and C4. Power at a predetermined voltage is supplied to the load via the power supply.

A conventional DC/DC converter of this type has semiconductors such as coils 2 and 3, a transformer 4, a transistor 5, etc., and discrete components such as a capacitor 6 and a resistor 7 on a printed circuit board 1, as shown in FIG. After mounting, the output lead pins 8 are soldered to the printed circuit board 1, and the structure is such that the output lead pins 8 are taken out of the case 9.

This conventional technique has the drawback that an input filter coil, an oscillation transformer, and an output filter coil are each required separately, and the case must therefore be made larger.

In particular, as a recent trend, small battery-powered electronic devices (such as cameras) are becoming as small as possible.
The demand for DC/DC converters is increasing, and a problem has arisen in that conventional technology cannot meet such demands.

Another disadvantage of conventionally structured DC/DC converters is that they have poor heat dissipation effects. In other words, in the structure shown in FIG. 2, the heat generating components (transformer 4, transistor 5, etc.) are mounted on the printed circuit board, so the thermal resistance up to the outer case becomes a problem. Generally, if the inside of the case is not molded with resin, the heat resistance is determined by the thermal conductivity of the air, so the heat dissipation efficiency is very poor, and even if the inside of the case is molded with resin, the conventional structure is that from the heat generating parts to the case surface. Since the distance is long, the thermal resistance becomes large,
Heat dissipation efficiency is poor.

The present invention was devised in view of the actual state of the prior art, and its purpose is to provide a DC/DC converter that is small, easy to assemble, and has good heat dissipation efficiency.

That is, in the present invention, a conductive pattern is provided on a substrate in which notches are formed near both ends and in the center of a plate-shaped magnetic material so that they face each other from both sides. An oscillation transformer is formed on the substrate, and a DC/
This is a DC/DC converter in which other components of the DC converter are mounted, lead pins for external extraction are connected, a permanent magnet is attached to the notch of the coil to form a polarized chain, and the whole is molded with resin.

Hereinafter, one embodiment of the present invention will be described in detail based on the drawings. This embodiment is intended to realize the ringing chain converter shown in FIG. FIG. 3 is an explanatory diagram of the substrate used in the present invention. The substrate 10 has three sets of notches 1 near both ends and in the center of the plate-shaped magnetic material, facing each other from both sides.
1, 12, and 13 are formed in the width direction. For example, ferrite is suitable as the plate-shaped magnetic material, and in that case, it is easiest and preferable to press-form it into a desired shape and then sinter it. Of course, a green (unsintered) plate may be punched or cut into a desired shape and then sintered. Although it is possible to perform cutting after sintering, this is generally difficult and disadvantageous.

A predetermined circuit pattern 14 is formed on the surface of the substrate 10 (of course, both the front and back surfaces are possible). If the surface insulation resistance of the substrate 10 is sufficiently high, it may be formed directly on the substrate surface. The circuit pattern 14 can be formed using, for example, a conventionally known technique such as screen printing. If the surface insulation resistance of the substrate 10 is low, an insulating layer may be formed on the surface of the substrate 10, and the circuit pattern 14 may be formed thereon. The circuit pattern 14 includes lands and internal wiring patterns for mounting various electronic components and connecting the winding terminals of the coils L1 and L2 and the transformer T, as well as lands for mounting external lead pins. .

As shown in FIG. 4, windings are provided in the cutouts 11 and 12 at both ends of the substrate 10 to form an input side yoke coil L1 and an output side yoke coil L2.
2 is formed, and primary and secondary windings are wound together in the central cutout 13 to form the transformer T. In other words, in this invention, a magnetic material is used as the substrate, so the coil and transformer can be formed integrally with the substrate. The winding is extremely simple, as it is only necessary to wind wire around the cutouts in the substrate 10, and can be easily automated. The positional relationship between the yolk coil L1, transformer T, and yolk coil L2 is determined by the allowable limit of magnetic interference between the coils. In this invention, the cutouts 11 and 12 where the yolk coils L1 and L2 are formed are
A permanent magnet 15 such as a rare earth magnet is inserted in the choke coil, thereby polarizing the choke coil.
The whole can be made even smaller.

The magnetic field H1 generated by the input side York coil L1 is as follows.

H1=1/(π·W1) However, 1 is the current flowing through the coil L1, W1 is the width of the magnetic path cross section of the coil L1, and H1 is the strength of the magnetic field at a position W1/2 from the center of the coil L1.

Similarly, the magnetic field H2 generated by the output choke coil L2 and the magnetic field H3 generated by the main oscillation transformer T are as follows.

H2=2/(π・W2) H3=3/(π・W3) However, 2 is the current flowing in coil L2, W2 is the width of the magnetic path cross section of coil L2, and H2 is the width of W2/2 from the center of coil L2. 3 is the strength of the magnetic field at the position, 3 is the current flowing through the transistor T, W3 is the width of the cross section of the magnetic path of the transistor T, and H3 is the strength of the magnetic field at a position W3/2 from the center of the transistor T.

The degree of influence exerted by the three magnetic fields on adjacent coils is approximately determined by the ratio of the distances D1 and D2 between the coils and the widths W1, W2, and W3 of the magnetic path cross section of each coil. That is, coil L1 and transformer T
If the values of D1/W1 and D1/W3 are set to about 2 to 3 between them, the interference between the magnetic fluxes φ1 and φ3 in FIG. 4 will be reduced. Similarly, if the values of D2/W2 and D2/W3 are set to about 3 between the coil L2 and the transformer T, the interference between the magnetic fluxes φ2 and φ3 will be reduced, and normal operation as a converter will be obtained. However, in this invention,
Since the coils L1 and L2 are polarized as described above, normal operation as a converter can be obtained even if the value is made even smaller than the above value. In addition, the widths g1, g2, and g3 of the notches for the winding of each coil are 1 to 1, depending on the power capacity of the converter to be converted.
If it is about 2W or less, g1≒W2/2, g3≒W3/
The ratio may be 2, or when used as a polarized choke, this ratio may be made even smaller.

In this way, the coils L1, L2 and the transformer T are formed on the substrate 10, and as shown in FIG. are connected to the lands of the circuit pattern 14, etc. Similarly, the lead pin 17 for external extraction is also the circuit pattern 1.
Connected to 4. Thereafter, as shown in FIG. 6, a mold coating 18 made of epoxy resin or the like is formed by, for example, a dip molding method. As a result, a compact DC/DC converter integrated into a single in-line type can be obtained. It goes without saying that the structure of the package can be changed freely. Further, the circuit configuration of the converter itself is arbitrary.

In this invention, the flat magnetic substrate itself is used as the magnetic core of the transformer and chiyoke coil, and transistors, etc. are also directly attached to this substrate at the same time, so even though the total heat output is the same, the entire substrate generates heat. The amount of heat generated per unit area is small. Furthermore, since it is a flat type, the distance from heat generating components such as transistors to the outside air (converter surface) can be made very short, and the thermal resistance therebetween can be made very small. Since the thermal resistance between the heat generating components and the outside air is reduced in this way, heat dissipation efficiency is extremely high.

Since the present invention is a DC/DC converter configured as described above, the coils can be integrated with the board, and since the winding is performed using the notch, winding is simple and automation is easy. In addition, elements such as semiconductor capacitors and resistors can be mounted on the board, making it suitable for thinning.Furthermore, since both the front and back sides of the board can be used, it is possible to improve the packaging density, and since the board is made of a magnetic material, it is possible to increase the durability. Noise resistance is also good,
Since it is molded, it does not require a case, making it more compact, less expensive, suitable for automation, and has good heat dissipation efficiency, so it has great practical effects.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing an example of a DC/DC converter, Figure 2 is an explanatory diagram of the prior art, Figure 3 is an explanatory diagram showing an example of the board used in the present invention, and Figure 4 is a diagram showing winding coils. FIG. 5 is an explanatory view showing a state in which components are mounted on a board, and FIG. 6 is a partially cutaway front view showing a state in which the surface is dip molded. 10... Board, 11, 12, 13... Notch, 14... Circuit pattern, 15... Permanent magnet,
16... Chip-shaped electronic component, 17... Lead pin for external extraction.

Claims (1)

[Scope of utility model registration request] A conductive pattern is provided on a substrate in which notches are formed near both ends and in the center of a plate-shaped magnetic material so as to face each other from both sides, and wires are wound around the notches to form chiyoke coils at both ends and an oscillation transformer at the center. At the same time, other components of the DC/DC converter are mounted on the board, lead pins for external extraction are connected, a permanent magnet is attached to the notch of the coil to form a polar chain, and the whole is molded with resin. DC/DC converter.