JP2785586B2 - Mounting structure of power supply part of high frequency heating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency heating apparatus for heating foods, fluids and the like, and more particularly to a high-frequency heating apparatus using a semiconductor power converter for generating high-frequency power in a power supply device.

[0002]

2. Description of the Related Art As a power supply circuit of a high frequency heating apparatus such as a microwave oven for home use, a circuit as shown in FIG. 4 is often used. A commercial power supply 1 is a unidirectional power supply 5 formed by a diode bridge 2, an inductor 3, and a smoothing capacitor 4.
Is converted to a unidirectional voltage. The power conversion unit 10 including the resonance capacitor 6, the primary winding 7-a of the step-up transformer 7, the transistor 8 as a switching means, and the diode 9 monitors the value of the input current detection means 12 to make the input current substantially constant. The DC power of the unidirectional power supply 5 is converted to high-frequency power by the power control unit 11 that switches the transistor 8 while controlling the power supply as follows.

The high-frequency power output from the power converter 10 is a magnetron driving circuit 1 comprising a secondary winding 7-a, diodes 14, 15, a high-voltage capacitor 13, and a tertiary winding 7-c.
It is converted into a high voltage by 6 and applied to the magnetron 18.

That is, the secondary winding 7- of the step-up transformer 7
A high voltage of 1.5 to 1.7 KV is generated at b, and a half-wave voltage is rectified by the high voltage capacitor 13 and the diode 14.
After boosting to a high voltage of 3.7 to 4.0 KV, diode 15
Is applied to the magnetron 16 via the.

On the other hand, since the cathode of the magnetron is heated by the tertiary winding 7-c to excite electrons, the magnetron 15 in a state where a high voltage is applied starts oscillating and radiates electromagnetic wave energy to the inside of the heating chamber. Heat food etc.

Generally, the above-mentioned circuit components are magnetron 1
6 and the commercial power supply 1 are fixedly arranged on the printed circuit board 17 by soldering or the like, and the printed circuit board is fixed to a fixing resin mounting plate, and is attached to the body in that state. However, in view of arranging many components that generate a high voltage on the printed circuit board 17 in this manner,
There is a problem that the area of the printed circuit board becomes large in order to secure a sufficient insulation distance.

FIG. 5A shows a means for solving the problem.
As shown in the cross-sectional view of the printed circuit board of FIG. 1 and the top view of FIG. 3B, a punched slit 19 is provided on the printed circuit board between the high-voltage terminals of different polarities. 34-a and 3
4-b is a terminal of a different polarity on the printed circuit board, and a high voltage is generated between the terminals. These terminals are fixed by solder 20 on the pattern surface.

Referring to FIG. 2B, the creepage distance is a when there is no slit.
Creepage distance of the route. 18-
Looking at the straight line distances a and 18-b, the insulating performance is improved because of the presence of a slit as a space in the middle.

[0009]

However, in this configuration, when an insect such as a cockroach enters between the high voltage terminals as shown in FIG. 6 irrespective of the presence or absence of the slit, a spark is transmitted between the high voltage terminals via the cockroach. Can easily occur. In the worst case, if carbonization occurs due to sparks on the printed circuit board and the insulation performance is significantly deteriorated, continuous sparks may occur at that portion, leading to ignition or smoking, which is extremely dangerous.

In the case of a slit, a space portion other than a printed circuit board is provided between high-voltage terminals to ensure insulation performance, so that the distance between terminals for obtaining desired insulation performance is naturally determined. That was a major factor that hindered the miniaturization of printed circuit boards.

Therefore, the present invention has a simple configuration and prevents a spark between high-voltage terminals due to insects such as cockroaches, and reduces the distance between the high-voltage terminals, thereby realizing a power supply unit of a high-frequency heating apparatus capable of realizing a small printed circuit board. The purpose of the present invention is to provide a mounting structure.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a unidirectional power supply, switching means comprising at least one semiconductor element, and switching of power from the unidirectional power supply by the switching means. A power conversion unit for converting the power of the power conversion unit, a step-up transformer for boosting the output of the power conversion unit, a magnetron for irradiating electromagnetic wave energy, a magnetron driving circuit for doubling the output of the secondary side of the step-up transformer to drive the magnetron, and A printed circuit board comprising a directional power supply and switching means, a power conversion unit, a step-up transformer, and a magnetron drive circuit on the same or a plurality of boards; and a resin mounting plate for mounting the printed board, wherein the printed board is provided between terminals of the magnetron drive circuit. Slits are provided, and the resin mounting plate is a printed circuit board It is obtained by the slit and the structure projecting the resin structure.

[0013]

The mounting structure of the power supply unit of the high-frequency heating apparatus according to the present invention includes a resin mounting plate for mounting a printed circuit board in a slit provided between terminals of components of a magnetron drive circuit where a high voltage is generated. Because it is a shape that protrudes an object, it becomes an obstacle and insects such as cockroaches can not directly contact between terminals, so that sparks due to contact with insects such as cockroaches and fires derived therefrom, No problem such as smoking occurs.

Further, since the resin insulator is inserted into the slit, it is possible to obtain an insulation structure which is far stronger than the conventional insulation structure having only the slit space.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a high-frequency heating apparatus according to an embodiment of the present invention.

FIG. 4 is a circuit diagram of the power supply unit, and the description of the parts already described is omitted. The power supply unit is composed of a single printed circuit board 17, and a connection terminal 21 for connecting to the commercial power supply 1 and a connection terminal 22 for connecting to the magnetron 16 are arranged on the board, and are connected to each other by a cable. The printed circuit board 17 can be electrically connected to the chassis by tightening a screw at the ground terminal 23 portion.

FIG. 1 is a perspective view of a main part showing how a printed circuit board as a power supply unit is mounted on a resin mounting plate. When the printed circuit board 17 is mounted on the resin mounting plate 24, protruding plates 25, 26, and 27, which are resin structures, are formed at positions to be fitted with the slits 28, 29, and 30.
Here, the slit 28 and the protruding plate 25 correspond to the slit 2.
9 and the protruding plate 26, the slit 30 and the protruding plate 27
The printed circuit board 17 is properly fitted to the resin mounting plate 2
4, the projecting plate projects from the slit.

Reference numeral 23 denotes a ground terminal which is connected to a predetermined circuit on a pattern surface. Then, it is fixed to the resin mounting plate 24 by screws 31 together with the ground metal 32 connected to the printed circuit board 17 and the chassis. At this time, the ground terminal 23 and the ground metal 32 are electrically connected by the screw 31, and are grounded to the chassis as shown in the circuit diagram of FIG. Here, the jumper wire 33 connects one end of the secondary winding 7-b of the step-up transformer 7 and the high-voltage capacitor 13 in a circuit manner.

FIG. 2 is a perspective view of a main part in a state where a printed circuit board as a power supply unit is mounted on a resin mounting plate. It can be seen at a glance that the protruding plate protrudes from each slit. For example, the protruding plate 26 protrudes between the terminal of the tertiary winding 7-c, which is one of the different-polarity terminals at which high voltage is generated, and the terminal 13-a, which is one terminal of the high-voltage capacitor 13, and is an obstacle. Therefore, it can be seen that the insects such as cockroaches have a structure that cannot exist in a form of contact between the bipolar terminals.

FIG. 3 is a sectional view of the slit and the protruding plate. The insulation distance of D including the conventional space was changed to a + b by inserting the protruding plate.
+ C + d + e, which is sufficiently longer than D, can be secured. In addition, since the protruding plate 29, which is an insulating material, is present in the space, the insulation performance is significantly improved from the state of only the slits. It is also possible to reduce the space for arranging the above parts.

In order to improve the insulation performance, it is desirable to use a resin having excellent insulation performance for the protrusion plate.

[0022]

As described above, the following effects can be obtained in the mounting structure of the power supply unit of the high-frequency heating device of the first aspect.

(1) In a state where the printed board is mounted on the resin mounting board, the projected board protrudes from a slit portion provided between the high-voltage different-polarity terminals of the printed board. In this configuration, insects such as cockroaches cannot exist in a form in which both terminals are in contact with each other. Therefore, it is possible to provide a safe high-frequency heating device in which sparks caused by insects such as cockroaches between the terminals and danger modes derived from the sparks (ignition and smoke in a continuous spark due to carbonization of the substrate) do not occur at all.

(2) Since the resin, which is an insulating material, is interposed in the slit portion, the insulation performance is significantly improved as compared with the case where the slit space is left as it is, and the insulation distance is also reduced in consideration of the protruding portion in the slit. It becomes longer and the insulation performance is further improved. Therefore, the distance between the high voltage terminals can be designed to be short, and the space saving of the printed circuit board can be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of a power supply unit of a high-frequency heating device according to an embodiment of the present invention.

FIG. 2 is a perspective view of a main part showing a mounting structure of a power supply unit of the high-frequency heating device according to one embodiment of the present invention.

FIG. 3 is a sectional view of a main part of the slit and the protruding portion.

FIG. 4 is a circuit diagram of the power supply unit.

5A is a sectional view of a slit of a conventional printed circuit board, and FIG.

FIG. 6 is a sectional view of a conventional printed circuit board and a resin mounting plate.

[Explanation of symbols]

 Reference Signs List 5 unidirectional power supply unit 7 step-up transformer 8 switching means 10 power conversion unit 16 magnetron drive circuit 17 printed circuit board 18 magnetron 24 resin mounting plate 25 protruding plate 26 protruding plate 27 protruding plate 28 slit 29 slit 30 slit

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hisashi Morikawa 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (58) Field surveyed (Int.Cl. ⁶ , DB name) H05B ⁶ /64- 6/68

Claims (1)

(57) [Claims] 1. A unidirectional power supply, switching means including at least one semiconductor element, a power converter for switching power from the unidirectional power supply by the switching means to convert the power into high-frequency power, and the power converter. Step-up transformer for boosting the voltage of the unit, a magnetron for irradiating electromagnetic wave energy, a magnetron drive circuit for doubling the output of the secondary side of the step-up transformer to drive the magnetron, the unidirectional power supply, the switching means, and the A power conversion unit and a booster transformer and the magnetron drive circuit comprising a printed circuit board on the same or a plurality of substrates, and a resin mounting plate for mounting the printed circuit board, the printed circuit board between the terminals of the magnetron drive circuit A slit is provided, and the resin mounting plate is Mounting structure of the power supply portion of the high-frequency heating apparatus from the slit of the PC board and the structure projecting the resin structure.