JPH02223182A - Electric equipment for controlling microcomputer - Google Patents

Abstract

PURPOSE:To prevent the adverse effect of static electricity on a microcomputer by discharging static electricity to one terminal of the primary coil of a control power transformer via a gap portion between a pair of discharge conductor patterns and a resistor. CONSTITUTION:When the grounding of an microwave oven main body 1 by an earth bar 7 or the like is forgotten and the static electricity charged on a user flows on the oven main body 1, the static electricity is discharged to a power conductor pattern 1 via an earth wire 21 and a discharge conductor pattern 19. Since a resistor 22 is connected between a discharge conductor pattern 20 and a power conductor pattern 11, the discharging voltage of a gap G portion between the discharge conductor patterns 19 and 20 is suppressed low, and the surge current flowing in the power conductor pattern 11 via the resistor 22 is suppressed low. The adverse effect of static electricity on a microcomputer can be prevented with a simple structure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a microcomputer-controlled electrical device that prevents the adverse effects of static electricity on a microcomputer.

(Prior Art) In an electric device such as a microwave oven controlled by a microcomputer, when a user's hand touches the oven body, static electricity charged on the user may flow into the oven body. If the microwave oven itself is grounded, such as by burying a grounding rod in the ground, static electricity will be discharged to the ground, but people often forget to ground the microwave oven, and in such cases, static electricity can May discharge into circuit. Static electricity is sometimes discharged at a high voltage of several kilovolts, and in such cases, the microcomputer in the control circuit that receives power from the power supply circuit may be adversely affected by malfunction or destruction.

For this reason, conventionally, a filter or a discharge tube is provided in the power supply circuit, or a capacitor is provided in the control circuit, to prevent the negative influence of static electricity on the microcomputer.

(Problems to be Solved by the Invention) In the conventional configuration, there is a problem in that the price increases as a filter, a discharge tube, or a capacitor is provided.

The present invention has been made in view of the above circumstances, and its purpose is to provide a microcomputer-controlled electrical device that can prevent the adverse effects of static electricity on a microcomputer with a simple configuration, and that can reduce costs. It is on offer.

[Structure of the Invention] (Means for Solving the Problems) A microcomputer-controlled electrical device of the present invention includes a microcomputer-controlled electrical device in which a control circuit for controlling a load within the device body is mounted on a printed wiring board disposed within the device body. The computer is formed to include a computer, and the printed wiring board is provided with a control power transformer for supplying DC power to the control circuit, and the printed wiring board has a predetermined gap between them, and one side is connected to the device main body. The present invention is characterized in that a pair of discharge conductor patterns are formed, and a resistor is connected between the other of the pair of discharge conductor patterns and one terminal of the primary coil in the control power transformer.

(Function) According to the microcomputer-controlled electrical equipment of the present invention, if static electricity flows through the equipment body when the equipment body is not grounded, the static electricity will flow through the gap between the pair of discharge phase conductor patterns and the resistor. It is discharged to the primary coil of the control power transformer through the power supply transformer. In this case, the discharge voltage at the gap between the pair of discharge conductor patterns is suppressed to a low level by the resistor, and the surge current flowing to the primary coil via the resistor is also suppressed to a low level. has no effect on the secondary coil side.

(Example) Hereinafter, an example in which the present invention is applied to a microwave oven will be described with reference to the drawings.

First, the overall configuration will be described according to FIG. Reference numeral 1 denotes a microwave main body, which is the main body of the device, and a heating chamber 2 is provided inside. A magnetron 3 as a load is disposed on the upper plate of the heating chamber 2, and a turntable 4 is disposed in the lower part of the heating chamber 2, and this turntable 4 is driven by a motor 5 as a load. It is designed to be rotated. A ground rod 7 is connected to the microwave main body 1 via a ground wire 6.
is connected. Reference numeral 8 denotes an operation panel attached to the front right side of the microwave main body 1, and a printed wiring board 9 is attached to the back side of the operation panel.

Now, the electrical configuration will be described according to FIGS. 1 and 3. Reference numeral 10 denotes a control power transformer attached to the printed wiring board 9, and both terminals of its secondary coil IOP are connected to load side lands llb and 12b of power conductor patterns 11° and 12 printed on the printed wiring board 9.
It is connected to the. In addition, power supply conductor pattern 11.12
The power supply side lands lla and 12a of the power supply side land 12a are connected to both terminals 15.16 of the power supply plug via a power supply line 13.14.

Three terminals of the tapped secondary coil IOS of the control power transformer 10 are connected to a power terminal of the control circuit 17. This control circuit 17 includes a microcomputer 18 and is formed on a printed wiring board 9.
As is well known, the secondary coil I of the control power transformer 10
The cooking is controlled by obtaining a DC constant voltage from the AC voltage induced in the OS, and for example, the cooking key is pressed after the cooking time is set by a cooking time setting device (not shown). Then, the magnetron 3 and the motor 5 are energized via the drive circuit for a set time to operate.

On the other hand, 19 and 20 are a pair of discharge conductor patterns formed by printing on the printed wiring board 9, and their opposing sides are formed into a sharp point, and the gap G between the tops 19a and 2Oa is The dimensions are set to a few millimeters.

Then, the land 19b of one discharge conductor pattern 19
is connected to the range body 1 via the ground wire 21, and a resistor 22 is connected between the land 20b of the other discharge conductor pattern 20 and the land 11c of the power supply conductor pattern 11.
is connected.

Next, the operation of this embodiment will be explained.

If the microwave main body 1 is grounded, such as by embedding the ground rod 7 in the ground, even if static electricity charged on the temporary user flows into the microwave main body 1, the static electricity will be transferred to the ground wire 6. and discharge to the ground via the ground rod 7.

If the user forgets to ground the microwave oven main body 1 using the grounding rod 7 or the like as described above, if the static electricity charged on the user flows into the microwave oven main body 1, the static electricity will be transferred to the earth wire 21. The power supply conductor pattern 1 serves as one terminal of the control power transformer 10 via the discharge conductor pattern 19, a predetermined gap G, the discharge conductor pattern 20, and the resistor 22.
Discharge to 1. In this case, since the resistor 22 is connected between the discharge conductor pattern 20 and the power supply conductor pattern 11, the gear 7 between the discharge conductor patterns 19 and 20
The discharge voltage of the portion 16 is suppressed to a low level, and the surge current flowing to the power supply conductor pattern 11 via the resistor 22 is also suppressed to a low level.

As mentioned above, even if the discharge voltage at the gear 716 portion is suppressed to a low level, the discharge conductor pattern 19°20 is formed into a sharp-pointed shape having the tops 19a and 20a, and the gap G is made extremely small, a few millimeters. , the static electricity is sufficiently discharged at the gear 716 portion.

Moreover, the surge current flowing through the power supply conductor pattern 11 is suppressed to a low level, and the control power transformer 10 has a voltage of 12 or 5 Since it has a transformation ratio that obtains a small AC voltage of volts, the surge current on the secondary coil LOP side is transferred to the secondary coil 10.
There is no effect on the S side, and therefore there is no adverse effect on the microcomputer 18 of the control circuit 17 connected to the secondary coil IOS side.

According to this embodiment, the following effects can be obtained. In other words, if you forget to ground the microwave main body 1 and static electricity flows through the microwave main body 1,
The static electricity is transferred to the ground wire 21° discharge conductor pattern 19.
Since the discharge is made to the power supply conductor pattern 11, which is one terminal of the control power transformer 10, through the gap G of 20 and the resistor 22, there is no possibility that the microcomputer 18 of the control circuit 17 will be adversely affected, such as malfunction or destruction. It is possible to reliably prevent this from happening. Then, a pair of discharge conductor patterns 19 and 20 are formed on the printed wiring board 9 by printing, and a resistor 22, which is an extremely low-cost electrical component, is connected between the discharge conductor pattern 20 and the power supply conductor pattern 11. Since it is a one-piece structure, the structure is simple and the cost can be reduced compared to the conventional one.

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, but can be modified as appropriate without departing from the scope, such as being applicable not only to microwave ovens but also to microcomputer-controlled electrical equipment in general. Of course, it can be implemented as follows.

[Effects of the Invention] As explained above, the microcomputer-controlled electrical equipment of the present invention discharges static electricity flowing into the main body of the equipment through the gap between the pair of discharge conductor patterns on the printed wiring board and the resistor. Since the discharge is made to one terminal of the primary coil in the transformer, it is possible to prevent the negative effect of static electricity on the microcomputer with a simple configuration, and it has the excellent effect of reducing the cost. be.

[Brief explanation of the drawing]

The drawings show an embodiment in which the present invention is applied to a microwave oven, in which Fig. 1 is a front view of the main parts of a printed wiring board, Fig. 2 is a schematic longitudinal sectional front view of the whole, and Fig. 3 is an electrical configuration. It is a diagram. In the drawing, 1 is the range body (equipment body), 3 is the magnetron (load), 5 is the motor (load), 7 is the earth rod, 9 is the printed wiring board, 10 is the control power transformer, 10P
10S is a primary coil, 10S is a secondary coil, 11 and 12 are power supply conductor patterns, 17 is a control circuit, 18 is a microcomputer, 19 and 20 are a pair of discharge conductor patterns, 22 is a resistor, and G is a gap. .

Claims (1)

[Claims] 1. a printed wiring board disposed within the device body; a control circuit formed on the printed wiring board including a microcomputer to control a load within the device body; and a control circuit provided on the printed wiring board that controls the control circuit. A control power transformer for supplying power, a pair of discharge conductor patterns formed on the printed wiring board with a predetermined gap between them, one of which is connected to the device main body, and the pair of discharge conductors. A microcomputer-controlled electrical device comprising a resistor connected between the other of the patterns and one terminal of the primary coil in the control power transformer.