JPH0676981A - Electronic equipment - Google Patents

Abstract

PURPOSE:To protect a semiconductor element on a printed circuit board against discharged static electricity. CONSTITUTION:The 18th resistor 71 and the 19th resistor 72 as connected to a power supply line are provided at a position nearest the edge of an upper frame where static electricity discharged due to the contact of a statically electrified hand with a grip, is further allowed to flow to a control printed circuit board 3n. In addition, a power supply line is provided to allow a flow of discharged static electricity to a timer dial 3b, upon contact of such a hand therewith. In this case, a cutout section is formed on a power supply line pattern from the dial 3b to a microcomputer 61, thereby increasing substantially the length of the power supply line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device having a printed circuit board.

[0002]

2. Description of the Related Art An electronic device having a conventional printed circuit board is provided with a protection circuit including a varistor or a Zener diode for protecting against overvoltage such as discharge or surge voltage when a contact is turned on / off. Are known.

However, protection against static electricity discharged when a metal frame of an electronic device is touched by static electricity in the dry season of winter has not been considered.

[0004]

Therefore, in the conventional electronic equipment, there is a problem that semiconductor elements such as ICs mounted on the printed circuit board may be destroyed by the discharged static electricity in the dry season of winter and the like. there were.

Therefore, an object of the present invention is to provide an electronic device capable of protecting a semiconductor element mounted on a printed board against discharged static electricity.

[0006]

The invention according to claim 1 is
The position of the electronic components mounted on the printed circuit board in an electronic device that has an electronic circuit configured by mounting electronic components such as semiconductor elements on the printed circuit board and that controls various driving elements by this electronic circuit It is provided with a conductor which is arranged at a position where the distance from the member which is more likely to discharge static electricity is shorter than that and which is connected to the power supply line on the printed board.

According to a second aspect of the present invention, there is provided an electronic device having an electronic circuit configured by mounting an electronic component such as a semiconductor element on a printed board, and controlling the driving element by the electronic circuit to perform various processes. Configure a power supply line from a common power supply from electronic parts that easily discharge static electricity to electronic parts that are semiconductor elements on the printed circuit board, and provide notches in part to increase the distance of the power supply line. It has a long pattern.

[0008]

According to the invention of claim 1, when static electricity is discharged by, for example, a charged hand touching a member that is easily discharged, the discharged static electricity is placed in a position closer to the electronic component mounted on the printed circuit board. Guided by the body. The static electricity introduced to the conductor is discharged to the power supply line. Therefore, the semiconductor element mounted on the printed circuit board is not affected by static electricity due to the discharge to the power supply line, so that the semiconductor element can be protected.

According to a second aspect of the present invention, for example, when static electricity is discharged when a charged hand touches an electronic component that is easily discharged, the discharged static electricity is transferred from the electronic component to a semiconductor via a pattern forming a power supply line. Although it affects electronic parts made up of elements, since the distance of the power supply line is long due to the notch portion in the pattern, the influence of static electricity on the semiconductor element can be suppressed to a small level.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In this embodiment, the present invention is applied to an oven toaster, and FIG. 1 is a perspective view showing this oven toaster.

Reference numeral 1 denotes an apparatus main body. As will be described later, an upper heater is provided on the inner upper surface of the apparatus and a lower heater is provided on the lower surface thereof, and food to be heated is placed in the center of the apparatus main body 1 between the respective heaters. A fence table 1a for mounting is provided. A plug cord 1b for inputting a commercial AC power source is connected to the rear surface of the apparatus body 1.

On the front surface of the apparatus main body 1, there is provided a door 2 which is opened when the food is placed on the fence table 1a and is closed when the food is heated. This door 2
Is formed by fitting a transparent plastic 2a into a metal frame 2b so that the heating state of the food placed on the fence table 1a can be observed. Further, a handle 2c for opening and closing is provided on the upper portion of the door 2.

An operation unit 3 is provided under the door 2 on the front surface of the apparatus body 1. In this operation unit 3, the heater output is set to weak, medium, and high in sequence with each press of the heater, and a heater adjustment switch 3a, a timer volume 3b for setting a heating time, and a timer cooker. The timer cooking switch 3c that is pressed when performing the baking, the baking color volume 3 for setting the baking color when the automatic baking is performed
d. Automatic baking switch 3 that is pressed when performing automatic baking
e is provided, and a weak lamp 3f, a medium lamp 3g, and a strong lamp 3h that display the degree (weak, medium, strong) of the heating output of each heater set by the heater adjustment.
And a 1-minute lamp (lights up when 1 minute or more and less than 5 minutes) 3i, 5 minutes lamp (lights up when 5 minutes or more and less than 10 minutes) that displays the heating time set by the timer volume 3b
3j, a 10-minute lamp (lights for 10 minutes or more) 3k, and an automatic baking lamp 3m that lights up when the automatic baking switch 3e is pressed down are provided.

FIG. 2 shows a part of the apparatus main body 1 and the door 2
3 shows a cross-sectional structure of the operation unit 3.

Inside the operation unit 3, a control printed circuit board 3n on which the respective switches, the respective volumes, and the light emitting diodes forming the respective lamps are mounted, and electrically connected to the control printed circuit board 3n. A printed circuit board 3p for power supply is provided. These printed circuit boards are protected by a metal front frame 3r and a top frame 3s.

FIG. 3 shows a circuit configuration of a main part of this oven toaster.

The commercial AC power source (AC100V) 31 input by the plug cord 1b has an upper heater 32,
A series circuit including a lower heater 33 and a normally open contact 34 of the relay is connected, and a varistor 36 is connected via a first resistor 35.

One end of a second resistor 37 is connected to the connection point between the first resistor 35 and the varistor 36, and the other end of the second resistor 37 is connected to the first Zener diode 38.
Of the second Zener diode 39 and the positive terminal of the smoothing capacitor 40. These first Zener diode 38, second
A rectifying / smoothing circuit is configured by the Zener diode 39, the smoothing capacitor 40, etc., and a DC current is supplied from the connection point between the other end of the second resistor 37 and the rectifying / smoothing circuit to various control circuits described later. To be done.

In the rectifying and smoothing circuit, a stabilizing first capacitor 41 and a second capacitor 42 are connected in parallel to the Zener diodes 38 and 39, respectively, and the anode terminal of the first Zener diode 38 is Third
Is connected to the connection point between the lower heater 33 and the normally-open contact 34 via a resistor 43 and a first diode 44, and the commercial AC is connected via a fourth resistor 45 and a second diode 46. It is connected to the power supply 31. Further, the anode terminal of the second Zener diode 39 is connected to the base terminal of the PNP type first transistor 47, and the anode terminal of the first Zener diode 39 is connected via the fifth resistor 48. It is connected to the. The collector terminal of the first transistor 47 is connected to the anode terminal of the first Zener diode 39 via a sixth resistor 49, and the emitter terminal of the first transistor 47 is output from this rectifying / smoothing circuit. It becomes the ground of the constant voltage DC power supply. The-terminal of the smoothing capacitor 40 is connected to the emitter terminal of the first transistor 47 as its ground.

At the output terminal of the DC current output from the rectifying / smoothing circuit, that is, at the connection point between the other end of the second resistor 37 and the + terminal of the smoothing capacitor 40, there is PN.
The emitter terminals of the P-type second transistor 50 and the PNP-type third transistor 51 are connected, and the seventh
The respective base terminals are connected via the resistor 52 and the eighth resistor 53.

The collector terminal of the second transistor 50 is connected to the first Zener diode 38 via a series circuit of a buzzer oscillator 55 and a tenth resistor 56, to which a ninth resistor 54 is connected in parallel. The collector terminal of the third transistor 51 is connected to the anode terminal, and the collector terminal of the third transistor 51 is connected via the series circuit of the exciting coil 58 and the eleventh resistor 59 of the relay to which the third diode 57 is connected in parallel. Is connected to the anode terminal of the Zener diode 38. The exciting coil 58 and the eleventh
A third capacitor 60 is connected between the connection point with the resistor 59 and the emitter terminal of the second transistor 51.

A constant voltage DC current is supplied from the rectifying / smoothing circuit to a microcomputer 61 as a semiconductor element which constitutes the main body of the control section through a power supply line 62. An output terminal for outputting a low level signal when the buzzer oscillator 55 of the microcomputer 61 sounds the buzzer is connected to the base terminal of the second transistor 50 via a twelfth resistor 63, and the upper heater is also connected. 32 and the output terminal for outputting a low level signal when energizing the lower heater 33,
It is directly connected to the base terminal of the third transistor 51.

Further, according to the state of the heater heating output input by the heater adjusting switch 3a, any one of the three output terminals of the microcomputer 61 for outputting a low level signal is composed of a light emitting diode. It is connected to the cathode terminals of the weak lamp 3f, the medium lamp 3g and the strong lamp 3h. The anode terminals of the weak lamp 3f, the medium lamp 3g, and the strong lamp 3h are all connected to the power supply line 62 via a thirteenth resistor 64.

Further, the output terminal for outputting a low level signal when the automatic baking switch 3e of the microcomputer 61 is pressed is connected to the cathode terminal of the automatic baking lamp 3m, and the timer cooking switch 3c is pressed. An output terminal for outputting a low level signal when the lamp is turned on is connected to a cathode terminal of a timer cooking lamp 65 formed of a light emitting diode. The anode terminals of the automatic baking lamp 3m and the timer cooking lamp 65 are both connected to the power supply line 62 via a fourteenth resistor 66.

Further, according to the heating time set by the timer potentiometer 3b, any one of the three output terminals of the microcomputer 61 for outputting a low level signal is a light emitting diode.
It is connected to the cathode terminals of the minute lamp 3k, the 5 minute lamp 3j and the 1 minute lamp 3i. The anode terminals of the 10-minute lamp 3k, the 5-minute lamp 3j, and the 1-minute lamp 3i are all connected to the power supply line 62 via a fifteenth resistor 67.

The movable terminal of the timer potentiometer 3b is connected to the timer setting input terminal of the microcomputer 61 via a sixteenth resistor 68, and the two fixed terminals are respectively connected to the power supply line 62 and the ground. It is connected to the. Also, the timer volume 3b
The package is provided with a metal package frame, which is connected to the power supply line and to the ground via the third Zener diode 69.

The movable terminal of the baking color control 3d is connected to an input terminal for heater adjustment through a seventeenth resistor 70, and two fixed terminals are connected to the power supply line 62 and the ground, respectively. ing.

The 18th resistor 71 and the 1st resistor as a conductor
The resistors 72 of 9 are connected to the power supply line 62 in a loop shape.

FIG. 4 shows the arrangement (a) of electronic components on the mounting surface of the control printed circuit board 3n and the pattern (b) of the pattern surface projected from the mounting surface.

Notches A and B are provided at both upper ends of the control printed circuit board 3n, and the notches A and B are provided.
An edge portion (not shown) provided on the upper surface frame 3s is inserted into this.

Reference numeral 81 is a connector for inputting and outputting a power source and various signals, and the control printed circuit board 3n is electrically connected to the power source printed circuit board 3p by this connector.

In this embodiment having such a structure, for example, when the handle 2c of the door 2 is touched with a charged hand and static electricity is discharged from the handle 2 to the frame 2b, the discharged static electricity is applied to the frame 2b of the door 2. And top frame 3s
Or it flows to the front frame 3r.

Furthermore, the static electricity that has flowed to the upper surface frame 3s is easily discharged to the control printed circuit board 3n through the edge portion. If static electricity is discharged from the edge portion, the static electricity is guided to the eighteenth resistor 71 or the nineteenth resistor 72 mounted at the position closest to this edge portion. Therefore, the static electricity introduced to the eighteenth resistor 71 or the nineteenth resistor 72 is discharged to the commercial AC power supply 31 via the power supply line 62, the second resistor 37, and the first resistor 35.

Also, with a charged hand, the timer volume 3
When the package frame of b is touched and static electricity is discharged to the package frame of the timer volume 3b, the discharged static electricity is supplied through the power supply line 62, the second resistor 37 and the first resistor 35 to the commercial AC power supply. 31 is discharged. Further, the pattern of the power supply line from the connection point of the power supply line 62 to which the frame of the timer volume 3b is connected to the connection point of the power supply line 62 of the microcomputer 61 is enlarged as shown in FIG. The upper and lower portions of the pattern are alternately provided with notches to substantially lengthen the power supply line. That is, the conventional pattern shown in FIG. 6 is changed to the pattern shown in FIG. 5 by providing a notch. Therefore, since the length of the power supply line is increased, the influence of static electricity on the microcomputer 61 is reduced.

As described above, according to this embodiment, the static electricity discharged when the charged hand touches the handle 2c is the closest position to the edge portion of the upper frame 3s which is further discharged to the control printed circuit board 3n. An eighteenth resistor 71 and a nineteenth resistor 72 are provided to be connected to the power supply line 62, and when the charged hand touches the timer volume 3b, the static electricity discharged to the timer volume 3b flows through the power supply line. In 62, a notch is formed in the pattern of the power supply line from the timer volume 3b to the microcomputer 61, and the length of the power supply line is substantially lengthened, so that the control printed circuit board 3n is provided. The mounted microcomputer 61
The influence of static electricity on the static electricity can be reduced, and therefore the microcomputer 61 can be protected from static electricity.

Although a resistor is used as a conductor in this embodiment, the present invention is not limited to this, and various conductors such as a test pin may be used. Further, the effect can be enhanced by using a taller conductor. Further, although the pattern of the power supply line is modified to the shape shown in FIG. 5, the present invention is not limited to this, and the notch is formed so as to substantially lengthen the length of the power supply line. If a part is provided, it is applied.

[0037]

As described above in detail, according to the present invention,
It is possible to provide an electronic device capable of protecting a semiconductor element mounted on a printed board against discharged static electricity.

[Brief description of drawings]

FIG. 1 is a perspective view of an oven toaster showing an embodiment of the present invention.

FIG. 2 is a sectional view of a part of an apparatus main body and an operation unit showing the embodiment.

FIG. 3 is a diagram showing a circuit configuration of a main part of the embodiment.

FIG. 4 is a diagram showing a mounting state of a mounting surface of a manufacturing printed board of the embodiment and a diagram showing a pattern of a pattern surface projected from the mounting surface.

FIG. 5 is a diagram showing a pattern of the embodiment.

FIG. 6 is a diagram showing a pattern of a conventional example.

[Explanation of symbols]

2 ... Door, 2b ... Frame, 2c ... Handle, 3b ... Timer volume, 3n ... Control printed circuit board, 3s ... Top frame, A, B ... Notch.

Claims (2)

[Claims] 1. An electronic device having an electronic circuit configured by mounting an electronic component such as a semiconductor element on a printed circuit board, which controls a driving element by the electronic circuit to perform various processes, mounted on the printed circuit board. An electronic device provided with a conductor which is arranged at a position shorter than a position where the static electricity is discharged more easily than a position of the electronic component, and which is connected to a power supply line on the printed circuit board. 2. An electronic device having an electronic circuit configured by mounting an electronic component such as a semiconductor element on a printed circuit board, which controls a driving element by the electronic circuit to perform various processes, on the printed circuit board. Configure a power supply line from a common power source from electronic parts that easily discharge static electricity to electronic parts consisting of semiconductor elements, and provide a pattern in which a notch is provided in part to increase the distance of the power supply line. An electronic device characterized by being provided.