JPH0960884A - Switch device for electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an in-rush current from being generated without using any cement resistor. SOLUTION: This electronic equipment is set such that a power supply transformer 5 having a magnetron 15 connected thereto and a heater 28 are connected in parallel in respect to a power supply 1 through a selector switch 3. Then, in the case that terminals d-a of the selector switch 3 are connected to cause the power supply transformer 5 and the power supply 1 to be connected to each other, terminals c-a of each of the changing-over switches 7, 8 are connected to cause the heater 28 to be connected in series with the power supply transformer 5. In addition, as a capacitor C in a connecting circuit 10 is charged through the connection of the terminals d-a of the selector switch 3, a connection between each of the changing-over switches 7, 8 is changed over to the terminals c-b through a second relay coil L2. That is, after elapsing a specified time when the capacitor C is charged, the series-connection between the heater 28 and the power supply transformer 5 is released and then the power supply 1 is supplied to the magnetron 15 through the power supply transformer 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device in which a power transformer connected to a magnetron and a heater are connected in parallel to a power source via a selection switch, and more specifically, the selection switch is connected to the magnetron side. The present invention relates to a switch device of an electronic device capable of preventing an inrush current when the battery is turned on and connected to a power supply.

[0002]

2. Description of the Related Art Electronic equipment (for example, cooking equipment such as microwave oven) equipped with a power transformer connected to a magnetron
In the case of turning on the power switch to supply power to the magnetron, a large inrush current flows through the power transformer when the power is turned on. For example, the output is 800 ~
In a microwave oven of about 900 W, 80 to 1 when the power is turned on.
A current of about 30 A flows.

For this reason, the breaker for home use will fall down as it is. Therefore, in the conventional microwave oven, a cement resistor, which is a winding resistor, is connected in series to a power transformer when the power is turned on, and an inrush current is generated. I try not to let it flow in the transformer. Then, after the lapse of the inrush current generation period, the cement resistor is disconnected from the power transformer, and thereafter, the power is stably supplied to the magnetron through only the power transformer.

[0004]

As described above, in the conventional microwave oven, the cement resistance is used to prevent the inrush current from flowing when the power is turned on, but the cement resistance has a small resistance value. Since I am using one, there was a problem that the wattage became large. In addition, some manufacturers do not have a sufficient resistance value against inrush, and there is a problem that they cannot be used uniformly. Further, since the cement resistor is used only to prevent the inrush current, there is a problem that the cost of parts is increased accordingly.

The present invention was devised to solve such problems, and an object thereof is to provide a switch device for electronic equipment which can prevent the occurrence of inrush current without using cement resistance. It is in.

[0006]

In order to solve the above problems, a switching device of the present invention is an electronic device in which a power transformer connected to a magnetron and a heater are connected in parallel to a power source via a selection switch. When the selection switch is turned on to the magnetron side and connected to the power source, the heater is connected in series with the power transformer to supply power to the magnetron through the heater and the power source transformer. After a lapse of a certain time after the selection switch is turned on, a connection switching circuit that supplies power to the magnetron through the power transformer by disconnecting the series connection of the heater and the power transformer is provided. is there.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in the state of being incorporated in a microwave oven. 2 and 3 are a side sectional view and a plan sectional view showing an example of the structure of the microwave oven to which the switch device of the present invention is applied. An opening / closing door 22 is attached to the front surface of the range main body 21, and the inside of the opening / closing door 22 is a heating chamber 23.

A waveguide 25 is provided on the upper surface plate 24 of the heating chamber 23 so as to extend to the central portion thereof, and the waveguide 25 is arranged outside the right side of the heating chamber 23. Further, it is connected to a high-frequency generator 26 having a built-in magnetron 15 and the like. A stirrer 27, which is covered with a stirrer cover 28, is attached to the lower surface side of the upper surface plate 24 (that is, the inside of the heating chamber 23) and to the opening of the waveguide 25. The high frequency wave guided through the waveguide 25 is applied to the heating chamber 23 while being diffused by the stirrer 27.

An upper heater 29, which is an electric sheath heater, is attached to the lower surface of the upper plate 24, and a rear heater 32 is provided in a heater case 31 attached to the rear plate 30 of the heating chamber 23. It is installed.
Further, the blower motor 33 is attached to the rear surface of the heater case 31 via the motor bracket 34, and the blower fan 35 and the cooling fan 36 driven by the blower motor 33 are also attached.

When the microwave oven is used as an oven, the inside of the heating chamber 23 is heated by the radiant heat from the upper heater 29, and the air heated by the rear heater 32 is exhausted above and below the rear plate 30. A blower fan 35 blows air into the heating chamber 23 through the ports 37 and 38. Further, the blower motor 33 is cooled by the cooling fan 36.

On the front surface of the range main body 21, an operation plate 39 is provided on the right side of the opening / closing door 22, and the operation plate 39 is provided.
Although not shown in the figure, a display window, a power switch 2, a selection switch 3 for selecting either oven or range, and other various function switches are provided.

FIG. 1 shows the electrical construction of the switch device of the present invention applied to the microwave oven having the above construction. The common terminal d of the selection switch 3 is connected to the power supply 1 via the power supply switch 2. Select switch 3 is 3
It has two fixed terminals a to c, of which fixed terminal c
Is an open end.

The fixed terminal a of the selection switch 3 is connected to one end of a primary side coil 51 of a high frequency generating power transformer 5 via a normally open switch 4, and the other end of the primary side coil 51 is connected to a signal line. It is connected to the power supply 1 via the line 6. The magnetron 15 is connected to the secondary coil 52 of the power transformer 5. The fixed terminal b of the selection switch 3 is the fixed terminal b of the first changeover switch 7.
Connected to the common terminal c of the first changeover switch 7.
Is connected to one end of the upper heater 28 (or the rear heater 31). The fixed terminal a of the first changeover switch 7 is
It is connected to the power supply 1 via the power switch 2.

The other end of the upper heater 28 is connected to the common terminal c of the second changeover switch 8, and the fixed terminal b of the second changeover switch 8 is connected to the signal line 6. The fixed terminal a of the second changeover switch 8 is connected to one end of the primary coil 51 of the power transformer 5. Further, the fixed terminal a of the selection switch 3 is connected to the connection switching circuit 10 via the resistor R and the backflow prevention diode D1.

The connection switching circuit 10 comprises a parallel circuit including a first relay coil L1, a second relay coil L2, a capacitor C and a Zener diode D2. The first relay coil L1, the second relay coil L2, one end of the capacitor C, and the cathode side of the Zener diode D2 are connected to the cathode side of the backflow prevention diode D1. The other end of the second relay coil L2, the capacitor C, and the anode side of the Zener diode D2 are connected to the signal line 6.

In the above structure, the first changeover switch 7
In the second changeover switch 8, the common terminal c is normally connected to the fixed terminal b side, and the common terminal d of the selection switch 3 is changed over from the fixed terminal b or c to the fixed terminal a side. When it is turned on, it is configured to switch to the fixed terminal a side in conjunction with this. Further, the first changeover switch 7 and the second changeover switch 8 are relay switches, and when a current flows through the second relay coil L2, the common terminal c is forcibly switched to the fixed terminal b side. Has become. Further, the normally open switch 4 is also a relay switch, and the switch is closed only while the current is flowing through the first relay coil L1.

Next, the operation of the switch device having the above configuration will be described. Before using the microwave oven, the selection switch 3 is connected to the fixed terminal c, and the common terminals c of the first changeover switch 7 and the second changeover switch 8 are connected to the fixed terminal b side. Has been done. In this state, when the power switch 2 is turned on and then the common terminal d of the selection switch 3 is connected to the fixed terminal a side which is the range side, the first changeover switch 7 and the second changeover switch are interlocked with this. Each common terminal c of the switch 8 is switched to the fixed terminal a side.

As a result, the fixed terminal a of the selection switch 3
At the time of connection to the side, the power source 1, the power switch 2, the terminals ac of the first changeover switch 7, the upper heater 28, the terminal ca of the second changeover switch 8, the primary side coil 51 of the power transformer 5, The signal line 26 constitutes a closed circuit. That is, the upper heater 28 is connected in series to the power transformer 5.

This has the same result as connecting the cement resistors used in a conventional microwave oven or the like in series, and can prevent a large inrush current flowing when the power source 1 is supplied to the magnetron 15. It will be. Further, at this time, the connection switching circuit 10 is also connected to the power source 1, but the current from the power source 1 remains constant for a certain period after the connection (several millisecond when the inrush current stops flowing).
During about (c), the capacitor C is charged and does not flow to the relay coils L1 and L2. Therefore, until the capacitor C is charged, each changeover switch 7,
The connection of 8 is kept at terminal ca, and the normally open switch 4 is kept open.

When the capacitor C is charged, a current then flows through the relay coils L1 and L2. At that time, therefore, the changeover switches 7 and 8 are connected so that the common terminal c is forced to the fixed terminal b side. And the normally open switch 4 is turned on. Therefore, thereafter, the power supply 1, the power switch 2, the terminal da of the selection switch 3, the normally open switch 4, the primary coil 51 of the power transformer 5, and the signal line 26 form a closed circuit. That is, the upper heater 28 is restored to the normal circuit configuration separated from the power transformer 5.

The selection switch 3 is connected to the fixed terminal a.
, The common terminal c of the first changeover switch 7 and the second changeover switch 8 maintains the state of being connected to the fixed terminal b side. When the terminal d is connected to the fixed terminal b, it can be used as a normal oven.

[0022]

The switch device of the present invention is an electronic device in which a power transformer to which a magnetron is connected and a heater are connected in parallel to a power source through a selection switch,
When the selection switch is turned on to the magnetron side and connected to the power supply, the heater is connected in series with the power transformer to supply power to the magnetron via the heater and power supply truss, and a certain time has elapsed after the selection switch was turned on. After that, the series connection between the heater and the power transformer was released to supply the power to the magnetron via the power transformer, so a large inrush that flows when the power is supplied to the magnetron. The current can be prevented. Also, since the heater is connected to the power transformer in series,
The cement resistance that was used in the past becomes unnecessary, and the cost can be reduced accordingly.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of a switch device of the present invention.

FIG. 2 is a side sectional view showing an example of the structure of a microwave oven to which the switch device of the present invention is applied.

FIG. 3 is a cross-sectional view seen from a plane showing an example of the structure of a microwave oven to which the switch device of the present invention is applied.

[Explanation of symbols]

 1 power supply 2 power supply switch 3 selection switch 5 power supply transformer 7 first changeover switch 8 second changeover switch 10 connection changeover circuit 15 magnetron 28 upper heater

Claims (1)

[Claims] 1. An electronic device in which a power transformer connected to a magnetron and a heater are connected in parallel to a power source via a selection switch, when the selection switch is turned on to the magnetron side and connected to the power source. By connecting the heater in series with the power transformer, power is supplied to the magnetron via the heater and the power transformer, and the heater and the power source are turned on after a certain time has passed after the selection switch was turned on. A switch device for an electronic device, comprising a connection switching circuit that supplies power to the magnetron through the power transformer by releasing a series connection with the transformer.