JP2002329574A - Microwave oven - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive microwave oven by mounting a component for suppressing a rush current surge generating in input of a power source on one printed board with a general small electronic component by constituting a power source circuit having no transformer. SOLUTION: A power source circuit of a relay unit RU1 is connected in series to a fan motor MT1 and a turn table motor MT2, and then connected to an AC power source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave oven for driving a control circuit of a magnetron with a DC power supply.

[0002]

2. Description of the Related Art In a specific European country (Germany), there are areas where a power breaker installed in a general home is particularly sensitive, and this power breaker may be cut off by an inrush current when a microwave oven is turned on. . Therefore, in a conventional circuit, a circuit element for suppressing the inrush current has been employed in a main power supply circuit of a microwave oven.

FIG. 20 shows a conventional circuit of a microwave oven employing a motor timer. Immediately before the high voltage transformer HT1, the relay contact of the AC surge relay RA1 and the surge resistor R3
Is inserted. With this, a pre-excitation current is applied to the high-voltage transformer HT1 via the surge resistor R3 using a time difference of about 6 to 20 msec between the start of the heating operation of the microwave oven and the time when the relay contact of the AC surge relay RA1 is closed. In addition, the rush current when the relay contact is closed is suppressed. As an example of the surge resistor R3, 10Ω20
W tungsten wire coil cement resistance was used. Further, in the present embodiment, 4.
A 3Ω20W tungsten wire coil cement resistor was connected in series with the 6.3A monitor fuse F1.

FIG. 21 shows another conventional circuit in which the surge resistor and the monitor resistor in FIG. 20 are combined into one. In this circuit, when the door is closed, the monitor switch SW3 forms a circuit in which the surge resistor R3a bypasses the surge relay contact via the monitor fuse F2, and the surge relay contact closes at the start of the heating operation of the microwave oven. During this time, a pre-excitation current is applied to the high voltage transformer HT1 to suppress the inrush current.

When the door is opened, the monitor switch SW3 is inverted to form a monitor circuit for diagnosing a contact opening abnormality of the first door switch SW1, and the surge resistance R
Reference numeral 3a functions as a monitor resistor for keeping the fusing current of the monitor fuse F2 within the rating.

In this circuit, compared to the circuit of FIG. 20, the breaking capacity of the monitor fuse can be reduced, the power capacity of the monitor fuse for suppressing the maximum fusing current is small, and a small one can be used. In this circuit, a monitor fuse of 1.6 A and a surge resistance of 20 Ω and 10 W are mounted on the extended portion of the printed circuit board of the noise filter NF1.

FIG. 22 shows a circuit in which the surge relay in the circuit of FIG. 21 is replaced with a DC power supply type from an AC power supply type. A power supply circuit including a low-voltage conversion transformer T1 and a rectifying element DB1 is used as a relay driving power supply. By the replacement with the DC relay RD1, the accuracy of the time difference from the start of the heating operation of the microwave oven to the operation of the relay contact is improved, and the effect of suppressing the rush current is stabilized.

FIG. 23 shows a circuit in which the bleeder resistor R60 is used as a power supply circuit for the DC relay RD1 in the circuit of FIG.

[0009]

In the above-mentioned conventional circuit, a surge relay and a surge resistor are used for pre-exciting the high-voltage transformer HT1 in order to suppress an inrush current at the beginning of operation of the microwave oven.

The surge resistance withstands the energizing energy of the pre-excitation current (eg, about 15 A, maximum 20 msec) of the high-voltage transformer HT1, and in the circuit of FIG.
In the 3A type monitor fuse, the circuits shown in FIGS. 21 to 23, for example, the T1.6A slow blow type monitor fuse must endure the energizing energy for surely blowing the monitor fuse, and has a large power withstand power (10Ω20W or 2Ω).
0 Ω 10 W). For this reason, the element size becomes large, and the method of mounting inside the microwave oven is either printed circuit board mounting or direct mounting to the microwave oven main body with individual brackets, which is a concern from the viewpoint of reducing the number of production and assembly steps and costs of the microwave oven. It should have been an item.

[0011] The contact operation time of the AC surge relay varies greatly depending on the phase of the AC power supply voltage at the time when the relay coil power is turned on. In the conventional circuit, 6msec ~ 20msec
It is. This relay operation time is the pre-excitation time of the high-voltage transformer HT1, but the delay time of about 8 msec by the relay for effectively suppressing the rush current is sufficient, and when it falls within about 8 msec ± 2 msec, the surge resistance is reduced. Maximum power stress can be reduced.

Therefore, by replacing the AC surge relay with a DC surge relay, the relay contact operating time is reduced to 8 hours.
It is stable in about msec and has the advantage that a low cost general type relay can be adopted in terms of cost.
Obtaining a low-voltage power supply was an obstacle.

An object of the present invention is to provide a transformerless power supply without using a conventionally used low-voltage transformer or bleeder resistor, and to mount general-purpose small electronic components on the same circuit board. Accordingly, an object of the present invention is to provide a low-cost microwave oven.

[0014]

According to a first aspect of the present invention, there is provided a microwave oven provided with a magnetron, comprising: a fan motor driven by an AC power supply; A power supply circuit of a magnetron driven by the AC power supply, an open / close contact for supplying power to the power supply circuit, and open / close means for opening / closing the open / close contact; connecting a rectifying element in series with the fan motor; A circuit configuration is provided in which a direct current flows through a series circuit of the opening / closing means and the fan motor by an element.

A microwave oven according to a second aspect of the present invention comprises:
In a microwave oven equipped with a magnetron, a turntable motor driven by an AC power supply, a power supply circuit of the magnetron driven by the AC power supply, an open / close contact for supplying power to the power supply circuit, and open / close the open / close contact. Opening / closing means, a rectifying element connected in series with the turntable motor, and a rectifying element configured to supply a direct current to a series circuit of the opening / closing means and the turntable motor. .

A microwave oven according to a third aspect of the present invention comprises:
In a microwave oven provided with a magnetron, an oven lamp driven by an AC power supply to indicate that the magnetron is operating, a power supply circuit of the magnetron driven by the AC power supply, an open / close contact for supplying power to the power supply circuit, An opening / closing means for opening / closing an opening / closing contact, wherein a rectifying element is connected in series with the oven lamp, and the rectifying element has a circuit configuration for supplying a direct current to a series circuit of the opening / closing means and the oven lamp. Features.

[0017]

FIG. 2 shows the appearance of a microwave oven for Northern Europe according to a first embodiment of the present invention. On the control panel, a timer knob for setting the operation time and a door button for opening the door are arranged.

In this embodiment, the arrangement of the monitor fuse and the surge resistor is the same as that of the conventional circuit shown in FIG. 21, and the AC relay is replaced with a DC relay. In order to make the power supply circuit of the DC relay transformerless, a diode bridge is inserted in series with the fan motor coil of the microwave oven, and the DC relay is driven by a pulsating flow obtained by rectifying the fan motor current. That is, the bleeder resistance in the conventional circuit of FIG. 23 is replaced with the impedance of the fan motor coil.

In the case of a microwave oven for Northern Europe, the power supply is 220
V is 50 Hz, and to drive a DC relay of about 18 V DC, the current is suppressed to about 40 mA DC. If a bleeder resistor is used, the resistance value becomes about 5 kΩ, and the power value consumed by the resistor consumes about 8 W. ,
Practically, a bleeder resistance of 10 W to 15 W is required. In the case of the present embodiment, focusing on the fact that the steady-state current value of the fan motor is about 100 mA, this is rectified and divided by the parallel resistance with the DC relay to obtain D.
A C relay power supply was configured. Since the shunt resistance for DC relay current adjustment is about 1.5W to 2.0W, it is sufficient.
Compared to a bleeder resistor, the size is more suitable for mounting on a printed circuit board, and cost reduction is possible.

The fan motor has a power supply voltage of about 2
Although the rotation torque is reduced as a result of the voltage drop of 0 V, it is sufficiently possible to adjust the motor coil so as to be an induction motor and satisfy the internal air cooling effect as a microwave oven.

FIG. 1 shows a circuit of a microwave oven according to the present embodiment. The circuit configuration is such that the noise filter NF1 is disposed in the commercial power supply input section, and the main thermoelectric circuit up to the high-voltage transformer HT1 for driving the magnetron MG1 serves as an oven thermocut TH1 for protecting a microwave oven in the event of abnormal food heating in the oven, and a magnetron. A magnetron thermocut TH2 for protecting the MG1 from abnormal operation is provided, followed by a timer contact TC1, a first door switch SW1, a relay contact of a DC relay RD1 for surge suppression, and a second door switch SW2. .

Further, as auxiliary parts constituting the microwave oven, an oven lamp OL1, a timer motor TM1, a fan motor MT1 for air cooling, and a turntable driving motor M
T2 and a relay unit RU1 in which a DC relay RD1 and a power supply circuit according to the present invention are arranged.

In the configuration of the power supply circuit of the relay unit RU1, this type of conventional power supply circuit obtains a low-voltage power supply necessary for driving a DC relay by using a low-voltage transformer T1 shown in FIG. 22 or a bleeder shown in FIG. The power supply circuit is obtained by limiting the current with the resistor R6. However, in this circuit, the fan motor MT1 and the turntable motor MT2 are arranged in parallel, and the relay unit RU1
Is connected to an AC power supply of 220 V and 50 Hz in series with the power supply circuit of No. 1. Diode block DB for motor current
The current is rectified by 1 and shunted by a shunt resistor R5 to a current value necessary for driving the DC relay, thereby obtaining a DC relay power supply. As an example of a circuit design, the combined current consumption of the turntable motor MT2 and the fan motor MT1 is about 15 W, and the inductive load power factor is about 50%, and the current flows about 130 mA. Therefore, if a DC relay having a coil specification of 18 V and 40 mA is adopted, the shunt resistance R5 needs to be about 200Ω3W.

In order to comply with safety standards, the contact welding of the first door switch SW1 is monitored, and at the time of contact welding, the monitor fuse F2 is blown off, so that a monitor switch SW3 for stopping the operation of the microwave oven is provided. And a monitor resistor R3 for adjusting the maximum fusing current of the monitor fuse F2 to a rated value.

A high voltage power supply circuit for driving the magnetron MG1 for microwave power conversion includes a high voltage transformer HT1, a high voltage capacitor HC1 for voltage doubling rectification,
A high-voltage diode HD1 and a high-voltage current fuse HF1 for protecting a high-voltage circuit short-circuit abnormality are provided.

The contacts of the first door switch SW1 and the second door switch SW2 in the circuit of FIG. 1 indicate that the door is closed. When the timer knob is wound up for setting the time of the timer motor TM1, the timer contact TC1 is closed, the monitor fuse F2 in the relay unit RU1,
A power supply is connected to the fan motor MT1 and the turntable motor MT2 via the fuse resistor F3 for circuit protection, the rectifier diode block DB1, and the coil of the DC relay RD1.

The DC relay RD1 has a predetermined time of about 8 ms.
Close relay contacts after ec. During the delay time until the relay contact is closed, the primary excitation coil of the high voltage transformer HT1 is connected to the primary coil of the high voltage transformer HT1 via the monitor fuse F2, the monitor resistor R3, and the com-no contact of the monitor switch SW3. Flows with the rush current suppressed by the monitor resistor R3. Next, DC relay R
When the relay contact of D1 is closed, a steady operation current starts to flow in the high voltage circuit. However, since the core of the high voltage transformer HT1 has already been pre-excited, the initial operation is compared with the case where the residual magnetic field is opposite to the polarity of the initial excitation. Is a sufficiently low value. Here, when the door is closed by the switching operation of the monitor switch SW3, the monitor resistor R3 functions as a surge suppression resistor. When the door is opened, the monitor resistor R3 is connected to the monitor fuse F2 via the com-nc contact. It functions as a monitor circuit for the first door switch SW1.

In the circuit shown in FIG. 1, the monitor circuit and the surge current suppressing circuit are composed of the same parts, and the monitor resistance value and the monitor fuse capacity are required to function sufficiently reliably as respective circuit parts. Is done. Therefore, in this embodiment, the monitor fuse F2 has a slow blow type [T] of T1.6A, and the monitor resistor R3 has a resistance of 20Ω.
A winding resistance of 10 W was employed.

The safety test items based on the requirements of the microwave oven safety standards include a short-circuit short-circuit test for components. Therefore, in the present embodiment, even when the fan motor MT1 is short-circuited or the circuit components are short-circuited, power is not supplied to the high-voltage transformer HT1, so that safety as a microwave oven can be ensured. That is, the fan motor MT
When 1 is short-circuited, the commercial power supply voltage is applied to the relay coil of the DC relay RD1 and the resistor R5 for adjusting the relay power supply. As a result, a current exceeding about 1 A flows, and several tens of times the steady power is consumed by the fuse resistor F3, and the circuit is opened after a few seconds. As an example of the fuse resistor F3,
In the case of 10Ω 1 / 4W, the steady operation power is about 0.1W, but when the fan motor MT1 is short-circuited, the power consumption is 10W, and the power is about 40 times the rated power.
In about a second, the fuse resistor F3 cuts off the circuit and the DC relay R
D1 cannot be driven. Relay unit RU1
Similarly, when the circuit components are short-circuited, the DC relay RD1
Since the power source cannot be configured and the relay contact cannot be driven, the microwave heating operation of the microwave oven cannot be performed.
Therefore, in any state, the operation of the microwave oven is stopped, and safety can be ensured.

As described above, in the present embodiment, a DC relay is used to suppress an inrush current when the power is turned on, and the DC power supply of the control circuit is connected in series with the fan motor. A conventionally used low-voltage transformer or a transformerless power supply that does not use a bleeder resistor can be configured. Therefore, by mounting a monitor fuse and a monitor resistor that also serves as a surge suppressor on the same circuit board, a low-cost circuit configuration can be realized.

FIG. 3 shows the appearance of a microwave oven for Northern Europe according to a second embodiment of the present invention. On the control panel, a timer knob for setting the operation time, an output adjustment knob for adjusting the output, and a door button for opening the door are arranged.

In the microwave oven according to the present embodiment, when the DC relay is driven in the microwave oven according to the first embodiment, the relay contact is closed when the inrush current at the time of turning on the power of the microwave has a power supply voltage phase angle that can minimize the most. It is characterized by the following.

By using a DC relay as a surge relay, the fluctuation of the operation time delay characteristic of the relay contact is limited, and the relay contact is closed in synchronization with the voltage phase of the power supply, so that an inrush current at power-on can be suppressed. No surge resistor is required.

Normally, a magnetic leakage type high voltage transformer HT1 is employed as a high voltage power supply for a microwave oven. During operation, the current phase of the input power supply is approximately 90% of the voltage phase.
° Late. Accordingly, when the power supply voltage has a maximum value, that is, when the power supply voltage waveform is a sine function, when the power supply is turned on when the voltage phase angle is 90 °, the current value rises from 0 A, and the rush current becomes a minimum. In reality, the rush current does not become extremely small depending on the degree of the residual magnetic field of the core of the high-voltage transformer HT1 and the direction of the magnetism, but a sufficient peak value suppression effect in practical use is obtained.

The DC relay power supply and the relay control circuit power supply
As in the first embodiment, a transformerless power supply is obtained by dividing the voltage of 220 VAC using a resistor inserted in series with the fan motor.

Further, in the circuit of the present embodiment, a duty control contact built in a motor timer is connected to control the duty of turning on / off the DC relay at a predetermined cycle when the DC relay is driven. Has a variable microwave output function.

FIG. 4 shows a circuit of a microwave oven according to this embodiment. The relay contact is closed in synchronization with the phase of the power supply voltage between the power supply circuit portion of the DC relay RD1 configured in series with the fan motor MT1 and the turntable motor MT2 connected in parallel, and the relay coil. For controlling the inrush current to the high-voltage transformer HT1 when the power is turned on by performing the voltage phase control.

Therefore, the monitor resistor R3 does not need the function of suppressing the inrush current of the high-voltage transformer HT1, and only functions as a limiting resistor for keeping the maximum fusing current of the monitor fuse F2 within the specifications of the fuse. In the embodiment, the monitor fuse F2 is a coil type of F150 mA, and the monitor resistor F3 is a coil type of 150Ω3W. Thus, the monitor fuse F2 can be quickly blown when the monitor circuit is operating or the fan motor is short-circuited, and the safety of the microwave oven can be secured.

When the door is closed and the timer knob is wound up,
The timed contact TC1 of the timer closes and the oven lamp OL
1. Timer motor TM2 coil, relay unit RU
2. Power is connected to the fan motor MT1 and the turntable motor MT2 connected in parallel. Then, the phase control circuit applies a voltage to the relay coil of the DC relay RD1 at the several zero-cross timing of the input voltage, and the relay contact closes after a predetermined delay time of about 11.5 msec. The power supply of the relay unit RU2 is generated by the motor current of the inductive load, and the phase of the supplied voltage is about 3.3 msec from the voltage phase of the main power supply of the microwave oven.
Running late. Therefore, when the relay contact of the DC relay RD1 is closed at the timing of the maximum value of the main power supply voltage to the high voltage transformer HT1 in the case of the 50 Hz power supply, the rush current can be suppressed.

The monitor switch SW3 is a normally closed switch. When the door is closed, the contact is open. If the door is to be opened during operation of the microwave oven, the first door switch SW1 opens the main power supply circuit first, and then the second door switch SW
2 opens the main power supply circuit and stops the power supply to the high voltage transformer HT1 twice, and then closes the monitor switch SW3 at a predetermined position where the door starts to open. At this time, if the contact of the first door switch SW1 is in an abnormal state where the circuit cannot be opened due to welding or the like, the circuit is short-circuited by the monitor fuse F2, the monitor resistor R3, and the monitor switch SW3, and the monitor fuse F2 is instantaneously turned on. Blow. as a result,
The power supply to the relay unit RU2 is cut off, and the DC relay RD1 is disabled.

FIG. 5 shows a relay unit R according to this embodiment.
3 shows a circuit configuration of U2. The diode block DB1 of this circuit rectifies the AC operating current of the fan motor MT1. The current of this circuit is mainly divided into four currents.
The relay coil of the C relay RD1 is driven.

The current i1 is a current flowing through the shunt resistor R5 such that the relay coil driving current i3 of the DC relay RD1 becomes a predetermined rated operating current. Transistor T
When the DC relay RD1 is operating while R1 is on, the thyristor SR1 is turned off because no gate voltage is applied, and the current i2 does not flow. Therefore, the fan motor MT1 and the turntable motor M
About 130 mA of current of T2 is divided into current i1 and current i3. Using a DC relay having a coil specification of 18 V and 40 mA, the shunt resistance R5 was set to 280 Ω 3 W in consideration of the characteristics of the operation timing of the relay contact at the time of voltage reduction.

When the transistor TR1 is off, the current i2 is equal to the resistance of the relay coil of the DC relay RD1 and R10.
, A current flows to the gate of the thyristor SR1 and the current flows when the anode and the cathode of the thyristor SR1 are turned on. The current i2 flows in parallel with the current i1 to the power supply, and its value is determined by the resistor R6 and the shunt resistor R5. In the embodiment, the resistance R6 is set to 10
0Ω2W.

The current i4 is provided for adjusting the average output of the microwave oven, is a current that flows when the contact TC2 built in the timer that opens and closes periodically closes, and passes through the resistor R15, mainly through the transistor TR1. Base current. With the opening and closing of the timer contact TC2, the transistor TR1 is also turned on / off. Here, by the capacitor C12 connected between the base and the emitter of the transistor TR1, when the timer contact TC2 is turned on, the ON timing of the transistor TR1 by the CR charging time constant is set to 1
There is a delay of about 5 msec.

The current i3 is a current flowing through the relay coil of the DC relay RD1. The timer contact TC2 is closed when the timer contact TC2 is closed and the power is turned on by the timed contact TC1 of the timer, or when the timer contact TC2 is energized. After about 15 msec from the time when the transistor TR is closed, the transistor TR
The flow starts when 1 is turned on. However, even if the transistor TR1 is turned on, when the thyristor SR1 is on, the circuit voltage is low due to the resistor R6, and a current sufficient to drive the DC relay RD1 does not flow.

Since the circuit current supplied from the diode block DB1 is a pulsating current waveform subjected to full-wave rectification, the voltage waveform appearing at both ends of the shunt resistor R5 is also a pulsating current periodically showing a voltage of 0V. The thyristor SR1 is turned on by a gate current generated at each voltage cycle starting from 0 V, and is turned off at the end of each voltage cycle. Also, due to the switching characteristics of the thyristor, even if there is no gate current during one voltage cycle once turned on, the voltage cycle ends and the thyristor does not turn off until the voltage between the anode and cathode becomes 0V. . Therefore, at the end of the voltage cycle in which the transistor TR1 is turned on, the thyristor SR1 is turned off.
Keeps on state by the charging voltage of the capacitor C12, and after the next voltage cycle, the thyristor SR1 remains off and the driving of the DC relay RD1 is started.

FIG. 6 shows the opening / closing timing of the timer contact TC1 of the timer and the output adjustment contact TC2 built in the timer. Set the output of the microwave to [HIGH] (100
%), The TC2 continues to be in the ON state, but as an example, if [MID-HIGH] (70%), the opening / closing control is such that one cycle is 30 seconds, of which 22 seconds are on and 8 seconds are off. . [DEF] (10%) gives 30
Of 5 seconds, ON for 5 seconds and OFF for 25 seconds are repeated.

FIG. 7 is a voltage and current waveform diagram for explaining the operation of the circuit of relay unit RU2 shown in FIG. This shows a situation of 20 msec from when the timer contact TC1 of the timer is turned on to when the relay contact of the DC relay RD1 is closed. It is assumed that the timer contact TC2 is closed.

(A) shows a power supply voltage waveform av applied to the high-voltage transformer HT1, and the same voltage waveform is applied to the fan motor MT1. Current waveform a of fan motor MT1 and turntable motor MT2 connected in parallel
i is substantially described as the operating current of the fan motor MT1 due to the difference in power consumption between MT1 and MT2. The fan motor MT1 is a shaded induction motor, and the power phase cos θ during operation is about 50%, so that the current phase is delayed about 60 ° from the voltage phase. In a 50 Hz AC power supply, one cycle of the power supply is 20 msec, and a delay of 60 ° in phase angle corresponds to a delay of about 3.3 msec.

(C) shows the voltage across the capacitor C12 connected to the base of the transistor TR1 in FIG.
When the power is turned on, the capacitor C12 passes through the resistor R15.
Is charged, the voltage rises, and the transistor TR1
Turns on after a few milliseconds. When the transistor TR1 is turned on, the power supply voltage (e) increases, the charging voltage of the capacitor C12 also increases, and the on state of the transistor is stably maintained.

(B) shows the voltage across the resistor R6 in FIG. When the transistor TR1 is off, a current flows to the gate of the thyristor SR1 via the relay coil of the DC relay RD1 and the resistor R10, and the thyristor SR1 is ignited for each period of the voltage generated across the shunt resistor R5. Turn on. The current i1 and the current i2 flow, and the power supply voltage (e) has an effective value of about 9.5 V and a peak value of about 13.5.
Vp. The current value flowing through the relay coil of the DC relay RD1 is as small as about the gate current of the thyristor SR1, and the voltage applied to the collector of the transistor TR1 (b)
Is also substantially equal to the power supply voltage.

On the other hand, when the transistor TR1 is turned on, the gate current of the thyristor SR1 stops flowing.
The resistance of the relay coil of the relay RD1 is added in parallel, and the power supply voltage (e) and the voltage applied to the resistor R6 further decrease. Once the pulsating voltage cycle becomes 0 V, thyristor S
R1 is turned off, and at the time of the next rising of the pulsating voltage cycle, the transistor TR1 keeps on due to the charge of the capacitor C12. Therefore, the collector voltage (d) of the transistor TR1 is sufficiently low, and the thyristor SR1 is turned on. Cannot be fired. Therefore, a current that satisfies the operation specifications of the DC relay RD1 flows, and the DC relay RD1 closes the relay contact at a predetermined timing. Since the operation time of the DC relay RD1 employed in the embodiment is a specification of about 8 msec in DC step response, the capacitor C11 is connected in parallel to the relay coil of the DC relay RD1 to delay the operation time by about 3.5 msec. As shown in (f), about 11.5 msec (8 + 3.
5) The relay contact of the DC relay RD1 is connected with a delay. It is further delayed by 3.3 msec from the zero crossing point of the power supply voltage phase of the high-voltage transformer HT1, and the total
Due to the delay of 4.8 msec, the timing at which the contact of the DC relay RD1 is turned on matches the maximum value of the voltage phase of the high-voltage transformer HT1.

In the initial stage of turning on the power to the motor, the impedance of the motor coil changes due to the inertia force of the rotor rotation, and the current value and the phase angle delay are unstable. msec delayed.

FIG. 8 shows a case where the zero-cross timing of the voltage phase angle is 0 ° in a 50 Hz power supply supplied to the high-voltage transformer HT1, and the angle is used as a parameter.
FIG. 11 is a diagram in which the observed peak values of the inrush current waveform are plotted, and the circuit shown in FIG. 5 or FIG. 10 controls the operation timing of the relay contact of the DC relay RD1 by controlling the phase angle, thereby suppressing the inrush current. Show. The two curves are
The voltage phase angle at which the high-voltage transformer HT1 is operated immediately before the inrush current observation and the power is turned off is also used as an observation parameter, and is an inrush current observation value obtained under a phase condition having a large influence. This indicates that the phase angle at which the inrush current becomes minimum changes by about 30 ° depending on the polarity of the residual magnetic field of the core of the high-voltage transformer HT1 and the polarity of the voltage phase when the power is turned on. When the conventional microwave oven rush current suppression effect is obtained by the phase angle control only when the power is turned on, if about 40 A is used as a guide in the drawing,
The phase angle ranges from about 65 ° to 103 °. That is, if the relay contact of the DC relay RD1 is closed within a range of about 4.7 msec ± 1 msec from the power supply voltage zero crossing, an inrush current suppression effect can be obtained practically.

According to the above configuration, when the power is turned on, it is possible to start the operation controlled based on the voltage phase angle of the power supply, so that the surge resistance for suppressing the rush current is unnecessary.
Therefore, the combination of the specifications of the monitor fuse and the monitor resistor can be composed of a small-capacity current fuse to be supplied to the control circuit and a monitor resistor with a value required to blow within the rated value of this fuse. Small parts suitable for the vehicle can be adopted. Also, in the present invention, the monitor fuse rated fusing current value is sufficiently small, and when the fan motor is short-circuited, the monitor fuse is blown.

Further, in the present embodiment, the timed contact of the conventional timer motor is provided at a constant cycle (for example, 30
(Cycle of about second) A timer motor with an intermittent contact added and capable of changing the duty ratio of the operation of the high-voltage transformer HT1 is employed. By connecting the intermittent contact of this timer motor to a phase control circuit, an output adjustment function was added to the microwave oven.

Since the circuit current flowing through the intermittent contact of the timer motor is a low voltage minute current that supplies the base current of the driving transistor of the DC relay RD1, the intermittent contact inserted into the main circuit of the conventional microwave oven is used. Smaller contacts than contacts can be used. For this reason, the reliability of the timer contact is improved, and an inexpensive contact component can be used.

FIG. 9 shows a circuit of a microwave oven for Northern Europe according to a third embodiment of the present invention. The present embodiment is different from the circuit shown in FIG. 4 in that the voltage obtained by the variable resistor VR1 connected to the electronic circuit of the relay unit RU3 does not use the timer built-in contact for the microwave output variable function. On / off duty control of the DC relay is performed at a predetermined cycle according to the level. For this purpose, a relay control circuit is provided with a long-period triangular wave generation circuit and a voltage comparison circuit.

When the microwave oven door is closed and the timer knob is wound up, the timer contact TC1 is closed, and power is supplied to the fan motor MT1 and the turntable motor MT2 connected in series with the relay unit RU3 and connected in parallel. By the circuit of the relay unit RU3 shown in FIG. 10, the contact of the DC relay RD1 closes at a power supply voltage phase angle of about 90 °, the rush current is suppressed, and power is supplied to the high-voltage transformer HT1. Then, the high voltage circuit drives the magnetron MG1, and the heating operation is started. In the output adjustment, the DC relay RD1 is intermittently controlled by adjusting the angle of the output adjustment volume VR1, and the average output is changed. When the door is opened during operation, the door switch SW1 opens,
The power of the relay unit RU3 is also turned off, the relay contact of the DC relay RD1 is opened, and the state of the circuit is reset. When the door is closed again, the operation starts from the initial state.

FIG. 10 shows a circuit of the relay unit RU3 of the present embodiment. In this circuit, the power supply configuration and the drive timing of the DC relay RD1 are almost the same as those of the voltage phase angle control circuit shown in FIG. 5, but the output is controlled by a phase latch circuit that determines the drive start timing of the DC relay RD1. A voltage comparing circuit and a long-period triangular wave generating circuit for generating the intermittent timing of the DC relay RD1 are added. The circuit current is mainly divided into four currents as in FIG. 5, and drives the DC relay RD1.

The current i11 is a current flowing through the shunt resistor R5a connected in parallel so that the drive current i31 of the DC relay RD1 becomes a predetermined rated operating current of the DC relay RD1. When the transistor TR1 is on and the DC relay RD1 is operating, the thyristor SR1 is turned off because no gate voltage is applied, and the current i21 does not flow. Therefore, the current of about 130 mA of the fan motor MT1 and the turntable motor MT2 is divided into the current i11 and the current i31 and the current i41 flowing through the electronic circuit after the resistor R7. The circuit voltage is 5V in this circuit
And the circuit current i41 is about 20 mA.
A shunt resistor R5a was set to 540Ω3W in consideration of a voltage reduction characteristic by adopting a DC relay of coil specification 18V40mA.

When the transistor TR1 is off, the current i21 is equal to the resistance of the relay coil of the DC relay RD1 and the current R21.
The current flows through the gate of the thyristor SR1 via the gate line 10, and flows between the anode and the cathode of the thyristor SR1 when the thyristor SR1 is turned on. When the DC relay RD1 is turned off, suppress the fluctuation of the circuit impedance,
In order to perform load compensation, as an example, the resistor R6a
A value of 470Ω3W corresponding to the coil resistance of the C relay RD1 was employed.

The current i31 is a current flowing through the relay coil of the DC relay RD1, and starts flowing when the transistor TR1 is turned on. For this reason, a circuit configuration is provided in which a voltage phase latch is performed by a combination of the voltage between both ends of the resistor R6a and the intermittent signal from the comparator IC2 so that the zero-crossing initial of the pulsating circuit voltage always becomes the ON timing of the transistor TR1 for the comparator IC1. Has become.

The resistor R7 and the Zener diode ZD
2 and the capacitor C10 constitute a circuit power supply 5V for generating an intermittent signal for output adjustment.

FIG. 11 is a functional block diagram relating to the circuit of the relay unit RU3 of FIG. The circuit power supply is configured by supplying a pulsating flow obtained by rectifying the external motor current to the shunt resistor R5a and other circuits. D with load compensation
The C relay drive circuit has already been described with reference to FIG.

The phase latch circuit synchronizes the rising timing of the next voltage comparison circuit output from L to H level with the initial timing of the circuit pulsating voltage cycle, and turns on the driving transistor TR1 of the DC relay RD1. And is configured by a comparator IC1.

The voltage comparison circuit compares the output voltage of the long-period triangular wave generation circuit with the voltage level set by the variable resistor VR1 connected to the output adjustment knob installed on the control panel of the microwave oven.
, And the output is input to the comparator IC1 as H / L according to the magnitude of the level.

The long-period triangular wave generation circuit uses a programmable unijunction transistor PUT and a resistor R
A repetitive timer circuit is formed by discharging the voltage across C30 according to the charging time constant of the capacitor 30 and the capacitor C30 with a divided voltage by the resistors R32 and R33. In the embodiment, in order to perform the same output control as that of the intermittent contact having the built-in motor timer shown in FIG. 6, the circuit constant is set so that one cycle is about 30 seconds.

FIG. 12 shows an output state by the voltage comparison circuit and the long-period triangular wave generation circuit in FIG. FIG.
2 (a) shows an input waveform of the voltage comparator IC2. FIGS. 12B and 12C show output waveforms of the voltage comparator IC2 with respect to the set voltage level of the variable resistor VR1. At 100% level, the output of IC2 is always H, and at 70% level, the output of IC2 is about 2
When the duty ratio is 2 seconds and the duty ratio is 73% or 10%, the output of IC2 is set so that the H state is about 5 seconds and the duty ratio is 17%. It should be noted that the duty time in the H state is approximately 2 at the beginning of operation of the magnetron MG1.
There is a loss time due to the filament heat-up of about seconds, and as the actual heating operation time, the above 73% is 66%.
% And 17% correspond to a heating operation time of 10%.

FIG. 13 shows waveforms for explaining the operation of the phase latch circuit of FIG. A pulsating voltage generated across the resistor R6a by a current flowing when the thyristor SR1 is in an on state is input to the input (A) of the comparator IC1 by a resistor R11 and diodes D6 and D7, and resistors R20 and R21. A signal whose waveform has been shaped so as to be in a range is input. Comparator IC1
FIG. 12B shows the input (B) of FIG.
A signal having a waveform with a duty ratio set as shown in (c) is input.

When the input signal (B) of IC1 is L, the voltage level is almost 0V, and the input signal (A) is at least 1V to 5V.
Since the signal is in the range up to V, [A> B] is always satisfied, and the output (C) of IC1 is L
Becomes When the input signal (B) of IC1 rises from L to H, the H level is set to about 3 V by resistors R22 and R23.
become. At this time, the input signal (A) is in the middle of the pulsating voltage cycle, and based on the relationship between the voltage levels of 5 V and 3 V, [A>
B], the output (C) of the IC 1 does not immediately become H, but keeps L. At the moment when the pulsating voltage cycle of the input signal (A) ends and the voltage level changes from 5 V to 1 V, the relationship between the input voltage levels becomes [A <B]. Become. Therefore, the DC relay driving transistor TR1 is turned on. Transistor T
When R1 is turned on, the gate current of the thyristor SR1 is turned off immediately before the pulsating voltage is applied to SR1, so that no current flows through the resistor R6a, and the input signal (A) of the comparator IC1 has an L level. Hold 1V. Therefore, the voltage between both ends of the relay coil of the DC relay RD1 is applied in synchronization with the rise of the pulsating voltage cycle as shown in a waveform (RD). However, since the capacitor C11 is connected in parallel to the relay coil, the timing at which the relay contact closes is delayed, and closes after about 11.5 msec. A delay of about 14.8 msec is added to the phase of the power supply voltage applied to the motor by adding a delay of about 3.3 msec to the current phase. The power supply voltage has a maximum value, and the power is supplied to the high-voltage transformer HT1, thereby suppressing an inrush current. it can.

As described above, by incorporating a circuit capable of variably controlling the ON / OFF duty ratio at a predetermined cycle in the drive control circuit of the DC relay RD1, the high-voltage transformer HT1 is intermittently connected with one electronic circuit board. The function of controlling and adjusting the average output can be realized. For this reason, when designing for mass production, it is more advantageous to incorporate functions into the electronic circuit board in terms of member costs and assembly costs than to mechanically / additionally add additional contacts to the motor timer.

FIG. 14 shows a circuit of a microwave oven for Northern Europe according to another embodiment. The microwave oven according to the present embodiment
In the circuit of the microwave oven according to the third embodiment, the timer contact inserted in the main power supply circuit is inserted into the power supply of a circuit including an oven lamp, a motor, a relay unit, and the like. The oven lamp OL1 and the timer motor TM3 are all connected in parallel to the circuit of the fan motor MT1 and the turntable motor MT2 connected in series with the relay unit RU3 and connected in parallel.
C1 opens and closes. Since the timer contact TC1 can be configured with a current switching capacity of about 300 mA without switching the current of the main power supply circuit, the contact switching of a timer motor equipped with a contact that switches the main current of 10 A to 15 A conventionally is performed. In the mechanism, the contact operating force can be reduced. When the contact operating force is reduced, the operating force of the clutch mechanism between the timer output shaft and the internal mechanism can be reduced.

In the standby state of the microwave oven, the timer contact T
Since C1 is open and the power of the DC relay RD1 is off, the magnetron MG1 does not malfunction due to malfunction of the electronic circuit.

With the above configuration, the motor timer contact T
Remove C1 from the main power circuit of magnetron MG1,
Insert auxiliary parts such as oven lamp, motor, relay unit, etc. into the power supply of the integrated circuit. This allows
The current flowing through the motor timer contact TC1 is 220V5
With a 0 Hz power supply, it is about 360 mA at the maximum.
In a conventional circuit, the steady operating current flowing through the main power circuit is
From 6A to 10A, the inrush current at the start of operation is reduced from the peak value of 30A to about 50A even if the suppression control is performed by the voltage phase angle, and the contact condition is very severe. In this circuit, since the current capacity of the motor timer contact can be limited to a low value, the cost of the motor timer contact TC1 can be reduced in terms of members, and an inexpensive control circuit and a motor timer can be supplied in a mass production design. .

FIG. 15 shows a circuit of a microwave oven for Northern Europe according to a fourth embodiment of the present invention. In contrast to the third embodiment shown in FIG. 9, a triac, which is a semiconductor switching element, is used instead of a DC relay as a main power switching device for the high voltage transformer HT1. The operation time of the DC relay requires about 8 msec, but is extremely short in the case of a semiconductor switching element such as a triac. In the case of the Nordic home power supply of 220 V and 50 Hz, if the power is turned on at a timing 4.5 msec to 5 msec later than the time of the power supply voltage zero crossing, the power is turned on at a voltage phase angle of approximately 90 °, and the power is turned on at the maximum voltage value. Inrush current can be suppressed. In this embodiment, the control circuit power is obtained from the current of the air-cooling induction motor, and the phase angle shift of the voltage / current of the induction motor corresponds to a delay of about 60 °. The timing is delayed by about 3.3 msec when compared with the voltage phase of the microwave power supply. Furthermore, it is easy to detect the circuit voltage zero crossing and to delay the timing of firing the triac gate by about 1.2 msec to 1.7 msec, and the delay time precision is relatively high.

The timing of the ignition signal to the gate of the triac TA1 is performed in the same manner as the timing of closing the relay contact in the circuit of FIG. 9, and the rush current is controlled by controlling the power supply voltage phase angle to about 90 °. Restrained. Inside the circuit power supply of the relay unit RU4, the pulsating voltage cycle obtained by the phase-lag current flowing through the fan motor MT1 and the turntable motor MT2 is
Utilizing a voltage rising timing delayed by about 3.3 msec and a time delay of about 1.5 msec obtained from the rising voltage gradient, a timing of ignition at a power supply voltage phase angle of 90 ° by a total phase delay of about 4.8 msec. Have gained. The gate firing of the triac TA1 uses a phototriac coupler P instead of the relay coil used in the circuit of FIG.
The gate of the triac TA1 for interrupting the main power supply is fired using C1.

FIG. 16 shows a circuit of the relay unit RU4 shown in FIG. In this circuit, the relay drive circuit portion in the relay unit circuit RU3 shown in FIGS. 10 and 11 is connected to the input side L of the phototriac coupler PC1.
This is a circuit replaced by ED. The circuit current from the power supply portion is similar to the circuit of FIG.
Of the divided current. Since the value required for the current i32 is the drive current for the input LED of the phototriac coupler PC1, it may be about 10 mA. Since the power supply circuit voltage only needs to be able to drive this LED, as an example, the shunt resistor R5b is set to 100Ω2W, and the divided voltage of the relay unit RU4 is set to about 10V. Therefore, when the transistor TR1 is off, the current i22 flowing through the thyristor SR1 is set to about 10 mA, the resistance R6b is set to about 1 kΩ, and the current i42 is set to 20 mA at 5V as in FIG. R7 is adjusted.

By the operation of the phase latch circuit, the transistor TR1 is turned on when the circuit power supply pulsating voltage rises, but the input LE of the phototriac coupler PC1 is turned on.
The timing at which D gives a signal to the output triac TA1 is delayed until the pulsating voltage exceeds the voltage of the zener diode ZD1. In the case of a pulsating voltage having an effective value of 10 V, a delay time of about 1.5 msec can be obtained by inserting a Zener diode ZD1 having a Zener voltage of about 7 V, which is about half the peak value. The transistor TR1 is turned on, and the input LED of the phototriac coupler PC1 is constantly turned on by the electric charge charged in the capacitor C11 in one cycle of the pulsating voltage, so that the main power switching triac TA1 is fired.

As described above, by employing the triac which is a semiconductor switching element, the characteristic that the power supply of the control circuit utilizes the delay current which is the motor inductive load is effectively utilized, and the accuracy is improved. It becomes possible to control the injection of the phase angle of a high power supply voltage, and it is possible to effectively suppress the inrush current.

FIG. 17 is a circuit diagram of a microwave oven for Nordic countries according to the third embodiment shown in FIG. 9, which is different from the relay unit RU4 shown in FIG. And a circuit of a relay unit RU5 in which a long-period triangular wave generation circuit is configured using a microchip integrated circuit.

The currents i13 to i43 are the same as in the circuit of FIG. However, in the power supply circuit of the present circuit, a smoothing capacitor C12 is connected in parallel with the shunt resistor R5c to smooth the pulsating voltage. Also,
The current of the resistor R6c for load fluctuation compensation is switched by the transistor TR2. The microchip integrated circuit LSI includes input / output I / O terminals such as a clock oscillation circuit, a reset circuit, an output adjustment level setting input circuit, a power supply synchronizing signal input circuit, and a drive output circuit of the transistor TR1. (RAM / ROM, counter) is a one-chip microcomputer.

By closing the microwave oven door and turning the timer knob, the power is turned on to the relay unit RU5, the fan motor MT1, and the turntable motor MT2. When the power supply voltage reaches the Zener voltage of the Zener diode ZD3, the transistor TR3 outputs LS
A voltage is applied to the reset terminal of I, and the LSI enters an initial setting state. Thereafter, based on the divided voltage information of the power supply voltage obtained from the output adjusting variable resistor VR1, the on-time of the on / off duty ratio with one cycle being about 30 seconds is calculated. When the transistor TR1 is turned on based on the calculated on / off duty, the ignition timing is determined by counting the time with reference to the clock cycle of the LSI so that the timing is optimal for turning on the main power. It is demanded by.

The time from when the timer contact is closed to when the DC relay contact is closed is determined by the rise time of the circuit power and
The time required for the initial reset of the LSI is set to about 15 msec, and after detecting the first rise of the power supply synchronization signal, the transistor TR1 is turned on with a delay of about 3.5 msec, and the contact of the DC relay RD1 is set to about 8 msec. If closed later, it would take about 27 msec.

When the transistor TR1 is turned on,
The transistor TR2 is turned off, the load of the power supply circuit does not change, and the DC relay RD1 is controlled.

As described above, by adopting the one-chip microcomputer LSI for the configuration of the electronic control circuit, the power supply for controlling the rush current and controlling the operation output by controlling the phase angle of the power supply voltage at the time of turning on the power of the microwave oven. The degree of freedom and accuracy of timing determination in ON / OFF duty control and the like are improved, and the time deviation between circuit units is small as compared with the case of using discrete components, which is effective in mass production.

FIG. 18 shows a circuit of a microwave oven for Northern Europe according to a fifth embodiment of the present invention. In the present embodiment, the connection positions of the oven lamp OL1, the fan motor MT1, and the turntable motor MT2 are replaced with the circuit of the third embodiment shown in FIG. Therefore, the circuit power supply of the relay unit RU6 is characterized by being supplied by a divided voltage of the commercial power supply voltage with the oven lamp OL1. The specification of the oven lamp OL1 employs 220 V and 25 W as an example, and the rated current is about 114 mA. For this reason, by connecting the relay unit RU6 in series, the current value slightly decreases to about 105 mA,
It can be a sufficient power supply to drive the relay coil in U6.

The voltage and current phases of the power supply are the same, and the timing for suppressing the current surge when the power supply to the high-voltage transformer HT1 is turned on is a timing delayed by 90 ° from the time of the voltage zero crossing, as shown in FIG. As shown in the above, the delay may be about 4.8 msec from the voltage zero cross.

FIG. 19 shows a circuit of a relay unit RU6 employed in the circuit of the microwave oven according to the present embodiment. The relay unit RU6 of the circuit of FIG. 18 differs from the circuit of FIG. 10 in the insertion position of the capacitor C11, and is connected between the circuit after the diode D5 and the 0V potential. That is, before the DC relay RD1 is closed by the transistor TR1, the DC relay RD1 is inserted for the purpose of smoothing the power supply for driving the DC relay RD1. Further, the DC relay RD1 is
Operating time of relay contact is 4.8msec at rated voltage
Since it is required to be ± 1 msec, the coil specification is 9 as an example.
It is necessary to adopt a coil of V80 mA and reduce the coil resistance value. For this reason, the shunt condition of the circuit current changes, and the current i
From 14, the resistance value that determines the value of the current i44 is also changed. As an example, the value of the shunt resistor R5d is 430Ω1W, and the value of the resistor R6d for load variation compensation is 120Ω2W as a value approximating the resistance value of the relay coil. The other circuit configuration and the operation of each unit are the same as those of the circuit of FIG.

With the above configuration, the power supply of the control circuit is
When the DC relay is configured to be connected in series with the oven lamp OL1 and there is no phase shift of voltage / current and a DC relay having an operation time of 4.5 msec to 5.5 msec is adopted in a 50 Hz power supply, the DC relay RD starts from the time of voltage zero crossing.
An optimum power-on timing is obtained by a delay of one operation time. For this reason, an electrolytic capacitor for delaying the operation of the DC relay RD1 can be omitted, and the fluctuation factor of the power-on timing can be reduced.

The replacement of the fan motor with the oven lamp can be applied to the circuits of other embodiments. However, in the case of an oven lamp, there is no voltage / current phase shift, and it is necessary to adjust the operation delay time of the DC relay or the semiconductor switching element.

Furthermore, relatively large components such as an AC type surge suppression relay, a surge resistor, a monitor resistor, and an intermittent timer contact for output adjustment used in the conventional circuit shown in FIG. The parts that are independently fixed with screws inside the set are mounted on a single printed circuit board as a transformer-less power supply circuit configuration and stored in a relay unit, and mass production is facilitated by using general-purpose parts be able to. Furthermore, by integrating the circuit board parts of the noise filter unit shown in the conventional circuit into the relay unit,
The production time in the microwave oven manufacturing process can be reduced.

[0093]

As described above, the microwave oven of the present invention can be used to replace a surge suppression relay, which has been employed for suppressing a rush current into a high-voltage transformer, with a small general-purpose DC relay or the like. It can be implemented with a power supply without power. Further, the surge resistance and the monitor resistance of the relatively large size of the square cement resistance conventionally used can be replaced with a small axial type resistance of a general-purpose product mounted on a printed circuit board.

Further, in the manufacture of a microwave oven, it is not necessary to separately arrange several kinds of special parts in the set. One printed circuit board is attached to the set, and a bundle of several connectors is formed. Completion of wiring by connection reduces cost due to improvement in production efficiency and reduces erroneous wiring and other operation errors.

Further, in designing a bundle of lead wires for internal wiring of a microwave oven, when a plurality of components are put together on a single board, a connection portion between components arranged inside the board can be omitted, which is extremely simplified. Lead wire bundle design can be realized, and the cost can be reduced.

As described above, it is possible to reduce the cost of component materials, the cost of the production process, and supply a more inexpensive microwave oven to the market.

Further, by dividing the voltage by using the display means indicating that the magnetron is operating instead of the motor, the power can be turned on at a stable timing without a voltage / current phase shift.

Further, since the switching contact is closed in synchronization with the voltage phase of the AC power supply, an inrush current when the power is turned on can be suppressed, and a surge resistor is not required.

Further, by controlling the on / off duty of the power supply, the microwave output can be made variable, and a product with higher added value can be provided.

Further, by making the intermittent control for output adjustment an electronic circuit, a general-purpose type electronic circuit component can be mounted on one printed circuit board. By consolidating general-purpose small electronic components on one printed circuit board, mass production becomes easy and cost reduction becomes possible.

Further, by using a DC relay as the opening / closing means, the operation time of the relay contact can be stabilized and a low-cost component can be used.

Further, by using a triac as the switching means, the power can be turned on with high time accuracy based on the phase angle of the power supply voltage, and the rush current can be effectively suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit of a microwave oven according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an appearance of a microwave oven for Scandinavia according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating an appearance of a microwave oven for Scandinavia according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a circuit of a microwave oven according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating a circuit of a relay unit according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating opening / closing timings of a timed contact and an output adjustment contact of a timer.

FIG. 7 is a diagram showing current and voltage waveforms for explaining the operation of the circuit of the relay unit according to the second embodiment of the present invention.

FIG. 8 is a diagram plotting a peak value of an inrush current at the time of power-on using a power-supply voltage phase angle as a parameter.

FIG. 9 is a diagram showing a circuit of a microwave oven for Northern Europe according to a third embodiment of the present invention.

FIG. 10 is a diagram illustrating a circuit of a relay unit according to a third embodiment of the present invention.

FIG. 11 is a functional block diagram of a circuit of a relay unit according to a third embodiment of the present invention.

FIG. 12 is a diagram illustrating a state of output by a voltage comparison circuit and a long-period triangular wave generation circuit.

FIG. 13 is a diagram showing waveforms for explaining the operation of the phase latch circuit.

FIG. 14 is a diagram showing a circuit of a microwave oven for Northern Europe according to an embodiment of the present invention.

FIG. 15 is a diagram showing a circuit of a microwave oven for Northern Europe according to a fourth embodiment of the present invention.

FIG. 16 is a diagram illustrating a circuit of a relay unit according to a fourth embodiment of the present invention.

FIG. 17 is a diagram showing a circuit of a relay unit using a microchip integrated circuit according to an embodiment of the present invention.

FIG. 18 is a diagram showing a circuit of a microwave oven for Northern Europe according to a fifth embodiment of the present invention.

FIG. 19 is a diagram illustrating a circuit of a relay unit according to a fifth embodiment of the present invention.

FIG. 20 is a diagram showing a circuit of a conventional microwave oven employing a motor timer.

FIG. 21 is a diagram showing a circuit of a conventional microwave oven in which a surge resistor and a monitor resistor are combined into one.

FIG. 22 is a diagram showing a circuit of a conventional microwave oven using a DC surge relay using a low-voltage transformer power supply.

FIG. 23 is a diagram showing a circuit of a conventional microwave oven using a DC surge relay using a power supply utilizing a bleeder resistor.

[Explanation of symbols]

 RU1-6 Relay unit DB1 Diode block RD1 DC relay MT1 Fan motor MT2 Turntable motor OL1 Oven lamp TM1-3 Timer motor HT1 High voltage transformer MG1 Magnetron NF1 Noise filter TA1 Triac

Claims (3)

[Claims] 1. A microwave oven provided with a magnetron, a fan motor driven by an AC power supply, a power supply circuit of the magnetron driven by the AC power supply, an open / close contact for supplying power to the power supply circuit, Switching means for opening and closing contacts, a rectifying element connected in series with the fan motor, and a dc current flowing through a series circuit of the switching means and the fan motor by the rectifying element. And microwave oven. 2. A microwave oven provided with a magnetron, a turntable motor driven by an AC power supply, a power supply circuit of the magnetron driven by the AC power supply, an open / close contact for supplying power to the power supply circuit, Opening and closing means for opening and closing the opening and closing contacts, connecting a rectifying element in series with the turntable motor,
A microwave oven having a circuit configuration in which a DC current is supplied to a series circuit of the opening / closing means and the turntable motor by the rectifying element. 3. A microwave oven equipped with a magnetron, an oven lamp driven by an AC power supply to indicate that the magnetron is operating, a power supply circuit of the magnetron driven by the AC power supply, and power supply to the power supply circuit. A circuit for connecting a rectifying element in series with the oven lamp, and supplying a direct current to a series circuit of the opening / closing means and the oven lamp by the rectifying element. A microwave oven having a configuration.