JPH0569894U - microwave - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce the inrush current that flows when electricity is applied to a pair of high-frequency generators connected in parallel to a commercial power supply, and to simplify the inrush current prevention circuit. [Structure] When driving the pair of high-frequency generators 3 and 8,
According to the sequence incorporated in the control circuit 11, first, the first switch 5 is turned on and the first resistor 4
After pre-exciting the high-voltage transformer 2, the second switch 6
Is closed and a regular voltage is applied to the first high voltage transformer 2. At the same time, commercial power is supplied to the second high-voltage transformer 7 via the second resistor 9 to perform pre-excitation, and then the third switch 10 is closed to supply a regular voltage to the high-voltage transformer 7 to operate it.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to prevention of inrush current in a microwave oven having a plurality of high-frequency generators in order to increase the high-frequency heating output.

[0002]

[Prior Art]

 In order to suppress the inrush current that flows to the primary side of the high-voltage transformer that supplies a high voltage to the high-frequency generator, commercial power is applied to the high-voltage transformer through a resistor that limits the inrush current, and the high-voltage transformer is pre-excited. Japanese Patent Laid-Open No. 2-257589 discloses a configuration in which a resistor is short-circuited and commercial power is supplied to a high-voltage transformer without going through the resistor.

On the other hand, in order to shorten the cooking time, a high-power microwave oven has been developed in which two high-frequency generators having the above-mentioned configuration are connected in parallel. The inrush current of this high-power microwave oven was large, and the breaker of the indoor wiring sometimes broke.

[0004]

[Problems to be solved by the device]

 The inrush current that flows when multiple high-frequency generators connected in parallel to the commercial power source are energized is reduced to prevent breaks in the indoor wiring. Furthermore, the inrush current prevention circuit will be simplified to reduce costs.

[0005]

[Means for Solving the Problems]

 The present invention relates to a first high-voltage transformer for driving a first high-frequency generator by boosting a power supply voltage, a second high-voltage transformer for driving a second high-frequency generator, and an inrush connected to the first high-voltage transformer. A series circuit of a first resistor and a first switch that limits the current; and a second switch that is connected in parallel to the series circuit of the first resistor and the first switch and that controls the power supply to the first high-voltage transformer. , Connected in parallel with the first high-voltage transformer and connected in parallel with a series circuit of a second resistor and a second high-voltage transformer for limiting inrush current, and a series circuit of the second switch and the second resistor, The third switch, which controls the power supply to the second high-voltage transformer, and the first switch are turned on, the second switch is turned on for a predetermined time, and the second switch is turned on. 3 Switch on And a control circuit which work.

[0006]

[Action]

 Since the second switch for controlling the power supply to the first high-voltage transformer is also used as the switch for pre-exciting the second high-voltage transformer and the pair of high-frequency generators is sequentially driven, it is compared to the case where they are simultaneously driven. However, the peak value of the inrush current can be reduced.

[0007]

【Example】

 FIG. 1 shows a circuit configuration of an embodiment of the present invention. 1 is a commercial power source, 2 is a first high voltage transformer for boosting a commercial power source voltage to drive a first high frequency generator 3, and 4 is a first high voltage transformer 2. A first resistor for limiting the inrush current generated during the energization of the first resistor 5, a first switch for controlling the energization of the first high-voltage transformer 2 via the first resistor 4, and a first resistor 4 and a first switch 5. Is a second switch that is connected in parallel to the series circuit of and controls the power supply to the first high-voltage transformer 2.

Reference numeral 7 is a second high-voltage transformer that boosts the commercial power supply voltage to drive the second high-frequency generator 8. Reference numeral 9 is a second resistor that limits the inrush current generated when the second high-voltage transformer 7 is energized. A series circuit of the second resistor 9 and the second high voltage transformer 7 is connected in parallel with the first high voltage transformer 2. A third switch 10 is connected in parallel to the series circuit of the second switch 6 and the second resistor 9 and controls the power supply to the second high-voltage transformer 7, and 11 is for opening and closing the first to third switches. It is a control circuit for controlling.

In the above configuration, when heating and cooking are started, the first switch 5 is first closed according to the sequence incorporated in the control circuit 11, and commercial power is supplied via the first resistor 4 to the first high-voltage transformer 2 To perform pre-excitation. At this time, the second high-voltage transformer 7 is also pre-excited via the first resistor 4 and the second resistor 9, but the pre-excitation is not sufficiently performed because the energizing current to the second high-voltage transformer 7 is small. Then, after about 30 to 70 milliseconds, the second switch 6 is closed to apply a regular voltage to the first high voltage transformer 2, and at the same time, the commercial power is supplied to the second high voltage transformer 2 via the second resistor 9. 7 and perform sufficient pre-excitation. Next, after about 30 to 70 milliseconds, the third switch 10 is closed to apply a regular voltage to the second high voltage transformer 8.

Since the first resistor 4 and the second resistor 9 are short-circuited by the second switch 6 or the third switch 10 after being energized for a short time (tens of milliseconds), the power consumption is relatively small. The one used for is used.

[0011]

[Effect of the device]

 According to the present invention, the second switch for controlling the power supply to the first high-voltage transformer is also used as the switch for pre-exciting the second high-voltage transformer, and the pair of high-frequency generators are sequentially driven. The number of switches for controlling the pre-excitation that suppresses the inrush current of the generator can be reduced and the cost can be reduced. Further, since the pair of high-frequency generators are sequentially driven, the peak value of the inrush current can be reduced to about half that in the case of simultaneously driving, and the breaker of the indoor wiring due to the inrush current can be prevented.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

[Explanation of symbols]

 2 1st high voltage transformer 3 1st high frequency generator 4 1st resistance 5 1st switch 6 2nd switch 7 2nd high voltage transformer 8 2nd high frequency generator 9 2nd resistance 10 3rd switch 11 Control circuit

Claims (1)

[Scope of utility model registration request] 1. A first high voltage transformer for driving a first high frequency generator by boosting a power supply voltage, a second high voltage transformer for driving a second high frequency generator, and an inrush current connected to the first high voltage transformer. A series circuit of a first resistor and a first switch for limiting the voltage, a second switch connected in parallel to the series circuit of the first resistor and the first switch, and controlling the power supply to the first high-voltage transformer, The first high-voltage transformer is connected in parallel, and the second resistor for limiting the inrush current and the second high-voltage transformer are connected in parallel, and the second switch is connected in series to the second resistor. A third switch for controlling power supply to the high-voltage transformer and a third switch which is delayed by a predetermined time after the first switch is turned on to turn on the second switch, and is delayed by a predetermined time after the second switch is turned on by the third switch. Turn on A microwave oven that includes a control circuit that controls the microwave oven.