JP3032594B2 - microwave - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[Object of the Invention]

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave oven having a function of controlling the output of a magnetron at a constant level.

[0003]

2. Description of the Related Art As is well known, in a microwave oven,
A rectifier that rectifies AC power supplied from a commercial AC power supply, an inverter circuit that switches the output of the rectifier by a switching element and supplies the primary winding of the transformer, and rectifies the secondary output of the transformer. And a magnetron drive circuit for driving the magnetron.

In a microwave oven, since the output of the magnetron itself fluctuates due to the influence of the magnetron temperature and the like, the output of the magnetron is controlled to be constant. For this constant output control, there are provided anode current detection means for detecting the anode current of the magnetron, and constant output control means for controlling the inverter circuit so as to make the output of the magnetron constant according to the anode current detection result. ing. That is, the magnetron output is estimated by detecting the anode current, and the anode current is appropriately controlled by changing the on-time of the switching element of the inverter circuit in accordance with the anode current detection result, thereby keeping the magnetron output constant. To control.

[0005]

By the way, in the above-mentioned device, when the output of the magnetron is kept constant, the anode current increases as the power supply voltage increases, so that the anode current is controlled to decrease the anode current. in this case,
Control is performed so as to shorten the ON time of the switching element. Therefore, in this case, a large current does not flow through the inverter circuit. However, when the voltage of the power supply decreases, the anode current decreases. Therefore, in order to eliminate the decrease, the control is performed such that the ON time of the switching element is lengthened and the output of the magnetron is constant. As a result, a large amount of current flows through the inverter circuit, and there is a problem that the indoor power supply breaker operates beyond the maximum rating of 15 A, which is the maximum rating of an indoor 100 V outlet.

Accordingly, an object of the present invention is to provide a microwave oven capable of controlling the magnetron output to a constant level when the power supply voltage does not decrease, and preventing an excessive current from flowing through the inverter circuit when the power supply voltage decreases. To offer.

[Structure of the Invention]

[0008]

The microwave oven according to the present invention comprises:
An inverter circuit for rectifying an alternating current and switching the output by a switching element to supply the primary current to a primary winding of a transformer; a magnetron drive circuit for rectifying a secondary output of the transformer to drive a magnetron ;
Magnetron output detection means for detecting the output of the power supply , power supply voltage detection means for detecting the power supply voltage, voltage determination means for determining whether the power supply voltage detection result is equal to or higher than a reference voltage, and the power supply voltage detection result Is greater than or equal to the reference voltage , according to the detection result of the magnetron output detection means.
The inverter so that the output of the magnetron is constant
And a release means for controlling the circuit and releasing the constant output control for the magnetron when the power supply voltage detection result falls below the reference voltage. this
In this case, the magnetron output detecting means is
Consists of anode current detection means for detecting anode current
Good.

[0009]

According to the above means, in a normal state where the power supply voltage is not low, this is determined by the voltage determining means.
Then, the inverter circuit is controlled so as to keep the output of the magnetron constant according to the detection result of the magnetron output detection means. Therefore, constant control of the magnetron output is achieved. Further, when the power supply voltage becomes low, this is determined by the voltage determination means. Then, the release means releases the constant output control for the magnetron. Therefore, even if the power supply voltage decreases, the current flowing through the inverter circuit does not increase.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. The figure shows an electric circuit, and one terminal 1 of a power plug 1 connected to an indoor power outlet.
a is connected to one input side of a rectifier 4 composed of a diode bridge via a fuse 2 and a power switch 3, and the other terminal 1b of the power plug 1 is connected to the other input side of the rectifier 4. I have.

A choke coil 5 and a smoothing capacitor 6 are connected to the output side of the rectifier 4, and an inverter circuit 7 is connected between both terminals of the smoothing capacitor 6. That is, the inverter circuit 7 connects the primary winding 8a of the step-up transformer 8 and the transistor 9 as a switching element between both terminals of the smoothing capacitor 6, and connects the resonance capacitor 10 in parallel with the primary winding 8a. 9 and a flywheel diode 11 is connected in parallel.

A rectifier diode 13 for driving the magnetron 12 is connected to a secondary winding 8 b of the step-up transformer 8.
And a magnetron drive circuit 15 including a voltage doubler capacitor 14.

On the other hand, a primary winding 16a of a step-down transformer 16 is connected to the power supply lines 1c and 1d, and a secondary winding 16b for an electronic circuit power supply and a power supply voltage are connected to the secondary side of the transformer 16. A secondary winding 16c for detection is provided, and each of the windings 16b and 16c is connected to a control circuit 17 including a microcomputer.

The control circuit 17 comprises power supply voltage detecting means and voltage judging means by the secondary winding 16c and the internal microcomputer. That is, the power supply voltage is detected based on the induced voltage of the secondary winding 16c, and this power supply voltage detection result is compared with a reference voltage (for example, 100 V) preset in the internal memory, and the result of the power supply voltage detection is equal to or higher than the reference voltage. In some cases, the constant control permission signal Ss is provided to the inverter circuit 18, and when the input voltage detection result is lower than the reference voltage, the constant control release signal Sk is provided to the inverter circuit 18. The control circuit 17 controls the cooking by setting a cooking menu and a cooking time by switch input from various switches (not shown).

The inverter control circuit 18 has a microcomputer therein. The inverter control circuit 18 has a function as a magnetron output detecting means.
Anode current detector 1 constituting anode current detection means
9 is provided.
The anode current detector 19 is provided in the magnetron drive circuit 15 and detects the anode current of the magnetron 12.

The inverter control circuit 18 functions as output constant control means and release means. That is, when the output fixed permission signal Ss is given from the control circuit 17, that is, when the power supply voltage detection result is equal to or higher than the reference voltage, the transistor is controlled so as to make the output of the magnetron 12 constant based on the anode current detection result. 9 is changed. When the control circuit 17 supplies the fixed output signal Sk, that is, when the detection result of the power supply voltage falls below the reference voltage, the magnetron 12
Release the constant output control for. That is, in the present embodiment, control is performed so that the on-time of the transistor 9 is shorter than the maximum on-time in the case of constant output control.
As a result, the current flowing through the inverter circuit 7 does not increase, but conversely decreases from the current of the inverter circuit 7 during the maximum on-time.

According to the present embodiment, when the power supply voltage is the reference voltage or more, the inverter control circuit 8
Since the inverter circuit 7 is controlled so that the output of the magnetron 12 is constant based on the anode current,
In a situation where an excessive current does not flow through the inverter circuit 7, the constant output control of the magnetron 12 can be normally performed.

When the power supply voltage is lower than the reference voltage, the output control for the magnetron 12 is released by the release means in the inverter control circuit 8.
Excessive current can be prevented from flowing through the inverter circuit 7. As a result, it is possible to prevent a current higher than the maximum rating of the power outlet from flowing, thereby preventing an indoor power breaker from operating.

The present invention is not limited to the above-described embodiment, but can be implemented with various modifications without departing from the scope of the invention.

[0020]

As is apparent from the above description, the present invention provides an inverter circuit which rectifies an alternating current, switches its output by a switching element, and supplies it to a primary winding of a transformer, and a secondary circuit of the transformer. a magnetron driving circuit for driving the magnetron by rectifying the side output, said Magne
Magnetron output detection means for detecting the output of the tron,
Power supply voltage detecting means for detecting a power supply voltage; voltage determining means for determining whether or not the power supply voltage detection result is equal to or higher than a reference voltage; and the magnetron output detecting means when the power supply voltage detection result is equal to or higher than the reference voltage. Response to the
The invertor to keep the magnetron output constant.
And a canceling means for canceling the constant output control for the magnetron when the power supply voltage detection result is lower than the reference voltage.
If the power supply voltage does not decrease, the magnetron output can be controlled to be constant, and if the power supply voltage decreases, it is possible to prevent excessive current from flowing to the inverter circuit and prevent the indoor power breaker from operating. It has excellent effects.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing one embodiment of the present invention.

[Explanation of symbols]

In the figure, 4 is a rectifier, 7 is an inverter circuit, 8 is a transformer,
9 transistor (switching element), 12 magnetron 15 magnetron driving circuit, 16 is a step-down transformer, the control circuit 17 (power supply voltage detecting means, the voltage determining means), 18 an inverter control circuit (canceled means) Reference numeral 19 denotes an anode current detector ( magnetron output detecting means, anode current detecting means).

Claims (2)

(57) [Claims] 1. An inverter circuit for rectifying an alternating current, switching its output by a switching element and supplying it to a primary winding of a transformer, and a magnetron drive for rectifying a secondary output of the transformer to drive a magnetron Circuit and
Magnetron output detection for detecting the output of the magnetron
Means out, the power supply voltage detecting means for detecting a power supply voltage, and a voltage determining means for determining whether or not this power supply voltage detection result is equal to or higher than the reference voltage, when the power supply voltage detection result is the reference voltage or more Detection of magnetron output detection means
Make the output of the magnetron constant according to the result
A microwave oven comprising: a canceling means for controlling the inverter circuit and canceling the constant output control for the magnetron when the power supply voltage detection result falls below a reference voltage. 2. A magnetron output detecting means, comprising:
Current detection means to detect the anode current of
2. The electronic device according to claim 1, wherein the electronic device comprises:
range.