CN1255650C - Microwave oven - Google Patents

Abstract

A microwave oven is provided with a drive circuit for driving a magnetron and a control circuit for controlling the drive circuit to control an input electricity of the magnetron. The controlling circuit has a ROM for recording a control index and controls the drive circuit according to the control index such that the input electricity of the magnetron is controlled to be constant.

Description

Micro-wave oven

Technical field

The present invention relates to carry out the micro-wave oven (microwaveoven) of the input power control of magnetron (magnetron).

Background technology

Fig. 6 illustrates the circuit of existing micro-wave oven, particularly the drive circuit of magnetron 100.Be connected with drive circuit of magnetron 102 on AC power 101, this drive circuit 102 is made of DC power supply circuit 103, converter (inverter) circuit 104, high frequency transformer (high frequency transformer) 105 and voltage doubling rectifing circuit 106.

In said structure, converter circuit 104 comprises switch element (switching elements) 104a, 104b, this switch element 104a, 104b by control circuit 107 controlling carry out switch (on, off).Then, by this switch motion at the last generation of elementary winding (primary winding) 105a of high frequency transformer 105 high frequency electric, on the voltage doubling rectifing circuit 106 that the primary side with this high frequency transformer 105 is connected, produce voltage multiplying rectifier power, drive magnetron 100.

The output of above-mentioned magnetron 100 changes corresponding to the temperature of this magnetron 100, and the temperature of this magnetron 100 and driven by magnetron begin to rise simultaneously, and be relevant with it, and anode voltage reduces, and magnetron output reduces.As controlling a kind of mode that this magnetron is output as specified states, existing following mode.

That is, because in fact be difficult to directly detect magnetron output, so, by detecting the input power relevant and controlling input power, control magnetron output with magnetron output.As shown in Figure 6, the current sensing means 108 that is made of for example current transformer is set on the power circuit of AC power 101, detection current value and known voltage (normally definite value 100V) according to this current sensing means 108 detect input power, control the opening (ON) time of switch element 104a of above-mentioned converter circuit 104, the control high frequency electric is so that this input power becomes specified states, for example certain.

But, in such existing structure, current sensing means 108 checkout gears such as grade must be arranged, therefore the shortcoming of cost height (cost overrun) is arranged.

The present invention its objective is the micro-wave oven that provides the simple structure of a kind of usefulness to realize the control of input power in view of the above problems.

Summary of the invention

The starting point of the present invention is as follows.That is, one drives magnetron, and temperature just rises, and loss just produces, and anode voltage just reduces.Because this anode voltage reduces, magnetron output just reduces, and just shows as input power and reduces.If the power of the difference of the compensation and the input power of wanting just can recover magnetron output.At this,, test in advance by the present inventor and to try to achieve as the control data of the power that is used to compensate above-mentioned difference.That is, because from driving magnetron, along with time course, temperature rises and the loss of magnetron becomes big, so, for it is compensated input power is also increased.Obtain and make input power increase what control data this moment.

Therefore, the micro-wave oven of the present invention's the 1st sample attitude comprises

Be used to heat the magnetron of heating object;

Drive this driving magnetron device; And

Control the input power of above-mentioned magnetron and control the driving control device of above-mentioned drive unit,

Described driving control device has storage device, described memory device stores time dependence control data, this time dependence control data is used for the action elapsed time according to described magnetron, and the input power that is input to described magnetron from described drive unit is controlled to specified states;

Control described drive unit according to this time dependence control data.

The micro-wave oven of the present invention's the 1st sample attitude, even produce loss at magnetron, because driving control device is according to relying on magnetron data (control data) accessory drive in action elapsed time, do not become specified states so do not need checkout gear such as existing current sensing means just can control input power yet.Its result helps cheapization of cost (cost).

The micro-wave oven of the present invention's the 2nd sample attitude, driving control device also comprises

Data storage device during the stopping of data during storage magnetron stopping when stopping, and

Judge whether dwell time passes through the device of stipulated time,

When driven by magnetron begins, be judged as when when the driven by magnetron of last time stops, not passing through the stipulated time Data Control drive unit when being stored in when stopping stopping in the data storage device by described judgment means.

Along with end of cooking, after magnetron stopped, soon, the magnetron temperature was in the low state of anode voltage than normal temperature height.Begin the cooking if drive magnetron once more under this state, then fully the output of height and magnetron is not enough for input power, and cooking is failed.

Yet, the micro-wave oven of the present invention's the 2nd sample attitude, when when the driven by magnetron of distance last time stops, not passing through the stipulated time, promptly, when the magnetron temperature does not drop to room temperature, because of according to being stored in the control data accessory drive in the data storage device when stopping,, do not cause the cooking failure so the input power of magnetron can be high fully and do not have the deficiency of magnetron output.

The micro-wave oven of the present invention's the 3rd sample attitude comprises

Detect the temperature sensor of external air temperature, and

According to the detected temperatures that detects by this temperature sensor, compensate the compensation arrangement of described time dependence control data.

The action of micro-wave oven also changes corresponding to outside air temperature.That is, externally under the situation that air themperature is high (situation that anode voltage is low), the input power of micro-wave oven reduces, and externally under the situation that air themperature is low, input power increases.

Yet, the micro-wave oven of the present invention's the 3rd sample attitude, because can detect external air temperature by temperature sensor, the compensation arrangement of dependence control data when compensating according to this detected temperatures is so can prevent the change to the input power of magnetron input that produces because of external air temperature.

Description of drawings

Fig. 1 is the circuit diagram that one embodiment of the present of invention are shown.

Fig. 2 is the longitudinal sectional drawing that the schematic configuration of micro-wave oven is shown.

Fig. 3 is the figure that the variation of magnetron temperature, anode voltage, control characteristic, input power is shown.

Fig. 4 is the figure that illustrates for the variation of the input current of external air temperature.

Fig. 5 is the figure that the control content of control circuit is shown.

Fig. 6 is the circuit diagram that prior art is shown.

The explanation of Reference numeral

The 9-magnetron

12-drive circuit (drive unit)

35-control circuit (driving control device, storage device, data storage device, compensation arrangement when stopping)

The specific embodiment

Below, referring to figs. 1 through Fig. 5 one embodiment of the present of invention are described.At first, as shown in Figure 2, the shell 1 of micro-wave oven is made of outer container 2 and interior case 3, and interior case 3 inside constitute heating clamber 4.In this case 3 below dispose turntable motor (turntable motor) 5, the bottom of case 3 and outstanding to heating clamber 4 in its rotating shaft runs through is at its front end connection rotation net 6.On this rotation net 6, disposing the rotating disc 7 that to take down.Spatial portion between the right plate of the right plate of interior case 3 and outer container 2 constitutes Machine Room 8.In this Machine Room 8, the magnetron 9 as heater is installed on the right plate of interior case 3, the microwave (microwave) that produces with this magnetron 9 just the excitation mouth 3a from the right plate that is arranged on interior case to heating clamber 4 internal radiations.In addition, the temperature sensor 10 that is used to detect external air temperature is being set on above-mentioned Machine Room 8.

In addition, Fig. 1 illustrates the circuit diagram of one embodiment of the invention.The drive circuit 12 that drives magnetron 9 is connected to commercial ac power source 11.About this drive circuit 12, describe below.Two ends in AC power 11, the input terminal that connects the full-wave rectifying circuit 14 that constitutes by diode bridge (diode bridge) by capacitor (capacitor) 13, the opposing party's of full-wave rectifying circuit 14 lead-out terminal is connected to an end of smmothing capacitor (smoothing capacitor) 16 by choke coil (choke coil) 15, and another lead-out terminal is connected to the other end of capacitor 16.Constitute DC power supply circuit 17 by described capacitor 13, full-wave rectifying circuit 14, choke coil 15 and smmothing capacitor 16.

Dc source circuit (DC power line) 17a at this DC power supply circuit 17 is connecting converter circuit 18 on the 17b.The structure of this converter circuit 18 is as follows.At dc source circuit 17a, the switch element 19,20 that is connected in series between the 17b and constitutes by for example insulated gate bipolar transistor.Connect fly-wheel diode (freewheel diode) 21,22 in inverse parallel ground respectively with these switch elements 19,20.In addition, at dc source circuit 17a, capacitor 23 and 24 are being connected in series on the 17b.When the shared tie point of switch element 19,20 is connected with the terminal of the elementary winding 25a of high frequency transformer 25, be connected with the emitter stage of capacitor 27 with the switch element 20 of underarm (1ower arm) side by resistance 26.In addition, the shared tie point of above-mentioned capacitor 23,24 is connected with another terminal of the elementary winding 25a of high frequency transformer 25.

Primary side at above-mentioned high frequency transformer 25 is provided with secondary windings (secondary winding) 25b and Filament Winding (filament winding) 25c.On secondary windings 25b, connecting voltage doubling rectifing circuit 28.This voltage doubling rectifing circuit 28 is that 29,30 and two capacitors 31,32 of two diodes (diode) and two resistance 33,34 are connected as shown in figure, adds the dc high voltage power by this voltage doubling rectifing circuit 28 rectifications on magnetron 9.

The switch element 19 and 20 of above-mentioned converter circuit 18 utilizes control circuit 35, carries out switch control by the dutycycle (デ ユ-テ イ-ratio) of high frequency.Its result, high frequency electric is crossed, induction of high frequency electric current on secondary windings 25b and Filament Winding 25c in the elementary winding 25a upper reaches of above-mentioned high frequency transformer 25.The high frequency electric of responding on secondary windings 25b becomes high-voltage direct current by voltage doubling rectifing circuit 28, is added on the magnetron 9, and then magnetron 9 oscillation actions.

Control circuit 35 is made of microcomputer.Control circuit 35 utilizes the ETAD expected time of arrival and departure with the switch element 19,20 of converter circuit 18 to change over linearity (linear) with compensating mutually, input power that will stepless terrace land control magnetron 9.Under this situation, in one-period, there is switch element 19 to replace for "open" state for " pass " and switch element 20 for " pass " state and switch element 19 (OFF) for " opening " and switch element 20, if increase the time that switch element 19 is opened, just can make the input current of magnetron 9 become big, the anode voltage of magnetron 9 rises, and just can improve output.

In addition, constitute the microcomputer of above-mentioned control circuit 35, comprise CPU, ROM and RAM.The function of the storage device of the data when this ROM has stopping of storage time dependence control data described later and magnetron.In addition, give the switch input to above-mentioned control circuit 35 from switch input circuit 36, this switch input circuit 36, but comprise time setting switch and starting switch (start switch) etc. as switch.In addition, turntable motor 5 is also driven by the drive circuit 37 of control circuit 35 controls, has again, is connecting AC power 11 on motor drive circuit 37.

Below, describe about above-mentioned time dependence control data.In Fig. 3, under the condition of for example normal temperature (20 ℃), under the situation of certain action, the temperature of magnetron 9 is shown in characteristic curve Tm in the dutycycle that makes converter circuit 18 (ETAD expected time of arrival and departure of switch element 19), rise during originally 5 minutes, just be roughly certain afterwards.Thereupon, the loss of magnetron 9 increases, and anode voltage ebm also reduces in originally 5 minutes roughly, just is roughly certain afterwards.Thereby, the output of magnetron 9 so that input power also almost reduce gradually during originally 5 minutes.This part is necessary to make the input power increase.Therefore, in the present embodiment, control characteristic y is set in investigation in advance, changes the control data of the dutycycle of converter circuit 18 as the action elapsed time that relies on magnetron.

Promptly, under normal temperature condition, and use specified loads, will from action beginning after 5 minutes input power be the dutycycle of maximum (being maximal input under the big state of the loss of magnetron 9), the dutycycle control characteristic of ETAD expected time of arrival and departure T of switch element 19 that is converter circuit 18 is when " 100 ", after beginning 5 minutes from action (state that the loss of magnetron 9 is big), the input power of magnetron 9 is that the dutycycle control characteristic that rated input power is used is good for " 96 ".

From originally, if drive magnetron 9,, therefore, set dutycycle control characteristic y because too much in action beginning initial stage (losing little state) input power with this dutycycle index " 96 ", make the input power of this part reduce.That is, dutycycle control characteristic y shown in the characteristic curve y of Fig. 3 like that, be " 86 " at action time started point, after 5 minutes, improve with regard to straight line, up to above-mentioned " 96 ", just keep should " 96 " constant afterwards.

Thereby establishing this dutycycle control characteristic is y, and the elapsed time is x minute, and the action beginning increased according to y=((96-86)/5) x+86 expression formula during 5 minutes.After 5 minutes, set y=96 for.The dutycycle control characteristic y of such setting is stored among the ROM of control circuit 35.In addition, this dutycycle control characteristic y will compensate according to external air temperature (temperature within doors of micro-wave oven is set), the following setting of this penalty constant h, and be stored among the above-mentioned ROM.That is, at the maximum input current that illustrates on the characteristic curve Ij of Fig. 4 under the situation that does not have compensation about dutycycle control characteristic y for external air temperature.Under this situation, if make external air temperature be lower than roughly 15 degree, maximum input current just surpasses 14.50A, allows that to maximum input current is approaching.

Therefore, in the present embodiment, when establishing external air temperature and being t, h=0.98 when making temperature compensation coefficient h in 10 ℃＜t＜15 ℃, h=0.96 during t≤10 ℃, h=1.00 during 15 ℃≤t (not compensation) has again, and with dashed lines Hi illustrates the maximum current after the compensation.

Below, with reference to the flow chart of Fig. 5 the input power control based on the magnetron of control circuit 35 is described.After the 36 setting cooking times, starting switch one leaves, and just begins the control shown in this flow chart by the switch input circuit.That is, in step (step) S1, whether passed through the stipulated time when judging, for example more than 5 minutes apart from end of cooking last time (stopping of magnetron 9).If passed through, just carry out the transition to step S2, set the initial value of the time x that " 0 " uses as control characteristic.Then, carry out the transition to step S3, set " 0 " as cooking time t (resetting).

In following step S4, begin counting (count) about time x and time t.Then, in step S5, judge time x about above-mentioned control characteristic y (minute) whether be 0＜x≤5, if in this scope, just carry out the transition to step S6, according to expression formula y=((96-86)/5) x+86 that represents, set control characteristic.

In step S7, the detected temperatures setting compensation coefficient h according to temperature sensor 10 compensates above-mentioned control characteristic y.That is, deciding hy again is control characteristic.

In step S8, according to control characteristic hy control change device circuit 18.That is, the ETAD expected time of arrival and departure of the switch element 21 of control change device circuit 18 is (hy/100) T.In following step S9, judge whether to have arrived and set cooking elapsed time t, do not arrive if, just turn back to step S4, in turn execution in step S5, S6, S7, S8, S9, S4.Like this, with time x through setting control characteristic y simultaneously.Under this situation, although reduce anode voltage ebm gradually, compensated because of it reduces part, its result, input power just are controlled so as to necessarily.

Cooking elapsed time x is if surpass 5 minutes, and just " NO " according to step S5 carries out the transition to step S10, and setting control characteristic y is " 96 ".According to the ETAD expected time of arrival and departure of the switch element 21 of this control characteristic y=96 control change device circuit 18, and then the control input power becomes certain.

At this,, just store the time x on this time point if arrived the cooking time that gastronomical process time t has been set.Promptly store the control characteristic y that represents by time x.If the stored time is x '.Then, close the switch element 21,22 of converter circuit 18, stop the driving of magnetron 9.

In above-mentioned step S1, during not through 5 minutes, just carry out the transition to step S12 at the end of cooking of distance last time, read the time x ' of last stored, the initial value of fixed time x by step S4 counting is x '.Then,, carry out the transition to step S4 and step S5, further carry out the transition to step S6 or step S10, ask control characteristic y through step S3.That is, in the cooking of this situation the control of input power since the control characteristic of time point of end of cooking last time.

Like this, according to present embodiment, even produce loss at magnetron 9, but owing to control the converter circuit 18 of drive circuit 12 according to being stored in time dependence control characteristic y in the memory by control circuit 35, therefore, do not need checkout gears such as existing current sensing means also can control input power and become specified states, this occasion can be controlled to necessarily (with reference to the characteristic curve Q of Fig. 3).Its result can help cheapization of cost.

In addition, in the above-described embodiments, can control input power for certain, but also can set control characteristic, make and for example improve input power, make its reduction afterwards at the heating beginning initial stage.

In addition, according to present embodiment, data storage device, for example ROM when control circuit 35 comprises stopping of control characteristic y during the storage magnetron is when stopping, when driven by magnetron begins, when judgement is not passed through the stipulated time when the magnetron of last time stops, from beginning to drive the control beginning, even the cooking failure does not take place continuous carrying out cooking then yet corresponding to the specific control characteristic y that stops the elapsed time that is stored in the ROM.

Along with end of cooking, after magnetron 9 stopped, soon, the magnetron temperature was also than normal temperature height, and anode voltage is in low state.Drive normal keyholed back plate once more and begin the cooking under this state, input power is little can be fully not high, and magnetron output is not enough, the cooking failure.

Yet, when the present invention begins in driven by magnetron, when from the end of cooking of last time the time, not passing through official hour, promptly, judge when the magnetron temperature does not descend till room temperature, because of the control data in the data storage device comes accessory drive when stopping according to being stored in, so can make the input power of magnetron high fully, magnetron output can be sufficient, can not cause the cooking failure.

In addition, the present invention compensates control characteristic y according to this detected temperatures, so can prevent the change that the input power of magnetron produces because of external air temperature because detect external air temperature by temperature sensor 10.

Have again, in the above-described embodiments,, but boosting or primary cut-out of the voltage that for example changes DC power supply circuit 17 can be set also, control it by the control data of setting in addition by the ETAD expected time of arrival and departure of the switch element 21 of control characteristic y control change device circuit 18.

From above explanation as can be known, the present invention can realize the control of input power with simple structure, can realize cheapization of cost.

Claims (3)

1. a micro-wave oven is characterized in that, comprises

Magnetron;

Drive this driving magnetron device; And

Control the driving control device of described drive unit,

Described driving control device has storage device, described memory device stores time dependence control data, this time dependence control data are used for according to the action elapsed time of described magnetron the input power that is input to described magnetron from described drive unit being controlled to specified states;

Control described drive unit according to this time dependence control data.

2. micro-wave oven as claimed in claim 1 is characterized in that,

Driving control device comprises

Data storage device during the stopping of data during storage magnetron stopping when stopping; And

Judge whether dwell time passes through the device of stipulated time,

When driven by magnetron begins, be judged as when when the driven by magnetron of last time stops, not passing through the stipulated time Data Control drive unit when being stored in when stopping stopping in the data storage device by described judgment means.

3. micro-wave oven as claimed in claim 1 is characterized in that, comprises

Detect the temperature sensor of external air temperature; And

According to the detected temperatures that detects by this temperature sensor, compensate the compensation arrangement of described time dependence control data.

Images