TW200401872A - 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

200401872 V. Description of the invention (1) [Technical field to which the invention belongs] The present invention relates to a microwave oven that performs input power control of a magnetron. [Prior Art] FIG. 6 shows a conventional electric circuit of a microwave oven, and particularly a drive circuit of a magnetron 100. When the AC power supply 101 is connected to the magnetron drive circuit 102, the drive circuit 102 has a DC power supply circuit 103, an inverter circuit 104, and a high frequency transformer (high frequency). transformer) 105. Voltage doubler rectifier circuit 106. In the above configuration, the inverter circuit 104 includes switching elements 104a and 104b. These switching elements 104a and 104b are formed by The control circuit 10 is turned on / off (ο η, 0ff). Therefore, by using this on / off, a primary coil (Primary w Γη ding) 1 0 5 a of the high-frequency transformer 105 generates a high-frequency current, and a voltage doubler rectification circuit connected to the secondary side of the high-frequency transformer 105 is used. 106 generates voltage-doubled rectified power to drive the magnetron 100. However, the output of the above-mentioned magnetron 100 is changed due to the temperature of the magnetron, and the temperature of the magnetron 100 will rise along with the start of the magnetron driving. Related to this is that the anode voltage will decrease and the magnetoelectricity will decrease. Tube output will decrease. One way to control the output of this magnetron is as follows. That is, it is actually quite difficult to directly detect the output of the magnetron, so it is necessary to detect the input power related to the output of the magnetron and then control the input power to control the output of the magnetron. As shown in Figure 6

11068pif.ptd Page 5 200401872 V. Description of the invention (2) The power line of the same AC power supply 1 0 1 is provided with a current detection device 1 0 8 constituted by a converter, for example, and using this current detection device 1 0 8 The detection current and the known voltage (usually a certain value of 100 V [volts]) to detect the input power. In order to make this detected input power to a certain value, the switch of the aforementioned inverter circuit 104 should be controlled. The opening (0 N) time of the component 10 4 a, and the south frequency current should be controlled. However, in the conventional configuration, since a detection device such as the current detection device 108 is necessary, there is a disadvantage that the cost is too high. In view of the foregoing, one of the objects of the present invention is to provide a microwave oven whose control of input power can be achieved by a simplified structure. SUMMARY OF THE INVENTION Therefore, the object of the present invention is to focus on the following. When the magnetron is driven, the temperature rises and losses occur, and the anode voltage decreases. Because the reduction of the anode 6-pole voltage will reduce the output of the magnetron, and the input power will be low. If the input power of the phase difference is increased relative to the predetermined input power, the output of the magnetron can be restored. Here, the present inventors obtained experimental data in advance in order to supplement the input power of the phase difference portion described above. That is, with the passage of time from the start of the driving of the magnetron to the increase in temperature and the loss of the magnetron, the input power also increases. Find out how much input control data needs to be increased at this time. Based on the foregoing and other objectives, the present invention provides a microwave oven, including: a magnetron that electrically induces a heated object to be heated, a driving device that drives the magnetron, and controlling input power to one of the magnetrons,

11068pif.ptd Page 6 200401872 V. Description of the Invention (3) A drive control device for controlling a drive device. The aforementioned drive control device is provided with a memory device for memorizing control data for controlling the input power of the magnetron to a fixed value, and controlling the drive device based on the control data. In the above invention, even if a magnetron is driven to cause a loss, the drive control device controls the drive device based on the control data (c ο ntr ο 1 data), so a conventional detection device such as a current detection means is not required. The input power can be controlled to a fixed value. As a result, the cost can be reduced. The driving control device of the present invention includes a data storage device for storing control data when the driving of the magnetron is stopped. When the magnetron driving starts, under the condition that the previous magnetron driving stop has not elapsed for a predetermined time, the 'driving device is controlled based on the control data stored in the data storage device at the time of stopping. When the magnetron is driven to stop with the end of the conditioning, the magnetron is temporarily at a high temperature. In this state, if you want to adjust again, when the magnetron drive is started, the anode voltage will appear low. Therefore, in the initial value of the control data, the input power will be small and the magnetron output will be insufficient. There is a possibility of heating conditioning failure. However, in the above invention, when the magnetron driving is started, under the condition that the previous magnetron driving stop has not elapsed for a predetermined time, that is, under the condition that the magnetron temperature has not dropped, according to the data at the time of stopping The control data stored in the memory device controls the driving device, so that even in the case of continuous conditioning, the magnetron can obtain sufficient input power

11068pif.ptd Page 7 200401872 V. Description of the invention (4) The force will not cause the output of the magnetron to be insufficient, so it will not cause the adjustment failure. The microwave oven of the present invention further includes: a temperature sensor (sen sor) for detecting the temperature of the outside air, and a correction device for correcting the control data according to the detected temperature from the temperature sensor. When the control data is at normal temperature, when the outside air temperature is high (the anode is in a low state), using its control data will make the input power at the beginning of the magnetron drive slightly lower, and when the outside air temperature is low, then The input power will be slightly higher. However, in the above-mentioned invention, the temperature sensor is used to detect the outside air temperature, and correction means for correcting the control data based on the detected temperature is provided, so that the input power of the magnetron can be prevented from changing due to the outside air temperature. ^ In order to make the above and other objects, features, and advantages of the present invention more comprehensible, a preferred embodiment is described below in detail with the accompanying drawings as follows: [Embodiment] Hereinafter, referring to the 1 to 5 illustrate an embodiment of the present invention. First, in the second figure, the main body 1 of the microwave oven includes an outer box 2 and an inner box 3, and the inside of the inner box 3 is a heating chamber 4. As shown in FIG. A turntable motor 5 is arranged on the outer bottom of the heating chamber 4, and its rotary shaft protrudes in the heating chamber 4 and is connected to the turning net 6. A rotary disc 7 is detachably arranged on the rotary net 6. The space between the right side plate of the inner box 3 and the right side plate of the outer box 2 serves as a machine room 8. In the machine room 8, the inner box 3

11068pif.ptd Page 8 200401872 V. Description of the invention (5) The magnetized magnetron 9 is installed on the right side plate. The microwave generated by this magnetron 9 is supplied from the excitation port 3a to the heating chamber 4 . In addition, a temperature sensor 10 for detecting the temperature of the outside air is disposed in the mechanical room 8. The driving circuit 12 is shown in FIG. 1 as a driving means connected to a commercial AC power source 11 for driving and controlling the magnetron 9. Next, the driving circuit 12 will be described. The two ends of the AC power source 1 1 are connected to a full-wave rectifier circuit 14 formed by a diode bridge connection through a capacitor 13. One side of this output terminal is connected to a choke coil 15. One end of the smoothing capacitor 16 is connected to the other end of the capacitor 16. Using these capacitors 1, 3, full-wave rectifier circuit 14, 4, choke coil 1, 5, and smoothing current generator 16 constitute a DC power supply circuit 17. The DC power lines 17 a and 17 b of the DC power supply circuit 17 are connected to the inverter circuit 18. The inverter 18 is configured as below and below. Switching elements 19, 20 made of, for example, IGB are connected in series between the DC power sources 17a, 17b, and bypass two-wheel (freewheel diodes) 21, 22 are connected in antiparallel. Capacitors 2 3, 2 4 are connected in series to the power line 17 1 7 b. Therefore, the common connection terminal of the switching element 9 is a terminal connected to the primary coil 25 of the high-frequency transformer 25, and is connected to the emitter of the switching element 20 of the lower arm via a resistor 26 and a capacitor 27. . Furthermore, the common connection point of the capacitors M, and is a terminal connected to the primary coil 25a'24 side of the high-frequency transformer 25. '^ Another

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Page 9 20041872 V. Description of the invention (6) On the secondary side of the above-mentioned high-frequency transformer 25, a secondary winding 25b and a filament winding 25c are provided, and the secondary coil 25b is connected To double the voltage rectifier circuit 2 8. This voltage doubler rectifier circuit 28 series, as shown in the figure, consists of two diodes 29, 30, two capacitors 31, 32 and two resistors 33, 34 to form a connected circuit to apply high voltage to the magnetron 9 . The switching elements 19 and 20 of the aforementioned inverter 18 use the control circuit 35 shown in the first to control the on / off of the high-frequency capacitor operating ratio (dutyrati 〇) to let the south frequency current flow to The primary coil 2 5 a ′ induces a south frequency current at > the primary coil 2 5 b and the wound coil 2 5 c. The high-frequency current system induced in the secondary coil 2 5 b is high-voltage by the voltage doubler rectifying circuit 28 and is applied to the magnetron 9 to thereby make the magnetron 9 oscillate. The control circuit 35, which is a drive control means and a correction means, has a structure including a Wei computer. By changing the on time of the switching element 19 of the inverter circuit 18 to linear, it is possible to control the input power steplessly. At this time, in particular, during a period of the switches 19 and 20, the switching element 19 is turned on and the switching element 20 is turned off, and the switching element 19 is turned off and the switching element 20 is turned on. In a state, when the on-time of the switching element 19 becomes longer, the input current can be increased, so that the anode voltage of the magnetron 9 can be increased, and the output can be increased. Furthermore, the microcomputer of the control circuit 35 includes a CPU, a ROM, and a RAM. The ROM has a function of storing control data and a function of storing data at the stop time as control data when magnetization is stopped. The control circuit 3 5 is attached to the switch input circuit 3 6.

11068pif.ptd Page 10, 200401872 V. Switch input from (7), and although not shown, this switch input circuit 36 is a time setting switch, start switch, etc. . In addition, the turntable motor 5 is controlled by a control circuit 35 through a drive circuit 37, and the drive circuit 37 is connected to an AC power source 11. Next, the above control data will be described. In FIG. 3, for example, under normal temperature (20 degrees Celsius) temperature conditions, for the magnetron 9, the drive mode of the inverter 18 (on time of the switching element 19) is in a certain state from the beginning to the beginning. In this case, when the magnetron 9 is driven, the temperature of the magnetron 9 rises during the first 5 minutes, as shown by the characteristic line Tm, and then becomes slightly constant after that. Along with this, the loss of the magnetron 9 increases, and the anode voltage e b m also decreases between approximately the first 5 minutes, and then becomes slightly constant after that. Therefore, the output of the magnetron 9 and even the input power are reduced. To this end, ‘input power needs to be increased. In this embodiment, for the drive mode of the inverter circuit 18, the control index y, which is the control data, should be checked and set in advance. In other words, under normal temperature conditions, under a specified load, the drive mode of the maximum allowable input power of the magnetron 9 obtained after 5 minutes (the maximum input power state when the loss of the magnetron 9 is large), When the opening time of the switching element 19 of the inverter circuit 18 in this case is used as the reference control index [1 0 0], it is preferable that after 5 minutes (the loss of the magnetron 9 is in a large state), The control index of the fixed input voltage of the magnetron 9 is obtained to the degree of [9 6]. From the beginning, if we use this control index as [9 6] to drive the magnetron 9,

11068pif.ptd Page 11 200401872 V. Description of the invention (8) There may be too much input power in the initial stage of magnetron driving (small loss state). For this reason, it is necessary to make a control to reduce the input power of this part. index. That is to say, when the control index is [8 6] at the start of driving as shown by the characteristic line y in FIG. 3, after 5 minutes, it rises straight to the above [9 6], and thereafter remains at [9 6] . Therefore, using y as the control index of this control data, and taking X as the elapsed time, y = ((96-86) / 5 · x + 86) is at 0 &lt; x &lt; = 5th Temple, and y = 96, At x &gt; 5 o'clock. This control index y can be stored in the ROM of the control circuit 35. In addition, the control index y is corrected by the outside air temperature (the temperature of the room where the microwave oven is installed), and the correction constant h is set as follows, and then stored in the aforementioned R 0 Μ. That is, the characteristic line Ij in Fig. 4 shows the maximum input current for the outside air temperature when the control index y is not corrected. In this case, when the outside air temperature is lower than about 15 degrees, the maximum input current will exceed 14.50A, which is close to the maximum allowable input current. Here, in this embodiment, when the outside air temperature is t and 10 ° C &lt; t <15 ° C, the temperature correction coefficient h = 0.98, and when t &lt; = 10 ° C, h = 0.96, and when 15 degrees Celsius &lt; = t, h = l (without correction), and the maximum current after correction is shown as a dotted line H i. Regarding the input power control of the control circuit 35, please refer to the flowchart in FIG. 5 for explanation. With the switch input circuit 3 6, when the start switch (s t a r t s w i t c h) is turned on (0 N) after the conditioning time has been set, the control shown in this flowchart is started. That is, in step S1, it is determined whether or not a predetermined time has elapsed from the end of the previous conditioning, for example, 5 minutes or more. If yes, go to step S2, the initial period of time X for controlling the index

11068pi f.ptd Page 12 200401872 V. Description of the invention (9) The value is set to [0]. Then, the process proceeds to step S3, and the conditioning time t is set to [0] (reset, reset). Next, in step S4, the count time X and time t are started. In step S5, it is judged whether the time x (minutes) of the control index y is 0 &lt; X <two 5. If it is in this range, go to step S6, and make the control index y = ((96 -86) / 5 · x + 86). Then, in step S7, a correction coefficient h is set based on the detected temperature of the temperature sensor 10, and the above-mentioned control index y is corrected. That is, treat h · y as the new control index. Then, in step S8, the inverter circuit 18 is controlled based on the control index h · y. That is, the opening time of the switching element 21 of the inverter 18 is controlled by (h · y / 1 0 0) · T. Next, in step S9, it is judged whether the elapsed conditioning time t has reached the set conditioning time, and if it has arrived, it returns to step S4, and then loops back to steps S5, S6, S7, S8, S9, and S4 ( 1 ο ο p). In this way, the control index y and the time elapsed are set together. In this case, because the anode voltage ebm is sequentially reduced, and the input power is reduced according to the amount of the decrease, the final input power can be controlled to a certain value. When the time χ exceeds 5 minutes, it proceeds to step S 1 0 according to [No] in step S 5 and sets the control index y to [9 6]. The ON (0 N) time of the switching element 21 of the inverter circuit 18 is controlled based on the control index y, and the input power is controlled to a certain value based on this. Here, when the conditioning elapsed time t reaches the set conditioning time, the time χ at this time is memorized. That is, using time χ,

11068pif.ptd Page 13 200401872 V. Description of the invention (ίο) System index y memory. Let the stored time be X '. Then, the switching elements 2 1 and 2 2 of the inverter circuit 18 are turned off (0 F F) to stop the driving of the magnetron 9. In the aforementioned step S1, if 5 minutes have not elapsed since the previous conditioning time, the process proceeds to step S12, the time X 'of the previous memory is read out, and the beginning of the time X counted in step S4 The value is set to X '. Then, after step S3, proceed to steps S4 and S5, and then proceed to step S6 or S7 to obtain the control index y. That is, the control index y will start from the control index at the end of the previous conditioning. According to the above-mentioned embodiment, even if the magnetron 9 is driven and a loss occurs, the control circuit 35 can be used to control the inverter circuit 18 of the driving circuit 12 according to the control index y. Therefore, a conventional current is not required. A detection device such as a detection means can control the input current to a constant value (refer to the characteristic line Q in FIG. 3). As a result, costs can be reduced. In this case, although the input power can be controlled to a fixed value, for example, the input power can be increased at the initial stage of heating and then decreased thereafter. In this case, the control index may be obtained in advance. In addition, according to this embodiment, the control circuit 35 is provided with a ROM that is a means for storing data at the time of stopping the control index y when the magnetron drive is stopped. When the magnetron drive is started, it is not Drive control is started from the control index y memorized in the ROM under the condition of a predetermined time, so even continuous heating conditioning will not cause the heating conditioning to fail. That is, when the magnetron 9 is driven to stop as the conditioning is completed, the magnetoelectricity

11068pif.ptd Page 14 200401872 V. Description of the invention (11) The temperature of the tube is temporarily high. If conditioning is to be restarted in this state, and the driving of the magnetron 9 is started, the anode voltage is low. The initial value of this control index is that the input power is small and the magnetron output is insufficient, which may cause heating conditioning failure. . As mentioned above, when the magnetron drive starts, under the condition that the predetermined time has not elapsed since the previous stop of the magnetron drive, that is, under the condition that the temperature of the magnetron has not dropped, the control index stored in the ROM is started. Input power control, even in the case of continuous conditioning, the magnetron can obtain sufficient input power without causing insufficient output of the magnetron, which will not cause conditioning failure. Furthermore, according to this embodiment, the temperature of the outdoor air is detected by the temperature sensor 10, and the control index y is corrected based on the detected temperature, so that the input power to the magnetron can be prevented from being changed due to the temperature of the outdoor air. ^ In the above embodiment, although the opening time of the switching element 21 of the inverter circuit 18 is controlled using the control index y, for example, the voltage of the boost DC power circuit 17 is changed or a high-voltage cutoff is set Control, and use additional control data to control these things. From the above description, it can be seen that the present invention can realize the control of the input power with a simplified structure and can reduce the cost. Although the present invention has been disclosed in the preferred embodiment as above, it is not intended to limit the present invention. Any person skilled in the art can make some modifications and retouching without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection shall be determined by the scope of the attached patent application.

11068pif.ptd Page 15 200401872 Brief description of the drawings [Simplified description of the drawings] Fig. 1 shows an electrical circuit diagram of an embodiment of the present invention; Fig. 2 shows a schematic front view of a schematic structure of a microwave oven; Figure 4 shows the change of magnetron temperature, anode voltage, control index, and input power; Figure 4 shows the change of input current to the outside air temperature; Figure 5 shows the control content of the control circuit; and Figure 6 shows A conventional electrical circuit diagram. [Illustration of diagrammatic representation] 1: Main body 2: Outer box 3: Inner box 4: Heating chamber 5 • Turntable motor 6: Turntable 7: Turntable 8: Machine room 9, 100: Magnetron 1 0: Temperature sensor 1 1, 1 0 1: AC power supply 121, 37, 102: Drive circuit (driving means) 13, 23, 24, 27, 31, 32: Capacitor 14: Full-wave rectifier circuit 15 Coil 16: smoothing capacitor 1 7, 1 0 3: DC power supply circuit 1 a, 1 7 b: DC power line (DC ρ 〇wer 1 ine) 18, 104: inverter circuit 1 9, 2 0, 1 0 4 a, 1 0 4 b: switching elements 21, 22: bypass diode (freewheel diode) 25, 105: means of data storage and correction for high frequency transformer )

11068pif.ptd Page 16 20041872 Simple illustration 2 5a: primary, coil 25b: secondary, secondary winding 25c: filament winding 26, 33, 34: resistance 2 8, 10: 6 times Voltage rectifier circuit 2 9, 3 0: Diode 3 5, 1 7: Control circuit (driving control means, memory means, stop 3 6: Switch input circuit 1 8: Current detection device

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Claims (1)

200401872 VI. Scope of patent application 1. A microwave oven, comprising: a magnetron for inducing electric heating of a heated object; a driving device for driving the magnetron; and a driving control device for inputting power to one of the magnetrons Performing control to control the driving device, wherein the driving control device is provided with a memory device to memorize control data of controlling the input power of the magnetron to a set value of control data and to control the driving according to the control lean material Device. 2. The microwave oven according to item 1 of the scope of the patent application, wherein the drive control device includes a data storage device to memorize control data when the magnetron driving is stopped, wherein when the magnetron driving starts, the former Under the condition that the magnetron driving is stopped for a predetermined period of time, the driving device is controlled according to the data at the time of the stop & the control data stored in the memory device. 3. The microwave oven according to item 1 of the scope of the patent application, further comprising: a temperature sensor to detect the outside air temperature; and a correction device to correct the control data based on the detected temperature from the temperature sensor. 11068pif.ptd Page 18