JP6643176B2 - Induction heating cooker - Google Patents

Description

  The present invention relates to a high-frequency heating cooker.

  As a background art of the present technical field, there is JP 2010-123356 A (Patent Document 1). The summary section of Patent Document 1 states that “a magnetron driving power supply 30 including an inverter circuit 48 for driving the magnetron 31, an input current detection circuit 52 for detecting an input current, and a control circuit 50 for controlling the switching element 44. The power supply synchronization timing detection circuit 51 includes a power supply synchronization timing detection circuit 51 that detects zero volts of the AC power supply 41, and drive data that determines the ON time and the OFF time of the switching element 44. After the magnetron 31 has warmed up using the drive data based on the zero volts of the AC power supply detected in the above, in a portion where the voltage of the AC power supply 41 is low, the drive data is controlled with a long ON time ratio of the drive data. At a position just before the apex of the power supply 41, the ON time ratio of the drive data is reduced. The control circuit 50 controls the inverter circuit 48. "And is described.

JP 2010-123356 A

  In the configuration of the inverter circuit described in Patent Document 1, a measurement error may occur with respect to the input current detected by the input current detection circuit (input side error).

  In general, there is an individual difference in the efficiency of the magnetron driven by the inverter, and the oscillation output with respect to the input current differs greatly in each magnetron. Therefore, when adjusting the data signal so that the input current when the magnetron is transmitted with a specific output becomes a specific value, it is necessary to set a large adjustment range, and the time required for the adjustment becomes long.

  That is, after adjusting the input power detection circuit of the magnetron drive power supply, it is necessary to adjust the data signal in a state where the magnetron drive power supply is incorporated in the high-frequency heating cooker, and it takes a long time to make adjustments at the manufacturing stage. There is.

  Therefore, an object of the present invention is to reduce the adjustment time for input and output of a high-frequency heating cooker.

The present invention has been made to solve the above problems, and a magnetron, a rectifier circuit connected to an AC power supply to convert the power supply to DC, an inverter circuit connected to the rectifier circuit and driving the magnetron, A drive circuit for driving a switching element of the inverter circuit;
An input current detection circuit that detects a current flowing through the inverter circuit, an ON timing detection circuit that outputs an ON timing of a switching element of the inverter circuit, and a switching element of the inverter circuit based on a detection result of the input current detection circuit. Control means for controlling the ON time necessary for turning on the switching element corresponding to an area obtained by dividing a half-cycle time axis of the AC power supply into a plurality of areas. Storage means for storing, and a direct access memory, wherein the drive data is different according to the frequency of the AC power supply, and the drive data has the same ON time in each area, and the ON time in each area. is configured to be shorter toward the peak from zero of the alternating current power supply voltage, the drive data before They are stored differently depending on the detection current of the input current detecting circuit, transferring the direct access memory is driving data stored in the storage means to the drive circuit as a drive signal of the switching element via the I / O Is what you do.

  ADVANTAGE OF THE INVENTION According to this invention, the adjustment time regarding the input and output of a high frequency heating cooker can be shortened.

1 is an external perspective view of a high-frequency heating cooker equipped with a magnetron driving power supply according to one embodiment of the present invention. FIG. 5 is a sectional view taken along line VV of FIG. 1. The control block diagram explaining the power supply for magnetron drive of the high frequency heating cooker concerning one example of the present invention. The block diagram explaining control of the high frequency heating cooker concerning one example of the present invention. The voltage waveform diagram of the main part of the control block diagram of the power supply for magnetron drive of the high frequency heating cooker concerning one Example of this invention. FIG. 4 is an explanatory diagram of a pulse for each area of the high-frequency heating cooker according to one embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
In the figure, a main body 1 of a high-frequency heating cooker puts a food to be heated (an object to be heated) in a heating chamber 17, and heats and cooks the food using high-frequency energy and heat of a heater.

  The door 2 is opened and closed so that food can be taken in and out of the heating chamber 17. By closing the door 2, the heating chamber 17 is sealed, preventing leakage of high frequency waves used when heating the food, And heat can be efficiently heated.

  The handle 7 is attached to the door 2 to facilitate opening and closing of the door 2, and has a shape that is easy to grasp by hand.

  The glass window 4 is attached to the door 2 so that the state of the food being cooked can be checked, and is made of glass that can withstand high temperatures due to heat generated by a heater or the like.

  The input unit 5 includes a display unit 5a and an operation unit 5b provided on the operation panel 3 below the front surface of the door 2. The operation unit 5b includes heating means such as high-frequency heating and heater heating, heating intensity and heating time. The display unit 5a displays the contents input from the operation unit 5b and the progress of cooking.

  The exhaust port 8 is a part for discharging cooling air after cooling the components and steam generated when the food is heated.

  The machine room 18 is a space provided below the heating chamber 17, and includes a magnetron 31 for heating food, a waveguide 21 connected to the magnetron 31, and a magnetron drive for supplying power to the magnetron 31. An inverter board 480 on which the power supply 30 is mounted, other various components described below, a cooling unit 62 for cooling these various components, and the like are attached.

  A substantially central portion of the bottom surface of the heating chamber 17 is depressed in a concave shape, in which a rotating antenna 19 is installed. High-frequency energy radiated by the oscillation of the magnetron 31 is output from the waveguide 21 and the rotating antenna driving means 23. The shaft 23 a flows into the lower surface of the rotating antenna 19 through the coupling hole 22 penetrating therethrough, and is diffused by the rotating antenna 19 and radiated into the heating chamber 17. The rotating antenna 19 is connected to an output shaft 23a of the rotating antenna driving means 23.

  A hot air unit 11 is attached to the rear of the heating chamber 17, a hot air fan 15 for efficiently circulating air in the heating chamber 17 and a hot air heater 14 are installed in the hot air unit 11, and a hot air There is a hole that becomes the path of the street.

  The hot-air fan 15 rotates by driving a hot-air motor 13 attached to the outside of the hot-air unit 11, circulates air with the heating chamber 17 through a hole provided on the inner wall surface of the heating chamber, and circulates with the hot-air heater 14. Heat the air.

  On the back side of the ceiling of the heating chamber 17, a grill heating means 12 composed of a heater is attached. The grill heating means 12 is formed by winding a heater wire around a mica plate to form a flat shape, pressing the mica plate against the back side of the top surface of the heating chamber 17 and fixing the same, and heating the top surface of the heating chamber 17 to feed the food in the heating chamber 17. It is baked by radiant heat.

  The temperature detecting means 16 detects the temperature of the heating chamber 17 heated by each heater, and a thermistor or the like is used as the detecting means.

  The table plate 20 is for placing food, has heat resistance so that it can be used for both heater heating and high-frequency heating, has good high-frequency transmission, and has no problem in hygiene. It is molded of the material.

Next, the block diagram of FIG. 4 will be described.
Reference numeral 41 denotes an AC power supply for operating control components and electric components of the main body 1. Reference numeral 60 denotes a range heating means, which includes a magnetron 31 for heating food with high-frequency energy, and a magnetron driving power supply 30. The main control means 6 converts the heating intensity input from the input means 5 into a power signal 6a and sends it to the control circuit 50 of the power supply 30 for driving the magnetron.

  Reference numeral 61 denotes an oven heating means which includes the above-described hot air unit 11 and the hot air motor 13 attached outside the hot air unit 11. The main control means 6 detects the temperature of the heating chamber 17 by the temperature detecting means 16 so that the temperature of the heating chamber 17 becomes the temperature inputted from the input means 5, and adjusts the power of the hot air heater 14.

  Reference numeral 62 denotes a cooling unit that cools a component that may cause a thermal problem due to heat conduction from the self-heating component or the heating component during the heating operation. When the range heating unit 60 is operating, In particular, it cools the magnetron 31 and the power supply 30 for driving the magnetron.

  Reference numeral 6 denotes a main control unit, which operates each heating unit so as to heat and cook the food according to the contents input from the input unit 5, and according to the temperature detected by the temperature detection unit 16, the oven heating unit 61 and the grill heating unit 12. The heater power is adjusted.

  Next, the operation of the magnetron 31 and the power supply 30 for driving the magnetron will be described. FIG. 3 is a control block diagram illustrating the magnetron driving power supply 30, FIG. 5 is a voltage waveform diagram of a main part of the control block diagram, and FIG. 6 is a diagram illustrating pulses for each area.

First, the magnetron driving power supply 30 will be described.
An AC power supply 41 is an AC power supply supplied from a commercial power supply. Reference numeral 42 denotes a rectifier circuit for converting the AC power supplied from the AC power supply 41 into DC.

A power supply smoothing circuit 43 smoothes the power supply rectified by the rectifier circuit 42.
A step-up transformer 46 boosts the voltage applied to the temporary coil to induce a high voltage in the secondary coil.
Reference numeral 44 denotes a switching element which turns on and off a current flowing through a primary coil of the step-up transformer 46 at a high frequency (20 K to 40 KHz).
45 is a resonance capacitor. Due to the resonance capacitor 45 and the inductance of the primary coil of the step-up transformer 46, even after the switching element 44 is turned off from the ON state, an alternating current flows through the primary coil of the step-up transformer 46, and the current flows through the secondary coil of the step-up transformer 46. Induce voltage. Then, the level of the voltage generated on the secondary side is adjusted by adjusting the ratio of the ON / OFF time of the switching element 44.

  The power supply smoothing circuit 43, the switching element 44, the resonance capacitor 45, and the step-up transformer 46 described above constitute an inverter circuit 48.

  Reference numeral 47 denotes a high-voltage circuit that double-rectifies a high-frequency voltage induced in the secondary coil of the step-up transformer 46.

  31 is a magnetron. The electrical configuration includes a cathode 31a (also used as a heater) and an anode 31b. An electric current is applied to the heater 31a to cause the heater to generate heat. When it reaches, the magnetron 31 starts oscillating, radiates high-frequency energy to heat the food in the heating chamber 17.

Next, the control circuit 50 and the control means 53 will be described.
As shown in FIG. 3, the control circuit 50 includes a power supply voltage detection circuit 58, a power supply synchronization timing detection circuit 51, an input current detection circuit 52, a drive circuit 57, an ON timing detection circuit 55a, and control means 53.

  The power supply synchronization timing detection circuit 51 is for detecting the timing at which the voltage Z of the AC power supply 41 (in FIG. 5A, a half cycle of the commercial power supply) periodically changes and the voltage Z becomes zero volt. Things.

  The input current detection circuit 52 detects a current flowing through the power supply smoothing circuit 43 when the magnetron 31 is operating. The current is measured by measuring a voltage generated between both ends of the resistor 52a and calculating from a resistance value of the resistor 52a. The resistor 52a uses a resistor having a small resistance value so that the resistor itself does not consume extra power. Therefore, the voltage generated at both ends of the resistor 52a also becomes a very small value, and the voltage is amplified by the amplifier circuit and output to the control means 53 as a detection value.

  Then, the correlation between the high-frequency output when the magnetron 31 is oscillating and the voltage generated across the resistor 52 a of the input current detection circuit 52 is checked in advance. The control means 53 can recognize whether or not the oscillating output of the magnetron 31 matches the request from the main control means 6 based on the voltage generated across the resistor 52a of the input current detection circuit 52. ing.

  The ON timing detection circuit 55a detects a current flowing through a resonance circuit including the resonance capacitor 45 of the inverter circuit 48 and the primary coil of the step-up transformer 46. Then, when the flow of the electric current stops, the timing at which the switching element 44 is turned on is instructed to the I / O 55 (details will be described later).

  The drive circuit 57 drives the switching element 44 based on the ON data signal output from the I / O 55.

  Next, the control means 53 has a DA converter 53d, a time measuring means 53a, a CPU 54, an I / O 55, a storage means 53b, a DMA 56, and a serial communication means 53c.

  The control means 53 starts operation based on a power signal 6a (details will be described later) sent from the main control means 6.

  The power signal 6a is a signal for transmitting the intensity of heating input from the operation unit 5b to the control circuit 50 by the main control unit 6 and setting the high-frequency output of the magnetron 31. The power signal 6a is input to a serial communication unit 53c (described later) of the control circuit 50.

  The CPU 54 controls various units and the like connected to the CPU 54.

  The timer 53a measures the pulse width U (FIG. 5 (b)) of the pulse signal Q (FIG. 5 (b)) sent from the power supply synchronization timing detection circuit 51, and calculates the midpoint R (FIG. 5) of the pulse width. 5 (b)), the time S of the pulse interval (FIG. 5 (b)) is measured, and the frequency of the connected power supply 41 is determined.

  However, although not shown in FIG. 3, when a zero-cross detection unit is provided, the control unit 53 can detect the timing when the voltage Z becomes zero. Therefore, it is possible to use a zero-crossing detecting means instead of the power supply synchronization timing detecting circuit 51.

  The storage unit 53b stores drive data K for outputting a voltage at which the magnetron 31 can oscillate at the maximum high-frequency output from the magnetron drive power supply 30.

  The drive data K accumulates the number of times to drive the switching element 44 during a half cycle of the commercial power supply. Further, since the driving of the switching element 44 varies depending on the frequency of the AC power supply 41 to be connected, two types, 50 Hz and 60 Hz, are provided when used in Japan. The details of the drive data K will be described later.

  The serial communication unit 53c is connected to the CPU 54 and receives the power signal 6a from the main control unit 6.

  The DMA (direct memory access) 56 transfers the drive data K of the storage unit 53b to the I / O 55 without being affected by the operation speed of the CPU 54 after the instruction of the transfer start by the CPU 54.

  The I / O 55 outputs the drive data K sent from the DMA 56 to the drive circuit 57 as an ON data signal. In accordance with an instruction from the CPU 54, the start data of the drive data K is synchronized with the start of the pulse signal Q from the ON timing detection circuit 55a. The output timing of each drive data K to the drive circuit 57 is synchronized with the input from the ON timing detection circuit 55a.

Next, the drive data K will be described in detail.
The drive data K stored in the storage unit 53b is data for outputting a voltage at which the magnetron 31 can oscillate with the maximum high-frequency output by the magnetron drive power supply 30. Further, when the magnetron 31 is oscillated, the data is used to generate a power supply (FIG. 5E) capable of improving the power factor and the efficiency to the maximum.

  In order to improve the power factor and efficiency, the duty ratio of the magnetron 31 is increased on the left and right A side portions in FIG. In order to increase the duty ratio of the magnetron 31, the ON time of the switching element 44 is lengthened, the induced voltage of the secondary coil of the step-up transformer 46 is quickly increased (maintained), and the heater (cathode) 31a of the magnetron 31 is increased. The data is used to raise the temperature quickly and to start the transmission of the magnetron 31 earlier.

  Further, in order to improve the power supply efficiency, after the voltage of the AC power supply 41 rises sharply from the base of the low sine wave (part B in FIG. 5A), the voltage changes near the peak (see FIG. 5A). In FIG. 5A, the ON time of the switching element 44 is set from just before the top (the latter half of the part B where the voltage is rapidly increasing) so that an unnecessary voltage is not applied to the magnetron 31. By gradually shortening it, the rate of increase in the voltage applied to the magnetron 31 is suppressed.

  In the part C, an excessive voltage (a current suddenly flows when the voltage applied to the magnetron 31 exceeds the oscillation voltage of the magnetron (about 4 kV)) is not applied.

  As the specific drive data K, as shown in FIG. 5C, the drive data K is set for each area N from area 1 where the half cycle (voltage Z) of the AC power supply 41 is finely divided. In this embodiment, the time of a half cycle (voltage Z) of the AC power supply 41 is equally divided into 200 equally divided areas. As the drive data K, one ON time data for turning on the switching element 44 corresponding to each area is assigned, and a total of 200 pieces are provided. This is the same number as the number of ON times when the switching element 44 is turned ON at 20 KHz.

  Further, the ON time as the ON data of the drive data K will be described with reference to FIGS. 5C and 5D. FIG. 5D shows the ON time of the switching element 44 corresponding to each area described above. The ON time of the data G shown in FIG. 5D becomes the maximum, and the ON time of the data E at the peak point D of the voltage Z is the minimum, at the H point on the bottom side of the voltage Z indicating the half cycle of the AC power supply 41. In the data in the meantime, ON time indicating a gradual change is set as shown in the figure. The OFF time is determined by the output of the ON timing detection circuit 55a that indicates the next ON timing after the switching element 44 has been turned OFF from ON, and the OFF time of the ON data signal output from the I / O 55 is substantially the same. .

  Next, the above-mentioned area will be described with reference to FIG. As shown in the figure, the ON data signals output from the I / O 55 in the same area are set so that the same ON data signal is output (in the area 1, the same ON data signal G is output a plurality of times). ing). The once output ON data signal continues the ON data signal even when the area shifts to the next area with the elapsed time, waits for an input from the next ON timing detection circuit 55a, and waits for the next ON data signal. (When the transition from the area 1 to the area 2 occurs, the ON data signal G has already been output, so the ON data signal G continues even after the transition to the area 2 and the ON data signal J is output at the next output. Output).

  In the figure, a plurality of ON data signals are described in the same area for the sake of explanation. However, in this embodiment, the ON data signal is generated at the point H at the bottom of the voltage Z when the ideal AC power supply 41 is used. This is a setting that is output once. However, in the data E at the peak point D of the voltage Z, since the ON time of the ON data signal is shortened, the ON data signal of the same data E is continuously output in the same area. The same ON data signal interrupts without shifting to the next data to generate and output the same ON data signal.

  Next, the operation of the magnetron drive power supply 30 will be described. The start of transmission of the magnetron 31 is started when a power signal 6 a corresponding to a high-frequency output input to start heating is transmitted from the main control unit 6 to the control unit 53.

  The control unit 53 calls the drive data K, which is data of the ratio of the ON time corresponding to the determined frequency, from the storage unit 53b. The signal is output from the DMA 56 to the I / O 55 to generate an ON time data signal (FIG. 5D).

  The control means 53 receives the power signal 6a and calls out the drive data K, which is the ratio of the ON time corresponding to the frequency of the power supply stored in the storage means 53b, from the drive data K stored in the storage means 53b. , And ON time data signal (FIG. 5D). When the product is connected to the power supply, the detection of the frequency of the AC power supply 41 has been completed.

  The ON time data output from the control means 53 according to the detection value from the input current detection circuit 52 so that the high frequency output oscillated by the magnetron 31 corresponding to the power signal 6 a sent from the main control means 6 is obtained. The ON time of the pulse of the signal (FIG. 5D) is changed as follows.

  That is, when the current value detected by the input current detection circuit 52 is small, the voltage supplied to the magnetron 31 is changed so that the current value detected by the input current detection circuit 52 flows in response to the requested high-frequency output. The operation is performed so as to increase the ratio of the ON time of the ON time data signal (FIG. 5D) so as to increase the high frequency output oscillated by the magnetron 31.

  When the detected current is large, the ratio of the ON time of the ON time data signal (FIG. 5D) is reduced so as to reduce the voltage supplied to the magnetron 31, and the high frequency output oscillated by the magnetron 31 is reduced. It works to make it smaller.

  As a result, on the bottom side of the voltage Z applied to the magnetron 31 shown in FIG. 5C, as shown in FIG. 5E, a flat voltage without rising unnecessary peak points is applied as shown in FIG. 5E.

  Next, the operation will be described. To warm the object to be cooked, the object to be cooked (not shown) is placed on the table plate 20 of the heating chamber 17 and the door 2 is closed.

  After the door 2 is closed, the user operates the operation unit 5b to set the high-frequency output, which is the heating intensity, and the heating time with reference to the menu displayed on the display unit 5a of the operation panel 3 provided on the door 2. In addition, warming of automatic heating can also be selected. Then, a heating start button (not shown) of the operation unit 5b is pressed to start heating.

  Next, the case where the high-frequency output is 700 W and the heating time is 1 minute will be described. The main control means 6 sends a power signal 6a to the control means 53 in the inverter board 480 to notify that the input high-frequency output is 700 W to start heating.

  At the same time, the main control means 6 sends a signal to the rotating antenna driving means 23, rotates the rotating antenna 19, sends a signal to the cooling means 62, and starts blowing cooling air.

  The control means 53 receives the power signal 6a, calls out the drive data K corresponding to the frequency of the power supply among the drive data K stored in the storage means 53b, and converts the ON time data signal to the I / O 55. The I / O 55 waits for an output from the ON timing detection circuit 55a, checks the state of the area, and sequentially outputs an ON data signal. The detection of the power supply frequency has been completed when the product is connected to the power supply.

  Immediately after the start of heating, since the heater 31a of the magnetron 31 is not warm, there is no oscillation and much current does not flow. However, at the start of heating, the ON time of the drive data K stored in the storage means 53b is generated and output so that a high voltage, which is the maximum output, is applied to the magnetron 31. Begins to rise (approximately 1 second after the voltage is applied), and a current starts to flow gradually.

  There are a plurality of patterns of drive data K in the storage means 53b. The drive data K is a dedicated pattern at the time of startup, and is thereafter switched to the drive data K of a pattern that can provide a required high-frequency output 700W. Further, the ON time of the ON time data signal (FIG. 5D) is changed while monitoring the current detected by the input current detection circuit 52 so that the high-frequency output 700 W is obtained. However, when the difference is larger than the target current value, the change width is larger, and when the difference is smaller, the change width is smaller. Further, when the current is increased or decreased with respect to the target value, the change in the high-frequency output oscillated by the magnetron 31 is slower when the current is decreased, and therefore, when the current is decreased, it is better to increase the change width. good.

  The heating of the object to be cooked is performed stably by repeating the above-described operation, and after a predetermined heating time of one minute elapses, the main control means 6 issues a stop command to the control means 53 and ends the heating. .

  Next, the relationship between the drive data K, the area, and the ON data signal will be described in more detail.

  The number of drive data K to be stored is the minimum number of ONs necessary for the switching element 44 to be turned ON / OFF in a half cycle of the connected AC power supply 41.

  The drive data K stores ON time data in which the switching element 44 is sequentially turned on from zero volts of the power supply during a half cycle of the AC power supply 41 as an ideal sine wave.

  The output timing of the ON data signal from the I / O 55 is output from the ON timing detection circuit 55a. The output timing is determined by the specifications of the resonance capacitor 45 of the inverter circuit 48 and the primary coil of the step-up transformer 46, and is the same timing (substantially the same OFF time) when the magnetron drive power supply 30 operates.

  In the case where the ON data signal output from the I / O 55 is output a plurality of times in the same area in each area obtained by equally dividing the half cycle time of the AC power supply 41 managed by the CPU 54, An interrupt is issued before the next drive data K, and an ON data signal having the same ON time as the ON data signal is output. Therefore, an ON data signal corresponding to the voltage Z of the AC power supply 41 is output to the switching element 44 by the drive data K provided for each area.

  The reason for using the principle of this area will be described. First, when the AC power supply 41 is always an ideal sine wave and there is no voltage fluctuation, and when there is no individual variation in the input and output of the magnetron, it is considered that there is no problem even if the above-mentioned area principle is not adopted. . However, for example, when the power supply voltage of the AC power supply 41 fluctuates high, the current value detected by the input current detection circuit 52 increases, and the ON time of the drive data K is shortened to reduce the voltage supplied to the magnetron 31. Since the OFF time is constant, the driving data K for the half cycle provided is used up, and the switching element 44 may not be turned on at the end.

  Further, when the power supply voltage is low, the drive data K is left in excess to lengthen the ON time of the drive data K. Furthermore, the ON / OFF timing of the switching element 44 that drives the magnetron 31 does not match the voltage Z that changes with a sine wave of the AC power supply 41 due to the change in the ON time of the drive data K, and the magnetron does not transmit normally. There is. Note that individual variations in the input and output of the magnetron actually exist, and the above phenomenon occurs when the ON time of the drive data K is adjusted according to the current value detected by the input current detection circuit 52 described above. I do.

  However, in this embodiment, when the ON data signal is output a plurality of times in the same area among the areas obtained by dividing the time axis of the half cycle of the AC power supply into a plurality of areas, the plurality of ON data Signal is output at the same ON time). Therefore, when the ON time of the drive data K changes, the number of ON data signals is adjusted over the same area where the ON time has changed or over the next area. Thus, the sine wave of the AC power supply 41 and the ON / OFF timing of the switching element 44 for driving the magnetron 31 are always synchronized, so that the transmission of the magnetron can be normalized.

  The switching element 44 is provided with the same number of drive data K as the minimum ON required for the switching element 44 to be turned ON / OFF. Even when the ON time of the data K changes, the number of ON data signals is adjusted over the same area where the ON time has changed or over the next area. Thus, the sine wave of the AC power supply 41 and the ON / OFF timing of the switching element 44 for driving the magnetron 31 are always synchronized, so that the error on the output side of the magnetron drive power supply 30 can be minimized.

  In addition, the high-frequency heating cooker corrects the temperature rise of the input current detection circuit 52 because the environmental temperature of the power supply 30 for driving the magnetron rises due to the heat generated by the magnetron and the heat generated by the switching element 44 and the step-up transformer 46. This can further increase the accuracy.

  As described above, according to the present embodiment, the magnetron, the rectifier circuit connected to the AC power supply to convert the power supply to DC, the inverter circuit connected to the rectifier circuit to drive the magnetron, and the inverter circuit A drive circuit that drives a switching element, an input current detection circuit that detects a current flowing through the inverter circuit, an ON timing detection circuit that outputs an ON timing of a switching element of the inverter circuit, and a detection result of the input current detection circuit Control means for controlling a switching element of the inverter circuit based on the control signal, wherein the control means includes an area obtained by dividing a time axis of a half cycle of the AC power supply into a plurality of areas, and the switching corresponding to the area. It has drive data of ON time necessary to turn on the element.

  Thereby, when the magnetron 31 is transmitted with a specific output after the product is assembled, the adjustment value which is read by the control means and is changed by the input current detection circuit 52 is completed by one adjustment. As a result, the adjustment time can be reduced.

  The control means may output the ON data signal a plurality of times in the same area among a plurality of areas obtained by dividing a time axis of a half cycle of the AC power supply into a plurality of areas. Output at ON time. Accordingly, when the ON time of the drive data changes, the number of ON data signals is adjusted over the same area where the ON time has changed or over the next area. Therefore, the switching element that drives the sine wave of the AC power supply and the magnetron ON / OFF timing is always synchronized, so that the transmission of the magnetron can be normalized.

  Further, the control of the switching element 44 does not require the use of an analog circuit by the CPU 54, the storage means 53b, the I / O 55 and the DMA 56, so that the number of components can be reduced and the size of the printed circuit board to be mounted can be reduced. In addition, costs can be reduced.

Reference Signs List 30 power supply for magnetron drive 31 magnetron 41 AC power supply 42 rectifier circuit 44 switching element 48 inverter circuit 50 control circuit 51 power supply synchronization timing detection circuit 52 input current detection circuit 53 control means 53b storage means 54 CPU
55 I / O
56 DMA
57 Drive circuit K Drive data

Claims (1)

A magnetron,
A rectifier circuit connected to an AC power supply to convert the power supply to DC;
An inverter circuit connected to the rectifier circuit and driving the magnetron;
A drive circuit for driving a switching element of the inverter circuit;
An input current detection circuit that detects a current flowing through the inverter circuit;
An ON timing detection circuit that outputs an ON timing of a switching element of the inverter circuit;
Control means for controlling a switching element of the inverter circuit based on a detection result of the input current detection circuit,
The control means includes:
Storage means for storing driving data of ON time required to ON the switching element corresponding to an area divided into a plurality of time axes of the half cycle of the AC power source,
Has direct access memory,
The drive data is different depending on the frequency of the AC power supply,
The drive data has the same ON time in each of the areas, and the ON time for each of the areas is configured to decrease from zero to a peak of the AC power supply voltage,
The drive data is stored differently according to the detection current of the input current detection circuit,
The high frequency heating cooker, wherein the direct access memory transfers the drive data stored in the storage unit to the drive circuit as a drive signal for the switching element via an I / O.

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