JP2008091295A - Induction heating rice cooker - Google Patents

Abstract

In an induction heating rice cooker configured to supply power to an inverter circuit from a rectifier having a high-frequency smoothing capacitor, when the high-frequency smoothing capacitor has a certain capacitance or less, the rice cooking operation is stopped and the minimum required capacity is achieved. Make it possible to use a high-frequency smoothing capacitor.
An inverter circuit 5 supplies high-frequency power to a heating coil 2 that heats a pan 1, and an rectifier 7 that rectifies an AC power source 6, a choke coil 9 and a high-frequency smoothing capacitor 10 are used to invert the inverter. Electric power is supplied to the means 5, the inverter circuit 5 is controlled by the control means 17, and the capacitance of the high-frequency smoothing capacitor 10 is detected by the capacitance detection means 19. The control unit 17 is configured to input the signal from the electrostatic capacitance detection unit 19 and prohibit the operation of the inverter circuit 5 when detecting that the electrostatic capacitance of the high-frequency smoothing capacitor 10 has become below a certain level.
[Selection] Figure 1

Description

  The present invention relates to an induction heating rice cooker configured to supply power to an inverter circuit from a rectifier having a high-frequency smoothing capacitor.

  Conventionally, this type of rice cooker has a heating coil for heating a pan, an inverter circuit for supplying a high-frequency current to the heating coil, a switching means constituting the inverter circuit, and a peak voltage for detecting a voltage across the switching means. Rectifying means that is composed of a detection means, a rectifying element that rectifies an AC power supply, a choke coil, and a high-frequency smoothing capacitor, and that supplies power to the inverter circuit, and an input current detection that detects an input current supplied from the AC power supply to the rice cooker The on-time of the switching means is shortened and the input current is controlled in accordance with the higher output of the output of the voltage detection means and the output of the current detection means (for example, Patent Documents) 1 and 2).

  FIG. 7 shows a conventional rice cooker described in Patent Document 1. As shown in FIG. Hereinafter, the configuration will be described.

  As shown in FIG. 7, the pan 1 is heated by the heating coil 2, and the heating coil 2 and the resonance capacitor 3 constitute a parallel resonance circuit, and the inverter circuit 5 is composed of switching means 4 capable of high-frequency switching. It is composed. The peak voltage detecting means 61 detects the voltage across the switching means 4. The rectifying means 7 includes a rectifying element 8 that rectifies the AC power supply 6, a choke coil 9, and a high-frequency smoothing capacitor 10. The input current detecting means 11 detects an input current, and according to the output values of the input current detecting means 11 and the peak voltage detecting means 61, the on-time of the switching means 4 is set by the control means 62 constituted by a microcomputer or the like. It is configured to control.

  Here, the choke coil 9 has a function of preventing the high frequency current component of the inverter circuit 5 from leaking as high frequency noise to the AC power supply 6 side.

In such a configuration, the high-frequency smoothing capacitor 10 has a function of supplying a high-frequency current that flows through the heating coil 2 when the switching means 4 of the inverter circuit 5 is energized.
Japanese Examined Patent Publication No. 61-26306 Japanese Patent Laid-Open No. 5-114472

  However, in such a conventional configuration, unless the electrostatic capacity of the high-frequency smoothing capacitor 10 is equal to or greater than a predetermined capacity, it is not possible to maintain energy sufficient to stably supply the high-frequency current supplied to the heating coil 2. A ripple voltage having the same frequency component as the oscillation frequency of the inverter circuit 5 is generated in the voltage at both ends of the inverter 10, and the fluctuation range of the ripple voltage is increased, and the high frequency noise leaking to the AC power supply 6 through the choke coil 9 is increased. Had a problem. Furthermore, the self-heating of the high frequency smoothing capacitor 10 itself has a problem of increasing.

  The high-frequency smoothing capacitor 10 used in such applications generally deteriorates due to long-term use or temperature rise, and the capacitance decreases. Therefore, even if it decreases, the high-frequency leakage noise is kept below a certain level. There was a problem that a high-frequency smoothing capacitor having a size capable of keeping the increase value below a certain level had to be mounted.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and aims to enable the use of a high-frequency smoothing capacitor having a minimum necessary capacity by stopping the rice cooking operation when the electrostatic capacity of the high-frequency smoothing capacitor falls below a certain level. It is said.

  In order to achieve the above object, the present invention provides an inverter means comprising a rectifier comprising a rectifier for rectifying an AC power source, a choke coil and a high-frequency smoothing capacitor, supplying high-frequency power to a heating coil for heating a pan by an inverter circuit. The inverter circuit is controlled by the control means, and the capacitance of the high frequency smoothing capacitor is detected by the capacitance detection means. The control means inputs a signal from the capacitance detection means. When the capacitance of the high frequency smoothing capacitor is detected to be below a certain level, the operation of the inverter circuit is prohibited.

  Thereby, when the electrostatic capacitance of a high frequency smoothing capacitor falls, the compact induction heating type rice cooker which can use the high frequency smoothing capacitor of the minimum required capacity | capacitance can be provided by prohibiting the heating operation of a rice cooker. .

  The induction heating type rice cooker of the present invention can use the high frequency smoothing capacitor with the minimum required capacity by stopping the rice cooking operation when the capacitance of the high frequency smoothing capacitor is below a certain level, and the induction of a compact shape It can be set as a heating rice cooker.

  A first invention is a heating coil for heating a pan, an inverter circuit for supplying high-frequency power to the heating coil, a control means for controlling the inverter circuit, a rectifying element for rectifying an AC power source, a choke coil, and a high-frequency smoothing A rectifying means configured to supply power to the inverter means, and a capacitance detecting means for detecting a capacitance of the high frequency smoothing capacitor, wherein the control means is a signal from the capacitance detecting means. Is input, and when the capacitance of the high-frequency smoothing capacitor is detected to be below a certain level, the operation of the inverter circuit is prohibited. By stopping the rice cooking operation at the same time, a high frequency smoothing capacitor with the minimum required capacity can be used, and the induction heating type cooking with a compact shape can be used. It can be a vessel. Further, it is possible to prevent the high-frequency smoothing capacitor from decreasing in electrostatic capacity, increasing high-frequency leakage noise leaking to the AC power supply, and increasing the self-heating of the high-frequency smoothing capacitor.

  In a second aspect based on the first aspect, the capacitance detecting means detects a ripple voltage having the same frequency component as the oscillation frequency of the inverter circuit generated at the voltage across the high-frequency smoothing capacitor. The operation of the inverter circuit is prohibited when the fluctuation value of the ripple voltage detected by the capacitance detecting means exceeds a certain value, and high frequency noise leaking to the commercial power supply due to a decrease in the capacitance of the high frequency smoothing capacitor is generated. By stopping the rice cooking operation before it becomes larger than a certain level, a high-frequency smoothing capacitor having the minimum necessary capacity can be used, and a compact-shaped induction heating rice cooker can be obtained.

  In a third aspect based on the first aspect, the capacitance detecting means detects a minimum voltage of a ripple voltage generated at a voltage across the high-frequency smoothing capacitor in a state where the inverter circuit is operating with a constant power consumption. The control means prohibits the operation of the inverter circuit when the minimum voltage detected by the capacitance detection means is below a certain level, before the capacitance of the high frequency smoothing capacitor becomes below a certain level. In addition, by stopping the rice cooking operation, a high-frequency smoothing capacitor having the minimum required capacity can be used, and a compact induction heating rice cooker can be obtained.

  4th invention is provided with the display means which displays the state of a rice cooker in any one of said 1st-3rd invention, and a control means prohibits operation | movement of an inverter circuit with the signal from an electrostatic capacitance detection means. Then, the display means displays that the high-frequency smoothing capacitor is abnormal, and the user can be informed that the rice cooker cannot be used because the capacitance of the high-frequency smoothing capacitor has decreased. .

  According to a fifth aspect of the present invention, there is provided a heating coil for heating a pan, an inverter circuit for supplying high-frequency power to the heating coil, a control means for controlling the inverter circuit, a rectifying element for rectifying an AC power source, a choke coil, and a high-frequency smoothing A rectifying means configured to supply power to the inverter means and a temperature detecting means for detecting the temperature of the high-frequency smoothing capacitor, and the control means inputs a signal from the temperature detecting means, and It is configured to prohibit the operation of the inverter circuit when it detects that the temperature of the smoothing capacitor has exceeded a certain level, and before the self-heating increases due to the capacitance of the high-frequency smoothing capacitor becoming below a certain level. By stopping the rice cooking operation, it is possible to use a high-frequency smoothing capacitor with the minimum required capacity, and to introduce a compact shape. It can be heated cooker.

  6th invention is provided with the display means which displays the state of a rice cooker in the said 5th invention, and a control means detects the said high frequency smoothing on a display means, if it detects that the temperature of a high frequency smoothing capacitor became more than fixed level. The fact that the capacitor is abnormal is displayed, and it is possible to inform the user that the rice cooker cannot be used because the capacitance of the high-frequency smoothing capacitor has decreased.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a system configuration diagram of main parts of an induction heating rice cooker according to Embodiment 1 of the present invention.

  As shown in FIG. 1, although not shown in particular, the pan 1 is composed of a laminated body using a plurality of metals that pass magnetic flux, and shows an equivalent circuit. The heating coil 2 is magnetically coupled to the pan 1, and the heating coil 2 is composed of a wire in which a plurality of litz wires bundled with a plurality of copper wires are further twisted, and the current when a high-frequency current flows. The distribution is uniform. The resonance capacitor 3 is connected in parallel to the heating coil 2 and constitutes a parallel resonance circuit with the heating coil 2. In the present embodiment, a polypropylene capacitor having a small loss even when a high-frequency current flows is used.

  The switching means 4 includes a semiconductor element such as a MOSFET or IGBT and a reverse connection diode connected in reverse to the semiconductor element. MOSFETs and IGBTs have a high withstand voltage, can switch at high frequencies, and have an advantage that a large current can flow. The inverter circuit 5 supplies high frequency power to the heating coil 2, and includes the heating coil 2, a resonance capacitor 3, and switching means 4.

  The AC power supply 6 supplies power to the rice cooker, and the power supply frequency of the AC power supply 6 is 50 Hz in the eastern Japan region and 60 Hz in the western Japan region.

  The rectifying means 7 supplies electric power to the inverter circuit 5 and includes a diode bridge 8 that is a rectifying element, a choke coil 9, and a high-frequency smoothing capacitor 10. Here, the capacity of the high-frequency smoothing capacitor 10 is as small as several μF, and when a high-frequency current is passed through the heating coil 2, a ripple occurs in the voltage across the high-frequency smoothing capacitor 10. In the present embodiment, this ripple voltage is substantially the same as the pulsating voltage obtained by full-wave rectification of the AC power supply 6. Further, in order to supply a high frequency current to the heating coil 2, a ripple voltage having the same frequency component as the oscillation frequency of the inverter circuit 5 is superimposed on the pulsating current obtained by full-wave rectification of the AC power supply 6. The The choke coil 9 prevents the high-frequency current component of the inverter circuit 5 from leaking to the AC power source 6 as high-frequency noise.

  The input current detection means 11 includes a current transformer 12, a resistor 13, a diode bridge 14, and an electrolytic capacitor 15. An AC signal from the current transformer 12 is converted into a DC signal by a rectifying / smoothing circuit including the diode bridge 14 and the electrolytic capacitor 15. Has been converted. The resistor 13 is for adjusting the output voltage value of the current transformer 12.

  The input current setting means 16 stores in advance an 8-bit set value corresponding to a plurality of input current target values in a ROM inside the microcomputer, and sets a predetermined value for each condition such as the rice cooking process and the size of the pot 1. An 8-bit set value corresponding to the target value is output.

  The control means 17 controls the inverter circuit 5 and is composed of an AD converter, a PWM generator or the like inside the microcomputer, receives the output voltage of the input current detection means 11 by the AD converter, and the AD converter The high pulse width of the PWM generator is controlled so that the output value and the set value of the input current setting means 16 are the same.

  The driving means 18 is constituted by a push-pull circuit composed of an NPN transistor and a PNP transistor, and outputs a high voltage to the IGBT constituting the switching means 4 when the control means 17 outputs a high pulse. While the high voltage is applied to the switching means 4, the switching means 4 is in a conductive state, and the energy charged in the high frequency smoothing capacitor 10 is supplied to the heating coil 2 as a high frequency current.

  The electrostatic capacitance detection means 19 detects the electrostatic capacitance of the high-frequency smoothing capacitor 10 and divides the voltage across the high-frequency smoothing capacitor 10 by a series circuit of the resistor 20, the resistor 21 and the resistor 22. The voltage across the resistor 22 is output to the control means 17 in parallel with the resistor 21.

  Moreover, the display means 24 is comprised with a liquid crystal display element, and displays the state of a rice cooker with the signal from the control means 17. FIG.

  Here, the control means 17 is configured to input the signal from the electrostatic capacity detection means 19 and prohibit the operation of the inverter circuit 5 when detecting that the electrostatic capacity of the high-frequency smoothing capacitor 10 is below a certain level. ing.

  FIG. 2 is an operation waveform diagram in synchronization with the AC power supply 6 of the voltage applied to the switching means 4, the energization current, and the voltage across the high-frequency smoothing capacitor 10 when the inverter circuit 5 outputs 1200 W. In FIG. 2, VIN is a voltage waveform of the AC power source 6, VC 2 is a voltage waveform at both ends of the high frequency smoothing capacitor 10, IC is an energization current waveform of the switching means 4, and VCE is a voltage waveform at both ends of the switching means 4. The energization current IC is a high-frequency current that is energized to the heating coil 2 using the energy charged in the high-frequency smoothing capacitor 10 as a power source. As shown in FIG. 2, the voltage waveform across the high-frequency smoothing capacitor 10 is substantially the same as the pulsating voltage obtained by full-wave rectification of the AC power supply 6.

  FIG. 3 is a waveform diagram in which the waveform around the peak of the applied voltage of the switching means 4 in the operation waveform shown in FIG. 2 is enlarged to the high frequency operation level. As shown in FIG. 3, while the driving unit 18 outputs a high voltage to the switching unit 4, the switching unit 4 is in a conductive state, and a high-frequency current is supplied from the high-frequency smoothing capacitor 10 to the heating coil 2. At this time, if the electrostatic capacitance of the high frequency smoothing capacitor 10 is not sufficiently large, the applied voltage cannot be maintained, and the voltage drops and ripples are generated.

  Thereafter, while the driving unit 18 outputs a low voltage to the switching unit 4, the switching unit 4 is in a non-conductive state, and the high-frequency smoothing capacitor 10 is charged from the AC power supply 6. At this time, a resonance voltage between the heating coil 2 and the resonance capacitor 3 is applied to the switching means 4. By repeating this, a voltage waveform in which a ripple voltage ΔV having the same frequency component as the oscillation frequency of the inverter circuit 5 is superimposed on a pulsating current obtained by full-wave rectification of the AC power supply 6 is applied to both ends of the high-frequency smoothing capacitor 10. The ripple voltage ΔV increases as the capacitance of the high-frequency smoothing capacitor 10 decreases.

  The operation and action of the above configuration will be described. First, when the rice cooking operation is started, the control means 17 outputs a drive signal to the drive means 18 to operate the inverter circuit 5. At this time, the capacitance detecting means 19 divides the voltage across the high-frequency smoothing capacitor 10 by the resistor 20, the resistor 21 and the resistor 22, and outputs the voltage across the resistor 22 to the control means 17.

  The capacitor 23 connected in parallel to the resistor 21 has a function of not applying the ripple voltage ΔV synchronized with the high frequency current to the resistor 21. That is, the ripple voltage ΔV is divided only by the resistors 20 and 22. Therefore, as the ripple voltage ΔV increases, the output voltage output from the capacitance detection means 19 also increases.

  When the control unit 17 detects that the output voltage output from the capacitance detection unit 19 is equal to or greater than a certain level, the control unit 17 determines that the capacitance of the high-frequency smoothing capacitor 10 has decreased and stops the operation of the inverter circuit 5. . At the same time, the display means 24 displays that rice cooking has been stopped and that the cause is a decrease in the capacitance of the high-frequency smoothing capacitor 10.

  As described above, in the present embodiment, the capacitance detection means 19 detects the ripple voltage ΔV having the same frequency component as the oscillation frequency of the inverter circuit 5 generated at the voltage across the high-frequency smoothing capacitor 10. Since the operation of the inverter circuit 5 is stopped by detecting that the capacitance of the high-frequency smoothing capacitor 10 has decreased, the rice cooked before the high-frequency noise leaking to the commercial power source increases by a certain level due to the decrease in the capacitance of the high-frequency smoothing capacitor 10. By stopping the operation, it is possible to provide an induction heating rice cooker that can use the high-frequency smoothing capacitor 10 having the minimum necessary capacity.

  Further, when the operation of the inverter circuit 5 is prohibited by a signal from the capacitance detection means 19, the display means 24 displays that the high-frequency smoothing capacitor 10 is abnormal, so that the electrostatic of the high-frequency smoothing capacitor 10 is displayed to the user. It can alert | report that the induction heating type rice cooker cannot be used because the capacity | capacitance fell.

  In the present embodiment, the display means is constituted by a liquid crystal display element, but may be displayed by lighting or blinking using an LED.

(Embodiment 2)
FIG. 4 is a system configuration diagram of the main part of the induction heating rice cooker according to Embodiment 3 of the present invention.

  As shown in FIG. 4, the capacitance detecting means 31 detects the capacitance of the high-frequency smoothing capacitor 10 and divides the voltage across the high-frequency smoothing capacitor 10 by a series circuit of a resistor 32 and a resistor 33. The divided voltage is output to the control means 17 so that the lowest voltage of the ripple voltage generated at the both-ends voltage of the high-frequency smoothing capacitor 10 is detected in a state where the inverter circuit 5 is operating with constant power consumption. Yes. Other configurations are the same as those of the first embodiment, and the same reference numerals are given and description thereof is omitted.

  FIG. 5 is an operation waveform diagram in which the voltage applied to the switching means 4, the energization current, and the voltage across the high-frequency smoothing capacitor 10 are synchronized with the AC power supply 6 during the operation in which the inverter circuit 5 outputs 100 W. In FIG. 5, VIN is a voltage waveform of the AC power source 6, VC 2 is a voltage waveform at both ends of the high-frequency smoothing capacitor 10, IC is an energization current waveform of the switching means 4, and VCE is a voltage waveform at both ends of the switching means 4. The energization current IC is a high-frequency current that is energized to the heating coil 2 using the energy charged in the high-frequency smoothing capacitor 10 as a power source.

  As shown in FIG. 5, the voltage waveform at both ends of the high-frequency smoothing capacitor 10 becomes a smoothing voltage having a ripple component obtained by full-wave rectifying and smoothing the AC power supply 6.

  Here, the capacity of the high-frequency smoothing capacitor 10 is as small as several μF, and when a high-frequency current is passed through the heating coil 2, a ripple occurs in the voltage across the high-frequency smoothing capacitor 10.

  When the power consumption of the inverter circuit 5 is about 1200 W, the high-frequency smoothing capacitor 10 cannot hold energy for smoothing the voltage obtained by full-wave rectifying the AC power supply 6 using the diode bridge 8 as illustrated in FIG. This ripple voltage is substantially the same as the pulsating voltage obtained by full-wave rectification of the AC power supply 6, and when the AC voltage is 0V, the voltage across the high-frequency smoothing capacitor 10 is also approximately 0V.

  However, if the power consumption of the inverter circuit 5 is only about 100 W, the high frequency smoothing capacitor 10 only smoothes the voltage obtained by full-wave rectification of the AC power supply 6 using the diode bridge 8 that is a rectifying element to some extent, as shown in FIG. Therefore, even if the AC voltage is 0 V, the voltage across the high-frequency smoothing capacitor 10 can maintain a constant voltage VL. The lower limit value VL of the holding voltage at this time becomes smaller as the capacitance of the high-frequency smoothing capacitor 10 is smaller.

  The operation and action of the above configuration will be described. First, when the rice cooking operation is started, the control means 17 outputs a drive signal to the drive means 18 to operate the inverter circuit 5. At this time, the capacitance detection means 31 divides the voltage across the high-frequency smoothing capacitor 10 by the resistor 32 and the resistor 33, and outputs the voltage across the resistor 33 to the control means 17. Therefore, when the lower limit value VL of the holding voltage is reduced, the output voltage output from the capacitance detection means 19 is also reduced.

  At the start of rice cooking, the control means 17 first controls the inverter circuit 5 to be heated for about 10 seconds so that the power consumption is about 100 W. When it is detected that the output voltage output from the capacitance detection means 31 is below a certain level during the 100 W output, it is determined that the capacitance of the high-frequency smoothing capacitor 10 has decreased, and the operation of the inverter circuit 5 is stopped. Let At the same time, the display means 24 displays that rice cooking has been stopped and that the cause is a decrease in the capacitance of the high-frequency smoothing capacitor 10.

  As described above, in the present embodiment, the capacitance detecting unit 31 detects the lower limit value VL of the ripple voltage generated at the voltage across the high-frequency smoothing capacitor 10, so that the capacitance of the high-frequency smoothing capacitor 10 is increased. Since the operation of the inverter circuit 5 is stopped by detecting the reduction, the minimum required by stopping the rice cooking operation before the high frequency noise leaking to the commercial power source becomes larger than a certain level due to the decrease in the capacitance of the high frequency smoothing capacitor 10 It is possible to provide an induction heating rice cooker that can use a high-frequency smoothing capacitor having a large capacity.

(Embodiment 3)
FIG. 6 is a system configuration diagram of main parts of the induction heating rice cooker according to Embodiment 3 of the present invention.

  As shown in FIG. 6, the temperature detecting means 41 detects the temperature of the high-frequency smoothing capacitor 10 and is arranged in close contact so as to detect the surface temperature of the high-frequency smoothing capacitor 10, and the detected high-frequency smoothing capacitor 10 surface temperatures are output to the control means 17. The fan motor 42 cools the inverter circuit 5 and the rectifying means 7. Other configurations are the same as those of the first embodiment, and the same reference numerals are given and description thereof is omitted.

  The operation and action of the above configuration will be described. First, the control means 17 will output a drive signal to the drive means 18, if it starts rice cooking operation, will operate the inverter circuit 5, and will operate the fan motor 42 simultaneously. And the output signal from the temperature detection means 41 is input. At this time, while the driving unit 18 outputs a high voltage to the switching unit 4, the switching unit 4 is in a conducting state, and a high-frequency current is supplied from the high-frequency smoothing capacitor 10 to the heating coil 2. At this time, if the electrostatic capacitance of the high frequency smoothing capacitor 10 is not sufficiently large, the applied voltage cannot be maintained, and the voltage drops and ripples are generated.

  Thereafter, while the driving means 18 outputs a low voltage to the switching means 4, the switching means 4 becomes non-conductive and the high frequency smoothing capacitor 10 is charged from the AC power supply 6. At this time, a resonance voltage between the heating coil 2 and the resonance capacitor 3 is applied to the switching means 4.

  By repeating this, a voltage waveform in which a ripple voltage ΔV having the same frequency component as the oscillation frequency of the inverter circuit 5 is superimposed on a pulsating current obtained by full-wave rectification of the AC power supply 6 is applied to both ends of the high-frequency smoothing capacitor 10. The ripple voltage ΔV increases as the capacitance of the high-frequency smoothing capacitor 10 decreases. As the ripple voltage ΔV increases, the charge / discharge current of the high-frequency smoothing capacitor 10 increases, and the internal impedance of the high-frequency smoothing capacitor 10 increases, so that the self loss increases.

  The fan motor 42 is cooled so that the high-frequency smoothing capacitor 10 has a capacitance equal to or higher than a predetermined value so that the temperature of the high-frequency smoothing capacitor 10 is equal to or lower than the operation guarantee temperature. In such a cooling state, when the capacitance of the high-frequency smoothing capacitor 10 decreases below a certain level, the self-loss increases and self-heating increases, and the temperature of the high-frequency smoothing capacitor 10 increases. Then, the temperature detection means 41 outputs the increased surface temperature of the high-frequency smoothing capacitor 10 to the control means 17.

  When the control unit 17 detects that the detected temperature output from the temperature detection unit 41 is equal to or higher than a certain level, the control unit 17 stops the operation of the inverter circuit 5. At the same time, the fact that the rice cooking has been stopped in the liquid crystal display element constituting the display means 24 and that the cause is a decrease in the capacitance of the high-frequency smoothing capacitor 10 are displayed.

  As described above, in the present embodiment, the temperature detection means 41 detects the surface temperature of the high-frequency smoothing capacitor 10 to detect that the capacitance of the high-frequency smoothing capacitor 10 has decreased and the inverter circuit 5 Since the operation is stopped, the rice cooking operation is stopped before the high frequency noise leaking to the commercial power supply increases by a certain level or more due to the decrease in the capacitance of the high frequency smoothing capacitor 10, so that the induction that can use the high frequency smoothing capacitor 10 with the minimum necessary capacity is used. A heating rice cooker can be provided.

  Further, when the operation of the inverter circuit is prohibited by a signal from the temperature detecting means 41, the display means 24 displays that the high frequency smoothing capacitor 10 is abnormal, so that the capacitance of the high frequency smoothing capacitor 10 is reduced to the user. By doing, it can alert | report that the induction heating type rice cooker cannot be used.

  In the present embodiment, the display means 24 is constituted by a liquid crystal display element, but may be displayed by lighting or blinking using an LED.

  As described above, the induction heating type rice cooker according to the present invention can use the high-frequency smoothing capacitor having the minimum necessary capacity by stopping the rice-cooking operation when the capacitance of the high-frequency smoothing capacitor becomes below a certain level. Since it can be set as an induction heating rice cooker having a compact shape, it is useful as an induction heating rice cooker configured to supply power to the inverter circuit from the rectifying means having a high frequency smoothing capacitor.

Main part system block diagram of the induction heating type rice cooker in Embodiment 1 of this invention Operation waveform diagram of each part synchronized with AC power supply during 1200W output operation of the same induction heating rice cooker Operation waveform diagram of each part in which the vicinity of the switching means applied voltage peak at the time of 1200 W output operation of the induction heating rice cooker is enlarged. Main part system block diagram of the induction heating type rice cooker in Embodiment 2 of this invention Operation waveform diagram of each part synchronized with AC power supply during 100W output operation of the same induction heating rice cooker Main part system block diagram of the induction heating type rice cooker in Embodiment 3 of this invention Main system configuration diagram of a conventional induction heating rice cooker

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pan 2 Heating coil 5 Inverter circuit 6 AC power supply 7 Rectification means 8 Rectification element 9 Choke coil 10 High frequency smoothing capacitor 17 Control means 19 Capacitance detection means

Claims (6)

A heating coil that heats the pan, an inverter circuit that supplies high-frequency power to the heating coil, a control means that controls the inverter circuit, a rectifying element that rectifies an AC power source, a choke coil, and a high-frequency smoothing capacitor, Rectifying means for supplying power to the inverter means and capacitance detecting means for detecting the capacitance of the high-frequency smoothing capacitor, the control means inputs a signal from the capacitance detecting means, and the high frequency An induction heating rice cooker configured to prohibit the operation of the inverter circuit when detecting that the capacitance of the smoothing capacitor has become below a certain level. The capacitance detection means detects a ripple voltage having the same frequency component as the oscillation frequency of the inverter circuit generated at the voltage across the high-frequency smoothing capacitor, and the control means detects the fluctuation value of the ripple voltage detected by the capacitance detection means. 2. The induction heating rice cooker according to claim 1, wherein the operation of the inverter circuit is prohibited when the value exceeds a certain value. Capacitance detection means detects the lowest voltage of the ripple voltage generated at the voltage across the high-frequency smoothing capacitor in a state where the inverter circuit is operating with constant power consumption. The induction heating type rice cooker according to claim 1, wherein the operation of the inverter circuit is prohibited when the detected minimum voltage is below a certain level. A display means for displaying the state of the rice cooker is provided, and the control means displays on the display means that the high-frequency smoothing capacitor is abnormal when the operation of the inverter circuit is prohibited by a signal from the capacitance detection means. The induction heating type rice cooker of any one of Claims 1-3. A heating coil that heats the pan, an inverter circuit that supplies high-frequency power to the heating coil, a control means that controls the inverter circuit, a rectifying element that rectifies an AC power source, a choke coil, and a high-frequency smoothing capacitor, Rectifying means for supplying power to the inverter means and temperature detecting means for detecting the temperature of the high frequency smoothing capacitor are provided, and the control means inputs a signal from the temperature detecting means, and the temperature of the high frequency smoothing capacitor is constant. An induction heating rice cooker configured to prohibit the operation of the inverter circuit upon detecting the above. A display means for displaying the state of the rice cooker is provided, and the control means displays on the display means that the high-frequency smoothing capacitor is abnormal when detecting that the temperature of the high-frequency smoothing capacitor exceeds a certain level. Item 6. The induction heating rice cooker according to item 5.

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