JP4961844B2 - Induction heating rice cooker - Google Patents

Description

  The present invention relates to an induction heating rice cooker having a voice notification function.

Conventionally, some rice cookers having a voice notification function reduce power consumption and prevent speaker noise by supplying power to a voice output unit including a voice synthesizer only for a specific period (for example, , See Patent Document 1).
JP 59-4828

  However, when an induction heating rice cooker is to be realized with the above-described conventional configuration, when a high-frequency current is flowing through the heating coil, a high-frequency magnetic field from the heating coil propagates to the winding of the speaker, and the winding of the speaker When an induced electromotive voltage is generated and the power of the audio output means is turned off, the induced electromotive voltage exceeds the maximum voltage rating of the audio output means, and the audio output means is destroyed. When the power of the audio output means is on, the output terminal of the audio output means becomes an intermediate potential of the power supply or is fixed to high or low, so that an induced electromotive voltage is generated in the speaker winding. However, since the maximum voltage rating of the sound output means is not exceeded, it is necessary to keep the sound output means turned on in order to prevent the sound output means from being broken by the induced electromotive voltage of the speaker. In this case, power is consumed even when no sound is output, and power cannot be saved, and noise noise is generated from the speaker due to a high-frequency magnetic field generated when a high-frequency current flows through the heating coil. Will have.

  In addition, in order to reduce the induced electromotive voltage generated in the winding of the speaker, it is necessary to sufficiently separate the speaker from the heating coil, so that the speaker cannot be arranged in the vicinity of the heating coil having a sufficient space for the arrangement. There was a problem that it was difficult to downsize the equipment.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and aims to prevent sound output means from being broken even if a speaker is arranged in the vicinity of a heating coil, and to realize a safe, compact and energy saving. Yes.

In order to achieve the above object, the present invention inductively heats a pan with a heating coil supplied with a high-frequency current from an inverter circuit, controls the inverter circuit with control means, receives the output of the control means, and receives voice from the voice output means. configured to output a signal to the speaker, when the high-frequency current flows through the heating coil, having an induced electromotive voltage protection means for reducing the induced electromotive force generated in the loudspeaker to the signal path of the speaker and the audio output unit, a speaker Is placed in the vicinity of the heating coil, and when the control means does not output sound, the power supply of the sound output means is stopped, and the induction occurs in the speaker even if the power supply of the sound output means is stopped during the heating coil operation. It is configured to reduce power .

  Thereby, the induced electromotive voltage generated in the winding of the speaker can be reduced by the induced electromotive voltage protection means, and the induced electromotive voltage does not exceed the maximum voltage rating of the audio output means even when the power of the audio output means is off, A safe, compact, energy-saving rice cooker that is easy to understand, such as operation, can be provided.

  The induction heating type rice cooker of the present invention can prevent the sound output means from being destroyed even if an induction electromotive voltage is generated in the speaker by the magnetic field of the heating coil when the power supply of the sound output means is stopped.

According to a first aspect of the present invention, there is provided a heating coil for induction heating of a pan, an inverter circuit for supplying a high frequency current to the heating coil, a control means for controlling the inverter circuit, a speaker, and an audio signal received from the control means. Voice output means for outputting a signal to the speaker, and when high frequency current flows through the heating coil, an induction voltage for reducing an induced voltage generated in the speaker in a signal path between the speaker and the voice output means. Voltage protection means, the speaker is disposed in the vicinity of the heating coil, and when the control means does not output sound, the power supply of the sound output means is stopped and the sound output means is activated during operation of the heating coil. stopping power supply is obtained by configured for reducing the induced electromotive force generated in the loudspeaker, induced electromotive voltage generated in the windings of the speaker It can be reduced by the induced electromotive voltage protection means, and the induced electromotive voltage exceeds the maximum voltage rating of the output terminal of the audio output means even when the power of the audio output means is off, and the protection provided on this output terminal It is possible to prevent current from flowing into the sound output means through the diode, and to prevent the sound output means from being destroyed. Further, since the power of the sound output means is turned off when no sound is output, even when a high frequency current flows through the heating coil and a high frequency magnetic field is generated, a noise waveform due to this high frequency magnetic field is superimposed on the sound output means, and the speaker No noise noise. Therefore, it is possible to provide a rice cooker that is safe, compact, energy-saving, and easy to understand such as operation.

  In a second aspect based on the first aspect, the induced electromotive voltage protection means comprises a resistor connected between the signal path of the speaker and the sound output means and the ground potential, and is generated in the winding of the speaker. The induced electromotive voltage can be consumed by the resistor, and the induced electromotive voltage of the speaker can be reduced. Furthermore, in order to reduce this induced electromotive voltage, a current flows through the winding and resistor of the speaker. Since this current can also be limited by the resistance, heat generation of the speaker winding can also be suppressed. Therefore, since the heat generation of the speaker is small and the induced electromotive voltage can be reduced with an inexpensive component such as a resistor, a low-cost and highly reliable rice cooker can be provided.

According to a third invention, in the first invention, the induced electromotive voltage protection means is connected so as to be reverse-biased between the signal path of the speaker and the sound output means and the high potential of the power supply of the sound output means. Even when the power of the sound output means is off, the first diode is turned on when the voltage applied to the output terminal of the sound output means becomes equal to or higher than the forward voltage of the first diode. Therefore, the induced electromotive voltage applied to the audio output means is clamped, so that the maximum voltage rating of the output terminal of the audio output means is exceeded and the current flow to the protective diode provided on this output terminal is suppressed. It is possible to provide a safe induction heating type rice cooker without destruction. Further, when the sound output means outputs sound, the first diode is reverse-biased, so that the current consumption is not increased and power saving can be realized.

  In a fourth aspect based on the third aspect, the induced electromotive voltage protection means comprises a signal path between the speaker and the sound output means, and a second diode connected so as to be reverse-biased between the ground potential. Even if a negative induced electromotive voltage is generated in the speaker winding, the second diode clamps the induced electromotive voltage in the speaker winding with the forward voltage of the second diode. Exceeding the maximum voltage rating of the output terminal and suppressing the flow of current to the protective diode provided in the output terminal can provide a safe induction heating rice cooker that is not damaged. Further, when the sound output means outputs sound, the second diode is reverse-biased, so that an increase in current consumption is eliminated and power saving can be realized.

  According to a fifth invention, in any one of the first to fourth inventions, the voice output means outputs a voice storage circuit that outputs previously stored voice data as a signal, and a predetermined frequency or higher of the signal of the voice storage circuit A filter circuit for attenuating a component and a low-frequency component below a predetermined value, and an amplifier circuit for amplifying the output signal of the filter circuit, so that at least power supply to the amplifier circuit is stopped when sound is not output Since the power input to the speaker can be increased, the volume can be increased, and the voice can be heard even in a user with poor hearing or noise during cooking. Also, when no sound is output, the power supply to the amplifier circuit is stopped, so even if the high-frequency magnetic field generated from the heating coil is superimposed on the input part of the amplifier circuit as noise, it is output as noise from the speaker. It will not be done. Further, since the power supply of the amplifier circuit is turned off when no sound is output, power saving can be realized.

According to a sixth invention, in any one of the first to fourth inventions, the amplifier circuit includes a first amplifier circuit and a second amplifier circuit, and the speaker has one terminal connected to the first amplifier circuit. connect the output, that the other terminal connected to the output of the second amplifier circuit, the output signal of the second amplifier circuit output signal and of the first amplifier circuit which is adapted to invert each other Since almost the same voltage as the power supply voltage of the first amplifier circuit and the second amplifier circuit can be applied to the speaker, a sufficient sound volume can be ensured even if the power supply voltage is lowered. The voice can be heard even in the noise. In addition, by lowering the power supply voltage of the amplifier circuit, the power supply voltage of the voice storage circuit and the power supply voltage of the amplifier circuit can be made the same power supply. Can be turned off to save energy.

  According to a seventh invention, in the fifth or sixth invention, the amplification factor of the amplifier circuit is 1 or less, and a noise sound is output during a sound output or a silent period until the next sound is output. Even if they are superimposed, this noise sound can be reduced.

  In an eighth aspect based on any one of the fifth to seventh aspects, the audio output means has a plurality of filter circuits having different frequency characteristics, and an arbitrary filter circuit is set based on a setting input by a user. Therefore, it is possible to output sound with the sound quality desired by the user.

  According to a ninth invention, in any one of the first to eighth inventions, the communication between the control means and the sound output means is performed when the operation of the inverter circuit is stopped. As a result, it is possible to prevent defects such as communication being disturbed and voice not being output, thereby providing a highly reliable rice cooker.

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 partial block diagram of the induction heating rice cooker according to Embodiment 1 of the present invention, and FIG. 2 is a cross-sectional view of the induction heating rice cooker. In order to simplify the drawing, lead wires for electrical connection and screws for fixing components are omitted.

  As shown in FIG. 1, the heating coil 1 induction-heats the pan 35 (refer FIG. 2), and is comprised with the litz wire which bundled the copper wire with a small wire diameter. The inverter circuit 2 supplies a high-frequency current to the heating coil 1, and although not shown, a semiconductor switching element made of IGBT, a diode reversely connected to the semiconductor switching element, and the resonance circuit constituting the resonance circuit with the heating coil 1 The semiconductor switching element is switched at a high frequency to supply a high-frequency current to the heating coil. The diode bridge 3, the choke coil 4, and the capacitor 5 rectify the commercial power supply 6 and supply power to the inverter circuit 2.

  The input means 7 is comprised with the several momentary switch, and the user can select the rice cooking method, the start or stop of rice cooking, etc. The display means 8 is comprised with the liquid crystal display and LED, and displays the content which the user set, the state of the rice cooker during rice cooking, during reservation, and the elapsed time of rice cooking.

  The control means 9 is composed of a microcomputer, an IC for driving a semiconductor switching element, etc., and receives the on / off control of the inverter circuit 2 and the input signal of the switch constituting the input means 7, and sets the contents set in the LCD. Display or operate the rice cooking sequence and heat retention sequence.

  The speaker 10 uses a type in which a coil and a magnet are used to vibrate the coil with a current flowing in the winding and a magnetic field of the magnet. In the present embodiment, the impedance of the speaker 10 is made larger than 8Ω in order to reduce the current flowing through the speaker 10. The speaker 10 has one of input terminals connected to the ground potential.

  The audio output means 11 includes a memory (audio storage circuit) 12 that stores audio data as 4-bit data, a DA converter 13 that converts a digital signal output from the memory 12 into an analog signal, and an output signal of the DA converter 13 The filter circuit 18 includes a high-pass filter composed of a resistor 14 and a capacitor 15 for attenuating low-frequency components, a low-pass filter composed of a resistor 16 and a capacitor 17 for attenuating high-frequency components, and an output voltage of the filter circuit 18 is set to a predetermined value. The operational amplifier (amplifier circuit) 19 is used to amplify at a magnification of.

  The DC component cutting capacitor 20 prevents a DC voltage from being applied to the speaker 10.

  The resistor 21 constitutes an induced electromotive voltage protection means. The resistor 21 is connected between one input terminal of the speaker 11 and the ground potential. Note that the same effect is obtained when the resistor 21 is connected between the output terminal of the operational amplifier 19 and the ground potential.

  In this embodiment, the driving means 22 is constituted by a push-pull circuit composed of a PNP transistor and an NPN transistor, and turns on / off the IGBT constituting the inverter circuit 2 in response to an on / off signal from the control means 9.

The first DC power supply 23 is constituted by a switching power supply, and the voltage obtained by rectifying the commercial power supply 6 is about 2
It is converted to 0V DC power. The output voltage 20V of the first DC power supply 23 is a voltage necessary for turning on the IGBT, and is supplied to the IGBT via the driving means 22, and the IGBT is turned on. The second DC power supply 24 is composed of an NPN transistor and a Zener diode. The voltage of the second DC power supply 24 is about 5V, which serves as the power supply for the microcomputer constituting the control means 9, the memory 12 constituting the audio output means 11, and the DA converter 13. The third DC power supply 25 has the same configuration as the second DC power supply 24, and the output voltage is about 10V. The third DC power supply 25 supplies power to the operational amplifier 19 constituting the audio output means 11.

  In this embodiment, the electronic switch 26 is composed of a PNP transistor and an NPN transistor. The electronic switch 26 is turned on / off in response to a signal from the control means 9 and supplies power to the third DC power supply 25 or stops. .

  Next, as shown in FIG. 2, the rice cooker main body 31 is provided with a lid 32 that covers its upper surface so as to be freely opened and closed. The storage unit 33 of the rice cooker body 31 has the heating coil 1 disposed at the bottom thereof, and the ferrite core 34 disposed on the outer peripheral side of the heating coil 1. The heating coil 1 is a winding having a center substantially directly below the center of the bottom of the pan 35. The pan 35 is made of a magnetic material such as stainless steel, iron, or copper. The pan 35 has a flange protruding outward at the upper end opening, and is placed in the storage portion 33 in a detachable manner by placing the flange in a state of being lifted from the upper end of the storage portion 33. Therefore, the pan 35 has a gap between it and the storage portion 33 when stored.

  A detachable lid heating plate 36 is set on the lid 32. The lid heating plate 36 is made of a metal such as stainless steel. A lid heating coil 37 (not shown in FIG. 1) is built in the lid 32 to inductively heat the lid heating plate 36.

  The first circuit board 38 is mounted with switches constituting the input means 7, LCDs and LEDs constituting the display means 8, microcomputers constituting the control means 9, sound output means 11, resistors 21 and the like. On the second circuit board 39, components constituting the inverter circuit 2, the diode bridge 3, the choke coil 4, the capacitor 5, and the like are mounted. Although not particularly shown, the first circuit board 38 and the second circuit board 39 are electrically connected by lead wires to realize the circuit configuration shown in FIG. The wind-up type power cord storage unit 40 is electrically connected to the second circuit board 39 via a lead wire. The power cord storage unit 40 can wind up the power cord using a stopper and a spring.

  The temperature detection means 41 detects the temperature of the pan 35, is constituted by a thermistor, and is arranged at the approximate center of the bottom of the pan 35. Since the resistance value of the thermistor changes with temperature, a voltage dividing circuit is configured with this thermistor and a resistor having a predetermined resistance value, and the resistance value of the thermistor is analogized by supplying a predetermined voltage to both ends of the voltage dividing circuit. Can be converted to voltage. The microcomputer constituting the control means 9 shown in FIG. 1 estimates the temperature from this analog voltage using a built-in AD converter.

  As shown in FIG. 2, the speaker 10 is disposed using a gap formed between the rice cooker body 31 and the heating coil 1, and the output surface of the speaker 10 is disposed below the heating coil 1. Note that the direction and location of the speaker 10 are not particularly limited, and the output surface of the speaker 10 may be upward, or may be placed on the lid 32 if there is a space.

The operation and action of the above configuration will be described with reference to FIG. 3 shows the operation waveform of the main part of the induction heating rice cooker in the present embodiment, (1) is the current waveform of the heating coil 1, (2) is the voltage waveform of the output terminal of the operational amplifier 19, and (3) is the resistor 21. The voltage waveform of the output terminal of the operational amplifier 19 when is removed is shown.

  First, when the user operates a switch (input means 7) provided on the first circuit board 38, the control means 9 turns on the electronic switch 26 in accordance with the content of the pressed switch, and the third DC power supply. 25 is activated to supply power to the operational amplifier 19. Thereafter, the control means 9 transmits a signal so as to output predetermined audio data to the memory 12. Thereafter, the inverter circuit 2 is turned on to drive a fan (not shown). The memory 12 outputs predetermined audio digital data to the DA converter 13 based on the transmission data from the control means 9, and the DA converter 13 converts it into an analog signal. The analog signal is input to the operational amplifier 19 through the filter circuit 18, and the operational amplifier 19 amplifies the voltage to drive the speaker 10. The speaker 10 vibrates when a signal from the operational amplifier 19 is input via the capacitor 20, and this vibration becomes sound and notifies the user of the sound. When the voice notification is finished, the control means 9 turns off the electronic switch 26 and stops the power supply to the third DC power supply 25, thereby turning off the power supply of the operational amplifier 19. During this time, the control means 9 controls the inverter circuit 2 to supply a high frequency current to the heating coil 1, and heats the pan 35 according to a predetermined heating sequence.

  When a high frequency current is passed through the heating coil 1, a high frequency magnetic field is generated from the heating coil 1. Most of the high-frequency magnetic field is consumed as an eddy current on the surface of the pan 35, but the portion that is not consumed becomes a leakage magnetic field and generates an induced electromotive voltage in the winding of the speaker 10.

  The induced electromotive voltage is a large value because it is not consumed unless a current is passed through a resistor or the like. On the other hand, when the power supply is turned off, the output terminal of the operational amplifier 19 becomes a high impedance state, and the potential of the output terminal becomes unstable. When these two conditions overlap, a voltage that is clamped by the protective diode inside the operational amplifier 19 is applied to the output terminal of the operational amplifier 19 as shown in FIG. If the current continues to flow through the protection diode, the protection diode generates heat and breaks down, and the operational amplifier 19 does not operate.

  Therefore, if the resistor 21 is arranged between the output terminal of the operational amplifier 19 and the signal path of the speaker 10 and the ground potential, a current flows through the resistor 21 and the induced electromotive voltage of the speaker 10 becomes small as shown in FIG. The current does not flow into the 19 protection diodes, and the destruction of the operational amplifier 19 can be suppressed. The induced electromotive voltage decreases as the resistance value of the resistor 21 decreases. However, since the current flowing through the resistor 21 increases when sound is output, the operational amplifier 19 and the third DC power supply 25 are burdened. Therefore, the resistance value of the resistor 21 needs to be set to about 20 to 40 times the impedance of the speaker 10 to suppress the influence on the operational amplifier 19 and the third DC power supply 25.

  As described above, in the present embodiment, when a high-frequency current flows through the heating coil 1, induced electromotive voltage protection that reduces the induced electromotive voltage generated in the speaker 10 in the signal path between the speaker 10 and the audio output means 11. Since the resistor 21 constituting the means is provided, the induced electromotive voltage generated in the winding of the speaker 10 can be reduced by the resistor 21, and the induced electromotive voltage is also generated when the power of the audio output means 11 is off. Exceeding the maximum voltage rating of the output terminal of the audio output means 11 and preventing current from flowing into the audio output means 11 through the protective diode provided at the output terminal, thereby preventing the audio output means 11 from being destroyed. Can do. Further, since the power of the sound output means 11 is turned off when no sound is output, even when a high frequency current flows through the heating coil 1 and a high frequency magnetic field is generated, a noise waveform due to this high frequency magnetic field is superimposed on the sound output means 11. In addition, no noise sound is generated from the speaker 10. Therefore, it is possible to provide a rice cooker that is safe, compact, energy-saving, and easy to understand such as operation.

Further, since the induced electromotive voltage protection means is composed of the resistor 21 connected between the signal path of the speaker 10 and the sound output means 11 and the ground potential, the induced electromotive voltage generated in the winding of the speaker 10 is consumed by the resistor 21. Thus, the induced electromotive voltage of the speaker 10 can be reduced. Furthermore, in order to reduce the induced electromotive voltage, a current flows through the winding and the resistor of the speaker 10, but since this current can also be limited by the resistance, heat generation of the winding of the speaker 10 can be suppressed. Therefore, since the heat generation of the speaker 10 is small and the induced electromotive voltage can be reduced with an inexpensive component such as a resistor, a low-cost and highly reliable rice cooker can be provided.

  In this embodiment, the audio output means 11 is composed of the memory 12 storing the audio data, the filter circuit 18 and the operational amplifier 19, but if these are integrated in one IC, the mounting area is reduced. A compact rice cooker can be provided.

  Further, in this embodiment, the induced electromotive voltage protection means is constituted by the resistor 21. However, when a capacitor is connected in parallel with this, a particularly high frequency component can be removed. It can be surely suppressed. However, if the capacity of the capacitor is increased too much, the audio signal may be distorted and uncomfortable for the user. Therefore, it is desirable that the capacitor be sufficiently smaller than the DC cut capacitor 20.

(Embodiment 2)
FIG. 4: shows the principal part circuit diagram made into the partial block of the induction heating type rice cooker in Embodiment 2 of this invention.

  As shown in FIG. 4, the first diode 51 constitutes an induced electromotive voltage protection means. The anode is connected to the signal path of the speaker 10 and the amplifier 19, and the cathode is the output terminal of the third DC power supply 25. Connected to. Note that the forward voltage VF of the first diode 51 is set to be smaller than the forward voltage VF of the protection diode provided inside the operational amplifier 19. 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 with reference to FIG. FIG. 5 shows the operation waveform of the main part of the induction heating rice cooker in the present embodiment, (1) is the current waveform of the heating coil 1, (2) is the voltage waveform of the output terminal of the operational amplifier 19, and (3) is the first. The voltage waveform when the diode 51 is removed is shown.

  First, when the user operates a switch (input means 7) provided on the first circuit board 38, the control means 9 turns on the electronic switch 26 in accordance with the content of the pressed switch, and the third DC power supply. 25 is activated to supply power to the operational amplifier 19. Thereafter, the control means 9 transmits a signal so as to output predetermined audio data to the memory 12. Thereafter, the inverter circuit 2 is turned on to drive a fan (not shown). The memory 12 outputs predetermined audio digital data to the DA converter 13 based on the transmission data from the control means 9, and the DA converter 13 converts it into an analog signal. The analog signal is input to the operational amplifier 19 through the filter circuit 18, and the operational amplifier 19 amplifies the voltage to drive the speaker 10. The speaker 10 vibrates when a signal from the operational amplifier 19 is input via the capacitor 20, and this vibration becomes sound and notifies the user of the sound. When the voice notification is finished, the control means 9 turns off the electronic switch 26 and stops the power supply to the third DC power supply 25, thereby turning off the power supply of the operational amplifier 19. During this time, the control means 9 controls the inverter circuit 2 to supply a high frequency current to the heating coil 1, and heats the pan 35 according to a predetermined heating sequence.

  When a high frequency current is passed through the heating coil 1, a high frequency magnetic field is generated from the heating coil 1. Most of the high-frequency magnetic field is consumed as an eddy current on the surface of the pan 35, but the portion that is not consumed becomes a leakage magnetic field and generates an induced electromotive voltage in the winding of the speaker 10.

  The induced electromotive voltage is a large value because it is not consumed unless a current is passed through a resistor or the like. On the other hand, when the power supply is turned off, the output terminal of the operational amplifier 19 becomes a high impedance state, and the potential of the output terminal becomes unstable. If these two conditions overlap, a voltage that is clamped by the protective diode inside the operational amplifier 19 is applied to the output terminal of the operational amplifier 19 as shown in FIG. If the current continues to flow through the protective diode, the protective diode generates heat and breaks down, and the operational amplifier 19 does not operate.

  Therefore, when the first diode 51 is arranged between the output terminal of the operational amplifier 19, the signal path of the speaker 10, and the output terminal of the third DC power supply 25, the first diode 51 is turned off when the third DC power supply 25 is off. 5 is grounded, the current flows through the first diode 51, the induced electromotive voltage of the speaker 10 becomes small as shown in FIG. 5 (2), and the current does not flow into the protective diode of the operational amplifier 19. 19 destruction can be suppressed.

  As described above, in the present embodiment, the induced electromotive voltage protection means is connected so as to be reverse-biased between the signal path of the speaker 10 and the audio output means 11 and the high potential of the power supply of the audio output means 11. Since the first diode 51 is used, even when the power of the audio output unit 11 is off, the first voltage applied to the output terminal of the audio output unit 11 is equal to or higher than the forward voltage of the first diode 51. Since the diode 51 is turned on and the induced electromotive voltage applied to the audio output means 11 is clamped, the maximum voltage rating of the output terminal of the audio output means 11 is exceeded, or the current to the protection diode provided at this output terminal The inflow of rice can be suppressed, and a safe induction heating rice cooker without destruction can be provided. Further, when the audio output means 11 outputs audio, the first diode is reverse-biased, so that an increase in current consumption is eliminated and power saving can be realized.

(Embodiment 3)
FIG. 6: shows the principal part circuit diagram made into the partial block of the induction heating type rice cooker in Embodiment 3 of this invention.

  As shown in FIG. 6, the second diode 52 constitutes an induced electromotive voltage protection means, and has an anode connected to the ground potential and a cathode connected to the signal path of the speaker 10 and the operational amplifier 19. Note that the forward voltage VF of the second diode 52 is made smaller than the forward voltage VF of the protection diode provided inside the operational amplifier 19. Other configurations are the same as those of the second embodiment, and the same reference numerals are given and description thereof is omitted.

  The operation and action of the above configuration will be described with reference to FIG. FIG. 7 shows the operation waveform of the main part of the induction heating rice cooker in this embodiment, (1) is the current waveform of the heating coil 1, (2) is the voltage waveform of the output terminal of the operational amplifier 19, and (3) is the first. The voltage waveform when the diode 51 and the second diode 52 are removed is shown.

First, when the user operates a switch (input means 7) provided on the first circuit board 38, the control means 9 turns on the electronic switch 26 in accordance with the content of the pressed switch, and the third DC power supply. 25 is activated to supply power to the operational amplifier 19. Thereafter, the control means 9 transmits a signal so as to output predetermined audio data to the memory 12. Thereafter, the inverter circuit 2 is turned on to drive a fan (not shown). The memory 12 outputs predetermined audio digital data to the DA converter 13 based on the transmission data from the control means 9, and the DA converter 13 converts it into an analog signal. The analog signal is input to the operational amplifier 19 through the filter circuit 18, and the operational amplifier 19 amplifies the voltage to drive the speaker 10. The speaker 10 vibrates when a signal from the operational amplifier 19 is input via the capacitor 20, and this vibration becomes sound and notifies the user of the sound. When the voice notification is finished, the control means 9 turns off the electronic switch 26 and stops the power supply to the third DC power supply 25, thereby turning off the power supply of the operational amplifier 19. During this time, the control means 9 controls the inverter circuit 2 to supply a high frequency current to the heating coil 1, and heats the pan 35 according to a predetermined heating sequence.

  When a high frequency current is passed through the heating coil 1, a high frequency magnetic field is generated from the heating coil 1. Most of the high-frequency magnetic field is consumed as an eddy current on the surface of the pan 35, but the portion that is not consumed becomes a leakage magnetic field and generates an induced electromotive voltage in the winding of the speaker 10.

  The induced electromotive voltage is a large value because it is not consumed unless a current is passed through a resistor or the like. On the other hand, when the power supply is turned off, the output terminal of the operational amplifier becomes a high impedance state, and the potential of the output terminal becomes unstable. When these two conditions overlap, a voltage that is clamped by the protective diode inside the operational amplifier 19 is applied to the output terminal of the operational amplifier 19 as shown in FIG. If the current continues to flow through the protective diode, the protective diode generates heat and breaks down, and the operational amplifier 19 does not operate.

  Therefore, when the first diode 51 is arranged between the output terminal of the operational amplifier 19, the signal path of the speaker 10, and the output terminal of the third DC power supply 25, the first diode 51 is turned off when the third DC power supply 25 is off. 7 is grounded, the current flows through the first diode 51, the induced electromotive voltage of the speaker 10 becomes small as shown in FIG. 7B, and the current does not flow into the protective diode of the operational amplifier 19. 19 destruction can be suppressed.

  In addition, since the voltage lower than the ground potential is also clamped by the second diode 52, no current flows into the protection diode of the operational amplifier 19, and the destruction of the operational amplifier 19 can be suppressed.

  As described above, in the present embodiment, the induced electromotive voltage protection means includes the signal path of the speaker 10 and the audio output means 11 and the second diode 52 connected so as to be reverse-biased between the ground potential. Therefore, even if a negative induced electromotive voltage is generated in the winding of the speaker 10, the second diode 52 clamps the induced electromotive voltage in the winding of the speaker 10 with the forward voltage of the second diode 52. The maximum voltage rating of the output terminal of the audio output means 11 will be exceeded, and the flow of current to the protective diode provided at this output terminal will be suppressed, and a safe induction heating rice cooker without destruction can be provided. Further, when the audio output means 11 outputs audio, the second diode 52 is reverse-biased, so that an increase in current consumption is eliminated and power saving can be realized.

(Embodiment 4)
FIG. 8 shows a partial circuit diagram of a partial block of the induction heating rice cooker according to Embodiment 4 of the present invention.

  As shown in FIG. 8, the audio output means 921, a memory (audio storage circuit) 12 that stores audio data as 4-bit data, a DA converter 13 that converts a digital signal output from the memory 12 into an analog signal, A filter circuit including a high-pass filter 93 including a resistor 81 and a capacitor 82 for attenuating a low-frequency component of the output signal of the converter 13, a low-pass filter 94 including a resistor 83 and a capacitor 84 for attenuating a high-frequency component, and a filter circuit The power supply to the amplifier circuit is stopped when no sound is output.

Here, the amplifier circuit is composed of a first amplifier circuit and a second amplifier circuit, and the first amplifier circuit is composed of an operational amplifier 85, a high-pass filter 93, and a low-pass filter 94, and the output of the DA converter 13. Are attenuated, and signals in other frequency bands are inverted and amplified. The amplification factor of the first amplifier circuit is determined by the ratio of the resistor 83 to the resistor 81. In this embodiment, the ratio of the resistor 81 and the resistor 83 is 1, and the amplification factor of the first amplifier circuit is 1. ing. By setting the ratio to 1, the noise component from the DA converter 13 can be prevented from being amplified. For example, the noise sound from the speaker 10 can be reduced during the silent period between the sounds. Furthermore, since the ratio is reduced even if external noise such as illegal radio waves comes during the silent period between voices, the noise sound from the speaker 10 can be suppressed.

  The second amplifier circuit includes an operational amplifier 86, a resistor 87, and a resistor 88, and inverts and amplifies the output of the first amplifier circuit. The amplification factor of the second amplifier circuit is determined by the ratio of the resistor 87 and the resistor 88. In this embodiment, the ratio of the resistor 87 and the resistor 88 is set to 1, and the amplification factor is set in the same manner as the first amplifier circuit. 1, the output of the first amplifier circuit is inverted and amplified.

  The output terminal of the operational amplifier 85 is connected to one terminal of the speaker 10 via the DC component cutting capacitor 20. The output terminal of the operational amplifier 86 is connected to the other terminal of the speaker 10. The resistor 89 is connected to the output terminal of the operational amplifier 85 and the ground potential, and the resistor 90 is connected to the output terminal of the operational amplifier 86 and the ground potential when the power supply of the operational amplifier 85 is off. The effect of the resistors 89 and 90 is to reduce the induced electromotive voltage generated in the windings of the speaker 1 as described in the first embodiment. Reference numeral 91 is a reference voltage of the operational amplifiers 85 and 86, and is composed of a resistance voltage dividing circuit.

  The memory (sound storage circuit) 12 and the DA converter 13 constituting the sound output means 92 are supplied from a third DC power supply 93. 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. Since the low-frequency component of the output signal of the DA converter 13 is attenuated by the high-pass filter 93 and the high-frequency component is attenuated by the low-pass filter 94, it is possible to reduce the distortion of the waveform of the audio signal and the feeling of volume of the audio during DA conversion. , Can output clear voice. Since the signal is attenuated by the high-pass filter 93 and the low-pass filter 94 before the signal is output to the speaker 10, it is not affected by the impedance of the speaker 10. Therefore, highly accurate filter characteristics can be obtained, and variations in sound quality can be suppressed. Since the operational amplifier can increase the maximum value of the output power as compared with the DA converter, the volume of the speaker 10 can be increased, and the voice can be heard even in the presence of a user with poor hearing or noise during cooking. When no sound is output, the power supply to the operational amplifier 85 constituting the first amplifier circuit and the operational amplifier 86 constituting the second amplifier circuit is stopped, so that the high frequency magnetic field generated from the heating coil 1 becomes noise and DA. Even if superimposed on the output signal of the sound transformer 13 or the signal of the high-pass filter 93 or the low-pass filter 94, no power is supplied from the operational amplifiers 85 and 86 to the speaker 10, so that it is output as noise from the speaker 10. There is no.

  Further, by performing inverting amplification using the two operational amplifiers 85 and 86, it is possible to apply almost the same voltage as the power supply voltage of the operational amplifiers 85 and 86 to the speaker 10, and therefore the power supply voltage of the operational amplifiers 85 and 86. Can be made the same as the power supply voltage of the memory 12 and the DA converter 13. Therefore, since all the power sources of the components constituting the audio output unit 92 can be turned off, power saving can be realized. In addition, since the rise of the output voltage of the two operational amplifiers 85 and 86 is almost the same, the noise sound is not applied to the speaker 10 when the power of the operational amplifiers 85 and 86 is turned on, which makes the user uncomfortable. Never give.

In addition, since the operational amplifier 85, the high-pass filter 93, and the low-pass filter 94 constitute the first amplifier circuit, it is possible to reduce the parts of the filter circuit portion and to configure a compact audio output means.

  As described above, in the present embodiment, by using the two operational amplifiers 85 and 86 so that the voltage almost the same as the power supply voltage can be output, one power source of the components constituting the audio output unit 92 is shared, Can be turned on and off. Thereby, it is possible to realize power saving when no sound is output. In addition, since the induced electromotive voltage generated in the speaker winding due to the resistance is reduced, it is possible to obtain high reliability that does not destroy the audio output means even when the power is turned off.

  As described above, in the present embodiment, the memory 12 that outputs the audio data stored in advance as the audio output means 92 as a signal, the DA converter 13 that converts the digital signal of the memory 12 into an analog signal, and the DA conversion A high-pass filter 93 for attenuating the low-frequency component of the output signal of the converter 13, a low-pass filter 94 for attenuating the high-frequency component of the output signal of the DA converter 13, and an amplifier circuit composed of an operational amplifier 85 and an operational amplifier 86. When not outputting, the power supply to the operational amplifier 85 and the operational amplifier 86 is stopped. First, since there are the high-pass filter 93 and the low-pass filter 94, noise sound during voice output can be reduced, and user discomfort can be reduced. Moreover, since the input power to the speaker 10 is increased by the operational amplifiers 85 and 86, the volume of the speaker 10 can be increased, so that even a person with poor hearing can hear it, and the sound can be heard even when there is noise during cooking. Can be heard. Further, since the power supply of the amplifier circuit composed of the operational amplifiers 85 and 86 is turned off when no sound is output, noise due to the high frequency magnetic field from the heating coil 1 causes the output signal of the DA converter 13, the output signal of the high pass filter 93, and the low pass. Even if it is superimposed on the output signal of the filter 94, power is not supplied from the operational amplifiers 85 and 86 to the speaker 10, so that no noise sound is output from the speaker 10. Further, when no sound is output, the power supply circuit is turned off, so that power saving can be realized.

  The amplifier circuit is composed of a first amplifier circuit and a second amplifier circuit, and the speaker 10 has one terminal connected to the output of the first amplifier circuit and the other terminal connected to the output of the second amplifier circuit. Since the output signal of the first amplifier circuit and the output signal of the second amplifier circuit are inverted to each other, the voltage almost the same as the power supply voltage of the first amplifier circuit and the second amplifier circuit is applied to the speaker. 10 can be applied even if the power supply voltage is lowered, so that a sufficient sound volume can be ensured, and the voice can be heard even in a user with poor hearing or noise during cooking. In addition, by lowering the power supply voltage of the amplifier circuit, it is possible to make the power supply voltage of the memory 12 and the power supply voltage of the amplifier circuit the same power supply. When no sound is output, the power supply of the memory 12 and the amplifier circuit is turned off. As a result, energy saving can be realized.

  In addition, since the amplification factor of the amplifier circuit is 1 or less, even if external noise such as illegal radio waves comes during the sound output or the silence period until the next sound is output, the noise sound from the speaker 10 is output. It is possible to suppress the discomfort of the user.

(Embodiment 5)
FIG. 9: shows the principal part circuit diagram made into the partial block of the induction heating type rice cooker in Embodiment 5 of this invention.

As shown in FIG. 9, the diode 101 is connected to the signal path of the speaker 10 and the operational amplifier 85 so as to be reverse-biased to the ground potential. The diode 102 is connected to the signal path of the speaker 10 and the operational amplifier 85 and the third DC power supply 93 so as to be reverse-biased. The diode 103 is connected to the signal path of the speaker 10 and the operational amplifier 86 so as to be reverse-biased to the ground potential. The diode 104 is connected so as to be reverse-biased to the signal path of the speaker 10 and the operational amplifier 86 and the third DC power supply 93. Other configurations are the same as those in the fourth embodiment, and the same reference numerals are given and description thereof is omitted.

  Thus, by connecting the diodes 101, 102, 103, and 104, the induced electromotive voltage generated in the winding of the speaker 10 can be clamped even when the third DC power supply 93 is turned off. 85 and 86 can be prevented from being destroyed.

(Embodiment 6)
FIG. 10: shows the principal part circuit diagram made into the partial block of the induction heating type rice cooker in Embodiment 6 of this invention.

  As shown in FIG. 10, the audio output means 111 has a plurality of filter circuits having different frequency characteristics, that is, a first low-pass filter 114 and a second low-pass filter 118, and is arbitrarily set based on a setting input by the user. The filter circuit is set. That is, the resistor 112 and the capacitor 113 constitute a first low-pass filter 114, which is turned on and off by a switching element 115 constituted by an NPN transistor or the like. The resistor 116 and the capacitor 117 constitute a second low-pass filter 118, which is turned on and off by a switching element 119 constituted by an NPN transistor or the like. The cutoff frequency of the first low-pass filter 114 is higher than the cutoff frequency of the second low-pass filter 118. When the user selects a predetermined sound quality (low sound or high sound) with the input means, the control means 120 turns on a predetermined low-pass filter according to the selected content. 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. In the initial setting, assuming that the kitchen is being cooked, the first low-pass filter 114 having a high cut-off frequency is selected so that sound can pass even in a slightly noisy place. However, for example, if the place where the rice cooker is used is a relatively quiet place, the high-pitched part of the sound may be annoying. In such a case, the user selects the sound quality to be low with the input means 7. Then, the control means 120 turns off the switching element 115, turns off the first low-pass filter 114, turns on the switching element 119, and turns on the second low-pass filter 118.

  Since the cutoff frequency of the second low-pass filter 118 is lower than that of the first low-pass filter 114, the high-frequency component is removed, the volume of the high-frequency part is reduced, and the user's discomfort can be reduced.

  In addition to the usage environment, the ease of listening varies depending on the age of the user. For example, in this embodiment, the cutoff frequency is increased and the volume of treble is increased so that even an elderly person can easily hear. However, in the case of a young person, this treble may be annoying. Also in this case, when the user selects the sound quality to be low with the input means 7, the second low-pass filter 118 is selected, and the volume of the annoying high sound can be reduced.

  As described above, in the present embodiment, the audio output unit 111 has a plurality of filter circuits having different frequency characteristics, that is, the first low-pass filter 114 and the second low-pass filter 118, and is input by the user. Since an arbitrary filter circuit is set based on the setting, it is possible to output sound with a user-preferred sound quality that is comfortable and easy to hear according to the usage environment and age by switching to the high sound side and low sound side Can do.

  In the present embodiment, two filter circuits of the first low-pass filter 114 and the second low-pass filter 118 are used. However, the number of filter circuits is not limited to two. Further, audio data having different sound quality may be stored in advance in the memory 12 of the audio output unit 111 so that the user can select a sound quality that the user likes.

(Embodiment 7)
Communication between the control means 9 and the audio output means 11 shown in FIG. 1 is performed when the operation of the inverter circuit 2 is stopped. Other configurations are the same as those of the first embodiment.

  The operation and action of the above configuration will be described with reference to FIG. FIG. 11 shows an operation time chart of the induction heating rice cooker in the present embodiment. (1) is a voltage waveform of the commercial power source 6, and (2) is a waveform that outputs high or low in synchronization with 0 V of the commercial power source 6. (3) is a diagram showing on / off of the electronic switch 26, (4) is an output voltage waveform of the third DC power supply 25, (5) is a transmission signal waveform from the control means 9 to the memory 12, (6) Indicates the input voltage of the speaker 10, and (7) indicates the on / off state of the inverter circuit 2.

  First, when the user operates a switch (input means 7) provided on the first circuit board 38 (see FIG. 2), a signal from the input means 7 is input to the control means 9. Then, at T0 in FIG. 11, the control means 9 turns on the electronic switch 26 in synchronization with the zero voltage of the commercial power supply 6, starts the third DC power supply 25, and supplies a DC voltage to the operational amplifier 19. At this time, since the output voltage of the third DC power supply 25 fluctuates, the output voltage of the operational amplifier 19 fluctuates, and the fluctuation of this output voltage is applied to the speaker 10 via the capacitor 20 and is output as noise sound. Sometimes. However, this noise can be reduced by slowing the rising speed of the output voltage of the third DC power supply 25.

  Thereafter, at T1 in FIG. 11, the control means 9 transmits the volume setting data to the memory 12 again in synchronization with the zero voltage of the commercial power source 6. Thereafter, at T2 in FIG. 11, the control unit 9 transmits address data indicating predetermined audio data to the memory 12 in synchronization with the zero voltage of the commercial power supply 6. Then, at T3 in FIG. 11, the memory 12 outputs predetermined audio digital data to the DA converter 13 based on the transmission data from the control means 9, and the DA converter 13 converts the audio signal into an analog voltage. And an audio signal is input to the speaker 10 through the filter circuit 18, the operational amplifier 19, and the capacitor 20. The speaker 10 vibrates when an audio signal is input, and the vibration becomes sound and notifies the user of the sound. At this time, the low frequency component and the high frequency component of the audio signal are attenuated by the filter circuit 18, the attenuated audio signal is amplified by the operational amplifier 19, and the DC component is removed from the amplified audio signal by the capacitor 20.

  In T4 of FIG. 11, according to the menu set by the input means 12, the control means 9 starts on / off control of the inverter circuit 2, supplies high frequency power to the heating coil 1, and heats the pan. In the present embodiment, although not particularly illustrated, the control means 9 drives the fan motor in accordance with the supply of the high frequency power to the heating coil 1. When a current flows through the heating coil 1, as described in the first embodiment, an induced electromotive voltage is generated in the speaker 10. At this time, since the operational amplifier 19 is applied with a voltage, the internal protection of the operational amplifier 19 is protected. Since the diode is reverse-biased, no current flows from the speaker 10 to the output terminal of the operational amplifier 19.

  The audio output ends at T6 in FIG. At T6 in FIG. 11, the control means 9 shuts off the electronic switch 26 and stops the power supply to the third DC power supply 25. By stopping the power supply to the third DC power supply 25, the operational amplifier 19 is turned off, and the output terminal of the operational amplifier 19 becomes unstable. Therefore, even if an electric current flows through the heating coil 1 and an induced electromotive voltage is generated in the speaker 10, the electric current flows through the resistor 21, so that the induced electromotive voltage can be reduced. Therefore, no current flows into the operational amplifier 19, so that the operational amplifier 19 can be prevented from being destroyed.

In the present embodiment, since the control means 9 stores the time of the audio data in advance,
When a predetermined time elapses from that time, the electronic switch 26 is cut off. The reason why the shutoff timing of the electronic switch 26 is made sufficiently later than the time of the audio data is because the speed of the audio signal output from the memory 12 varies.

  As described above, in the present embodiment, communication between the control means 9 and the audio output means 11 is performed when the operation of the inverter circuit 2 is stopped, that is, before the inverter circuit 2 is controlled to be turned on / off, the control means 9 Since the data is transmitted to the memory 12 constituting the output means 11, it is possible to prevent the transmission waveform from fluctuating due to the switching noise or the high-frequency current flowing through the heating coil 1, and it is possible to prevent malfunction such as not outputting sound.

  In the present embodiment, even when the operational amplifier 19 is turned off when no sound is output, the induced electromotive voltage generated from the speaker 10 can be reduced by the resistor 21, so that current flows from the speaker 10 to the operational amplifier 19. It does not occur and the operational amplifier 19 can be prevented from being destroyed.

  As described above, the induction heating rice cooker according to the present invention destroys the sound output means even if the induction voltage is generated in the speaker by the magnetic field of the heating coil when the power supply of the sound output means is stopped. Since it can prevent, it is useful as an induction heating type rice cooker which has an audio | voice alerting | reporting function.

The principal part circuit diagram which made the induction heating type rice cooker of Embodiment 1 of this invention into a partial block Cross section of the induction heating rice cooker (1) Current waveform diagram of the heating coil of the induction heating rice cooker (2) Voltage waveform diagram of the output terminal of the operational amplifier of the induction heating rice cooker (3) When the resistance of the induction heating rice cooker is removed Voltage waveform diagram The principal part circuit diagram which made the partial block of the induction heating type rice cooker of Embodiment 2 of this invention (1) Current waveform diagram of the heating coil of the induction heating rice cooker (2) Voltage waveform diagram of the output terminal of the operational amplifier of the induction heating rice cooker (3) Remove the first diode of the induction heating rice cooker Voltage waveform diagram when The principal part circuit diagram made into the partial block of the induction heating type rice cooker of Embodiment 3 of this invention (1) Current waveform diagram of the heating coil of the induction heating rice cooker (2) Voltage waveform diagram of the output terminal of the operational amplifier of the induction heating rice cooker (3) The first diode and the first of the induction heating rice cooker Voltage waveform diagram when diode 2 is removed The principal part circuit diagram which made the partial block of the induction heating type rice cooker of Embodiment 4 of this invention The principal part circuit diagram which made the partial block diagram of the induction heating type rice cooker of Embodiment 5 of this invention The principal part circuit diagram made into the partial block of the induction heating type rice cooker of Embodiment 6 of this invention Operation time chart of induction heating type rice cooker of embodiment 7 of the present invention

DESCRIPTION OF SYMBOLS 1 Heating coil 2 Inverter circuit 9 Control means 10 Speaker 11 Audio | voice output means 21 Resistance (Inductive electromotive voltage protection means)
35 pots

Claims (9)

A heating coil for inductively heating the pan, an inverter circuit for supplying a high-frequency current to the heating coil, a control means for controlling the inverter circuit, a speaker, and an audio signal received from the control means to be output to the speaker And an induction electromotive voltage protection means for reducing an induced electromotive voltage generated in the speaker in a signal path of the speaker and the audio output means when a high frequency current flows through the heating coil. The speaker is arranged in the vicinity of the heating coil, and when the control means does not output sound, the power supply of the sound output means is stopped and the power supply of the sound output means is stopped during the heating coil operation. An induction heating rice cooker configured to reduce the induced electromotive force generated in the speaker . The induction heating type rice cooker according to claim 1, wherein the induced electromotive voltage protection means comprises a resistor connected between a signal path of the speaker and the sound output means and a ground potential. 2. The induction heating according to claim 1, wherein the induced electromotive voltage protection means comprises a first diode connected so as to be reverse-biased between a signal path of the speaker and the sound output means and a high potential of the power supply of the sound output means. Type rice cooker. The induction heating type rice cooker according to claim 1, wherein the induced electromotive voltage protection means comprises a signal path between the speaker and the sound output means and a second diode connected so as to be reverse-biased between ground potentials. An audio output means includes an audio storage circuit that outputs audio data stored in advance as a signal, a filter circuit that attenuates a predetermined high frequency component and a predetermined low frequency component of the signal of the audio storage circuit, and the filter circuit An induction heating rice cooker according to any one of claims 1 to 4, further comprising an amplifier circuit for amplifying an output signal, wherein at least power supply to the amplifier circuit is stopped when no sound is output. . The amplifier circuit includes a first amplifier circuit and a second amplifier circuit, and the speaker has one terminal connected to the output of the first amplifier circuit and the other terminal connected to the output of the second amplifier circuit. connected, induction heating cooker of the first output signal of the output signal and the second amplifier circuit in the amplifier circuit of claim 5, wherein the so inverted to each other. The induction heating rice cooker according to claim 5 or 6, wherein the amplification factor of the amplification circuit is 1 or less. The induction heating according to any one of claims 5 to 7, wherein the sound output means has a plurality of filter circuits having different frequency characteristics, and an arbitrary filter circuit is set based on a setting input by a user. Type rice cooker. The induction heating rice cooker according to any one of claims 1 to 8, wherein communication between the control means and the voice output means is performed when the operation of the inverter circuit is stopped.

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