JP4023438B2 - rice cooker - Google Patents

Description

  The present invention relates to a rice cooker that heats a pan by supplying high-frequency power to a heating coil by inverter means that rectifies an AC power supply and supplies power.

  Conventionally, this type of rice cooker supplies high-frequency current to the heating coil that heats the pan from the inverter means constituted by the switching element, detects the voltage at both ends of the switching means by the peak voltage detection means, and from the AC power source to the rice cooker The supplied input current is detected by the input current detection means, and the ON time of the switching means is shortened according to the higher output of the output of the voltage detection means and the output of the input current detection means, and the input current is reduced. (See, for example, Patent Documents 1 and 2).

  In addition, there is a coil current detection unit that detects a current flowing in the heating coil, and controls an input current supplied from an AC power source according to the output of the coil current detection unit and the output of the input current detection unit. (For example, refer to Patent Document 3).

  FIG. 8 shows a conventional rice cooker described in Patent Document 1. As shown in FIG.

  As shown in FIG. 8, the pan 1 shows an equivalent circuit, which is composed of a laminated body using a plurality of metals through which magnetic flux passes, and the heating coil 2 is magnetically coupled. The resonance capacitor 3 is connected in parallel to the heating coil 2 and constitutes a parallel resonance circuit with the heating coil 2. 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. These heating coil 2, resonance capacitor 3, and switching means 4 constitute inverter means.

  The AC power supply 5 is rectified by the rectifying means 6 constituted by the diode bridge 7, the choke coil 8, and the smoothing capacitor 9, and supplies power to the inverter means. The input current detection means 13 comprises a current transformer 14, a resistor 15, a diode bridge 16, and an electrolytic capacitor 17, and converts an alternating current signal from the current transformer 14 into a direct current signal by a rectifying / smoothing circuit comprising the diode bridge 16 and the electrolytic capacitor 17. Thus, the input current supplied from the AC power source 5 is detected.

The peak voltage detection means 51 is configured by an emitter follower circuit that detects the peak value of the IGBT collector voltage, and the control in which the output of the peak voltage detection means 51 and the output of the input current detection means 13 are configured by a microcomputer or the like. The control means 71 is configured to control the ON time of the switching means 4 in accordance with the output values of the input current detection means 13 and the peak voltage detection means 51.
Japanese Examined Patent Publication No. 61-26306 Japanese Patent Laid-Open No. 5-114472 JP 2003-135272 A

  However, in such a conventional configuration, the input current-output voltage characteristics (hereinafter referred to as input / output characteristics) of the current transformer 14 constituting the input current detection means 13 even though the reference voltage for setting the input current is constant. Varies depending on the frequency of the AC power supply, and there is a problem that the input current varies in the region of the AC power supply frequency of 50 Hz and the region of 60 Hz.

  Also, the emitter follower circuit constituting the peak voltage detection means 51 has a fixed time constant of the charge / discharge circuit, so that there is a problem that the peak voltage value to be detected varies in the region where the AC power supply frequency is 50 Hz and 60 Hz. Had.

  The present invention solves the above-described conventional problems, and an object thereof is to suppress variations in input current and peak voltage between regions having different frequencies of an AC power supply.

In order to achieve the above object, the present invention provides a heating coil for heating a pan, inverter means for supplying high-frequency power to the heating coil, switching means constituting the inverter means, rectifying an AC power source and the inverter means Rectifying means for supplying power to the power supply, power supply frequency detecting means for detecting the frequency of the AC power supply, power supply voltage detecting means for detecting the power supply voltage of the AC power supply, and setting a reference value for the output of the power supply voltage detecting means Power supply voltage setting means, input current detection means for detecting an input current supplied from the AC power supply, input current setting means for setting a reference voltage value corresponding to a target value of the input current, and the input current detection means an output value of the control means for controlling the on-time of said switching means in response to a reference voltage value of the input current setting unit, the power supply voltage detection Means to change the reference value depending on the output of the power supply frequency detecting means, the input current setting means, according to the frequency of the power supply frequency detecting unit detects, with changing the reference voltage value, wherein The reference voltage value is changed according to the difference between the output of the power supply voltage detection means and the reference value .

As a result, even if the input / output characteristics of the input current detection means and the power supply voltage detection means change due to a change in the frequency of the AC power supply, the reference voltage value and the power supply voltage corresponding to the target value of the input current are previously determined according to the power supply frequency. Since the reference value set by the setting means has been changed, the actual input current and the reference value will not fluctuate, and the target value of the input current will be constant so that the input power is constant between regions where the frequency of the AC power supply is different. Therefore, it is possible to suppress variations in input power between regions having different frequencies of the AC power supply.

The rice cooker of this invention can suppress the dispersion | variation in the input electric power which arises between the areas where the power supply frequency of AC power supply differs.

The first invention is a heating coil for heating a pan, inverter means for supplying high-frequency power to the heating coil, switching means for constituting the inverter means, rectification for rectifying an AC power source and supplying power to the inverter means Means, power frequency detection means for detecting the frequency of the AC power supply, power supply voltage detection means for detecting the power supply voltage of the AC power supply, and power supply voltage setting means for setting a reference value of the output of the power supply voltage detection means , Input current detection means for detecting an input current supplied from the AC power supply, input current setting means for setting a reference voltage value corresponding to a target value of the input current, an output value of the input current detection means , and the according to the reference voltage value of the input current setting means and control means for controlling the on-time of said switching means, said power supply voltage detecting means, said power supply peripheral Change the reference value depending on the power of several detection means, the input current setting means, according to the frequency of the power supply frequency detecting unit detects, with changing the reference voltage value, the power supply voltage detection means The reference voltage value is changed in accordance with the difference between the output and the reference value. Even if the input / output characteristics of the input current detection means and the power supply voltage detection means change due to a change in the frequency of the AC power supply, Since the reference voltage value corresponding to the target value of the input current and the reference value set by the power supply voltage setting means are changed according to the power supply frequency, the actual input current and the reference value will not fluctuate. between frequencies different regions, the input power will be able to change the target value of the input current to be constant, suppress variations in the input power of the frequency of the AC power source between different regions Door can be. A peak voltage detecting means for detecting a peak value of the voltage across the switching means; and an upper limit setting means for setting an upper limit value of the output of the peak voltage detecting means. The upper limit value is changed in accordance with the output of the means, and the control means shortens the ON time of the switching means when the output value of the peak voltage detection means exceeds the upper limit value. The peak voltage detection means Even if the input / output characteristics of the switching circuit change depending on the power supply frequency, the upper limit value is also changed corresponding to the power supply frequency, and the upper limit value of the peak voltage of the switching means can be suppressed from fluctuating depending on the power supply frequency.

According to a second invention, in the first invention, a peak voltage detection means for detecting a peak value of the voltage across the switching means, and an upper limit value setting means for setting an upper limit value of the output of the peak voltage detection means. The upper limit value setting means changes the upper limit value according to the output of the power supply frequency detection means, and the control means shortens the ON time of the switching means when the output value of the peak voltage detection means exceeds the upper limit value. Even if the input / output characteristics of the peak voltage detection means change depending on the power supply frequency, the upper limit value also changes according to the power supply frequency, and the upper limit value of the peak voltage of the switching means depends on the power supply frequency. Fluctuation can be suppressed.

  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 partially block circuit diagram of the rice cooker according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the pan 1 shows an equivalent circuit, and is composed of a laminated body using a plurality of metals through which magnetic flux passes. The heating coil 2 is magnetically coupled to the pan 1 so as to heat the pan 1. The heating coil 2 is composed of a wire obtained by twisting more than 20 litz wires in which a plurality of copper wires are bundled, and makes the current distribution uniform when a high-frequency current flows.

  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.

  In the present embodiment, the inverter means is constituted by the heating coil 2, the resonance capacitor 3, and the switching means 4, and supplies high frequency power to the heating coil 2.

  The AC power supply 5 supplies power to the rice cooker. The power supply frequency of the AC power supply 5 is 50 Hz in the eastern Japan region and 60 Hz in the western Japan region. The rectifying means 6 is constituted by a diode bridge 7, a choke coil 8, and a smoothing capacitor 9, and rectifies the AC power supply 5 to supply power to the inverter means. Here, the capacity of the smoothing capacitor 9 is as small as several μF, and when a high-frequency current is passed through the heating coil 2, ripple occurs. In the present embodiment, this ripple voltage is the same as the voltage of the AC power supply 5.

  The power supply frequency detection means 10 detects the frequency of the AC power supply 5 and is composed of a synchronization pulse generation means 11 and a pulse counter 12. The synchronization pulse generating means 11 is composed of a voltage dividing resistor that divides the AC power supply voltage and a transistor that is turned on / off in accordance with the output of the voltage dividing resistor, and outputs a high or low signal in synchronization with the power supply voltage waveform. The pulse counter 12 counts the number of pulses per predetermined time of the synchronization pulse generating means 11, and determines that 60 Hz is exceeded when the predetermined number of pulses is exceeded, and 50 Hz if it is less than the predetermined number of pulses.

  The input current detecting means 13 detects an input current supplied from the AC power source 5 and is composed of a current transformer 14, a resistor 15, a diode bridge 16, and an electrolytic capacitor 17, and an AC signal from the current transformer 14 is converted into a diode. It is converted into a DC signal by a rectifying / smoothing circuit comprising a bridge 16 and an electrolytic capacitor 17. The resistor 15 adjusts the output voltage value of the current transformer 14.

  The input current setting means 18 sets a value corresponding to the target value of the input current, and stores an 8-bit set value corresponding to a plurality of target values of the input current in advance in a ROM inside the microcomputer. An 8-bit set value corresponding to a predetermined target value is output for each condition such as the rice cooking process and the pan size.

  Here, the input current setting means 18 changes the value corresponding to the target value of the input current according to the frequency detected by the power supply frequency detection means 10.

  The control means 19 controls the on-time of the switching means 4 according to the output values of the input current detection means 13 and the input current setting means 18, and is constituted by an AD converter or a PWM generator inside the microcomputer. The output voltage of the input current detecting means 13 is received by an AD converter, and the high pulse width of the PWM generator is controlled so that the output value of the AD converter and the set value of the input current setting means 18 are the same. The driving means 20 is composed of 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 19 outputs a high pulse.

  FIG. 2 is a characteristic diagram showing the relationship between the input current Iin of the input current detection means 13 and the output voltage Vi. As shown in FIG. 2, the output voltage tends to be lower at 50 Hz even with the same input current. This is largely due to the input / output characteristics of the current transformer 14 and the charge / discharge characteristics of the electrolytic capacitor 17.

  In FIG. 2, Iref1 is the target value of the input current used in part of the rice cooking process. Viref 150 is a reference voltage corresponding to Iref1 set by the input current setting means 18 when the frequency of the AC power supply 5 is 50 Hz, and Viref 160 is a reference voltage corresponding to Iref1 when the frequency of the AC power supply 5 is 60 Hz. Iref2 and Viref250, Viref260, and Iref3 and Viref350 and Viref360 have the same relationship. In addition, Iref2 is a target value of the input current used in a part of the rice cooking process. Iref3 is a target value of the input current used in part of the rice cooking process and the heat retaining process.

  In the present embodiment, Viref 150 to Viref 360 set by the input current setting means 18 are output to the control means 19 as values Viref 150 (8 bits) to Viref 360 (8 bits) converted to 8 bits.

  As described above, in the rice cooker of the present embodiment, the reference voltage corresponding to the input currents Iref1 to Iref3 at the frequency of 50 Hz and 60 Hz of the AC power supply 5 in accordance with the input / output characteristics of the input current detection means 10. Viref 150 to Viref 360 can be set.

  The operation and action of the above configuration will be described. First, before starting a rice cooking process or a heat retention process, the power frequency detection means 10 detects the frequency of the AC power supply 5. At this time, if the frequency is 50 Hz, the input current setting means 18 outputs the 8-bit converted values of the reference voltages Viref 150, Viref 250, and Viref 350 for 50 Hz to the control means 19. The control means 19 controls the ON time of the switching means 4 so that the output voltage of the input current detection means 13 becomes these reference voltages.

  Similarly, when the frequency of the AC power supply 5 is 60 Hz, the power supply frequency detection means 10 detects the frequency of the AC flow power supply 5 as 60 Hz, and the input current setting means 18 has 8 bits of reference voltages Viref160, Viref260, and Viref360 for 60 Hz. The converted value is output to the control means 19. The control means 19 controls the ON time of the switching means 4 so that the output voltage of the input current detection means 13 becomes these reference voltages.

  As described above, since the input current setting means 18 changes the reference voltage in accordance with the frequency of the AC power supply 5, even if the input / output characteristics of the input current detection means 13 change due to the influence of the AC power supply frequency, the input current Fluctuations can be suppressed.

  As described above, in the present embodiment, the power supply frequency detection means 10 detects the frequency of the AC power supply 5, and the input current setting means 18 corresponds to the target value of the input current corresponding to the detected frequency. By changing the reference voltage, even if the input / output characteristics of the input current detection means 13 change in an area where the frequency of the AC power supply 5 is different, the reference voltage of the input current setting means 18 also corresponds to the frequency of the AC power supply 5. It will change, and it can control that the input current of a rice cooker varies between the areas where the frequency of AC power supply 5 differs.

  In this embodiment, the power supply frequency detection means 10 outputs a high or low signal in synchronization with the power supply waveform, and the pulse counter counts the number of pulses per predetermined time of the synchronization pulse generation means 11. However, the pulse width of the synchronization pulse generating means 11 may be detected and 50 Hz or 60 Hz may be determined based on the length. In this case, 50 Hz or 60 Hz can be determined in a shorter time than the method of counting the number of pulses, but the probability of erroneous determination due to external noise increases. In any case, the power source frequency detection means 10 is not particularly limited to the above configuration as long as it can determine whether the frequency of the AC power source 5 is 50 Hz or 60 Hz.

  Further, in the present embodiment, the input current detection means 13 is configured to rectify the output of the current transformer 14 and output it as a DC voltage, but a resistor may be used instead of the current transformer 14. When using resistors, compared to the method using the current transformer 14, there are many types of variation tolerances, and it is easy to use resistors with small variations. However, since a large current flows, it is necessary to pay attention to heat generation of the resistors.

(Embodiment 2)
FIG. 3 is a partially block circuit diagram of the rice cooker according to the second embodiment of the present invention.

  As shown in FIG. 3, the power supply voltage detection means 31 detects the voltage of the AC power supply 5, and is composed of a voltage dividing circuit composed of a plurality of resistors and a peak hold circuit for peak holding the output of the voltage dividing circuit. ing. The peak hold circuit includes an emitter follower circuit using a transistor, an electrolytic capacitor, and a discharge resistor that discharges the electrolytic capacitor.

  The power supply voltage setting means 32 sets the reference value of the output of the power supply voltage detection means 31, and stores the reference value for the power supply frequency 50Hz and the reference value for 60Hz in advance in the ROM inside the microcomputer. The reference value is changed according to the output of the frequency detection means 10. The input current setting means 33 is configured to change the target value of the input current based on the difference between the output value of the power supply voltage detection means 31 and the reference value of the power supply voltage setting means 32. Other configurations are the same as those of the first embodiment, and the same reference numerals are given and description thereof is omitted.

  FIG. 4 is a characteristic diagram showing the relationship between the input voltage Vin and the output voltage Vout of the power supply voltage detection means 31. The input voltage Vin is an effective voltage of the AC power supply 5. As shown in FIG. 4, even if the power supply voltage is the same, the output voltage of 50 Hz tends to be lower. This is because the discharge time of the electrolytic capacitor is longer at 50 Hz.

  In FIG. 4, Vinref is a reference for the AC power supply 5. In the rice cooker of the present embodiment, Vinref is an effective voltage of 100V. Voutref50 is a reference value corresponding to Vinref when the power supply frequency is 50 Hz. Voutref60 is a reference value corresponding to Vinref when the power supply frequency is 60 Hz.

  In this embodiment, Voutref50 and Voutref60 set by the power supply voltage setting means 32 are output to the input current setting means 33 as values Voutref50 (8 bits) and Voutref60 (8 bits) converted into 8 bits.

  As described above, in the rice cooker of the present embodiment, the reference value corresponding to the reference Vinref of the power supply voltage at the frequency of 50 Hz and 60 Hz of the AC power supply 5 in accordance with the input / output characteristics of the power supply voltage detection means 31. Voutref50 and Voutref60 can be set.

  The operation and action of the above configuration will be described. First, before starting a rice cooking process or a heat retention process, the power frequency detection means 10 detects the frequency of the AC power supply 5. At this time, if the frequency is 50 Hz, the input current setting means 33 sets 8-bit converted values of the reference voltages Viref 150, Viref 250, and Viref 350 for 50 Hz as initial values. The power supply voltage setting means 32 sets a reference value Voutref 50 and outputs this 8-bit converted value to the input current setting means 33. The power supply voltage detection means 31 converts the voltage value Vout corresponding to the AC power supply voltage into 8 bits via an AD converter in the microcomputer and outputs it to the input current setting means 33. The input current setting means 33 calculates the difference between Voutref50 and Vout as shown in the following equation, and changes the reference voltage output to the control means 19 based on this difference.

Viref150 = Viref150 + α × (Voutref50−Vout)
Here, α is a coefficient, which is determined by the characteristics of the microcomputer constituting the pan 1, the heating coil 2, the resonance capacitor 3, the control means 19, and the like.

  The control means 19 controls the ON time of the switching means 4 so that the output voltage of the input current detection means 13 becomes these reference voltages. As a result, when the voltage of the AC power supply 5 is higher than 100V, the target value of the input current is lowered. Conversely, when the voltage of the AC power supply 5 is lower than 100V, the target value of the input current is increased. Can work with.

  Here, as an example, Viref 150 is used as the reference voltage set by input current setting means 33, but Viref 250 and Viref 350 are similarly changed.

  When the frequency of the AC power supply 5 is 60 Hz, the input current setting means 33 sets 8-bit converted values of the reference voltages Viref 160, Viref 260, and Viref 360 for 60 Hz as initial values. The power supply voltage setting means 32 sets a reference value Voutref 60 and outputs this 8-bit converted value to the input current setting means 33. Since the subsequent operation is the same as that at 50 Hz, it is omitted here.

  As described above, in the present embodiment, the power supply voltage detection means 31 that detects the voltage of the AC power supply 5 and the power supply voltage setting means 32 that changes the reference value according to the frequency of the AC power supply 5 are added to the input current. The setting means 33 changes the target value of the input current according to the difference between the output of the power supply voltage detection means 31 and the reference value, so that the input current detection means 13 and the power supply voltage detection means 31 are different in regions where the frequency of the AC power supply 5 is different. Even if the input / output characteristics change, the power supply voltage setting means 32 and the input current setting means 33 set a reference value corresponding to the characteristics, so that the variation in the input power between regions where the frequency of the AC power supply 5 is different. Can be small.

(Embodiment 3)
FIG. 5 is a partial block diagram of the rice cooker according to Embodiment 3 of the present invention.

  As shown in FIG. 5, the peak voltage detecting means 51 detects the peak value of the voltage across the switching means 4, and a voltage holding circuit comprising a plurality of resistors and a peak hold for peak holding the output of the voltage dividing circuit. It consists of a circuit. The peak hold circuit includes an emitter follower circuit using a transistor, an electrolytic capacitor, and a discharge resistor that discharges the electrolytic capacitor.

  The upper limit value setting means 52 sets the upper limit value of the output of the peak voltage detection means 51. The reference value for the power frequency 50 Hz and the upper limit value for 60 Hz are stored in advance in the ROM inside the microcomputer. The upper limit value is changed according to the output of the frequency detection means 10. The control means 53 is configured to shorten the ON time of the switching means 4 when the output value of the peak voltage detection means 51 is larger than the upper limit value of the upper limit value setting means 52. Other configurations are the same as those of the first embodiment, and the same reference numerals are given and description thereof is omitted.

  FIG. 6 is a characteristic diagram showing the relationship between the input voltage Vci and the output voltage Vco of the peak voltage detecting means 51. Here, the input voltage Vci indicates the peak value of the voltage across the switching means 4. The peak value indicates a peak value in one cycle of the AC power supply 5. As shown in FIG. 6, even if the power supply voltage is the same, the output voltage of 50 Hz tends to be lower. This is because the discharge time of the electrolytic capacitor is longer at 50 Hz.

  In FIG. 6, Vciref indicates the upper limit value of the voltage across the switching means 4. If this upper limit is around the peak value of the voltage at both ends in the rice cooking process of the rice cooker and the center value of the absolute maximum rating of the IGBT constituting the switching means 4, malfunction does not occur even if circuit parts vary. In this embodiment, Vciref is 850V. Vcoref50 is a value output with respect to the input of Vciref when the power supply frequency is 50 Hz. Vcoref60 is a value output to the input of Vciref when the power supply frequency is 60 Hz. When Vciref is set as the upper limit value of the voltage across the switching means 4, Vcoref 50 and Vcoref 60 are the upper limit values set by the upper limit value setting means 52.

  In the present embodiment, Vcoref50 and Vcoref60 set by the upper limit value setting unit 52 are converted to 8-bit values Vcoref50 (8 bits) and Vcoref60 (8 bits) and output to the control unit 53.

  As described above, in the rice cooker according to the present embodiment, the values Vcoref50 and Vcoref60 corresponding to Vciref can be set as the upper limit values at the frequency 50 Hz and 60 Hz of the AC power supply 5, respectively.

  FIG. 7 shows an internal block diagram of the control means 53. As shown in FIG. 7, the first calculation means 71 is constituted by a microcomputer, and the difference between any one of the output values Viref 150 to Viref 360 of the input current setting means 18 and the output value Vi of the input current detection means 13. dVi is calculated and the result is output to the on-time change amount setting means 73. Note that when Vi is larger, dVi takes a negative value.

  Similarly to the first calculation means 71, the second calculation means 72 is constituted by a microcomputer, and one of the output values Vcoref 50 and Vcoref 60 of the upper limit value setting means 52 and the output value of the peak voltage detection means 51. A difference dVco of Vco is calculated, and the result is output to the on-time change amount setting means 73. If Vco is larger, dVco has a negative value.

  The on-time change amount setting means 73 is constituted by a data table stored in a ROM inside the microcomputer. When the calculation results are input from the first calculation means 71 and the second calculation means 72, the on-time change amount setting means 73 sets an on-time change amount dTon corresponding to the calculation result condition from the data table. Set. Note that the data table of the present embodiment is configured such that dTon indicates a negative value when either dVi or dVco is a negative value.

  The on-time calculating means 74 adds the change amount dTon to the previous on-time Ton and outputs the new on-time Ton to the PWM means 75. The PWM means 75 outputs a high pulse to the driving means 20 during the ON time Ton.

  The operation and action of the above configuration will be described. First, before starting a rice cooking process or a heat retention process, the power frequency detection means 10 detects the frequency of the AC power supply 5. At this time, if the frequency is 50 Hz, the input current setting means 18 sets 8-bit converted values of the reference voltages Viref 150, Viref 250, and Viref 350 for 50 Hz as initial values. The upper limit value setting means 52 sets the reference value Vcoref 50 and outputs this 8-bit converted value to the control means 53. The peak voltage detection means 51 converts Vco into 8 bits via an AD converter in the microcomputer and outputs it to the control means 53.

  The control unit 53 calculates the difference dVco between the output value Vco of the peak voltage detection unit 51 and the upper limit value Vcoref50, and calculates the difference dVi between the output value Vi of the input current detection unit 13 and the output value Viref150 of the input current setting unit 18. . The on-time change amount setting unit 73 calls the on-time change amount dTon that meets the conditions of dVco and dVi from the data table. The on-time calculation means 74 adds dTon to the current on-time Ton, outputs it as a new on-time Ton to the PWM means 75, and outputs a high pulse from the PWM means 75 during the period Ton.

  As described with reference to FIG. 7, dTon is set to a negative value when dVi or dVco is a negative value. That is, when either the input current or the peak voltage exceeds the reference value, the on-time is shortened.

  When the frequency of the AC power supply 5 is 60 Hz, the input current setting unit 18 sets 8-bit converted values of the reference voltages Viref 160, Viref 260, and Viref 360 for 60 Hz as initial values. The upper limit value setting means 52 sets the reference value Vcoref 60 and outputs this 8-bit converted value to the control means 53. Since the subsequent operation is the same as that at 50 Hz, it is omitted here.

  As described above, in the present embodiment, the peak voltage detecting means 51 for detecting the peak value of the voltage across the switching means 4 and the upper limit setting means 52 for changing the upper limit value according to the frequency of the AC power supply 5 are provided. In addition, when the output value of the peak voltage detecting means 51 exceeds the upper limit value by the control means 53, the input / output characteristics of the peak voltage detecting means 51 change in regions where the frequency of the AC power supply 5 is different by shortening the ON time. Even so, since the upper limit value corresponding to the characteristic changed by the upper limit value setting means 52 is set, it is possible to prevent the upper limit value of the voltage across the switching means 4 from varying between regions where the frequency of the AC power supply 5 is different. Can do.

As described above, the rice cooker according to the present invention can suppress variations in input power between regions where the frequency of the AC power supply is different, so that the heating coil by the inverter means that rectifies the AC power supply and supplies the power. It is useful as a rice cooker that supplies high frequency power to the pot and heats the pan.

The circuit diagram which made the partial block diagram of the rice cooker of Embodiment 1 of this invention Characteristic diagram showing the relationship between the input current and output voltage of the input current detection means of the rice cooker The circuit diagram which made the block diagram of the rice cooker of Embodiment 2 of this invention Characteristic diagram showing the relationship between the input voltage and output voltage of the power supply voltage detection means of the rice cooker The circuit diagram which made the block diagram of the rice cooker of Embodiment 3 of this invention Characteristic diagram showing the relationship between the input voltage and output voltage of the peak voltage detection means of the rice cooker Internal block diagram of the control means of the rice cooker Partial block diagram of a conventional rice cooker

Explanation of symbols

1 pan 2 heating coil (inverter means)
3 Resonance capacitor (inverter means)
4 Switching means (inverter means)
5 AC power supply 6 Rectifying means 10 Power frequency detecting means 13 Input current detecting means 18 Input current setting means 19 Control means

Claims (2)

A heating coil for heating the pan; inverter means for supplying high-frequency power to the heating coil; switching means for constituting the inverter means; rectifying means for rectifying an AC power supply and supplying power to the inverter means; and the AC power supply Power supply frequency detection means for detecting the frequency of the power supply, power supply voltage detection means for detecting the power supply voltage of the AC power supply, power supply voltage setting means for setting a reference value of the output of the power supply voltage detection means, and supply from the AC power supply Input current detecting means for detecting the input current, input current setting means for setting a reference voltage value corresponding to the target value of the input current , output value of the input current detecting means , and reference of the input current setting means and control means for controlling the on-time of said switching means in response to a voltage value, the power supply voltage detecting means, the power supply frequency detecting means Change the reference value in response to a force, the input current setting means, according to the frequency of the power supply frequency detecting unit detects, with changing the reference voltage value, wherein an output of the power supply voltage detection means reference The rice cooker which changed the said reference voltage value according to the difference of a value . A peak voltage detection means for detecting the peak value of the voltage across the switching means; and an upper limit value setting means for setting an upper limit value of the output of the peak voltage detection means, wherein the upper limit value setting means is a power supply frequency detection means. 2. The rice cooker according to claim 1, wherein the upper limit value is changed in accordance with the output, and the control means shortens the on-time of the switching means when the output value of the peak voltage detection means exceeds the upper limit value.

Images