JP4929194B2 - Induction heating cooker - Google Patents

Description

  The present invention relates to an induction heating cooker capable of induction heating both a high resistance load such as an iron pan and a low resistance load such as an aluminum pan.

  Conventionally, as an induction heating cooker capable of induction heating both an iron pan as a high resistance load and an aluminum pan as a low resistance load, an inverter that supplies a high frequency voltage to a heating coil, and a commercial single-phase AC power source for this inverter A boost chopper provided with a smoothing capacitor consisting of an electrolytic capacitor on the output side is provided between the DC power supply circuit for converting the voltage into a DC power supply voltage, and the DC voltage supplied to the inverter along with the drive frequency of the inverter is provided. Also, a configuration is disclosed in which the power is controlled according to the load and controlled to the set thermal power (see, for example, Patent Document 1).

Low resistance loads such as aluminum pans tend to generate electromagnetic noise due to the repulsive force of electromagnetic induction, so the inverter input voltage can be stabilized to eliminate the inverter current fluctuation in the cycle of commercial single-phase AC power supply voltage. In the case of Patent Document 1, the step-up chopper has an action of stably converting the input voltage of the inverter to eliminate the inverter current fluctuation in the cycle of the commercial single-phase AC power supply voltage.
JP 2006-140088 A

  According to the conventional configuration, the input voltage of the inverter can be stably converted to a direct current by a boost chopper including a smoothing capacitor. However, if the smoothing capacitor deteriorates due to frequent cooking and the life is exhausted, the function of the smoothing capacitor is reduced. Therefore, there is a problem that ripple voltage is generated by the smoothing capacitor itself.

  This invention is made | formed in view of the said situation, The objective is to provide the induction heating cooker which can judge and alert | report the lifetime of the smoothing capacitor of a pressure | voltage rise chopper.

The induction heating cooker of the present invention includes a heating coil for induction heating, a DC power supply circuit that converts an AC power supply voltage into a DC voltage, and boosts the DC voltage from the DC power supply circuit and smoothes it with a smoothing capacitor. A step-up chopper for obtaining a step-up DC voltage, an inverter for converting the step-up DC voltage from the step-up chopper into a high-frequency voltage and supplying the voltage to the heating coil, a control means for controlling the step-up chopper and the inverter, and the step-up DC voltage The DC voltage detecting means to detect and the unit DC ripple of the boosted DC voltage detected by the DC voltage detecting means are detected, and the life of the smoothing capacitor is judged by comparing the ripple with a set ripple threshold value. Te, comprising a ripple voltage comparator means for notifying the fact of life informing means, the control means, prior to cooking operation start, the boost Cho And wherein the operating the ripple voltage comparator means while stopping the operation of the path.

According to the induction heating cooker of the present invention, when the smoothing capacitor deteriorates, the ripple of the boost DC voltage increases. Therefore, by detecting this ripple and comparing the ripple with the ripple threshold value, Since the service life is determined and the notification means is notified when the service life is determined, the user can be easily notified that the service life of the smoothing capacitor is exhausted. In addition, since the control means operates the ripple voltage comparison means in a state where the operation of the boost chopper is stopped before the cooking operation is started, the user is required to start the cooking operation when the life of the smoothing capacitor is exhausted. Is practically convenient.

The first embodiment of the present invention will be described below with reference to FIGS.
FIG. 1 shows the configuration of the electric circuit of this embodiment. In FIG. 1, a full-wave rectifier circuit 1 constitutes a DC power supply circuit 3 together with a smoothing capacitor 2 made of an electrolytic capacitor, and an AC input terminal thereof is 200 V via AC power supply lines 4 and 5 and a noise filter 6. Are connected to a commercial single-phase AC power source 7. In the full-wave rectifier circuit 1, the positive output terminal is connected to one terminal of the smoothing capacitor 2 via the reactor 8 and the high speed diode 9, and the negative output terminal is connected to the other terminal of the smoothing capacitor 2. Yes. The NPN transistor 10 constitutes a step-up chopper 11 that is a DC voltage variable means together with the reactor 8, the high-speed diode 9, and the smoothing capacitor 2, and its collector is connected to a common connection point of the reactor 8 and the high-speed diode 9. The emitter is connected to the negative output terminal of the full-wave rectifier circuit 1. The DC power supply lines 12 and 13 are connected to both terminals of the smoothing capacitor 2.

  The inverter 14 is composed of a single-phase full bridge circuit, and is the same as the series circuit (first arm) of the first IGBT 15 and the second IGBT 16 which are switching elements connected between the DC power supply lines 12 and 13. , And a series circuit (second arm) of a third IGBT 17 and a fourth IGBT 18 which are switching elements connected between the DC power supply lines 12 and 13. Free wheel diodes 15a, 16a, 17a and 18a are connected between the collectors and emitters of the IGBTs 15, 16, 17 and 18, respectively. Snubber capacitors 19 and 20 are connected between the collectors and emitters of the second IGBT 16 and the fourth IGBT 18.

  Heating for heating the pan 21 as a load between the neutral point of the series circuit of the first IGBT 15 and the second IGBT and the neutral point of the series circuit of the third IGBT 17 and the fourth IGBT 18 A series circuit of a coil 22 and a first resonance capacitor 23 is connected, and a series circuit of a second resonance capacitor 24 and a switching relay switch 25 is connected in parallel to the first resonance capacitor 23. A resonance circuit 26 is configured. In this case, the number of turns of the heating coil 22 is set to 60 turns, the capacity C23 of the first resonant capacitor 23 is set to a capacity used when heating the aluminum pan as a low resistance load, and the capacity C24 is set as a high resistance load. The capacity used for heating the iron pan is set so that the capacity C24 is sufficiently larger than the capacity C23.

  The control circuit 27 as a control means is composed of a high-speed microcomputer, for example, a 32-bit RISC microcomputer or a DSP microcomputer. As shown in a functional block diagram, the input power control unit 28 and the load as load determination means. A determination unit 29, an inverter voltage variable unit 30, an inverter drive pulse generation unit 31, and a ripple voltage comparison unit 41 as ripple voltage comparison means are provided. The operation display unit 42 that also serves as a notification unit gives commands such as start, stop, and thermal power setting to the input power control unit 28 based on a user's operation, and performs status display, life notification, other display, and notification. It comes to let you.

  The input voltage detection circuit 32 detects an AC input voltage VAC between the AC power supply lines 4 and 5, and supplies the detected AC input voltage to the input power control unit 28 and the ripple voltage comparison unit 41. The input current detection circuit 33 detects an AC input current via a current transformer 34 and supplies the detected AC input current to the input power control unit 28 and the load determination unit 29.

  The inverter current detection circuit 35 detects the current flowing through the inverter 14 via the current transformer 36 and supplies the detected inverter current to the load determination unit 29. The DC voltage detection circuit 43 serving as DC voltage detecting means detects the boosted DC voltage VDC by the boost chopper 11 as the terminal voltage of the smoothing capacitor 2 and supplies the detected boosted DC voltage to the ripple voltage comparison unit 41. .

  The input power control unit 28 refers to the AC input voltage detected by the input voltage detection circuit 32 and the determination result determined by the load determination unit 29, and outputs a signal corresponding to the inverter voltage set for the inverter voltage variable unit 30. The inverter voltage variable section 30 outputs an inverter voltage setting signal to boost the chopper 11 and supplies it to the chopper control section 37 as control means. The chopper control unit 37 is configured by an IC chip separately from the control circuit 27, and generates a base signal based on a given inverter voltage setting signal and gives it to the base of the transistor 10 via the driver 38. Thus, the boost chopper 11 applies the set boost DC voltage VDC between the DC power supply lines 12 and 13. The step-up chopper 11 is controlled so that the waveform of the AC input current detected by the input current detection circuit 33 follows the waveform of the AC input voltage detected by the input voltage detection circuit 32 simultaneously with the step-up operation. It also works as a rate improvement chopper.

  The load determination unit 29 determines the type of the pan 21 from the AC input current detected by the input current detection circuit 33 and the inverter current detected by the inverter current detection circuit 35, and the determination signal is input power control. The unit 28 and the inverter drive pulse generation unit 31 are provided. Further, the load determining unit 29 turns off the switching relay switch 25 via the relay switching circuit 39 when the pan 21 is determined to be an aluminum pan, and the relay switching circuit when the pan 21 is determined to be an iron pan. The switching relay switch 25 is turned on via 39.

  As will be described later, the ripple voltage comparison unit 41 detects the step-up DC voltage VDC via the DC voltage detection circuit 43 to detect the ripple (variation), and based on this, determines the life of the smoothing capacitor 2, When it is determined that the service life is reached, a service life determination signal is output and supplied to the input power control unit 28 and the operation display unit 42. When the life display signal is given from the ripple voltage comparison unit 41, the operation display unit 42 causes the appropriate notification means to perform the life notification.

  The input power control unit 28 calculates the input power from the AC input voltage detected by the input voltage detection circuit 32 and the AC input current detected by the input current detection circuit 33 so that the set input power set by the user is obtained. A frequency command signal for controlling the drive frequency (switching frequency) of the inverter 14 is supplied to the inverter drive pulse generator 31. The frequency command signal generator 31 (actually a high-speed microcomputer as the control circuit 27) has U-phase, V-phase and W-phase PWM ports for a three-phase inverter that drives a three-phase motor. Based on the frequency command signal from the unit 28 and taking the determination of the load determination unit 29 into account, a drive pulse as a PWM signal is generated and given to the driver 40. The driver 40 outputs a gate signal and supplies it to the gates of the IGBTs 15 to 18.

  The input power control unit 28 stops the boost chopper 11 and the inverter 14 when a life determination signal is given from the ripple voltage comparison unit 41. However, this function may be selectable. .

Next, the operation of the present embodiment will be briefly described. If a detailed description is necessary, refer to Patent Document 1.
When the cooking operation is stopped, the switching relay switch 25 is turned off. Accordingly, in the resonance circuit 26, the heating coil 22 and the first resonance capacitor 23 are connected in series. In this case, the capacitance C23 of the first resonance capacitor 23 is set to a value such that the resonance frequency is near 59 kHz when the number of turns of the heating coil 22 is 60 turns.

  When the user sets input power (thermal power) on the operation display unit 42 and operates the start button, the control circuit 27 first determines the type (material) of the pan 21. The input power control unit 28 gives a gate signal to the IGBTs 15 to 18 through the inverter drive pulse generation unit 31 and the driver 40 to drive the inverter 14 at a switching frequency of 65 kHz, and then gradually decreases the switching frequency. Then, when the switching frequency of the inverter 14 reaches 63 kHz, the load determination unit 29 determines the type of the pan 21 from the AC input current and the inverter current. That is, when the inverter 14 is driven at a switching frequency of 63 kHz, this is the specification of an aluminum pan. When the pan 21 is an aluminum pan, the AC input current and the inverter current are both specified currents. When the pot 21 is an iron pot, both the AC input current and the inverter current are significantly smaller than the respective specified currents or hardly flow. Thereby, the load determination unit 29 gives the determination result to the inverter drive pulse generation unit 31.

  When the pan 21 is an aluminum pan, the load determination unit 29 keeps the switching relay switch 25 off, and the inverter drive pulse generation unit 31 refers to the determination result of the load determination unit 29 to make a three-phase operation. A drive pulse for an appropriate two pairs of switching elements out of six, that is, three pairs of switching elements constituting a three-phase inverter for driving the motor is given to the driver 40. As a result, a gate signal corresponding to the drive pulse is output from the driver 40 and applied to the gates of the IGBTs 15, 16, 17, and 18. The high-frequency voltage output from the inverter 14 is twice the switching frequency of the inverter 14. Thus, the inverter current also has a double frequency. In the present embodiment, the frequency of the inverter current when the aluminum pan is heated at 2 kW is set to 60 kHz as in the conventional case, but in this case, the switching frequency of the inverter 14 is half, 30 kHz. In this case, the boosted DC voltage VDC is boosted to 320 V by the boost chopper 11.

  When the pan 21 is an iron pan, the load determination unit 29 turns on the switching relay switch 25. When the switching relay switch 25 is turned on, the resonance circuit 26 becomes a series circuit of the heating coil 22 and the parallel circuit of the first resonance capacitor 23 and the second resonance capacitor 24, and the resonance capacitor capacity is C23 + C24. Since the capacity C24 is sufficiently larger than the capacity C23, it is almost C24. The capacitance C24 is set to a value such that the resonance frequency when the number of turns of the heating coil 22 is 60 turns is 22 kHz.

  The inverter drive pulse generation unit 31 refers to the determination result of the load determination unit 29, and is used for appropriate two pairs of switching elements among six, that is, three pairs of switching elements that constitute a three-phase inverter that drives a three-phase motor. Is supplied to the driver 40. As a result, a gate signal corresponding to the drive pulse is output from the driver 40 and applied to the gates of the IGBTs 15, 16, 17, and 18. The high-frequency voltage output from the inverter 14 is the same as the switching frequency of the inverter 14. The inverter current has the same frequency. In this embodiment, the switching frequency of the inverter 14 is set to 25 kHz, and therefore the frequency of the high frequency voltage and the inverter current is also 25 kHz. Also in the case of this iron pan, the number of turns of the heating coil 22 is 60 turns, but the resonance circuit 26 (series circuit of the heating coil 22 and the second capacitor 24) has an amplitude twice that of the heating of the aluminum pan. Since a high frequency voltage having (VDC × 2) can be applied, a sufficient inverter current can be passed through the heating coil 22 and high heating power heating can be performed. When a high heating power of 3 kW is obtained during the heating of the iron pan, the boosted DC voltage VDC is boosted to 400 V, for example, by the boost chopper 11.

Now, the life judgment operation of the smoothing capacitor 2 will be described with reference to FIGS.
The control circuit 27 determines the life of the smoothing capacitor 2 during the above-described cooking operation. That is, the DC voltage detection circuit 43 detects the boosted DC voltage VDC, which is the terminal voltage of the smoothing capacitor 2, but the ripple voltage comparison unit 41 uses a plurality of cycles of the AC input voltage VAC, for example, 5 cycles as a unit of DC voltage. The boosted DC voltage VDC is sampled and detected a predetermined number of times through the detection circuit 43, the average of the detected values is calculated, the deviation from the average of each detected value detected by sampling is calculated, and the variance (2 of each deviation is calculated). The sum of the powers divided by the number of data) is calculated, and the standard deviation (ripple) is calculated by taking the square root of the variance.

  In the ripple voltage comparison unit 41, ripple thresholds σa and σb having different values are set in advance as shown in FIGS. 2 and 3 in order to determine the life of the smoothing capacitor 2. The ripple threshold value σa shown in FIG. 2 is for setting when the pot 21 is an aluminum pan, for example, and the boost DC voltage VDC is not so high as 320V. The ripple threshold value σb shown in FIG. This is for setting when the boosted DC voltage VDC is relatively high, such as 400 V, as in an iron pan.

  Thus, when the pot 21 is an aluminum pot, the ripple voltage comparison unit 41 compares the calculated standard deviation with the ripple threshold σa, and when the standard deviation exceeds the ripple threshold σa, the smoothing capacitor 2 When the pan 21 is an iron pan, the calculated standard deviation is compared with the ripple threshold σb, and when the standard deviation exceeds the ripple threshold σb, the smoothing capacitor 2 is determined (life is exhausted) and a life determination signal is output and provided to the input power control unit 28 and the operation display unit 42. Thereby, the input power control unit 28 stops the operation of the step-up chopper 11 and the inverter 14, and the operation display unit 42 notifies the notification means of the end of life.

  Here, when the pot 21 is not as high as 320 V, such as an aluminum pot, the AC voltage is input to the boost DC voltage VDC as the terminal voltage of the smoothing capacitor 2 as shown in FIG. The ripple of the cycle of the voltage VAC is not superimposed, but when the pot 21 is relatively high such as an iron pot and the boost DC voltage VDC is 400 V, the time for storing energy in the reactor 8 of the boost chopper 11, that is, the IGBT 16 Since the on-time is longer than that in the case of the aluminum pan, as shown in FIG. 3, a ripple component of the period of the AC input voltage VAC is easily superimposed on the boosted DC voltage VDC that is the terminal voltage of the smoothing capacitor 2.

  Therefore, in this embodiment, the ripple threshold value σb for the iron pan is set to be larger (σb> σa) than the ripple threshold value σa for the aluminum pan in consideration of the ripple overlap. Specifically, in the present embodiment, the ripple threshold value (σ) is set to be larger in accordance with the magnitude of the boosted DC voltage VDC boosted by the boost chopper 11, that is, as the boosted DC voltage VDC increases. ing.

  Since the smoothing capacitor 2 is not deteriorated rapidly in a short time, the smoothing capacitor 2 may be determined once in the heating cooking operation. It may be.

  On the other hand, in the present embodiment, as described above, the life of the smoothing capacitor 2 is determined during the cooking operation, but it is also performed before the cooking operation is started. The operation will be described below with reference to FIG.

  When the cooking operation is set in the operation display magnetic unit 42, the control circuit 27 performs the following operation before starting the set cooking operation. First, the control circuit 27 puts the step-up chopper 11 into an operation stop state. Therefore, the boosted DC voltage VDC, which is the terminal voltage of the smoothing capacitor 2, is 282V obtained by full-wave rectification of the 200V AC input voltage VAC, and the boost chopper 11 is not operated. As shown in FIG. 4, the ripple of the cycle of the AC input voltage VAC is largely superimposed.

  The ripple voltage comparison unit 41 samples and detects the boosted DC voltage VDC a predetermined number of times through the power flow voltage detection circuit 43 with a plurality of periods of the AC power input voltage VAC, for example, five periods as one unit, and performs a standard deviation ( Ripple) is calculated. Then, the ripple voltage comparison unit 41 compares the calculated standard deviation with the ripple threshold σc for operation stop, and when the standard deviation exceeds the ripple threshold σc, the life of the smoothing capacitor 2 (life is exhausted). The service life determination signal is output to the input power control unit 28 and the operation display unit 42. As a result, the operation display unit 42 notifies the notification means of the end of life, and the input power control unit 28 keeps the operations of the boost chopper 11 and the inverter 14 stopped.

  The ripple voltage comparison unit 41 compares the calculated standard deviation with the operation stop ripple threshold value σc, and determines that the life of the smoothing capacitor 2 has not expired when the standard deviation is equal to or less than the ripple threshold value σc. The control circuit 27 executes the set cooking operation.

  As described above, according to the present embodiment, the ripple voltage comparison unit 41 performs sampling detection of the boosted DC voltage VDC through the power flow voltage detection circuit 43 with 5 cycles of the AC power input voltage VAC as one unit during the cooking operation. Based on this, the standard deviation (ripple) is calculated, and the calculated standard deviation is compared with the ripple threshold σa for the aluminum pan or the ripple threshold σb for the iron pan to determine the life of the smoothing capacitor 2. When it is determined that the service life has been reached, the operation display unit 42 is notified that the life of the smoothing capacitor 2 has expired. As a result, the user can know that the smoothing capacitor 2 needs to be replaced and can ask the dealer to do so.

  Further, since the ripple threshold value σa for the aluminum pan and the ripple threshold value σb for the iron pan are set as the ripple threshold values for determining the life of the smoothing capacitor 2, specifically, the boost DC voltage that the boost chopper 11 boosts the ripple threshold value. Since the setting is made according to the magnitude of VDC, the life of the smoothing capacitor 2 can be reliably determined in consideration of the ripple of the period of the AC input voltage VAC superimposed on the boosted DC voltage VDC.

  Further, the control circuit 27 determines the life of the smoothing capacitor 2 before starting the set cooking operation when the cooking operation is set in the operation display magnetic unit 42. When the life of the capacitor 2 is exhausted, the user can be notified before starting the cooking operation, which is practically convenient.

  In the first embodiment, the ripple voltage comparison unit 41 performs sampling detection of the boosted DC voltage VDC through the power flow voltage detection circuit 43 with 5 periods of the AC power input voltage VAC as one unit during the cooking operation. Then, based on this, the standard deviation (ripple) is calculated and the life of the smoothing capacitor 2 is determined. Alternatively, the following may be used.

  The boosted DC voltage VDC is sampled and detected based on 5 cycles of the AC input voltage VAC as a unit, and the standard deviation (ripple) is calculated based on this sampling multiple times (for example, 5 times). May be calculated, and the calculated average value may be compared with the ripple threshold value to determine the life of the smoothing capacitor.

  The boosted DC voltage VDC is sampled and detected based on 5 cycles of the AC input voltage VAC as a unit, and the standard deviation (ripple) is calculated based on this sampling multiple times (for example, 5 times). Each time the smoothing capacitor life is judged by comparing the calculated standard deviation with the ripple threshold, the counter is counted up every time it is judged to be the life, and the life is notified when the count value reaches the set value. You may do it.

  The boosted DC voltage VDC is sampled and detected based on 5 cycles of the AC input voltage VAC as a unit, and the standard deviation (ripple) is calculated based on this sampling multiple times (for example, 5 times), and the plurality of standard deviations are calculated. The average value of the smoothing capacitor is calculated several times (for example, five times), and the average value calculated every time the average value is calculated is compared with the ripple threshold value to determine the life of the smoothing capacitor. Alternatively, the counter may be counted up to notify the end of life when the count value reaches the set value.

FIGS. 5 and 6 show a second embodiment of the present invention. The same parts as those in the above embodiment are indicated by the same reference numerals, and different parts will be described below.
The control circuit 27 includes a high frequency ripple voltage comparison unit 44 that is a high frequency ripple voltage comparison unit having the same function as the ripple voltage comparison unit 41, and detects the AC input voltage VAC between the AC power supply lines 4 and 5. The detected AC input voltage of the input voltage detection circuit 32 is applied. The high-frequency ripple detection circuit 45, which is a high-frequency ripple detection means, consists of a differentiation circuit or a high-pass filter, and detects a high-frequency ripple component superimposed on the boosted DC voltage VDC. The ripple voltage comparison unit 44 is provided. In the high frequency ripple voltage comparison unit 44, a high frequency ripple threshold σd is set.

  As will be described later, the high-frequency ripple voltage comparison unit 44 detects the high-frequency ripple voltage VR, detects the ripple (fluctuation), determines the life of the smoothing capacitor 2 based on this, and determines the life when it is determined as the life. A signal is output and provided to the input power control unit 28 and the operation display unit 42. The operations of the input power control unit 28 and the operation display unit 42 are the same as described above.

  Thus, when the smoothing capacitor 2 is deteriorated and its function is reduced, the smoothing characteristic is changed and a harmonic component is generated in the boosted DC voltage VDC. As shown in FIG. The harmonic component of the boosted DC voltage VDC is detected as a high frequency ripple voltage VR, and the detected high frequency ripple voltage VR is supplied to the voltage high frequency ripple voltage comparison unit 44. The high frequency ripple voltage comparison unit 44 samples and detects the high frequency ripple voltage VR detected by the high frequency ripple detection circuit 45 a predetermined number of times during a cooking operation, with a plurality of periods of the AC input voltage VAC, for example, five periods as one unit. Calculate the average of the detected values, calculate the deviation from the average of the detected detection values sampled, calculate the variance (the sum of the square of each deviation divided by the number of data) from these deviations, The standard deviation (ripple) is calculated by taking the square root.

  The high frequency ripple voltage comparison unit 44 compares the calculated standard deviation with the high frequency ripple threshold σd and determines that the life of the smoothing capacitor 2 (life is exhausted) when the standard deviation exceeds the high frequency ripple threshold σd. A determination signal is output and provided to the input power control unit 28 and the operation display unit 42. Thereby, the input power control unit 28 stops the operation of the step-up chopper 11 and the inverter 14, and the operation display unit 42 notifies the notification means of the end of life.

  Since the smoothing capacitor 2 is not deteriorated rapidly in a short time, the smoothing capacitor 2 may be determined once in the heating cooking operation. It may be.

  According to the second embodiment, since the life of the smoothing capacitor 2 is judged by both the ripple voltage comparison unit 41 and the high frequency ripple voltage comparison unit 44, the life of the smoothing capacitor 2 can be judged more reliably. be able to.

  In the second embodiment, the high-frequency ripple voltage comparison unit 44 samples and detects the high-frequency ripple voltage VR by taking 5 cycles of the AC power input voltage VAC as one unit during the cooking operation. Although the life of the smoothing capacitor 2 is determined by calculating the deviation (ripple), the following may be used instead.

  The high frequency ripple voltage VR is sampled and detected based on 5 cycles of the AC input voltage VAC as a unit, and the standard deviation (ripple) is calculated based on this sampling multiple times (for example, 5 times), and the plurality of standard deviations are calculated. May be calculated, and the calculated average value may be compared with the high frequency ripple threshold value to determine the life of the smoothing capacitor.

  The high frequency ripple voltage VR is sampled and detected based on 5 cycles of the AC input voltage VAC as a unit, and the standard deviation (ripple) is calculated based on this sampling multiple times (for example, 5 times), and the standard deviation is calculated. The standard deviation calculated each time is compared with the high-frequency ripple threshold value to determine the life of the smoothing capacitor. The counter is counted up each time it is determined to be the life, and the life is notified when the count value reaches the set value. You may make it make it.

  The high frequency ripple voltage VR is sampled and detected based on 5 cycles of the AC input voltage VAC as a unit, and the standard deviation (ripple) is calculated based on this sampling multiple times (for example, 5 times), and the plurality of standard deviations are calculated. The average value of the smoothing capacitor is calculated several times (for example, five times), and the average value calculated each time the average value is calculated is compared with the high frequency ripple threshold to determine the life of the smoothing capacitor. The counter may be incremented every time, and when the count value reaches the set value, the end of life may be notified.

In addition, the present invention is not limited to the embodiment described above and shown in the drawings, and the following modifications and expansions are possible.
In the above-described embodiment, the inverter 14 that outputs a high-frequency voltage having a frequency twice as high as the switching frequency when an aluminum pan serving as a low resistance load is used, but a normal inverter may be used instead.

In the above-described embodiment, the high resistance load and the low resistance load ile 22 are provided. However, a dedicated heating coil may be provided.
Although the chopper control unit 37 is configured by an IC chip different from the control circuit 27 formed of a microcomputer, the chopper control unit 37 may be configured as a partial function of the control circuit 27.

Electrical configuration diagram showing a first embodiment of the present invention Waveform diagram of each part for action explanation 2 equivalent diagram 2 equivalent diagram FIG. 1 equivalent view showing a second embodiment of the present invention. 2 equivalent diagram

Explanation of symbols

  In the drawing, 3 is a DC power supply circuit, 2 is a smoothing capacitor, 11 is a step-up chopper, 14 is an inverter, 22 is a heating coil, 27 is a control circuit (control means), 37 is a chopper control unit (control means), and 41 is a ripple. Voltage comparison unit (ripple voltage comparison unit), 42 is an operation display unit (notification unit), 43 is a DC voltage detection circuit (DC voltage detection unit), 44 is a high frequency ripple voltage comparison unit (high frequency ripple voltage comparison unit), and 45 is A high frequency ripple detection circuit (high frequency ripple detection means) is shown.

Claims (5)

A heating coil for induction heating;
A DC power supply circuit that converts an AC power supply voltage into a DC voltage;
A step-up chopper that boosts the direct-current voltage from the direct-current power supply circuit and smoothes it with a smoothing capacitor to obtain a boosted direct-current voltage;
An inverter that converts the boosted DC voltage from the boost chopper into a high-frequency voltage and supplies it to the heating coil;
Control means for controlling the step-up chopper and the inverter;
DC voltage detecting means for detecting the boosted DC voltage;
A unit of ripple of the boosted DC voltage detected by the DC voltage detecting means is detected, and the life of the smoothing capacitor is judged by comparing the ripple with a set ripple threshold value, and a notification means of the life is made. Ripple voltage comparison means for informing ,
The induction heating cooker, wherein the control means operates the ripple voltage comparison means in a state where the operation of the boost chopper is stopped before the cooking operation is started .   The induction heating cooker according to claim 1, wherein the ripple threshold value is set according to the magnitude of the step-up DC voltage. High-frequency ripple detecting means for detecting high-frequency ripple of the boost DC voltage;
A high-frequency ripple voltage comparing means for judging the life of the smoothing capacitor by comparing the high-frequency ripple detected by the high-frequency ripple detecting means with a set high-frequency ripple threshold, and notifying the informing means of the life. The induction heating cooker according to claim 1 or 2 , characterized in that. The ripple voltage comparison means or the high-frequency ripple voltage comparison means calculates the average value of the ripple by performing detection of one unit a plurality of times, and compares the calculated value with the ripple threshold value or the high-frequency ripple threshold value to thereby determine the life of the smoothing capacitor. induction heating cooker according to claim 1 or 3, wherein the determining the. The ripple voltage comparison means or the high frequency ripple voltage comparison means performs the average value calculation a plurality of times, and determines the life of the smoothing capacitor by comparing the calculated value with the ripple threshold value or the high frequency ripple threshold value every time the average value is calculated. 5. The induction heating cooker according to claim 4 , wherein the counter is incremented every time the determination is made and the notification means is caused to perform a notification operation when the count value reaches a set value .

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