JP2010055873A - Induction-heating cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction-heating cooker wherein simpler and smaller circuits can be constructed in the whole by using a DC power supply circuit in common for a plurality of heating coils. <P>SOLUTION: The induction-heating cooker comprises a rectifying circuit 2 for rectifying the voltage of a commercial power supply 1; a smoothing circuit 3 for smoothing the voltage rectified by the rectifying circuit 2; a plurality of inverter circuits 4, 5, 6 for inverting the DC voltage which has been made smooth by the smoothing circuit 3 into an AC voltage to be supplied to individual heating coils 7b, 8b, 9b, respectively; multipliers 12, 15, 18 for detecting the voltage supplied to the heating coils 7b, 8b, 9b and currents flowing in the heating coils 7b, 8b, 9b with the voltage, respectively for calculating power; and a control circuit 20 for controlling the individual inverter circuits 4, 5, 6 so that the electric power calculated by the multipliers 12, 15, 18 respectively becomes the electric power. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an induction heating cooker provided with a plurality of heating coils.

  In the conventional induction heating cooker, a rectifier circuit that is a DC power supply circuit and a smoothing capacitor are provided for a plurality of heating coils (see, for example, Patent Document 1).

JP 2001-267052 A (page 4, FIG. 2)

  In the above-described conventional induction heating cooker, since the DC power supply circuit is provided for each of the plurality of heating coils, the circuit configuration of the entire cooker is increased, and a large space for storing the circuit board is required. . However, in order to improve the design, the cooker is required to be reduced in size and thickness, and in order to achieve this, simplification of circuit components is an issue.

  The present invention has been made in order to solve the above-described problems. Inductive heating that allows a plurality of heating coils to share a DC power supply circuit, simplifies the circuit configuration of the cooker as a whole, and enables downsizing. The purpose is to provide a cooker.

  An induction heating cooker according to the present invention includes a DC power supply circuit that converts the voltage of an AC power supply into DC, and a plurality of inverters that convert the DC voltage converted by the DC power supply circuit into AC and supply each of the heating coils. A circuit, a voltage supplied to each heating coil, and a plurality of power calculation means for calculating a power by detecting a current flowing in the heating coil based on the voltage, and a power calculated by the plurality of power calculation means And a control means for controlling each inverter circuit so as to obtain set power.

  According to the present invention, since a plurality of power calculation means for calculating the power by detecting the voltage supplied to each heating coil and the current flowing through the heating coil based on the voltage are provided, a plurality of DC power supply circuits are provided. The inverter circuit can be shared, so that the circuit configuration of the entire cooking device can be simplified and reduced in size, and the cooking device itself can be reduced in size and thickness.

Embodiment 1 FIG.
FIG. 1 is a circuit diagram of an induction heating cooker showing Embodiment 1 of the present invention.
As shown in the figure, the induction heating cooker according to the first embodiment is provided with a rectifier circuit 2 and a smoothing circuit 3 as a DC power supply circuit shared by the three inverter circuits 4, 5, 6. , 6 (hereinafter referred to as “first, second and third inverter circuits 4, 5, 6”), multiplications for calculating the electric power of the heating coils 7 b, 8 b, 9 b for induction heating the cooking pan and the like, respectively. Units (power calculating means) 12, 15 and 18 are provided.

  The rectifier circuit 2 is a bridge-type full-wave rectifier circuit, and full-wave rectifies the AC voltage of the commercial power source 1. The smoothing circuit 3 includes a choke coil 3a and a smoothing capacitor 3b inserted between the outputs of the rectifier circuit 2, and smoothes the voltage that has been full-wave rectified by the rectifier circuit 2. The first inverter circuit 4 includes two switching elements 4a and 4b (hereinafter referred to as “upper switch 4a and lower switch 4b”) connected in series between both electrodes of the smoothing capacitor 3b of the smoothing circuit 3, and an upper and lower switch. Flywheel diodes 4c and 4d connected in reverse parallel to 4a and 4b, respectively, and a drive circuit 4e that outputs a drive signal (pulse signal) for alternately turning on and off the upper switch 4a and the lower switch 4b. . A load circuit 7 including a resonance capacitor 7a and a heating coil 7b is connected in parallel to the lower switch 4b of the first inverter circuit 4.

  The second and third inverter circuits 5 and 6 have the same circuit configuration as the first inverter circuit 4 described above, and the input side is connected between both electrodes of the smoothing capacitor 3b of the smoothing circuit 3. A load circuit 8 comprising a resonance capacitor 8a and a heating coil 8b is connected in parallel to the lower switch 5b of the second inverter circuit 5, and a resonance capacitor similar to the above is connected to the lower switch 6b of the third inverter circuit 6. A load circuit 9 including 9a and a heating coil 9b is connected in parallel. Each heating coil 7b, 8b, 9b is arrange | positioned adjacent to the back surface of the top plate (not shown) of a cooking appliance main body. In addition, the heating plate which shows the mounting position of a cooking pan in the part facing each heating coil 7b, 8b, 9b is provided in the top plate.

  Each heating coil 7b, 8b, 9b is connected in parallel with voltage detectors 10, 13, 16 made of, for example, voltage dividing resistors, and one output line of each inverter circuit 4, 5, 6 is connected to the current transformer 11 , 14, 17 are provided. The multiplier 12 receives the voltage across the heating coil 7b (high frequency voltage) detected by the voltage detector 10, and receives the coil current (high frequency current) of the heating coil 7b detected by the current transformer 11. The power is calculated and output to the control circuit 20 described later. The multiplier 15 inputs the voltage across the heating coil 8b detected by the voltage detector 13, inputs the coil current of the heating coil 8b detected by the current transformer 14, calculates the power, and the same as above. To the control circuit 20. Furthermore, the multiplier 18 inputs the voltage across the heating coil 9b detected by the voltage detector 16, inputs the coil current of the heating coil 9b detected by the current transformer 17, calculates the power, and the control circuit 20 Output to.

  When power is set for the heating unit, the control circuit 20 controls the drive circuit 4e of the first inverter circuit 4 so that the set power is output from, for example, the heating coil 7b disposed in the heating unit. . By this control, when the power calculated by the multiplier 12 is not the set power, the drive circuit 4e of the first inverter circuit 4 is controlled so that the power becomes the set power. That is, frequency control is performed so that, for example, the duty of the pulse signal of the drive circuit 4e is approximately 50% so that the power calculated by the multiplier 12 is substantially the same as the set power.

Next, operation | movement of an induction heating cooking appliance is demonstrated based on the waveform diagram shown in FIG. FIG. 2 is a waveform diagram showing the operation of each inverter circuit in the first embodiment.
For example, when electric power is set for each heating unit, the control circuit 20 causes each inverter circuit 4, so that the set power is output from the heating coils 7b, 8b, and 9b arranged in each heating unit. The drive circuits 4e, 5e and 6e of 5 and 6 are controlled. In this case, the frequency control of the pulse signal is performed so that the duty is approximately 50% for the drive circuits 4e, 5e, and 6e so that the electric power set in each heating unit can be obtained.

  For example, when the same power is set to be output from the heating coils 7b and 9b, the drive circuits 4e and 6e generate pulse signals based on the frequency control of the control circuit 20, and the upper and lower switches 4a. 4b, 6a, and 6b are turned on / off alternately (see FIGS. 2A and 2C). In this case, since the set power is the same, the pulse signals are out of phase at the same frequency (duty approximately 50%). When the power of the heating coil 8b is set lower than that of the heating coils 7b and 9b, the pulse signal output from the drive circuit 5e is a pulse signal having a higher frequency (duty approximately 50%) than the above frequency, The upper and lower switches 5a and 5b are alternately turned on / off (see FIG. 5B).

  On the other hand, the control circuit 20 reads the electric powers of the heating coils 7b, 8b, and 9b calculated by the multipliers 12, 15, and 18, respectively, and compares them with the electric powers set for each. For example, when the power of the heating coil 7b calculated by the multiplier 12 is different from the set power, frequency control based on the difference is performed on the drive circuit 4e. When the power of the heating coil 7b is higher than the set power, the frequency is increased so that the power is reduced to the set power, and when the power of the heating coil 7b is lower than the set power, the power is increased to the set power. Reduce the frequency.

  As described above, according to the first embodiment, the voltage detectors 10, 13, and 16 that detect the voltages applied to the heating coils 7b, 8b, and 9b and the coil currents that flow through the heating coils 7b, 8b, and 9b, respectively. Since the current transformers 11, 14, and 17 to be detected are provided, and the multipliers 12, 15, and 18 are provided to calculate the power from the detected voltage and the coil current, respectively, the first, second, and third inverters The rectifier circuit 2 and the smoothing circuit 3 that are the DC power supply circuits of the circuits 4, 5, and 6 can be made into one, so that the circuit configuration of the entire cooking device can be simplified and reduced in size, The cooker itself can be made small and thin.

  In the first embodiment, the inverter circuits 4, 5, and 6 are individually provided for the load circuits 7, 8, and 9. However, as shown in FIG. For example, a power module with a built-in IGBT (a module in which the power input is a common terminal) may be used. By using this power module, the circuit configuration can be further reduced.

  In addition, an amorphous coil is used as the choke coil 3a constituting the smoothing circuit 3 so as to suppress vibration noise generated when the first, second and third inverter circuits 4, 5, 6 are driven by pulse signals having different frequencies. It may be.

Embodiment 2. FIG.
FIG. 4 is a circuit diagram of an induction heating cooker showing Embodiment 2 of the present invention. In addition, the same code | symbol is attached | subjected to the part similar to Embodiment 1 demonstrated in FIG.
As shown in the drawing, the induction heating cooker of the second embodiment is provided with a rectifier circuit 2 and a smoothing circuit 3 as a DC power supply circuit shared by the first and second inverter circuits 4 and 5, and the embodiment 1 is provided with multipliers 12 and 15 for calculating the electric power of the heating coils 7b and 8b for induction heating of the cooking pot based on the outputs of the first and second inverter circuits 4 and 5, respectively. The second inverter circuits 4 and 5 are driven by duty control of a pulse signal having a constant frequency. In order to prevent commutation due to a constant frequency, a clamp diode 7 c is connected in parallel to the resonant capacitor 7 a of the load circuit 7, and a clamp diode 8 c is connected in parallel to the resonant capacitor 8 a of the load circuit 8. .

Next, the operation of the induction heating cooker will be described based on the waveform diagram shown in FIG. FIG. 5 is a waveform diagram showing the operation of each inverter circuit and smoothing circuit in the second embodiment.
For example, when electric power is set for each heating unit, the control circuit 20 drives the inverter circuits 4 and 5 so that the electric power set for each heating unit is output from the heating coils 7b and 8b. 4e and 5e are controlled respectively. That is, the duty control of the pulse signal having a constant frequency is performed on the drive circuits 4e and 5e so that the electric power set in each heating unit can be obtained. In this case, as an example, the ON time with respect to the period of the pulse signal is long on the first inverter circuit 4 side (see FIGS. 5A and 5C), so the power set for the heating unit is high on the heating coil 7b side. ing.

  The drive circuit 4e generates a pulse signal based on the duty control of the control circuit 20, turns on / off the upper switch 4a and the lower switch 4b of the first inverter circuit 4 alternately (see FIG. 4A), 1 inverter circuit 4 outputs the current shown in FIG. Similarly to the above, the drive circuit 5e generates a pulse signal based on the duty control of the control circuit 20, and alternately turns on / off the upper switch 5a and the lower switch 5b of the second inverter circuit 5 (FIG. 4 ( c)), the second inverter circuit 5 outputs the current shown in FIG. The smoothing circuit 3 constituting the DC power supply circuit outputs a sinusoidal current based on the sum of the output currents of the first and second inverter circuits 4 and 5 (see (e) in the figure). This is because the first and second inverter circuits 4 and 5 are driven at the same frequency, that is, the upper switches 4a and 5a and the lower switches 4b and 5b are alternately turned on and off at the same frequency. This is because the current does not overlap as the current flowing through the choke coil 3a of the smoothing circuit 3.

  On the other hand, the control circuit 20 reads the power of the heating coils 7b and 8b calculated by the multipliers 12 and 15 and compares it with the power set for each. For example, when the power of the heating coil 7b calculated by the multiplier 12 is different from the set power, duty control based on the difference is performed on the drive circuit 4e. When the power of the heating coil 7b is higher than the set power, the on-time of the pulse signal of the upper switch 4a is shortened so that the power drops to the set power, and when the power of the heating coil 7b is lower than the set power, The ON time of the pulse signal of the upper switch 4a is lengthened so that the power rises to the set power.

  As described above, according to the second embodiment, since the first and second inverter circuits 4 and 5 are driven at the same frequency, currents with different driving frequencies are superimposed on the choke coil 3a of the smoothing circuit 3. Will not flow. For this reason, there is no fluctuation of the current flowing through the choke coil 3a at the differential frequency due to the superposition of currents of different frequencies, the vibration sound of the choke coil 3a can be prevented, and the interference sound generated between the heating coils 7b and 8b can be suppressed. . Moreover, it becomes possible to make the rectifier circuit 2 and the smoothing circuit 3 which are direct current power supply circuits of the first and second inverter circuits 4 and 5 into one, thereby simplifying the circuit configuration of the entire cooking device and reducing the size. The cooker itself can be made small and thin.

Embodiment 3 FIG.
In the second embodiment, the first and second inverter circuits 4 and 5 are driven at the same frequency. However, in the circuit configuration of the induction heating cooker shown in FIG. (2) The inverter circuits 4 and 5 are driven with pulse signals having substantially the same phase and the same frequency.
For example, as shown in FIG. 6, when the upper switches 4a and 4b of the first inverter circuit 4 are alternately turned on / off with a pulse signal having a constant frequency (see FIG. 6A), the second inverter circuit 5 The upper switches 5a and 5b are alternately turned on / off with pulse signals having substantially the same phase and the same frequency (see FIG. 5C).

  In this case, the current shown in FIG. 4B is output from the first inverter circuit 4, and the current shown in FIG. 5D is output from the second inverter circuit 5. The smoothing circuit 3 constituting the DC power supply circuit outputs a sinusoidal current due to the difference between the output currents of the first and second inverter circuits 4 and 5 (see (e) in the figure). This is because the amplitude (peak current) of the current flowing through the smoothing circuit 3 can be suppressed by driving the first and second inverter circuits 4 and 5 with the same frequency and the pulse signal having substantially the opposite phase.

  By suppressing the amplitude of the current, loss and vibration generated in the choke coil 3a are reduced. In addition, as in the second embodiment, the rectifier circuit 2 and the smoothing circuit 3 that are the DC power supply circuits of the first and second inverter circuits 4 and 5 can be made into one, thereby the entire cooker. This circuit configuration can be simplified and miniaturized, and the cooker itself can be made small and thin.

Embodiment 4 FIG.
In the first to third embodiments, the rectifier circuit 2 and the smoothing circuit 3 are shared as the DC power supply circuits of the plurality of inverter circuits 4, 5, and 6, but the fourth embodiment is as shown in FIG. Further, the rectifier circuit 2 is provided as one, and the smoothing circuit 3 is provided between the rectifier circuit 2 and the first inverter circuit 4 and between the rectifier circuit 2 and the second inverter circuit 5.

  In the induction heating cooker according to the fourth embodiment, when the first and second inverter circuits 4 and 5 are driven by pulse signals having different frequencies, currents having different frequencies (high-frequency currents) are choke coils 3a of the smoothing circuit 3. It does not overlap with the current flowing through. For this reason, the vibration sound of the choke coil 3a due to the superposition of the current can be prevented. Moreover, since the rectifier circuit 2 is shared by the first and second inverter circuits 4 and 5, the entire circuit of the cooker can be reduced in size and the cost can be reduced.

  In the second to fourth embodiments, the inverter circuits 4 and 5 are individually provided for the load circuits 7 and 8. However, two sets of the upper and lower switches 4a, 4b, 5a, and 5b, for example, are provided. A power module with a built-in IGBT may be used. By using this power module, the circuit configuration can be further reduced.

It is a circuit diagram of the induction heating cooking appliance which shows Embodiment 1 of this invention. FIG. 3 is a waveform diagram showing an operation of each inverter circuit in the first embodiment. It is a circuit diagram which shows the structure of the power module in which several IGBT was incorporated. It is a circuit diagram of the induction heating cooking appliance which shows Embodiment 2 of this invention. FIG. 10 is a waveform diagram showing the operation of each inverter circuit and smoothing circuit in the second embodiment. FIG. 10 is a waveform diagram showing the operation of each inverter circuit and smoothing circuit in the third embodiment. It is a circuit diagram of the induction heating cooking appliance which shows Embodiment 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Commercial power supply, 2 Rectifier circuit, 3 Smoothing circuit, 3a Choke coil, 3b Smoothing capacitor, 4 1st inverter circuit, 4e drive circuit, 5 2nd inverter circuit, 5e drive circuit, 6 3rd inverter circuit, 6e drive circuit, 7 load circuit, 7a resonance capacitor, 7b heating coil, 8 load circuit, 8a resonance capacitor, 8b heating coil,
9 Load circuit, 9a Resonance capacitor, 9b Heating coil, 10, 13, 16 Voltage detector, 11, 14, 17 Current transformer, 12, 15, 18 Multiplier, 20 Control circuit.

Claims (6)

A DC power supply circuit for converting the voltage of the AC power supply to DC,
A plurality of inverter circuits that convert the DC voltage converted by the DC power supply circuit into alternating current and supply each of the individual heating coils;
A plurality of power calculation means for calculating power by detecting a voltage supplied to each heating coil and a current flowing through the heating coil based on the voltage;
An induction heating cooker comprising: control means for controlling individual inverter circuits so that the power calculated by the plurality of power calculation means is set to the power set for each of them.   2. The control unit according to claim 1, wherein each of the inverter circuits is controlled by a drive signal having the same frequency so that the power calculated by the plurality of power calculation units becomes a set power. The induction heating cooker described.   The control means controls each inverter circuit by a drive signal having substantially the same phase and substantially opposite phase so that the power calculated by the plurality of power calculation means becomes the power set for each. The induction heating cooker according to claim 1. A rectifier circuit for rectifying the voltage of the AC power supply;
A plurality of smoothing circuits for smoothing the voltage rectified by the rectifying circuit;
A plurality of inverter circuits that convert the direct current voltage smoothed by each smoothing circuit into alternating current and supply each of the heating coils;
A plurality of power calculation means for calculating power by detecting a voltage supplied to each heating coil and a current flowing through the heating coil based on the voltage;
An induction heating cooker comprising: control means for controlling individual inverter circuits so that the power calculated by the plurality of power calculation means is set to the power set for each of them.   5. The control means controls each inverter circuit with drive signals of different frequencies so that the power calculated by the plurality of power calculation means becomes a set power. The induction heating cooker described.   The induction heating cooker according to any one of claims 1 to 5, wherein a power module configured by incorporating switching elements of the plurality of inverter circuits is used.

Images