TW201838477A - Electromagnetic induction heating cooker - Google Patents

Abstract

The electromagnetic induction heating cooker is provided with: a pot placing part; an electromagnetic induction heating coil which generates a magnetic field in the pot placing part; an inverter circuit which is provided with a switching element and provides power to the electromagnetic induction heating coil; a timing output circuit which generates, from an input voltage and a voltage from the switching element, an output control timing waveform of the inverter circuit; an input voltage fluctuation detection circuit which detects a fluctuation in input voltage and generates an input voltage fluctuation waveform; a load detection circuit which performs, on the basis of the input voltage fluctuation waveform and the output control timing waveform, a load detection; and a main control circuit which determines, on the basis of the load detection, whether a pot is placed on the pot placing part. The load detection circuit is configured to perform the load detection on the basis of the input voltage fluctuation waveform while the output control timing waveform is at a high level.

Description

   Electromagnetic induction heating conditioner   

The invention relates to an electromagnetic induction heating conditioner.

Conventionally, there is an induction heating conditioner. The induction heating conditioner is formed in a magnetic field generated by an electromagnetic induction heating coil to form a pot placing portion for a pot for holding a conditioner. Heat conditioning. This induction heating conditioner generates electricity by energizing an electromagnetic induction heating coil to generate a magnetic field, so that the pot generates an induced electromotive force, heats the pot itself, and performs heating conditioning.

That is, this electromagnetic induction heating conditioner exists in the pot which becomes a resistance load in the magnetic field generated by the electromagnetic induction heating coil, thereby generating a load current, and the pot generates heat to perform heating conditioning.

When the heating conditioner of the electromagnetic induction heating method does not have a resistance load in the magnetic field generated by the electromagnetic induction heating coil, that is, when the pot serving as the resistance load is not arranged on the pot placement portion, it becomes non-existent. Load state without load current.

Using this phenomenon, it has conventionally been controlled in the following manner. When the electromagnetic induction heating coil is energized, it is detected whether a load current is generated. When the load current cannot be detected, it is determined that the pot is not placed in the pot placing portion, and The heating operation stops.

In addition, as a method for detecting the presence or absence of this load current, there is a method using a low-frequency AC detection means having a current transformer (for example, Patent Document 1).

    [Leading Patent Literature]         [Patent Literature]    

[Patent Document 1] Japanese Patent No. 3314124

However, this method of detecting the presence or absence of a load requires a current transformer, and the circuit configuration becomes complicated. Moreover, since a current transformer is used, there is a problem that the components constituting the circuit become expensive.

The present invention has been developed by a developer for solving the above-mentioned problems, and a main object thereof is to provide an electromagnetic induction heating conditioner that can detect the presence or absence of a load without using a current transformer.

In order to solve the above-mentioned problems, the electromagnetic induction heating conditioner includes a pot placing portion; the electromagnetic induction heating coil generates a magnetic field in the pot placing portion; the frequency conversion circuit includes a switching element and supplies power to the electromagnetic induction heating coil; The timing output circuit is to generate the output control timing waveform of the frequency conversion circuit from the input voltage and the voltage of the switching element; the input voltage change detection circuit is to detect the change of the input voltage and generate the input voltage change waveform; the load detection circuit is to be based on the input The voltage fluctuation waveform and the output control timing waveform are used for load detection; and the main control circuit is based on the load detection to determine whether the pot is installed in the pot placement section; the load detection circuit is configured to output the control timing waveform based on the input voltage fluctuation waveform as The input voltage fluctuation waveform between high levels is used for load detection.

According to the present invention, an electromagnetic induction heating conditioner can be provided. The electromagnetic induction heating conditioner performs the load detection by using an input voltage variation waveform between an output control timing waveform and a High level according to an input voltage variation waveform. The presence or absence of a load can be detected with high accuracy without using a current transformer.

1‧‧‧Commercial low frequency AC power supply

2‧‧‧full wave rectifier circuit

3‧‧‧ smoothing capacitor

4‧‧‧ electromagnetic induction heating coil

5‧‧‧Resonant capacitor

6‧‧‧ switching element

7‧‧‧diode

8‧‧‧ resistance

9‧‧‧Input voltage fluctuation detection circuit

10‧‧‧ Switching control circuit

11‧‧‧Main control circuit

12‧‧‧sequence output circuit

13‧‧‧Voltage detection circuit

14‧‧‧Input voltage detection circuit

15‧‧‧Load detection circuit

N‧‧‧ Pot

P‧‧‧Pot placing section

S‧‧‧circuit

50‧‧‧ electromagnetic induction heating conditioner

51a‧‧‧Power Plug

Fig. 1 is a block diagram showing a configuration of a circuit S of the electromagnetic induction heating conditioner of the first embodiment.

Fig. 2 is a graph showing an operation waveform when a pot is in the heating operation of the electromagnetic induction heating conditioner of the first embodiment.

Fig. 3 is a graph showing an operation waveform when there is no pan during the heating operation of the electromagnetic induction heating conditioner of the first embodiment.

Fig. 4 is a perspective view of an electromagnetic induction heating conditioner according to a second embodiment.

Fig. 5 is a sectional view taken along the line A-A in Fig. 4;

    First Embodiment    

The first embodiment will be described with reference to FIGS. 1 to 3.

FIG. 1 is a block diagram showing a configuration of a circuit S of an electromagnetic induction heating conditioner.

Commercial low-frequency AC power supply 1 is connected to full-wave rectifier circuit 2. The output of this full-wave rectifier circuit 2 is smoothed by a smoothing capacitor 3 and a choke coil (not shown).

The smoothed output is connected to a parallel circuit composed of a resonance capacitor 5, a switching element 6, and a diode 7 connected in series with the electromagnetic induction heating coil 4 via an electromagnetic induction heating coil 4 for high-frequency induction heating. These elements constitute a frequency conversion circuit that converts DC to AC, and supplies power to the electromagnetic induction heating coil 4. In addition, in a magnetic field generated by the electromagnetic induction heating coil 4 that receives power from the frequency conversion circuit, a pot placing portion P in which a pot N holding a conditioner is disposed is provided.

Next, the switching element 6 is controlled by a switching control circuit 10. The switching control circuit 10 is connected to the main control circuit 11 and controlled by a switching control signal from the main control circuit 11. The main control circuit 11 is a main control circuit having a microprocessor and a memory, and controlling the heating operation of the electromagnetic induction heating conditioner or various notifications, and the control of each of the above sections.

Next, the smoothing capacitor 3 is connected to the timing output circuit 12 and the input voltage detection circuit 14 via a resistor 8. The input voltage detected by the input voltage detection circuit 14 is input to the main control circuit 11 and a commercial low-frequency AC power supply voltage is detected. The timing output circuit 12 is also connected to the collector terminal of the switching element 6. Based on the commercial low-frequency AC power supply voltage, the timing of the change in the collector-emitter voltage Vce of the switching element 6 from 0V or 0V is detected. After the timing, an output control timing waveform is generated and input to the main control circuit 11. The voltage detection circuit 13 is connected to the collector terminal of the switching element 6, and detects the collector-emitter voltage Vce of the switching element 6 and inputs the voltage Vce to the main control circuit 11.

The smoothing capacitor 3 is connected to an input voltage fluctuation detection circuit 9 that detects a change in the input voltage and generates an input voltage fluctuation waveform. The input voltage fluctuation waveform from the input voltage fluctuation detection circuit 9 and the output control timing waveform from the timing output circuit 12 are input to the load detection circuit 15. The load detection circuit 15 detects the presence or absence of a load current based on the input voltage fluctuation waveform from the input voltage fluctuation detection circuit 9 and the output control timing waveform from the timing output circuit 12. In addition, the main control circuit 11 judges the presence or absence of a pot in the pot placement portion P based on the detection-side signal of the presence or absence of a load current from the load detection circuit 15.

Although the main control circuit 11 is not shown in the figure, the operation input of the electromagnetic induction heating conditioner is used to adjust the pulse width of the switching control signal to select the strength of the heating. Alternatively, the control program can be used to control the heating strength or make the strength variable. In addition, the main control circuit 11 controls the intensity of the heating or stops after determining whether there is a pan or not based on the detection-side signal from the load detection circuit 15.

Figure 2 shows the operation waveforms when a pot is in the heating operation of the electromagnetic induction heating conditioner, which represent (a) the collector-emitter voltage Vce of the switching element 6, (b) the output control timing waveform, and (c) Switching element current, (d) input voltage fluctuation waveform, and (e) switching element drive signal. In addition, the state with the pan is the state in which the pan N is placed on the pan placing portion P.

The switching control circuit 10 outputs a switching element driving signal after receiving a switching control signal from the main control circuit 11. When the switching element driving signal is ON (High level), the switching element 6 is turned on, and the switching element current Ic flows. Before the switching element 6 is turned on, the collector-emitter voltage Vce of the switching element 6 becomes 0V.

By receiving the switching control circuit 10 of the switching control signal from the main control circuit 11, when the switching element driving signal is turned OFF (Low level), the switching element current Ic becomes non-flowing. On the other hand, the collector of the switching element 6- The inter-emitter voltage Vce starts to rise. The magnitude of the collector-emitter voltage Vce of the switching element 6 generated at this time varies in proportion to the switching element current Ic flowing when the switching element 6 is ON.

The timing for turning the switching element 6 OFF is controlled by the main control circuit 11 according to the strength of the heating. The period of the collector-emitter voltage Vce of the switching element 6 is determined based on the reactance components of the electromagnetic induction heating coil 4 and the pot for induction heating, and the resonance frequency of the resonance capacitor 5.

At a period determined according to the resonance frequency, the collector-emitter voltage Vce of the switching element 6 becomes 0V. The timing at which the collector-emitter voltage Vce of this switching element 6 changes from 0V and the timing at which it becomes 0V is detected. The timing output circuit 12 generates output control synchronized with the waveform of the collector-emitter voltage of the switching element 6. The timing waveform is input to the main control circuit 11.

The main control circuit 11 that detects the falling edge of the output control timing waveform, that is, the collector-emitter voltage Vce of the switching element 6 becomes 0V, outputs a switching control signal after a fixed period, and the switching control circuit 10 causes the switching element The drive signal turns ON.

The switching element current Ic is when the collector-emitter voltage Vce of the switching element 6 becomes 0V, and the regenerative current Ir by the frequency conversion circuit flows in the reverse direction. After the collector-emitter voltage Vce of the switching element 6 becomes 0V, the switching control signal is output to the main control circuit 11, and the fixed period during which the switching control circuit 10 turns the driving signal of the switching element ON is a period during which the regenerative current Ir is stable. Better.

The input voltage fluctuation waveform fluctuates in proportion to the magnitude of the switching element current Ic. When the switching element 6 is turned ON, the switching element current Ic flows. This switching element current Ic is supplied from the current stored in the commercial low-frequency AC power supply 1 and the smoothing capacitor 3. At this time, the amount of current supplied from the smoothing capacitor 3 is supplied to the smoothing capacitor 3 from the commercial low-frequency AC power supply 1 during the period B in which the switching element 6 is turned OFF.

The period (B) during which the switching element 6 turns OFF includes not only the period (C) during which the collector-emitter voltage Vce of the switching element 6 occurs, but also the period (D) until the switching element driving signal turns ON. This is fixed. The period (D) is a regenerative current Ir. Since the regenerative current Ir from the resonance capacitor 5 flows into the smoothing capacitor 3, the input voltage fluctuation waveform becomes large. After that, the current is gradually stored in the smoothing capacitor 3, and the input voltage fluctuation waveform becomes constant as the input voltage is smoothed.

The load detection circuit 15 uses an output control timing waveform. When the output control timing waveform is at a Low level (the period during which it becomes OFF), the load detection circuit 15 is configured to reduce the input voltage fluctuation waveform to Low and allow the regenerative current Ir to flow. The input voltage fluctuation amount is not detected between the period (H) and the period (I) when the switching element 6 is turned on, and the main control circuit 11 is input with the input voltage fluctuation amount between the periods (C). That is, the load detection is performed based on the area K of the input voltage fluctuation waveform whose output control timing waveform is between the High level (the period during which it turns ON).

Next, a state in which the pot N is not placed on the pot placing portion P will be described. FIG. 3 shows the operation waveforms when there is no pot during the heating operation of the electromagnetic induction heating conditioner of the present invention, which respectively represent (a) the collector-emitter voltage Vce of the switching element 6, and (b) the output control timing waveforms, (c) Switching element current, (d) Input voltage fluctuation waveform, and (e) Switching element drive signal. In addition, the pan-less pan N is not placed in the pan placement portion P.

The magnitude of the input voltage fluctuation waveform is changed in proportion to the switching element current Ic when the switching element 6 is turned on. Therefore, in the state without the pot N, the input voltage fluctuation waveform becomes smaller than in the state with the pot N. The load detection circuit 15 uses an output control timing waveform. When the output control timing waveform is at a Low level (the period during which it becomes OFF), the load detection circuit 15 is configured to reduce the input voltage fluctuation waveform to Low and allow the regenerative current Ir to flow. The input voltage fluctuation amount is not detected between the period (L) and the period (M) during which the switching element 6 is turned on, and the input voltage fluctuation amount is input to the control circuit. That is, the load detection is performed based on the area Q of the input voltage fluctuation waveform between the output control timing waveform and the High level (the period during which it turns ON).

As shown above, when the load detection of the presence or absence of the pot N is performed, the output control timing waveform is Low, and the input voltage fluctuation waveform is reduced to Low, and the regenerative current Ir flows. The amount of input voltage fluctuation is not detected between the period and the period when the switching element 6 is turned on, and is a period during which the regenerative current Ir does not flow, because the area Q (integrated value) of the input voltage variation waveform between the time when the switching element 6 turns off, Since the load detection is performed, the influence of the fluctuation of the input voltage caused by the regenerative current Ir can be reduced.

That is, the period in which the regenerative current Ir does not flow and the period in which the switching element 6 is OFF are between the presence and absence of the pot N, and a large difference occurs in the input voltage fluctuation waveform, so that the presence or absence of load detection can be determined more accurately. , Which can improve the accuracy of load detection. In addition, in the actual load detection judgment, when the above-mentioned area Q and area K are larger than a certain threshold X, it is judged that there is a load (with a pot N), and when the threshold X is not reached, it is judged that there is no Load (without pan N). The threshold X is set to a value between the value of the area Q and the value of the area K.

    Second embodiment    

The second embodiment will be described with reference to FIGS. 4 and 5. Fig. 4 is a perspective view of the electromagnetic induction heating conditioner 50 including the circuit S of the first embodiment. Fig. 5 is a sectional view taken along the line A-A in Fig. 4; The same components as those in the first embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

The electromagnetic induction heating conditioner 50 includes a main body 51, a lid body 52, and a pan N. The pan placement part P is formed in the main body 51. The pot placing portion P is a recessed portion that opens toward the upper portion of the main body 51, and is configured to hold the conditioner inside the pot N and can be accommodated.

The cover body 52 is attached to the main body 51 as a rear end portion of the shaft in order to open and close the opening of the pot placement portion P of the main body 51. In a state where the lid body 52 is opened to the main body 51, the pot N can be detached from the pot placing portion P. In addition, the pot N is installed in the pot placing portion P, and the cover N is covered with the body 51 and the cover 52 in a state where the cover 52 is closed to the body 51 and is held inside the electromagnetic induction heating conditioner 50.

Therefore, the pan N is in a state in which it cannot be seen from the outside of the electromagnetic induction heating conditioner 50 and is held inside the electromagnetic induction heating conditioner 50. That is, in the case where the electromagnetic induction heating conditioner 50 is in a state where the cover body 52 is closed to the main body 51, it is impossible to recognize from the outside whether or not the pot N is installed inside the main body 51.

Next, the electromagnetic induction heating coil 4 constituting the circuit S is disposed below the pot placement portion P and inside the body 51. The circuit S has a power plug 51a. This power plug 51a is led out to the outside of the main body 51, and is connected to a commercial low-frequency AC power supply 1, whereby the electromagnetic induction heating conditioner 50 receives power.

The bottom surface of the pot N installed in the pot placing portion P is located in a magnetic field generated by the electromagnetic induction heating coil 4. That is, the pan N is induction-heated by the change of the magnetic field generated by the heating coil 4 by electromagnetic induction, and can heat-condition the conditioning substance held inside. The circuit S is provided inside the body 51.

By configuring each unit as described above, the presence or absence of load detection can be determined more accurately, and the accuracy of load detection can be improved, so it can be accurately determined whether or not the pot N is held inside the electromagnetic induction heating conditioner 50. Therefore, even if the user forgets to put the pot N in the electromagnetic induction heating conditioner 50 and start the heating operation, the load detection can be performed with accuracy, and a state without the pot N can be detected, and the wasteful heating conditioning operation can be stopped. The electromagnetic induction heating conditioner 50 of the present embodiment is, for example, an electric cooker for cooking rice, or an electrical conditioner for conditioning such as cooking.

Claims (5)

    An electromagnetic induction heating conditioner includes: a pot placing portion; an electromagnetic induction heating coil generating a magnetic field at the pot placing portion; a frequency conversion circuit including a switching element and supplying power to the electromagnetic induction heating coil; a timing output circuit The output control timing waveform of the frequency conversion circuit is generated from the input voltage and the voltage of the switching element; the input voltage variation detection circuit detects the variation of the input voltage and generates an input voltage variation waveform; the load detection circuit is based on the The input voltage fluctuation waveform and the output control timing waveform are used for load detection; and the main control circuit is based on the load detection to determine whether a pot is set in the pot placement section; the load detection circuit is based on the input voltage fluctuation waveform. The output control timing waveform is an input voltage fluctuation waveform between High levels, and the load detection is performed.         For example, the electromagnetic induction heating conditioner of the first scope of the patent application, wherein the output control timing waveform is during the period when the switching element is OFF, and the period during which the regenerative current does not flow to the switching element becomes the High level.         For example, the electromagnetic induction heating conditioner of item 1 or 2 of the patent application scope, wherein the main control circuit is a case where the integral value of the input voltage fluctuation waveform is between a threshold value and a threshold value when the output control timing waveform is High , It is judged that the pot is placed in the pot placing portion.         For example, the electromagnetic induction heating conditioner of item 1 or 2 of the patent application scope further includes: a switching control circuit that supplies a driving signal to the frequency conversion circuit; and a voltage detection circuit that detects the voltage of the switching element; the main The control circuit supplies a switching control signal that controls the switching control circuit.         For example, the electromagnetic induction heating conditioner of item 1 or 2 of the patent application scope has a body and a cover body; the pot placing portion is formed on the body; the cover system is installed on the body in order to open and close the pot placing portion.