JPS63299078A - High-frequency heating device - Google Patents

Abstract

PURPOSE:To improve the cooking performance by providing the first and second resonance circuits and connecting them to a switch element with a connecting means. CONSTITUTION:This device is constituted of a power supply unit 5 obtained from a commercial power supply or the like, the first resonance circuit consisting of the first resonance capacitor 7a and a booster transformer 13, the second resonance circuit consisting of the second resonance capacitor 7b and a heating coil 12, one or more switch elements 8, and a connecting means 24 connecting either one or both of the first and second resonance circuits to the switch elements 8. The inverter operating condition when a heating coil 12 is operated and the inverter operating condition when the high-voltage transformer 13 is operated can be independently optimized respectively, and dielectric heating and induction heating can be concurrently performed. The cooking performance can be thereby improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high-frequency heating device such as a microwave oven or an induction heating cooker that electrically heats food, liquid, etc.
More specifically, the present invention relates to a heating device that generates high frequency power from a commercial power source, battery, etc. using a so-called inverter device using semiconductor switching elements, etc., and uses this high frequency power for the above purpose.

2. Description of the Related Art Conventionally, many high-frequency heating devices of this type have been proposed, for example, as shown in FIG.

FIG. 6 is a circuit diagram of a high-frequency heating device configured to alternately use the high-frequency power generated by an inverter and to enable switching between dielectric heating and induction heating.

In Fig. 6, a commercial power supply 1, a diode bridge 2,
The inductor 3 and capacitor 4 constitute a power supply section 5 of the inverter, forming a DC power supply or a pulsating current power supply. Innovataro consists of a resonant capacitor 7, a transistor 8 which is a switching element, and a diode 9. The transistor 8 is driven by a control circuit 1o and has a frequency of 2°KHz to 1
Performs high frequency switching operation at 0.00 KHz. The output of the inverter 6 is configured to be supplied to a heating coil 12 or a step-up transformer 13 by an output changeover switch 11. The output energy of the heating coil 12 is supplied to an induction heated object 14 such as a pan, and so-called induction heating is performed. On the other hand, the output of the step-up transformer 13 is rectified by a capacitor 16 and a diode 16, and the output of the magnetron 1
7, and induction heating is performed by the oscillation of the magnetron 17.

When the changeover switch 11 is in the illustrated state, the resonance capacitor 7
and step-up transformer 13 form a resonant circuit, and current 1a/d and voltage vc) flowing through transistor 8 and diode 9 have waveforms as shown in FIGS. 6(a) and Φ), respectively. On the other hand, when the changeover switch 11 is in the opposite state to that illustrated, the heating coil 12 and the resonant capacitor 7 form a resonant circuit. Therefore, at this time as well, Figure 6 (
The voltage and current waveforms shown in a) and (b) are shown in FIG. 9. The transistor 8 operates as a switching element of a so-called resonant inverter. Therefore, the resonance capacitor 7 is designed so as to satisfy the resonance condition with the heating coil 12 as well as the resonance condition with the step-up transformer 13.
The inverter 6 is configured to simultaneously satisfy operating conditions as an induction heating device and conditions as a dielectric heating device. Further, the heating coil 12 and the step-up transformer 13 are also configured to have equivalent circuit constants on an electric circuit.

Problems to be Solved by the Invention In such a conventional high-frequency heating device, the resonant capacitor 7 is switched and connected to the heating coil 12 and the step-up transformer 13, and the inverter 6 is connected under almost the same operating conditions.
The configuration of the heating coil 12 and the step-up transformer 13 mutually imposes constraints on each other.
This made the design extremely complicated. That is, the load on the heating coil 12 is a linear load such as a pan, while the load on the step-up transformer 13 is an extremely non-linear load such as a magnetron. If we optimize with 7, then transistor 8 will be
This causes problems such as unreasonable stress (for example, excessive voltage) being applied to the inverter 6, and the inverter 6 has the drawback of not being able to demonstrate its full capacity (output).

Furthermore, since the heating coil 12 and step-up transformer 13 are configured to be switched by the changeover switch 11, induction heating and dielectric heating cannot be used simultaneously, which is disadvantageous in terms of improving cooking performance, for example. There were drawbacks.

Means for Solving the Problems The present invention has been made in order to eliminate such conventional drawbacks, and has the following configuration. That is, a power source obtained from a commercial power source, a first resonant circuit composed of a first resonant capacitor and a step-up transformer, a second resonant circuit composed of a second resonant capacitor and a heating coil, or more switch elements, and the first
And one or more of the second resonant circuits is a high frequency heating device configured with connection means for connecting both of them to the switching element.

Effect of the Invention The present invention realizes a resonant inverter with the above-mentioned configuration, which makes it possible to independently optimize the inverter operating conditions during heating coil operation and the inverter operating conditions during step-up transformer operation. This has the effect of making it possible to configure a high-frequency heating device that can perform both heating and induction heating at the same time.

Example An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of one implementation of the present invention, and the same reference numerals as in FIG. 5 are corresponding components, and their explanation will be omitted.

In the figure, the step-up transformer 13 forms a first resonant circuit together with the first resonant capacitor 7a, while the heating coil 12 forms a second resonant circuit together with the second resonant capacitor 7b. Therefore, these two resonant circuits are configured so that each can independently realize optimal inverter operation, and can output sufficient operating capability of the inverter 6 as their respective outputs. For example, the first and second resonant circuits are configured so that the voltage applied to the transistor 8 can be suppressed below the maximum allowable value and sufficient respective outputs can be obtained.

The two resonant circuits are connected to contacts 2 of the first and second relays 20 and 21, respectively, which are controlled by the control circuit 1o.
2 and 23 are configured to be connected to the transistor 8 selectively or simultaneously, and this relay circuit forms a connecting means 24.

In addition, the input current to the inverter 6 is monitored by the current transformer 26, and upon receiving this signal, the control circuit 10 controls the conduction time of the transistor 8 so that the total input current is maintained at a predetermined value. As a result, the output of the inverter 6 is maintained at a predetermined value.

FIG. 2 is an operation sequence diagram showing the operation mode of the high-frequency heating device shown in FIG. 1, and FIG.
) indicates a mode in which the heating coil 12 operates and performs induction heating. At the same time, it is clear that in both regions A and 8, only dielectric heating and induction heating are performed, respectively, and in region C
Both of these heatings are performed simultaneously in the region. The respective heating outputs are controlled to be approximately H each as shown in the figure. This is achieved by designing the resonant frequencies of the first and second resonant circuits to be approximately equal, and by making their characteristic impedances approximately equal, and performs input current control that maintains a constant input current as described below. This can be achieved by

FIG. 3 is a preliminary block diagram for explaining input current control. The input current supplied from the commercial power source 1 to the input current 6 is monitored by the current source 26 and fed back to the foot check circuit 26 of the control circuit 10.The output of this foot check circuit 26 is the input current. It is compared with the signal of the setting device 27 and the error signal is sent to the transistor control circuit 28. Based on this error signal,
Since the transistor control circuit 28 controls the conduction time (pulse width control) of the transistor 8, the input current is maintained at a predetermined value. Therefore, when the heating coil 12 and the step-up transformer 13 are connected simultaneously by the connecting means 24, the resulting output of each is approximately % of that when they operate independently.

FIG. 4 shows one embodiment of the configuration of a high-frequency heating device to which the present invention is applied, and the same reference numerals as in FIG. 1 represent corresponding components.

The heating coil 12 is mounted on the top of the open 30 using aluminum.

Installed through a magnetic shield 31 such as ferrite,
An induction heated object 14 such as a pan is placed on a non-magnetic placing plate 32.
The structure is such that In this embodiment, the heating coil is configured to heat cooking utensils such as a pan, but the magnetic shield 31 is removed and the open 3
It is clear that if the configuration is such that the heating coil M2 is used to heat the heating coil M2, and the induction heating is open, a high-frequency heating device that effectively utilizes simultaneous heating, which is an effect of the present invention, can be realized.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained.

In other words, since the configuration is such that the first and second resonant circuits are provided and connected to the switch element by the connecting means, the configurations of the step-up transformer and the heating coil were independently optimized, and the configuration was optimized for each. By optimizing the inverter, you can bring out the maximum potential of the switching elements.
The most rational and low-cost high-frequency heating device can be realized.

Furthermore, since the step-up transformer and the heating coil can be connected to the switch element and operated at the same time using the connecting means, it is possible to perform complex cooking at the same time, providing a high-frequency heating device with greatly improved cooking performance. can do.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a high-frequency heating device showing an embodiment of the present invention, Fig. 2 (-) and (b) are diagrams explaining the operating modes of the device, and Fig. 3 explains feedback control of the device. Fig. 4 is a cross-sectional view showing the configuration of the device, Fig. 6 is a circuit diagram of a conventional high-frequency heating device, Fig. 6(a)
, (b)/Ii is an operating current and voltage waveform diagram of the same device. 6... Power supply section, 7a... First resonant capacitor, 7b... Second resonant capacitor, 8
......Switch element, 12...Heating coil, 13...Step-up transformer, 24...
Connection means. Name of agent: Patent attorney Toshio Nakao and 1 other person5-
Electric J evil 8-switch element 12-sword heating coil 13-#-to pressure transformer-! ffi+ Stage 1 Figure 1I2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (3)

[Claims] (1) A power source obtained from a commercial power source, a first resonant circuit consisting of a first resonant capacitor and a step-up transformer, and a second resonant circuit consisting of a second resonant capacitor and a heating coil.
A high-frequency heating device comprising a resonant circuit, one or more switching elements, and connecting means for connecting one or both of the first and second resonant circuits to the switching element. (2) The high-frequency heating device according to claim 1, wherein the connecting means includes two relays, and selective activation of the two relays connects the two resonant circuits to the switch element. (3) The high-frequency heating device according to claim 1, wherein the two resonant circuits are configured so that the resonant frequencies of the resonant circuits are approximately equal.