JPS63187589A - Induction heating cooker - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to an induction heating cooker for general household use.

Conventional technology An example of a conventional induction heating cooker is shown in FIG.

In Figure 2, an AC power supply 1, a rectifier 2, a current transformer 3
This constitutes a DC power source 4. 6 is a choke coil, 6 is an inverter, and the inverter 6 is a smoothing capacitor 7, a heating coil 8. Co-meng capacitor 9. at least one switching transistor 10. Reverse conducting diode 1
1. 12 is a control circuit for the inverter 6; 13 is a rectifier circuit for rectifying the output of the current transformer 3;
14 is input current setting means for setting the input current of the cooker;
16 is a load pot.

The operation in the above configuration will be explained. The control circuit 12 is
The switching transistor 1o is turned on and off. By turning on and off the switching transistor 10,
A high frequency current flows through the resonant circuit of the heating coil 8 and the resonant capacitor 9, heating the pot 16. Further, the output of the current transformer 3 is rectified by a rectifier circuit 13, and the rectifier circuit 13 outputs a voltage v1 proportional to the input current in to the control circuit 12. The control circuit 12 has vl and input current setting means 1.
The switching traverse/raster 1001 operation time is controlled so that the output voltages 2 and 4 are equal.

Further, another conventional induction heating cooker is shown in FIG. Third
In the figure, AC power supply 1. The rectifier 2 constitutes a power source 4. 5 is a choke coil connected in series to an inverter 6, and this series circuit is connected to a power source 4. The inverter 6 is the same as the inverter shown in FIG.
Heating coil 8° resonant capacitor 9. It has a switching transistor 1° and a reverse conduction diode 11.

12 is a control circuit connected to the switching transistor 10, 14 is an input current setting means, 16 is a resistor, and 17 is an amplifier that amplifies the voltage across the resistor 16.

The operation in the above configuration will be explained. The resistor 16 generates a DC voltage v3 proportional to the input current of the inverter 6 at both ends thereof. The amplifier 17 amplifies the voltage v3 across the resistor 16 and outputs the voltage v4 to the control circuit 12. The control circuit 12 controls the on-time of the switching transistor 10 so that v4 and the output voltage v6 of the input current setting means 14 become equal.

Problems to be Solved by the Invention In the former conventional configuration, a current transformer 3 is required, but the winding on the secondary side of the current transformer 3 is very thin.
Since a very large number of turns is required, there are problems in that it is time consuming and expensive.

In addition, in the latter conventional configuration, the power loss due to the resistance is large, so the resistor 16 with high power is required, resulting in high cost. Furthermore, since the temperature inside the cooker becomes high, the switching transistor 10 and the like are likely to be destroyed and the control circuit 12 malfunctions, and the efficiency is also reduced due to power loss caused by the resistance.

In view of these problems, the present invention reduces costs by eliminating the need for expensive current transformers and high-power resistors, and eliminates power loss caused by resistors, thereby lowering the temperature of the cooker and preventing malfunctions. .

To provide an induction heating cooker that is difficult to break and has high efficiency.

Means for Solving the Problems In order to solve the above problems, the induction heating cooker of the present invention includes an inverter including at least one switching element, a choke coil connected in series to the inverter, and a choke coil connected in series to the inverter. It has a power supply connected to a series circuit of an inverter and a choke coil, and a control circuit connected to the switching element, and the control circuit detects an input current based on a terminal voltage of the choke coil and controls switching of the switching element. It is something.

Effect With the above-described configuration, the induction heating cooker of the present invention can eliminate the need for an expensive current transformer or a high-power resistor, and can eliminate power loss due to a high-power resistor at a low cost. .

EXAMPLE An example of the present invention will be described below with reference to FIG. FIG. 1 is a circuit diagram of an induction heating cooker according to an embodiment of the present invention. In FIG. 1, the configurations of a power source 4, choke coil 6, and inverter 6 are the same as the conventional configuration shown in FIG. 3, and the same parts are given the same reference numerals and detailed explanation thereof will be omitted. A low-pass filter 18 removes, from the waveform of the voltage v6 across the choke coil 5, at least the operating frequency components of the inverters whose magnitude changes depending on the type of pot, and outputs the voltage v7 to the amplifier 19. The amplifier 19 outputs the voltage 8 from the input voltage v7 to the control circuit 12. The control circuit 12 controls the on-time of the switching transistor 1° so that the T voltage 8 becomes equal to the output voltage v9 of the input current setting means 14. The DC resistance of the choke coil 6 is normally around 100 mΩ, so
When the input current is 12 A in effective value, a peak value of 1.7 cm can be obtained as voltage v7 just outside the DC resistance. Furthermore, there is a choke coil actance at a commercial frequency of 50 to 60 L, and if a low-pass filter that passes the commercial frequency is used, an even larger voltage can be obtained.

In the embodiment of the present invention, a choke coil is provided between a DC power source and an inverter that operates by inputting DC voltage.
The input current is detected by the terminal voltage of the choke coil, but it does not necessarily have to be direct current; instead, a choke coil is installed between an AC power source and an inverter that operates by inputting AC voltage, and the terminal voltage of the choke coil is The input current may be detected by

Furthermore, if a change in the input voltage detection characteristics due to a change in the temperature of the choke coil becomes a problem, a method of compensating for this by providing a temperature detection means near the choke coil may be considered.

Effects of the Invention As is clear from the above embodiments, the induction heating cooker of the present invention detects the input current by the terminal voltage of the choke coil connected in series with the inverter, thereby reducing the need for expensive current transformers and high power. By eliminating the need for a resistor, costs can be reduced. Furthermore, power loss due to resistance can be eliminated. Therefore, it is possible to provide a highly efficient induction heating cooker that is less likely to malfunction or break by lowering the temperature of the cooker.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an induction heating cooker showing an embodiment of the present invention, FIG. 2 is a circuit diagram of an induction cooking device showing a first conventional technique, and FIG. 3 is a second conventional technique. It is a circuit diagram of an induction heating cooker showing. 4...Power supply, 6...Choke coil,
6... Inverter, 10... Switching element (switching transistor), 12...
・Control circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person1-
・AC electricity! , IC) - switching transistor 2 - inductor An H - inductive 4 - diode 4 - current
Rin 12-Control! t1 circuit 5-1-s-Kukoi LI,! ,−,Input! ,? L stage determining means 6-in-park 15-sensor 7-volume capital condensation 18. -Ronodezu Filter 8
・-! ! a Tsuru coil 19-・-Increase t% 9-Hyodo condensation Figure 1/be 1,-A.C.? -Hyouni Continsa 2-Rectification h
10-Switching transistor 3-Current transformer 11-Reverse conduction diode 4-Electrical terminal
12- Control! 1 circuit 5-+3-Kukoi L 13-Circuit 6-Inverter I4-Manual power flow standard R7-Smoothing capacitor +5-Yu 8-Sword heat coil Fig. 2

Claims (1)

[Claims] an inverter including at least one switching element, a choke coil connected in series to the inverter, a power supply connected to a series circuit of the inverter and choke coil, and a control circuit connected to the switching element; The control circuit detects an input current based on the terminal voltage of the choke coil, and controls switching of the switching element.