JPS6340290A - Induction heating cooker - Google Patents

Abstract

(57) [Abstract] 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.

Prior Art A circuit diagram of this type of induction heating cooker in the prior art is shown in FIG. In FIG. 4, 1 is an AC power supply, 2 is a rectifier for rectifying the AC power supply 1, 3 is a capacitor connected in parallel to the rectified output of the rectifier 2 to absorb abnormal voltage, etc., and 6 is a capacitor for reducing current ripple. The rectifier 2 , the capacitor 3 , and the current limiting coil 6 constitute a power supply circuit 7 . 8 is a heating coil, 9 is a resonant capacitor connected to both ends of the heating coil 8, and 10 and 11 are switching elements, such as transistors.

12 is a control circuit for controlling on/off of the switching elements 10 and 11, and 13 is a pot.

Next, the operation of the conventional circuit shown in FIG. 4 will be briefly explained. In steady operation, switching elements 10 and 1
1 is turned on alternately to excite resonance between the heating coil 8 and the resonant capacitor 9, and the resonant current applied to the heating coil 8 inductively heats the pan 13 magnetically coupled to the heating coil 8. For example, they are inserted in order to prevent the rectified output of the rectifier 2 from rising rapidly during a power supply abnormality such as a lightning surge or instantaneous power outage, thereby preventing the switching elements 10 and 11 from being destroyed.

Problems to be Solved by the Invention However, in such a conventional configuration, since the capacitor 3 is always connected in parallel to the rectified output, charging and discharging are repeated every cycle of the AC power supply. Therefore, there are problems in that the power factor of the load as seen from the AC power supply decreases, and the current for charging and discharging the capacitor is large, resulting in the capacitor being large and expensive.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to make a capacitor small and inexpensive without reducing the power factor.

Means for Solving the Problems In order to achieve this object, the induction heating cooker of the present invention includes an AC power source, a rectifier for rectifying the AC power source, and a series circuit of a diode and a capacitor connected in parallel to the rectified output side. and a power supply circuit configured by connecting current limiting coils in series, a heating coil whose midpoint terminal or one terminal is connected to one terminal of the power supply circuit, and a resonant capacitor connected between both terminals of the heating coil. , a pair of switching elements connected from both ends of the heating coil to the other terminal of the power supply circuit, and a control circuit that controls on/off of the switching element.

Function: With the above configuration, the present invention charges the capacitor connected in parallel to the rectified output of the rectifier only in the event of a power supply abnormality such as a lightning surge or instantaneous power outage, so charging and discharging are repeated every cycle of the AC power supply. Therefore, the power factor does not decrease, and the current for charging and discharging the capacitor becomes small.

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of an induction heating cooker according to an embodiment of the present invention. In Figure 1, 1 is an AC power supply;
2 is a rectifier for rectifying the AC power supply 1; 3 is a diode; 4 is a capacitor connected in parallel to the rectifier output side of the rectifier 2 via the diode 3 to absorb abnormal voltage; and 6 is a capacitor for reducing current ripple. Rectifier 2 with current limiting coil
- A power supply circuit 7 is constituted by a series circuit of a diode 3 and a capacitor 4 and a current limiting coil 6.

8 is a heating coil whose midpoint terminal is connected to one terminal of the power supply circuit 7, 9 is a resonant capacitor connected between both terminals of the heating coil 8, and 1o and 11 are connected from both ends of the heating coil 8 to the other terminal of the power supply circuit. A pair of switching elements each connected to a terminal, for example, a transistor. 12 is a control circuit that controls on/off of the switching elements 10 and 11, and 13 is a pot.

Next, the operation of the configuration of this embodiment will be explained. In steady operation, as in the conventional example, switching element 1
o and 11 are turned on alternately to excite resonance between the heating coil 8 and the resonant capacitor 9, and the pot 13 magnetically coupled to the heating coil 8 is inductively heated by the resonance current applied to the heating coil 8. The capacitor 4 is normally charged to the peak value voltage of the rectified output of the rectifier 2 and is not charged or discharged. However, in the event of a power supply abnormality such as a lightning surge or instantaneous power outage, it functions to absorb the abnormality.

FIG. 2 is a circuit diagram of an induction heating cooker according to a second embodiment of the present invention, in which a discharge resistor 5 is connected in parallel to a capacitor 4. According to this configuration, since the charge in the capacitor 4 can be quickly discharged, it is possible to prevent the absorption capacity of the capacitor 4 from decreasing when power supply abnormalities such as lightning surges and instantaneous power outages are continuously applied.

FIG. 3 is a circuit diagram of an induction heating cooker according to another embodiment of the present invention. Although one terminal of the heating coil 8 is connected to one terminal of the power supply circuit, the operation is similar to the circuit shown in FIG. 1.

In each of the embodiments described above, the switching element is a reverse blocking type transistor, but it is clear that similar effects can be obtained with other switching elements including a reverse conducting type.

Effects of the Invention As described above, according to the induction heating cooker of the present invention, since the capacitor connected in parallel to the rectified output of the rectifier is charged only in the event of a power abnormality such as a lightning surge or instantaneous power outage, it is possible to use an AC power supply. Since charging and discharging are not repeated every cycle of the capacitor, the power factor does not decrease, and the charging and discharging current of the capacitor is also small, making it possible to make the capacitor smaller and cheaper. , its practical effect is a dog.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an induction cooking device according to an embodiment of the present invention, FIG. 2 is a circuit diagram of an induction cooking device according to a second embodiment of the invention, and FIG. 3 is a circuit diagram of an induction cooking device according to a second embodiment of the invention. FIG. 4 is a circuit diagram of an induction cooking device according to an embodiment of the present invention, and FIG. 4 is a circuit diagram of a conventional induction cooking device. 1... AC power supply, 2... Rectifier, 3.
...Diode, 4...Capacitor, 5
...Discharge resistance, 6...Current limiting coil, 7
...Power circuit, 8...Heating coil, 9
...Resonance capacitor, 10, 11...
Switching element, 12... Control circuit, 13.
·····pot. Name of agent: Patent attorney Toshio Nakao et al.
1 Figure 13 Tahanawa Figure 3 Figure 13 Burning Figure 4, 3 Yu

Claims (2)

[Claims] (1) A power supply circuit consisting of an AC power source, a rectifier that rectifies the AC power source, a series circuit of a diode and a capacitor connected in parallel to the rectified output side, and a current limiting coil connected in series, and a midpoint terminal or one side. a heating coil whose terminal is connected to one terminal of the power supply circuit; a resonant capacitor connected between both terminals of the heating coil; and a pair of resonant capacitors connected from both ends of the heating coil to the other terminal of the power supply circuit. An induction heating cooker including a switching element and a control circuit that controls on/off of the switching element. (2) The induction heating cooker according to claim 1, wherein the power supply circuit has a capacitor connected in parallel with a discharge resistor.