JP2008210743A - Induction-heating cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction-heating cooker which can control an input power to each of heaters even if a power source circuit side is used commonly for a plurality of heaters. <P>SOLUTION: The induction-heating cooker is provided with a plurality of inverter circuits 5a to 5c which convert an output of a rectifier circuit 2 into a high frequency voltage and impress each of heating coils 10a to 10c, a plurality of filter capacitors 13a to 13c provided on an input side of each of a plurality of the inverter circuits 5a to 5c, a plurality of current detecting resistors 14a to 14c each inserted between the rectifier circuit 2 and a plurality of filter capacitors 13a to 13c and input current detecting means 16a to 16c for detecting an input current of each of the inverter circuits 5a to 5c from voltages generated in a plurality of the current detecting resistors 14a to 14c. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an induction heating cooker having a plurality of heating ports.

A conventional induction heating cooker includes, for each of a plurality of heating ports, a current transformer and an input current detection circuit that detect an input current from a commercial AC power supply, and a rectifier circuit and an inverter circuit that convert the commercial AC power supply to a DC power supply. The input current is detected for each heating port, the drive signal of the inverter circuit is controlled, and the input power is adjusted (for example, Patent Document 1).
In addition, as this type of induction heating cooker, there is a type including a common rectifier circuit, a choke coil, a filter capacitor, and an inverter circuit for each heating port for a plurality of heating ports (for example, Patent Document 2).

JP 2001-267052 A JP 58-169791 A

  However, the current transformer and the input current detection circuit for detecting the input current from the commercial AC power supply of Patent Document 1 are applied to the circuit configuration that is reduced in size and cost by sharing the power supply circuit such as the rectifier circuit shown in Patent Document 2. Even so, there is a problem that only the input current combining the plurality of heating ports can be detected, and the input power cannot be individually controlled for each heating port.

  The present invention has been made to solve the above-described problems, and provides an induction heating cooker that can control input power for each heating port even if the power supply circuit side is made common to a plurality of heating ports. The purpose is to do.

  An induction heating cooker according to the present invention includes a rectifier circuit that rectifies a commercial power supply, a plurality of inverter circuits that convert an output of the rectifier circuit into a high-frequency voltage, and that is applied to individual heating coils, and an input side of the plurality of inverter circuits The input currents of the individual inverter circuits are obtained from the plurality of filter capacitors respectively provided in the circuit, the plurality of current detection resistors inserted between the rectifier circuit and the plurality of filter capacitors, and the voltages generated in the plurality of current detection resistors. Input current detecting means for detecting.

  In the present invention, the filter capacitors provided on the input sides of the plurality of inverter circuits prevent leakage of the high-frequency current generated by the inverter circuits to the rectifier circuit side, and are provided between the rectifier circuits and the filter capacitors. Since the input current for each inverter circuit is detected from the voltage generated by the low-frequency current flowing through the plurality of current detection resistors, the input power of each heating coil can be controlled.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a circuit configuration of an induction heating cooker according to Embodiment 1 of the present invention, and FIG. 2 is a diagram showing a configuration of an input current detection circuit of the induction heating cooker according to Embodiment 1.
In FIG. 1, low-frequency AC power of a commercial AC power supply 1 is converted into DC power by a rectifier circuit 2, and the voltage is detected by an input voltage detector 3. The electric power converted into direct current by the rectifier circuit 2 is input to, for example, three inverter circuits 5a, 5b, and 5c through the choke coil 4, respectively.

  The inverter circuit 5a includes two switching elements 6a and 7a connected in series between the outputs of the rectifier circuit 2 (hereinafter, the switching element 6a is referred to as “upper switch 6a” and the switching element 7a is referred to as “lower switch 7a”). And diodes 8a and 9a connected in antiparallel to the upper and lower switches 6a and 7a, respectively, and a heating circuit 10a and a load circuit for the resonant capacitor 11a connected in parallel to the lower switch 7a. The upper switch 6a and the lower switch 7a are alternately turned on and off by a drive signal from the drive circuit 12a to generate a high-frequency voltage, and a high-frequency current flows through the heating coil 10a and the resonance capacitor 11a of the load circuit. The high-frequency current flowing through the load circuit also flows through the upper switch 6a and its antiparallel diode 8a, but the leakage of the high-frequency current to the rectifier circuit 2 side is suppressed by the filter capacitor 13a provided on the input side of the inverter circuit 5a. ing.

  As described above, since the high-frequency current generated in the inverter circuit 5a is bypassed by the filter capacitor 13a and leakage to the rectifier circuit 2 side is suppressed, the low-frequency current is almost between the filter capacitor 13a and the rectifier circuit 2. Only input current flows. A series circuit of a current detection resistor 14a and a backflow blocking diode 15a is provided between the filter capacitor 13a and the rectifier circuit 2, and the input current detection circuit 16a detects a voltage generated in the current detection resistor 14a due to a low frequency input current. . As shown in FIG. 2, the input current detection circuit 16a is composed of a differential amplifier circuit 18a and a filter circuit 19a, and the amplitude of the voltage generated in the current detection resistor 14a is adjusted by the differential amplifier circuit 18a. Detected, smoothed by the filter circuit 19a, and output to the control unit 17. The reverse current blocking diode 15a connected in series with the current detection resistor 14a is for preventing current caused by the operation of the other inverter circuits 5b and 5c connected in parallel from flowing into the current detection resistor 14a.

  The other inverter circuits 5b and 5c shown in FIG. 1 have the same configuration as the inverter circuit 5a described above, and the input current detection circuits 16b and 16c on the inverter circuits 5b and 5c side are the input current detection circuits described above. The configuration is the same as that of 16a, and the description is omitted.

  The control unit 17 is a circuit unit that controls the entire induction heating cooker, and controls the three inverter circuits 5a, 5b, and 5c, respectively, and the input voltage detected by the input voltage detector 3 and each inverter circuit. The individual input power of each heating port is calculated from the input current detected by the input current detection circuits 16a, 16b, and 16c provided in 5a, 5b, and 5c, and the thermal power (power) set for each heating port is calculated. ) To control the drive circuits 12a, 12b, 12c of the inverter circuits 5a, 5b, 5c. That is, the input power is controlled to be the same as the thermal power.

As described above, according to the first embodiment, since the filter capacitors 13a to 13c are provided on the input sides of the three inverter circuits 5a, 5b, and 5c, the high-frequency current generated by each inverter circuit 5a, 5b, and 5c. Can be prevented from leaking to the rectifier circuit 2 side.
Further, current detection resistors 14a to 14c are inserted between the rectifier circuit 2 and the filter capacitors 13a to 13c, respectively, and the input of each inverter circuit 5a, 5b, and 5c from the voltage generated by the low-frequency current flowing through the resistors 14a to 14c. Since the input current detection circuits 16a to 16c for detecting the currents are provided, the input power can be controlled for each heating port. For this reason, the rectifier circuit 2 and the choke coil 4 can be shared with respect to the three inverter circuits 5a, 5b, and 5c, and the circuit can be reduced in size and cost.

Embodiment 2. FIG.
In the first embodiment, the half-bridge type is used as the inverter circuits 5a to 5c for the plurality of heating ports. However, the second embodiment includes half-bridge type and full-bridge type inverter circuits. It is.
FIG. 3 is a diagram showing a circuit configuration of the induction heating cooker according to the second embodiment. In the second embodiment, the other components are the same as those in the first embodiment described with reference to FIG. 1 except for the full bridge inverter circuit 5d.
A filter capacitor 13d that bypasses high-frequency current generated in the inverter circuit 5d and prevents leakage to the rectifier circuit 2 side is provided on the input side of the full-bridge inverter circuit 5d. Further, an input current detection circuit for detecting an input current from a voltage generated by a low-frequency input current flowing through the current detection resistor 14d is inserted between the filter capacitor 13d and the rectifier circuit 2 with a current detection resistor 14d and a backflow blocking diode 15d. 16d is provided.

  In the second embodiment, since the filter capacitors 13d and 13e are provided on the input sides of the full-bridge and half-bridge inverter circuits 5d and 5e, respectively, a rectifier circuit for high-frequency current generated by the inverter circuits 5d and 5e. Leakage to the second side can be prevented. Further, current detection resistors 14d and 14e are inserted between the rectifier circuit 2 and the filter capacitors 13d and 13e, respectively, and the input current of each inverter circuit 5d and 5e is obtained from the voltage generated by the low-frequency current flowing through the resistors 14d and 14e. Since the input current detection circuits 16d and 16e for detecting each are provided, the input power can be controlled for each heating port. For this reason, it becomes possible to share the rectifier circuit 2 and the choke coil 4 with respect to the two inverter circuits 5d and 5e, and the circuit can be reduced in size and cost.

Embodiment 3 FIG.
In the first and second embodiments described above, the rectifier circuit 2 and the choke coil 4 are shared with respect to the plurality of inverter circuits 5a to 5c, 5d, and 5e. However, in the third embodiment, as shown in FIG. The choke coils 4f and 4g are inserted on the input sides of the inverter circuits 5f and 5g, respectively.
Also in this configuration, since the filter capacitors 13f and 13g are provided on the input sides of the two inverter circuits 5f and 5g, the leakage of the high-frequency current generated by the inverter circuits 5f and 5g to the rectifier circuit 2 side. Can be prevented. Further, current detection resistors 14f and 14g are inserted between the rectifier circuit 2 and the filter capacitors 13f and 13g, respectively, and the input current of each inverter circuit 5f and 5g is obtained from the voltage generated by the low frequency current flowing through the resistors 14f and 14g. Since the input current detection circuits 16f and 16g for detecting each are provided, the input power can be controlled for each heating port.

  In FIG. 4, the choke coils 4f and 4g are arranged between the high potential side output of the rectifier circuit 2 and the filter capacitors 13f and 13g. However, as shown in FIG. It is good also as arranging between 13g. With this configuration, since the high potential side of the input power supply of the plurality of inverter circuits can be made common as in the first and second embodiments, a plurality of IGBTs as shown in FIG. 6 are incorporated. It is also possible to use a power module (a module in which the high potential side power input is a common terminal and the low potential side power input is an individual terminal), and the circuit configuration can be further reduced in size.

It is a figure which shows the circuit structure of the induction heating cooking appliance in Embodiment 1 of this invention. 3 is a diagram showing a configuration of an input current detection circuit of the induction heating cooker in Embodiment 1. FIG. It is a figure which shows the circuit structure of the induction heating cooking appliance in Embodiment 2. FIG. It is a figure which shows the circuit structure of the induction heating cooking appliance in Embodiment 3. FIG. It is a figure which shows another circuit structure of the induction heating cooking appliance in Embodiment 3. FIG. It is a figure which shows an example of the circuit structure of the power module which incorporates several IGBT.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Commercial AC power supply, 2 Rectifier circuit, 3 Input voltage detector, 4 Choke coil, 5a-g Inverter circuit, 10a-10g Heating coil, 13a-13g Filter capacitor, 14a-14g Current detection resistor, 15a-15g Backflow prevention diode , 16a to 16g Input current detection circuit, 17 control unit.

Claims (2)

A rectifier circuit for rectifying an AC power supply;
A plurality of inverter circuits that convert the output of the rectifier circuit into a high-frequency voltage and apply it to individual heating coils;
A plurality of filter capacitors respectively provided on the input side of the plurality of inverter circuits;
A plurality of current detection resistors respectively inserted between the rectifier circuit and the plurality of filter capacitors;
An induction heating cooker comprising: input current detection means for detecting an input current of each inverter circuit from voltages generated in the plurality of current detection resistors.   2. The induction heating cooker according to claim 1, further comprising reverse current blocking diodes connected in series to the current detection resistor and blocking currents from other inverter circuits.

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