JP2005149915A - Induction heating cooking appliance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating cooking appliance in which switching loss and capacity of switching elements are made not to be large, generated heat of the switching elements is low, and damping of oscillating current is suppressed. <P>SOLUTION: A control circuit 12 alternately switches and actuates a set of a first and second switching elements 4, 5, and a set of a third and fourth switching elements 6, 7. In switching, the second and fourth switching elements 5, 7 are controllably actuated so that a heating coil 8 and a resonance capacitor 9 connected in series make a closed loop, thereby causing the oscillating current of a resonance frequency determined by the inductance of the heating coil 8 and the capacity of the resonance capacitor 9 to flow. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an induction heating cooker that induction-heats, for example, an aluminum pan or a copper pan using a high-frequency magnetic field.

In this type of conventional induction heating cooker, the first switching element is turned on to allow current to flow from the power source to the heating coil, and then the first switching element is turned off, and then the second switching element is turned on. Then, a series circuit is formed by the heating coil and the resonance capacitor, and an oscillating current flows through the heating coil. At this time, the current of several cycles is vibrated by one switching of the second switching element, and a current having an oscillation frequency higher than the switching frequency is generated to heat the aluminum pan (see, for example, Patent Document 1). .
JP 2001-160484 A (page 8, FIGS. 1 and 2)

  However, since the above-described conventional induction heating cooker supplies the energy of the vibration current for several cycles to the load through switching only once in one cycle, the current flowing through the switching element increases and the capacity increases. A large switching element is required, and heat generation of the switching element is also large. Moreover, the oscillating current was attenuated, and the aluminum pan could not be heated sufficiently.

  The present invention has been made to solve such a problem, and does not increase the switching loss and capacity of the switching element, generates little heat from the switching element, and can suppress the attenuation of the oscillating current. The purpose is to provide a cooker.

  An induction heating cooker according to the present invention includes a DC power supply circuit, a heating coil and a resonant capacitor connected in series, a first switching element inserted between the positive electrode side of the DC power supply circuit and the heating coil, A second switching element inserted between the resonance capacitor and the negative electrode side of the DC power supply circuit, and a third switching element inserted between the positive electrode side of the DC power supply circuit and the connection point of the resonance capacitor and the second switching element. Switching element, a fourth switching element inserted between the connection point of the first switching element and the heating coil and the negative electrode side of the DC power supply circuit, a set of the first and second switching elements, and a third And a control unit for controlling the driving of the second and fourth switching elements at the time of switching. That.

  In the present invention, the first and second switching elements and the third and fourth switching elements are alternately switched and driven, and at the time of switching, the second and fourth switching elements are driven. Since it is controlled, an oscillating current several times the switching frequency can be passed through the heating coil, so that an aluminum or copper pan with a low resistance can be heated without increasing the switching loss. Since the first and third switching elements are driven alternately, the pulse width of the current flowing through the two switching elements can be reduced, there is no need to use a switching element having a large capacity, and heat generation due to the current is reduced. And attenuation of the oscillating current can be suppressed, and an efficient induction heating cooker can be provided.

Embodiment 1 FIG.
FIG. 1 is a circuit diagram of an induction heating cooker showing Embodiment 1 of the present invention. The rectifier circuit 2 shown in FIG. 1 performs full-wave rectification on the AC voltage of the commercial power supply 1, and the smoothing capacitor 3 smoothes the voltage that has been full-wave rectified by the rectifier circuit 2. The first switching element 4 is inserted between the positive electrode side of the smoothing capacitor 3 and the heating coil 8 provided on the bottom surface of the top plate 10 on which the pan 11 is placed, and the second switching element 5 is composed of the heating coil 8. Are inserted between the resonance capacitor 9 connected in series to the negative electrode side of the smoothing capacitor 3. The third switching element 6 is inserted between the positive electrode side of the smoothing capacitor 3 and the connection point of the resonant capacitor 9 and the second switching element 5, and the fourth switching element 7 is the first switching element. 4 and the connection point of the heating coil 8 and the negative electrode side of the smoothing capacitor 3. Each of the switching elements 4, 5, 6, 7 described above is composed of, for example, an insulated gate bipolar transistor, and has a built-in diode for power regeneration. The oscillating current detection resistor 13 is inserted on the emitter side of the second and fourth switching elements 5 and 7 and is provided to detect the direction in which an oscillating current I which will be described later flows.

  The control circuit 12 is driven by alternately switching the set of the first and second switching elements 4 and 5 and the set of the third and fourth switching elements 6 and 7 and is connected in series at the time of switching. The second and fourth switching elements 5 and 7 are driven and controlled so that the heating coil 8 and the resonant capacitor 9 are in a closed loop. When the series circuit becomes a closed loop, an oscillating current I flows at a resonance frequency determined by the inductance of the heating coil 8 and the capacitance of the resonance capacitor 9. This oscillating current I has a frequency several times the switching frequency (high frequency) for driving each switching element 4, 5, 6, 7.

  Further, the control circuit 12 is configured such that when the oscillating current I flows in the direction of the built-in diode of the heating coil 8 → the resonant capacitor 9 → the second switching element 5 → the oscillating current detection resistor 13 → the fourth switching element 7. The direction of the current is determined to be positive, and the oscillating current I flows in the direction of the built-in diode of the resonant capacitor 9 → the heating coil 8 → the fourth switching element 7 → the oscillating current detecting resistor 13 → the second switching element 5. If it is, the direction is determined as a negative direction, and the switching timing of each switching element 4, 5, 6, 7 is determined based on the direction of the oscillating current. This switching is performed, for example, every time the waveform of the oscillating current I repeats one and a half cycles, and direct currents Ia and Ib (hereinafter simply referred to as “currents Ia and Ib”) are supplied to the heating coil 8 and the resonant capacitor 9. A magnetic flux is generated from the heating coil 8 by the vibration current I, and an eddy current is generated in the aluminum or copper pan 11 placed on the top plate 10 by the magnetic flux, and the pan 11 is heated.

Next, operation | movement of the induction heating cooking appliance of Embodiment 1 is demonstrated using the wave form diagram shown in FIG. FIG. 2 is a waveform diagram showing the operation of each switching element in the first embodiment and a waveform diagram of an oscillating current flowing by this switching operation.
When cooking is started by a predetermined switch operation, the rectifier circuit 2 full-wave rectifies the AC voltage of the commercial power supply, and the smoothing capacitor 3 smoothes the full-wave rectified voltage. On the other hand, the control circuit 12 turns on the first and second switching elements 4 and 5 and causes the current Ia to flow through the heating coil 8 and the resonance capacitor 9. Thereafter, the first switching element 4 is turned off while the second switching element 5 is turned on, and at the same time, the fourth switching element 7 is turned on. At this time, since the heating coil 8 and the resonant capacitor 9 connected in series are closed loops when the second and fourth switching elements 5 and 7 are turned on, the oscillating current I flows through the closed loop series circuit.

  The control circuit 12 detects the direction of the oscillating current I through the oscillating current detection resistor 13, and turns on the fourth switching element 7 when the direction of the oscillating current I flows from the resonant capacitor 9 toward the heating coil 8. At the same time, the third switching element 6 is turned on while the second switching element 5 is turned off to pass the current b through the resonance capacitor 9 and the heating coil 8. Then, the third switching element 6 is turned off while the fourth switching element 7 is turned on, and at the same time, the second switching element 5 is turned on, and the heating coil 8 and the resonance capacitor 9 are connected to the second and second capacitors. The switching elements 5 and 7 of FIG. 4 are closed again so that the oscillating current I from the resonance capacitor 9 and the heating coil 8 flows.

  Furthermore, when the direction of the oscillating current I is flowing from the heating coil 8 toward the resonant capacitor 9, the first switching element 4 is turned on again with the second switching element 5 turned on, The switching element 7 is turned off, and the current Ia flows through the heating coil 8 and the resonance capacitor 9. Thereafter, the first switching element 4 is turned off while the second switching element 5 is turned on, and at the same time, the fourth switching element 7 is turned on, and the heating coil 8 and the resonant capacitor 9 are connected to the second and second capacitors. The switching elements 5 and 7 are closed loops so that the oscillating current I flows. By repeating this series of operations, an oscillating current I several times the switching frequency flows through the heating coil 8.

  As described above, according to the first embodiment, the set of the first and second switching elements 4 and 5 and the set of the third and fourth switching elements 6 and 7 are alternately switched and driven. At the time of switching, the second and fourth switching elements 5 and 7 are driven and controlled so that the heating coil 8 and the resonance capacitor 9 connected in series are in a closed loop, so that the oscillation current I several times the switching frequency is It becomes possible to flow through the heating coil 8, and therefore, the aluminum or copper pan 11 having a low resistance value can be heated without increasing the switching loss.

  In addition, the energy of the oscillating current I for several cycles is supplied to the heating coil 8 via the second and fourth switching elements 5 and 7 once every half cycle, so that the second and second The driving time of the switching elements 5 and 7 of 4 can be halved compared with the conventional case.

  Further, since the first and third switching elements 4 and 6 are driven alternately, the pulse width of the currents Ia and Ib flowing through the switching elements 4 and 6 can be reduced, and a switching element having a large capacity must be used. Disappears.

  Furthermore, as described above, since the pulse widths of the currents Ia and Ib are small, heat generation due to the current is reduced, and attenuation of the vibration current can be suppressed, and an efficient induction heating cooker can be provided.

Embodiment 2. FIG.
FIG. 3 is a circuit diagram of an induction heating cooker showing Embodiment 2 of the present invention. In addition, the same code | symbol is attached | subjected to the same or equivalent part as Embodiment 1 demonstrated in FIG. 1, and description is abbreviate | omitted.
Although the second embodiment will be described in detail when explaining the operation, the first and second switching elements 4 and 5 and the third and fourth switching elements 6 and 7 are alternately switched and driven (first). 1 and the second and fourth switching elements 5 and 7 are alternately driven (second frequency) at the time of switching, and the connection state of the heating coil 8 and the resonant capacitor 9 is intermittently closed loop. The control circuit 12 is provided.

Next, the operation of the induction cooking device of the second embodiment will be described using the waveform diagram shown in FIG. FIG. 4 is a waveform diagram showing an operation of each switching element in the second embodiment and a waveform diagram of an oscillating current flowing by this switching operation.
When cooking is started by a predetermined switch operation, the rectifier circuit 2 full-wave rectifies the AC voltage of the commercial power supply, and the smoothing capacitor 3 smoothes the full-wave rectified voltage. On the other hand, the control circuit 12 turns on the second switching element 5, turns on the first switching element 4, and causes the current Ia to flow through the heating coil 8 and the resonant capacitor 9. At this time, an oscillating current I having a resonance frequency determined by the inductance of the heating coil 8 and the capacitance of the resonance capacitor 9 is generated, and starts flowing in the direction in which the diode 7a of the fourth switching element 7 is conducted. After that, the first switching element 4 is turned off before the direction of the oscillating current I is reversed. At the same time, the fourth switching element 7 is turned on, and the oscillating current I conducts the diode 5a of the second switching element 5. The second switching element 5 is turned off.

  Further, the second switching element 5 is turned on again before the oscillating current I reverses in the direction of conducting the diode 7a, and the fourth switching element 7 is turned off when the oscillating current I begins to flow in the direction, Then, the fourth switching element 7 is turned on again before the oscillating current I reverses in the direction in which the diode 5a is conducted, and at the same time as the third switching element 6 is turned on when the oscillating current I begins to flow in that direction. The second switching element 5 is turned off, and the current Ib is passed through the heating coil 8 and the resonant capacitor 9. At this time, similarly to the above, an oscillating current I having a resonance frequency determined by the inductance of the heating coil 8 and the capacitance of the resonance capacitor 9 is generated and flows in a direction in which the diode 5a is conducted.

  The control circuit 12 repeatedly performs the series of operations described above, determines the direction of the oscillating current I through the oscillating current detection resistor 13, and switches the switching elements 4, 5, 6, and 7 based on this.

  As described above, according to the second embodiment, when one of the diodes 5a or 7a of the second and fourth switching elements 5 and 7 is conducting, the switching element side having the diode is turned off. Therefore, consumption of driving power for keeping the second and fourth switching elements 5 and 7 in the on state can be suppressed, and the switching is performed while the diode 5a or 7a is conducting. Since no current flows on the element side, switching loss can be greatly suppressed.

  In the second embodiment, the control circuit 12 controls the first and second switching elements 4 and 5 and the third and fourth switching elements 6 and 7 alternately at the first frequency. And the resonant capacitor 9 is charged and the second and fourth switching elements 5 and 7 are alternately driven at the second frequency to generate an oscillating current I by the heating coil 8 and the resonant capacitor 9. Yes. For this reason, the first switching element 4 and the third switching element 6 are driven at a frequency that is ½ or less of that of the second switching element 5 and the fourth switching element 7. Since the period during which current flows through the first switching element 4 and the third switching element 6 is shortened, switching loss can be greatly suppressed. Furthermore, by matching the driving frequency of the second switching element 5 and the fourth switching element 7 with the resonance frequency of the oscillating current I, it is possible to input a large amount of power to the heating coil 8.

Embodiment 3 FIG.
FIG. 5 is a circuit diagram of an induction heating cooker showing Embodiment 3 of the present invention. In addition, the same code | symbol is attached | subjected to the same or equivalent part as Embodiment 1 demonstrated in FIG. 1, and description is abbreviate | omitted.
The induction heating cooker of Embodiment 3 includes, for example, a current detection resistor 13a inserted on the negative electrode side of the smoothing capacitor 3, a normally open relay switch 14 connected in parallel to the resonance capacitor 9, and a current detection unit 15a. And a control circuit 15 having a control switching unit 15b, a first control unit 15c, and a second control unit 15d.

  The current detector 15a of the control circuit 15 detects the current flowing through the heating coil 8 through the voltage generated at both ends of the current detection resistor 13a. When the control switching unit 15b detects the start of cooking based on a predetermined switch operation, the control switching unit 15b operates the first control unit 15c, and the switching elements 4, 5, 6, and 7 of the first control unit 15 are driven. When the current is input via the current detection unit 15a, it is determined whether the current is equal to or greater than a predetermined value. When the current detected by the current detector 15a is greater than or equal to a predetermined value, the second controller 15d is operated. When the detected current is lower than the predetermined value, the relay switch 14 is closed to short-circuit the resonant capacitor 9, Control of each switching element 4, 5, 6, 7 by the 1st control part 15c is continued.

  The first control unit 15c alternately turns on the set of the first and second switching elements 4 and 5 and the set of the third and fourth switching elements 6 and 7 to turn on the high frequency current to the heating coil 8. Shed. Similarly to the control circuit 12 shown in FIG. 1, the second control unit 15 d alternates between the first and second switching elements 4 and 5 and the third and fourth switching elements 6 and 7. At the time of switching, the second and fourth switching elements 5 and 7 are driven and controlled so that the series circuit of the heating coil 8 and the resonant capacitor 9 becomes a closed loop so that the oscillating current I flows.

  In the induction heating cooker configured as described above, the control switching unit 15b of the control circuit 15 operates the first control unit 15c at the start of cooking. As described above, the first controller 15c repeatedly turns on the first and second switching elements 4 and 5 and the third and fourth switching elements 6 and 7 alternately and turns them on. The generated voltage is converted into a high frequency voltage, and a high frequency current is passed through the heating coil 8 and the resonance capacitor 9. At this time, the control switching unit 15b receives the current detected by the current detection unit 15a and determines whether or not the current is equal to or greater than a predetermined value. When the current detected by the current detection unit 15a is equal to or greater than a predetermined value, it is determined that the pan 11 on the top plate 10 is made of aluminum or copper, and the switching elements 4, 5, 6 and 7 are stopped, and the second controller 15d is operated.

  As described above, the second control unit 15d turns on the first and second switching elements 4 and 5 to flow the current Ia through the heating coil 8 and the resonant capacitor 9, and then the second switching element. The first switching element 4 is turned off while 5 is turned on, and at the same time, the fourth switching element 7 is turned on. At this time, the heating coil 8 and the resonance capacitor 9 connected in series become a closed loop when the second and fourth switching elements 5 and 7 are turned on, so that an oscillating current I by the resonance capacitor 9 and the heating coil 8 flows.

  Further, when the direction of the oscillating current I flows from the resonance capacitor 9 to the heating coil 8, the third switching element 6 is turned on while the fourth switching element 7 is kept on, and at the same time, the second switching element is turned on. 5 is turned off, and the current b flows through the resonance capacitor 9 and the heating coil 8. Then, when the oscillating current I flows from the heating coil 8 to the resonance capacitor 9, the third switching element 6 is turned off while the fourth switching element 7 is turned on, and the second switching is performed at the same time as described above. The element 5 is turned on, and the heating coil 8 and the resonance capacitor 9 are closed with the second and fourth switching elements 5 and 7 so that the oscillating current I from the resonance capacitor 9 and the heating coil 8 flows. .

  When the direction of the oscillating current I flows from the heating coil 8 toward the resonance capacitor 9, the first switching element 4 is turned on again while the second switching element 5 is turned on, and the fourth The switching element 7 is turned off, and the current Ia flows through the heating coil 8 and the resonance capacitor 9. Thereafter, the first switching element 4 is turned off while the second switching element 5 is turned on, and at the same time, the fourth switching element 7 is turned on, and the heating coil 8 and the resonant capacitor 9 are connected to the second and second capacitors. The switching elements 5 and 7 are closed loops so that the oscillating current I flows. By repeating this series of operations, an oscillating current I several times the switching frequency flows into the heating coil 8 to generate a magnetic flux, and this magnetic flux causes the aluminum or copper pan 11 placed on the top plate 10 to be generated. An eddy current is generated and the pan 11 is heated.

  When the current detected by the current detector 15a is lower than a predetermined value, the control switching unit 15b determines that the pan 11 on the top plate 10 is iron-based, closes the relay switch 14, and closes the resonance capacitor. 9 is short-circuited, and the control of each switching element 4, 5, 6, 7 by the first controller 15 c is continued. In this case, as shown in FIG. 4, the first and second switching elements 4 and 5 are simultaneously turned on as a set, and then the switching elements 4 and 5 are turned off, and the third and fourth switching elements are turned on. The switching elements 6 and 7 are turned on simultaneously as a set, and this operation is repeated to pass a high-frequency current I through the heating coil 8.

  As described above, according to the third embodiment, the first controller 15c alternately sets the first and second switching elements 4, 5 and the third and fourth switching elements 6, 7 alternately. If the current flowing through the heating coil 8 is greater than or equal to a predetermined value at this time, it is determined that the pan 11 is made of aluminum or copper, and the second control unit 15d causes the vibration current I to flow through the heating coil 8. When the current is lower than the predetermined value, it is determined as the iron pan 11 and the resonance capacitor 9 connected in series with the heating coil 8 is short-circuited, and each switching element 4 by the first control unit 15c is short-circuited. Since the control of 5, 6 and 7 is continued, it becomes possible to allow a sufficient amount of current to flow through the heating coil 8 according to the material of the pan 11, and the pan 11 can be efficiently heated.

  In the third embodiment, the second control unit 15d performs the switching operation shown in FIG. 2 of the first embodiment. Instead, the switching operation shown in FIG. 4 of the second embodiment is performed. It may be the same as the operation, and the same effect can be expected.

It is a circuit diagram of the induction heating cooking appliance which shows Embodiment 1 of this invention. FIG. 4 is a waveform diagram showing an operation of each switching element in the first embodiment and a waveform diagram of an oscillating current flowing through this switching operation. It is a circuit diagram of the induction heating cooking appliance which shows Embodiment 2 of this invention. FIG. 6 is a waveform diagram showing an operation of each switching element in Embodiment 2 and a waveform diagram of an oscillating current flowing through this switching operation. It is a circuit diagram of the induction heating cooking appliance which shows Embodiment 3 of this invention. It is a wave form diagram which shows operation | movement when the material of a pan is iron type.

Explanation of symbols

1 commercial power source, 2 rectifier circuit, 3 smoothing capacitor, 4 first switching element,
5 Second switching element, 6 Third switching element, 7 Fourth switching element, 8 Heating coil, 9 Resonance capacitor, 10 Top plate, 11 Pan, 12 Control circuit,
13 vibration current detection resistor, 13a current detection resistor, 14 relay switch, 15 control circuit, 15a current detection unit, 15b control switching unit, 15c first control unit, 15d second control unit.

Claims (8)

A DC power supply circuit;
A heating coil and a resonant capacitor connected in series;
A first switching element inserted between a positive electrode side of the DC power supply circuit and the heating coil;
A second switching element inserted between the resonant capacitor and the negative electrode side of the DC power supply circuit;
A third switching element inserted between a positive electrode side of the DC power supply circuit and a connection point of the resonant capacitor and the second switching element;
A fourth switching element inserted between a connection point of the first switching element and the heating coil and a negative electrode side of the DC power supply circuit;
The first and second switching elements and the third and fourth switching elements are alternately switched and driven, and at the time of switching, the driving of the second and fourth switching elements is controlled. An induction heating cooker comprising a control means.   2. The induction heating cooking according to claim 1, wherein the control means drives the second and fourth switching elements at the time of switching so that the connection state of the heating coil and the resonance capacitor becomes a closed loop. vessel.   2. The control unit according to claim 1, wherein the second switching element and the fourth switching element are alternately driven at the time of switching so that the connection state of the heating coil and the resonant capacitor is intermittently closed loop. The induction heating cooker described. A DC power supply circuit;
A heating coil and a resonant capacitor connected in series;
A first switching element inserted between a positive electrode side of the DC power supply circuit and the heating coil;
A second switching element inserted between the resonant capacitor and the negative electrode side of the DC power supply circuit;
A third switching element inserted between a positive electrode side of the DC power supply circuit and a connection point of the resonant capacitor and the second switching element;
A fourth switching element inserted between a connection point of the first switching element and the heating coil and a negative electrode side of the DC power supply circuit;
Normally open switching means connected in parallel to the resonant capacitor;
Current detecting means for detecting a current flowing in the heating coil;
First control means for alternately switching and driving the first and second switching element sets and the third and fourth switching element sets;
The first and second switching elements and the third and fourth switching elements are alternately switched and driven, and at the time of switching, the driving of the second and fourth switching elements is controlled. A second control means;
Each switching element is driven by the first control means, the current flowing through the heating coil is detected through the current detection means, and it is determined whether the detected current is a predetermined value or more, and the detected current is a predetermined value or more. In this case, each switching element is driven by the second control means. When the detected current is lower than a predetermined value, the switching means is closed to short-circuit the resonant capacitor, and each switching by the first control means is performed. An induction heating cooker comprising control switching means for continuing driving of the element.   5. The induction heating cooking according to claim 4, wherein the control means drives the second and fourth switching elements at the time of switching so that the connection state of the heating coil and the resonance capacitor becomes a closed loop. vessel.   5. The control unit according to claim 4, wherein the second switching element and the fourth switching element are alternately driven at the time of switching so that the connection state of the heating coil and the resonance capacitor is intermittently closed loop. The induction heating cooker described. A DC power supply circuit;
A heating coil and a resonant capacitor connected in series;
A first switching element inserted between a positive electrode side of the DC power supply circuit and the heating coil;
A second switching element inserted between the resonant capacitor and the negative electrode side of the DC power supply circuit;
A third switching element inserted between a positive electrode side of the DC power supply circuit and a connection point of the resonant capacitor and the second switching element;
A fourth switching element inserted between a connection point of the first switching element and the heating coil and a negative electrode side of the DC power supply circuit;
The first and second switching elements and the third and fourth switching elements are alternately driven at a first frequency to charge the resonant capacitor, and the second and fourth Control means for alternately driving the switching element at a second frequency to generate an oscillating current by the heating coil and the resonant capacitor;
The induction heating cooker characterized in that the second frequency is twice or more the first frequency. The induction heating cooker according to claim 7, wherein the second frequency and the resonance frequency of the oscillating current are matched.

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