JP4494397B2 - Induction heating device - Google Patents

Description

  The present invention relates to an induction heating coil including an induction heating coil driven by at least one inverter circuit having a full-bridge configuration and an induction heating coil driven by at least one inverter circuit having a half-bridge configuration. The present invention relates to an induction heating apparatus capable of using the induction heating coil simultaneously or selectively by controlling a circuit and its control unit.

  The induction heating device converts an alternating current power source into a direct current power source using a rectifier circuit, supplies the direct current power source to an inverter circuit to convert it into a high frequency alternating current, and flows the high frequency alternating current through the heating coil to thereby generate an alternating magnetic field in the heating coil. Is generated. This alternating magnetic field generates eddy currents at the bottom of a metal cooking utensil (sometimes called a load) made of a magnetic material such as a pan placed close to the heating coil via the top plate. Cooking is performed using the heat generated by the current and the resistance of the metal cookware.

  By the way, as a first prior art of an induction heating cooking apparatus, a two-or-more induction heating apparatus using a switching element having a half-bridge configuration is provided with a driving unit that alternately conducts two switching elements. Switches the control of the above two switching elements between a method of conducting while changing the frequency at a constant conduction ratio and a method of conducting while changing the conduction ratio at a constant frequency, or using them simultaneously. A technique is disclosed that can increase the power when used alone, as compared with the case where two or more ports are used simultaneously (see, for example, Patent Document 1).

  As a second conventional technique, in a heating device using a switching element having a full bridge configuration, a control signal in which only a delay amount is changed according to a heating output is supplied to a switching element of an individual current path to be turned on / off. Discloses a technique for preventing the generation of interference sound due to the difference in frequency of the inverter circuit (see, for example, Patent Document 2).

JP-A-5-315069 (paragraph 0012, FIG. 1) JP-A-9-185986 (paragraph 0009, FIG. 1)

  In the conventional induction heating device shown in Patent Document 1, an inverter circuit that drives a plurality of heating coils as load circuits is provided for each heating port, and each inverter circuit is configured individually for each heating port with discrete components. As a result, there is a problem that it is difficult not only to increase the circuit scale and cost but also to improve noise resistance.

  The present invention has been made to solve such a problem, and aims to simplify the circuit configuration and reduce the cost, and to obtain an induction heating apparatus having a high noise resistance.

The induction heating apparatus according to the present invention includes an inverter circuit that drives a load circuit composed of a resonance capacitor corresponding to at least two heating coils, and one IPM (Intelligent) that includes three arms each having two switching elements connected in series. 2 of the 3 arms built in the IPM are used for a full-bridge inverter circuit, and the remaining 1 of the 3 arms built in the IPM is a half bridge. It is used for the inverter circuit of a structure .

  According to the present invention, since the inverter circuit for driving at least two heating coils is configured by one IPM having three sets of arms each having two switching elements connected in series, the circuit configuration can be simplified and the cost can be reduced. In addition, there is an effect that noise resistance is further improved.

Embodiment 1 FIG.
FIG. 1 is a circuit diagram showing the configuration of the induction heating apparatus according to Embodiment 1 of the present invention. In the figure, an induction heating apparatus 10 includes a heating circuit 5 (hereinafter referred to as a half-bridge) comprising a full-wave rectifier 2, a smoothing capacitor 3, a choke coil 4, and a half-bridge inverter composed of a commercial AC power source 1, a diode bridge. Bridge circuit), a heating circuit (hereinafter referred to as a full bridge circuit) 6 constituted by an inverter having a full bridge configuration, and a control circuit 7 for controlling them.
The half-bridge circuit 5 includes a heating coil 51, a resonant capacitor 52, two switching elements 53 and 54, and a snubber capacitor 55 that prevents generation of spike voltage when these switching elements are turned off. The
The full bridge circuit 6 includes a heating coil 61, a resonance capacitor 62, four switching elements 63 to 66, and two snubber capacitors 67 and 68.

Next, the operation of the first embodiment will be described with reference to FIG.
The AC voltage output from the commercial AC power supply 1 is full-wave rectified by the full-wave rectifier circuit 2 and converted to a DC voltage. In addition, the filter composed of the smoothing capacitor 3 and the choke coil 4 reduces high frequency components generated in an inverter circuit (described later) at the subsequent stage of the circuit. The direct-current rectified by the diode bridge 2 is supplied to a half-bridge inverter circuit (hereinafter referred to as a half-bridge circuit) 5 and a full-bridge inverter circuit (hereinafter referred to as a full-bridge circuit) 6. .

On the other hand, the control unit 7 provides an IPM 9 (described later) with an original signal for driving the switching elements 53 and 54 of the half bridge circuit 5 at a high frequency so that the switching elements 53 and 54 are alternately driven at a high frequency and the resonant capacitor 52. The high frequency current flows through the heating coil 51 using the charging / discharging of the above. In this case, since the inverter circuit has a half-bridge configuration, only half of the power supply voltage is applied to the heating coil 51, and the heat power that can be output is small. Further, the control unit 7 gives an IPM 9 (described later) an original signal for driving the switching elements 63, 64, 65, and 66 of the full bridge circuit 6 at a high frequency, and the pair of switching elements 63 and 66 and the pair of 64 and 65 are alternately arranged. By being driven at high frequency, a high frequency current flows through the heating coil 61. In this case, since the power supply voltage is applied to the heating coil 61 as it is because it is a full-bridge inverter circuit, the heat power that can be output is larger than that of the heating coil 51.
Therefore, the user can change the side of the heating power that can be output (hereinafter referred to as the heating power large side) with the heating coil 61 and the side of the heating power that can be output (hereinafter referred to as the heating power small side) according to the cooking mode. Since the heating coil 51 can be used properly, the cooking efficiency is improved.
Further, the control unit 7 has a load material determining means 70 for determining the material of the pan, which is a load of the induction heating device, and a table in which the material of the pan is associated with the operating conditions of the inverter circuit. The operating frequency corresponding to the material of the pan is obtained from the table according to the material of the pan determined by the means 70 and the material of the pan determined by the load material determining means 70, and the inverter circuit is controlled to be driven. . Furthermore, the control of the heating output to be put into the pan is performed by the user setting the heating output in the operation unit described later, and changing the acquired operating frequency and conduction ratio so that the set heating output is obtained. Control is performed by the control unit 7 as described above.

By the way, three sets of arms in which two switching elements are connected in series (the total number of switching elements is six) and three IPMs (Intelligent Power Modules) incorporating a drive circuit for driving these switching elements are provided. It is commercially available as a component of a phase motor control inverter. Therefore, the IPM built-in 3 as the arm composed of the switching elements 53 and 54 of the half bridge circuit 5 and the arm composed of the switching elements 63 and 64 and the arm composed of 65 and 66 of the full bridge circuit 6. A pair of arms can be diverted.
By diverting this IPM, the induction heating device of the present invention can exhibit the following excellent features specific to IPM.
(1) Since the switching elements and circuits for driving them are built in the IPM, the circuit pattern wiring is extremely short. Therefore, since the inductance component of the pattern wiring is extremely small and noise is not easily superimposed, noise resistance is very good.
(2) Both the full bridge circuit used in the heating coil on the large thermal power side and the half bridge circuit used in the heating coil on the small thermal power side can be configured by one IPM. Therefore, it is not necessary to provide a drive circuit or the like for each inverter, and the circuit configuration can be simplified.
(3) Conventionally, the switching element of the inverter circuit is composed of discrete components. However, since only one IPM is used, miniaturization and power saving can be achieved.
(4) In the configuration of the inverter circuit, in the past, the number of parts was large and the work man-hours were large. However, in the present invention, it is only necessary to use one IPM which is an inexpensive commercial product. Since there are few, it can aim at a significant cost reduction.
(5) Since the circuit components are housed in the chip, the reliability is high.

Embodiment 2. FIG.
In the second embodiment, a mode in which a half bridge circuit and a full bridge circuit configured by IPM are independently controlled by a control unit will be described.
FIG. 2 is a circuit diagram showing a configuration of the induction heating apparatus according to Embodiment 2 of the present invention. In the figure, the same reference numerals as those in FIG. The control unit 7 includes a half-bridge circuit operating frequency setting unit 71 and a full-bridge circuit operating frequency setting unit 72. The operation unit 8 includes a switch 81 for setting a thermal power on the small thermal power side and a thermal power large-side switch. A switch 82 for setting thermal power is provided, and the switch 81 on the smaller thermal power side is connected to the half-bridge circuit operating frequency setting unit 71. The switch 82 on the large thermal power side is connected to the full bridge circuit operating frequency setting unit 72.
The half-bridge circuit operating frequency setting unit 71 is provided in the IPM 9 and is connected to a drive circuit that drives the switching elements 53 and 54.
The full bridge circuit operating frequency setting unit 72 is provided in the IPM 9 and is connected to a drive circuit that drives the switching elements 63 to 66.

Next, the operation of the second embodiment will be described with reference to FIG. A description of the same parts as those in the first embodiment will be omitted, and different parts will be described.
When cooking, the user uses either or both of the switch 81 on the small heating power side and the switch 82 on the large heating power side in accordance with the type and amount of the cooking object.
When the user operates the switch 81 on the small heating power side to adjust the heating power of the heating coil 51, a control signal corresponding to the heating power is generated from the switch 81 on the small heating power side. It is sent to the circuit operating frequency setting unit 71. When the control signal corresponding to the thermal power is input from the switch 81 on the small thermal power side, the half bridge circuit operating frequency setting unit 71 generates a driving original signal corresponding to the control signal, and inputs it to the driving circuit in the IPM 9. Then, the half bridge circuit 5 is driven.
When the user operates the switch 82 on the large thermal power side, a control signal corresponding to the thermal power is generated from the switch 82 on the large thermal power side, and this signal is sent to the full bridge circuit operating frequency setting unit 72. When a control signal corresponding to the thermal power is input from the switch 82 on the large thermal power side, the full bridge circuit operating frequency setting unit 72 generates a driving original signal corresponding to the control signal and inputs it to the driving circuit in the IPM 9. Then, the full bridge circuit 6 is driven.
Here, a method of determining the operating frequency of the half-bridge circuit operating frequency setting unit 71 and the full-bridge circuit operating frequency setting unit 72 will be described. When a control signal corresponding to the heating power is input to the half-bridge circuit operating frequency setting unit 71 or the full-bridge circuit operating frequency setting unit 72, the load material determining means 70 of the control unit 7 first loads the pot that is a load before the heating power is turned on. Execute the operation to determine the material. In addition, the purpose of judging the material of the pan is that the resonance point of the load circuit consisting of the pan, the heating coil, and the resonant capacitor changes depending on the material of the pan, the size of the pan, etc. This is because it is necessary to select an appropriate operating frequency within the phase range. There are various methods of determination. For example, the inverter circuit is driven at a certain operating frequency, the current flowing in the heating coil at that time, the current flowing in the inverter circuit, and the load that the control unit 7 has The material of the pan is determined from a table that correlates the material and the operating conditions of the inverter circuit (heating coil current, inverter circuit current, etc. when operated at a certain frequency), and the operating frequency of the inverter circuit is determined.
After determining the operating frequency of the inverter circuit, for example, a conduction ratio corresponding to the thermal power is determined, and the half-bridge circuit operating frequency setting unit 71 and the full-bridge circuit operating frequency setting unit 72 generate respective driving original signals.
Similarly, when both the small thermal power switch 81 and the large thermal power switch 82 are operated, the half bridge circuit 5 is driven at the frequency set by the half bridge circuit operating frequency setting unit 71 and simultaneously the full bridge. The circuit 6 is driven at a frequency set by the full bridge circuit operating frequency setting unit 72. As a result, the half bridge circuit 5 and the full bridge circuit 6 operate at independent frequencies.

  In this way, the operating frequency of the half-bridge circuit 5 on the small thermal power side and the operating frequency of the full-bridge circuit 6 on the large thermal power side can be driven at an operating frequency suitable for the material of the pan that is the load of each inverter circuit. Is possible.

Next, the operating frequency will be described.
The human audible range is generally 20 Hz to 20 kHz, and it is necessary to remove this range.
In addition, the use frequency band of an infrared remote controller used for home appliances or the like is frequently used in the vicinity of 30 kHz to 40 kHz, and it is desirable to use it by removing such a frequency band.
Further, when the half-bridge circuit 5 and the full-bridge circuit 6 are operated at the same time, if a difference in frequency generated by both operating frequencies enters an audible range, an interference sound is generated, which needs to be prevented.
Moreover, the impedance Z of the load circuit comprised with a pan, a heating coil, and a resonance capacitor is represented by the following formula 1 when the frequency is f.
Z = (R ² + (2πfL−1 / 2πfC) ² ) ^1/2 (1)
Here, R is a resistance R of a load circuit composed of a heating coil and a resonance capacitor, L is an inductance of the heating coil, and C is a capacitance of the resonance capacitor.
As can be seen from Equation 1, since the resistance R is constant, the first term is constant, the second term increases as the frequency f increases, and the third term approaches 0 as the frequency f increases. Therefore, in the high frequency region of 20 kHz or higher, the contribution of the inductance component L to the impedance Z is considerably large. Accordingly, the lower the frequency, the smaller the impedance, and the higher the frequency, the larger the impedance.
Further, the power consumption P is expressed by the following equation 2 where the voltage is V.
^{P = V 2 / Z ........................... (} 2)
Since the thermal power is proportional to the power consumption P, the thermal power is inversely proportional to the impedance from Equation 2. Therefore, if the frequency is the same, the thermal power can be set larger as the frequency is lower, and the thermal power obtained is smaller as the frequency is higher.
Further, as described above, regarding the difference in the thermal power due to the difference in the inverter circuit system, in the case of the inverter circuit having the half bridge configuration, only half of the power supply voltage is applied to the heating coil 51, so that the thermal power that can be output is small. In the case of an inverter circuit having a full bridge configuration, since the power supply voltage is applied to the heating coil 61 as it is, the heat power that can be output is larger than that of the heating coil 51.
Considering all the above conditions, it can be seen that it is preferable to set the operating frequency of the full-bridge circuit 6 on the large thermal power side to 20 kHz to 30 kHz and the operating frequency of the half-bridge circuit 5 on the small thermal power side to 40 kHz or more.
Therefore, when the switch 82 on the large heating power side of the operation unit 8 is operated, the full bridge circuit operating frequency setting unit 72 of the control unit 7 that receives the signal from the switch 82 is the material of the pan as described above. When the operation frequency of the full bridge circuit 6 is set to a relatively low 20-30 kHz as shown in FIG. 3 and the switch 81 on the side where the heating power of the operation unit 8 is small is operated, as shown in FIG. In response to the signal from the switch 81, the half bridge circuit operating frequency setting unit 71 of the control unit 7 similarly determines the material of the pan, and then determines the operating frequency of the half bridge circuit 5 as shown in FIG. Set to a relatively high 40 kHz or higher.

As a result, the driving frequency can be set independently on the large thermal power side and the small thermal power side, and therefore, it is possible to drive at a frequency suitable for the material of the pan that is the load of each inverter circuit.
Also, the operating frequency of the full-bridge circuit on the large thermal power side is set to a relatively low 20 kHz to 30 kHz, and the operating frequency of the half-bridge circuit on the small thermal power side is set to a relatively high 40 kHz or higher. You can get a lot of firepower and enjoy a comfortable cooking.
Furthermore, since the operating frequency is set to a relatively low 20 kHz to 30 kHz on the full bridge circuit 6 side and a relatively high 40 kHz or higher on the half bridge circuit 5 side, a thermal power corresponding to the heating port can be obtained, You can enjoy comfortable cooking.
Further, when simultaneously driving the large thermal power side and the small thermal power side, for example, if the operating frequency on the large thermal power side is set to 22 kHz and the operating frequency on the small thermal power side is set to 45 kHz, the operating frequency on the large thermal power side and the small thermal power side Is 20 kHz or more outside the human audible range, so that it is possible to suppress the generation of interference sound.

Moreover, since the control part 7 is equipped with the load material determination means 70, setting an appropriate operating frequency according to the material of the pan mounted in the heating coil 61 of the large thermal power side, and the heating coil 51 of the small thermal power side. Can do. In this case, the control unit 7 stores in advance an internal storage unit (not shown) that indicates the correspondence between the material of the pan and the operating frequency on the large heating power side and the small heating power side as shown in FIG. . A control signal is generated when the user starts heating or controls heating (control of thermal power) from the switch 82 on the large thermal power side or the switch 81 on the small thermal power side of the setting unit 8. It is sent to the circuit operating frequency setting unit 72. When a control signal corresponding to the heating power is input from the switch 82 on the large heating power side, the full bridge circuit operating frequency setting unit 72 first determines the material of the pan as a load by the load material determination means 70 as described above. The operation is executed, the operating frequency corresponding to the material of the pan is determined, the driving original signal corresponding to the control signal by the user's operation of the switch 82 is generated, input to the driving circuit in the IPM 9, and the full bridge circuit 6 Drive. Similarly, when the setting switch 81 on the small heating power side of the setting unit 8 is operated, the operating frequency corresponding to the material of the pan is determined, and the driving original signal corresponding to the control signal by the user's operation of the switch 81 is determined. It is generated and input to a drive circuit in the IPM 9 to drive the half bridge circuit 6.
Thereby, cooking can be performed at an appropriate operating frequency according to the material of the pan to be used, and comfortable cooking can be enjoyed while saving power.

Embodiment 3 FIG.
In the third embodiment, a mode in which three arms with built-in IPM are used for three half-bridge circuits will be described.
FIG. 5 is a circuit diagram showing the configuration of the induction heating apparatus according to Embodiment 3 of the present invention. In the figure, the same reference numerals as those in FIG. The induction heating device 10 is a three-port induction heating device including three heating coils 51a to 51c. The inverter circuits for driving these heating coils 51a to 51c can use three arms with built-in IPM independently to form three half-bridge circuits with relatively small heating power.
The control unit 7 drives the frequencies of these three half bridge circuits independently.
As a result, it is possible to drive three heating coils with one IPM, and it is possible to reduce the size of the apparatus, simplify the circuit configuration, and improve noise resistance.

It is a circuit diagram which shows the structure of the induction heating apparatus in Embodiment 1 of this invention. It is a circuit diagram which shows the structure of the induction heating apparatus in Embodiment 2 of this invention. It is a figure which shows the operating frequency range of the thermal power large side in Embodiment 2 of this invention, and the operating frequency range of the small thermal power side. It is a table which shows a response | compatibility with the material and operating frequency of the pan in the thermal power large side in Embodiment 2 of this invention, and a thermal power small side. It is a circuit diagram which shows the structure of the induction heating apparatus in Embodiment 3 of this invention.

Explanation of symbols

  1 AC power supply, 2 full-wave rectifier, 3 smoothing capacitor, 4 choke coil, 5 half bridge circuit, 5 a to c half bridge circuit, 6 full bridge circuit, 7 control unit, 8 operation unit, 9 IPM (Intelligent Power Module) DESCRIPTION OF SYMBOLS 10 induction heating apparatus, 51 heating coil, 51a-c heating coil, 52 resonant capacitor, 52a-c resonant capacitor, 53 switching element, 54 switching element, 55 snubber capacitor, 63 switching element, 64 switching element, 65 switching element, 66 switching elements, 67 snubber capacitors, 68 snubber capacitors, 70 load material determination means, 71 half-bridge circuit operating frequency setting section, 72 full-bridge circuit operating frequency setting section, 81 thermal power side switch, 82 thermal power side switch .

Claims (7)

A top plate for placing a load such as a pan,
A plurality of heating coils disposed under the top plate for inductively heating the load;
A plurality of resonant capacitors provided for each heating coil;
A plurality of inverter circuits provided for each of the heating coils, each having a switching element for converting an AC power source into a high-frequency current, and causing the high-frequency current to flow through a load circuit including the resonance capacitor corresponding to each heating coil;
A control unit for driving and controlling the inverter,
At least two of the inverter circuits are composed of one IPM (Intelligent Power Module) having three sets of arms each having two switching elements connected in series ,
Two of the three arms built in the IPM are used in an inverter circuit having a full bridge configuration.
The remaining first arm of the three arms built in the IPM is an induction heating device according to claim Rukoto used an inverter circuit of the half-bridge arrangement. Among the plurality of load circuits, the heating coil on the side with the largest maximum thermal power that can be output is driven by the inverter circuit of the full bridge configuration,
Induction heating apparatus according to claim 1, wherein the driving the heating coil output maximum possible heating power is smaller side in the inverter circuit of the half-bridge configuration. The control unit controls the difference between an operating frequency of the inverter circuit having the full bridge configuration and an operating frequency of the inverter circuit having the half bridge configuration to be out of a range of 20 Hz to 20 kHz. The induction heating apparatus according to claim 1 or 2 . 3. The induction heating apparatus according to claim 1, wherein the control unit sets an operating frequency of the inverter circuit having the half-bridge configuration to be higher than an operating frequency of the inverter circuit having the full-bridge configuration. . Wherein the control unit, the induction heating apparatus according to any one of claims 1 to 4, characterized in that to set the operating frequency of the inverter circuit of the full bridge configuration to a range of 20KHz～30kHz. Wherein the control unit, the induction heating apparatus according to any one of claims 1 to 5, characterized in that to set the operating frequency of the inverter circuit of the half-bridge arrangement above 40 kHz. The control unit includes a load material determination unit that determines the material of the load, and a table that associates the material of the load with an operating frequency of the inverter circuit, and the load material determined by the load material determination unit induction heating apparatus according to any one of claims 1 to 6, to obtain the operating frequency corresponding from the table, and drives the inverter circuit in response to.

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