JP3399262B2 - Induction heating cooker - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating cooker having an inverter that operates at a constant frequency.

[0002]

2. Description of the Related Art Conventionally, an induction heating cooker of this type has the structure disclosed in Japanese Patent Laid-Open No. 21150/1993. Hereinafter, the induction heating cooker will be described with reference to FIGS.
This will be described with reference to FIG.

FIG. 37 is a circuit diagram of a conventional induction heating cooker. In FIG. 37, 101 is a DC power source and 102 is a DC power source.
Is an inverter circuit for converting direct current into high frequency alternating current, 10
A control circuit 3 controls the inverter circuit 102.
The inverter circuit 102 includes a reverse current blocking type first switching element 104, a reverse current conducting type second switching element 105, a heating coil 106, and a first resonance capacitor 10.
7, a second resonance capacitor 108, and a diode 109. The control circuit 103 is composed of a drive unit 110 and the like that alternately conducts the first switching element 104 and the second switching element 105 at a constant frequency f0.

FIG. 38 shows operation waveforms of respective parts for explaining the operation of the inverter circuit 102 of the conventional induction heating cooker configured as described above.

FIG. 39 shows the characteristic of the input pin with respect to the conduction ratio D1 (= ton1 / t0) of the conventional induction heating cooker. As is apparent from FIG. 39, in the conventional induction heating cooker, the ratio of the on-time (ton1) of the first switching element 104 to the constant cycle (t0) under the constant operating frequency (f0) of the inverter circuit 102. Conduction ratio D
By changing 1 (= ton1 / t0), the input power (P
in), and the first switching element 104 and the second switching element 105 were able to realize the zero volt switching operation, as is clear from the operation waveforms of the respective parts in FIG.

[0006]

Such a conventional induction heating cooker is provided with an inverter whose input can be varied at a constant operating frequency. Therefore, when it has a multi-port structure, it is caused by the frequency difference between burners. Since the problem of pan interference noise can be solved and the two switching elements can realize zero volt switching operation, it was excellent in low cost and miniaturization due to low loss and low noise in the circuit, With the spread of cooking devices, it is necessary to establish a new low-cost, small-sized inverter and its control system.

In view of the above points, the present invention has an object to provide an induction heating cooker using an inverter system which is lower in cost and smaller in size than a conventional one and which operates at a constant frequency.

[0008]

To solve the above problems, the present invention provides a DC power supply, a heating coil connected to one end of the DC power supply, the other end of the heating coil and the other end of the DC power supply. A first switching element connected to, a first resonant capacitor forming a resonant circuit with the heating coil,
An inverter circuit configured by a series circuit of a reverse current conducting type second switching element and a second resonance capacitor connected in parallel with the heating coil or the first resonance capacitor, and an input current for detecting an input current of the inverter circuit A detection means and a drive control circuit for alternately conducting the switching elements at a constant frequency, wherein the drive control circuit controls the conduction ratio of the switching elements based on the output of the input current detection means , and , Both switching elements
Inverter circuit input set according to the conduction time of the child
The conduction ratio is controlled within the range of current .

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 includes a heating coil connected to one end of a DC power supply, a first switching element connected to the other end of the heating coil and the other end of the DC power supply, A first resonance capacitor forming a resonance circuit with the heating coil, an inverter circuit composed of a series circuit of a reverse current conduction type second switching element and a second resonance capacitor connected in series or in parallel with the heating coil,
Input current detection means for detecting an input current of the inverter circuit, conduction time detection means for detecting conduction time of the first switching element or the second switching element, first switching element of the inverter circuit, and A drive control circuit for driving and controlling two switching elements, wherein the drive control circuit alternately conducts the first switching element and the second switching element at a constant frequency, and an input detected by the input current detecting means. Current, the conduction time of the first switching element detected by the conduction time detection means, or for changing the conduction ratio in a range of a predetermined value or less determined for each conduction time of the second switching element. is there.

According to a second aspect of the present invention, a DC power supply, a heating coil connected to one end of the DC power supply, a first switching element connected to the other end of the heating coil and the other end of the DC power supply. A first resonance capacitor forming a resonance circuit with the heating coil; an inverter circuit including a series circuit of a reverse current conduction type second switching element and a second resonance capacitor connected in series or in parallel with the heating coil; A first switching element voltage detecting means for detecting a voltage of the first switching element, a second switching element voltage detecting means for detecting a voltage of the second switching element, a first switching element of the inverter circuit and a second A drive control circuit for driving and controlling the switching element is provided, wherein the drive control circuit includes the first switching element and the second switch. The switching elements are alternately conducted at a constant frequency, and the voltage of the first switching element detected by the first switching element voltage detection means is the second switching element detected by the second switching element voltage detection means. The conduction ratio is changed within a range below a predetermined value determined for each voltage.

According to a third aspect of the present invention, there is provided a DC power supply, a heating coil connected to one end of the DC power supply, a first switching element connected to the other end of the heating coil and the other end of the DC power supply. A first resonance capacitor forming a resonance circuit with the heating coil; an inverter circuit including a series circuit of a reverse current conduction type second switching element and a second resonance capacitor connected in series or in parallel with the heating coil; From the output of the first switching element voltage detection means for detecting the voltage of the first switching element, the second switching element voltage detection means for detecting the voltage of the second switching element, and the output of the first switching element voltage detection means Subtraction means for subtracting the output of the second switching element voltage detection means, the first switching element of the inverter circuit and the second A driving control circuit for driving and controlling an switching element, wherein the driving control circuit alternately conducts the first switching element and the second switching element at a constant frequency, and the first switching detected by the subtraction means The conduction ratio is changed within a range in which the voltage difference between the voltage of the element and the voltage of the second switching element is a predetermined value or less.

According to a fourth aspect of the present invention , a DC power supply, a heating coil connected to one end of the DC power supply, a first switching element connected to the other end of the heating coil and the other end of the DC power supply. A first resonance capacitor forming a resonance circuit with the heating coil; an inverter circuit including a series circuit of a reverse current conduction type second switching element and a second resonance capacitor connected in series or in parallel with the heating coil; A second switching element current detecting means for detecting a current of the second switching element, a conduction time detecting means for detecting a conduction time of the first switching element or the second switching element, and a second of the inverter circuit. A drive control circuit for driving and controlling the one switching element and the second switching element, wherein the drive control circuit is
The first switching element and the second switching element are alternately conducted at a constant frequency, and the current of the second switching element detected by the second switching element current detection means is detected by the conduction time detection means. The conduction ratio of the first switching element is changed within a conduction time of the first switching element or a predetermined value or less determined for each conduction time of the second switching element.

[0013]

EXAMPLES ( Reference Example 1) FIG. 1 shows a circuit configuration diagram of an induction heating cooker according to a first reference example of the present invention. In FIG. 1, 1 is a DC power source and 2 is a DC power source 1. It is an inverter circuit to be connected. The inverter circuit 2 has a heating coil 4 whose one end is connected to the positive side which is one end of the DC power supply 1, and a first switching which is connected to the other end of the heating coil 4 and the negative side which is the other end of the DC power supply 1. IGBT5 with reverse conduction diode built-in
And the IGBT 5 so as to form a resonance circuit with the heating coil 4.
The first resonance capacitor 6 connected in parallel with the heating coil 4 and the series circuit of the second resonance capacitor 8 and the IGBT 7 having a built-in reverse conducting diode which is the second switching element connected in parallel.

A current transformer 9 is connected between the DC power supply 1 and the inverter circuit 2, a secondary side of the current transformer 9 is connected to an iin detection circuit 10, and an output of the iin detection circuit 10 is connected to a drive control circuit 3. The drive control circuit 3 is connected to the gate terminal of the IGBT 5 and the gate terminal of the IGBT 7, respectively. The input current detecting means for detecting the input current of the inverter circuit 2 is composed of the current transformer 9 and i.
It is composed of an in detection circuit 10.

The operation of the induction heating cooker configured as described above will be described.

FIG. 2 is an operation waveform of each part of the inverter circuit 2. In FIG. 2, vge1 is a gate-emitter voltage of the IGBT5, vge2 is a gate-emitter voltage of the IGBT7, and vce1 is a collector-emitter voltage of the IGBT5. Voltage, vce2 is the collector-emitter voltage of the IGBT7, ic1 is the collector current of the IGBT5, and ic2 is I
The collector current of GBT7, iC1 is the current of the first resonance capacitor 6, vC2 is the voltage of the second resonance capacitor 8, and iL
Indicates the current of the heating coil 4, respectively.

Further, t0 is the operation cycle of the inverter circuit 2, ton1 is the conduction time of the IGBT5, and ton2 is the IG.
The conduction time of BT7, td1 and td2 are IGBT5 and IG
The BT7 is a non-conducting time, that is, a dead time, and the operating cycle t0 of the inverter circuit 2 is always constant.

FIG. 3 is a diagram showing the basic characteristics of the inverter circuit 2, showing the characteristics of the conduction ratio D1 = ton1 / t0, which is the ratio of the conduction time ton1 of the IGBT 5 to the constant operation period t0, and the input power pin. As shown in FIG. 3, the input power pin of the inverter circuit 2 can be changed by the conduction ratio D1.

When the induction heating cooker operates, the input current detecting means composed of the current transformer 9 and the iin detecting circuit 10 detects the input current iin of the inverter circuit 2, and the iin detecting circuit 10 detects the input current iin. Output according to size. The drive control circuit 3 detects the input current iin from the output of the iin detection circuit 10, sets the conduction ratio D1 based on the detection result, and sets the IGBT5 and the IGBT.
Drive 7

The input power pin is the voltage of the DC power supply 1 E
Then, since (Equation 1) is obtained, the input power pin can be known by detecting the input current iin of the inverter circuit 2.

[0021]

[Equation 1]

In this way, the drive control circuit 3 has the IGBT 5 and the IGBT 7 under the constant operating frequency f0 (= 1 / t0).
Are alternately conducted, the constant frequency operation of the inverter circuit 2 can be realized.

Further, the drive control circuit 3 can change the input power pin by changing the conduction ratio D1, and iin
Since the input power pin can be detected from the output of the detection circuit 10, the input current ii of the inverter circuit 2 is controlled by controlling the conduction ratio D1 based on the output of the iin detection circuit 10.
Feedback control by n can be performed, and the input power pin can be accurately controlled to an arbitrary value.

Reference Example 2 FIG. 4 is a circuit configuration diagram of an induction heating cooker according to a second reference example of the present invention. In FIG. 4, 11 is a commercial power source, and 12 is a commercial power source.
Is a diode bridge that rectifies the commercial power supply 11. A smoothing capacitor 13 is connected to the output of the diode bridge 12, and the smoothing capacitor 13 functions as a DC power supply supplied to the inverter circuit 2.

The inverter circuit 2 has the same structure as the inverter circuit 2 of the induction heating cooker of the reference example 1. A current transformer 14 is connected between the commercial power supply 11 and the diode bridge 12, and the secondary side of the current transformer 14 is connected to the iin detection circuit 15. The output vout1 of the iin detection circuit 15 and the output vo of the input setting means 16
ut2 is connected to the comparison means 17, the output of the comparison means 17 is connected to the drive control circuit 18, and the drive control circuit 18 is I
It is connected to the GBT 5 and the IGBT 7, respectively.

[0026] For more induction heating cooker constructed as, its operation will be described with reference to FIGS.

An arbitrary input power p by the input setting means 16
If in is set, the induction cooker will start operating,
The input setting means 16 outputs a predetermined voltage determined in advance according to the set input power pin vout2.
Output as. The input current detection means composed of the current transformer 14 and the iin detection circuit 15 is the commercial power supply 11
Detects the input current iin to the induction cooking device and outputs a voltage corresponding to the magnitude of the input current iin as vout1. The comparison means 17 has an output voltage vout1 of the iin detection circuit 15 and an output voltage vout2 of the input setting means 16.
And outputs a voltage according to the difference between these output voltages. The drive control circuit 18 sets the conduction ratio D1 based on the magnitude of the difference between the input set by the input setting means 16 detected by the output of the comparison means 17 and the input detected by the input current detection means, and IGBT5 and IGBT with conduction ratio D1
Drive T7.

Input power pin and iin of the induction heating cooker
The characteristic of the output voltage vout1 of the detection circuit 15 is as shown in FIG. 5, so that pin can be known from vout1. For example, when the input setting means 16 has the five-stage setting specification as shown in FIG. If the value of the output voltage vout2 of the input setting means 16 for each setting is determined in advance as shown in FIG. 7, feed bag control by iin can be performed for each set input power, and according to the product specifications. It is possible to accurately obtain an arbitrary input power pin.

(Embodiment 1 ) FIG. 8 shows a circuit configuration diagram of an induction heating cooker according to a first embodiment of the present invention. In FIG. 8, a DC power source 1, an inverter circuit 2, a current transformer 9, iin detection circuit 10 is actually
This is the same as that of the first embodiment .

The conduction time detecting means for detecting the output of the iin detection circuit 10 and the on time ton1 of the IGBT 5 is t.
The output of the on1 detection circuit 19 is connected to the drive control circuit 20.

[0031] For more induction heating cooker constructed as will be explained.

The drive control circuit 20 uses the current transformer 9
The conduction ratio D1 is set on the basis of the output of the input current detecting means constituted by the iin detection circuit 10 and the conduction ratio D.
The feedback control of the input pin by the input current iin that the IGBT 5 and the IGBT 7 are driven by 1 is the same as the reference example 1 .

The ton1 detection circuit 19 detects the on-time ton1 of the IGBT 5 and outputs an output according to the length of the ton1. The drive control circuit 20 receives the input current i as described above.
The input pin is feedback controlled by in,
At that time, the IGB detected by the ton1 detection circuit 19
The inverter circuit 2 is controlled within a range that does not exceed the preset value of the input current iin of the inverter circuit 2 that is predetermined for each value of the on-time ton1 of T5. That is,
As shown by the thick line in FIG. 9, the set value of pin determined in advance for each value of ton1 is pin = 2000 W when ton1 ≧ 17 μs, and pin = 1 when ton1 <17 μs.
In the case of 600 W, when the induction-heated load is a non-magnetic pot, the pin is controlled in the range of 1600 W or less, and in the case of the magnetic pot, the pin is controlled in the range of 2000 W or less.

The loss of each component constituting the inverter circuit 2 is larger in the non-magnetic pot than in the magnetic pot when compared with the same pin, but as shown by the thick line in FIG.
Since the limiter of the input pin set for each conduction time ton1 of T5 is provided, the maximum value of the input pin of the magnetic pot is 2000W, but the maximum value of the input pin of the non-magnetic pot is limited to 1600W. The load becomes a magnetic pot.
Despite being a non-magnetic pot, the heating operation can be performed without excessively increasing the loss of each component of the inverter circuit 2.

The predetermined value of the input pin determined for each value of the conduction time ton1 of the IGBT 5 may be as shown in FIG. 10 or other values. In the case shown in FIG. 10, the loss of the components of the inverter circuit 2 is larger than that in the case of FIG. 9 due to the load A having the ton1-pin characteristic of the load between the non-magnetic pot and the magnetic pot. And input pi
It is possible to perform heating at an optimum operating point considering both maximum values of n.

Reference Example 3 FIG. 11 is a circuit configuration diagram of an induction heating cooker of Reference Example 3 of the present invention.

In FIG. 11, the DC power supply 1 and the inverter circuit 2 are the same as in the reference example 1 . The vce1 detection circuit 21 is connected to the collector of the IGBT5, the output of the vce1 detection circuit 21 is connected to the drive control circuit 22, and the drive control circuit 22 is connected to the gate terminals of the IGBT5 and the IGBT7, respectively.

The operation of the induction heating cooker configured as above will be described. When the induction heating cooker operates, the vce1 detection circuit 21 detects the collector-emitter voltage vce1 of the IGBT 5 and outputs a voltage according to the magnitude of vce1. The drive control circuit 22 uses vce1
Based on the magnitude of the output voltage of the detection circuit 21, the conduction ratio D
1, that is, the respective conduction times ton1 and ton2 of the IGBT5 and the IGBT7 are set, and the IGBT5 and the IGBBT7 are driven by those conduction times.

Input power pin of induction heating cooker and IGB
The characteristic of the collector-emitter voltage vce1 of T5 is as shown in FIG. 12, and the vce1 detection circuit 21 can indirectly detect the input pin by detecting vce1 during operation, and the drive control circuit 22 can detect the input vce1. IGBT5 and IGBT based on the magnitude of vce1 detected by the detection circuit
Since the conduction ratio of T7 is changed, the pin by vce1
Feedback control can be performed, and the input power pin can be accurately controlled to an arbitrary value.

Reference Example 4 FIG. 13 is a circuit diagram of the induction heating cooker of Reference Example 4 .

In FIG. 13, the DC power supply 1, the inverter circuit 2, the current transformer 9, and the iin detection circuit 10 are
This is the same as that of the reference example 1, and the vce1 detection circuit 21
Is the same as in Reference Example 3 .

The outputs of the vce1 detection circuit 21 and the iin detection circuit 10 are both connected to the drive control circuit 23.

The operation of the induction heating cooker configured as described above will be described.

Current transformer 9 and iin detection circuit 10
The input current detection means configured by detects the input current iin of the inverter circuit 2, and the iin detection circuit 10
A voltage corresponding to the size of iin is output. Also, vce
The 1 detection circuit 21 detects the collector-emitter voltage vce1 of the IGBT 5 and outputs a voltage according to the magnitude of vce1. The drive control circuit 23 uses the iin detection circuit 10
The IGBT5 and the IGBT7 are driven based on the magnitudes of both the output voltage of VCE1 and the output voltage of the vce1 detection circuit 21.
That is, vc detected by the vce1 detection circuit 21
When e1 is less than 700V, the drive control circuit 23 determines that ii
The inverter circuit 2 is controlled based on the output of the n detection circuit 10. That is, the feedback control of pin by iin is performed. v detected by the vce1 detection circuit 21
When ce1 is 700V, the drive control circuit 23 outputs vce
The inverter circuit 2 is controlled based on the output of the 1 detection circuit 21. That is, when the vce1 detected by the vce1 detection circuit 23 becomes 700 V, the drive control circuit 23 outputs vc
The conduction ratio D1 is limited so that e1 does not exceed 700V.

As shown in the characteristics of the input pin and the collector-emitter voltage vce1 of the IGBT 5 in FIG. 14, the standard pot and the non-magnetic pot can input up to 2000 W which is the rated input, and the pot and the magnetic pot have vce1 = 700 V. The input can be obtained up to the value, but the collector-emitter voltage vce1 of the IGBT5 is 7 for any load.
The voltage does not exceed 00V, and the inverter circuit 2 can secure a safe operating state.

Reference Example 5 FIG. 15 is a circuit diagram of the induction heating cooker of Reference Example 5 .

In FIG. 15, the DC power supply 1 and the inverter circuit 2 are the same as in the reference example 1.

The vce2 detection circuit 24 is connected to the collector of the IGBT 7, and the output of the vce2 detection circuit 24 is
The drive control circuit 25 is connected to the drive control circuit 25.
It is connected to the gates of the GBT 5 and the IGBT 7, respectively.

The operation of the induction heating cooker constructed as above will be described.

When the induction heating cooker operates, the vce2 detection circuit 24 detects the collector-emitter voltage vce2 of the IGBT 7 and outputs a voltage according to the magnitude of vce2. The drive control circuit 25 sets the conduction times ton1 and ton2 of the IGBT5 and the IGBT7 based on the magnitude of the output voltage of the vce2 detection circuit 24, and the conduction time t.
The IGBT5 and IGBBT7 are driven by on1 and ton2, respectively.

Input power pin of induction heating cooker and IGB
The characteristics of the collector-emitter voltage vce2 of T7 are as shown in FIG. 16, and the drive control circuit 25 outputs vc
The input pin can be indirectly detected from the size of vce2 detected by the e2 detection circuit 24, and
n feedback control is possible and the induction heating cooker pi
n control can be performed accurately.

(Embodiment 2 ) FIG. 17 is a circuit configuration diagram of an induction heating cooker according to a second embodiment of the present invention.

[0053] In FIG. 17, the DC power source 1 and the inverter circuit 2 is the same as in Reference Example 1, VCE1 detection circuit 21 ginseng
Same as that of Consideration 3 , but the vce2 detection circuit 24 is a reference example.
It is the same as that of 5 .

The collector of the IGBT 5 is connected to the vce1 detection circuit 21, and the collector of the IGBT 7 is connected to vc.
The e2 detection circuit 24 is connected, and the output of the vce1 detection circuit 21 and the output of the vce2 detection circuit 24 are both connected to the drive control circuit 26. The drive control circuit 26 connects the IGBT 5 and I
Each is connected to the gate of the GBT 7.

The operation of the induction heating cooker configured as above will be described.

The vce1 detection circuit 21 detects the collector-emitter voltage vce1 of the IGBT 5 and outputs a voltage corresponding to the magnitude of vce1. In addition, the vce2 detection circuit 24 detects the collector-emitter voltage vc of the IGBT 7.
e2 is detected and a voltage corresponding to the magnitude of vce2 is output. The drive control circuit 26 inputs the output of the vce1 detection circuit 21 and the output of the vce2 detection circuit 24, sets respective conduction times ton1 and ton2 of the IGBT5 and the IGBT7 based on these two outputs, and the conduction time ton.
1 and ton2 drive the IGBT5 and IGBBT7, respectively. That is, as shown in FIG. 18, the vce2-vce1 characteristic of each load to be induction-heated is controlled so as to be restricted by the bold line in the figure. Therefore, the magnetic pan and the non-magnetic pan t0.5 are not limited by this control, but the non-magnetic pan t1, the non-magnetic pan t1.5, and the aluminum pan have the values shown in the thick line in FIG. There will be restrictions.

With the control as described above, the drive control circuit 26
Can operate without limiting the pin for the magnetic pan with relatively small loss of the components of the inverter circuit 2 and the non-magnetic pan t0.5 with a pan bottom thickness of 0.5 mm,
For aluminum pan / non-magnetic pan t1.5 / non-magnetic pan t1 in which the loss of the components of the inverter circuit 2 is relatively large,
p according to the value of vce1 determined for each value of ce2
It is possible to limit the in, and the loss of the components of the inverter circuit 2 becomes relatively large.
Also for the non-magnetic pan t1, the loss of parts can be suppressed.

( Embodiment 3 ) FIG. 19 is a circuit diagram of an induction heating cooker according to a third embodiment of the present invention .

In FIG. 19, the DC power supply 1 and the inverter circuit 2 are the same as those in the reference example 1, and the vce1 detection circuit 21 and the vce2 detection circuit 24 are the same as those in the second embodiment. The outputs of the vce1 detection circuit 21 and the vce2 detection circuit 24 are both connected to the subtraction circuit 27, and the output of the subtraction circuit 27 is connected to the drive control circuit 28.

The operation of the induction heating cooker configured as described above will be described.

The vce1 detection circuit 21 detects the collector-emitter voltage vce1 of the IGBT 5 and outputs a voltage corresponding to the magnitude of vce1. In addition, the vce2 detection circuit 24 detects the collector-emitter voltage vc of the IGBT 7.
e2 is detected and a voltage corresponding to the magnitude of vce2 is output. The subtraction circuit 27 outputs the output of the vce1 detection circuit 21 and v
A value according to the magnitude of the difference between the outputs of the ce2 detection circuit 24 is output, and the drive control circuit 28 drives and controls the IGBT 5 and the IGBT 7 based on the output of the subtraction circuit 27.
That is, the pin- (vce of each load as shown in FIG.
The 1-vce2) characteristic can be controlled so as to be restricted as shown by the thick line in the figure. When compared with the same pin, (vce1-vce2) is larger in the non-magnetic pot than in the magnetic pot, and the thicker the bottom of the non-magnetic pot is, the larger the loss of the inverter circuit 2 is. The pan is larger, and the thicker the non-magnetic pan is, the thicker the pan is. Therefore, by limiting (vce1-vce2) to 110V, the non-magnetic pan t1.2 and the non-magnetic pan t1.5 have The pin can be suppressed, and as a result, the loss of each component of the inverter circuit 2 can be suppressed.

Reference Example 6 FIG. 21 is a circuit configuration diagram of the induction heating cooker of the present reference example .

In FIG. 21, the DC power supply 1 and the inverter circuit 2 are the same as those in the reference example 1.

The current transformer 29 is connected in series with the heating coil 4, and the secondary side of the current transformer 29 is i
The L control circuit 31 is connected to the L detection circuit 30, and the output of the iL detection circuit 30 is connected to the drive control circuit 31.
It is connected to the gates of the GBT 5 and the IGBT 7, respectively.

The operation of the induction heating cooker configured as described above will be described.

Current transformer 29 and iL detection circuit 30
The heating coil current detection unit configured by detects the current of the heating coil 4, and the iL detection circuit 30 outputs a voltage according to the magnitude of the current of the heating coil 4. The drive control circuit 31 determines the conduction times ton1 and to of the IGBT5 and the IGBT7 based on the magnitude of the output voltage of the iL detection circuit 30.
n2 is set, and IGBT5 and IGBBT are set depending on the conduction time.
7 are driven respectively.

Input pin and heating coil 4 in the standard pan
22 has a characteristic as shown in FIG. 22, the drive control circuit 31 can indirectly detect the input pin by the magnitude of iL detected by the current transformer 29 and the iL detection circuit 30, and Based on the size of
The feedback control of the pin by iL can be performed by changing the conduction ratio of 5 and the IGBT 7, and the pin control of the induction heating cooker can be accurately performed.

Since the drive control circuit 31 can detect the size of iL from the output of the iL detection circuit 30, FIG.
As shown by the thick line in Fig. 23, the limiter can be controlled at iL = 70 (A). In the case of Fig. 23, the input p of the non-magnetic pan is
The in can be suppressed to 1600 W, and the loss of the inverter circuit 2 can be suppressed.

Reference Example 7 FIG. 24 is a circuit configuration diagram of an induction heating cooker of the present reference example .

In FIG. 24, the DC power supply 1 and the inverter circuit 2 are the same as those in the reference example 1.

The current transformer 32 is connected in series with the IGBT 5, and the secondary side of the current transformer 32 is ic.
1 detection circuit 33, the output of the ic1 detection circuit 33 is connected to the drive control circuit 34, the drive control circuit 34
Are connected to the gates of the IGBT 5 and the IGBT 7, respectively.

The operation of the induction heating cooker configured as described above will be described.

Current transformer 32 and ic1 detection circuit 3
The first switching element current detection means composed of 3 detects the collector current ic1 of the IGBT5, and ic1
The detection circuit 33 outputs a voltage according to the magnitude of ic1. The drive control circuit 34 sets the conduction times ton1 and ton2 of the IGBT5 and the IGBT7 based on the magnitude of the output voltage of the ic1 detection circuit 33, and the IGBT is determined by the conduction time.
Inverter circuit 2 drives T5 and IGBT7 respectively.
To operate.

Input power pin at standard load and IGB
Since the characteristic of the collector current ic1 of T5 is as shown in FIG. 25, the drive control circuit 34 can indirectly detect the input pin from the magnitudes of ic1 detected by the current transformer 32 and the ic1 detection circuit 33. The feedback control of the pin by ic1 can be performed, and the pin control of the induction heating cooker can be accurately performed.

Further, since the drive control circuit 34 can detect the size of ic1 from the output of the ic1 detection circuit 33, the limiter can be controlled by ic1 = 70 (A) as shown by the thick line in FIG. In the case of 26, the input pin of the non-magnetic pot can be suppressed to 1600 W, and the loss of the inverter circuit 2 can be suppressed. Compared with the case of detecting the iL as in Reference Example 6, and detects the present embodiment the iL1 smaller ic1, in the present reference example, it is possible to use a small current transformer ratings.

Reference Example 8 FIG. 27 is a circuit diagram of the induction heating cooker of the present reference example .

In FIG. 27, the DC power supply 1 and the inverter circuit 2 are the same as those in the reference example 1 . The current transformer 35 is connected in series with the IGBT 7, the secondary side of the current transformer 35 is connected to the ic2 detection circuit 36, the output of the ic2 detection circuit 36 is connected to the drive control circuit 37, and the drive control circuit 37 is IGBT5 and IGBT7
Connected to each gate.

The operation of the induction heating cooker configured as described above will be described.

Current transformer 35 and ic2 detection circuit 3
The second switching element current detection means composed of 6 detects the collector current ic2 of the IGBT 7,
The detection circuit 36 outputs a voltage according to the magnitude of ic2. The drive control circuit 37 sets the conduction times ton1 and ton2 of the IGBT5 and the IGBT7 based on the magnitude of the output voltage of the ic2 detection circuit 36, and the IGBT is determined by the conduction time.
The inverter circuit 2 is operated by driving T5 and IGBBT7, respectively.

Input power pin and IGBT in standard pan
The characteristic of the current ic2 of No. 7 is as shown in FIG. 28, and the drive control circuit 37 indirectly inputs p from the magnitude of ic2 detected by the current transformer 35 and the ic2 detection circuit 36.
Since in can be detected, the feedback control of the pin by ic2 can be performed, and the pin control of the induction heating cooker can be accurately performed.

Further, since the drive control circuit 37 can detect the size of ic2 from the output of the ic2 detection circuit 36, it is possible to perform a control to apply a limiter at ic2 = 40 (A) as shown by the thick line in FIG. In the case of 29, the input pin of the non-magnetic pan can be suppressed to 1600 W, and the loss of the inverter circuit 2 can be suppressed. Compared with the case of detecting ic1 as in Reference Example 7 , ic1 is detected in this embodiment.
Since a smaller ic2 is detected, a current transformer having a smaller rating can be used in this embodiment.

( Fourth Embodiment) FIG. 30 is a circuit diagram of an induction heating cooker according to a fourth embodiment of the present invention.

In FIG. 30, the DC power supply 1 and the inverter circuit 2 are the same as those in the reference example 1, the ton1 detection circuit 19 is the same as that in the first embodiment, and the current transformer 3 is the same.
The second switching element current detection means composed of 5 and the ic2 detection circuit 36 is the same as in the reference example 8 .

The output of the ic2 detection circuit 36 and the output of the ton1 detection circuit 19 are both connected to the drive control circuit 38, and the drive control circuit 38 is connected to the gates of the IGBT5 and the IGBT7, respectively.

The operation of the induction heating cooker configured as described above will be described.

Current transformer 35 and ic2 detection circuit 3
The second switching element current detection means composed of 6 detects the collector current ic2 of the IGBT 7,
The detection circuit 36 outputs a voltage according to the magnitude of ic2. The ton1 detection circuit 19 determines the ON time t of the IGBT5.
on1 is detected, and an output according to the length of ton1 is output.
The drive control circuit 38 operates the inverter circuit 2 with the conduction ratio of the IGBT 5 and the IGBT 7 determined based on the magnitude of the output voltage of the ic2 detection circuit 36, but the magnitude of ic2 detected by the ic2 detection circuit 36 is , Ton1 detection circuit 19 controls conduction ratio D1 so as not to exceed a value determined for each ton1.

That is, as described in the reference example 8 , since the drive control circuit 38 can detect ic2 by the current transformer 35 and the ic2 detection circuit 36, a limiter by ic2 can be provided, but at the same time, the ton1 detection circuit 19 can be provided. since it by the output ton1 also detected, the limiter value ic2 can be freely set for each value of ton1, for example, if you like the thick line in FIG. 31, as compared with the case of FIG. 29 of the reference example 8, the multilayer pan Although the input pin is limited to 1800 W, it becomes possible to input up to 2000 W in this embodiment.

Regarding the configuration of the inverter circuit 2 in the above-mentioned first to fourth embodiments, the first resonance capacitor 6 may be connected in parallel with the heating coil 4 as shown in FIG.
Further, as shown in FIG. 33, the same operation can be performed by connecting both the heating coil 4 and the IGBT 5 in parallel.

Further, the DC power source 1, the heating coil 4 and the IGB
The connection of T5 may be a configuration in which the IGBT 5 is connected to the positive side of the DC power supply 1 and the heating coil 4 is connected to the negative side of the DC power supply 1 as shown in FIG.

In addition, the IGBT 7 and the second resonance capacitor 8
The series circuit may be connected in parallel with the IGBT 5 as shown in FIG.

Further, the first switching element can be also implemented in the reverse current blocking type as shown in FIG.

[0092]

As described above, according to the first aspect of the invention, the inverter circuit having a simpler structure than the conventional one is used.
Since constant frequency operation and zero volt switching operation of the first switching element and the second switching element can be realized, the occurrence of pan interference noise can be eliminated and the loss and noise of the inverter circuit can be reduced even when used in a multi-port induction heating cooker. Therefore, the size and cost of the product can be reduced. Further, since the drive control circuit can feedback-control the inverter circuit based on the input current detected by the input current detecting means, the input power control of the induction heating cooker can be accurately performed regardless of the type of load.

Then , the input current detection means detects the input current, the conduction time detection means of the switching element detects the conduction time, and the drive control circuit specifies the load from the (input current-conduction time) characteristic and Since the current is limited to the predetermined value that is determined for each conduction time, the input can be limited only to the non-magnetic pot, and safe operation can be performed without excessive loss of the inverter circuit even when the load is non-magnetic pot. can get.

According to the second aspect of the invention, the drive control circuit can feedback-control the inverter circuit based on the magnitude of the first switching element voltage detected by the first switching element voltage detecting means. The input power of the induction heating cooker can be controlled accurately.

Then, the first switching element voltage detecting means detects the first switching element voltage, the second switching element voltage detecting means detects the second switching element voltage, and the drive control circuit (the first switching element voltage -The second switching element voltage) is used to specify the load based on the difference in the characteristics, and the first switching element voltage is limited to the specified value determined for each second switching element voltage. The input can be limited only to a load that causes a large loss during operation, and safe operation can be obtained under any load without excessive loss of the inverter circuit.

According to the third aspect of the present invention, the first switching element voltage detecting means detects the first switching element voltage, the second switching element voltage detecting means detects the second switching element voltage, and the subtraction is performed. The means subtracts the second switching element voltage from the first switching element voltage, and the drive control circuit determines the value of the first switching element voltage minus the second switching element voltage and the difference in the thickness of the pan bottom due to the difference in the characteristics of the input. Since a load that causes a large loss during operation of an inverter circuit represented by a large non-magnetic pot is specified, and the value obtained by subtracting the second switching element voltage from the first switching element voltage is limited to a predetermined value,
Safe operation can be obtained without increasing the loss of the inverter circuit even for non-magnetic pans with large pan bottoms.

Further, according to the invention described in claim 4 , the second switching element current detection means detects the second switching element current, the conduction time detection means of the switching element detects the conduction time, and the drive control circuit is , Since the load is distinguished by the difference between the characteristics of the second switching element current and the conduction time depending on the load and the second switching element current is limited to the predetermined value determined for each conduction time, Safe and efficient heating operation can be obtained for each load by limiting the input and without limiting the input for the multi-layer pan.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of an induction heating cooker according to a first reference example of the present invention.

FIG. 2 is an operation waveform diagram of each part of the inverter circuit of the induction heating cooker.

FIG. 3 is a characteristic diagram of the conduction ratio and the input power of the induction heating cooker.

FIG. 4 is a circuit configuration diagram of an induction heating cooker according to a second reference example of the present invention.

FIG. 5 is a characteristic diagram of input power and vout1 of the induction heating cooker.

FIG. 6 is an explanatory view of specifications of input setting means of the induction heating cooker.

FIG. 7 is a characteristic diagram of the set input level of the input setting means of the induction heating cooker and vout2.

FIG. 8 is a circuit configuration diagram of the induction heating cooker according to the first embodiment of the present invention.

FIG. 9 is a characteristic diagram of on-time and input power of the first switching element of the induction heating cooker.

FIG. 10 is another characteristic diagram of on-time and input power of the first switching element of the induction heating cooker.

FIG. 11 is a circuit configuration diagram of an induction heating cooker according to a reference example 3 of the present invention.

FIG. 12 is a characteristic diagram of input power of the induction heating cooker and vce1 of the first switching element.

FIG. 13 is a circuit configuration diagram of an induction heating cooker according to reference example 4 of the present invention.

FIG. 14 is a characteristic diagram of input power of the induction heating cooker and vce1 of the first switching element.

FIG. 15 is a circuit configuration diagram of an induction heating cooker according to reference example 5 of the present invention.

FIG. 16 is a characteristic diagram of input power of the induction heating cooker and vce2 of the second switching element.

FIG. 17 is a circuit configuration diagram of an induction heating cooker according to a second embodiment of the present invention.

FIG. 18 is a characteristic diagram of vce2 of the second switching element and vce1 of the first switching element of the induction heating cooker.

FIG. 19 is a circuit configuration diagram of an induction heating cooker according to a third embodiment of the present invention.

FIG. 20: Input power of the induction heating cooker and (vce1-
vce2) characteristic diagram

FIG. 21 is a circuit configuration diagram of an induction heating cooker according to reference example 6 of the present invention.

FIG. 22 is a characteristic diagram of the input power and the heating coil current of the induction heating cooker.

FIG. 23 is another characteristic diagram of the input power and the heating coil current of the induction heating cooker.

FIG. 24 is a circuit configuration diagram of an induction heating cooker according to reference example 7 of the present invention.

FIG. 25 is a characteristic diagram of input power and first switching element current of the induction heating cooker.

FIG. 26 is another characteristic diagram of the input power and the first switching element current of the induction heating cooker.

FIG. 27 is a circuit configuration diagram of an induction heating cooker according to Reference Example 8 of the present invention.

FIG. 28 is a characteristic diagram of the input power and the second switching element current of the induction heating cooker.

FIG. 29 is another characteristic diagram of the input power and the second switching element current of the induction heating cooker.

FIG. 30 is a circuit configuration diagram of an induction heating cooker according to a fourth embodiment of the present invention.

FIG. 31 is a characteristic diagram of the conduction time of the first switching element and the second switching element current of the induction heating cooker.

FIG. 32 is a circuit configuration diagram of an induction heating cooker according to another embodiment of the present invention.

FIG. 33 is another circuit configuration diagram of the induction heating cooker.

FIG. 34 is another circuit configuration diagram of the induction heating cooker.

FIG. 35 is another circuit configuration diagram of the induction heating cooker.

FIG. 36 is another circuit configuration diagram of the induction heating cooker.

FIG. 37 is a circuit configuration diagram of a conventional induction heating cooker.

FIG. 38 is an operation waveform diagram of each part of the inverter circuit of the induction heating cooker.

FIG. 39 is a characteristic diagram of the conduction ratio and the input power of the induction heating cooker.

[Explanation of symbols]

1 DC Power Supply 2 Inverter Circuit 3 Drive Control Circuit 4 Heating Coil 5 IGBT (First Switching Element) 6 First Resonant Capacitor 7 IGBT (Second Switching Element) 8 Second Resonant Capacitor 9 Current Transformer (Input Current Detecting Means) 10 iin Detection circuit (input current detection means) 16 Input setting means 17 Comparison means 18 Drive control circuit 19 ton1 detection circuit (conduction time detection means) 21 vce1 detection circuit (first switching element voltage detection means) 22 Drive control circuit 23 Drive control circuit 24 vce2 detection circuit (second switching element voltage detection means) 25 drive control circuit 26 drive control circuit 27 subtraction circuit (subtraction means) 28 drive control circuit 29 current transformer (heating coil current detection means) 30 iL detection circuit (heating coil current) Detection means) 31 Drive control times 32 current transformer (first switching element current detection means) 33 ic1 detection circuit (first switching element current detection means) 34 drive control circuit 35 current transformer (second switching element current detection means) 36 ic2 detection circuit (second switching element) Current detection means) 37 Drive control circuit 38 Drive control circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hidekazu Yamashita 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-5-343173 (JP, A) JP-A-7- 114981 (JP, A) JP 10-149876 (JP, A) JP 10-154575 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H05B 6/12 H05B 6 / 04

Claims (4)

(57) [Claims] 1. A DC power supply, a heating coil connected to one end of the DC power supply, a first switching element connected to the other end of the heating coil and the other end of the DC power supply, and a resonance with the heating coil. A first resonance capacitor forming a circuit, an inverter circuit composed of a series circuit of a second switching element of a reverse current conduction type and a second resonance capacitor connected in parallel with the heating coil or the first resonance capacitor, An input current detection unit that detects an input current of the inverter circuit and a drive control circuit that alternately controls conduction of the both switching elements at a constant frequency are provided, and the drive control circuit outputs the input current detection unit based on an output of the input current detection unit. Controls the conduction ratio of the switching element , and
Of the inverter circuit set according to the conduction time of the switching element.
An induction heating cooker in which the conduction ratio is controlled within the range of input current . 2. A DC power supply, a heating coil connected to one end of the DC power supply, a first switching element connected to the other end of the heating coil and the other end of the DC power supply, and a resonance with the heating coil. A first resonance capacitor forming a circuit, an inverter circuit composed of a series circuit of a second switching element of a reverse current conduction type and a second resonance capacitor connected in parallel with the heating coil or the first resonance capacitor, A first switching element voltage detecting means for detecting the voltage across the first switching element, and the second switching element.
Second switching element that detects the voltage across the switching element
Child voltage detection means, and a drive control circuit for alternately conducting the switching elements at a constant frequency, the drive control circuit, based on the output of the first switching element voltage detection means, the conduction ratio of both switching elements. Control the
And, it is set according to the voltage of the second switching element.
Within the range of the voltage between both ends of the specified first switching element, both
An induction heating cooker that controls the conduction ratio of switching elements . 3. A DC power supply, a heating coil connected to one end of the DC power supply, a first switching element connected to the other end of the heating coil and the other end of the DC power supply, and a resonance with the heating coil. A first resonance capacitor forming a circuit, an inverter circuit composed of a series circuit of a second switching element of a reverse current conduction type and a second resonance capacitor connected in parallel with the heating coil or the first resonance capacitor, A first switching element voltage detecting means for detecting the voltage across the first switching element, and the second switching element.
Second switching element that detects the voltage across the switching element
Child voltage detection means and voltage across both switching elements
And a drive control circuit that alternately controls conduction of the two switching elements at a constant frequency, the drive control circuit including the switching elements based on the output of the first switching element voltage detection means. Control the conduction ratio of , and the output of the subtraction means below a predetermined value.
An induction heating cooker in which the switching ratio of both switching elements is controlled so that 4. A DC power supply, a heating coil connected to one end of the DC power supply, a first switching element connected to the other end of the heating coil and the other end of the DC power supply, and a resonance with the heating coil. A first resonance capacitor forming a circuit, an inverter circuit composed of a series circuit of a second switching element of a reverse current conduction type and a second resonance capacitor connected in parallel with the heating coil or the first resonance capacitor, The second switching element current detection means for detecting the current of the second switching element, and a drive control circuit for alternately conducting the two switching elements at a constant frequency, the drive control circuit, the second switching element current The conduction ratio of both switching elements is controlled based on the output of the detection means , and the conduction of both switching elements is controlled.
Of the current of the second switching element set according to the time
An induction heating cooker that controls its conduction ratio within the range .