JP3456209B2 - Induction heating device - 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 used in general households and restaurants, and an industrial induction heating apparatus used for metal melting, seamless welding, and the like. The present invention relates to an induction heating device characterized by a method of configuring a power conversion circuit that produces high-frequency alternating current from an alternating-current power source.

[0002]

2. Description of the Related Art The circuit configuration of a conventional induction heating device is shown in FIG.
3 shows. This circuit is described in the magazine "OHM", September 1999, p. 53. In FIG. 13, a rectifier circuit 21 including a diode bridge is connected to the single-phase AC power source 1 via a high frequency filter 20, and a DC output side of the rectifier circuit 21 is connected to a DC power source through a power source filter 22 including a reactor and a capacitor. Is connected to an inverter circuit for producing high frequency alternating current. Here, the power supply filter 22 performs a non-smoothing operation and plays a role of attenuating high-frequency switching ripple.

The inverter circuit includes a heating coil 11, a resonance capacitor 10, a diode 8 and a switching element 6.
It is configured as a one-stone resonance type inverter consisting of.
Further, the switching element 7, the diode 9 and the resonance capacitor 5 play a role of clamping the resonance voltage.

In the above structure, when the switching element 6 is turned on, the heating coil 11 is connected to the DC power source composed of the rectifying circuit 21, so that the current increases linearly. At this time, the capacitor 10 is charged to the power supply voltage. When the switching element 6 is turned off, the current of the heating coil 11 flows into the capacitor 10 and the voltage of the capacitor 10 gradually rises. As a result, the voltage of the switching element 6 also gently rises, and a so-called zero voltage switching operation is performed.

When the voltage of the capacitor 10 reaches the DC power supply voltage + the voltage of the capacitor 5, the diode 9 naturally conducts and the current of the heating coil 11 is absorbed by the capacitor 5. Since the capacitor 5 is designed to have a sufficiently large capacity, the voltage of the switching element 6 is clamped to a substantially constant value.

If the switching element 7 is turned on while the current is flowing through the diode 9, the current in the heating coil 11 is reversed, and the resonance with the heating coil 11 causes the current to flow from the resonance capacitor 5 through the switching element 7. Is supplied. When the switching element 7 is turned off at any time in this mode, the current of the heating coil 11 is supplied from the capacitor 10. After that, the voltage of the capacitor 10 and the voltage of the switching element 6 gradually drop, and when these voltages reach zero, the diode 8 naturally conducts to perform a zero-voltage turn-on operation.

Next, FIG. 14 is a circuit diagram showing another conventional technique. In FIG. 14, a rectifier circuit 71 formed of a three-phase diode bridge is connected to the output terminals R, S, and T of the three-phase AC power supply 61, and a smoothing capacitor 72 is connected to both ends of the DC output terminal. There is. A series circuit of resonance capacitors 73 and 74 is connected to the capacitor 72.

Switching elements 75 and 78 are connected in series at both ends of the series circuit of the resonance capacitors 73 and 74,
Each switching element 75, 78 has a freewheeling diode 7
6, 79 and capacitors 77, 80 are connected in parallel. Further, the heating coil 11 is connected between the internal connection point of the series circuit of the resonance capacitors 73 and 74 and the internal connection point of the series circuit of the switching elements 75 and 78.

In the prior art of FIG. 14, a rectifying circuit 71
The capacitor 72 converts the three-phase AC voltage into a DC voltage, and the capacitors 73 and 74 and the heating coil 11 generate a high frequency current by the resonance operation thereof. The switching elements 75 and 78 control the high frequency current flowing through the heating coil 11, and the capacitors 77 and 80 play a role of soft switching the switching elements 75 and 78.

Next, the operation of this prior art will be described. For example, when the switching element 75 is turned on, the capacitor 7
When the switching element 75 is turned off, a current flows through the path of 3 → switching element 75 → heating coil 11 → capacitor 73, and the current is commutated to the path of heating coil 11 → capacitor 74 → capacitor 80 → heating coil 11. At this time, the voltage of the capacitor 77 gradually increases, so that soft switching is established for the switching element 75.

Next, when the voltage of the capacitor 80 becomes zero, the current flows in the anti-parallel diode 79 of the switching element 78.
When the switching element 78 is turned on, the soft switching is established for the switching element 78. When the switching element 78 is turned on, the heating coil 11
The electric current flowing in is reversed, and the electric current flows in the path of the heating coil 11, the switching element 78, the capacitor 74, and the heating coil 11.

Further, when the switching element 78 is turned off, the current flowing through the heating coil 11 is changed.
→ capacitor 80 → capacitor 74 → heating coil 11 path and heating coil 11 → capacitor 77 → capacitor 73 → heating coil 11 path is shunted to the capacitor 8
As the voltage of 0 gradually increases, the switching element 78
Soft switching is established.

When the voltage of the capacitor 77 becomes zero, the current flowing through the heating coil 11 is
→ The anti-parallel diode 76 of the switching element 75 → the capacitor 73 → flows in the path of the heating coil 11, and when the switching element 75 is turned on while the current is flowing through the diode 76, the soft switching of the switching element 75 is established.

By repeating such switching, a high-frequency current is supplied to the heating coil 11, and the electric power supplied to the heating coil 11 can be controlled by changing the conduction ratio or the frequency of the switching elements 75 and 78. . Here, when power is supplied to the heating coil 11, the DC voltage of the capacitor 72 drops, and when this voltage drops below the input voltage, a charging current for the capacitor 72 flows from the input side through the three-phase bridge rectifier circuit 71.

[0015]

In the prior art shown in FIG. 13, the AC power supply voltage is rectified by the rectifier circuit 21, once converted into DC, and then heated using a high frequency switching circuit composed of a single-stone resonant inverter. The coil 11 is driven at high frequency. Here, looking at the flow of electric power, the electric power is supplied from the AC power supply 1 to the inverter circuit via the high frequency filter 20, the rectifier circuit 21, and the power supply filter 22.

On the other hand, the current flow path is from the AC power supply 1 to the high frequency filter 20, the two diodes in the rectifier circuit 21, the power supply filter 22, the heating coil 11 and the switching element 6 when the switching element 6 is on. Become. It is the two diodes in the rectifier circuit 21 and the switching element 6 that cause a large loss due to the current flow among these parts. Particularly, due to the power loss due to the plurality of diodes, the conversion efficiency is lowered and the heat treatment is not performed. For this reason, there have been problems such as an increase in the size of the device and an increase in the cost of the device due to the increased capacity of the cooling fins.

Further, according to the conventional technique shown in FIG. 14, in order to supply the electric power to the heating coil 11, the voltage in the rectifier circuit 71 is reduced.
One diode and one switching element 75 or 7
A current flows through 8. Therefore, the power loss is large as in the prior art of FIG. 13, and the same problem as described above occurs.

Therefore, the present invention intends to provide an induction heating apparatus in which power loss is reduced by a circuit configuration in which a current flows from an AC power source through a minimum number of diodes to a switching element to directly convert it into a high frequency AC. To do.

In order to solve the above problems, the invention according to claim 1 is a diode series circuit including two diodes, a capacitor series circuit including two resonance capacitors, a switching element and a diode connected in anti-parallel. And a switching arm series circuit composed of two switching arms each configured by
One end of an AC power supply is connected to the internal connection point of the diode series circuit, the other end of the AC power supply is connected to the internal connection point of the capacitor series circuit, and a capacitor for turning off the heating coil and the switching element at zero voltage. One end of a parallel circuit consisting of and is connected to the internal connection point of the switching arm series circuit, and the other end of the parallel circuit of the heating coil and the capacitor is connected to the internal connection point of the capacitor series circuit , and two resonances are connected. Add one side of the capacitor
The heat coil is made to resonate .

According to a second aspect of the present invention, a diode series circuit including two diodes, a capacitor series circuit including two resonant capacitors, and two switching elements and diodes respectively connected in antiparallel are provided. And a capacitor for switching off the switching element to zero voltage are connected in parallel to the switching arm in series with the switching arm series circuit including the switching arm of the AC and the AC is connected to the internal connection point of the diode series circuit. One end of the power supply is connected, the other end of the AC power supply is connected to the internal connection point of the capacitor series circuit, one end of the heating coil is connected to the internal connection point of the switching arm series circuit, and the other end of the heating coil is connected. Two resonance capacitors are connected to the internal connection point of the capacitor series circuit. Resonating the heating coil with one of the capacitors
It was made to let .

[0021]

[0022]

According to a third aspect of the present invention, four switching arms each including an anti-parallel connected switching element and a diode are formed to form first to fourth switching arms. A switching arm, a parallel circuit of a heating coil and a capacitor, and a second circuit
And a series circuit of the third switching arm, the resonance capacitor, and the fourth switching arm are connected to both ends of the parallel circuit of the heating coil and the capacitor.

According to a fourth aspect of the present invention, four switching arms each including an anti-parallel connected switching element and a diode are formed to form first to fourth switching arms, and each of these switching arms is formed. Connect the capacitors in parallel and connect the first
A switching arm, a heating coil, and a second switching arm are connected in series, and a series circuit of a third switching arm, a resonant capacitor, and a fourth switching arm is connected to both ends of the heating coil. It is a thing.

According to a fifth aspect of the present invention, four switching arms including switching elements and diodes connected in anti-parallel are formed to form first to fourth switching arms. First and second
And the second switching arm are connected in series in this order to form a first series circuit, and the third switching arm and the fourth switching arm are connected in series to form a second series circuit. And connecting the first series circuit and the second series circuit in parallel, and connecting one end of the AC power supply to the connection point between the first switching arm and the first resonance capacitor to form the second resonance circuit. The other end of the AC power supply is connected to the connection point between the capacitor and the second switching arm, and the internal connection point of the first and second resonant capacitors and the second
The parallel circuit of the heating coil and the capacitor is connected between the internal connection point of the series circuit of 1) and the internal connection point.

According to a sixth aspect of the present invention, four switching arms each including an anti-parallel connected switching element and a diode are formed to form first to fourth switching arms, and each of these switching arms is formed. A capacitor is connected in parallel, the first switching arm, the first and second resonant capacitors, and the second switching arm are connected in series in this order to form a first series circuit, and a third switching circuit is formed. The arm and the fourth switching arm are connected in series to form a second series circuit, the first series circuit and the second series circuit are connected in parallel, and the first switching arm and the first resonance are connected. One end of the AC power supply is connected to the connection point with the capacitor, and the other end of the AC power supply is connected to the connection point between the second resonant capacitor and the second switching arm. A heating coil is connected between the internal connection point of the first and second resonance capacitors and the internal connection point of the second series circuit.

The invention according to claim 7 is configured by two diode series circuits including two diodes, a capacitor series circuit including two resonant capacitors, a switching element and a diode connected in anti-parallel, respectively. A switching arm series circuit composed of two switching arms connected in parallel, and a capacitor for turning off the switching element at zero voltage is connected in parallel to the switching arm.
The first output terminal and the third output terminal of the three-phase AC power supply are connected to the internal connection points of each circuit of the diode series circuit, and the second output terminal of the three-phase AC power supply is connected to the internal connection point of the capacitor series circuit. While connecting the output terminal, one end of the heating coil is connected to the internal connection point of the switching arm series circuit, the other end of the heating coil is connected to the internal connection point of the capacitor series circuit , and one of the two resonance capacitors is connected. When
The heating coil is made to resonate .

The invention according to claim 8 is composed of two diode series circuits including two diodes, a capacitor series circuit including two resonance capacitors, a switching element and a diode connected in anti-parallel, respectively. A switching arm series circuit composed of two switching arms is connected in parallel, and the first output terminal and the third output terminal of the three-phase AC power supply are connected to the internal connection points of each circuit of the diode series circuit. A second output terminal of a three-phase AC power source is connected to an internal connection point of the capacitor series circuit, and one end of a parallel circuit of a heating coil and a capacitor for turning off the switching element to zero voltage is connected to the switching arm. Connected to the internal connection point of the series circuit, the other end of the parallel circuit of the heating coil and the capacitor, Connect to the internal connection point of the capacitor series circuit and connect one of the two resonant capacitors and the heating coil together.
It was made to shake .

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a first embodiment of the present invention and corresponds to the embodiment of the invention described in claim 1. In FIG. 1, a diode series circuit including diodes 2 and 3, a capacitor series circuit including resonant capacitors 4 and 5, a switching arm including a switching element 6 and a diode 8 connected in anti-parallel, and
A switching arm series circuit composed of a switching arm composed of a switching element 7 and a diode 9 is connected in parallel. One end of the AC power supply 1 is connected to the internal connection point of the diode series circuit, and the other end of the AC power supply 1 is connected to the internal connection point of the capacitor series circuit.
One end of the parallel circuit of the heating coil 11 and the capacitor 10 is connected. The other end of the parallel circuit of the heating coil 11 and the capacitor 10 is connected to the internal connection point of the switching arm series circuit.

Next, the operation of this embodiment will be described. When the switching element 6 is turned on during the period when the AC power supply voltage is positive, the heating coil is moved along the path of the AC power supply 1 → diode 2 → switching element 6 → heating coil 11 → AC power supply 1 (this direction is called the positive direction). The current of 11 increases.
At this time, the capacitor 10 is charged so that the switching element 6 side is positive, and the polarity is positive.
Here, since the resonance capacitor 4 is connected in parallel to the AC power source 1 via the diode 2, in terms of high frequency,
The current of the heating coil 11 is supplied from the resonance capacitor 4.

When the switching element 6 is turned off, the current of the heating coil 11 flows into the capacitor 10, so that the voltage of the capacitor 10 is gradually lowered and the switching element 6 is in the zero voltage turn-off operation. When the voltage of the capacitor 10 drops, then the diode 9 naturally conducts and charges the resonant capacitor 5 to a positive polarity via the heating coil 11. At this time, if the switching element 7 is turned on,
Since the resonance capacitor 5 and the heating coil 11 form a resonance circuit, the current is inverted in the path passing through the switching element 7, and the resonance capacitor 5 is charged in the negative direction. When the switching element 7 is turned off in this state, the current in the heating coil 11 discharges the capacitor 10.

After that, the voltage of the switching element 7 gradually rises, and the switching element 7 is in the zero-voltage turn-off operation. Next, the diode 8 naturally conducts and charges the resonance capacitor 4. At this time, when the switching element 6 is turned on, the resonance capacitor 4 and the heating coil 11 form a resonance circuit, so that the current is reversed to the path passing through the switching element 6.

By repeating the above-described operation at a high frequency, a high frequency current is supplied to the heating coil 11. Further, while the AC power supply 1 is in the negative period, the operations of the switching elements 6 and 7 are reversed from the operations in the AC power supply 1 in the positive period, and the entire operation is similar.

According to this embodiment, when the AC power supply 1 supplies power to the heating coil 11 while the AC power supply voltage is positive or negative, the number of semiconductor elements through which the current passes is one diode and one switching element. As a result, the power loss is reduced and the conversion efficiency is improved as much as the number of diodes is reduced.

Next, FIG. 2 shows a second embodiment of the present invention, which corresponds to the embodiment of the invention described in claim 2. In this embodiment, the capacitor 10 connected in parallel to the heating coil 11 in FIG. 1 is deleted, and capacitors 12 and 13 are connected in parallel to each switching arm.

The operation of this embodiment will be described below. When the switching element 6 is turned on during the positive period of the AC power supply 1, the AC power supply 1 → diode 2 → switching element 6 →
The current of the heating coil 11 increases in the path from the heating coil 11 to the AC power supply 1. At this time, similarly to the above, the resonance capacitor 4 supplies a current in terms of high frequency.

Next, when the switching element 6 is turned off, the current of the heating coil 11 charges the capacitor 12,
In addition, the capacitor 13 flows into the resonance capacitor 5 in a direction of discharging the capacitor 13, the voltage of the capacitor 12 gradually rises, and the switching element 6 performs a zero-voltage turn-off operation.
Then, the diode 9 conducts naturally and the heating coil 11
The current flowing through the capacitor charges the resonance capacitor 5. At this time,
When the switching element 7 is turned on, the resonance capacitor 5
Since the heating coil 11 and the heating coil 11 form a resonance circuit, the current is inverted to a path passing through the switching element 7. When the switching element 7 is turned off in this state, the heating coil 1
The current of 1 charges the capacitor 13 and
In the direction of discharging 2, the resonant capacitor 4 flows into the switching capacitor 7, and the switching element 7 operates in a zero-voltage turn-off mode.

The diode 8 then conducts naturally and the current flowing through the heating coil 11 charges the resonant capacitor 4.
At this time, when the switching element 6 is turned on, the resonance capacitor 4 and the heating coil 11 form a resonance circuit, so that the current is inverted to the path passing through the switching element 6.

By repeating such an operation at a high frequency, a high frequency current is supplied to the heating coil 11.
During the period when the AC power supply voltage is negative, the switching elements 6 and 7 are
Only by reversing the operation of (1) to the operation of the positive period, the entire operation becomes similar.

[0040] FIG. 3 is a circuit diagram showing a third embodiment of the present invention. This embodiment is a series circuit of a diode series circuit including diodes 2 and 3, a switching arm including switching element 6 and diode 8 connected in anti-parallel, and a switching arm including switching element 7 and diode 9. A switching arm series circuit of 1 and a switching arm including a switching element 14 and a diode 16 connected in anti-parallel,
Also, a second switching arm series circuit, which is a series circuit of switching arms composed of the switching element 15 and the diode 17, and a capacitor 23 are connected in parallel, and one end of the AC power supply 1 is connected to an internal connection point of the diode series circuit. The other end of the AC power supply 1 is connected to the internal connection point of the first switching arm series circuit, and the heating coil 11 and the capacitor 1 are connected via the resonance capacitor 4.
0 is connected to one end of a parallel circuit, and the other end of the parallel circuit of the heating coil 11 and the capacitor 10 is connected to the internal connection point of the second switching arm series circuit.

To explain the operation of this embodiment, the switching element 7 is turned on and the switching element 6 is turned off while the AC power supply voltage is positive. When the switching element 14 is turned on in this state, the current increases in the path of AC power supply 1 → diode 2 → switching element 14 → heating coil 11 → resonance capacitor 4 → AC power supply 1 (referred to as the positive direction). At this time, the capacitor 10 is charged so that the side of the switching element 14 becomes positive, and the polarity is positive. Since the switching element 7 is turned on in this state, the capacitor 23 is connected in parallel to the AC power source 1 via the diodes 2 and 9, and the current of the heating coil 11 is supplied from this capacitor 23 in terms of high frequency. To be done.

Next, when the switching element 14 is turned off, the current of the heating coil 11 flows into the capacitor 10, so that the voltage of the capacitor 10 gradually decreases, and the switching element 14 becomes a zero voltage turn-off operation.
The diode 17 conducts naturally. At this time, when the switching element 15 is turned on, the current of the heating coil 11 decreases due to the resonance phenomenon, and then the current is reversed. In this state, the capacitor 10 is charged negatively. Then, when the switching element 15 is turned off, the current of the heating coil 11 flows into the capacitor 10, the voltage of the capacitor 10 gradually rises, and the switching element 15 performs the zero-voltage turn-off operation.

The diode 16 then conducts naturally and the current in the heating coil 11 charges the capacitor 23 in the path through the diode 9. At this time, when the switching element 14 is turned on, the resonance operation causes the current in the heating coil 11 to increase in the positive direction.

By repeating such an operation at a high frequency, a high frequency current is supplied to the heating coil 11.
Further, while the AC power supply voltage is negative, the switching element 6 is turned on, the switching element 7 is turned off, and the switching elements 15 and 14 are alternately turned on and off, so that the heating coil 11 similarly has a high-frequency current. Is supplied.

[0045] FIG. 4 is a fourth embodiment of the present invention. In this embodiment, the capacitor 10 connected in parallel to the heating coil 11 is deleted from FIG. 3, and the capacitors 18 and 19 are connected in parallel to the respective switching arms forming the second switching arm series circuit. That is, the capacitor 18 is connected in parallel to the antiparallel connection circuit of the switching element 14 and the diode 16, and the capacitor 19 is connected in parallel to the antiparallel connection circuit of the switching element 15 and the diode 17.

The operation of this embodiment will be described. First, the switching element 7 is turned on while the AC power supply voltage is positive,
The switching element 6 is turned off. When the switching element 14 is turned on in this state, the path of the AC power supply 1 → diode 2 → switching element 14 → heating coil 11 → resonance capacitor 4 → AC power supply 1 (referred to as the positive direction)
The current increases at. The voltage polarity of the capacitor 4 at this time is positive. Since the switching element 7 is turned on here, the capacitor 23 is connected in parallel to the AC power source 1 via the diodes 2 and 9, and the current of the heating coil 11 is supplied from this capacitor 23 in terms of high frequency. It

Next, when the switching element 14 is turned off, the current of the heating coil 11 charges the capacitor 18,
In addition, the capacitor 19 flows in a direction of discharging, the voltage of the capacitor 18 gradually rises, and the switching element 14
Is a zero-voltage turn-off operation. And diode 1
7 naturally conducts. At this time, when the switching element 15 is turned on, the current of the heating coil 11 decreases due to the resonance phenomenon, and then the current is reversed. When the switching element 15 is turned off in this state, the current of the heating coil 11 flows in the direction of charging the capacitor 19 and discharging the capacitor 18, and the switching element 15 is in the zero voltage turn-off operation.

After that, the diode 16 conducts naturally,
The current in the heating coil 11 charges the capacitor 23 along the path through the diode 9. At this time, the switching element 14
When is turned on, the resonance operation causes the current in the heating coil 11 to increase in the positive direction. By repeating such an operation at a high frequency, a high frequency current is supplied to the heating coil 11. While the AC power supply 1 is in the negative period, the switching element 6 is turned on, the switching element 7 is turned off, and the switching elements 15 and 14 are alternately turned on and off, so that a high frequency current is supplied to the heating coil 11 as well. To be done.

FIG. 5 shows a fifth embodiment of the present invention, which corresponds to the embodiment of the invention described in claim 3 . In this embodiment, a first switching arm composed of a switching element 6 and a diode 8 connected in anti-parallel, a parallel circuit of a heating coil 11 and a capacitor 10, and a switching element 14 and a diode 16 connected in anti-parallel. A series circuit with the second switching arm is connected to the AC power supply 1 in parallel. A third switching arm including the switching element 7 and the diode 9 connected in anti-parallel, a resonance capacitor 4, and a fourth switching arm including the switching element 15 and the diode 17 connected in anti-parallel.
The series circuit with the switching arm of the heating coil 11
Are connected in parallel to.

The operation of this embodiment will be described. While the AC power supply voltage is positive, the switching elements 6 and 7 are turned on, and the switching elements 14 and 15 are alternately turned on and off at a high frequency. When the switching element 14 is turned on, the current of the heating coil 11 increases in the route of AC power supply 1 → diode 8 → parallel circuit of heating coil 11 and capacitor 10 → switching element 14 → AC power supply 1. At this time, the capacitor 10 is charged to the power supply voltage. Next, when the switching element 14 is turned off, the voltage of the capacitor 10 gradually decreases, and the switching element 14 performs a zero voltage turn-off operation.

Next, the diode 17 naturally conducts and charges the resonance capacitor 4 via the switching element 7. At this time, when the switching element 15 is turned on, the resonance capacitor 4 and the heating coil 11 compose a resonance circuit, so that the current flows through the diode 9 and the switching element 1.
Reverse the path through 5. When the switching element 15 is turned off in this state, the voltage of the capacitor 10 gradually rises, and the switching element 15 performs a zero-voltage turn-off operation.

By repeating such an operation at a high frequency, a high frequency current is supplied to the heating coil 11.
Further, when the AC power supply voltage is negative, the switching elements 14 and 15 are turned on, and the switching elements 6 and 7 are alternately turned on and off, whereby the same operation is performed.

FIG. 6 shows a sixth embodiment of the present invention and corresponds to the embodiment of the invention described in claim 4 . In this embodiment, the capacitor 10 connected in parallel with the heating coil 11 in FIG. 5 is deleted, and the capacitors 12, 13, 18, 19 are connected in parallel with the respective switching arms.

As for its operation, while the AC power supply voltage is positive, the switching elements 6 and 7 are turned on, and the switching elements 14 and 15 are alternately turned on and off at a high frequency. When the switching element 14 is turned on, the AC power supply 1
→ diode 8 → heating coil 11 → switching element 1
4 → The current of the heating coil 11 increases in the path of the AC power supply 1.

Next, when the switching element 14 is turned off, the voltage of the capacitor 18 gradually rises, and the switching element 14 performs a zero voltage turn-off operation. After that, the diode 17 naturally conducts and charges the resonance capacitor 4 via the switching element 7. At this time, when the switching element 15 is turned on, the resonance capacitor 4 and the heating coil 11 form a resonance circuit, so that the current is inverted to the path passing through the diode 9 and the switching element 15. If the switching element 15 is turned off in this state,
The voltage of the capacitor 19 gradually rises, and the switching element 15 performs a zero voltage turn-off operation.

By repeating the above operation at high frequency, a high frequency current is supplied to the heating coil 11. Further, while the AC power supply voltage is negative, the switching elements 14 and 15 are turned on, and the switching elements 6 and 15 are turned on.
The same operation is performed by alternately turning 7 on and off.

FIG. 7 shows a seventh embodiment of the present invention, which is another embodiment of the present invention as set forth in claim 3 . Further, FIG. 8 shows an eighth embodiment of the present invention and shows another embodiment of the invention described in claim 4 . These embodiments differ in that the connecting directions of the switching arms (switching elements and diodes connected in antiparallel to each other) are opposite to those in FIGS. 5 and 6 when the AC power supply 1 is used as a reference. It is a point. The operation of FIGS. 7 and 8 is the same as that of FIGS. 5 and 6, and thus the description thereof is omitted.

FIG. 9 shows a ninth embodiment of the present invention, which corresponds to the embodiment of the invention described in claim 5 . In this embodiment, a first switching arm including a switching element 6 and a diode 8 connected in antiparallel, a first resonance capacitor 4, a second resonance capacitor 5, a switching element 7 connected in antiparallel, and The second switching arm composed of the diode 9 is connected in series in this order to form a first series circuit. In addition, a third switching arm including the switching element 14 and the diode 16 connected in anti-parallel and a fourth switching arm including the switching element 15 and the diode 17 connected in anti-parallel are connected in series to each other. A series circuit is constructed. The first series circuit and the second series circuit are connected in parallel.

Furthermore, one end of the AC power supply 1 is connected to the connection point between the first switching arm and the first resonance capacitor 4, and the connection point between the second switching arm and the second resonance capacitor 5 is connected. The other end of the AC power supply 1 is connected.
The heating coil 1 is provided between the connection point between the third switching arm and the fourth switching arm and the connection point between the first resonance capacitor 4 and the second resonance capacitor 5.
A parallel circuit of 1 and the capacitor 10 is connected.

Explaining the operation of this embodiment, when the switching element 14 is turned on while the switching elements 6 and 7 are on during the positive period of the AC power supply voltage, the resonance capacitor 4 → diode 8 → switching element 14 → A resonance current flows in the path of the parallel circuit of the heating coil 11 and the capacitor 10. When the switching element 14 is turned off here, the electric charge of the capacitor 10 is discharged by the current of the heating coil 11, the voltage across the switching element 14 gradually increases, and finally the heating coil 11 → resonance capacitor 5 → switching element 7 → A resonance current flows through the path of the diode 17, and the current of the heating coil 11 decreases. At this time, when the switching element 15 is turned on, this current becomes a resonance current in the path of the resonance capacitor 5 → the parallel circuit of the heating coil 11 and the capacitor 10 → the switching element 15 → the diode 9.

When the switching element 15 is turned off, the voltage across the switching element 15 gradually increases as the voltage of the capacitor 10 increases. Due to this voltage increase, the diode 16 becomes conductive, and the current of the heating coil 11 becomes a path passing through the diode 16 → the switching element 6 → the resonance capacitor 4. At this time, the switching element 1
When 4 is turned on, the resonance current is inverted.

By repeating the above operation, a high frequency current flows through the heating coil 11, and at this time, the switching elements 14 and 15 perform a zero voltage switching operation. Further, during the period when the AC power supply voltage is negative, the switching element 1
Similarly, the heating coils 11 and 4 are turned on and the switching elements 6 and 7 are turned on and off alternately.
High-frequency current flows through.

FIG. 10 shows a tenth embodiment of the present invention and corresponds to the embodiment of the invention described in claim 6 .
The difference from FIG. 9 is that the capacitor 10 connected in parallel to the heating coil 11 is deleted, and capacitors 12, 13 are connected in parallel with the first to fourth switching arms, respectively.
18 and 19 are connected.

The operation of this embodiment is basically the same as that of FIG. 9, but the difference is that in FIG. 9, the zero voltage switching operation of the switching element is performed by the voltage change of the capacitor 10 connected in parallel with the heating coil 11. Was realized,
In the embodiment of FIG. 10, the capacitors 12, 13, 18, and 19 connected in parallel with the respective switching arms play the role.

Although not shown, the high frequency filter 20 and the power supply filter 22 shown in FIG. 13 may be used in combination in the above embodiments.

Next, FIG. 11 shows an eleventh embodiment of the present invention, which corresponds to the embodiment of the invention described in claim 7 . In FIG. 11, the first output terminal R of the three-phase AC power supply 61 is connected to the internal connection point of the series circuit of the diodes 81 and 82, and the third output terminal T of the three-phase AC power supply 61 is the diode 83, 84. It is connected to the internal connection point of the series circuit. In addition, the second output terminal S of the three-phase AC power supply 61
Is connected to the internal connection point of the series circuit of the resonance capacitors 73 and 74 and one end of the heating coil 11.

Switching elements 75 and 78 are connected in series at both ends of the series circuit of the resonance capacitors 73 and 74,
Each switching element 75, 78 has a freewheeling diode 7
6, 79 and capacitors 77, 80 are connected in parallel. The other end of the heating coil 11 is connected to the internal connection point of the series circuit of the switching elements 75 and 78.

Next, the operation of this embodiment will be described.
For example, when the switching element 75 is turned on while the capacitor 73 is charged, the path of the capacitor 73 → the switching element 75 → the heating coil 11 → the capacitor 73 and the output terminal R → the diode 81 → the switching element 7
5 → heating coil 11 → output terminal S → AC power supply 61 → output terminal R, when a current flows and the switching element 75 is turned off, the current is transferred to the route of heating coil 11 → capacitor 74 → capacitor 80 → heating coil 11. Shed. At this time, the voltage of the capacitor 77 gradually rises, so that soft switching (zero voltage turn-off operation) is established for the switching element 75.

When the voltage of the capacitor 80 becomes zero, the current commutates to the antiparallel diode 79 of the switching element 78, and when the switching element 78 is turned on at this time, soft switching is established for the switching element 78. When the switching element 78 is turned on, the heating coil 1
The current flowing in 1 is reversed, and the path of the heating coil 11 → switching element 78 → capacitor 74 → heating coil 11 and the output terminal S → heating coil 11 → switching element 78 → diode 84 → output terminal T → AC power source 61 →
It flows to the path of the output terminal S.

Further, when the switching element 78 is turned off, the current flowing through the heating coil 11 becomes
Capacitor 80 → capacitor 74 → heating coil 11 path and heating coil 11 → capacitor 77 → capacitor 7
3 → The current is shunted to the path of the heating coil 11, and the voltage of the capacitor 80 gradually rises, whereby soft switching (zero voltage turn-off operation) of the switching element 78 is established.

When the voltage of the capacitor 77 becomes zero, the current flowing through the heating coil 11 changes from the heating coil 11 to the anti-parallel diode 76 of the switching element 75 to the capacitor 7.
3 → flows through the path of the heating coil 11 and the anti-parallel diode 7
When the switching element 75 is turned on while the current is flowing through 6, the soft switching of the switching element 75 is established.

By repeating such switching, a high frequency current is supplied to the heating coil 11, and the power supplied to the heating coil 11 can be controlled by changing the conduction ratio or the frequency of the switching elements 75, 78.

According to the present embodiment, the semiconductor element through which the current passes to supply the electric power to the heating coil 11 always has one diode and one switching element. Since the number of diodes is two and the number of switching elements is one, the number of semiconductor elements through which the current passes is reduced, so that power loss can be reduced and the efficiency of the entire apparatus can be improved.

Next, FIG. 12 shows a twelfth embodiment of the present invention, which corresponds to the embodiment of the invention described in claim 8 . In this embodiment, the capacitor 7 in FIG.
7, 80 are removed, and a condenser 85 is connected in parallel to the heating coil 11. The rest of the configuration is the same as in FIG.

The operation of this embodiment will be described below. For example, when the switching element 75 is turned on while the capacitor 73 is charged, the path of the capacitor 73 → the switching element 75 → the heating coil 11 → the capacitor 73,
Output terminal R → diode 81 → switching element 75 →
An electric current flows through the path of heating coil 11 → output terminal S → AC power supply 61 → output terminal R. At this time, the capacitor 85 is charged to the same voltage as the capacitor 73.

When the switching element 75 is turned off, current is commutated in the path of the heating coil 11, the capacitor 74, the antiparallel diode 79 of the switching element 78, the heating coil 11, and the path of the heating coil 11, the capacitor 85, and the heating coil 11. To do. In this state, the difference between the voltage of the capacitor 73 and the voltage of the capacitor 85 is the switching element 75.
Since the voltage of the switching element 75 gradually increases as the voltage of the capacitor 85 gradually decreases, the soft switching of the switching element 75 is established.

Next, when the switching element 78 is turned on while the current is flowing through the anti-parallel diode 79 of the switching element 78, the current flowing through the heating coil 11 is reversed and the heating coil 11 → the switching element 78 → the capacitor. 74 → path of heating coil 11 and output terminal S → heating coil 11 → switching element 78 → diode 84
→ Output terminal T → AC power supply 61 → Output terminal S At this time, the capacitor 85 is charged to the same voltage as the capacitor 74.

When the switching element 78 is turned off, the current flowing through the heating coil 11 is the heating coil 11 → the anti-parallel diode 76 of the switching element 75 → the capacitor 73 →
The flow is divided into the path of the heating coil 11 and the path of the heating coil 11 → the condenser 85 → the heating coil 11. In this state, the difference between the voltage of the capacitor 74 and the voltage of the capacitor 85 is applied to both ends of the switching element 78, and the voltage of the switching element 78 gradually increases as the voltage of the capacitor 85 gradually increases. Therefore, soft switching of the switching element 78 is established.

Further, the soft switching of the switching element 75 is established by turning on the switching element 75 while the current is flowing through the anti-parallel diode 76 of the switching element 75. By repeating such switching, a high frequency current is supplied to the heating coil 11,
The power supplied to the heating coil 11 can be controlled by the conduction ratio or frequency of the switching elements 75, 78.

Also in this embodiment, the semiconductor element through which the current passes to supply the electric power to the heating coil 11 is always one diode and one switching element,
By reducing the number of semiconductor elements through which the current passes as compared with the conventional technique of FIG. 14, it is possible to reduce power loss and improve efficiency.

[0081]

As described above, in the present invention, a high frequency alternating current can be passed through the heating coil without once converting the alternating current into the direct current as in the prior art. As a result,
The number of semiconductor elements through which the current passes when supplying power from the AC power supply to the heating coil is one diode and one switching element in any configuration.

That is, in the prior art, when the power is supplied to the heating coil, the current is two diodes and the switching element 1
According to the invention, one diode
The number of pieces is reduced, and the following effects can be obtained. (1) Since the number of semiconductor elements through which current passes is reduced, power loss is reduced and conversion efficiency is improved. (2) Due to the reduction in power loss, the fins for cooling the semiconductor element are downsized, and at the same time, the device can be downsized and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a third embodiment of the present invention.

FIG. 4 is a circuit diagram showing a fourth embodiment of the present invention.

FIG. 5 is a circuit diagram showing a fifth embodiment of the present invention.

FIG. 6 is a circuit diagram showing a sixth embodiment of the present invention.

FIG. 7 is a circuit diagram showing a seventh embodiment of the present invention.

FIG. 8 is a circuit diagram showing an eighth embodiment of the present invention.

FIG. 9 is a circuit diagram showing a ninth embodiment of the present invention.

FIG. 10 is a circuit diagram showing a tenth embodiment of the present invention.

FIG. 11 is a circuit diagram showing an eleventh embodiment of the invention.

FIG. 12 is a circuit diagram showing a twelfth embodiment of the invention.

FIG. 13 is a circuit diagram showing a conventional technique.

FIG. 14 is a circuit diagram showing a conventional technique.

[Explanation of symbols]

1,61 AC power supply 2,3,8,9,16,17,76,79,81,8
2,83,84 Diodes 4, 5, 73, 74 Resonant capacitors 6, 7, 14, 15, 75, 78 Switching elements 10, 12, 13, 18, 19, 23, 77, 80, 8
5 Capacitor 11 Heating Coil 20 High Frequency Filter 21 Rectifier Circuit 22 Power Supply Filter R, S, T Output Terminal

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-51-72742 (JP, A) JP-A-2-231965 (JP, A) JP-A-11-121162 (JP, A) JP-A-5- 15171 (JP, A) JP 10-83885 (JP, A) JP 3-263787 (JP, A) JP 8-13888 (JP, A) JP 2000-286051 (JP, A) Open 2000-279319 (JP, A) JP 2000-253989 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05B 6/04 H05B 6/12 H02M 7/48

Claims (8)

(57) [Claims] 1. A diode series circuit composed of two diodes, a capacitor series circuit composed of two resonant capacitors, and a switching composed of two switching arms each composed of a switching element and a diode connected in antiparallel. An arm series circuit is connected in parallel, one end of an AC power supply is connected to an internal connection point of the diode series circuit, and the other end of the AC power supply is connected to an internal connection point of the capacitor series circuit, and a heating coil and the switching circuit are connected. One end of a parallel circuit composed of a capacitor for turning off the element at zero voltage is connected to an internal connection point of the switching arm series circuit, and the other end of the parallel circuit of the heating coil and the capacitor is internally connected to the capacitor series circuit. Connected to one of the two resonant capacitors
An induction heating device characterized in that a heating coil is resonated . 2. A diode series circuit composed of two diodes, a capacitor series circuit composed of two resonant capacitors, and a switching composed of two switching arms each composed of a switching element and a diode connected in antiparallel. An arm series circuit is connected in parallel, and a capacitor for turning off the switching element to zero voltage is connected in parallel to the switching arm, and one end of an AC power supply is connected to an internal connection point of the diode series circuit. , The other end of the AC power source is connected to the internal connection point of the capacitor series circuit, one end of the heating coil is connected to the internal connection point of the switching arm series circuit, and the other end of the heating coil is connected to the inside of the capacitor series circuit. Two resonance capacitors connected to the connection point
An induction heating device characterized in that one side of a heater and a heating coil are resonated . 3. A first to a fourth switching arm are formed by forming four switching arms each composed of a switching element and a diode which are connected in anti-parallel, and a first switching arm and a heating element are provided at both ends of an AC power supply. A parallel circuit of a coil and a capacitor and a series circuit of a second switching arm are connected, and a third switching arm, a resonant capacitor and a fourth switching arm are provided at both ends of the parallel circuit of the heating coil and the capacitor. An induction heating device characterized in that a series circuit of is connected. 4. A first to a fourth switching arm are formed by forming four switching arms each composed of a switching element and a diode connected in anti-parallel, and capacitors are respectively connected in parallel to these switching arms. A series circuit of a first switching arm, a heating coil, and a second switching arm is connected to both ends of the AC power supply, and a third switching arm, a resonant capacitor, and a fourth switching circuit are connected to both ends of the heating coil. An induction heating device characterized in that a series circuit with an arm is connected. 5. The first to fourth switching arms are formed by forming four switching arms each including an antiparallel connected switching element and a diode, and the first switching arm and the first and second resonances. A capacitor and a second switching arm are connected in series in this order to form a first series circuit, and a third switching arm and a fourth switching arm are connected in series to form a second
A first series circuit and a second series circuit are connected in parallel, and one end of an AC power supply is connected to a connection point between the first switching arm and the first resonance capacitor. The other end of the AC power supply is connected to the connection point between the second resonance capacitor and the second switching arm, and between the internal connection point of the first and second resonance capacitors and the internal connection point of the second series circuit. An induction heating device characterized in that a parallel circuit of a heating coil and a capacitor is connected to the. 6. A first to a fourth switching arm are formed by forming four switching arms each including an antiparallel connected switching element and a diode, and capacitors are respectively connected in parallel to these switching arms. The first switching arm, the first and second resonance capacitors, and the second switching arm are connected in series in this order to form a first series circuit, and the third switching arm and the fourth switching arm are formed. The arm is connected in series to form a second series circuit, the first series circuit and the second series circuit are connected in parallel, and at the connection point between the first switching arm and the first resonance capacitor. One end of the AC power supply is connected, and the other end of the AC power supply is connected to the connection point between the second resonance capacitor and the second switching arm. Between the internal connection point of the internal connection point and the second series circuit of capacitors, induction heating apparatus characterized by connecting the heating coil. 7. A diode series circuit comprising two diodes, two circuits, and a capacitor series circuit comprising two resonant capacitors,
A parallel connection with a switching arm series circuit composed of two switching arms each composed of a switching element and a diode connected in anti-parallel, and
A capacitor for turning off the switching element to zero voltage is connected in parallel to the switching arm, and the first output terminal and the third output of the three-phase AC power supply are connected to the internal connection points of each circuit of the diode series circuit. The terminals are respectively connected, and the second output terminal of the three-phase AC power supply is connected to the internal connection point of the capacitor series circuit,
One end of the heating coil is connected to the internal connection point of the switching arm series circuit, the other end of the heating coil is connected to the internal connection point of the capacitor series circuit , and two resonance capacitors are connected.
An induction heating device characterized in that one of the sensors and a heating coil are resonated . 8. A diode series circuit including two diodes, and a capacitor series circuit including two resonant capacitors,
A switching arm series circuit composed of two switching arms each composed of a switching element and a diode connected in anti-parallel is connected in parallel, and a first three-phase AC power supply is provided at an internal connection point of each circuit of the diode series circuit. Connect the output terminal and the third output terminal of
The second output terminal of the three-phase AC power supply is connected to an internal connection point of the capacitor series circuit, and one end of a parallel circuit of a heating coil and a capacitor for turning off the switching element to zero voltage is connected to the switching arm series. It is connected to the internal connection point of the circuit, the other end of the parallel circuit of the heating coil and the capacitor is connected to the internal connection point of the capacitor series circuit, and is connected to one of the two resonance capacitors.
An induction heating device characterized in that a heat coil is resonated .