JP3070249B2 - High frequency inverter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency inverter used for induction heating cookers and the like used in ordinary households .

[0002]

2. Description of the Related Art In recent years, there has been a demand for a high-frequency inverter of this type to expand the range of loads that can be handled by using a plurality of inverters in parallel or reduce noise.

[0003] A conventional high-frequency inverter will be described below with reference to FIGS. In the figure, 1 is a resonance capacitor, and 2 is a resonance coil connected in series to the resonance capacitor 1. Reference numeral 3 denotes a reverse conducting switching element, which is constituted by a diode connected in antiparallel to a bipolar transistor. Reference numeral 4 denotes a control circuit which controls conduction and cutoff of the reverse conduction switching element 3. Reference numeral 5 denotes a DC current source usually composed of a DC voltage source and a DC reactor, and supplies power to the circuit of the resonance capacitor 1, the resonance coil 2, and the reverse conducting switching element 3. The resonance coil 2 normally also serves as a heating coil, and induction heats a load such as a pan (not shown).

In the conventional high-frequency inverter configured as described above, the reverse conducting switching element 3 is periodically turned on and off.
By shutting off, an alternating current flows through the resonance coil 2 and the load is induction-heated by a high-frequency AC magnetic field generated from the resonance coil 2.

FIG. 12 is a waveform diagram showing operation waveforms of the reverse conducting switching element 3 of the high-frequency inverter, where VSW and ISW represent the voltage and current of the reverse conducting switching element 3, respectively. The period T1 indicates a period in which the reverse conducting switching element 3 is cut off, and by changing this, the input power of the high-frequency inverter can be controlled.

[0006]

However, in the above-described conventional configuration, there is a problem that if the period T1 is changed, the oscillation period T0 must be changed in conjunction therewith. That is,
In the conventional configuration, as shown by VSW in FIG. 12, in order to perform zero current switching with a small duty of the switching element, the period t0 to t1 includes the resonance capacitor 1 and the resonance coil 2
Are fixed at the resonance cycle of. Therefore, when the period T1 is changed to control the input power, the oscillation period T0 changes in conjunction.

[0007] The inability to independently control the input power and operating frequency has the following problems in industrial and consumer applications. (1) When using multiple induction heating cookers or induction heating devices in parallel to heat large loads, if the induction heating frequencies of adjacent resonance coils are different, the difference frequency falls within the audible range. Sounds as interference noise. (2) As is well known, a high frequency is suitable for a small load or a non-magnetic load, and a low frequency is suitable for a large load or a magnetic load. Therefore, the desired input power cannot be obtained in this optimum frequency band. For this reason, it is inevitable to narrow the load handling range or perform inefficient heating. (3) Since the operating frequency range is wide, the noise filter cannot cover the noise, and the noise leaking to the power supply increases. In addition, when a specific frequency such as a modulation frequency of an infrared remote control of a television is interfered with a peripheral device, it is difficult to avoid using the frequency.

An object of the present invention is to solve the above-mentioned conventional problems, and it is a first object of the present invention to provide a high-frequency inverter capable of easily and independently controlling power and frequency with a simple configuration. The second to achieve the first object
The second, third and fourth objectives are to provide third and fourth means.

[0009]

The first object of the present invention for achieving the first object is to provide a DC current source, a resonance coil and a resonance capacitor connected in series to the DC current source, A first reverse conducting switching element for driving a coil and a resonant capacitor and the series connected resonance
A second reverse conducting switching element connected in series to the coil and the resonance capacitor, and a control circuit for driving the first and second reverse conducting switching elements; The output current of the current source is arranged so as to be a forward current, and the second reverse conduction switch is arranged .
When the switching element has zero or negative forward current
This is a high-frequency inverter controlled so as to be turned off .

A second means of the present invention for achieving the second object is to drive a DC current source, a resonance coil and a resonance capacitor connected in series to the DC current source, and driving the resonance coil and the resonance capacitor. A first reverse conducting switching element and a second reverse conducting switching element, and a control circuit for driving the first and second reverse conducting switching elements, wherein the first reverse conducting switching element is a direct current source. Is arranged in a direction in which the output current of the DC current source becomes a forward current, and the second reverse conducting switching element is a high-frequency inverter arranged in a direction in which the output current of the DC current source becomes a reverse current.

A third means of the present invention for achieving the third object is a DC current source, a resonance coil and a resonance capacitor connected in series to the DC current source, and the resonance coil and the resonance capacitor. A reverse blocking switching element to be driven, and a resonance capacitor and a resonance capacitor connected in series.
A reverse conduction switching element connected in series to a sensor, and a control circuit for driving the reverse conduction switching element and the reverse conduction switching element, wherein the reverse conduction switching element is arranged so that the output current of the DC current source becomes a forward current. with arranging the reverse conducting switching element, the reverse conducting
The switching element has a forward current of zero or negative.
This is a high-frequency inverter that is controlled to be turned off at the beginning.

Further, a fourth means of the present invention for achieving the fourth object is to provide a DC current source, a resonance coil and a resonance capacitor connected in series to the DC current source, and the resonance coil and the resonance capacitor. A reverse blocking switching element and a reverse conduction switching element to be driven; and a control circuit for driving the reverse blocking switching element and the reverse conduction switching element. The reverse blocking switching element is arranged in a direction in which the output current of the DC current source becomes a forward current. The reverse conducting switching element is a high-frequency inverter arranged in a direction in which the output current of the DC current source becomes a reverse current.

[0013]

The first means of the present invention is to change the conduction ratio of the switching element during one cycle, thereby changing the power while keeping the operation cycle constant, and changing the power while keeping the power constant. , So as to change the operation cycle. Therefore, it is possible to provide a high-frequency inverter capable of controlling power and operating frequency independently.

In the second means of the present invention, since the rise time of the forward current of the first reverse conducting switching element becomes longer, the driving of the gate is facilitated, and the first means of the present invention is further improved. The control circuit can be made compact and inexpensive. Therefore, an inexpensive high-frequency inverter can be provided.

The third means of the present invention operates stably even when there is no load, since the switching element is of the reverse blocking type.

According to the fourth means of the present invention, since the rise time of the forward current of the reverse conducting switching element becomes longer,
The gate can be easily driven, and the control circuit can be made smaller and less expensive than the third means of the present invention.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the first means of the present invention will be described below with reference to FIG. In the figure, reference numerals 6 and 7 indicate a resonance coil and a resonance capacitor connected in series.
The resonance coil 6 inductively heats a pan (not shown) placed thereon. Reference numerals 8 and 9 denote a first reverse conduction switching element and a second reverse conduction switching element for driving the resonance coil 6 and the resonance capacitor 7, respectively. In this embodiment, the first and second reverse conduction switching elements are constituted by bipolar transistors and antiparallel diodes. 10 is the first and second reverse conducting switching element 8
Control circuit for driving 9 Reference numeral 11 denotes a DC current source composed of a DC voltage source and a DC reactor.

The outputs VD1 and VD2 of the control circuit 10 are connected to the gates G1 and G2 of the first reverse conducting switching element 8 and the second reverse conducting switching element 9, respectively. Thus,
The conduction and cutoff of the first reverse conduction switching element 8 and the second reverse conduction switching element 9 are controlled by the control circuit 10. At this time, in this embodiment, the first reverse conducting switching element 8 and the second reverse conducting switching element 9 are arranged in a direction in which the output current IS of the DC current source 11 becomes the forward currents ISW1 and ISW2. In this embodiment, since the high-frequency inverter for induction heating is used, the resonance coil 6
Also serves as a heating coil.

The operation of this embodiment will be described below. In the present embodiment, the first reverse conduction switching element 8 and the second reverse conduction switching element 9 are periodically turned on and off by the control circuit 10, and a high-frequency alternating current is supplied to the resonance coil 6 to generate a high-frequency current. Induction heating of a load such as a pot is induced by a magnetic field. Hereinafter, the operation will be described with reference to FIG. VSW1 and ISW1 represent the voltage and current of the first reverse conduction switching element 8, respectively, VSW2 and ISW2 represent the voltage and current of the second reverse conduction switching element 9, and IL represents the current of the resonance coil 6. The periods T1 and T2 indicate periods in which the first reverse conducting switching element 8 and the second reverse conducting switching element 9 are shut off, respectively.

During the period from t0 to t1, the control circuit 10 causes the first reverse conduction switching element 8 and the second reverse conduction switching element 9 to conduct, and the resonance coil 6, the resonance capacitor 7, and the first reverse conduction switching. In the loop of the element 8 and the second reverse conducting switching element 9, the resonance current becomes ISW
It flows like 2. When the resonance current flows through I SW2, I
SW1 (= IS−ISW2) rises in a resonance arc, once passes through the power supply current IS, rises and falls, and reaches IS again at time t1 when ISW2 becomes zero. The control circuit 10 shuts off the bipolar transistor constituting the second reverse conducting switching element 9 before the time t1 and during a period when the ISW2 is negative. Then, at time t1, the second reverse conducting switching element 9 is naturally turned off, and VSW2 rises. Since the resonance capacitor 7 is shut off during this period, the period t
The voltage between 1 and t2 is maintained. That is, the voltage of the second reverse conducting switching element 9 is maintained at a constant value. When the control circuit 10 conducts the second reverse conduction switching element 9 at time t2, the resonance state is the same as that of the period t0 to t1, and ISW1 rises and falls in an arc of resonance and passes through zero. , Draws a negative resonance arc and reaches zero again at time t3. Next, before time t3, that is, during the period when ISW1 is negative, the bipolar transistor forming the first reverse conducting switching element 8 is cut off. For this reason, at time t3, the first reverse conducting switching element 8 is naturally shut off, and VSW
1 stands up. In the period t3 to t4, the resonance capacitor 13 is charged with the constant current IS, so that VSW1 increases. When the control circuit 10 conducts the first reverse conducting switching element 8 at time t4, the state of the high-frequency inverter returns to the state at time t0, and oscillation continues.

As described above, the high-frequency inverter of the present embodiment changes the cut-off time T2 of the second reverse conducting switching element 9 so that the first reverse conducting switching element 8 can be maintained while maintaining zero current switching. Can be changed freely.

By the way, the power P of the high frequency inverter is I
This is the product of S and the average value of VS, that is, the average value of VSW1. The high-frequency inverter of the present embodiment has the following (1)
It can be seen that frequency and power can be independently variably controlled for the reason (2). (1) As shown in FIG. 3A, the control circuit 10 increases the cut-off period T1 of the first reverse conduction switching element 8 and simultaneously sets the second reverse conduction switching so that T0 is kept constant. The cut-off period T2 of the element 9 is reduced. Therefore, in addition to increasing VSW1, T1 /
Since T0 increases, the average value of VSW1 also increases, and power P increases. That is, the high-frequency inverter of the present embodiment can freely and variably control the power while maintaining the operating frequency constant. (2) When the operation cycle T0 is reduced, the power P increases because T1 / T0 increases. That is, characteristics as shown in FIG. 3B are obtained. In FIG. 3B, for example, the operating point A1
In A2 and A3, the same power P1 can be obtained in different operation periods a1, a2 and a3. Therefore, the frequency can be freely controlled while the power is kept constant.

Since the switching element maintains zero current switching, the duty of the switching element is small, and the noise generated is small.

Next, an embodiment of the second means of the present invention will be described with reference to FIG. 12, 13, 14, 15
Reference numerals 16 and 17 denote a resonance coil, a resonance capacitor, a first reverse conduction switching element, a second reverse conduction switching element, a control circuit, and a DC current source, which are the same as those in the above embodiment. The first reverse conducting switching element 14 is connected to the DC current source 17, the resonance capacitor 13 and the second reverse conducting switching element 15 are connected in series to the DC current source 17, and the resonance coil 12 is connected to the resonance capacitor 13. Inserted in series. Outputs VD1 and VD2 of the control circuit 16 are connected to the gates G1 and G2 of the first reverse conduction switching element 14 and the second reverse conduction switching element 15, respectively, and control the conduction and cutoff of these. In the present embodiment, the first reverse conducting switching element 14 is arranged in a direction in which the output current of the DC current source 17 becomes the forward current I SW1, and the reverse current −I SW2
The second reverse conducting switching element 15 is arranged in the direction as follows.

The operation of the embodiment will be described below with reference to FIG. VSW1 and ISW1 indicate the voltage and current of the first reverse conducting switching element 14, respectively, VSW2 and ISW2 indicate the voltage and current of the second reverse conducting switching element 15, and IL indicates the current of the resonance coil 12. . The periods T1 and T2 indicate periods in which the first reverse conducting switching element 14 and the second reverse conducting switching element 15 are shut off. In the period t0 to t1, the control circuit 1
6, the first reverse conducting switching element 14 and the second reverse conducting switching element 15 are conducting, and the resonance coil 12, the resonance capacitor 13, the first reverse conducting switching element 14, and the second reverse conducting switching element 15 , A resonance current flows like ISW2. ISW1 (= I
S-ISW2) gradually increases, and the time t1 at which ISW2 becomes zero is obtained.
To reach IS. Before the time t1, the control circuit 16 outputs the signal ISW2
Turns off the bipolar transistor constituting the second reverse conducting switching element 15 during the negative period. Then, at time t1, the second reverse conducting switching element 15 is naturally shut off, and VSW2 rises. Since the resonance capacitor 13 is shut off during this period, the voltage between the periods t1 and t2 is maintained. That is, the voltage of the second reverse conducting switching element 15 is maintained at a constant value. Further, at time t2, the control circuit 16
Is turned on, the same resonance state as in the period t0 to t1 is obtained.
ISW1 rises and falls in a resonance arc, passes through zero, and then reaches zero again at time t3 with a negative resonance arc.
Next, before time t3, that is, during the period when ISW1 is negative, the bipolar transistor forming the first reverse conducting switching element 14 is cut off. For this reason, at time t3, the first reverse conducting switching element 14 is naturally shut off, and VSW1
Stand up. In the period t3 to t4, the resonance capacitor 13 is charged with the constant current IS, so that VSW1 increases.
When the control circuit 16 conducts the first reverse conducting switching element 14 at time t4, the state of the high-frequency inverter changes to time t4.
Returning to the state of 0, oscillation continues.

As described above, the high-frequency inverter of this embodiment can independently control the frequency and the power similarly to the above-described embodiment, and maintains the zero-current switching of the switching element. And the noise generated is small.

In the embodiment of the first means of the present invention, ISW1 rapidly reaches the peak ISWP during the period from t0 to t1. For this reason, the first reverse conduction switching element 8 needs to be quickly shifted to a sufficient conduction state. For example, in the case of a bipolar transistor, a large forward base current must flow. Therefore, there is a problem that the control circuit 10 becomes large and expensive. In this regard, in the high-frequency inverter of the present embodiment, the period t0 to ISW1 of FIG.
As is clear from t3, the time required to reach the peak ISWP of the large current becomes longer by the period T2, so that it is sufficient to slowly shift to the sufficient conduction state. That is, in the present embodiment, the configuration of the control circuit 16 can be made smaller and less expensive than the control circuit 10 of the above embodiment.

Next, an embodiment of the third means of the present invention will be described with reference to FIG. Reference numerals 18 and 19 denote a resonance coil and a resonance capacitor, which are the same as those in the above embodiments. Reference numerals 20 and 21 denote reverse blocking switching elements and reverse conduction switching elements that drive the resonance coil 18 and the resonance capacitor 19. 22 is a reverse blocking switching element 20
A control circuit for controlling the reverse conducting switching element 21;

The reverse blocking switching element 20 is connected to the DC current source 23, the resonance capacitor 19 and the reverse conduction switching element 21 are connected to the DC current source 23 in series, and the resonance coil 18 is inserted into the resonance capacitor 19 in series. ing. The outputs VD1 and VD2 of the control circuit 22 correspond to the gates G of the reverse blocking switching element 20 and the reverse conduction switching element 21.
1 · G2 to control the conduction and cutoff of these. In this embodiment, the reverse blocking switching element 20 and the reverse conduction switching element 21 are arranged so that the output current IS of the DC current source 22 becomes the forward currents ISW1 and ISW2.

The operation of this embodiment will be described below. In the present embodiment, the reverse blocking switching element 20 and the reverse conduction switching element 21 are periodically turned on / off by the control circuit 22.
An AC current is supplied to the resonance coil 18 in a cut-off state, and a load placed on the resonance coil 18 is induction-heated by the generated high-frequency magnetic field.

The operation will be described below with reference to FIG.
VSW1 and ISW1 are reverse blocking switching elements 20 respectively.
VSW2 · ISW2 indicates the voltage / current of the reverse conducting switching element 21 and IL indicates the current of the resonance coil 18. The periods T1 and T2 indicate periods in which the reverse blocking switching element 20 and the reverse conduction switching element 21 are cut off.

In the period from t0 to t1, the reverse blocking switching element 20 and the reverse conducting switching element 21 are conducting by the control circuit 22, and the resonance coil 18, the resonance capacitor 19, the reverse blocking switching element 20, and the reverse conducting switching element 21 are provided. The resonance current ISW2 flows in the loop. ISW1 (= IS-ISW2) rises in a resonance arc, temporarily passes through the power supply current IS, then rises and falls, and
At time t1 when W2 becomes zero, the current reaches IS again. Control circuit 22
Turns off the bipolar transistor forming the reverse conducting switching element 21 before the time t1 and during the period when ISW2 is negative. Therefore, at time t1, the reverse conducting switching element 21 is naturally shut off, and VSW2 rises. In this state, since the resonance capacitor 19 is shut off, the period t1
The voltage is maintained for t2. That is, the voltage of the reverse conducting switching element 21 is maintained at a constant value. When the reverse conducting switching element 21 is turned on at the time t2, the resonance state returns to the same state as the period t0 to t1, and the ISW1 falls to zero as shown in the period t2 to t3. When ISW1 reaches zero, that is, at time t3, the reverse blocking switching element 20 is naturally shut off, and VSW1 is generated. In the period t3 to t4, the resonance capacitor 19 is charged with the constant current IS, and VSW1 increases. Next, after time t3, that is, V
During the negative period of SW1, the bipolar transistor forming the reverse blocking switching element 20 is turned on. Thus, the blocking of the reverse blocking switching element 20 is maintained during the period t3 to t4. At time t4, the reverse blocking switching element 20 is turned on by the control circuit 22. When the reverse blocking switching element 20 conducts, the state of the high-frequency inverter returns to the state at time t0, and oscillation continues.

As described above, the high-frequency inverter of the present embodiment can independently control the frequency and the power similarly to the embodiment of the first means of the present invention, and the zero-current switching of the switching element is maintained. Therefore, the duty of the switching element is small and the generated noise is small.

In the embodiment of the first means of the present invention,
The voltage VS of the DC current source 11 does not become negative because the first reverse conducting switching element 8 is connected.
This means that, in principle, the instantaneous power Pi supplied from the DC current source 11 is always positive. Since IS ≧ 0 and VS ≧ 0, Pi = IS × VS ≧
This is because it becomes 0. As can be clearly seen, in a high-frequency inverter in which instantaneous power is not regenerated in this way, when no power is supplied from the power supply and no load is supplied, the supplied power continues to be stored in the inverter, As a result, the system diverges and becomes unstable. In this respect, in this embodiment, since the switching element 20 connected to the DC current source 23 is of the reverse blocking type,
There is a period in which VS becomes negative. Therefore, it operates stably even when there is no load. Specifically, when there is no load, the operation can be performed such that the positive and negative average values of VSW1 become equal, the average value becomes zero, and the power supplied from the DC current source 23 becomes zero. That is, the present embodiment realizes a more reliable high-frequency inverter. Next, an embodiment of the fourth means of the present invention will be described with reference to FIG. 24 ・ 25 ・ 26 ・ 27 ・
Reference numerals 27, 28, and 29 denote a resonance coil, a resonance capacitor, a reverse blocking switching element, a reverse conduction switching element, a control circuit, and a DC current source similar to those of the third embodiment of the present invention. A reverse blocking switching element 26 is connected to a DC current source 29, and a resonance capacitor 25 and a reverse conduction switching element 27 are connected in series.
, A resonance coil 24 is inserted in series. Control circuit 28
The outputs VD1 and VD2 are connected to the gates G1 and G2 of the reverse blocking switching element 26 and the reverse conduction switching element 27, and control the conduction and cutoff thereof. In the present embodiment, the reverse blocking switching element 26 is arranged in the direction of the output current IS of the DC current source 29 in the direction of the forward current ISW1, and the reverse conduction switching element 29 is arranged in the direction of the reverse current -ISW2.

The operation of the present embodiment will be described below with reference to FIG. VSW1 and ISW1 represent the voltage and current of the reverse blocking switching element 26, VSW2 and ISW2 represent the voltage and current of the reverse conduction switching element 27, and IL represents the current of the resonance coil 24, respectively. In addition, period T1, T2
Indicates a period in which the reverse blocking switching element 26 and the reverse conduction switching element 27 are cut off.

The control circuit 28 conducts the reverse blocking switching element 26 and the reverse conducting switching element 27 during the period t0 to t1, and the resonance coil 24, the resonance capacitor 25, the reverse blocking switching element 26, and the reverse conducting switching element. A resonance current ISW2 flows in a loop of 27. When the resonance current ISW2 flows, ISW1 (= IS-ISW2) gradually increases and reaches IS at time t1 when ISW2 becomes zero. Next, before time t1, while ISW2 is negative, the bipolar transistor forming the reverse conducting switching element 27 is shut off. Thus, at time t1, the reverse conducting switching element 27 is naturally shut off, and VSW2 rises. In this period, since the resonance capacitor 25 is shut off, the period t
The voltage is maintained from 1 to t2. That is, the voltage of the reverse conduction switching element 27 is maintained at a constant value. Time t
When the control circuit 16 conducts the reverse conduction switching element 27 in 2, the resonance state is the same as the period t 0 to t 1, and
Rises and falls in a resonance arc and reaches zero again at time t3. When ISW1 reaches zero, at time t3, the reverse blocking switching element 26 is naturally turned off, and VSW1 is generated. Next, during the period t3 to t4, the resonance capacitor 25 is charged with the constant current IS, so that VSW1 increases. Further, after time t3, the control circuit 28 shuts off the bipolar transistor constituting the reverse blocking switching element 26 during the period when VSW1 is negative. When the bipolar transistor is cut off, the blocking of the reverse blocking switching element 26 is maintained during the period t3 to t4. When the reverse blocking switching element 26 is turned on at time t4, the state of the high-frequency inverter returns to the state at time t0, and oscillation continues.

The high-frequency inverter according to the present embodiment can independently control the frequency and the power, as in the third embodiment of the present invention, and the zero-current switching of the switching element is maintained. Therefore, the duty of the switching element is small, and the generated noise is small. In addition, stable operation can be performed even when there is no load. In addition, in the high-frequency inverter of this embodiment, the ISW1 of FIG.
As is clear from the period t0 to t3, the peak I of the large current
Since the time required to reach SWP is long, the reverse blocking switching element 26 only needs to be slowly shifted to a sufficiently conductive state, and the control circuit 28 can be made small and inexpensive.

In each of the above embodiments, the resonance coil is inserted in series with the resonance capacitor. However, in the first and second embodiments of the present invention, the resonance coil is inserted in series with the first reverse conducting switching element. Alternatively, the first and second resonance coils may be inserted into the resonance capacitor and the first reverse conducting switching element, respectively. Further, in the embodiments of the third and fourth means of the present invention, the first and second resonance coils may be connected in series to the reverse blocking switching element, and may be connected to both the resonance capacitor and the reverse blocking switching element. May be inserted respectively.

FIG. 10 shows a second embodiment of the first means of the present invention, in which a first resonance coil 32a and a second resonance coil 32b are provided in both a resonance capacitor 30 and a first reverse conducting switching element 31. Each is inserted. 33 is a second reverse conducting switching element, 34 is a control circuit, and 35 is a DC current source.

In each of the above embodiments, the switching element is constituted by an npn bipolar transistor and a diode.
np bipolar transistor, MOSFET, IGBT
A SIT / SI thyristor / thyristor may be used, and a series diode constituting a reverse blocking switching element may be inserted into the emitter instead of being inserted into the collector as in the embodiment. Further, the reverse blocking switching element may be constituted by one switching element having a reverse blocking function, such as a reverse blocking thyristor and an IGBT having a high reverse withstand voltage. The reverse conducting switching element may be a reverse conducting thyristor, a reverse conducting IGBT MOSFET. For example, a single switching element having a reverse conduction function may be used. The DC current source used in each of the above embodiments may be formed by connecting a DC reactor to a DC voltage source obtained by rectifying an AC power supply, or may be a constant current source formed by a semiconductor circuit. Also,
A pulsating or pulsed DC current source may be used.

Further, in each of the above embodiments, the high-frequency inverter for induction heating has been described. However, the present invention is applicable to a high-frequency inverter for various uses such as for fluorescent lamp lighting, ultrasonic generation, magnetron drive power supply, and switching power supply. Can be applied.

[0042]

According to a first aspect of the present invention, there is provided a DC current source,
A resonance coil and a resonance capacitor connected in series to the DC current source; a first reverse conducting switching element for driving the resonance coil and the resonance capacitor; and the series connection
A second reverse conduction switching element connected in series to the resonance coil and the resonance capacitor, and a control circuit for driving the first and second reverse conduction switching elements, wherein the first and second reverse conduction switching The element is arranged in a direction in which the output current of the DC current source becomes a forward current, and the second
The reverse conducting switching element has zero forward current.
Is a high-frequency inverter that is controlled to be turned off when negative, so that power and operating frequency can be controlled independently.

The second means of the present invention comprises a DC current source, a resonance coil and a resonance capacitor connected in series to the DC current source, a first reverse conducting switching element for driving the resonance coil and the resonance capacitor, and A second reverse conduction switching element, and a control circuit for driving the first and second reverse conduction switching elements, wherein the first reverse conduction switching element has a direction in which the output current of the DC current source becomes a forward current. Since the second reverse conducting switching element is arranged as a high-frequency inverter arranged in a direction in which the output current of the DC current source becomes a reverse current, the rising time of the forward current of the first reverse conducting switching element becomes longer, The driving of the gate is facilitated, and the control circuit can be made smaller and less expensive than the first means of the present invention. Therefore, an inexpensive high-frequency inverter can be realized.

According to a third means of [0044] the present invention, a direct current source, and resonant coil and the resonant capacitor connected in series to the direct current source, the reverse blocking switching element and the driving the resonant capacitor and the resonant coil Connected in series
A reverse conduction switching element connected in series to the resonance coil and the resonance capacitor, and a control circuit for driving the reverse blocking switching element and the reverse conduction switching element, such that the output current of the DC current source becomes a forward current. The reverse blocking switching element and the reverse conduction switching element are arranged, and the reverse conduction switching element is arranged in that order.
Control to turn off when the directional current is zero or negative.
The high frequency inverter can be a device that operates stably even when there is no load.

The fourth means of the present invention comprises a DC current source, a resonance coil and a resonance capacitor connected in series to the DC current source, a reverse blocking switching element for driving the resonance coil and the resonance capacitor, and a reverse conduction. A switching element; and a control circuit for driving the reverse blocking switching element and the reverse conducting switching element. The reverse blocking switching element is arranged in a direction in which the output current of the DC current source becomes a forward current. As a high-frequency inverter arranged in the direction in which the output current of the source becomes the reverse current, the rise time of the forward current of the reverse conducting switching element becomes longer, the driving of the gate becomes easier, and the effect of the third means of the present invention is obtained. In addition, the control circuit can be small and inexpensive.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a high-frequency inverter according to an embodiment of a first means of the present invention.

FIG. 2 is a waveform diagram illustrating the operation of the high-frequency inverter.

FIG. 3 is an operation characteristic diagram illustrating the operation of the high-frequency inverter.

FIG. 4 is a circuit diagram of a high-frequency inverter according to an embodiment of the second means of the present invention.

FIG. 5 is a waveform chart for explaining the operation of the high-frequency inverter.

FIG. 6 is a circuit diagram of a high-frequency inverter according to a third embodiment of the present invention;

FIG. 7 is a waveform chart for explaining the operation of the high-frequency inverter.

FIG. 8 is a circuit diagram of a high-frequency inverter according to a fourth embodiment of the present invention;

FIG. 9 is a waveform chart for explaining the operation of the high-frequency inverter.

FIG. 10 is a circuit diagram of a high-frequency inverter according to a second embodiment of the first means of the present invention.

FIG. 11 is a circuit diagram of a conventional high-frequency inverter.

FIG. 12 is a waveform chart illustrating the operation of the high-frequency inverter.

[Explanation of symbols]

 6, 12, 18, 24, 30 Resonant coil 7, 13, 19, 25 Resonant capacitor 8, 14, 31 First reverse conducting switching element 9, 15, 33 Second reverse conducting switching element 10, 16, 22, 28/34 Control circuit 11/17/23/29/35 DC current source 20/26 Reverse blocking switching element 21/27 Reverse conduction switching element 32a First resonance coil 32b Second resonance coil

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-6770 (JP, A) JP-A-1-3111587 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05B 6/12 H02M 7/48

Claims (4)

(57) [Claims] 1. A DC current source, a resonance coil and a resonance capacitor connected in series to the DC current source, a first reverse conducting switching element driving the resonance coil and the resonance capacitor, and the resonance coil connected in series And resonance
A second reverse conducting switching element connected in series to a capacitor , comprising a control circuit for driving the first and second reverse conducting switching elements, wherein the first and second reverse conducting switching elements are connected to a DC current source. An output current is arranged in a forward current direction, and the second reverse conducting switching element is arranged.
Switch off when its forward current is zero or negative
High-frequency inverter controlled as follows . 2. A DC current source, a resonance coil and a resonance capacitor connected in series to the DC current source, and a first reverse conduction switching element and a second reverse conduction switching element for driving the resonance coil and the resonance capacitor. And a control circuit for driving the first and second reverse conducting switching elements, wherein the first reverse conducting switching element is arranged in a direction in which the output current of the DC current source becomes a forward current, and the second The reverse conducting switching element is a high-frequency inverter arranged in a direction in which the output current of the DC current source becomes a reverse current. 3. A DC current source, a resonance coil and a resonance capacitor connected in series to the DC current source, a reverse blocking switching element for driving the resonance coil and the resonance capacitor, and a resonance capacitor connected to the series connected resonance coil.
A reverse conduction switching element connected in series to a sensor, and a control circuit for driving the reverse conduction switching element and the reverse conduction switching element, wherein the reverse conduction switching element is arranged so that the output current of the DC current source becomes a forward current. with arranging the reverse conducting switching element, the reverse conducting
The switching element has a forward current of zero or negative.
High frequency inverter controlled to turn off when 4. A DC current source, a resonance coil and a resonance capacitor connected in series to the DC current source, a reverse blocking switching element and a reverse conduction switching element for driving the resonance coil and the resonance capacitor, and the reverse blocking switching. A reverse blocking switching element is arranged in a direction in which the output current of the DC current source becomes a forward current, and a reverse conduction switching element is arranged such that the output current of the DC current source is a reverse current. High-frequency inverter arranged in the direction of