JPH05326127A - High frequency inverter - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide a high-frequency inverter capable of easily independently controlling power and frequency. A DC current source 11, a resonance coil 6 and a resonance capacitor 7 connected in series to the DC current source, a first reverse conduction switching element 8 and a second reverse conduction which drive the resonance coil and the resonance capacitor. A switching element 9 and a control circuit 10 for driving the first and second reverse conducting switching elements are provided, and the first and second reverse conducting switching elements are arranged so that the output current of the DC current source becomes a forward current. I placed it.

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 in an induction heating cooker used in general 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 load handling range by parallel use such as multiple ports and reduce noise.

A conventional high frequency inverter will be described below with reference to FIGS. 11 and 12. In the figure, 1 is a resonance capacitor, and 2 is a resonance coil connected in series to the resonance capacitor 1. A reverse conduction switching element 3 is composed of a diode connected in antiparallel to a bipolar transistor. Reference numeral 4 denotes a control circuit, which controls conduction / interruption of the reverse conduction switching element 3. Reference numeral 5 is a direct current source normally composed of a direct current voltage source, a direct current reactor and the like, and supplies electric power to the circuit of the resonance capacitor 1, the resonance coil 2 and the reverse conduction switching element 3. The resonance coil 2 also doubles as a heating coil, and inductively heats a load such as a pan (not shown).

In the conventional high frequency inverter configured as described above, the reverse conduction switching element 3 is periodically conducted.
By cutting off, an alternating current is passed through the resonance coil 2, and the load is induction-heated by the high frequency AC magnetic field generated by 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, and V _SW and I _SW respectively show voltage and current of the reverse conducting switching element 3. The period T ₁ indicates a period in which the reverse conduction switching element 3 is cut off, and the input power of the high frequency inverter can be controlled by changing the period.

[0006]

However, in the above-mentioned conventional structure, there is a problem that when the period T ₁ is changed, the oscillation cycle T ₀ is inevitably changed. That is,
In the conventional configuration, as shown by V _SW in FIG. 12, in order to perform the zero current switching in which the duty of the switching element is small, the period t _{0 to} t ₁ is the resonance capacitor 1 and the resonance coil 2.
It is fixed at the resonance period of. Therefore, when the period T ₁ is changed to control the input power, the oscillation cycle T ₀ changes in conjunction.

The fact that the input power and the operating frequency cannot be controlled independently poses the following problems in industrial and consumer applications. (1) When using an induction heating device in parallel to heat a large number of induction heating cookers or large loads, if the induction heating frequencies of adjacent resonance coils are different, the difference frequency falls within the audible range. Sound as interference noise. (2) As is well known, there is an optimum heating frequency band depending on the heating application and load, such as a high frequency for a small load or a non-magnetic load and a low frequency for a large load or a magnetic load. Therefore, the target input power cannot be obtained in this optimum frequency band. For this reason, it is unavoidable to narrow the load corresponding range or perform inefficient heating. (3) Since the operating frequency range is wide, the noise filter cannot be fully covered, and the noise leaking to the power source becomes large. Further, when the peripheral device is disturbed at a specific frequency such as the modulation frequency of the infrared remote controller of the television, it is difficult to avoid the frequency and use.

SUMMARY OF THE INVENTION The first object of the present invention is to provide a high frequency inverter having a simple structure and capable of easily independently controlling electric power and frequency. In addition, the second to achieve the first purpose
The second, third, and fourth purposes are to provide the third and fourth means.

[0009]

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

A second means of the present invention for achieving the second object is to drive a direct current source, a resonance coil and a resonance capacitor connected in series to the direct current source, and 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. The second reverse conduction switching element is a high-frequency inverter that is arranged in a direction in which the output current becomes a forward current and the second reverse conduction switching element is 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 to provide a direct current source, a resonance coil and a resonance capacitor connected in series with the direct current source, and the resonance coil and the resonance capacitor. A reverse blocking switching element for driving and a reverse conducting switching element; and a control circuit for driving the reverse blocking switching element and the reverse conducting switching element, the reverse blocking switching element in a direction in which an output current of the direct current source becomes a forward current And a high frequency inverter in which the reverse conduction switching element is arranged.

A fourth means of the present invention for achieving the fourth object is to provide a direct current source, a resonance coil and a resonance capacitor connected in series with the direct current source, and the resonance coil and the resonance capacitor. A reverse blocking switching element for driving and a reverse conducting switching element, and a control circuit for driving the reverse blocking switching element and the reverse conducting switching element, wherein 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 conduction switching element is a high frequency inverter arranged in a direction in which the output current of the direct current source becomes a reverse current.

[0013]

According to the first means of the present invention, by changing the conduction ratio of the switching element during one cycle, the electric power is changed in the state where the operation cycle is constant, and the electric power is kept in the state where the power is kept constant. , Acts to change the operation cycle. Therefore, it is possible to provide a high frequency inverter capable of independently controlling electric power and operating frequency.

According to the second means of the present invention, since the rise time of the forward current of the first reverse conducting switching element is long, the driving of the gate is facilitated and the second 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.

According to the third means of the present invention, since the switching element is of the reverse blocking type, it operates stably even under no load.

In the fourth means of the present invention, since the rise time of the forward current of the reverse conduction switching element becomes long,
The gate can be easily driven, and the control circuit can be made compact and inexpensive as compared with 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, 6 and 7 are resonance coils and resonance capacitors connected in series.
The resonance coil 6 induction-heats a pan (not shown) placed on the resonance coil 6. Reference numerals 8 and 9 denote a first reverse conducting switching element and a second reverse conducting switching element for driving the resonance coil 6 and the resonance capacitor 7, which are constituted by bipolar transistors and antiparallel diodes in this embodiment. 10 is the first and second reverse conduction switching elements 8
A control circuit for driving 9. Reference numeral 11 is a DC current source composed of a DC voltage source and a DC reactor.

The outputs V _D1 and V _D2 of the control circuit 10 are connected to the gates G ₁ and G ₂ of the first reverse conducting switching element 8 and the second reverse conducting switching element 9. Thus
The control circuit 10 controls conduction and interruption of the first reverse conduction switching element 8 and the second reverse conduction switching element 9. At this time, in this embodiment, the first reverse conducting switching element 8 and the second reverse conducting switching element 9 are arranged in the direction in which the output current I _S of the DC current source 11 becomes the forward currents I _SW1 and I _SW2. There is. Since the high frequency inverter for induction heating is taken up in this embodiment, 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 conducted / interrupted by the control circuit 10, and a high frequency alternating current is passed through the resonance coil 6 to generate a high frequency. A magnetic field is used to inductively heat a load such as a pan. The operation will be described below with reference to FIG. Each V _{SW1-I SW1} voltage and current of the first reverse conducting switching device 8, the voltage and current of each V _{SW2-I SW2} a second reverse conducting switching device 9, I _L is the current of the resonant coil 6 Is shown. Further, the periods T ₁ and T ₂ indicate periods in which the first reverse conducting switching element 8 and the second reverse conducting switching element 9 are cut off, respectively.

In the period t _{0 to} t ₁ , the first reverse conducting switching element 8 and the second reverse conducting switching element 9 are conducted by the control circuit 10, and the resonance coil 6, the resonance capacitor 7 and the first reverse conduction switching element 9 are in conduction. In the loop of the conduction switching element 8 and the second reverse conduction switching element 9, the resonance current is I
It is flowing like _SW2 . When the resonance current I _SW2 flows,
I _SW1 (= I _S −I _SW2 ) rises in an arc of resonance,
After passing the power supply current I _S once, it rises and falls and reaches I _S again at time t ₁ when I _SW2 becomes zero. The control circuit 10
Before the time t1, the bipolar transistor forming the second reverse conduction switching element 9 is cut off during a negative period of I _SW2 . Then, at time t ₁ , the second reverse conduction switching element 9 is naturally shut off and V _SW2 rises. Since the resonance capacitor 7 is cut off during this period, the voltage during the period t _{1 to} t ₂ is maintained. That is, the voltage of the second reverse conduction switching element 9 is maintained at a constant value.
Further, when the control circuit 10 turns on the second reverse conducting switching element 9 at time t ₂ , the same resonance state as during the period t _{0 to} t ₁ is reached, and I _SW1 draws an arc of resonance to rise and fall to zero. After passing through, a negative resonance arc is drawn and reaches zero again at time t3. Next, before the time t ₃ , that is, during the period when I _SW1 is negative, the bipolar transistor forming the first reverse conduction switching element 8 is cut off. Therefore, at time t ₃ , the first reverse conduction switching element 8 is naturally shut off and V
_SW1 starts up. Further, in the period t _{3 to} t ₄ , the resonance capacitor 13 is charged with the constant current I _S , so that V _SW1 increases. When the control circuit 10 turns on the first reverse conduction switching element 8 at time t ₄ , the state of the high frequency inverter returns to the state at time t ₀ and oscillation is continued.

As described above, in the high frequency inverter of this embodiment, by changing the cutoff time T ₂ of the second reverse conducting switching element 9, the first reverse conducting switching element is maintained in the state where the zero current switching is maintained. It is possible to freely change the conduction period t _{0 to} t ₃ of FIG.

The power P of the high frequency inverter is I
And _S, the product of the average value or average value of V _SW1 of V _S. The high frequency inverter of this embodiment has the following (1)
It is understood that the frequency and the power can be variably controlled independently due to the reason (2). (1) As shown in FIG. 3 (a), the control circuit 10 increases the cut-off period T ₁ of the first reverse conduction switching element 8 and at the same time, makes the second reverse circuit so that T ₀ is maintained constant. The interruption period T ₂ of the conduction switching element 9 is reduced. Therefore, in addition to increasing V _SW1 , T ₁ /
Since T ₀ increases, the average value of V _SW1 also increases and the power P increases. That is, the high frequency inverter of this embodiment can freely variably control the electric power while keeping the operating frequency constant. (2) When the operation cycle T ₀ is shortened, T ₁ / T ₀ increases, so that the power P increases. That is, the characteristic as shown in FIG. 3B is obtained. In FIG. 3B, for example, operating point A ₁
In A ₂ · A ₃ , the same electric power P ₁ can be obtained in different operation cycles a ₁ , a _2, and a ₃ . Therefore, the frequency can be freely controlled while the power is kept constant.

Further, since the zero current switching of the switching element is maintained, the duty of the switching element is small and the generated noise is also small.

Next, an embodiment of the second means of the present invention will be described with reference to FIG. 12/13/14/15
16 and 17 are a resonance coil, a resonance capacitor, a first reverse conduction switching element, a second reverse conduction switching element, a control circuit, and a direct current source, which are the same as those in the above embodiment. The first reverse conduction switching element 14 is connected to the direct current source 17, the resonance capacitor 13 and the second reverse conduction switching element 15 are further connected in series to the direct current source 17, and the resonance coil 12 is connected to the resonance capacitor 13. Inserted in series. The outputs V _D1 and V _D2 of the control circuit 16 are connected to the gates G ₁ and G ₂ of the first reverse conduction switching element 14 and the second reverse conduction switching element 15, and control conduction and interruption of these. ing. In the present embodiment, the first reverse conducting switching element 14 is arranged in the 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 conduction switching element 15 is arranged in the direction.

The operation of this embodiment will be described below with reference to FIG. V _SW1 and I _SW1 are the voltage and current of the first reverse conducting switching element 14, V _SW2 and I _SW2 are the voltage and current of the second reverse conducting switching element 15, and I _L is the resonance coil 12. It shows the current. Further, the periods T ₁ and T ₂ indicate periods in which the first reverse conduction switching element 14 and the second reverse conduction switching element 15 are cut off, respectively. In the period t _{0 to} t ₁ , the control circuit 16 causes the first reverse conduction switching element 14 and the second reverse conduction switching element 15 to be in conduction, and thus the resonance coil 12, the resonance capacitor 13, and the first reverse conduction switching element. 14. Second reverse conduction switching element 15
The resonance current flows like I _{SW2 in} the loop. I _SW1 (=
I _S −I _{S W2} ) gradually increases and reaches I _S at time t ₁ when I _SW2 becomes zero. The control circuit 16 outputs I before time t1.
Second reverse conduction switching element 1 during the negative period of _SW2
The bipolar transistor constituting 5 is cut off. By doing so, at time t ₁ , the second reverse conducting switching element 15
Is naturally shut off and V _SW2 rises. Since the resonance capacitor 13 is cut off during this period, the period t _{1 to} t ₂
The voltage during is maintained. That is, the voltage of the second reverse conduction switching element 15 is maintained at a constant value. Also the control circuit 16 is conductive the second reverse conducting switching element 15 at time t _2, the become a same resonance state in the period t ₀ ~t _1, I _SW1 is rise and fall in an arc of resonance, zero After passing through, a negative resonance arc is drawn and reaches zero again at time t3. Then, before the time t ₃ , that is, before the negative period of I _SW1 , the bipolar transistor forming the first reverse conduction switching element 14 is cut off. Therefore, at time t ₃ , the first reverse conduction switching element 14 is naturally shut off,
V _SW1 rises. Further, in the period t _{3 to} t ₄ , the resonance capacitor 13 is charged with the constant current I _S , so that V _SW1 increases. When the control circuit 16 conducts the first reverse conduction switching element 14 at time t ₄ , the state of the high frequency inverter returns to the state at time t ₀ and oscillation is continued.

As described above, the high frequency inverter of this embodiment can control the frequency and the power independently as in the case of the above embodiment, and the zero current switching of the switching element is maintained. Is small and the generated noise is also small.

In the embodiment of the first means of the present invention, I _SW1 rapidly reaches the peak I _SWP in the period t _{0 to} t ₁ . Therefore, the first reverse conduction switching element 8 needs to be rapidly transitioned to a sufficient conduction state. For example, in the case of a bipolar transistor, a large forward base current has to flow. Therefore, the control circuit 10 becomes large and expensive. In this respect, in the high frequency inverter of the present embodiment, the period t ₀ to I _SW1 of FIG.
As is clear from t _3, the time until the peak of the large current I _SWP is reached is increased by the period T _2, so it is sufficient to slowly shift to a sufficiently conductive state. That is, in this embodiment, the structure of the control circuit 16 can be made smaller and cheaper 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 are resonance coils and resonance capacitors, which are the same as those in the above-described embodiments. Reference numerals 20 and 21 are 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 that controls the reverse conduction switching element 21.

A reverse blocking switching element 20 is connected to the direct current source 23, a resonance capacitor 19 and a reverse conduction switching element 21 are connected in series to the direct current source 23, and a resonance coil 18 is inserted in series to the resonance capacitor 19. ing. The outputs V _D1 and V _D2 of the control circuit 22 are the gates G of the reverse blocking switching element 20 and the reverse conduction switching element 21.
_It is connected to ₁ and G ₂ and controls conduction and interruption of these. In this embodiment, the reverse blocking switching element 20 and the reverse conduction switching element 21 are arranged in the direction in which the output current I _S of the DC current source 22 becomes the forward currents I _SW1 and I _SW2 .

The operation of this embodiment will be described below. In this embodiment, the control circuit 22 causes the reverse blocking switching element 20 and the reverse conducting switching element 21 to conduct periodically.
An alternating current is made to flow through the resonance coil 18 after being cut off, and a high-frequency magnetic field generated is used to inductively heat a load placed on the resonance coil 18.

The operation will be described below with reference to FIG.
V _SW1 and I _SW1 are reverse blocking switching elements 20 respectively.
, V _SW2 · I _SW2 indicates the voltage / current of the reverse conduction switching element 21, and I _L indicates the current of the resonance coil 18. Further, the periods T ₁ and T ₂ indicate periods in which the reverse blocking switching element 20 and the reverse conduction switching element 21 are cut off, respectively.

Period t₀~ T₁Then, by the control circuit 22
The reverse blocking switching element 20 and the reverse conduction switch
The resonance element 18 is in conduction, and the resonance coil 18
Capacitor 19, reverse blocking switching element 20, reverse conduction switch
In the loop of the switching element 21, the resonance current I_SW2Flows
It I_SW1(= I_S-I_SW2) Goes up, drawing an arc of resonance
And then once the power supply current I_SAfter passing through, go up and down I
_SW2Time t when is zero₁And I again_SReach Control circuit 2
2 is time t₁In front of I_SW2Reverse conduction switch during a negative period.
The bipolar transistor that forms the touching element 21
Cut off. Therefore, time t₁And the reverse conduction switching element
Child 21 is naturally shut off, V_SW2Stands up. This state
Since the resonance capacitor 19 is cut off, the period t
₁~ T₂During that time its voltage is maintained. That is, reverse conduction switch
The voltage of the switching element 21 is maintained at a constant value. Again time
Tick t₂When the reverse conduction switching element 21 is turned on,
Interval t₀~ T ₁Return to the same resonance state as in₂~ T₃Shown in
I like_SW1Drops to zero. I_SW1Reaches zero
That is, time t₃Then, the reverse blocking switching element 20
Naturally cut off, V_SW1Occurs. Period t₃~ T_Fourso
Is a constant current I_SIs charged with
And V_SW1Will increase. Then at time t₃After, ie V
_SW1Reverse blocking switching element 20 during the negative period of
The formed bipolar transistor is turned on. Thus
Interval t₃~ T_FourWhile the reverse blocking switching element 20 is cut off,
Maintained. Also at time t_FourThen, the control circuit 22 reverses
The blocking switching element 20 is turned on. Reverse blocking switch
When the switching element 20 is conductive, the state of the high frequency inverter is
Time t₀The state returns to and the oscillation continues.

As described above, the high frequency inverter of this embodiment can control the frequency and the power independently as in 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 also small.

In the embodiment of the first means of the present invention,
Voltage V _S of the DC current source 11, since the first reverse conducting switching device 8 is connected, it does not become negative.
This means that, in principle, the instantaneous power P _i supplied from the DC current source 11 is always positive. Since I _S ≧ 0 and V _S ≧ 0, P _i = I _S × V _S ≧
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 the power supplied from the power supply does not go out, the supplied power continues to be stored in the inverter, As a result, the system diverges and becomes unstable. In this regard, in this embodiment, since the switching element 20 connected to the DC current source 23 is of the reverse blocking type, V
There is a period during which _SW1 or V _S becomes negative. Therefore, it operates stably even under no load. Specifically, when there is no load, it is possible to operate so that the positive and negative average values of V _SW1 become equal and the average value becomes zero, and the electric power supplied from the direct current source 23 becomes zero. That is, this embodiment realizes a high-reliability 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
Numerals 27, 28, and 29 are a resonance coil, a resonance capacitor, a reverse blocking switching element, a reverse conduction switching element, a control circuit, and a DC current source, which are the same as those in the embodiment of the third means of the present invention. The reverse blocking switching element 26 is connected to the DC current source 29, and the resonance capacitor 25 and the reverse conduction switching element 27 are connected in series.
5, the resonance coil 24 is inserted in series. Control circuit 2
The outputs V _D1 and V _D2 of 8 are connected to the gates G ₁ and G ₂ of the reverse blocking switching element 26 and the reverse conduction switching element 27, respectively, and control conduction and interruption of these. In this embodiment, the output current I _S of the DC current source 29 is the forward current I _SW1.
The reverse blocking switching element 26 is arranged in the direction that becomes, and the reverse conduction switching element 29 is arranged in the direction that becomes the reverse current −I _SW2.
Are arranged.

The operation of this embodiment will be described below with reference to FIG. V _{SW1-I SW1} is a voltage and current of the reverse blocking switching element 26, respectively, the voltage and current of each V _{SW2-I SW2} is reverse conducting switching device 27, I _L represents the current in the resonant coil 24. Also period T ₁ · T
Reference numeral ₂ denotes a period in which the reverse blocking switching element 26 and the reverse conduction switching element 27 are cut off, respectively.

The control circuit 28 conducts the reverse blocking switching element 26 and the reverse conducting switching element 27 during the period t _{0 to} t ₁ , and the resonance coil 24, the resonance capacitor 25, the reverse blocking switching element 26 and the reverse conducting state. The resonance current I _SW2 flows in the loop of the switching element 27. When the resonance current I _SW2 flows, I _SW1 (= I _S −I _SW2 ) gradually increases and reaches I _S at time t ₁ when I _SW2 becomes zero. Then, before the time t ₁ , the bipolar transistor forming the reverse conduction switching element 27 is turned off during the period when I _{SW 2} is negative. Thus, at time t ₁ , the reverse conduction switching element 27 is naturally shut off and V _SW2 rises. Since the resonance capacitor 25 is cut off during this period, the period t
The voltage is maintained for _{1 to} t ₂ . 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 the state of 2, the resonance state is the same as that of the period t _{0 to} t _1, and I _SW1
Draws an arc of resonance, rises and falls, and reaches zero again at time t ₃ . When I _SW1 reaches zero, the reverse blocking switching element 26 is naturally shut off at time t ₃ and V _SW1 is generated. Then, in the period t ₃ ~t _4, the V _SW1 since the resonance capacitor 25 is charged with a constant current I _S increases. Further, the control circuit 28 cuts off the bipolar transistor forming the reverse blocking switching element 26 during a negative period of V _SW1 after the time t ₃ . When the bipolar transistor is cut off, the reverse blocking switching element 26 is kept cut off during the period t3 to t4. When the reverse blocking switching element 26 is turned on at time t ₄ , the state of the high frequency inverter returns to the state at time t ₀ and oscillation continues.

In the high frequency inverter of the present embodiment described above, the frequency and the power can be controlled independently as in the case of the third 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 also small. Further, it can be operated stably even under no load. In addition, in the high frequency inverter of this embodiment, I _{SW1 of} FIG.
As is clear from the period t _{0 to} t ₃ ,
Since it takes a long time to reach _SWP, it suffices to slowly shift the reverse blocking switching element 26 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 embodiments of the first and second means of the present invention, the resonance coil is inserted in series with the first reverse conduction switching element. Alternatively, the first and second resonant coils may be inserted in the resonant capacitor and the first reverse conducting switching element, respectively. In the embodiments of the third and fourth means of the present invention, the reverse blocking switching element may be connected in series, and both the resonance capacitor and the reverse blocking switching element may have the first and second resonance coils. May be inserted respectively.

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

Further, in each of the above-mentioned embodiments, the switching element is composed of the npn bipolar transistor and the diode.
np bipolar transistor, MOSFET, IGBT
SIT, SI thyristor, thyristor, etc. may be used, and the series diode forming the reverse blocking switching element may be inserted in the emitter instead of the collector as in the embodiment. Further, the reverse blocking switching element may be composed of a single switching element having a reverse blocking function such as a reverse blocking thyristor or an IGBT having a high reverse breakdown voltage, and the reverse conducting switching element may be a reverse conducting thyristor / reverse conducting IGBT / MOSFET. It may be configured by one switching element having a reverse conduction function. 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 source, or may be a constant current source using a semiconductor circuit. Also,
A pulsating current or a pulsed direct current source may be used.

Further, although each of the above-described embodiments has been described as a high frequency inverter for induction heating, the present invention is applicable to a high frequency inverter for various purposes such as lighting of fluorescent lamps, generation of ultrasonic waves, magnetron driving power source, switching power source and the like. Can be applied.

[0042]

The first means of the present invention is a direct current source,
A resonance coil and a resonance capacitor connected in series to the DC current source, a first reverse conduction switching element and a second reverse conduction switching element which drive the resonance coil and the resonance capacitor, and the first and second reverse conduction switching elements. As a high-frequency inverter having a control circuit for driving a conduction switching element and arranging the first and second reverse conduction switching elements in a direction in which the output current of a direct current source becomes a forward current, the power and the operating frequency are independently controlled. It is supposed to be possible.

The second means of the present invention is to provide a direct current source, a resonance coil and a resonance capacitor connected in series to the direct current source, a first reverse conducting switching element for driving the resonance coil and the resonance capacitor, 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 has a direction in which the output current of the direct current source becomes a forward current. The second reverse conducting switching element is a high-frequency inverter arranged in a direction in which the output current of the direct current source becomes a reverse current, so that the forward current rising time of the first reverse conducting switching element becomes long, The gate can be easily driven, 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 the third means of the present invention, 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 blocking switching element for driving the resonance coil and the resonance capacitor. A conduction switching element and a control circuit for driving the reverse blocking switching element and the reverse conduction switching element are provided, and the reverse blocking switching element and the reverse conduction switching element are arranged in a direction in which the output current of the DC current source becomes a forward current. The high frequency inverter can be a device that operates stably even under no load.

The fourth means of the present invention is to provide a direct current source, a resonance coil and a resonance capacitor connected in series to the direct current source, a reverse blocking switching element for driving the resonance coil and the resonance capacitor, and reverse conduction. A switching element and a control circuit for driving the reverse blocking switching element and the reverse conducting switching element are provided, the reverse blocking switching element is arranged in a direction in which the output current of the DC current source becomes a forward current, and the reverse conducting switching element is a DC current. As a high-frequency inverter arranged in a direction in which the output current of the source becomes a reverse current, the rise time of the forward current of the reverse conduction switching element becomes long, the driving of the gate becomes easy, and the effect of the third means of the present invention In addition, the control circuit can be made compact and inexpensive.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a high frequency inverter in an embodiment of the 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 for explaining the operation of the high frequency inverter.

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

FIG. 5 is a waveform diagram illustrating the operation of the high frequency inverter.

FIG. 6 is a circuit diagram of a high frequency inverter in an embodiment of the third means of the present invention.

FIG. 7 is a waveform diagram illustrating the operation of the high frequency inverter.

FIG. 8 is a circuit diagram of a high frequency inverter in an embodiment of the fourth means of the present invention.

FIG. 9 is a waveform diagram illustrating 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 diagram 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 conduction switching device 9 ・ 15 ・ 33 Second reverse conduction switching device 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

Claims (4)

[Claims] 1. A direct current source, a resonance coil and a resonance capacitor connected in series to the direct current source, 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 and second reverse conducting switching elements are arranged in a direction in which the output current of the DC current source becomes a forward current. .. 2. A direct current source, a resonance coil and a resonance capacitor connected in series to the direct current source, 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 is a forward current, The reverse conduction switching element is a high-frequency inverter arranged so that the output current of the DC current source becomes a reverse current. 3. A direct current source, a resonance coil and a resonance capacitor connected in series to the direct 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 high-frequency inverter comprising a control circuit for driving an element and a reverse conduction switching element, and arranging the reverse blocking switching element and the reverse conduction switching element in a direction in which an output current of the DC current source becomes a forward current. 4. A direct current source, a resonance coil and a resonance capacitor connected in series to the direct 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. The device includes a control circuit that drives the element and the reverse conduction switching element.The reverse blocking switching element is arranged in the direction in which the output current of the DC current source becomes the forward current.The reverse conduction switching element has the output current of the DC current source as the reverse current. High frequency inverters arranged in the same direction.