JPH08228486A - Control method of dc-ac inverter - Google Patents

Abstract

PURPOSE: To prevent the drop of efficiency caused by the capacitance between the electrodes of switching element, and enable the operation of high frequency by clamping the voltage added to the switching element below the power source voltage, and also, keeping the condition of Z.V.S, making use of accumulated energy. CONSTITUTION: Voltage is added to the series circuit of a rectifier D2 for clamping, a transformer 5 parallel with a switching element S2 , and a capacitor C2 by a switching element S1 parallel with a clamp rectifier D1 . The voltage added to the switching elements S1 and S2 is clamped below the voltage of the power source 1 by the rectifier D2 for clamping by turning on or turning off the switching elements S1 and S2 at a proper delay time. By making use of the energy accumulated in the primary winding of the transformer 5 and the capacitor C2 , the condition of Z.V.S(zero volt switching) is always kept, covering a wide output control range.

Description

Detailed Description of the Invention

[0001]

[Field of Industrial Application] This is a method for realizing a small-sized DC-AC inverter having high efficiency and a wide control range, and can be used in all industries that require DC voltage or high frequency power.

[0002]

2. Description of the Related Art In a DC-DC converter that converts a direct current into an alternating current by applying a direct current to a DC-AC inverter, rectifies the alternating current voltage, and then smooths it with a filter to obtain a direct current voltage, a DC-DC converter is used as a technique for downsizing the device. A method of increasing the switching frequency of the AC inverter to downsize the transformer and the filter has been adopted. However, if the switching frequency is raised, the switching loss of the switching element and the like also increases, so that there is a limit to raising the switching frequency, and this switching frequency is limited to several 100 kHz.

A resonance type DC-AC inverter is used as a method of further increasing the switching frequency to reduce the size. In this method, the voltage or current applied to the switching element is made into a sine wave or a half-wave sine wave having a period of zero half cycle by using the resonance characteristic of LC, and the switching element is turned on during the period when the voltage or current becomes zero. However, there is a method of significantly reducing the switching loss of the switching element.

A method of switching in a period when the voltage applied to the switching element is zero is described in Z. V. S (Zero
VOLT SWITCHING), a method of switching during a period when the current is zero is described in Z. C. S (Zero Cur
rent switching). These methods have ideal characteristics that not only greatly reduce switching loss but also significantly reduce switching noise during switching.

However, in these resonant DC-AC inverters, the energy to be processed per switching cycle is almost fixed, and the output is controlled by controlling the ON time of the switching element like a conventional switching regulator. Is difficult. The reason for this is that when the ON time of the switching element is controlled, the timing when the voltage or current of the switching element becomes zero also changes, so that the switching element is turned on in accordance with the period when the voltage or current of the switching element is zero. This is because it is difficult to obtain delicate timing, or when the ON time of the switching element is short, sufficient resonance energy is not applied to the resonance circuit, and the period during which the voltage or current becomes zero is insufficient.

Therefore, in order to eliminate this drawback, Z.
C. US Patent 441 which is a typical example of S
5959 Foward Converter at Z
As seen in ero Current, in order to control the output, the switching frequency was changed and the energy per unit time was changed to control the output while keeping the ON time of the switching element constant.

[0007]

As described above, the conventional method has been to change the switching frequency of the DC-AC inverter as a method for controlling the output. In this method, there is a problem that the effect of the filter is lowered because the switching frequency is lowered when the output voltage is lowered or when the load is light. Furthermore, when a plurality of power supplies are used at the same time, beat interference due to the frequency difference between them occurs, and the frequency band of noise also changes depending on input conditions and load conditions, which may cause unexpected noise interference. Also,
Z. V. S and Z. C. In the method in which the switching frequency is fixed under the condition of S and the output is controlled by varying the OFF time and ON time of the switching element, the variable range of the output is narrow, and the optimum timing for turning on the switching element can be obtained. It was difficult.

Further, in the resonance type inverter, Z. C.
Under the condition of S, there is a drawback that the peak value of the current flowing through the switching element becomes high and the energy accumulated in the interelectrode capacitance of the switching element becomes a loss. V. S
Has a drawback that the voltage value applied to the switching element becomes high, and the switching frequency is fixed and Z. V. The control circuit of the inverter that maintains the condition of S and the voltage applied to the switching element is low was the ultimate dream of power electro technology.

[0009]

In consideration of such a point, the present invention abandons the conventional idea of resonance and clamps the rectifier D ₁ for clamping in parallel with the switch S ₁ . Rectifier D ₂ and switching element S ₂
For a clamp in which a voltage is applied to a series circuit of a transformer and a capacitor having a parallel switch, switches S ₁ and S ₂ are alternately turned on and off with an appropriate delay time, and the voltage applied to the switching device is connected in parallel to the switching device. By using the energy stored in the primary winding of the transformer and the capacitor in parallel with the switching element to clamp below the power supply voltage by the rectifier, the Z.
V. A circuit that always keeps the condition of S is adopted, and the voltage energy accumulated in the interelectrode capacitance of the switching element is also effectively used to increase efficiency.

[0010]

As shown in FIG. 1, a circuit in which the primary winding of the transformer 3 and C ₃ of the capacitor 9 are connected in series is connected to the diode D ₂ of the diode 8.
Parallel C ₂ of the capacitor 3 connected in parallel, the addition of V _i of the voltage 1 in S ₁ of the switch 6 having a D ₁ of the C ₁ and parallel diode 8 parallel capacitors 7 and, C of the capacitor 9
_A voltage is applied to the transformer ₃ through 3 and an output voltage is generated in this secondary winding. The current that flows at this time is the C of the capacitor 9.
Charge ₃

[0011] S ₁ of the switch 6 for maintaining the current flowing through the primary winding of the switch S ₁ is turned OFF, the transformer 3 is turned ON S ₁ of the switch 6 time T _ON1 has elapsed
The current flowing through the capacitor 7 charges C ₁ of the capacitor 7, and when the capacitance of C ₃ of the capacitor 9 is sufficiently larger than the capacitance C _{1 of the} capacitor 7, the current flowing immediately before the S ₁ of the switch 6 is cut off. _{Is iON1} and the capacitance C _{1 of the} capacitor 7 is
When the parallel combined capacitance of C _{2 and} the capacitance C ₂ of the capacitor 3 is C _S , the terminal voltage V _S1 of S ₁ of the switch 6 is S _S of the switch 6.
I _ON1 t / C for the elapsed time t from turning OFF _1
When it rises at _S and this voltage becomes larger than V _{i of the} power supply voltage 1, D _{2 of} the diode 2 becomes conductive, the terminal voltage of S ₁ of the switch 6 is clamped to the power supply voltage, and C _{3 of} the capacitor 9 is further charged. It

When S ₂ of the switch 4 is turned on in this state, the terminal voltage v _S2 of S ₂ of the switch 4 becomes D ₂ of the diode _2.
Forward voltage, which is almost zero, Z. V. It becomes the condition of S. When S _{2 of the} switch 6 is turned on, the voltage charged in the C ₃ of the capacitor 9 is applied to the transformer 5, the primary winding voltage of the transformer is inverted, and S ₂ of the switch 4 is in the forward direction (C ₃ of the capacitor 9). A current flows in the direction of discharging electric charges. Current transformer current has been flowing in the primary winding of the transformer 5 S ₂ of the switch 4 OFF Then immediately before this state flowing through the S ₂ switch 4 in the forward direction by the charge accumulated in the capacitor 9 Is i _ON2 , this current charges C ₂ of the capacitor 3 and discharges C ₁ of the capacitor 7.

Therefore, the voltage of C ₁ of the capacitor 7 falls at i _ON2 t / C _S, where t is the elapsed time after S ₂ of the switch 4 is turned off, and (C _{2 of the} capacitor 3
When this voltage becomes negative, D _{1 of the} diode 8 becomes conductive and the S ₂ terminal voltage of the switch 6 is clamped to the power supply voltage. During the period when D _{1 of the} diode 8 is conducting, the terminal voltage of S ₁ of the switch 6 is the forward voltage of D ₁ of the diode 8 and is almost zero. If S ₁ of switch 6 is turned on during this period, Z. V. The S ₁ of the switch 6 can be ON in the condition of S. While repeating the same operation, S _{1 of the} switch 6 and S ₂ of the switch 4 are Z. V.
Switching is performed while the voltage of the switching element is clamped by the power supply voltage under the condition of S and the high frequency output is transmitted to the secondary winding of the transformer 5.

To control the output power, the S of switch 6
Switch 6 for controlling the ratio of ON time and OFF time of ₁
No matter which period the S ₁ is turned off, the falling of the voltage is suppressed by the C _{1 of} the capacitor 7 connected in parallel with the S ₁ of the switch 6, so that Z. V. It can be turned off under the condition of S. Power is supplied from the power supply when S _{1 of} switch 6 is ON, and energy is supplied to the output when there is a forward characteristic rectifier on the secondary side of the transformer, and at the same time the equivalent inductance of leakage inductance of the transformer is set. It is also stored as current energy in the included primary inductance. At this time, the energy obtained from the power supply side is proportional to the ON time of S ₁ of the switch 6.

When S _{1 of the} switch 6 is turned off, if there is a flyback rectifier on the secondary side of the transformer 5, the energy accumulated while the S ₁ of the switch 6 is on is supplied to the output side. At the same time, C ₃ of the capacitor 9 is charged. When S _{2 of} switch 4 turns on, C _{3 of} capacitor 9
Stored energy is supplied to the output through the flyback direction of the rectifier, since S ₁ of energy switch 6 at this time increases the longer the time to ON, by controlling the ON time of the S ₁ switch 6 It is also possible to control the output. However, when the ON time of S ₁ of the switch 6 is controlled, the charge amount of C ₃ of the capacitor 9 can be automatically controlled at the same time. Therefore, it is rational to control the ON time of S ₁ of the switch 6 to control the output. Is.

At this time, S _{1 of} switch 6 and switch 4
S ₂ of turns on and off alternately with a certain delay. Therefore, if the sum of the ON time of S ₁ of switch 6 and the ON time of S ₂ of switch 4 is kept constant and the time ratio of ON and OFF of S _{1 of} switch 6 and S ₂ of switch 4 is controlled, the switching frequency is It becomes possible to control the output at a constant value, which is the most convenient control method.

As another control method, the O of the switch 4S ₂ is turned on.
It is possible to change the output by controlling only the ON time of the switch 6S _{1 while} keeping the N time constant, but if the ON time of the switch 6S ₁ is shortened for the purpose of lowering the output, the primary winding of the transformer 5 is reduced. If the voltage of the switch 2S ₂ cannot be maintained during the delay time TD ₂ from turning off the switch 6S ₁ to turning on the switch 4S ₂ due to lack of energy stored in Z.
V. The condition of S cannot be satisfied. If a leakage inductance is added to the transformer or the inductance is further connected in series, it is possible to obtain the time for effectively charging the capacitor 9 with the energy stored in this inductance, and this problem can be prevented. Switch 6S ₁ ON time is kept constant, switch 4S ₂ ON
The same operation is performed when the time is changed.

[0018]

EXAMPLE An example is shown in FIG. In this embodiment, a capacitor 9 is connected in series to the primary winding of the transformer 5 and the power supply voltage 1 is applied at S ₁ of the switch 6. A capacitor 7 and a clamp diode 8 are connected in parallel to the switch 6. On the other hand, a switch 4 for shunting the primary winding of the transformer 5 and both ends of the capacitor 9 is provided, and the capacitor 3 and the clamp diode 2 are also connected in parallel to this switch. The secondary side of the transformer is rectified by a center tap rectifier circuit by a diode 10 and smoothed by a smoothing capacitor 11 to supply DC power to a load resistor 12.

It is convenient to use transistors and FETs for the switches 4 and 6 used here. Since the inter-electrode capacitance is large in the FET, this capacitance is used as the parallel capacitor 3 or 7
Available as The series capacitor 9 does not need to resonate with the inductance of the transformer, and is practically set to several tens of times the capacity of the parallel capacitors 3 and 7, but even if this value is changed by an order of magnitude, it remains close to the switching frequency. If the series impedance of the input impedance of the capacitor 9 and the transformer 5 is inductive, the basic operation does not change.

When used as a DC-DC converter, the rectifier circuit is not limited to the center tap shown in FIG. 1 but can be used in a bridge circuit, and can operate as a forward-type or flyback-type half-wave rectifier, and the smoothing circuit can also be a capacitor. It is not limited to the input type. If the secondary side rectifier circuit is a forward type half-wave rectifier circuit, most of the flyback energy operates to charge the capacitor 9.

_Regarding the operation timings of the switches 6 and 4, the switch 6 is first turned on, and the switch 6 is turned off when the time T _ON1 has elapsed. The switch 4 is turned on with a delay time of TD ₁ from turning off the switch 6 to turning on the diode 2.

The switch 4 is turned on during the period T _ON2 . Next, the switch 4 is turned off, the delay time TD ₂ until the diode 8 becomes conductive is taken, and the switch 6 is turned on. The voltage-current waveform of the switching element in this state is shown in FIG. The output electric power is an average value of electric power per unit time obtained by multiplying the power supply voltage by the integrated value of the current value of the switch 6.

[0023] While the control of the output is also possible to control the time T _ON2, and T _ON1 and TD _1, TD ₂ as constant T
When the sum of _ON2 varying the ratio of T _ON1 and T _ON2 in the constant can always be varying the output by a constant switching frequency. The voltage-current waveform of each switching element at this time is shown in FIG.

However, depending on the rectifier and the smoothing circuit, the extent to which the energy accumulated during the period when the switch 6 is ON is transmitted to the capacitor 9 is different, and the switch 6 is turned OFF.
After that, Z. V. The time for keeping S becomes longer, the margin value for the delay time until the switch 4 is turned on increases, and the delay time increases as the impedance seen from the primary input of the transformer becomes more inductive, and the timing of turning on the switch 4 The degree of freedom is increased, and the timing for turning on the switch 4 is set to 0 for the switch 6.
There is no need to make it immediately after FF, switch 4 turns ON
The present invention can be realized even if the time is fixed. When the ON time of the switch 4 is fixed in this way, as shown in FIG. V. In some cases, there is a period in which the condition of S is not satisfied, but this voltage is lower than the voltage of the inverter by another method, and even if the voltage waveform shown in (a) is obtained, for example, the parallel capacitance of the switch 4 at this time is The stored power is small and the harm is small. Further, the waveform as shown in (b) does not cause any actual damage, and the object of the present invention can be achieved even if the drive circuit is simplified in this way.

In principle, the control system of the present invention requires that the series input impedance of the transformer 5 including the series capacitor 9 be inductive near the switching frequency. Moreover, the output power is inversely proportional to this inductance. Therefore, when the transformer has a high inductance, the energy storage inductance is connected in parallel with this transformer.

In the DC-DC converter, when the rectifier on the secondary side of the transformer is of the capacitor input type, power is transmitted to the output during the period when the rectifier on the secondary side is conducting in the flyback state, and the capacitor 9 Energy is not stored in. Therefore, to solve this problem, either connect an inductance in series with the transformer or give the transformer a leakage inductance.

As shown in FIG. 5, the primary winding of the transformer is divided into L ₁ and L ₂ , and the secondary winding L is associated with this primary winding.
₃ and L ₄ are provided. Here, if the coupling coefficient of L ₁ and L ₂ is lowered, even if one rectifier conducts and the effect of the inductance decreases, the winding on the side where the other rectifier does not conduct acts as an inductance, and Inductance can be omitted. When the coupling coefficient of L ₁ and L ₂ is zero, that is, when L ₁ and L ₂ are separated and two transformers having L ₁ , L ₃ and L ₂ and L ₄ are connected in series, mutual influence is exerted. It has the most power because it is not available. However, using two transformers can lead to space factor and cost issues.

In this case, for example, if L ₁ and L ₂ are physically separated by a distance as shown in FIG. 6, mutual influences can be prevented, and if a core shown by hatching in FIG. The effect increases. Another method is to use different core legs as shown in FIGS. 8 and 9. A similar objective is achieved by increasing the space between the windings of each other.

When the power supply voltage is higher than the withstand voltage of the switching element, the switch 6 is divided into plus and minus of the power source as shown in FIG. 10, and the shunt switches 4 are connected in series to each other and the plus and minus of the power source are connected. 2 when connecting to the midpoint of the distributed voltage balancing capacitor 13
It is possible to support double power supply voltage.

The circuit of FIG. 1 is a conventional one-stone DC-
It looks like a circuit in which a capacitor 9 is added in series to the primary winding of the AC inverter, and a shunt switch 4 is attached. However, even if the winding start terminal of the transformer is connected not to the positive side of the power supply but to the negative side, the same operation is performed. This circuit is similar to the half-bridge DC-AC inverter that is often used conventionally, and is also similar to the circuit in which a transformer is connected to the output of the OTL amplifier by capacitor coupling. In this way, the basic circuit is similar to the already known circuit, and although it is very simple, just select the operation timing of each switch and make the impedance seen from the primary side of the transformer inductive. The point of the present invention is to obtain a DC-AC inverter having ideal characteristics that are ideal for engineers.

[0031]

EFFECTS OF THE INVENTION According to the present invention, the Z.Z.
V. It is possible to realize a DC-AC inverter that maintains the S characteristic and can vary the output over a wide range while fixing the switching frequency. Moreover, even when the power supply is turned on or in the worst transient state such as an output short-circuit accident, a voltage higher than the power supply voltage is not applied to the switching element, so that a switching element with low withstand voltage can be used, and the cost of the switching element can be reduced. Can be lowered.

When an FET is used as the switching element, the interelectrode capacitance is Z. V. Not only can it be used to realize S, an element with a low ON resistance can be adopted, and a high-power inverter that uses direct current obtained by rectifying a three-phase commercial power source can also operate efficiently.

The DC-AC inverter according to the present invention is
Z. V. Although the radiated noise is significantly reduced due to the characteristics of S, the effect is further enhanced because the switching voltage is also low. At the same time, the voltage energy accumulated in the interelectrode capacitance of the switching element does not become a loss, and even if a switching frequency with a high frequency on the order of MHz is used,
A high efficiency of 0% or more can be obtained.

In this control method, Z. V. Even if the worst condition that does not satisfy the condition of S is assumed, the switching element is forcibly turned on with the voltage applied to the switching element.
It is possible to reduce the voltage immediately before the switch is turned on to 1 / π or less, as compared with the conventional current resonance method. Since the loss due to the interelectrode capacitance of the switching element is proportional to the square of the voltage, this loss is also about 1/10.

For this reason, using this output, D
When a C-DC converter is realized, a DC-DC converter having a small size, high efficiency, and low radiation noise characteristics can be obtained. Further, to explain the effect of the present invention, since the switching element is switched in series with the capacitor, even if a transient current flows due to power-on or failure, the switching element is charged with the series capacitor. And no more current flows and the current is automatically limited. The higher the switching frequency, the lower the capacitance value of the series capacitor, and the lower the current value of the switching element flowing during the transition.

Since the voltage applied to the switching element does not exceed the power supply voltage, the problem of the safe operation area of the switching element is eliminated, and the reliability of the inverter is greatly improved. Furthermore, since the transformer is connected in series with the capacitor, no direct current component flows through the transformer regardless of the ON / OFF ratio of each switch, which reduces efficiency due to biased magnetism of the transformer and It is also possible to prevent saturation.

A conventional flyback type DC-AC inverter utilizes Z.V. V. Although it was possible to realize S, many problems occur due to the secondary resonance of the order of MHz generated by the leakage inductance of the transformer and the capacitance between the electrodes of the switching element, and it is difficult to eliminate this effect. there were. In the present invention, the leakage inductance of the transformer, which has been a problem in the conventional method, can be used in reverse, and the flexibility of the transformer design is increased.

In the DC-DC converter using this inverter, the utilization factor of the switching element and the rectifier is high, the effective current of the current flowing through the transformer and the switching element is relatively low, and the transformer can be miniaturized. further,
Since the present invention does not utilize resonance, it has a feature that it is simple in design and has a high tolerance to changes in circuit constants. The output of the DC-AC inverter of the present invention can be used as it is, or through a filter, a matching circuit, etc., as an AC output of a high-frequency heater, rotating equipment, etc.
Even in matching, it is possible to prevent an increase in the loss of the switching element, and it is possible to simplify the matching circuit, so that the usage range is wide.

As described above, the control system of the present invention has many features and is an ideal control system that exceeds the conventional wisdom of conventional inverters. Since the drive circuit of each switching element is different from the conventional method, it is currently difficult to obtain a suitable one-chip IC, but it is easily controlled by a combination of simple logic circuits or a self-excited oscillation circuit. A circuit can be realized. Even if a special IC for a control circuit for realizing the present invention is specially manufactured, there is a possibility that the IC can be sufficiently paid. There is a possibility that the high-voltage switching element for the inverter, which is not included, may be unnecessary.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment in which the present invention is used as a DC-DC converter.

FIG. 2 is a diagram showing a voltage / current waveform of each switch when the switches S ₁ and S _{2 have} the same duty and have opposite operations with a certain delay.

[Figure 3] to narrow the ON width of the switch S _1, the switch S ₁
6 is a diagram showing voltage-current waveforms of respective switches when the switch S ₂ is reversely operated with a certain delay time with respect to ON / OFF of FIG.

[Fig. 4] The ON width of the switch S ₂ is fixed, and the switch S ₁ is fixed.
_{2 is} a voltage waveform of the switch S ₂ when the ON width of the switch is narrowed.

FIG. 5 is a diagram showing a primary winding and a secondary side rectifier of a transformer.

FIG. 6 is a schematic diagram of a method of reducing the coupling coefficient between L ₁ and L ₂ of the primary winding by increasing the distance between the windings.

FIG. 7 is a schematic diagram of a method of reducing the coupling coefficient between L ₁ and L ₂ of the primary winding with an attached core by increasing the distance between the windings.

FIG. 8 is a schematic diagram of a method of separating the legs of the core between each winding to reduce the coupling coefficient of L ₁ and L ₂ of the primary winding.

FIG. 9 is a schematic view of a method of separating the legs of the core between the respective windings and providing a shared magnetic path in the middle to reduce the coupling coefficient of L ₁ and L ₂ of the primary winding.

FIG. 10 is a circuit diagram in which the balance of the voltage applied to each switch when the switches are connected in series is improved.

[Explanation of symbols]

1 input supply (voltage V _i) 2 clamp diode (D ₂₎ 3 capacitor (C ₂₎ 4 switching elements (S ₂₎ 5 transformer 6 switching elements (S ₁₎ 7 resonant capacitor (C ₁₎ 8 clamp diode (D ₁ ) 9 series capacitor (C ₃ ) 10 rectifier 11 filter capacitor 12 load resistor 13 voltage balancing capacitor

Claims (5)

[Claims] 1. A switching element S ₁ having a characteristic of conducting in a reverse direction and a parallel capacitance in a series circuit of a capacitor and a primary winding of one or more transformers, and after _applying a voltage for a period of T _{ON1 to} the switching element S _1. Switching element S ₂ having a characteristic and parallel capacitance that conducts in the opposite direction after delay time TD ₁ after turning OFF ₁ and switching element S ₁ becomes 0FF
The series circuit of the primary winding of the transformer and the capacitor is
Only period _ON2 shorted Substitution on behalf of the primary winding current of the transformer to the switching element S _1. In DC-AC inverter switching element S ₂ to output the AC power to the secondary winding of the repeating by transformer operation to ON again switching element S ₁ with a period TD ₂ from the OFF, T for T _{ON1 ON2} A method of controlling a DC-AC inverter, which controls the output of the DC-AC inverter by controlling the ratio of the voltage and the energy applied to the transformer. 2. A switching element S ₁ having a characteristic of conducting in a reverse direction to a series circuit of a capacitor, a primary winding of one or more transformers, and an inductance, and a parallel capacitance, T _ON1
After applying voltage for the period of time, switching element S ₁ is turned off.
Then, after the switching element S ₁ becomes 0FF, the delay time T
The primary winding current of the transformer is short-circuited by the switching element S ₂ having the characteristic of conducting in the opposite direction and the parallel capacitance after D ₁ to short-circuit the series circuit of the primary winding of the transformer, the inductance and the capacitor for the period of T _ON2. It replaces in place of the switching element S ₁ . Again O switching element S ₁ switching element S ₂ is with a period TD ₂ from the OFF
A DC-AC inverter that repeats N operations to output AC power to the secondary winding of the transformer, and a switching element S.
The method of DC-AC inverter for controlling the output by controlling the energy applied to control the ratio in transformer T _ON2 for a is T _{ON1 1} of ON time. _3. A period of T _{ON1 in} a switching element S ₁ having a parallel capacitance and a characteristic of conducting serially in the reverse direction to a series circuit of primary windings of a plurality of transformers having leakage inductances in series with a capacitor. After the voltage is applied, the switching element S ₁ is turned off, and after the delay time TD ₁ after the switching element S ₁ becomes 0FF, the switching element S ₂ having the characteristic of conducting in the reverse direction and the parallel capacitance has the primary winding of the transformer. The series circuit of the line, the inductance and the capacitor is short-circuited for the period of T _ON2 , and the primary winding current of the transformer is changed in place of the switching element S ₁ . Outputting AC power to the secondary winding of the transformer by repeating the operation of turning on the switching element S ₁ again in the period of TD ₂ after the switching element S ₂ is turned off.
And C-AC inverter, a control method of the DC-AC inverter for controlling the output by controlling the energy applied to control the ratio in transformer T _ON2 against T _ON1. 4. A series circuit of a primary winding and an inductance of a plurality of transformers having a leakage inductance that are intentionally separated from each other by sharing the same magnetic path in series with a capacitor. After a voltage is applied for a period of T _ON1 by a switching element S ₁ having a characteristic of conducting in the reverse direction and a parallel capacitance, the switching element S ₁ is turned off, and after a delay time TD ₁ after the switching element S ₁ becomes 0FF. Switching element S having a characteristic of conducting in the opposite direction and a parallel capacitance
_By means of ₂ , the series circuit of the primary winding of the transformer, the inductance and the capacitor is short-circuited for the period of T _ON2 , and the primary winding current of the transformer is replaced in place of the switching element S ₁ . DC for outputting AC power to the secondary winding of the transformer by repeating the operation of turning on the switching element S ₁ again in the period of TD ₂ after the switching element S ₂ is turned off.
-AC inverter and method for controlling a DC-AC inverter for controlling the output by controlling the energy applied to the transformer by controlling the ratio of T _ON2 against T _ON1. 5. The method according to any one of claims 1 to 4, wherein S ₁ of the switch 6 and S ₂ of the switch 4 are connected in series to each other to reduce the voltage applied to the switching element, thereby responding to a high input voltage. 10, the S ₁ of the switch 6 is distributed to the positive side and the negative side of the input power source 1 as shown in FIG. 10, and the series circuit of the transformer 5 and the capacitor 9 is short-circuited by the S _{2 of} the switch 4 connected in series. Circuit,
Voltage balancing capacitor 1 in which the midpoint of S ₂ of the switch 4 connected in series is connected in series between the positive and negative sides of the power supply 1.
A DC-AC inverter connected to the middle point of 3 to improve the voltage balance applied to each switching element.