JP2001069769A - Single-phase full-bridge inverter circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To balance the voltages impressed upon capacitors with each other by connecting a fifth switching element between the junction of the second winding of a choke coil with a second diode and the other end of a DC power source. SOLUTION: In a single-phase full-bridge inverter circuit, a fifth switching element T5 is connected between the junction of the second winding L2 of a choke coil L with a second diode D2 and the other end 12 of a DC power source 1. When the fifth switching element T5 is turned on, a current flows from one end 11 to the other end 12 of the power source 1 through the second winding L2 of the choke coil L and switching element T5 and energy is stored in the choke coil L. When the switching element T5 is turned off, on the other hand, the energy stored in the choke coil L is discharged, but, when VC1>VC2, the energy is shifted from the coil L to a second capacitor C2. When VC1<VC2, the energy is shifted to a first capacitor C1. Therefore, the voltages impressed upon the capacitors C1 and C2 can be balanced with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-phase full-bridge type inverter circuit.
DC voltage boosting means is interposed, thereby boosting the DC voltage and balancing the voltages applied to the first and second capacitors connected in series. A single-phase full-bridge inverter with a bidirectional function that can stabilize the DC potential at the series connection point of the capacitors and convert DC power to AC power and AC power to DC power. It is related to the circuit.

[0002]

2. Description of the Related Art A full-bridge type inverter circuit includes a DC power supply, a series connection circuit of first and second switching elements, and a series connection circuit of third and fourth switching elements. A load is connected between the series connection point of the second switching element and the series connection point of the third and fourth switching elements.

In the above-described full-bridge type inverter circuit, the DC voltage is set to the peak value of the AC voltage to be obtained, which is equal to the peak value of the AC voltage.
Conventionally, a boost chopper circuit as shown in FIG.

The boost chopper circuit shown in FIG. 5 includes a choke coil L ₀ between one end 11 and the other end 12 of the DC power supply 1.
And connecting a series circuit of a switching element T _0, while connected to one input terminal 31 of the inverter circuit 3 a series connection point between the choke coil L ₀ and the switching element T ₀ through the diode D _0, the The other end 12 of the DC power supply 1 is connected to the other input terminal 32 of the inverter circuit 3. Reference numeral 2 denotes a capacitor for absorbing ripple.

The inverter circuit 3 includes a first series connection circuit of a _first switching element T ₁ and a second switching element T ₂ , a third switching element T ₃ and a fourth switching element T _4. Are connected in parallel with each other, and a series connection point of the first switching element T ₁ and the second switching element T ₂ is connected to one output via a reactor L ₄₁ of the filter circuit 4. And a connection point between the _third switching element T ₃ and the fourth switching element T ₄ in series with the reactor L of the filter circuit 4.
₄₂ through the other output terminal, a single-phase full-bridge type connected to the load 5 between the output terminals, the capacitor C of the filter circuit 4 between the output side of the output side and the reactor L ₄₂ of the reactor L _{41 4} is connected. Since such an inverter circuit 3 and the above-described step-up chopper circuit are known, the description of the operation thereof is omitted.

[0006]

In the inverter circuit 3 and the [SUMMARY OF THE INVENTION], the load 5 has unbalanced components, the voltage applied to the first capacitor C ₁ and the second capacitor C ₂ becomes unbalanced However, there has been a problem that the output voltage from the side where the voltage has decreased does not reach the peak value.

In order to solve such a problem, conventionally, a first capacitor C ₁ and a second capacitor C ₂ are provided.
The dummy resistors were connected in parallel, and the voltage imbalance was eliminated by balancing the voltage applied to the dummy resistors with the loss caused by the dummy resistors. since this loss is larger when the voltage applied first and if the unbalance voltage larger first capacitor C ₁ and the second capacitor C ₂ large, when used in such applications, the lowering of conversion efficiency It was not preferable because of the cause.

[0008]

According to a first aspect of the present invention, there is provided a DC power supply having a first switching element and a first switching element having the other end connected to one end of a second switching element. A second circuit in which the other end of the third switching element is connected to one end of the fourth switching element;
And a third series connection circuit in which the other end of the first capacitor is connected to one end of the second capacitor, one end of the first capacitor, one end of the first switching element, and 3 are connected to one another, and the other end of the second capacitor;
A single-phase full-bridge type in which the other end of the second switching element and the other end of the fourth switching element are connected to each other to obtain an output between each series connection point of the first and second series connection circuits An inverter circuit, comprising: a choke coil having a center tap connected to a series connection point of the first capacitor and the second capacitor, wherein a first winding of the choke coil is connected via a first diode. The second winding is connected to the other end of the second capacitor, the second winding is connected to one end of the first capacitor via a second diode, and the one end of the DC power supply is connected to the center tap of the choke coil. Wherein a fifth switching element is connected between a connection point between a second winding of the choke coil and a second diode and the other end of the DC power supply. This may cause the load 5 to have an unbalanced component and increase the imbalance between the voltages applied to the first and second capacitors, or the input voltage of the half-bridge type inverter circuit. Balance the voltages applied to the first and second capacitors without reducing the conversion efficiency even when the voltage is high and the voltage applied to the first and second capacitors is large. Can be.

According to a second aspect of the present invention, in the single-phase full-bridge inverter circuit according to the first aspect, a choke having a center tap connected to a series connection point of the first capacitor and the second capacitor. And a first winding of the choke coil having a first diode and a first diode.
Connected to the other end of the second capacitor via a first parallel connection circuit with the second transistor, and a second winding is connected via a second parallel connection circuit between the second diode and the second transistor. One end of the DC power supply is connected to a center tap of the choke coil, and a connection point between a second winding of the choke coil and a second parallel connection circuit is connected to the DC power supply. A third diode and a third transistor between the other end of the power supply and the third diode;
Are connected, whereby the voltage applied to the first capacitor and the voltage applied to the second capacitor can be balanced, and the inverter circuit In addition, a bidirectional function capable of converting DC power into AC power and converting AC power into DC power can be provided.

According to a third aspect of the present invention, in the single-phase full-bridge inverter circuit according to the first or second aspect, the DC power supply is a storage battery, and a photomos circuit is used as a voltage detection circuit for detecting the voltage of the storage battery. Since the voltage detection circuit can be disconnected when it is not necessary to detect the voltage of the storage battery, unnecessary discharge of the storage battery can be prevented.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on its embodiments.

FIG. 1 is a circuit diagram of a single-phase full-bridge inverter circuit according to a first embodiment of the present invention.

[0013] Features of the single-phase full-bridge inverter circuit shown in FIG. 1, a DC power source 1, a first connecting a first end of the switching element T ₁ to a second end of the switching element T ₂ a series circuit, the second series connection circuit, the first end of the capacitor C ₁ second capacitor connected to the third end of the switching element T ₃ to a fourth end of the switching element T ₄ with connecting the third series circuit connected to one end of the C ₂ in parallel, the first choke coil L to the center tap to the series connection point is connected to the capacitor C ₁ and the second capacitor C ₂ the a first winding L ₁ of the choke coil L together with the second winding L ₂ is the second is connected to the second end of the capacitor C ₂ through the first diode D ₁ via said diode D ₂ first capacitor Is connected to one end of the C _1, one end 11 of the DC power source 1 is connected to the center tap of the choke coil L, the second winding of the choke coil L L
₂ is that the switching element T ₅ of the fifth is connected between the second diode D ₂ and the other end 12 of the DC power source 1 and the connection point between. The two capacitor for ripple absorption, the 4 reactor L _41, reactor L _42, a filter circuit comprising a capacitor C _4.

In the above-described single-phase full-bridge type inverter circuit, its input voltage, that is, the first capacitor C ₁
, A sum voltage V _C of the voltage V _C1 applied to the second capacitor C ₂ and the voltage V _C2 applied to the second capacitor C ₂ is detected, and the sum voltage V _C is amplified between a voltage reference value and a triangular wave. compared to the sum voltage V _C by creating a PWM control signal can control the switching element T ₅ of the fifth to be constant, also detects the sum voltage V _C and, this current reference The error voltage obtained by amplifying the error between the two values is smoothed to obtain a current target value, and the error voltage obtained by amplifying the error between the current target value and the input current of the three-phase half-bridge inverter circuit is calculated as follows. it is possible to control the switching element T ₅ of the fifth so that ripples of the AC power source 1 contained in the input current by creating a PWM control signal becomes smaller than the triangular wave.

Next, the operation of the above-described single-phase full-bridge type inverter circuit will be described.

(Operation Mode 1) This operation mode 1 is the fifth operation mode.
Switching element T ₅ of the case on. That is, when the switching element T ₅ of the fifth is turned on, one end of the DC power source 1 11 → second winding of the choke coil L L ₂ →
Current flows through the path of the fifth switching element T ₅ → the other end 12 of the DC power supply 1 and energy is accumulated in the choke coil L.

(Operation Mode 2) This operation mode 2 is the fifth operation mode.
Switching element T ₅ of the case off. That is, the switching element T ₅ of the fifth is turned off, but the energy in the operation mode 1 have been accumulated in the choke coil L is discharged, the voltage V _C1 applied to the first capacitor C ₁ second Voltage V _C2 applied to capacitor C ₂
The release route differs depending on the magnitude relation of

That is, the first winding L of the choke coil L
If the second winding L ₂ of the number of turns of _the number of turns = choke coil L, V _C1> For V _C2 at the node between the first winding L ₁ and the first diode D ₁ of the choke coil L potential first diode D is lower than the potential of the other end of the second capacitor C ₂ (the anode side of the potential of the first diode D _1)
1 is forward biased, the first winding L ₁ of the choke coil L → the second capacitor C ₂ → the first diode D ₁
→ a current flows in the first winding L ₁ becomes the path of the choke coil L is energy of the choke coil L is transferred to the second capacitor C _2. At this time, the choke coil secondary winding L ₂ and the potential at the connection point between the second diode D ₂ second diode D ₂ is reverse biased is lower than the first end of the potential of the capacitor C ₁ of L The choke coil L
No current flows through the path of the second winding L ₂ → the second diode D ₂ → the first capacitor C ₁ → the second winding L ₂ of the choke coil L.

Similarly, when V _C1 <V _C2 , the potential at the connection point between the second winding L ₂ of the choke coil L and the second diode D ₂ is the potential at one end of the first capacitor C ₁ (the potential at the one end of the first capacitor C ₁ ). The potential on the cathode side of the _second diode D2).
Since the diode D ₂ is forward biased, the second winding of the choke coil L L ₂ → second diode D ₂ → first capacitor C ₁ → second winding L ₂ consisting path current of the choke coil L energy of the choke coil L is transferred to the first capacitor C ₁ is flowing. At this time, the first winding L ₁ of the choke coil L and the potential at the connection point between the first diode D ₁ the first diode D ₁ is reverse higher than the second electric potential at the other end of the capacitor C ₂ Being biased, the first winding L ₁ of the choke coil L → the second capacitor C ₂
No current flows through the path of the first diode D ₁ → the first winding L ₁ of the choke coil L.

According to each operation mode described above, V _C1 > V
Since in the case of _C2 energy of the choke coil L is transferred to the second capacitor C _2, the voltage V _C2 of the second voltage V _C2 of the capacitor C ₂ is applied to the second capacitor C ₂ rises first it is possible to balance the voltage V _C1 applied to the first capacitor C _1, in the case of V _C1 <V _C2 because energy of the choke coil L is transferred to the first capacitor C _1, the first capacitor C ₁ voltage V _C1 can be balanced with the voltage V _C2 applied to the first voltage V _C1 applied to the capacitor C ₁ to the second capacitor C ₂ rises.

FIG. 2 is a circuit diagram of a single-phase full-bridge inverter circuit according to a second embodiment of the present invention.

The feature of the embodiment shown in FIG. 2 is that the first diode D ₁ is replaced by the first diode D ₁ .
The transistors S ₁ and the first parallel connection circuit connected in parallel, instead of the second diode D _2, a second parallel connection of connecting the second transistor S ₂ in parallel with the second diode D ₂ and circuitry, in place of the switching element T ₅ of the fifth, third transistor S to the third diode D _3
3 is a third parallel connection circuit connected in parallel.

According to the above-described second embodiment, the third embodiment
On the transistor S _3, together with the first voltage V _C1 of the capacitor by turning off the voltage V _C2 of the second capacitor can be balanced, the function of converting the DC power mentioned above into AC power, the AC power Since bidirectionality can be achieved by adding a function of converting to DC power, it can be used for interconnection operation between a system for obtaining AC power and a DC power supply such as a solar cell.

That is, the AC side of the single-phase full-bridge type inverter circuit described above is connected to the system, and the AC power from the system is converted into DC power by the inverter circuit and supplied to the DC power supply 1. The operation is performed in the following operation modes 3 and 4.

(Operation Mode 3) This operation mode 3 is the third operation mode.
Of the transistor S ₃ is turned off, first the first parallel connection circuit
Of a case where the transistor S ₁ and the second transistor S ₂ of the second parallel connection circuit is ON, thereby, a second first end of the capacitor C ₁ → second transistor S ₂ → choke coil L Winding L ₂ → First of choke coil L
A current flows through a path from the winding L ₁ → the first transistor S ₁ → the other end of the second capacitor C ₂ , and energy is stored in the choke coil L.

(Operation Mode 4) This operation mode 4 is the third operation mode.
Of the transistor S ₃ is turned off, first the first parallel connection circuit
Transistors S ₁ and the case of the second transistor S ₂ is turned off in the second parallel connection circuit, thereby, the second winding L ₂ → DC power source 1 → the third diode → choke coil of the choke coil L of The current stored in the choke coil L is transferred to the DC power supply 1 by passing a current through the path of the second winding L _{2 of} L, so that the AC power from the system is converted into DC power by the inverter circuit 3. It can be supplied to a DC power supply 1 such as a storage battery.

Further, according to each of the above-described embodiments, an inverter circuit is used in an uninterruptible power supply,
Is a storage battery, and if a voltage detection circuit 20 for detecting the voltage of the storage battery is provided, the storage battery may be continuously discharged with a very small current by the voltage detection circuit 20, and a problem that recovery of capacity due to sulfation may not be achieved may occur. 3 and 4 in which the photomos circuit 21 is interposed in the voltage detection circuit 20, so that the above-mentioned problem can be solved.

[0028]

As described above, the present invention relates to a single-phase full-bridge inverter circuit in which the load 5 has an unbalanced component and the voltage applied to the first capacitor and the second capacitor is unbalanced. When the input voltage is high and the voltage applied to the first capacitor and the second capacitor is large, the first capacitor and the second capacitor can be connected without lowering the conversion efficiency. The voltage applied to the capacitors can be balanced, and the series connection point of the first capacitor and the second capacitor can be directly connected to one end of the DC power source as a neutral point and grounded to neutral point. Bi-directional that can stabilize DC potential, reduce high-frequency leakage current and EMI noise, and convert DC power to AC power and AC power to DC power It is possible to have a function, that contribute However large expansion of the single-phase full-bridge inverter circuit applications.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a single-phase full-bridge inverter circuit according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a single-phase full-bridge inverter circuit according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram when a voltage detection circuit is provided in the single-phase full-bridge inverter circuit according to the embodiment of FIG. 1;

FIG. 4 is a circuit diagram in a case where a voltage detection circuit is provided in the single-phase full-bridge inverter circuit according to the embodiment of FIG. 2;

FIG. 5 is a circuit diagram of a conventional single-phase full-bridge inverter circuit.

[Explanation of symbols]

 1 DC power supply 2 Capacitor 3 Inverter circuit 4 Filter circuit 5 Load

Claims (3)

[Claims] 1. A DC power supply, a first series connection circuit having the other end of a first switching element connected to one end of a second switching element, and a fourth series connection circuit having the other end of a third switching element connected to a fourth switching element.
A second series connection circuit connected to one end of the switching element, and a third series connection circuit connected to the other end of the first capacitor to one end of the second capacitor. One end of the first switching element and one end of the third switching element are connected to each other, and the other end of the second capacitor, the other end of the second switching element, and the other end of the fourth switching element are connected to each other. A single-phase full-bridge type inverter circuit connected to each other and configured to obtain an output between respective series connection points of the first and second series connection circuits, wherein the first capacitor and the second capacitor are connected to each other.
A choke coil having a center tap connected to a series connection point with a capacitor of the first type.
A winding is connected to the other end of the second capacitor via a first diode, and a second winding is connected to one end of the first capacitor via a second diode. One end is connected to a center tap of the choke coil, and a fifth switching element is connected between a connection point between a second winding of the choke coil and a second diode and the other end of the DC power supply. A single-phase full-bridge type inverter circuit characterized by the following. 2. The single-phase full-bridge inverter circuit according to claim 1, further comprising: a choke coil having a center tap connected to a series connection point of the first capacitor and the second capacitor. Is connected to the other end of the second capacitor via a first parallel connection circuit of a first diode and a first transistor, and a second winding is connected to a second diode and a second transistor. A second transistor connected to one end of the first capacitor via a second parallel connection circuit, one end of the DC power supply is connected to a center tap of the choke coil, and A third parallel connection circuit comprising a third diode and a third transistor is connected between a connection point with the second parallel connection circuit and the other end of the DC power supply. Phase full bridge type inverter circuit. 3. The single-phase full-bridge inverter circuit according to claim 1, wherein the DC power supply is a storage battery, and a photomos circuit is inserted in a voltage detection circuit for detecting a voltage of the storage battery. Single-phase full-bridge inverter circuit.