JP3276126B2 - Bridge circuit and inverter device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bridge circuit using a self-extinguishing switch element and an inverter device using the bridge circuit.

[0002]

2. Description of the Related Art A bridge circuit using a self-extinguishing switch element is widely used in an inverter device or the like for converting a DC voltage into an AC voltage by pulse width modulation. In this bridge circuit, when the switch element is turned off and the current is rapidly interrupted, an overvoltage is generated due to the release of residual energy of the inductance existing in the circuit, and this overvoltage is suppressed within the allowable voltage of the switch element. A snubber circuit is provided. The snubber circuit has a capacitor that absorbs energy as a charge, and the charge absorbed by the capacitor is usually discharged to a resistor and consumed as heat.

However, in recent years, a self-extinguishing type switching element such as an IGBT which operates at a high speed is used, and as the switching frequency becomes higher, the power loss of the snubber circuit increases and the conversion efficiency decreases. Has arisen.
In order to solve this problem, various snubber circuits have been attempted in which the charge stored in the capacitor is regenerated to the power supply side to reduce power loss.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to provide a bridge circuit and an inverter device which have low power loss even when switching is performed at a high frequency. It is in.

[0005]

As a bridge circuit according to the first aspect of the present invention, two sets of switch elements in which diodes are connected in anti-parallel are connected in series and connected between the positive and negative DC voltage sources. A half bridge circuit serving as an AC output terminal; and a snubber circuit connecting a capacitor and a second diode in series to each other and connecting the capacitor in parallel to the switch element. One end of the second diode is connected to the switch element. A second switch element connected to the series connection point side and having one end connected to the connection point between the capacitor and the second diode, and a reactor connected between the other end of the second switch element; A third diode is connected between both ends of the reactor and the positive and negative sides of the DC voltage source.

According to a second aspect of the present invention, there is provided a DC voltage source comprising a series connection of a positive side arm and a negative side arm formed by connecting two switch elements in which diodes are connected in anti-parallel to each other. A half-bridge circuit connected between the positive and negative terminals of the first and second terminals and having a series connection point of the positive and negative arms as an AC output terminal;
A fourth diode connected between a series connection point of the two switch elements connected in series and an intermediate potential point of the DC voltage source, and a capacitor and a second diode connected in series. A snubber circuit connected in parallel to each of the switch elements; one end of the second diode of the snubber circuit connected in parallel to the switch element on the AC output end side is connected to an AC output end; A second terminal having one end connected to a connection point between the capacitor and the second diode.
, A reactor connected between the other end of the second switch element, and a third diode connected between both ends of the reactor and the positive and negative sides of the DC voltage source.

[0007] As an inverter device according to the third aspect of the present invention,
A bridge circuit according to claim 1 or 2, connected between the positive and negative sides of the DC voltage source, and outputs an AC voltage between an intermediate potential of the DC voltage source and an AC output terminal of the bridge circuit. I do.

According to a fourth aspect of the present invention, there is provided an inverter device comprising:
At least two bridge circuits according to claim 1 or 2 are connected between the positive and negative DC voltage sources, and a single-phase or multi-phase AC voltage is output between AC output terminals of each bridge circuit. I do.

[0009]

When the switch element is turned on, the bridge circuit according to claim 1 is connected to the switch element and the second diode.
And discharging the charge of the capacitor through the second switch element and the reactor.
Is turned off to regenerate the current flowing through the reactor to the DC voltage source via the third diode.

In the bridge circuit according to the present invention, when the switch element on the AC output end is turned on, the capacitor is connected via the switch element, the second diode, the second switch element, and the reactor. Then, the second switch is turned off, and the current flowing through the reactor is regenerated to the DC voltage source via the third diode.

The inverter device according to the present invention functions as a half-bridge inverter, and outputs an AC voltage between an intermediate potential of a DC voltage source and an AC output terminal of the bridge circuit. The inverter device according to the fourth aspect outputs a single-phase or multi-phase AC voltage between the AC output terminals of each bridge circuit.

[0012]

FIG. 1 shows an embodiment corresponding to claims 1 and 3 of the present invention. In the configuration of FIG. 1, 1 and 2 are DC power supplies connected in series and function as a DC voltage source. 3 and 4 are IG
BT and other self-extinguishing type switch elements
The nodes 5 and 6 are connected in anti-parallel. 7 and 8 are the capacitors of the snubber circuit, 9 and 10 are the second diodes of the snubber circuit,
11 and 12 are second switch elements, and 13 and 14 are third diodes.
, 15 is a reactor, and 16 is a load.

In the above configuration, the DC power supplies 1 and 2 and the load
Circuits other than 16 correspond to the bridge circuit of claim 1 of the present invention, and the entire configuration corresponds to the inverter device of claim 3 of the present invention. In this configuration, the voltage of the E ₁ between the AC output terminal A of the intermediate point B and the bridge circuit of the DC voltage source and the switching element 3 is turned on to output, voltage opposite polarity E ₂ the switch element 4 is turned on Is output. By controlling the switching of these switch elements by pulse width modulation, a desired AC voltage can be output. Such an inverter device is well known as a half-bridge inverter and will not be described in detail. However, the bridge circuit of this embodiment is provided with a new function of regenerating the charged charges of the capacitors 7 and 8 of the snubber circuit. ing.

In the configuration of FIG. 1, when the switch element 3 or 4 is turned on, the capacitor 8 or 7 of the snubber circuit is charged to the voltage E ₁ + E ₂ of the DC voltage source. Therefore, when the switching elements 3 and 4 are alternately turned on, the switching elements are turned on in a state where the capacitors 7 and 8 are charged to E ₁ + E ₂ .

FIG. 2 is a waveform diagram for explaining the operation of the bridge circuit according to the present embodiment, in which each switch element is assumed to be an ideal switch. When the switch element 3 is turned on, the load
16 outputs a voltage of E ₁ to, E ₁ + E ₂ the capacitor 8
At this time, the voltage _{Vc7 of the} capacitor 7 becomes E
₁ + When in the state charged in the E _2, switching element 3 second diode - capacitor 7 in the path of the de 10 second switching element 12 reactor 15 the second switching element 11
Is discharged. This discharge current is
Owing to the resonance of the reactor 15 and the reactor 15, an oscillating current is generated as shown in FIG. Thereafter, when the voltage _{Vc7 of the} capacitor 7 becomes zero, the discharge current of the reactor 15 flows through the second diode 9. When turning off the second switching element 11 at this time t _2, the discharge current i ₀ of the reactor 15 the third diode -
The current is returned to the DC voltage source via the nodes 13 and 14, and the power is regenerated in a short time. Thereafter, the voltage of the load current switching element 3 is turned off is interrupted the load 16 at time t ₃ is zero. At this time, the service due to the stray inductance existing in the main circuit
The voltage is suppressed by the capacitor 7. When the load 16 is inductive, the discharge current diode - via de 6 refluxed, the voltage of the load 16 is a capacitor 7 becomes -E ₂ as indicated by a broken line is charged to E ₁ + E _2. Then, at time t
₄ When the switch element 4 is turned on, the load 16 is output in the reverse polarity voltage E _2, the voltage V _c7 of the capacitor 7 E ₁
+ It is charged to E _2. At this time, the charge of the capacitor 8 is discharged through the path of the second switch element 12, the reactor 15, the second switch element 11, the second diode 9, and the switch element 4. Due to the resonance, the same oscillating current as described above flows. Thereafter, when the voltage _{Vc8 of the} capacitor 8 becomes zero, the discharge current of the reactor 15 flows through the second diode 11. When turning off the second switching element 12 at this time t _5, the third diode discharge current i ₀ of the reactor 15 in the same manner as described above - de 13 a refluxed short time power regeneration to the DC voltage source via a 14 Is done.

As described above, the second switching elements 11 and 12
Operates such that each time the switch element 3 or 4 of the main circuit is turned on, it is turned on only for a period during which the charge of the capacitor 7 or 8 is transferred to the reactor 15. Further, it is possible to output an AC voltage of a sine wave by proceeding up to the time point t ₄ on the switching element 3, a pulse width modulation Repeat off.

FIG. 3 shows an embodiment according to the second and third aspects of the present invention. This embodiment has an energizing mode for clamping the AC output terminal OUT to the intermediate potential point B of the DC voltage source,
A bridge circuit and an inverter device used for a so-called neutral point clamp (NPC) inverter and a three-level inverter. In FIG. 3, reference numerals 21 and 22 denote switch elements in which diodes 23 and 24 are connected in anti-parallel, 25 and 26 are fourth diodes for voltage clamping, and 27 and 28 are first diodes of a snubber circuit. , 29 and 30 are capacitors of the snubber circuit, and 31 and 32 are known power regeneration circuits. Others are the same as those in FIG.

In the above configuration, when the switch elements 21 and 3 are turned on and the switch elements 4 and 22 are turned off, the AC output terminal O
UT becomes the potential at point P. When the switch elements 21 and 3 are turned off and the switch elements 4 and 22 are turned on, the AC output terminal OUT becomes N
It becomes the potential of the point. When the switching elements 21 and 22 are turned off and the switching elements 3 and 4 are turned on, the AC output terminal OUT has the potential at the point B and is clamped at the neutral point of the DC voltage source. By performing the PWM control in the three conduction modes described above, a sine wave AC voltage can be output to the AC output terminal OUT. However, this operation is well known and will not be described in detail, but in the present embodiment, a new function for regenerating the charged charges of the capacitors 7 and 8 of the snubber circuit is provided. Charges in the capacitors 29 and 30 of the snubber circuit are regenerated to the DC voltage source by the power regenerating circuits 31 and 32 when the switch element 21 or 22 is turned on. This circuit is also known and will not be described in detail.

The bridge circuit maintains the switch element 3 in the on state and the switch element 22 in the off state. When the switch elements 21 and 4 repeat on and off in a complementary relationship with each other, the AC output terminal OUT has a P point. And the potential at point B are output alternately, and an output voltage controlled by PWM is obtained.
In this case, the voltage of the capacitor 7 is maintained at zero,
Capacitor 30 is maintained is charged to the voltage E ₂ of the voltage source. Then, the switching element 21 is turned on, and the switching element 4
When is off, the charge of the capacitor 29 becomes zero is regenerated, the capacitor 8 is charged to the voltage E ₁ of the voltage source. Further, the switch element 21 is turned off, when the switch element 4 is ON, the capacitor 29 is charged to the voltage E ₁ of the voltage source, the charge of the capacitor 8 is zero is regenerated. At this time,
The operation of regenerating the charge of the capacitor 8 is performed in the same manner as in the above-described embodiment. That is, when the switch element 4 is turned on, the electric charge of the capacitor 8 is discharged through the second switch element 12-reactor 15-second switch element 11-second diode 9-switch element 4, Thereafter, the energy that has been turned off by the second switch element 12 and moved to the reactor 15 is regenerated to the power supply via the third diodes 13 and 14.

When the switch element 21 is kept off and the switch element 4 is kept on, and the switch element 3 and the switch element 22 are repeatedly turned on and off in a complementary relationship with each other, the point B at the AC output terminal OUT is connected. The potential and the potential at the point N are output alternately, and an output voltage controlled by PWM is obtained.
In this case, the voltage of the capacitor 8 is maintained at zero,
Capacitor 29 is maintained is charged to the voltage E ₁ of the voltage source. Then, the switch element 3 is turned off, and the switch element 22 is turned off.
When is ON, the capacitor 7 is charged to the voltage E ₂ of the voltage source, the charge of the capacitor 30 becomes zero is regenerated. Further, the switch element 3 is turned on, when the switch element 22 is off, the charge of the capacitor 7 becomes zero is regenerated, the capacitor 30 is charged to a voltage source E _2. At this time, the operation of regenerating the electric charge of the capacitor 7 is performed in the same manner as described above.

A PWM having less harmonic components between the AC output terminal OUT of the bridge circuit and the neutral point potential of the DC voltage source.
A controlled AC voltage can be output. FIG. 4 shows an embodiment corresponding to claim 4 of the present invention.

In FIG. 4A, reference numerals 51 and 52 denote the bridge circuits shown in FIG.
And 52 are connected in parallel between the positive and negative sides of the DC voltage source 1, and the load 16 is connected between the AC output terminals A of each bridge circuit.
Device.

In the above configuration, each of the bridge circuits 51, 52
Can output an alternating-current voltage subjected to PWM control with a phase difference of 180 ° to an output terminal A of the DC voltage source 1 to output an AC voltage having a peak value close to the voltage E ₁ of the DC voltage source 1.

In FIG. 4B, reference numerals 61 and 62 denote bridge circuits shown in FIG. 3, which are connected in parallel between the positive and negative DC voltage sources 1 and 2 connected in series, and Neutral point potentials are also connected. The inverter device is configured to connect the load 16 between the AC output terminals OUT of each bridge circuit.

In the above configuration, each of the bridge circuits 61 and 62
Can output an PWM-controlled AC voltage having a phase difference of 180 ° to the output terminal OUT, and can output an AC voltage having a peak value close to the voltage E ₁ + E ₂ of the DC voltage source and having less harmonic components.

FIG. 4 shows an example in which two bridge circuits are used. However, three bridge circuits may be used to output AC voltages having phases different from each other by 120 ° and output three-phase AC voltages. Further, it is possible to output multi-phase AC voltages having different phases of 360 ° / n by using n pieces. According to this embodiment, it is possible to obtain an inverter device in which the power loss of the snubber circuit is small and the conversion efficiency is improved.

[0027]

According to the bridge circuits according to the first and second aspects, most of the charge stored in the capacitor of the snubber circuit is regenerated to the power supply in a short time, and even if switching is performed at a high frequency, power loss is reduced. Can be reduced.

According to the inverter circuit of the third and fourth aspects, even if the PWM control is performed at a high modulation frequency, the power conversion efficiency can be increased, and the operation efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of a bridge circuit and an inverter device according to claims 1 and 3;

FIG. 2 is a waveform chart for explaining the operation of the embodiment.

FIG. 3 is a configuration diagram of an embodiment of a bridge circuit and an inverter device according to claims 2 and 3;

FIG. 4 shows an embodiment of an inverter device corresponding to claim 4, wherein (a) uses the bridge circuit of claim 1 and (b) uses the bridge circuit of claim 2; Indicates the case where

[Explanation of symbols]

1, 2, DC voltage source 3, 4, 21, 22 ... switch element 5, 6, 23, 24 ... diode 7, 8, 29, 30 ... capacitor 9, 10, 27, 28 ... second diode Nodes 11, 12 ... second switch elements 13, 14 ... third diode
15: Reactor 16: Load 25, 26: Fourth diode 31, 32: Power regeneration device 51, 52 ... Bridge circuit 61, 62 of claim 1 ... Bridge circuit of claim 2

Claims (4)

(57) [Claims] 1. A half-bridge circuit having two sets of switching elements having diodes connected in anti-parallel connected in series and connected between the positive and negative DC voltage sources, and having a series connection point as an AC output terminal; a capacitor; A second diode connected in series and connected in parallel to the switch element. One end of the second diode is connected to a series connection point of the switch element. A second switch element having one end connected to a connection point of the diode, a reactor connected between the other ends of the second switch element, and a positive electrode and a negative electrode between the both ends of the reactor and the DC voltage source, respectively. A third diode connected thereto, and when the switch element is turned on, the capacitor is connected via the switch element, the second diode, the second switch element, and the reactor. A bridge circuit for discharging the charge stored in the DC / DC converter and then turning off the second switch element to regenerate a current flowing through the reactor to the DC voltage source via the third diode. . 2. A positive-side arm and a negative-side arm each having two diodes connected in anti-parallel and connected in series and connected in series between the positive and negative DC voltage sources. Positive side arc
A half-bridge circuit having an AC output terminal at a series connection point of the arm and the negative arm, and a half-bridge circuit between the series connection point of the two switch elements connected in series and an intermediate potential point of the DC voltage source, respectively. A fourth diode to be connected, a capacitor and a second
And a snubber circuit connected in parallel to the switch element and connected in parallel to the switch element on the side of the AC output terminal. One end of the second diode of the snubber circuit connected in parallel to the switch element on the AC output terminal side is connected to the AC output terminal. , A second switch element having one end connected to a connection point between the capacitor and the second diode of the snubber circuit, and a reactor connected between the other end of the second switch element. A third diode connected between both ends of the reactor and the positive and negative terminals of the DC voltage source, wherein when the switch element on the AC output end is turned on, the switch element and the second diode are connected; And discharging the charge of the capacitor through the second switch element and the reactor. Then, the second switch is turned off and the current flowing through the reactor is changed to the third current. Diode - bridge circuit, characterized in that the regenerated to the DC voltage source through a de. 3. The bridge circuit according to claim 1 is connected between the positive and negative sides of the DC voltage source,
An inverter device for outputting an AC voltage between an intermediate potential of the DC voltage source and an AC output terminal of the bridge circuit. 4. The bridge circuit according to claim 1, wherein at least two or more bridge circuits are connected between the positive and negative DC voltage sources, and a single-phase or multi-phase circuit is connected between AC output terminals of each bridge circuit. An inverter device for outputting an AC voltage.