JP3249295B2 - 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 three-level output bridge circuit and an inverter device.

[0002]

2. Description of the Related Art When converting DC power into AC power by pulse width modulation (hereinafter referred to as PWM), an inverter having a multi-level output is used as an inverter for suppressing harmonic components. FIG. 4 shows a conventional bridge circuit used for the main circuit of this type of conventional inverter device.

FIG. 4 shows the structure of one phase.
Three levels of output voltage can be generated per phase. In the figure, E1 and E2 are DC voltage sources, S11 to S11.
14 is a switch element, D11 to D16 are diodes, and OUT is an output terminal. Also, in the same figure, Cs11 to Cs14
Is a snubber capacitor, Ds11 to Ds14 are snubber diodes, and Rs11 to Rs14 are snubber resistors.

The output voltage at the output terminal OUT of this bridge circuit is the voltage V1 when the switching elements S11 and S12 are on and the switching elements S13 and S14 are off, the switching elements S12 and S13 are on and the switching element S11 When S14 and S14 are off, the voltage becomes V2, and the switching elements S13 and S14
When the switch 14 is on and the switch elements S11 and S12 are off, the voltage becomes V3 and a three-level output is obtained. By performing PWM control on these switch elements, an AC output voltage subjected to PWM control can be obtained as shown in FIG. Also,
At this time, the snubber capacitors Cs11 to Cs14 are connected to the snubber diode when the switch elements S11 to S14 are in the off state.
Is charged to E1 or E2 through the nodes Ds11 to Ds14,
As shown by Vcs11 to Vcs14 in FIG. 5, any two snubber capacitors are charged to the voltage of the DC voltage source. When each of the switch elements S11 to S14 is turned on, it is discharged through the snubber resistors Rs11 to Rs14, and when the charging voltage of one snubber capacitor becomes zero,
That amount is borne by another snubber capacitor.

[0005]

In the above-described bridge circuit of the prior art, each time the switch element is turned on, the charge stored in the snubber capacitor is consumed as heat by the snubber resistor and the PWM is applied.
When the control modulation frequency is increased, there is a problem that the power loss increases because the number of times of charging and discharging of the snubber capacitor increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and even if the modulation frequency of PWM control is increased,
An object of the present invention is to provide a bridge circuit and an inverter device in which power loss does not increase so much.

[0007]

Means for Solving the Problems As a first aspect of the present invention,
A positive arm and a negative arm are connected in series between two switch elements in which a first diode is connected in anti-parallel, and the positive arm is connected between the positive and negative DC voltage sources. The connection point between the negative arm and the negative arm is an AC output terminal, and the positive arm and the negative arm
A second diode for voltage clamping connected between an intermediate point of two series-connected switch elements of the system and an intermediate potential point of the DC voltage source, and a capacitor and a third diode. And a third diode of the snubber circuit connected in series to each of the two switch elements connected in series, and a snubber circuit composed of a series circuit of A first resistor connected between a connection point of the capacitor of the snubber circuit connected to the third switching element and the third diode and the intermediate potential, and a switching element connected to the AC output terminal side. A bridge circuit having a series circuit of a second resistor and a fourth diode respectively connected between the connection point of the capacitor of the snubber circuit and the third diode and the positive and negative of the DC voltage source; That. According to a second aspect of the present invention, there is provided an inverter device that includes at least two or more of the above-described bridge circuits and outputs single-phase or multi-phase AC power.

[0008]

According to the first aspect of the present invention, the capacitor of the snubber circuit connected to the switch element on the DC voltage source side is always charged to a predetermined voltage, and the surge voltage when the switch element is turned off is absorbed. The increasing charge charge is the first
And is maintained at a predetermined voltage through the above-mentioned resistor. The capacitor of the snubber circuit connected to the switch element on the side of the AC output terminal is charged to a predetermined voltage when the two switch elements of the opposing arm connected in series are turned on, and when the switch element is turned off. The charge that increases by absorbing the surge voltage of
Is discharged to the DC voltage source via the second resistor and the fourth diode, and when the two serially connected switch elements of the arm are turned on, the second resistor and the fourth diode are used. Then, the battery is discharged to the DC voltage source and the charging voltage becomes zero. According to a second aspect of the present invention, a single-phase or multi-phase AC voltage having a predetermined frequency is output between AC output terminals of each bridge circuit.

[0009]

FIG. 1 shows an embodiment of a bridge circuit according to claim 1 of the present invention. FIG. 1 shows the configuration of a bridge circuit for one phase, which outputs three levels of voltage.

In FIG. 1, a DC voltage source comprises two DC voltage sources E1 and E2 connected in series, and a first diode
A positive-side arm (S11, S11, D14) is formed by connecting two switch elements S11-S14 connected in series in anti-parallel with each other.
S12, D11, D12) and the negative arm (S13, S14, D13,
D14), the positive arm and the negative arm are connected in series between the positive and negative DC voltage sources, and the connection point between the positive arm and the negative arm is an AC output terminal OUT. A second diode D15 for voltage clamping is provided between an intermediate point of two serially connected switch elements of a positive arm and a negative arm and an intermediate potential V2 of the DC voltage source. Connect D16.

A snubber circuit formed by connecting capacitors Cs11 to Cs14 and a third diode Ds11 to Ds14 in series is connected in parallel to each of the switch elements S11 to S14, and two switch elements S11 are connected in series. , S12 and the third diode of the snubber circuit connected to S13, S14
Ds11 and Ds12 and Ds13 and Ds14 are connected in series. Also, the switching elements S11, S14 on the DC voltage source side
Of the snubber circuit connected to the 3rd diode
The first resistors Rs11 and Rs14 are respectively connected between the connection point of the node and the intermediate potential V2, and the capacitor of the snubber circuit connected to the switch elements S12 and S13 on the side of the AC output terminal OUT and the third diode are connected. And the fourth resistor Ds12, Rs13 between the connection point of the DC voltage source and the fourth diode Ds.
15 and Ds16 are connected in series.

In the above configuration, when the switch elements S11 and S12 are turned on and the switch elements S13 and S14 are turned off as shown in FIG.
Is output, the switching elements S12 and S13 are turned on, and when the switching elements S11 and S14 are in the off state, the voltage V2 is output, and the switching elements S13 and S14 are turned on and the switching element S
When V11 and S12 are off, the voltage V3 is output, and a three-level output is obtained. By performing PWM control on these switch elements at a high modulation frequency, a sine wave AC output voltage can be obtained.

Further, the switching elements S11 and S12 are turned on,
When S13 and S14 are off, capacitors Cs13 and Cs
14, the voltage E1 + E2 of the DC voltage source is applied in series,
When the switch elements S13 and S14 are turned on and S11 and S12 are off, the voltage E1 + E2 of the DC voltage source is applied to the capacitors Cs11 and Cs12 in series. When the switch elements S12 and S13 are turned on and S11 and S14 are turned off,
The capacitors Cs11 and Cs14 have a voltage E1 +
E2 is applied in series.

When the voltages V1 and V2 are alternately and repeatedly output to the AC output terminal OUT, the capacitors Cs11 and Cs11
S13 and Cs14 are charged to a predetermined voltage determined by the voltage of the DC voltage source, and this state is shown in the positive mode period in FIG. Also, when the voltages V2 and V3 are alternately and repeatedly output to the AC output terminal OUT, the capacitors Cs11, Cs12, Cs
S14 is charged to a predetermined voltage determined by the voltage of the DC voltage source, and this state is shown in the negative mode period of FIG. This figure 2
As shown in (1), the capacitors Cs11 and Cs14 are always charged to a predetermined voltage.

When the switching elements S11 and S12 are turned on and S13 and S14 are turned off, if the charging voltage of the capacitor Cs11 is higher than the voltage E1, a DC voltage source E1 is connected via a resistor Rs11.
And is maintained at the voltage of E1. Therefore, when the switch element S11 is turned off, a part of the charged electric charge of the capacitor Cs11 which is increased by absorbing the surge voltage generated between the anode and the cathode is regenerated to the DC voltage source.

The switching elements S13 and S14 are turned on,
When S11 and S12 are turned off, the capacitor Cs14 is maintained at the voltage of E2 in the same manner as described above. Switch element S12
When S13 and S13 are turned on and S11 and S14 are turned off, if the charging voltage of the capacitor Cs12 is higher than E1, a discharging current flows to the DC voltage source through the series circuit of the resistor Rs12 and the diode Ds15, The charging voltage is kept below E1. Similarly, the charging voltage of the capacitor Cs13 is maintained at E2 or lower.

Further, the switching elements S11 and S12 are turned on,
When S13 and S14 are turned off, if there is a charge in the capacitor Cs12, the charge is discharged to the DC voltage source E1 via the resistor Rs12 and the diode Ds15, and a part of the charge is regenerated to the DC voltage source. The charging voltage becomes almost zero.

The switch elements S13 and S14 are turned on, and S
When 11 and S12 are turned off, the charging voltage of the capacitor Cs13 becomes substantially zero as described above. When the voltages V1 and V2 are repeatedly output to the AC output terminal OUT by the operation described above, as shown in the positive mode period of FIG.
Voltages Vcs11, Vs of capacitors Cs11, Cs13, Cs14
cs13 and Vcs14 are substantially maintained at the voltages of E1 and E2,
The voltage Vcs12 of the capacitor Cs12 becomes zero. Also, V
When the voltages 2 and V3 are repeatedly output, as shown in the negative mode period of FIG. 2, Vcs11, Vcs12, and Vcs14 are output.
Is maintained substantially at E1 and E2, and Vcs13 becomes zero.

According to the present embodiment, every time each switch element is turned on, the charge stored in the snubber capacitor is not consumed as power loss, and P
Even if WM control is performed, power loss can be reduced.

FIG. 3 shows an embodiment of an inverter device according to a second aspect of the present invention. In FIG. 3, reference numerals 3 and 4 represent FIG.
Wherein the voltages V1, V2, V3 of the DC voltage sources 1, 2 are applied to the terminals V1, V2, V3,
Three levels of voltages V1, V2, V
3 is output. Reference numeral 6 denotes an inverter control unit for outputting signals Su, Sv, Sw for controlling the bridge circuits 3 to 4 by PWM.

In the above configuration, when the inverter control section 6 outputs the PWM signals Su, Sv, Sw for turning on and off the switch elements S11 to S14 of each of the bridge circuits 3 to 4, it outputs the PWM signals Su, Sv, Sw. A PWM signal is output at a high modulation frequency so that the voltage output from the AC output terminal OUT becomes a sine wave voltage having a phase difference of 120 °.
Thereby, a high-quality three-phase AC voltage can be output. Note that it is also possible to output a single-phase AC voltage by using two bridge circuits, and various modifications can be made.

[0022]

According to the first aspect of the present invention, the DC voltage is P
When converting to an AC voltage by WM control, even if PWM control is performed by increasing the modulation frequency, a bridge circuit with reduced power loss and improved conversion efficiency can be provided.

According to the second aspect of the present invention, there is provided an inverter device which performs PWM control of the bridge circuit at a high modulation frequency, outputs a high-quality single-phase or multi-phase AC voltage, and has an improved conversion efficiency. Can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of a bridge circuit according to claim 1 of the present invention.

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

FIG. 3 is a configuration diagram of an embodiment of an inverter device according to claim 2 of the present invention.

FIG. 4 is a configuration diagram of a conventional bridge circuit.

FIG. 5 is a time chart for explaining the operation of the conventional bridge circuit.

[Description of Signs] E1, E2 DC voltage sources S11 to S14 Switching elements D11 to D14 (first) diodes D15 and D16 (second) diodes Ds11 to Ds14 (third) ) Diodes Ds15, Ds16 ... (fourth) diodes Cs11 to Cs14 ... capacitors Rs11, Rs14 ... (first) resistors Rs12, Rs13 ... (second) resistors 1,2 ... DC voltage sources 3 to 5. Bridge circuit of the present invention 6. Inverter control unit

Claims (2)

(57) [Claims] 1. A positive-side arm and a negative-side arm comprising two series-connected switch elements in which a first diode is connected in anti-parallel.
The positive arm and the negative arm are connected in series, and the connection point between the positive arm and the negative arm is used as an AC output terminal, and two of the positive arm and the negative arm are connected in series. A second diode for voltage clamp connected between an intermediate point of the connected switch element and an intermediate potential point of the DC voltage source;
A snubber circuit composed of a series circuit of a capacitor and a third diode is connected in parallel to the switch element, respectively, and the third diodes of the snubber circuit connected to two switch elements connected in series are connected in series. A first resistor connected between a connection point of the capacitor of the snubber circuit connected to the switch element on the DC voltage source side and a third diode and the intermediate potential, and an AC output terminal. A series connection of a second resistor and a fourth diode respectively connected between the connection point of the capacitor of the snubber circuit connected to the switch element on the side and the third diode and the positive and negative of the DC voltage source. A bridge circuit comprising a circuit. 2. An inverter device comprising at least two or more bridge circuits according to claim 1, and outputting single-phase or multi-phase AC power.