JPH10304683A - Inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the circuitry of a control circuit in an inverter device, and improve the distortions of regulation and an output waveform against every load. SOLUTION: In this inverter, the output voltage of a DC-AC conversion circuit 6 is controlled so as to be a constant value, by detecting AC output voltage VOUT supplied to a load 10 by an output voltage detection circuit 12, detecting output current IOUT flowing through current detecting resistors 31, 32 by an output current detection circuit 34, comparing the instantaneous value of a sum-signal V7 of this current detection signal V7 and the reference sine- wave signal VR1 of a reference sine-wave generation circuit 16 with the instantaneous value of the voltage detection signal V1 of the output voltage detection circuit 12 by an instantaneous value comparison circuit 18, and controlling on/off periods of respective MOS-FETs 2 to 5 of the DC-AC conversion circuit 6, based on a compared output signal V8 . It is thus possible to simplify the circuitry of a control circuit 33 and improve the distortions of regulation and the output waveform against every load.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device for converting DC power into AC power, and more particularly to an inverter device which simplifies the circuit configuration of an output control system, regulates all kinds of loads, and improves distortion of an output waveform. Things.

[0002]

2. Description of the Related Art Inverters for converting DC power supplied from a DC power supply such as a battery into AC power have been widely used in uninterruptible power supplies (UPS) used as backup power supplies for electronic and information equipment. It is used. For example, the inverter device shown in FIG.
And first to fourth MOs as four switching elements
S-FETs 2 to 5 are bridge-connected and the first and fourth S-FETs
MOS-FETs 2 and 5 and second and third MOS-FETs
3 and 4 are alternately turned on and off two by two to convert a DC voltage supplied from the DC power supply 1 into an AC voltage.
An AC conversion circuit 6, a filter circuit 9 including a reactor 7 and a capacitor 8, and converting an AC voltage of the DC-AC conversion circuit 6 into a sine wave AC voltage to be supplied to a load 10;
Based on the AC output voltage V _OUT supplied to the load 10, the first and fourth MOS-FETs 2, 5 and the second and third M-FETs
And a control circuit 11 for generating an on-off control signal V _G1 and V _G2 are applied to the gate terminals of the OS-FET3,4 (control terminal).

[0003] The control circuit 11 includes an output voltage detecting circuit 12 to output the voltage detection signal V ₁ by detecting the AC output voltage V _OUT as shown in FIG. 8, the voltage detection signal V ₁ of the output voltage detection circuit 12 the absolute value circuit 13 which outputs the absolute value signal V ₂
And the absolute value signal V ₂ of the absolute value circuit 13 is converted to an AC output voltage V
The mean value circuit 15 composed of the integrating circuit 14 for converting the average value signal V ₃ of _OUT, the reference sine wave generating circuit 16 for generating a reference sine wave signal V _R1 of commercial frequency which defines the voltage value of the AC output voltage V _OUT If a multiplier circuit 17 which outputs a product signal V ₄ between the reference sine wave signal V _R1 of the average value signal V ₃ and the reference sine wave generating circuit 16 of the averaging circuit 15, the output voltage detected is input to the inverting input terminal the instantaneous value comparison circuit 18 for comparing the instantaneous value of the product signal V ₄ of the multiplier circuit 17 to be inputted to the instantaneous value of the voltage detection signal V ₁ of the circuit 12 and the non-inverting input terminal, the reference of the reference sine wave generating circuit 16 instantaneous input a triangular wave oscillator 19 which generates a triangular wave signal V _R2 of very high frequency, the triangular wave signal V _R2 of the triangular wave oscillator 19 is input to the inverting input terminal to the non-inverting input terminal than the frequency of the sine wave signal V _R1 Ratio of value comparison circuit 18 PW compares the output signal V ₅
PWM comparator 20 for generating M modulated signal V _PWM
When a inverter 21 which outputs an inverted signal -V _PWM of the PWM signal V _PWM of the PWM comparator 20, a dead time by an on-off period of the PWM signal V _PWM of the PWM comparator 20 slightly shorter or extend respectively formed and a dead time forming circuit 22 to be output to the second and the gate terminal of the third MOS-FET3,4 the signal as on-off control signal V _G2, the inverted output signal -V _PWM inverters 21 on-off period slightly shorter or extend to form a dead time and the other to output the signal as an on-off control signal V _G1 in the first and the gate terminal of the fourth MOS-FET2,5 respectively And a dead time forming circuit 23. Note that the dead time forming circuits 22 and 23 include the second and third MOS-FETs 3 and
4, when the first and fourth MOS-FETs 2 and 5 are turned on (or turned off), the respective ON / OFF control signals V _G2 ,
Due to the timing shift of V _G1 , the second and third MOS-
This is provided for the purpose of preventing the FETs 3 and 4 and the first and fourth MOS-FETs 2 and 5 from being simultaneously turned on.

The operation of the control circuit 11 shown in FIG. 8 is as follows. In the inverter device shown in FIG.
AC output voltage V _OUT to be supplied are input to the output voltage detection circuit 12 in the control circuit 11, the output voltage detection circuit 12
Detection signal V ₁ of the AC output voltage V _OUT is output from. The voltage waveforms of the voltage detection signal V ₁ of the this time is shown in FIG. 9 (F). The voltage detection signal V ₁ output from the output voltage detection circuit 12 is input to the inverting input terminal of the instantaneous value comparison circuit 18 and to the absolute value circuit 13 in the average value circuit 15. The absolute value circuit 13 outputs an absolute value signal V ₂ of the AC output voltage V _OUT . The absolute value signal V ₂ of the voltage waveform of the AC output voltage V _OUT at this time is shown in FIG. 9 (I). The absolute value signal V ₂ of the AC output voltage V _OUT output from the absolute value circuit 13
Are converted into an average value signal by the integration circuit 14, and the average value signal V ₃ of the AC output voltage V _OUT is output from the average value circuit 15. The average value signal V ₃ of the AC output voltage V _OUT at this time
9 (H) is shown in FIG. The average value signal V ₃ of the AC output voltage V _OUT output from the average value circuit 15 is multiplied by the multiplication circuit 1 together with the reference sine wave signal V _R1 of the reference sine wave generation circuit 16.
7, a product signal V of the average value signal V ₃ of the average value circuit 15 and the reference sine wave signal V _R1 of the reference sine wave generation circuit 16
₄ is output from the multiplication circuit 17. At this time, the reference sine wave signal V _R1 of the reference sine wave generation circuit 16 and the multiplication circuit 17
Figure of the voltage waveform of the product signal V _4, respectively 9 (G) and (J)
Shown in Product signal V ₄ outputted from the multiplier circuit 17 is input to the non-inverting input terminal of the instantaneous value comparison circuit 18, the voltage detection of the output voltage detection circuit 12 that the instantaneous value of the product signal V ₄ is input to the inverting input terminal The signal is compared with the instantaneous value of the signal V ₁ , and the instantaneous value comparison circuit 18 outputs a comparison output signal V ₅ .

The comparison output signal V from the instantaneous value comparison circuit 18
₅ is input to the non-inverting input terminal of the PWM comparator 20 is compared with the triangular wave signal V _R2 of the triangular wave oscillator 19 is input to the inverting input terminal in the PWM comparator 20, compares the output signal V ₅ is PWM-modulated (pulse width modulation) Is done. Inverting input terminal and non-inverting the voltage waveform of the triangular wave signal V _R2 and comparison output signal V ₅ that is input to the input terminal of each diagram of the PWM comparator 20 in this case 9
It is shown in (A). At this time, the PWM comparator 20
FIG. 9 shows the voltage waveform of the _PWM signal V _PWM output from
It is shown in (C). The PWM modulation signal V _PWM of the PWM comparator 20 is directly input to the dead time forming circuit 22,
The PWM signal V _{PWM is generated} by the dead time forming circuit 22.
The on / off period is slightly shortened / extended to form a dead time.
WM modulation signal V _PWM is outputted as an on-off control signal V _G2 to the second and the gate terminal of the third MOS-FET3,4. At this time, the voltage waveform of the on / off control signal _VG2 output from the dead time forming circuit 22 is shown in FIG.
Shown in At the same time, the PW of the PWM comparator 20
The M modulation signal V _PWM is inverted by the inverter 21, and is supplied to another dead time forming circuit 23 by the PWM modulation signal V _PWM.
Inverted signal -V _PWM of is inputted. At this time, inverter 2
PWM-modulated signal V output from 1 Inverted signal -V of _PWM
FIG. 9B shows the voltage waveform of the _PWM . The inversion signal -V _PWM of the PWM modulation signal V _PWM input to the other dead time forming circuit 23 has its on and off periods slightly shortened or extended to form a dead time, and this dead time is formed. and PWM modulation signal V _PWM inverted signal -V _PWM as the on-off control signal V _G1 first and fourth
Are output to the respective gate terminals of the MOS-FETs 2 and 5.
Figure 9 another dead time forming circuit 23 on-off control signal V _G1 of the voltage waveform output from this time (D)
Shown in

The operation of the main circuit of the inverter device shown in FIG. 7 is as follows. Each of the on / off control signals V _G1 shown in FIGS. 9D and 9E output from the control circuit 11,
V _G2 are each DC - AC converter circuit 6 in the first and fourth MOS-FET2,5 second and third MOS-
It is given to each gate terminal of FET3,4. As a result, the first and fourth MOS-FETs 2 and 5 and the second and third MOS-FETs 2 and 3 are alternately turned on and off by two at a frequency which is extremely higher than the commercial frequency and subjected to PWM modulation. . The on / off operation of the first to fourth MOS-FETs 2 to 5 in the DC-AC conversion circuit 6 causes the connection point of the first and second MOS-FETs 2 and 3 to the third and fourth MOS-FETs 4. 5 and 5, an AC voltage having a PWM-modulated commercial frequency is generated. The PWM modulated AC voltage is converted into a commercial frequency sine wave AC voltage by the reactor 7 and the capacitor 8 of the filter circuit 9, and a smooth commercial frequency sine wave AC output having a constant voltage and from which ripple components are removed is loaded. 10 is supplied.

[0007]

[SUMMARY OF THE INVENTION Incidentally, in the conventional inverter apparatus as described above, the average of the AC output voltage V _OUT by the output voltage detection circuit 12 and the averaging circuit 15 in order to stabilize the AC output voltage V _OUT The value is detected and stabilized. Therefore, when the load 10 is a load with a pure resistance having a power factor of 1.0, the regulation (output stability) is very good. However, in practice, the power factor of the load 10 is often 1.0 or less, and the output waveform is distorted, so that the regulation is not always good. Therefore, in the inverter device shown in FIGS. 7 and 8, the instantaneous value of the voltage detection signal V ₁ of the output voltage detection circuit 12 is compared with the average value signal V ₃ of the average value circuit 15 and the reference sine wave generation by the instantaneous value comparison circuit 18. By comparing the instantaneous value of the AC output voltage V _{OUT with} the instantaneous value of the product signal V ₄ of the reference sine wave signal V _R1 of the circuit 16 and controlling the instantaneous value of the AC output voltage V _OUT in accordance with the comparison value, the power factor of the load 10 becomes 1.0. The distortion of the output waveform in the following cases is improved. Therefore, in the case of the inverter device shown in FIGS. 7 and 8, the control system for the average value of the output voltage and the control system for the instantaneous value are provided for the purpose of improving both regulation and distortion of the output waveform for all loads. Circuit 1
There is a disadvantage that the circuit configuration of (1) is complicated.

Accordingly, an object of the present invention is to provide an inverter device which can improve both regulation and distortion of an output waveform with respect to any load by a control circuit having a simple circuit configuration.

[0009]

An inverter device according to the present invention has a DC power supply and at least one switching element, and converts a DC supplied from the DC power supply into an AC by an on / off operation of the switching element. And a control circuit that generates an on / off control signal applied to the control terminal of the switching element based on the output voltage of the DC-AC conversion circuit. The control circuit of the inverter device includes the DC-
An output voltage detection circuit that detects an output voltage of the AC conversion circuit, a reference sine wave generation circuit that generates a reference sine wave signal that defines an output voltage of the DC-AC conversion circuit, and an output current of the DC-AC conversion circuit An output current detection circuit that detects the output voltage as a voltage corresponding thereto, an addition circuit that outputs a sum signal of a reference sine wave signal of the reference sine wave generation circuit and a current detection signal of the output current detection circuit, An instantaneous value comparison circuit for comparing the instantaneous value of the voltage detection signal of the circuit with the instantaneous value of the sum signal of the addition circuit, and the switching element of the DC-AC conversion circuit based on the comparison output of the instantaneous value comparison circuit. By controlling the ON / OFF period of the DC / AC converter, the output voltage of the DC-AC conversion circuit is controlled to a constant value.

The output voltage of the DC-AC converter is detected by the output voltage detector, and the output current flowing through the DC-AC converter is detected by the output current detector as a corresponding voltage. An instantaneous value comparison circuit compares the instantaneous value of the voltage of the sum signal with the reference sine wave signal of the reference sine wave generation circuit and the instantaneous value of the voltage of the voltage detection signal of the output voltage detection circuit. By controlling the ON / OFF period of the switching element of the DC-AC conversion circuit based on the comparison output of the instantaneous value comparison circuit, the DC-
The output voltage of the AC conversion circuit is controlled to a constant value. Therefore, for example, when the current flowing through the load connected to the output side of the DC-AC conversion circuit is large, the instantaneous value of the voltage of the sum signal of the detection signal of the current and the reference sine wave signal also increases. Accordingly, since the comparison output of the instantaneous value comparison circuit also increases, if the ON / OFF period of the switching element is controlled in the direction in which the output voltage of the DC-AC conversion circuit increases based on the comparison output, any load In contrast, the distortion of the output waveform is small and the regulation is good. Therefore, since the control circuit only needs to have a control system for the instantaneous value of the output voltage of the DC-AC conversion circuit, both the regulation and the distortion of the output waveform are improved for all loads by the control circuit having a simple circuit configuration. it can.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the inverter device according to the present invention will be described below with reference to FIGS. However, in these drawings, the same portions as those shown in FIGS. 7 to 9 are denoted by the same reference numerals, and description thereof will be omitted. As shown in FIG. 1, the inverter device of the present embodiment differs from the inverter device shown in FIG. 7 in that a current detection resistor is connected in series with each of the second and fourth MOS-FETs 3 and 5 of the DC-AC conversion circuit 6. 8 are connected to the load 10 and the first to fourth MOS-Fs of the DC-AC conversion circuit 6 instead of the control circuit 11 shown in FIG.
It is connected between each gate terminal of ET2 to ET5. Other configurations are substantially the same as those of the inverter device shown in FIG. The control circuit 33 controls the load 10 as shown in FIG.
An output voltage detection circuit 12 for detecting an AC output voltage V _OUT to be supplied to a reference sine wave generating circuit 16 for generating a reference sine wave signal V _R1 of commercial frequency which defines the voltage value of the AC output voltage V _OUT, An output current detection circuit 34 for detecting an output current of the DC-AC conversion circuit 6 flowing through the current detection resistors 31 and 32 as a corresponding voltage, a reference sine wave signal V _{R1 of} the reference sine wave generation circuit 16 and an output current detection Circuit 34
Adder circuit 3 that outputs a sum signal V ₇ with the current detection signal V _{6 of} FIG.
5, and a momentary value comparing circuit 18 for comparing the instantaneous value of the voltage detection signal V ₁ of the output voltage detecting circuit 12 and the instantaneous value of the sum signal V ₇ of the adding circuit 35. Instantaneous value comparison circuit 18
Since the configuration of the internal circuit after that is substantially the same as that of the control circuit 11 shown in FIG. 8, the description is omitted.

[0012] In the above configuration, the AC output voltage V _OUT to be supplied to the load 10 is detected by the output voltage detection circuit 12 in the control circuit 33, the detection signal V ₁ of the AC output voltage V _OUT is output. The voltage waveforms of the voltage detection signal V ₁ of the this time is shown in FIG. 3 (F). The voltage detection signal V ₁ output from the output voltage detection circuit 12 is input to the inverting input terminal of the instantaneous value comparison circuit 18. At the same time, the output current I _OUT flowing alternately through the current detection resistors 31 and 32 connected in series to the second and fourth MOS-FETs 3 and 5 of the DC-AC conversion circuit 6 is controlled as a corresponding voltage. The detection signal V ₆ of the output current I _OUT is detected by the output current detection circuit 34 in the circuit 33. The voltage waveform of the current detection signal V ₆ at this time is shown in FIG. 3 (I). The current detection signal V ₆ outputted from the output current detecting circuit 34 is added to the reference sine wave signal V _R1 of the reference sine wave generating circuit 16 by the adding circuit 35, the current detection signal V ₆ and the reference of the output current detection circuit 34 Reference sine wave signal V _{R1 of} sine wave generation circuit 16
The sum signal V ₇ is output from the adder circuit 35 with. At this time, the respective voltage waveforms of the reference sine wave signal V _R1 of the reference sine wave generation circuit 16 and the sum signal V ₇ of the addition circuit 35 are shown in FIG.
(G) and (H). Sum signal V ₇ output from the addition circuit 35 is input to the non-inverting input terminal of the instantaneous value comparison circuit 18, the output voltage detection circuit 12 that the instantaneous value of the sum signal V ₇ is input to the inverting input terminal detection signal It is compared with the instantaneous value of V ₁ , and the instantaneous value comparison circuit 18 outputs a comparison output signal V ₈ .

The comparison output signal V from the instantaneous value comparison circuit 18
₈ is input to the non-inverting input terminal of the PWM comparator 20 is compared with the triangular wave signal V _R2 of the triangular wave oscillator 19 is input to the inverting input terminal in the PWM comparator 20, compares the output signal V ₈ is PWM modulated. Showing each voltage waveform of the triangular wave signal V _R2 and comparison output signal V ₈ inputted to the inverting input terminal and non-inverting input terminal of the PWM comparator 20 in this case in FIGS 3 (A). FIG. 3C shows a voltage waveform of the PWM modulation signal V _PWM output from the PWM comparator 20 at this time. P
The PWM modulation signal V _PWM of the WM comparator 20 is directly input to the dead time forming circuit 22, and the dead time is formed by the ON / OFF period of the PWM modulation signal V _PWM being slightly shortened or extended by the dead time forming circuit 22. , The PWM modulation signal V on which the dead time is formed
_{The PWM} is used as the on / off control signal _VG2 as the second and third M
It is output to each gate terminal of OS-FET3,4. At this time, the ON / OFF signal output from the dead time forming circuit 22 is output.
FIG. 3E shows the voltage waveform of the off control signal _VG2 . At the same time, the PWM modulation signal V of the PWM comparator 20
_{The PWM} is inverted by the inverter 21, and the other dead time forming circuit 23 _supplies the inverted signal of the PWM modulation signal V _PWM −
V _PWM is input. FIG. 3B shows the voltage waveform of the inverted signal −V _PWM of the PWM modulation signal V _PWM output from the inverter 21 at this time. Another dead time formation circuit 2
3, the inverted signal of the PWM modulation signal V _PWM -V _PWM
The on / off period is slightly shortened / extended to form a dead time, and the inverted signal −V _{PWM of} the PWM modulation signal V _PWM in which the dead time is formed is used as the on / off control signal V _G1 as the first signal. And fourth MOS-FET
It is output to each of the gate terminals 2 and 5. Another dead time forming circuit on-off control signal V _G1 of the voltage waveform outputted from the 23 at this time shown in Figure 3 (D). The operation of the main circuit of the inverter device shown in FIG.
Since the operation of the main circuit of the inverter device shown in FIG.

In the above-described embodiment, the AC output voltage V _OUT supplied to the load 10 is detected by the output voltage detection circuit 12 in the control circuit 33, and the current detection resistors 31, 3
2, the output current I of the DC-AC converter 6
_OUT is detected by the output current detection circuit 34 in the control circuit 33 as a corresponding voltage, and the current detection signal V ₆
Is added to the reference sine wave signal V _R1 of the reference sine wave generation circuit 16 by the addition circuit 35, and the instantaneous value of the added sum signal V _{7 and} the instantaneous value of the voltage detection signal V ₁ of the output voltage detection circuit 12 are calculated. compared by the instantaneous value comparing circuit 18, a DC based on the comparison output signal V ₈ - the first to fourth AC converter 6
By controlling the ON / OFF period of the MOS-FETs 2 to 5, the output voltage of the DC-AC conversion circuit 6 is controlled to a constant value. Therefore, the output voltage of the DC-AC conversion circuit 6 can be controlled to a constant value for various loads 10 only by the control system of the instantaneous value of the output voltage with little distortion of the output waveform, so that the circuit configuration of the control circuit 33 is simplified. It is possible to improve both regulation and output waveform distortion for all loads 10.

The embodiments of the present invention are not limited to the above embodiments, and various modifications can be made. For example, in the above embodiment, the second and fourth MOS-FETs 3, 5
Current detecting resistors 31 and 32 connected in series to
Has been described, the output current I _OUT of the DC-AC conversion circuit 6 is detected as shown in FIG.
1, 32 are first and third MOS-FETs 2, respectively.
4 connected in series with the output current I of the DC-AC conversion circuit 6.
_OUT may be detected. Further, as shown in FIG. 5, the current detection resistors 31 and 32 are respectively connected to the first and second MOS-MOS transistors.
The output current I _OUT of the DC-AC conversion circuit 6 may be detected by connecting the FETs 2 and 3 in series. Also, as shown in FIG. 6, a current detecting resistor or a current detecting transformer (CT), a Hall element, or the like is provided between the connection point of the third and fourth MOS-FETs 4 and 5 and the capacitor 8 of the filter circuit 9. The current detection means 41 may be connected to detect the output current I _OUT of the DC-AC conversion circuit 6. Of course, in each of the embodiments shown in FIGS. 1, 4 and 5, it is also possible to use a current detecting transformer (CT), a Hall element or the like instead of the current detecting resistors 31 and 32. In the above embodiment, the AC output voltage V _OUT supplied to the load 10 is controlled by the control circuit 3.
Although the form in which the output voltage is detected by the output voltage detection circuit 12 in FIG. 3 has been described, the voltage of the output terminal of the DC-AC conversion circuit 6 may be detected by the output voltage detection circuit 12 in the control circuit 33. In each of the above embodiments, the first and fourth MOS transistors are used.
-The DC-AC converter circuit 6 is configured by a full-bridge type inverter that alternately turns on and off two FETs 2 and 5 and the second and third MOS-FETs 3 and 4 at the same high frequency. First and second MOS-FETs 2, 3
Are alternately turned on and off at a high frequency of several kHz or more, and the third and fourth MOS-FETs 4 and 5 are
The DC-AC conversion circuit 6 may be constituted by a full-bridge type inverter that is turned on and off alternately at a commercial frequency of / 60 Hz. Further, the DC-AC conversion circuit 6 is not limited to the above-described full-bridge type inverter, but may be constituted by a half-bridge type or another type of inverter. Further, a bipolar power transistor, an IGBT (insulated gate field effect transistor), a J-FET (junction field effect transistor), a thyristor, or the like is used as a switching element instead of a MOS-FET (MOS field effect transistor). It is also possible.

[0016]

According to the present invention, the output voltage of the DC-AC conversion circuit can be controlled to a constant value for various loads only by the control system of the instantaneous value of the output voltage with little distortion of the output waveform. With a control circuit having a simple circuit configuration, both regulation and distortion of the output waveform can be improved for all loads.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of an inverter device according to the present invention.

FIG. 2 is a block circuit diagram showing an internal configuration of a control circuit in the inverter device shown in FIG.

FIG. 3 is a waveform chart showing voltages of respective parts in the control circuit of FIG. 2;

FIG. 4 is an electric circuit diagram showing a first modified embodiment of the inverter device of FIG. 1;

FIG. 5 is an electric circuit diagram showing a second modified embodiment of the inverter device of FIG. 1;

FIG. 6 is an electric circuit diagram showing a third modified embodiment of the inverter device of FIG. 1;

FIG. 7 is an electric circuit diagram showing a conventional inverter device.

8 is a block circuit diagram showing an internal configuration of a control circuit in the inverter device shown in FIG.

FIG. 9 is a waveform chart showing voltages of respective parts in the control circuit of FIG. 8;

[Explanation of symbols]

1. . . DC power supply, 2-5. . . First to fourth MOS-
5. FET (switching element); . . 6. DC-AC conversion circuit; . . Reactor, 8. . . Capacitors,
9. . . 10. filter circuit; . . Load, 11. . . Control circuit, 12. . . 12. output voltage detection circuit; . . 13. absolute value circuit; . . 14. integration circuit; . . Average circuit.
16. . . Reference sine wave generation circuit, 17. . . Multiplication circuit,
18. . . Instantaneous value comparison circuit, 19. . . Triangular wave oscillator,
20. . . PWM comparator, 21. . . Inverter, 2
2,23. . . Dead time forming circuit, 31, 3
2. . . Current detection resistor, 33. . . Control circuit, 3
4. . . Output current detection circuit, 35. . . Adder circuit, 4
1. . . Current detection means

Claims (1)

[Claims] A DC-AC conversion circuit having a DC power supply, at least one switching element, and converting a DC supplied from the DC power supply into an AC by an on / off operation of the switching element; A control circuit that generates an on / off control signal to be applied to the control terminal of the switching element based on an output voltage of the AC conversion circuit, wherein the control circuit includes an output voltage of the DC-AC conversion circuit. An output voltage detection circuit for detecting the output voltage of the DC-AC conversion circuit, a reference sine wave generation circuit for generating a reference sine wave signal that defines the output voltage of the DC-AC conversion circuit, and an output current of the DC-AC conversion circuit as a voltage corresponding thereto. An output current detection circuit for detecting, and a sum signal of a reference sine wave signal of the reference sine wave generation circuit and a current detection signal of the output current detection circuit. And an instantaneous value comparison circuit that compares the instantaneous value of the voltage detection signal of the output voltage detection circuit with the instantaneous value of the sum signal of the addition circuit, based on the comparison output of the instantaneous value comparison circuit. An inverter device wherein the output voltage of the DC-AC converter is controlled to a constant value by controlling the ON / OFF period of a switching element of the DC-AC converter.