JP3220291B2 - 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 an inverter for converting a DC voltage into an AC voltage. Specifically, the present invention relates to a configuration of a control device that performs PWM control of an inverter. Inverter devices for converting DC power to AC power have been developed in response to the development of switching semiconductor elements. In particular, there is an increasing demand for inverters that receive commercial AC power and include a battery for backup during a power failure, that is, UPS. Inverter semiconductor switch,
Although the cost of a power conversion unit such as a transformer and a capacitor increases and decreases in proportion to the output capacity, the control unit that controls the power conversion unit is almost constant without affecting the output capacity. That is,
An inverter having a smaller output capacity has a higher proportion of the cost occupied by the control unit in the entire device. Therefore, in a small-capacity inverter or UPS, reduction of the cost of the control unit is a major problem. The present invention aims at simplifying the configuration while suppressing a decrease in the function and performance of the control unit, and reducing the cost, improving the reliability, miniaturizing the device, and the like. The PWM signal that drives a conventional switching semiconductor element senses the output voltage of the inverter, compares it with a reference sine wave signal, creates a signal that compensates for the error, and matches this signal with a high-frequency triangular wave signal. I was getting it. In the present invention, a PWM pattern corresponding to the above-described PWM signal is created in advance, stored in a semiconductor memory, and mounted in a control unit. At the time of the operation of the inverter, the contents of the memory are read out repeatedly in a time-series manner and processed to obtain drive signals.

[0002]

2. Description of the Related Art FIG. 6 shows a configuration example of a conventional inverter device. Although a single-phase inverter is shown as an example, a three-phase inverter is also commonly used. E _DC in FIG. _6A is a DC power supply input to the inverter device. 1 is a DC-DC converter, 2 is a DC-AC converter, 3 is an AC filter ,
4 the load, 5 is a control circuit of the transistor Q ₁ to Q _4. Thus, the DC-DC converter converts the DC input voltage to a required level,
Output to N. C _DC is a capacitor. The transistors Q _{1 to} Q _{4 form} a bridge inverter circuit (hereinafter, referred to as an inverter circuit) which is a DC-AC converter. Diodes D _{1 to} D ₄ provided in antiparallel to the transistors Q _{1 to} Q ₄ are provided for regenerating reactive power on the AC output side of the inverter circuit. L _AC and C _AC are a reactor and a capacitor constituting an AC filter,
PWM (Pulse Width Modula) generated in the inverter circuit
pulsation width modulation) Attenuates harmonic components from the voltage V _PWM and outputs a sine wave AC voltage V _OUT . L is an AC load. PT is a transformer for sensing the output AC voltage V _OUT . CONT is the transistors Q _{1 to} Q
₄ is a control device for generating a drive signal for controlling the on / off of ₄ . In FIG. 6A, the input is described as DC, but the case where AC power is input is also generally used. This is shown in FIG. A DC voltage obtained by controlling the power of the AC power supply E _{AC to} a constant voltage by an AC-DC converter (commonly known as a rectifier) is output to PN. Figure 6 after PN
The configuration is the same as (a).

FIG. 7 shows a circuit configuration (a) of the control device CONT.
And the operation waveform (b). In the figure, 6 is an error amplifier, 7 is a comparator, 8 is a triangular wave generator, and 9 is a distributor. The output voltage V _OUT of the inverter device is extracted via the sensing transformer PT, and this signal ES is input to one of the error amplifiers 6 and the other is supplied with a reference sine wave voltage signal E _R. The output of the error amplifier 6 obtains E _OUT in which a signal obtained by amplifying a difference between two inputs on the reference sine wave voltage signal E _R is superimposed. E _OUT = E _R + (E _R −E _S ) × R ₂ / R _{1 When} the output voltage of the inverter device fluctuates, the waveform of the superimposed signal E _OUT changes so as to correct it. The triangular wave generator generates a high frequency triangular wave b. The frequency at which the transistors Q _{1 to} Q ₄ of the inverter circuit are switched is
It is determined by the frequency of the triangular wave signal b. When the signal E _OUT and the triangular wave signal b are given to the comparator, the signal E _OUT
Outputs a PWM signal c which is at a high level during a period in which the level is higher than the signal b and becomes a zero level in other periods. A PWM signal c is input to a distributor, and a drive signal d which is amplified and, if necessary, insulated, and a N signal of the signal d
A drive signal e corresponding to OT is obtained. The signal d drives the transistors Q ₁ and Q ₄ of the inverter circuit, and the signal e drives the transistors Q ₂ and Q ₃ . Each transistor Q ₁ ~Q ₄ is the drive signal that has been given high
Level and turns off during the zero level, and the DC voltage of the capacitor C _DC (FIG. 6) is changed to the AC PW
Convert to M voltage V _PWM . When this V _PWM voltage is applied to the AC filters L _AC and C _AC , the high-frequency component is removed and a sine wave voltage V _OUT corresponding to the reference sine wave signal a is output. In this conventional device, the transistors Q _{1 to} Q
The configuration of the control device CONT for controlling the control device ₄ is complicated, which causes a decrease in reliability and an increase in cost. In a motor drive inverter, a method of storing a PWM control pattern in a semiconductor memory and sequentially reading the pattern to generate a PWM voltage waveform has been proposed. This method is effective when the PWM voltage is directly supplied to the motor. However, in the inverter that supplies the power to the load after shaping the generated PWM voltage into a sine wave voltage through an LC filter as in the present invention, Natural vibration of LC filter (1
/ √LC is superimposed on the sinusoidal voltage at a free oscillation occurring at a frequency corresponding to LC), so that the same method cannot be put to practical use.

[0004]

SUMMARY OF THE INVENTION The present invention has been proposed in order to improve the above-mentioned drawbacks. The object of the present invention is to simplify a control device constituting an inverter device and to improve reliability and reduce costs. It is to plan.

[0005]

In order to achieve the above object, the present invention relates to an apparatus for receiving DC power and converting the DC power into an AC voltage having a desired frequency by a DC-AC converter and an AC filter. AC converter P
A control device that generates a drive signal for performing WM switching control is configured by dividing a half cycle of an output voltage into n sections from 1 to n, and arranging a pulse in each of the divided sections. A semiconductor memory in which a PWM pattern is made so that addresses 1 to n correspond to the sections from 1 to n, and the width of a pulse arranged in each section is stored at each corresponding address as m-bit parallel data; M bits stored at addresses 1 to n. A PWM signal converter for sequentially reading parallel data and converting the read m-bit parallel data into m-bit serial data to read a PWM signal, and a distribution circuit for converting the converted PWM signal into a drive signal. SUMMARY OF THE INVENTION The gist of the present invention is an inverter device characterized by the above configuration. Further, the present invention relates to a device for converting a DC voltage into an AC voltage having a desired frequency by a DC-AC converter and an AC filter. As a device for obtaining the DC voltage, the device receives AC power and converts the DC voltage to a desired level. Or a DC-DC converter that receives DC power and converts it to a desired level of DC voltage.
A control for controlling the input voltage of the AC converter to a constant voltage or controlling a voltage level corresponding to the output current, and generating a drive signal for PWM switching control of the DC-AC converter; The equipment is
A PWM pattern formed by dividing a half cycle of the output voltage into n sections from 1 to n and arranging pulses one by one in each of the divided sections is represented by an address 1 to n and a section from 1 to n. , And the width of a pulse arranged in each section is stored as m-bit parallel data at each corresponding address, and the m-bits stored at addresses 1 to n from this memory. A PWM signal converter for sequentially reading parallel data and converting the read m-bit parallel data into m-bit serial data to read a PWM signal, and a distribution circuit for converting the converted PWM signal into a drive signal. SUMMARY OF THE INVENTION The gist of the present invention is an inverter device characterized by the above configuration.

[0006]

The present invention relates to a DC-AC converter having a PW
By configuring a control device that generates a drive signal for performing M switching control with a memory that stores a PWM pattern and a distribution circuit that converts a signal obtained by reading this memory in time series into a drive signal, The control device of the inverter is greatly simplified and downsized, and the cost can be reduced.

[0007]

Next, an embodiment of the present invention will be described. FIG.
Is a first configuration example of the inverter device of the present invention. FIG.
, The control device CONT outputs the output voltage V _OUT
Did not feedback. In the figure, E _DC is a DC power supply, 1 is a DC-DC converter, 2 is a DC-AC converter, 3 is a filter, 4 is a load, and 5 is a control circuit. The input-side DC-DC converter controls the voltage of the output terminal PN to a constant voltage, or controls the voltage level according to the output current. For example, a voltage drop that changes in proportion to the output current by inserting a small resistor R is sensed and controlled so that the voltage increases in proportion to the current. Also, P
The currents of the N terminal is increased is when the output of the inverter is increased, the voltage drop at this time the transistor Q ₁ to Q ₄ and the reactor L _AC is increased in proportion to the current, the voltage drop amount The DC voltage at the PN terminal is increased to compensate. As a result, the output voltage V _OUT of the inverter device can be kept substantially constant without feeding back the output voltage of the inverter device to the control device CONT. If the DC voltage supplied from the outside is at a desired level and quality as an input to the inverter, the DC power supply E
Power is supplied directly from _DC to the terminal PN. Although an example is shown in which bipolar transistors are used as the switching elements Q _{1 to} Q ₄ of the inverter circuit, this is merely an example, and other semiconductor switches, such as power MOSFETs and IGs, are used.
BT (Insulated Gate Bipolar Transistor) can also be used. Also, a full-bridge inverter using four transistors is shown as an inverter circuit, but a half-bridge inverter using two transistors or a three-phase bridge inverter using six transistors as in the conventional inverter device. It goes without saying that it can also be used.

FIG. 2 shows a control unit CONT applied to the present invention.
The following shows an example. In the figure, 10 is a semiconductor memory, 1
1 denotes a PWM signal converter, and 12 denotes a distributor. In the semiconductor memory M, a PWM pattern is stored in an area of n addresses × m bits (D1 to Dm). The PWM signal converter converts the m-bit parallel data read from the memory M into m-bit serial data. Here, m PWM pattern arrangements can be selected from the m-bit data. As shown in FIG. 3, a half cycle of the output voltage of the inverter device is divided into 1 to n, and the output voltage is sinusoidal for each time division. The pulse pattern arrangement of 1 to m is distributed so as to have a wave half cycle. That is, the correspondence with the pattern C in FIG.
Then , the pulse closest to the pulse width of the pattern C is selected and arranged from the pulses 1 to m in FIG. 3 for each section. The pulse train obtained in this manner is used as a signal C in FIG. 4 (signal C in FIG. 7).
). That is, 1 out of m patterns
Take one. The arrangement of the selected patterns becomes the PWM signal C. Drive signal d, e by applying PWM signal C to distributor
Create As is generally used, in the distributor, the input and output are insulated by a photocoupler as needed, and the signal is amplified to amplify the signal of the transistor Q _{1 of the} inverter circuit.
To drive the ~Q _4. When the present invention is applied to a three-phase inverter, three sets of signals whose phases are shifted by 120 degrees are created as the PWM signal C, and each set is processed into a drive signal by a distributor and used.

A microcomputer circuit can be applied to the PWM signal converter, as is generally used. FIG. 5A shows an example using a one-chip microcomputer circuit. The ROM of the microcomputer circuit corresponds to the memory M in FIG. This ROM has a program and PWM for one cycle of the inverter output waveform.
Signal data is stored as data in which ON / OFF for each unit time (minimum pulse width) is represented by 1 and 0. This data is created by the number of bits corresponding to the number of transistors of the inverter circuit (for example, 4 bits for a single-phase inverter and 6 bits for a three-phase inverter). After the data is read out in chronological order, it is ANDed with the signal generated by the external interrupt processing,
Only during the period when the interrupt signal shown in FIG. 5B is input, the pulses are cut off from the pulses Q _{1 to} Q ₄ read from the memory as shown by the broken lines, and the signals C _{1 to} C ₄ are output from the output port of the microcomputer. Is output as The signals C _{1 to} C ₄ are amplified or insulated through the distributors, respectively, and used as drive signals for the transistors Q _{1 to} Q ₄ . Note that the necessary number of bits is not limited to the case where a signal corresponding to each transistor is formed by forming a logic circuit externally as shown in FIG. For example, in the case of a single-phase inverter, one bit may be used.

[0010] Further, for the prevention of a short circuit of the DC power supply described below, data corresponding to each transistor can be provided with data that is kept off for a minimum unit time. In the inverter circuit of FIG. 1, transistors, for example, Q ₁ and Q ₂
Are turned on at the same time, a DC power supply (DC-DC converter) is short-circuited, and an overcurrent flows through the DC power supply and the transistor, which is damaged. On the other hand, in a transistor, a delay occurs between a given drive signal and a switching operation caused by the drive signal. Therefore,
In order to prevent the transistor from being damaged by overcurrent, a method of providing a time lag from when an off signal is applied to one of the transistors connected in series to when an on signal is applied to the other transistor is used. In FIG. 2, the distributor has this pulse shaping function. FIG. 4 shows the operation of pulse shaping. NOT the signal C obtained by inverting the phase of the PWM signal C
We make with circuit. On the other hand, the signal C _{D which} is delayed from the PWM signal C
Is made with the integration circuit of the resistor and the capacitor and the amplifier. A signal C _{D obtained} by inverting the phase of the signal C _D is generated by a NOT circuit.
Provides a signal C and C _D the AND circuit 1, the output signal d
And Moreover, given the signal C and C _D the AND circuit 2, making the signal e. Here, C is a signal obtained by inverting C, and C _D is a signal obtained by inverting C _D. There is a gap between the signals d and e due to the delay time due to the integration circuit. Even if there is a switching delay in the transistor, if the gap time is longer than this delay time, an accident of short-circuiting the DC power supply can be avoided. .

Next, the interrupt processing will be described. AN
A high level voltage H is always supplied to the D circuits 1 and 2 as a third input. When the output of the inverter device becomes abnormal, for example, when the output current becomes overcurrent due to a short circuit accident of the load L, or when the output voltage _VOUT becomes overvoltage due to abnormal operation of the inverter circuit (separately, the sensor The level of this third input is changed from H to zero level. That is, interrupt processing is performed. Thereby, the output signals d and e of the AND circuits 1 and 2 are obtained.
There both zero-level, forcibly shut off the transistors Q ₁ to Q ₄ of the inverter circuit. The forced cutoff of the transistor protects the inverter device from a short circuit accident of the load L and protects the load L from an accident of the inverter device.

[0012]

As described above, according to the present invention, the control device of the inverter device is greatly simplified and downsized. This has the effect of improving the reliability of the control device and reducing costs. Since the control device needs to have a certain scale irrespective of the power capacity to be converted by the inverter device, even a small-capacity inverter device requires the same control device as a large-capacity device. Therefore, the ratio of the control device to the reliability and cost of the inverter device having a smaller power capacity increases. This indicates that the effect of the present invention increases as the inverter device has a smaller power capacity. Further, in the inverter device having a small power capacity, the ratio of the physical size occupied by the control device also increases, so that the present invention is also effective for downsizing the inverter device. Further, even if the voltage control device lacks the function of output voltage control, the inverter device itself can be protected from a load short-circuit accident and the load can be protected from the inverter device accident.

[Brief description of the drawings]

FIG. 1 shows a configuration of an inverter device according to a first embodiment of the present invention.

FIG. 2 shows an embodiment of a control device applied to the present invention.

FIG. 3 shows m patterns.

FIG. 4 shows a time chart of a signal.

5A and 5B show control by a microcomputer, FIG. 5A shows a circuit configuration, and FIG. 5B shows an output signal of each transistor.

6A and 6B show a configuration of a conventional inverter device, wherein FIG. 6A shows one embodiment and FIG. 6B shows another embodiment.

7A and 7B show a control device for controlling a conventional inverter device, FIG. 7A is a configuration diagram, and FIG. 7B is a time chart of each signal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DC-DC converter 2 DC-AC converter 3 Filter 4 Load 5 Control circuit 6 Error amplifier 7 Comparator 8 Triangular wave generator 9 Divider 10 Memory 11 PWM signal converter 12 Divider

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tadahisa Nakajima 1-15-1 Kita-Otsuka, Toshima-ku, Tokyo Inside Sanyo Denki Co., Ltd. (72) Inventor Yoshiaki Kobayashi 1-1-15 Kita-Otsuka, Toshima-ku, Tokyo No. 1 Yamayo Denki Co., Ltd. (72) Inventor Seiichi Muroyama 1-1-6 Uchisaiwai-cho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Suzuki No. 6 Nippon Telegraph and Telephone Corporation (72) Inventor Masayuki Aoki 1-23-11 Sengoku, Bunkyo-ku, Tokyo Shinano Electric Co., Ltd. (56) References JP-A-58-112471 (JP, A) JP-A Sho 59-172979 (JP, A) JP-A-59-213285 (JP, A) JP-A-5-114473 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02M 7/48 G05F 1/10

Claims (4)

(57) [Claims] An apparatus for receiving DC power and converting the DC power into an AC voltage having a desired frequency by a DC-AC converter and an AC filter, wherein a control signal for generating a drive signal for performing PWM switching control of the DC-AC converter is provided. The device divides a half cycle of the output voltage into n sections from 1 to n, and arranges a PWM pattern formed by arranging pulses one by one in each of the divided sections. n, a semiconductor memory in which the width of a pulse arranged in each section is stored at each corresponding address as m-bit parallel data, and m bits stored at addresses 1 to n from this memory. A PWM that sequentially reads parallel data and reads a PWM signal by converting the read m-bit parallel data into m-bit serial data.
An inverter device comprising: a signal converter; and a distribution circuit that converts the converted PWM signal into a drive signal. 2. A DC-AC converter comprising:
A device for converting an AC voltage of a desired frequency by a C filter, as an apparatus for obtaining the DC voltage, an AC-DC converter for receiving AC power and converting the AC power to a DC voltage of a desired level, or receiving DC power The DC-DC converter for converting this to a desired level of DC voltage is
A small resistor for controlling the input voltage of the C-AC converter to a constant voltage or for controlling the voltage level corresponding to the output current is provided, and generates a drive signal for performing PWM switching control of the DC-AC converter. The control device divides a half cycle of the output voltage into n sections from 1 to n, and arranges a PWM pattern formed by arranging pulses one by one in each of the divided sections. To n, the width of the pulse arranged in each section is stored as m-bit parallel data at each corresponding address, and the m bits stored at addresses 1 to n from this memory. A PWM that sequentially reads parallel data and reads a PWM signal by converting the read m-bit parallel data into m-bit serial data.
An inverter device comprising: a signal converter; and a distribution circuit that converts the converted PWM signal into a drive signal. 3. The inverter device according to claim 1, wherein the distribution circuit has an interrupt function of stopping an output of the drive signal in response to an external signal. 4. The PWM signal converter is constituted by a microcomputer (microcomputer), and an interrupt function for stopping output of a drive signal in response to an external signal is provided by an interrupt processing function of the microcomputer and software. The inverter device according to claim 1, wherein the inverter device is provided.