JPH06351256A - Inverter - Google Patents

Abstract

PURPOSE:To significantly simplify and downsize the controller for inverter and to reduce the total cost. CONSTITUTION:The inverter for inverting a DC voltage EDC into an AC voltage of desired frequency through a DC-DC converter 1, a DC-AC converter 2 and an AC filter 3 comprises a controller 5 for the DC-AC converter 2, a pulse memory storing a PWM pattern, and a distribution circuit for converting the signals read out in time series from the memory into drive signals.

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 voltage into AC voltage. Specifically, it relates to the configuration of a control device that PWM-controls an inverter. Inverter devices for converting DC power into AC power have been developed in response to the development of semiconductor elements for switching. In particular, there is an increasing demand for inverters that receive commercial AC power and that have a battery for backup in the event of a power failure, that is, UPS. Inverter semiconductor switch,
The cost of the power conversion unit such as the transformer and the capacitor increases or decreases in proportion to the output capacity, but the control unit that controls the power conversion unit does not affect the output capacity and is substantially constant. That is,
The lower the output capacity of the inverter, the higher the cost ratio of the control unit in the entire device. Therefore, in the case of a small capacity inverter or UPS, reducing the cost of the control unit becomes a major issue. The present invention aims to reduce the cost, improve the reliability, and downsize the device while simplifying the configuration while suppressing the deterioration of the function and performance of the control unit. The PWM signal that drives the conventional switching semiconductor element senses the output voltage of the inverter, compares it with the reference sine wave signal, creates a signal that compensates for the error, and matches this with the high frequency triangular wave signal. I was getting it. In the present invention, a PWM pattern corresponding to the PWM signal is created in advance, stored in a semiconductor memory, and mounted in the control unit. During operation of the inverter, the contents of this memory are repeatedly read out in time series and processed into drive signals.

[0002]

2. Description of the Related Art FIG. 6 shows a configuration example of a conventional inverter device. A single-phase inverter is shown as an example, but a three-phase inverter is also commonly used. E _DC in FIG. _6A is a DC power source input to the inverter device. 1 is a DC-DC converter, 2 is a DC-AC converter, 3 is a direct current filter,
Reference numeral 4 is a load, and 5 is a control circuit for the transistors Q _{1 to} Q ₄ . Then, the DC-DC converter converts the DC input voltage to a required level or controls it to a constant voltage to control the terminal P.
Output to N. _CDC is a capacitor. In the transistor Q ₁ to Q _4, the bridge inverter circuit (hereinafter, referred to as an inverter circuit) is a DC-AC converter constituting. Diode D ₁ to D ₄ provided in antiparallel to each transistor Q ₁ to Q ₄ are those provided for regeneration of the reactive power of the AC output side of the inverter circuit. L _AC and C _AC are a reactor and a capacitor forming an AC filter,
PWM (Pulse Width Modula) generated in the inverter circuit
tion pulse width modulation) A harmonic component is attenuated from the voltage V _PWM and a sine wave AC voltage V _OUT is output. L is an AC load. PT is a transformer for sensing the output AC voltage V _OUT . CONT is a transistor Q _{1 to} Q
It is a control device that generates a drive signal for controlling ON / OFF of ₄ . In addition, in FIG. 6A, the input is explained as a direct current, but the case where alternating current power is input is also generally used. This is shown in FIG. An AC-DC converter (commonly called a rectifier) controls the power of the AC power supply E _{AC to} a constant voltage and outputs a DC voltage to PN. Figure 6 after PN
The configuration is the same as that of (a).

FIG. 7 shows a circuit configuration (a) of the control unit CONT.
And the operation waveform (b) are shown. 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 taken out via the sensing transformer PT, this signal ES is input to one side of the error amplifier 6, and the other side is supplied with a sine wave voltage signal E _{R serving} as a reference. At the output of the error amplifier 6, E _OUT in which a signal obtained by amplifying the difference between the two inputs is superimposed on the reference sine wave voltage signal E _R is obtained. E _OUT = E _R + (E _R −E _S ) × R ₂ / R _{1 When} the output voltage of the inverter device fluctuates, the waveform of this superposed signal E _OUT changes so as to correct it. The triangular wave generator generates a high frequency triangular wave b. The frequency for switching the transistors Q _{1 to} Q ₄ of the inverter circuit is
It depends on 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 when the signal level is higher than the signal b and which is at a zero level during the other period. The PWM signal c is input to the distributor, the drive signal d is amplified and amplified if necessary, and the N 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 , respectively. Each transistor Q ₁ ~Q ₄ is the drive signal that has been given high
It is turned on during the period when it is at the level, turned off during the period when it is at 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 the sine wave voltage V _OUT corresponding to the reference sine wave signal a is output. Transistors Q ₁ to Q of the inverter circuit in this conventional apparatus
The configuration of the control device CONT for controlling the ₄ is complicated, resulting in lower reliability and higher cost. In addition, 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 is also used. This method is effective when the PWM voltage is directly fed to the motor. However, in the inverter that shapes the PWM voltage generated like the present invention into a sine wave voltage through the LC filter and then feeds the load, Natural vibration of LC filter (1
Since the free vibration occurring at the frequency corresponding to / √LC is superimposed on the sine wave voltage), the same method cannot be used in practice.

[0004]

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

[0005]

To achieve the above object, the present invention provides a DC-AC converter and an AC filter for converting the DC power into an AC voltage of a desired frequency. AC converter to P
In a control device for generating a drive signal for WM switching control, a semiconductor memory having a PWM pattern stored therein and a distribution circuit for converting a signal read out in time series from the memory into a drive signal are characterized. The inverter device is defined as the gist of the invention.
Furthermore, the present invention is a device for converting a DC voltage into an AC voltage of a desired frequency by a DC-AC converter and an AC filter, which is a device for obtaining the DC voltage, receives AC power, and outputs the DC voltage of a desired level. An AC-DC converter for converting to DC or a DC-DC converter for receiving DC power and converting it to a DC voltage of a desired level, and generating a drive signal for PWM switching control of the DC-AC converter. In a control device, a semiconductor memory storing a PWM pattern and a distribution circuit for converting a signal obtained by reading the memory in time series into a drive signal are provided. Is.

[0006]

The present invention provides a DC-AC converter in which the PW
By configuring a control device that generates a drive signal for M switching control by a memory that stores a PWM pattern and a distribution circuit that converts a signal read out from this memory in time series into a drive signal, The inverter controller is greatly simplified and downsized, and the cost can be reduced.

[0007]

EXAMPLES Next, examples of the present invention will be described. Figure 1
Is a first configuration example of the inverter device of the present invention. Figure 6
To the control device CONT, the output voltage V _OUT
Do not give 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 DC-DC converter on the input side controls the voltage of the output terminal PN to a constant voltage or controls the voltage level according to the output current. For example, by inserting a minute resistor R, a voltage drop that changes in proportion to the output current is sensed and controlled so as to increase the voltage in proportion to the current. Also, P
The current at the N terminal increases when the output of the inverter device increases. At this time, the voltage drops of the transistors Q _{1 to} Q ₄ and the reactor L _AC increase in proportion to the current. 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 has the desired level and quality as the input of the inverter, the DC power supply E
_{Power is} directly supplied to the terminal PN from _DC . An example is shown in which bipolar transistors are used as the switching elements Q _{1 to} Q ₄ of the inverter circuit, but this is an example, and another semiconductor switch such as a power MOS FET or IG is used.
You can also use BT (Insulated Gate Bipolar Transistor). Also, a full bridge inverter using four transistors is shown as the inverter circuit, but like the conventional inverter device, a half bridge inverter using two transistors and a three-phase bridge inverter using six transistors. Needless to say, it can also be used.

FIG. 2 shows a control unit CONT applied to the present invention.
An example of is shown. In the figure, 10 is a semiconductor memory, 1
Reference numeral 1 is a PWM signal converter, and 12 is 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 m-bit parallel data read from the memory M into m-bit serial data. Here, m PWM pattern arrays can be selected from the m-bit data, and as shown in FIG. 3, the half cycle of the output voltage of the inverter device is divided into 1 to n, and the output voltage is sine every time division. The pulse pattern arrays of 1 to m are distributed so that the wave half cycle is obtained. That is, in correspondence with the pattern C in FIG. 7, 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 thus obtained is converted into the signal C in FIG. 4 (the signal C in FIG. 7).
Correspond to). That is, 1 out of m patterns
Take one. The array of the selected patterns becomes the PWM signal C. The PWM signal C is applied to a distributor to drive signals d and e
To make. As is generally used, in the distributor, a photo coupler is used to insulate the input and output from each other as necessary, and the signal is amplified to amplify 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 PWM signals C, and each set is processed into a drive signal by a distributor for use.

A microcomputer circuit can be applied to the PWM signal converter, as is commonly used. FIG. 5A shows an example using a one-chip microcomputer circuit. The ROM of the microcomputer circuit corresponds to the memory M of FIG. In this ROM, PWM for one cycle of program and inverter output waveform
The 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 in time series, it is ANDed with the signal created by the external interrupt process, that is,
Only during the period when the interrupt signal of FIG. 5B is input, the pulses are deleted from the pulses Q _{1 to} Q ₄ read from the memory as shown by the broken line, and the signals C _{1 to} C ₄ are output from the output port of the microcomputer. Is output as. Signal C ₁ -C ₄ amplifies via respective distributor or insulated from the drive signal of the transistor Q ₁ to Q _4. Note that the required number of bits is not limited to this when a logic circuit is assembled externally to generate a signal corresponding to each transistor as shown in FIG. For example, in the case of a single-phase inverter, it may be 1 bit.

As for the short-circuit prevention of the DC power supply, which will be described below, data corresponding to each transistor can be provided to keep it off for a minimum unit time. In the inverter circuit of FIG. 1, transistors such as Q ₁ and Q ₂
If both are turned on at the same time, the direct current power supply (DC-DC converter) is short-circuited, and an overcurrent flows through the direct current power supply and the transistor, damaging it. On the other hand, in the transistor, there is a delay between the applied drive signal and the switching operation caused thereby. Therefore,
In order to prevent the transistor from being damaged by overcurrent, a method is provided in which a time difference is provided from when an OFF signal is applied to one of the transistors connected in series to when the ON signal is applied to the other transistor. In FIG. 2, the distributor has this pulse shaping function. FIG. 4 shows the operation of pulse shaping. NOT the signal C that is the inverted phase of the PWM signal C
Make with a circuit. On the other hand, a signal C _D delayed from the PWM signal C
Is made with an integrating circuit of a resistor and a capacitor and an amplifier. A signal C _D obtained by inverting the phase of the signal C _D made with the NOT circuit.
The signals C and C _D are given to the AND circuit 1, and its output signal is d
And Also, the signals C and C _D are given to the AND circuit 2 to generate 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 corresponding to the delay time due to the integrating circuit between the signals d and e. Even if there is a switching delay in the transistor, if the gap time is set longer than this delay time, the 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 applied to the D circuits 1 and 2 as the 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 V _OUT becomes overvoltage due to abnormal operation of the inverter circuit (separate sensor Change the level of this third input from H to zero level. That is, interrupt processing is performed. As a result, the output signals d and e of the AND circuits 1 and 2
There both zero-level, forcibly shut off the transistors Q ₁ to Q ₄ of the inverter circuit. By forcibly shutting off the transistor, the inverter device is protected from a short circuit accident of the load L, and the load L is protected 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 the cost. Since the control device requires a certain scale regardless of the power capacity converted by the inverter device, even a small-capacity inverter device requires the same control device as the large-capacity device. Therefore, the smaller the power capacity of the inverter device, the higher the ratio of the control device to the reliability and the cost. This indicates that the effect of the present invention is greater as the inverter device has a smaller power capacity. Further, in an inverter device having a small power capacity, the ratio of the physical size occupied by the control device also becomes large, so the present invention is also effective in downsizing the inverter device. Further, even if the voltage control device lacks the output voltage control function, it is possible to protect the inverter device itself from a short circuit of the load and to protect the load from the accident of the inverter device.

[Brief description of drawings]

FIG. 1 shows a configuration of an inverter device that is 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 signals.

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

FIG. 6 shows a configuration of a conventional inverter device, (a) shows one embodiment, and (b) shows another embodiment.

FIG. 7 shows a control device for controlling a conventional inverter device, in which (a) is a configuration diagram and (b) is a time chart of each signal.

[Explanation 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 Distributor 10 Memory 11 PWM signal converter 12 Distributor

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tadahisa Nakajima 1-15-1 Kitaotsuka, Toshima-ku, Tokyo Sanyo Electric Co., Ltd. (72) Inventor Yoshiaki Kobayashi 1-1-15 Kitaotsuka, Toshima-ku, Tokyo No. 1 Sanyo Denki Co., Ltd. (72) Inventor Seiichi Muroyama 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Within Nippon Telegraph and Telephone Corporation (72) Inventor Suzuki ▲ Noboru 1-chome, Uchisaiwaicho, Chiyoda-ku, Tokyo No. 6 Nihon Telegraph and Telephone Corporation (72) Inventor Masayuki Aoki 1-23-11 Sengoku, Bunkyo-ku, Tokyo Shinano Denki Co., Ltd.

Claims (5)

[Claims] 1. A device for receiving DC power and converting the DC power into an AC voltage of a desired frequency by a DC-AC converter and an AC filter, the control for generating a drive signal for PWM switching control of the DC-AC converter. In the device, PWM
An inverter device comprising a semiconductor memory in which a pattern is stored and a distribution circuit for converting a signal read out from the memory in time series into a drive signal. 2. A direct current voltage DC-AC converter and A
A device for converting an AC voltage of a desired frequency by a C filter, which is a device for obtaining the DC voltage, receives AC power and converts the AC power into a DC voltage of a desired level, or receives DC power. And a DC-DC converter that converts the DC-AC converter into a DC voltage of a desired level, and that generates a drive signal for PWM switching control of the DC-AC converter.
An inverter device comprising a semiconductor memory that stores a WM pattern and a distribution circuit that converts a signal read out in time series from this memory into a drive signal. 3. A PWM pattern for creating a PWM pattern for feeding back an AC voltage of an output, comparing the AC voltage with a reference sine wave voltage signal, and storing the corrected signal in a memory. Inverter device. 4. The inverter device according to claim 1, 2 or 3, wherein the distribution circuit has an interrupt function of stopping the output of the drive signal in response to a signal from the outside. 5. The interrupt processing function of a micro computer and the software are provided with an interrupt function of receiving an external signal and stopping the output of a drive signal. The inverter device according to 3.