JPH08168255A - Controller for digital active filter - Google Patents

Abstract

PURPOSE: To provide a highly reliable controller for a digital active filter which can prevent a rush current or abrupt voltage boosting at the time of starting the filter by softly starting the filter. CONSTITUTION: A multiplier 28 calculates the drive pattern of PWM signals from the side wave pattern stored in a ROM 32 based on the outputs of a current detecting circuit 22 which detects the current waveform of an AC power supply and an output voltage detecting circuit 25 which detects the output voltage of the AC power supply and a switching element is driven by using the PWM signals of the calculated drive pattern. In addition, the duty ratio of the PWM signals which drive the switching element is reduced at the time of starting an active filter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a digital active filter which is used for reducing a harmonic current of a power supply circuit and which is particularly configured to be soft-started during driving.

[0002]

2. Description of the Related Art As a method of reducing a harmonic current of a power supply circuit, there are a method of inserting a passive filter composed of a reactor coil and a capacitor and a method of inserting an active filter composed of a semiconductor.

The method using a passive filter has a small number of parts and can be easily realized, but the harmonic reduction characteristic is not good. In addition, the passive filter becomes large and heavy in the passive component when the power to be handled becomes large, which makes it impractical.

On the other hand, the method using the active filter generally has a large number of parts and has a complicated circuit configuration. However, a control device of an active filter generally has a control circuit configured by an analog IC in order to reduce the number of parts, and has already been commercialized by several companies. Further, the active filter has a feature that the harmonic current reduction characteristic is very excellent.

By the way, in recent years, the performance of digital ICs has improved, the speed of clocks has increased, the accuracy and resolution have improved,
The cost has been reduced, and various functions that were conventionally configured by analog circuits have been replaced by digital circuits. The digital circuit has an advantage that the operation is highly reproducible, the function can be easily changed by installing a register inside, and complicated control can be easily performed. The control device of the active filter is no exception, and a system in which a part or the whole of the control circuit is digitized has been reported in literatures such as academic societies and patents.

[0006]

As described above, a digital system for an active filter control device is very promising and is being developed. However, it is not a digital system for an active filter control device. For example, there is a problem that an inrush current is generated at the time of start-up or a sudden voltage rise occurs, and in some cases, circuit components are destroyed.

The present invention has been made in view of the above,
It is an object of the present invention to provide a control device for a digital active filter, in which inrush current and abrupt voltage rise are prevented by enabling soft start at startup, and reliability is improved.

[0008]

In order to achieve the above object, a control device for a digital active filter according to the present invention comprises a current detecting means for detecting a current waveform of an AC power supply, an output voltage detecting means for detecting an output voltage, Calculation means for calculating the drive pattern of the PWM signal from the sine wave pattern based on the outputs of the current detection means and the output voltage detection means, and the PW of the drive pattern calculated by the calculation means.
A digital active filter control device having a drive circuit for driving a switching element with an M signal, comprising:
It is a gist to have a duty ratio reducing means for reducing the duty ratio of the PWM signal that drives the switching element when the active filter is activated.

The control device for a digital active filter according to the present invention comprises a current detecting means for detecting a current waveform of an AC power supply, an output voltage detecting means for detecting an output voltage, the current detecting means and the output voltage detecting means. A controller for a digital active filter having an arithmetic means for arithmetically operating a drive pattern of a PWM signal from a sine wave pattern based on an output, and a drive circuit for driving a switching element with the PWM signal of the drive pattern arithmetically operated by the arithmetic means. Therefore, the gist of the present invention is to have carrier frequency reducing means for reducing the carrier frequency of the PWM signal that drives the switching element when the active filter is activated.

Further, the control device for a digital active filter according to the present invention comprises a current detecting means for detecting a current waveform of an AC power supply, an output voltage detecting means for detecting an output voltage, the current detecting means and the output voltage detecting means. A controller for a digital active filter having an arithmetic means for arithmetically operating a drive pattern of a PWM signal from a sine wave pattern based on an output, and a drive circuit for driving a switching element with the PWM signal of the drive pattern arithmetically operated by the arithmetic means. Therefore, the gist is to have a zero-cross synchronizing means for starting the active filter in synchronization with the zero-cross point of the AC power supply.

The microcomputer unit of the present invention comprises a current detecting means for detecting the current waveform of the AC power supply, an output voltage detecting means for detecting the output voltage, a sine wave based on the outputs of the current detecting means and the output voltage detecting means. A calculation unit that calculates a drive pattern of the PWM signal from the pattern, a drive circuit that drives the switching element by the PWM signal of the drive pattern calculated by the calculation unit, and a PWM signal that drives the switching element when the active filter is activated. A digital active filter controller having either one of a duty ratio reducing means for reducing a duty ratio and a carrier frequency reducing means for reducing a carrier frequency of a PWM signal for driving the switching element at the time of starting the active filter. Is the gist .

Further, the air conditioner of the present invention is based on the outputs of the current detecting means for detecting the current waveform of the AC power source, the output voltage detecting means for detecting the output voltage, the current detecting means and the output voltage detecting means. PW from sine wave pattern
Calculation means for calculating the drive pattern of the M signal, drive circuit for driving the switching element by the PWM signal of the drive pattern calculated by the calculation means, and PWM for driving the switching element when the active filter is activated
A control device for a digital active filter having one of a duty ratio reducing means for reducing a duty ratio of a signal and a carrier frequency reducing means for reducing a carrier frequency of a PWM signal for driving the switching element at the time of starting the active filter. The point is to have it in the power supply circuit.

[0013]

In the controller for the digital active filter of the present invention, the duty ratio of the PWM signal for driving the switching element is reduced when the active filter is activated.

In the digital active filter control device of the present invention, the carrier frequency of the PWM signal for driving the switching element is reduced when the active filter is activated.

Further, in the control device for the digital active filter of the present invention, the activation of the active filter is performed in synchronization with the zero cross point of the AC power supply.

In the microcomputer unit of the present invention, a control device for the digital active filter is provided to reduce the duty ratio of the PWM signal for driving the switching element when the active filter is activated, or when the active filter is activated. The carrier frequency of the PWM signal that drives the switching element is reduced.

Further, in the air conditioner of the present invention, the control device for the digital active filter is provided in the power supply circuit to reduce the duty ratio of the PWM signal for driving the switching element when the active filter is activated, or to activate the active filter. The carrier frequency of the PWM signal that drives the switching element is reduced when the filter is activated.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a digital active filter having a control device for a digital active filter according to an embodiment of the present invention. The active filter shown in FIG. 1 is a step-up chopper type active filter. Are configured. In the figure, 1
Is an AC power supply, 2 is a rectifying diode, 3 is a reactor coil, 4 is a switching element made of, for example, an IGBT or MOSFET, 5 is a diode, 6 is a smoothing capacitor,
Reference numeral 7 is, for example, a load of an inverter or a switching power supply, 8 is a microcomputer, 9 is an active filter control device, 10 is a voltage waveform detection circuit including a resistance and an isolation circuit, and 11 is a current detection element such as a current transformer or a current detection resistor. A current detection circuit including an isolation circuit, a switching element drive circuit 12 including an isolation circuit such as a photocoupler, and an output voltage detection circuit 13 including a voltage dividing resistor and an isolation circuit.

Next, the operation of the active filter shown in FIG. 1 will be described with reference to the waveform chart shown in FIG.

2 (a), 2 (b) and 2 (c) are diagrams showing operation waveforms at points indicated by A, B and C in FIG. 1, respectively. That is, FIG. 2A corresponds to A in FIG.
2 shows the voltage waveform of the output of the rectifying diode 2 shown in FIG.
2B shows the waveform of the PWM signal that is the drive voltage of the gate of the switching element 4 shown by B in FIG.
(C) shows the waveform of the current detected by the current detection circuit 11 shown by C in FIG.

In FIG. 1, the frequency of the AC power supply 1 is 50.
The AC voltage from the AC power supply 1 is rectified by the rectifying diode 2 to have a pulsating voltage waveform as shown in FIG. 2A. This pulsating voltage is applied to the reactor coil 3 while the switching element 4 is off.
The current flows through the diode 5, charges the smoothing capacitor 6, and is supplied to the load 7. At this time, the energy accumulated in the reactor coil 3 is discharged. Further, the pulsating voltage flows through the reactor coil 3 to the switching element 4 while the switching element 4 is on, and the AC power supply 1
At the same time, the voltage is supplied from the smoothing capacitor 6 to the load 7 at this time. At this time, energy is accumulated in the reactor coil 3.

The switching element 4 is driven by the PWM signal from the switching element drive circuit 12, and the PW
It is repeatedly turned on and off in the cycle of M signal. Figure 2
The voltage waveform shown in (b) is a PWM signal for driving the switching element 4, has a frequency of several tens KHz to several hundreds KHz, and is synthesized by the active filter control device 9.

The active filter control device 9 outputs the output voltage detection circuit based on a sine wave pattern stored in a built-in ROM as described later or based on the sine wave waveform of the power source input from the voltage waveform detection circuit 10. The calculation is performed by the signal of 13 and the signal of the current detection circuit 11, and the PWM signal output from the switching element drive circuit 12 is combined. As a result, the current of the AC power supply 1 can be the sine wave shown in FIG. Further, the microcomputer 8 controls the entire system including the active filter control device 9 and the load 7.

The active filter control device 9 is constructed as shown in FIG. In FIG. 3, reference numeral 21 is a voltage waveform detection circuit including an AD converter, and 22 is A.
A current detection circuit composed of a D converter or the like, 23 a protection circuit, 24 a drive circuit, 25 an output voltage detection circuit composed of a reference voltage circuit and an AD converter, 26 a phase detection circuit of a power supply, 27 a start-up circuit, 28 a A multiplier, 30 is an error detection circuit, 31 is a comparison circuit including a digital comparator, 32 is a ROM storing a sine wave pattern, 3
Reference numeral 3 is an oscillator circuit including a digital counter, 34 is a frequency control circuit, and 35 is an internal control circuit.

Next, referring to the waveform diagram shown in FIG. 4, FIG.
The operation of the active filter control device 9 will be described. In FIG. 3, the output voltage detection circuit 25 calculates and outputs the difference between the reference voltage and the voltage obtained by dividing the output voltage by a resistor, and supplies it to the protection circuit 23 and the multiplier 28. Output voltage detection circuit 2
The setting of the output voltage value of 5 can be determined by the voltage division ratio of the resistor. The multiplier 28 supplied with the output voltage multiplies the output voltage by the sine wave pattern stored in the voltage waveform detection circuit 21 or the ROM 32 to calculate and output the basic pattern of the PWM waveform.

The output of the multiplier 28 is a sine wave of the frequency of the AC power supply 1, and it corresponds to the output of the output voltage detection circuit 25 and is large when the output voltage is lower than the target value and high when the output voltage is high. Get smaller. The error detection circuit 30 compares the output of the multiplier 28 with the output of the current detection circuit 22,
The difference is supplied to the comparison circuit 31. The comparison circuit 31 determines the PW from the output of the error detection circuit 30 and the output of the oscillation circuit 33.
The duty ratio of the M pattern is determined and the drive circuit 24 is driven. The drive circuit 24 has sufficient capacity to drive the isolation circuit of the switching element drive circuit 12, and outputs the PWM pattern output from the comparison circuit 31. The above operation is performed in synchronization with the internal clock of the active filter control device 9.

Further, the protection circuit 23 is the output voltage detection circuit 2
When the output of 5 increases, or when the output of the current detection circuit 22 increases, the output of the drive circuit 24 is stopped.
The internal control circuit 35 is composed of a command register, a data register, a decoder circuit, etc., controls the overall operation of the active filter control device 9, and transfers data to and from the outside. Actually, the internal control circuit 35 turns on / off the active filter control device 9 and the oscillation circuit 33.
, The reference voltage of the output voltage detection circuit 25, the threshold value of the protection circuit 23, and the like.

Next, with reference to the waveform diagram shown in FIG. 4, the operation at the time of starting the active filter will be described.

When an activation signal is input to the active filter control device 9, the drive circuit 27 informs the comparison circuit 31 of the activation state, the carrier frequency remains fixed, and the calculated duty ratio is originally set. Regardless, Figure 4
As shown in (b), the on time of the switching element is shortened to prevent the output voltage from rapidly increasing. By setting the on-time and the duration of the activation state in the register of the internal control circuit 35, the on-time and the duration of the activation can be selected to arbitrary values.

As an operation at the time of starting the active filter, when a start signal is input to the active filter control device 9, the start circuit 27 informs the frequency control circuit 34 that the start state is in effect, and FIG. ),
The frequency control circuit 34 reduces the carrier frequency of the PWM signal to prevent the output voltage from rapidly increasing. By setting the carrier frequency and its duration in the register of the internal control circuit 35, it is possible to select the carrier frequency and its duration at startup to arbitrary values.

Further, as the operation at the time of starting the active filter, the phase detection circuit 26 detects the zero-cross point of the AC power supply 1 and the starting circuit 27 sets the start timing to the zero-cross point, so that the rush current at the time of starting is changed. This can be prevented and soft start of the active filter can be enabled.

FIG. 5 is a diagram showing the configuration of another embodiment of the present invention. In the embodiment shown in the figure, the active filter control device 9 shown in FIG. 3 described above is combined with a core of a microcomputer to form an MCU (microcomputer unit). In the figure, 9 is the active filter control device, 42 is a microcomputer core, 44 is other peripheral circuits, and 43 is a data bus and an address bus.

As shown in FIG. 5, by forming an MCU using the active filter control device 9 and further integrating this into one chip, cost reduction and noise resistance improvement can be achieved.

FIG. 6 is a diagram showing the configuration of another embodiment of the present invention. In the embodiment shown in the figure, the active filter shown in FIG. 1 is used in the power supply circuit of the air conditioner. In the figure, 51 is an AC power supply, 52 is a rectifying diode, 60 is an active filter having the active filter control device 9, 56 is an inverter,
Reference numeral 58 is a compressor motor, and 59 is a microcomputer that controls the overall operation of the air conditioner.

A conventional structure corresponding to the device shown in FIG. 6 is shown in FIG. 7, in which the same components are designated by the same reference numerals as in FIG. In FIG. 7, 53 is an electronic starter, 54 is a drive circuit for the electronic starter, and 55 is a smoothing circuit having a slight power factor improving function. The electronic starter 53 is provided to prevent the inrush current from flowing through the capacitor of the smoothing circuit 56, and the inrush current is limited by the resistance of the electronic starter at the time of startup.

As can be seen from the comparison of both figures, the active filter 60 shown in FIG. 6 replaces the electronic starter 53, its drive circuit 54, and the smoothing circuit 55 of FIG. 7, and thus the active filter 60 is used. As a result, the conventional electronic starter is not required, and the active filter 60 has the advantages that it can suppress the inrush current when the power is turned on as described above. Then, by eliminating the need for the electronic starter, it is possible to reduce the number of parts having contacts, improve reliability, and reduce costs. It goes without saying that the conventional power factor improving effect is excellent.

[0038]

As described above, according to the present invention,
When the active filter is started, the duty ratio or carrier frequency of the PWM signal that drives the switching element is reduced, or the active filter is started in synchronization with the zero-cross point of the AC power supply. It is possible to prevent an inrush current and a rapid voltage increase without providing a circuit. In addition, cost reduction and noise resistance can be improved by forming one chip.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an active filter having a control device for a digital active filter according to an embodiment of the present invention.

FIG. 2 is a waveform diagram showing the operation of the active filter shown in FIG.

FIG. 3 is a circuit diagram showing a configuration of an active filter control device used in the active filter shown in FIG.

FIG. 4 is a waveform diagram showing an operation at the time of starting the active filter shown in FIG.

5 is a diagram showing a configuration of another embodiment of the present invention, which is a diagram in which an active filter control device shown in FIG. 3 is combined with a core of a microcomputer to configure an MCU.

FIG. 6 is a diagram showing the configuration of another embodiment of the present invention, in which the active filter shown in FIG. 1 is used in a power supply circuit of an air conditioner.

7 is a diagram showing a configuration of a conventional device corresponding to the device of FIG.

[Explanation of symbols]

 1 AC power supply 3 Reactor coil 4 Switching element 7 Load 8 Microcomputer 9 Active filter control device 10 Voltage waveform detection circuit 11 Current detection circuit 12 Switching element drive circuit 13 Output voltage detection circuit 26 Phase detection circuit 27 Start circuit 28 Multiplier 30 Error detection Circuit 31 Comparison circuit 32 ROM 33 Oscillation circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaaki Ohno 3-3-9 Shimbashi, Minato-ku, Tokyo Toshiba Abu E. Co., Ltd.

Claims (5)

[Claims] 1. A PWM signal is driven from a sine wave pattern based on the outputs of a current detecting means for detecting a current waveform of an AC power supply, an output voltage detecting means for detecting an output voltage, the current detecting means and the output voltage detecting means. A control device for a digital active filter, comprising a calculation means for calculating a pattern, and a drive circuit for driving a switching element with a PWM signal of a drive pattern calculated by the calculation means, wherein the switching element is provided when the active filter is activated. A control device for a digital active filter, comprising a duty ratio reducing means for reducing a duty ratio of a PWM signal for driving the. 2. A PWM signal is driven from a sine wave pattern on the basis of the outputs of the current detection means for detecting the current waveform of the AC power supply, the output voltage detection means for detecting the output voltage, the current detection means and the output voltage detection means. A control device for a digital active filter, comprising a calculation means for calculating a pattern, and a drive circuit for driving a switching element with a PWM signal of a drive pattern calculated by the calculation means, wherein the switching element is provided when the active filter is activated. 1. A control device for a digital active filter, comprising a carrier frequency reducing means for reducing a carrier frequency of a PWM signal for driving the. 3. A PWM signal is driven from a sine wave pattern based on the outputs of the current detection means for detecting the current waveform of the AC power supply, the output voltage detection means for detecting the output voltage, the current detection means and the output voltage detection means. A control device for a digital active filter, comprising a calculation means for calculating a pattern and a drive circuit for driving a switching element with a PWM signal of a drive pattern calculated by the calculation means, wherein activation of the active filter is performed by the AC power supply. A digital active filter control circuit having a zero-cross synchronizing means for synchronizing with a zero-cross point. 4. A PWM signal is driven from a sine wave pattern based on the outputs of the current detection means for detecting the current waveform of the AC power supply, the output voltage detection means for detecting the output voltage, the current detection means and the output voltage detection means. Calculation means for calculating the pattern, P of the drive pattern calculated by the calculation means
A drive circuit for driving a switching element with a WM signal, and a duty ratio reducing means for reducing a duty ratio of a PWM signal for driving the switching element when the active filter is activated, or a PWM for driving the switching element when the active filter is activated. A microcomputer unit having a control device for a digital active filter having one of carrier frequency reducing means for reducing a carrier frequency of a signal. 5. A PWM signal is driven from a sine wave pattern based on the outputs of the current detecting means for detecting the current waveform of the AC power supply, the output voltage detecting means for detecting the output voltage, the current detecting means and the output voltage detecting means. Calculation means for calculating the pattern, P of the drive pattern calculated by the calculation means
A drive circuit for driving a switching element with a WM signal, and a duty ratio reducing means for reducing a duty ratio of a PWM signal for driving the switching element when the active filter is activated, or a PWM for driving the switching element when the active filter is activated. An air conditioner comprising a control device for a digital active filter having one of carrier frequency reduction means for reducing a carrier frequency of a signal in a power supply circuit.