JPS59202706A - Method and device for converting direct current to optional voltage waveform - Google Patents

Abstract

PURPOSE:To convert comparatively easily a DC to an optional voltage waveform by forming a control pulse train which has distributed a unit square wave and/or a collected wave of the unit square wave so that an integral waveform being nearly equal to an integral waveform of a specified voltage waveform can be obtained, and intermitting the DC. CONSTITUTION:A control pulse train 8 functions in order to obtain a specified voltage waveform 7, and consists of pulses P1-P13. The pulses P1, P2 and P6-P13 are a unit square wave of a height (h) and a width (w), but the pulse P3 and P7 are a collection of two unit square waves, and have a width 2w. In the same way, the pulse P4 and P6 have a width 3w, and the pulse P5 has a width 10w. A mutual interval of a rise time point of each pulse is set to an integer multiple of a unit interval of the rise time point. The control pulse train 8 set in this way becomes a control signal of a switching element for intermitting a DC, and when the switching element is turned on and off in response to the control pulse train 8, its output voltage waveform also becomes that which corresponds to the control pulse train, and by making it pass through a smoothing circuit, a waveform being approximate to a specified voltage waveform 7 can be obtained.

Description

TECHNICAL FIELD The present invention relates to a method and apparatus for converting direct current into an arbitrary voltage waveform, and more particularly to a method and apparatus suitable for direct-current to alternating-current conversion.

Prior art fl (X), f, (X) is a function of variable X, a is a constant, fIfX) = a f2(X) - ・ ・ ・ ・
・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・
・ ・ ・ ・ ・ ・ ・ ・ ・ ・ (1) If 0, then X when formula (1) holds true. Equation (2) holds regardless of the value of . Furthermore, when equation (2) holds true regardless of the value of Xo, equation (1) holds true. This is the theory of mathematics: /)c0f2(x)d x is f+ fXl and r2fx+ 0 to X, respectively. This is the area up to. Therefore,
Regardless of the value of xa, if the area from O to It is also a coefficient that represents the magnification of the area.

Based on the above idea, when obtaining the specific voltage waveform (1) shown in FIG. 1 using the conventional method, a rectangular wave control pulse train shown in (2) was formed. That is, any function af2. (Nono waveform (
1), a function f+ (
The rectangular wave control pulse train (2) was determined so as to obtain x).

By the way, in the conventional method, the rectangular wave control pulse train (
2), the integral waveform (31 (4
) (51 (61) had to be prepared. Waveform (3) in Fig. 2 is the integral value of waveform (1) in Fig. 1, that is, faf, (θ)・dθ, and the waveform ( 4) is the integral value of the rectangular wave control pulse train (2) in Fig. 1, that is, ff2(θ)
・dθ, and the waveform +51 is the value obtained by shifting the waveform (3) by a constant value α in the positive direction, that is, faf, (of・dθ + α), and the waveform (6) is the waveform (3) shifted by a constant value α. This is the value shifted in the negative direction, that is, faf+(θ)・dθ−α.Second
When forming the control pulse train (2) in FIG. 1 based on the four waveforms (31(41(51(61)) shown in the figure, the waveform (
4) becomes equal to waveforms (5) and (6), the direct current is interrupted in synchronization with the time point.

As is clear from the above (in the conventional method, many integral waveforms are required, making the conversion complicated. Also, in order to continuously change the output voltage, it is necessary to continuously change the value of the coefficient a). However, regardless of whether analog technology or digital technology is used to implement such control, the control device is relatively complex and expensive.

OBJECT OF THE INVENTION Therefore, an object of the present invention is to provide a method and apparatus that can relatively easily convert direct current into an arbitrary voltage waveform.

Structure of the Invention The first invention of the present application to achieve the above object is to convert a DC voltage into a specific voltage waveform by converting a unit rectangle so that an integral waveform approximately equal to the integral waveform of the specific voltage waveform is obtained. A method for converting direct current into an arbitrary voltage waveform, the method comprising forming a control pulse train in which a wave and/or a collective wave of the unit rectangular waves are distributed, and intermittent direct current in a manner corresponding to the control pulse train by a switching circuit. This is related to.

The second invention of the present application is a device for use in the above method, and is a device for converting a DC voltage into a specific voltage waveform, the device being a unit rectangular wave that sequentially sends out unit rectangular waves at a constant cycle. a generating circuit, a memory that stores in advance a digital signal for obtaining a control pulse train in which the unit rectangular waves are distributed so as to obtain an integral waveform substantially equal to the integral waveform of the specific voltage waveform, and the unit rectangular waves. A device for converting direct current into an arbitrary voltage waveform, comprising a logic circuit that sends out the control pulse train based on the output of the generator circuit and a digital signal obtained from the memory, and a switching circuit that intermittents the direct current voltage in response. This is related to.

Effects of the Invention According to the invention of the method and apparatus described above, a control pulse train is formed by an array of unit rectangular waves, and thereby direct current is interrupted, so that it becomes possible to easily form a specific voltage waveform. Further, according to the invention of the above-mentioned device, since the control pulse train is formed by the logic of the unit rectangular wave sent out at a constant cycle from the unit rectangular wave generation circuit and the digital signal sent out from the memory, a specific voltage waveform can be generated. It can be obtained with a simple device.

Embodiment FIGS. 3 and 4 show a method of converting direct current into an arbitrary voltage waveform according to an embodiment of the present invention. The specific voltage waveform (7) in FIG. 3 is the same as the waveform (1) in FIG.
This shows the 0 degree section. The control pulse train (8) is
This is to obtain a specific voltage waveform (7), and is
Consists of PI to P13. Pal, XPl, p2.
p8 to P13 are unit rectangular waves with a height of 1 width W,
The pulses P3 and Pl are collective waves of two unit rectangular waves and have a width of 2W, as is clear from the division by dotted lines. Further, the pulses P4 and P6 are set within three unit rectangles, and the interval between the rising points of each pulse is also set to an integral multiple of the unit interval at the rising point, and in this embodiment, from 0 degrees to the first pulse P1
The time to the rise of is 6 degrees, the interval between the rises of Pl and P2 is 6 degrees,
The rising interval between P2 and P3 is set to 4 degrees, and the rising interval between P3 and P4 is set to 6 degrees, which is an integral multiple of the minimum unit interval of 2 degrees. Note that the minimum rising unit interval corresponds to the case of a collective wave, and matches the pulse width W. The control pulse train (8) set in this way becomes a control signal for the switching element for intermittent direct current, and when the switching element turns on and off in response to the control pulse train (8) in Fig. 3, its output voltage changes. The waveform also corresponds to the control pulse train,
By passing it through a smoothing circuit, the specific voltage waveform (7
) can be obtained.

The control pulse train (8) in FIG. 3 is formed by the method shown in FIG. 4. In Figure 4, the waveform (9) is the integral value of the specific voltage waveform (7) in Figure 3, and the waveform aO)
is the integral value of the control pulse train (8) in FIG.

In short, the integral waveform CLOI of the control pulse train (8) is determined to approximate the integral waveform (9) of the specific voltage waveform (7), and the control pulse train (8) is made into a unit rectangular wave and/or a collective wave thereof. The width and distribution of each pulse P1 to P13 are determined as follows.

Next, how closely does a waveform consisting of an array of unit rectangular waves approximate the waveform of a given arbitrary function? Also, if the width of the unit rectangular wave is changed, only the amplitude changes and the waveform hardly changes. I will explain about it.

The functions of waveform (1) in FIG. 1 and waveform (7) in FIG. 3 are both 81rIθ+o and 5stn3θ. The rectangular wave control pulse trains that approximate this are (2) in Figure 1 and (8) in Figure 3, and each harmonic when the waveforms of pulse trains (2) and (8) are expanded into a Foury series. The amplitudes of the waves are shown in tables (a+ and tb+). Furthermore, the values obtained by expanding the waveform into a Foury series when the width of each unit rectangular wave of the control pulse train (8) in FIG. 3 is halved are shown in table tc+. Similarly. Table f shows the values when the width of the rectangular wave is reduced to 1/10.
Shown in d). Furthermore, if the width of the unit rectangular wave is halved or 1/10, the aggregate wave is completely divided into unit rectangular waves such that the point source portion of the aggregate wave pulses P3 to P7 becomes the rising edge of the unit rectangular wave. . The values shown in table fb) are the width of the unit square wave, that is, W
This is the value when the phase is set to 2°.If this width is set to a smaller value and the array of unit rectangular waves is subdivided, the approximation becomes even better.

Note that the amplitude of the harmonics in this table is calculated by subtracting the amplitude of the first harmonic by 10
0, and the remaining 3rd to 27th harmonics are shown in proportion to 100. Therefore, the table fal (bl (cl
The amplitudes of the first harmonics of fdl are not necessarily equal and are shown in Table (
If the amplitude of the first harmonic of alfbl is 100, the amplitude of the first harmonic of table FC+ is 49.9, and the amplitude of the first harmonic of table (di
The amplitude of the first harmonic is 10.

Each harmonic component of the conventional control pulse train (2) shown in Table (a) and the control pulse train (8) according to the present invention shown in Table (bl)
), the two are extremely similar. That is, by the method of the present invention, it is possible to obtain a specific voltage waveform with almost the same accuracy as the conventional method.

In addition, a table (bl
As is clear from the comparison between the table (C1) showing the case where the width is 50% and the table (di) showing the case where the width is 10%, even if the width of the unit rectangular wave is changed, the harmonic components are The ratio does not change. Therefore, it is possible to keep the waveform approximate and change only the amplitude, that is, the output voltage. This effect occurs because the unit rectangular waves are arranged and their rising phases are fixed.

The control pulse train (2) in FIG. 1 and the control pulse train (8) in FIG. 3 are shown up to 90 degrees, but from 90 degrees to 18
If the waveform between 0 degrees is made symmetrical about 90 degrees, even harmonics will not be generated.

FIG. 5 shows a conversion circuit according to an embodiment in which the control pulse train is simplified to simplify the explanation.
FIG. 6 is a diagram showing the state of each part in FIG. 5.

In FIG. 5, (11) is an integral voltage input terminal,
This is a terminal that supplies DC voltage. This human power terminal (11)
The voltage supplied from
1 and is integrated here. Since the discharge transistor α1 is connected in parallel to the capacitor a,
The sawtooth wave V in Fig. 6 is generated in synchronization with the on/off period of one transistor. (I6) is the output frequency indication voltage input terminal, and the indication voltage supplied from here is V-F. The converter (171 converts it into a frequency signal and generates a pulse at a period corresponding to the specified frequency.V-F
The output pulse of the converter (17+) is input as a clock pulse to the counter (18) and is also input to the transistor Q51.
input to the base of In the example of Fig. 6, 18 pulses are generated at a period of θ5 = 20' during the period θ° ~ 3600,
18 sawtooth waves are generated. A9 is a voltage comparator which generates a comparison output between the control voltage (2) applied from the control voltage input terminal (20) and the sawtooth wave (2). As is clear from ■P in FIG. 6, in this embodiment, the sawtooth waveform generates the comparison output VP which is at a high level during a period lower than the control voltage ■. That is, 18 unit rectangular wave pulse outputs 2 are generated at a period θS from θ° to 360° in FIG. Therefore, in the embodiment shown in FIG. 5, a unit rectangular wave generating circuit (2υ) is constituted by the integrating circuit 02 and the comparator (19).

(Two are memories, which store digital signals for forming control pulse trains (1) and (2) in Fig. 6 based on the unit rectangular wave output VP in Fig. 6. As is clear from the address column in Figure 6, there are a total of 19 addresses from address O to 18, and address 18
A reset signal is stored in , and at the moment of switching to address 18, a reset signal for the counter (181) is generated from line M4, and the address is switched to zero. Note that each address 0 to 18 corresponds to M- in FIG. As shown in M4, 4-bit data is stored, and this data is read out by four output lines M1 to M4 corresponding to the 4 bits.Memory α
Data reading from 9 is performed using the same clock as the period θS of the sawtooth waveform. That is, the addresses are sequentially designated by the counter 08).

(c) and (241 are first and second AND circuits for obtaining a control pulse train, one input terminal of the first AND circuit is connected to the comparator (19), and the other input terminal is connected to the memory (221 One input terminal of the second AND circuit (221) is connected to the first output line M1 of the memory (221
is connected to the second output line M2 of.

The outputs of M1 to M4 in FIG. 6 send out low level (L) or high level sunrise in each segment period of θs = 20 degrees. Therefore, the AND circuit (to) of the output of the comparator in FIG.
When found in (2), the first and second control pulse trains v1 and 2 of FIG. 6 are obtained. Since the first and second control pulse trains (1) and (2) are obtained based on the unit rectangular wave indicated by Vp, they are pulse trains in which unit rectangular waves are arranged.

Transistors Ql, Q2 . Q3 and Q4 constitute a bridge inverter, and intermittent the voltage of the DC power supply E. The output of the first AND circuit (c) is coupled to the bases of transistors Ql and Q4, and the output of the second AND gate I24
) is coupled to the bases of transistors Q2 and Q3, so in response to the control pulse trains ■1 and ■2 of FIG. The output voltage VO can be made into a waveform approximating a sine wave by the smoothing effect of the smoothing circuit or the load itself.

The output line M3 of the memory (2) is connected to the control voltage terminal (
A) is coupled to the base of the transistor connected in parallel to the resistor (2) of the line. Therefore, when outputs as shown in FIG. 6 occur sequentially from the memory output line M3, the transistor (C) turns on and off in response to this.
The value of control voltage ■ changes. Therefore, it becomes possible to change the width of the output pulse at a specific position. Note that when there is no need to change the control voltage blindness, the value of the memory output line M3 is always kept constant.

Since the circuit of FIG. 5 has a comparator a9,
By changing the control voltage ■, the magnitude of the output voltage VO can be adjusted. FIG. 7 shows this voltage adjustment. When the control voltage Vm moves to the top of the sawtooth wave vA in FIG. 7(4), the output voltage VO in FIG. 7(B) is obtained, and Vl increases. If the output voltage is located in the middle of Vm, an output voltage of 0 as shown in FIG. 7(C) can be obtained.

As is clear from the comparison between Figure 7 (B) and (C), in the case of the maximum output voltage, a collective wave of two unit rectangular waves is included, and when the output voltage is lowered below this, the collective wave The wave is divided into two unit square waves. Figure 7 (C) shows the output when the rising phase of each unit rectangular wave is fixed and the falling phase is controlled, and Figure 7 (■) shows the output when the rising phase of each unit rectangular wave is fixed and the rising phase is controlled. The output is shown below. 7th
The method of fixing the falling phase in FIG. υ can also provide the same effect as the method of fixing the rising phase.

As is clear from the above, this embodiment has the following advantages.

fal As shown in FIG. 6, Vl and V2, the control pulse train is formed by arranging unit rectangular waves, so the control pulse train can be easily obtained.

fb) Since the mutual interval between the rising points of the unit rectangular waves is set to an integral multiple of the unit interval θS, the formation of the control pulse train and the switching control of the inverter are facilitated.

(C1 The rising phase of each unit rectangular wave is always constant regardless of the output voltage and output frequency, and the mutual interval at the rising point is an integral multiple of θS, so the rising edge phase can be calculated using extremely universal digital technology. , or can be set very easily using analog technology. Furthermore, the control of the pulse width after the rise is also easy, and the output voltage 0 can be adjusted without changing the waveform.

tdi In this embodiment, since the input terminal u9 is configured to supply the DC voltage of the input/output power supply E, it is possible to limit the fluctuation of the output voltage due to the fluctuation of the impark input voltage. I can do it. That is, when the input voltage decreases, for example, the input voltage of the integrating capacitor (1410) also decreases, and the slope of the sawtooth waveform shown in FIG. 6 becomes gentler.

As a result, the pulse width of the output voltage becomes wider. However, since the input voltage has decreased and the amplitude of the output pulse has become smaller, the area of the output pulse remains almost constant, and the output voltage fluctuations and Substantially no fluctuations in harmonic components occur.

Such an operation also occurs when the inverter power supply E supplies a pulsating voltage. Therefore, there is a great advantage that voltage fluctuations including input voltage pulsations do not appear on the output side.

(e) Since the width of a specific pulse can be controlled by switching the level of the control voltage (2) using the memory output line M3, control that improves the approximation to a sine wave can be easily achieved.

Modifications Although the embodiments of the present invention have been described above, the present invention is not limited thereto, and for example, the following modifications are possible.

In Figure 5, the voltage ■ supplied from the control voltage input terminal to the comparator θ9! may be set as a constant reference voltage, and the voltage supplied from the input terminal 1) may be set as the output voltage command voltage. That is, the slope of the sawtooth waveform shown in FIG. 6 may be changed in accordance with the output voltage, and the width of the sawtooth output pulse may be changed.

CB) Input the voltage of terminal (1]) or (201), <
- The output voltage may be supplied based on the detection of the evening output voltage, and closed-loop control may be used.

The waveform approximation may be improved by changing the pulse width of only the unit rectangular wave selected from the pulse train force (of the output VP of the zero comparator 091).

[Brief explanation of the drawing]

Figure 1 is a waveform diagram showing the specific voltage waveform in the conventional conversion method and the control/curse train to obtain it.
FIG. 3 is a waveform diagram showing a method for forming a control pulse train according to the embodiment of the present invention; FIG. 4 is a waveform diagram showing the principle for obtaining the control pulse train shown in FIG. 3, FIG. 5 is a circuit diagram showing a conversion device according to an embodiment of the present invention, and FIG. Waveform diagram showing the state of
Figure ('!. It is a waveform diagram showing the adjustment of the output voltage. (7)... Specific voltage waveform, (8)... Control pulse train, (2υ... Unit rectangular wave generation circuit, ( 2z...Memory, (231(2(a)...AND circuit, E...
DC power supply, Q1-Q4) transistor. Agent Noriji Takano

Claims (1)

[Claims] When converting il+ DC voltage into a specific voltage waveform, a unit rectangular wave and/or a collective wave of the unit rectangular waves is converted so that an integral waveform approximately equal to the integral waveform of the specific voltage waveform is obtained. A method for converting direct current into an arbitrary voltage waveform, the method comprising: forming a distributed control pulse train; and intermittent direct current in a manner corresponding to the control pulse train by a switching circuit. (2) The method for converting direct current into an arbitrary voltage waveform according to claim 1, wherein the unit rectangular wave has a pulse width adjusted to correspond to an amplitude change of the specific voltage waveform. (3) A device for converting a DC voltage into a specific voltage waveform, which includes a unit rectangular wave generation circuit that sequentially sends out unit rectangular waves at a constant cycle, and an integral waveform that is approximately equal to the integral waveform of the specific voltage waveform. a memory that stores in advance a digital signal for obtaining a control pulse train in which the unit rectangular waves are distributed such that the unit rectangular wave is distributed; A device for converting direct current into an arbitrary voltage waveform, comprising: a logic circuit that sends out a control pulse train; and a switching circuit that cuts on and off the DC voltage in response to the control pulse train sent from the logic circuit. (4) The unit rectangular wave generation circuit is a circuit that sequentially transmits unit rectangular waves whose pulse widths are adjusted to correspond to changes in the amplitude of the specific voltage waveform at a constant cycle. A device for converting direct current into an arbitrary voltage waveform according to item 3.