JPH0345009A - Approximate sine wave PWM waveform output method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a method for outputting an approximate sine wave PIIM waveform used for inverter control, etc., and more specifically relates to an approximate sine wave PIIM waveform output method that can vary the frequency of a target sine wave. Wave PvM
This relates to a waveform output method.

[Conventional example] Conventionally, in calculating this type of approximate sine wave PVMfi type, a sine wave waveform and a fundamental wave (carrier wave) of a triangular wave are superimposed, and the calculation is performed based on the magnitude relationship between the sine wave waveform and the carrier wave. I am trying to obtain PIIM waveform data. To explain using FIG. 8 as an example, the PwH waveform data consists of data (switch data) in which the part where sine wave 1 is larger than carrier wave 2 is set to "171" and the part where it is smaller is set to "0"; is interval data (time data) from the point where the carrier wave 2 intersects with the carrier wave 2 to the next intersecting point, and these switch data 3a and time data 3b are stored in various memory 3 (Fig. 9) according to the frequency of the sine wave 1. ) to 1
It is stored as 18 waveform data.

Here, as shown in FIG. 9, when a target frequency command is issued, the control section (microcomputer) 4
The switch data 3a and time data 3b corresponding to the target frequency are sequentially read out from the memory 3, and a pulse train (PWN waveform) signal corresponding to these data is output to the I
Output from /O boat. That is, the pulse train signal is a PWM waveform of an approximate sine wave of the target frequency.

Therefore, switch data and time data are obtained in the same manner as described above using three-phase sine waves and carriers whose phases are shifted by, for example, 120 degrees.

Using these waveform data, for example, when a switching transistor that drives a compressor is turned ON or OFF, a current waveform that approximates the above sine wave flows through the compressor, so the operating frequency of the compressor is determined by the target waveform data. value.

[Problems to be Solved by the Invention] By the way, in calculating the above PVM waveform data, in order to obtain PVM waveform data (switch data 3a, time data 3b) for each frequency of the approximate sine wave, the memory 3 is It required a capacity to store PWM1M waveform data. Moreover, as the number of frequencies of the approximate sine wave increases, there is a problem that the capacity of the memory 3 must be increased.

This invention was made in view of the above problems, and its purpose is to provide an approximation that allows obtaining 1wM waveform data that requires less memory capacity when the number of target frequencies of PIIM waveform output is increased. Sine wave PWM
The object of the present invention is to provide a waveform output method.

[Means for Solving the Problem] In order to achieve the above object, the present invention divides a sine wave into equal parts, and stores the height value of the sine wave at the divided parts in a first memory as waveform data. At the same time, the interval from the peak or trough of the carrier wave superimposed on the sine wave to the predetermined position of the carrier wave corresponding to the height value is stored in a second memory as time data, and Storing step data in a third memory for reading out the waveform data of the first memory according to the frequency, reading out the waveform data based on the step data corresponding to the frequency of the target waveform, and corresponding to the waveform data. The gist is that time data is set in a real timer of a microcomputer in a cycle of half the cycle of the carrier wave, and the output of the real-time I/O port of the microcomputer is made into a P%IM waveform output of an approximate sine wave.

[Function] With the method described above, when outputting the PIIM waveform at the target frequency, the step data corresponding to the target frequency is read from the third memory, and the waveform data is read from the first memory based on the step data. Read out. Further, time data corresponding to the waveform data is read from the second memory, and the time data is set in the real timer of the microcomputer in the control section. Furthermore, since the step data is read out at the timing of a half cycle of the carrier wave, the time data based on the switch data is set in the real timer at the timing of a half cycle of the carrier wave. Then, the output of the real-time I/O port of the microcomputer is inverted after the time data set at the half-cycle timing has elapsed (if it is at the "Ill" level, it becomes the "Yes"level; if it is at the "Yes" level, it is turned into the "Yes" level). II
H11 level), and by its inversion control, a PIIM waveform of an approximate sine wave of the target frequency is obtained. Therefore, even if there is no approximate sine wave PVM waveform data corresponding to the target frequency, if step data corresponding to the target frequency is read from the third memory, the time data set in real time of the microcomputer can be changed. PVN waveform outputs of approximate sinusoids of various frequencies can be obtained.

[Example] Hereinafter, an example of the present invention will be described based on the drawings. Note that in FIGS. 1 to 3, the same or equivalent parts as in FIGS. 7 and 8 are designated by the same reference numerals, and redundant explanation will be omitted.

In FIGS. 1 to 3, the control circuit that outputs the approximate sine wave PwH waveform is a control unit (microcomputer) 5 equipped with a real-time I/O port.

A first memory 6 that divides the sine wave 1 into equal parts and stores the height value of the sine wave 1 at the divided points as sine wave data.
a, a second memory 6b that stores as time data the interval from the trough or peak point of the carrier wave 2 superimposed on the sine wave l to a predetermined position of the carrier wave 2 corresponding to the height value, and a target waveform; a third memory 6c that stores data on the number of steps for reading out the sine wave data in the first memory and the time data in the second memory according to the frequency of the third memory 6c;
ROM 6, which is a memory having the following functions. The above sine wave data is the height value at either end of the division when the sine wave 1 is equally divided, or the average height value at the division interval.

Next, referring to FIGS. 3 to 5, the first memory 6a
A method of calculating the sine wave data stored in the second memory 6b and the time data stored in the second memory 6b will be explained.

First, arbitrarily divide 180 degrees (π) of sine wave 1 into m equal parts,
Obtain the height value of the sine wave in this equal division, and
This height value is taken as sine wave data.

Then, the sine wave data is calculated by the formula Hsin (nπ/Maro), and as shown in Figure 3, when the peak value of the sine wave l is H, the height value of the sine wave data is A predetermined position 1a where the rising waveform of the carrier wave 2 intersects is determined, and the interval (time: t a ) from the trough of the carrier wave 2 to that position is obtained as time data. Although the positive side of the sine wave 1 has been described, in the case of the negative side, a predetermined position where the height value of the sine wave 1 and the falling waveform of the carrier wave l intersect in equal division is found, and the carrier wave 1 is It is sufficient to use the interval from the peak of It may be a distorted waveform that drops to the same level at an angle of 60 degrees.Here, for example, the frequency fc of carrier wave 2 may be set to 3.
Assuming that the frequency is 3 kHz, H = 255, and m = 256, the sine wave data and time data I and ■ shown in FIG. 4 are obtained by the above calculation method.

Note that the time data I is for the case where the slope of the carrier wave 2 is positive, and the time data 2 is for the case where the slope of the carrier wave 2 is negative.

Moreover, as shown in FIG. 5, the approximate sine wave PIIM
When outputting a waveform, data on the number of steps for selecting the sine wave data and time data is determined according to the target frequency of the approximate sine wave, and data on the number of steps is stored in a third memory. . That is, for example, in the case of a target frequency of 20, "1", "2", "
2" step data is repeated, and the sine wave data r4 J, r13J, r19Jr22J, r29J, r
35J, r38J, r..." corresponds, and if the target frequency is 60 or less, "4", "5", "5", "5"
The step data is sine wave data r16J, r3
2J.

"..." and "..." correspond.

In this way, the first, second and third memories 6a, 6
The waveform data stored in the waveforms b and 6c only needs to be the sine wave data of the sine wave 1 and the predetermined carrier wave 2, time data, and step number data, and does not need to be obtained for each target frequency of the approximate sine wave, for example.

Next, the operation of outputting the PvM waveform based on the data in the ROM 6 will be explained based on the flowchart of FIG. 6 and the time chart of FIG. 7.

Note that the first to third memories 6 a, 6 b, 6
Data obtained by setting the carrier frequency fc to 3.3 kHz (sine wave data, time data ■, time data ■,
Step number data) are stored.

First, when a frequency command (for example, 20 cells) of a PIIM waveform of an approximate sine wave is issued, the control unit 5 reads data S (r I J) of the number of steps corresponding to the command frequency from the third memory 6c. (Step 5TI).

Next, the internal timer of the control unit 4 (2/fc=152 μs
) is activated (step 5T2), and it is determined whether the internal timer has timed up (step 5T3).
If the 152 μs internal timer has not timed up, it is determined whether or not the frequency command has changed (step 5T4). If there is no change in the frequency command, the process returns to step ST3 and the internal timer has timed up. Until then, steps ST3 and Sr1 are repeated. Then, one interrupt is generated due to the time-up of the internal timer, and the number of steps R for reading out the sine wave data of the I-th memory 6a is calculated based on the data of the number of steps read out (step 5T5). In this case, Since the initial step number data S is "1", R=R+S=O+1 (in the initial state, R
= O), the step number R=1 is obtained, and based on this step number R, the read address Acc=Acc+R of the sine wave data is calculated (step 5T6).
That is, the read address Acc of the sine wave data is one after the first address A, (=O), and the sine wave data read from the first memory 6a is "4". Next, it is determined whether the carry flag is "1" by calculating Acc=Acc+R (Sr7). In this case, since Aec>255, the sine wave data read out as described above is "1". 4
” (Sr8) 6 Then, the slope KC of carrier wave 2
is incremented by +1 (STIO), and the L of this KC is incremented by +1 (STIO).
A determination is made whether the SB is 111 II (S
TII). That is, when the LSB is "1", the slope of the carrier wave 2 is determined to be negative, and when the LSB is l (On), the slope of the carrier wave 2 is determined to be positive. In this case,
Since the initial value is 0, KC=1, so time data ``73'' is read out (ST12).

In this way, the time data "73" read from the second memory 6b is set in the real timer of the control unit 5 (step 5T13).

Further, when the real timer is set, the real time I/O port output of the control section 5 is controlled, and the process returns to step ST3. In this case, data "2" for the next number of steps is read from the third memory 6c, and the internal timer is operated again. Furthermore, as in the case of the step number data rlJ, when the internal timer of 152 μs times up, an interrupt occurs, and the address Ace for reading the sine wave data is obtained based on the step number data "2". That is, the number of steps R=R+S is 1+2, and the address Ace is A,
Since 10R=3, the sine wave data read from the first memory 6a becomes "13" (Sr9), and then,
KC=KC+ 1 = (0001), +1 = (00/
O) is performed (STIO), and this LSB becomes "O" (ST11), so the time data read from the second memory 6b becomes "T82" (ST14).
), when this time data "82" is set in the real timer of the control section 5 (ST13), the real time I/O port output of the control section 5 is controlled and the process returns to step STI. Then, in the same manner as described above, data "2" for the next step number is read out from the third memory 6c, and based on this data "2" the step number R=3+
2=5 is obtained, and the address Acc=Acc+R from which the sine wave data is read is set to 5.

Next, by using the address Ace, the sine wave data “1” is sent.
9” is read out, and furthermore, KC=KC+1=(00/
O)2+1=(0011), L
Since SB becomes Pa1″, its sine wave data “19”
The time data "67" corresponding to the time data "67" is read out, and this time data "67" is set in the real time of the control section 5.

Furthermore, when the real time is set, the real time I/O port output of the control section 5 is controlled and the process returns to step ST3. In this case, since the step number data is "l", "2", and "2", the data is sequentially and repeatedly read out, but this data reading is repeated until one frequency command changes in step ST4. .

Further, when there is a change in the frequency command, step data for this changed frequency is read out (ST15), and the same processing as described above is performed.

On the other hand, when the real time of the control section 5 is set, the real time I/O output is inverted controlled every time the set time data elapses. Therefore, as shown in FIG.
In the above case, when the time of time data "73" set in real time has elapsed, the output of the real time I/O port is inverted, and for example, if it is at "HI+ level", the level is inverted to "u L j". Furthermore, at the same time as the time data is set, an internal timer starts, and the above time data "82
'', the output of the real-time I/O port is inverted from the It L 71 level to the tt Htp level. Furthermore, in the next 152 μs,
When the above time data “67” has elapsed, the output of the real-time I/O port changes from II HI+ level to “
It is inverted to L” level. Also.

In the above embodiment, Acc is a byte (8 bits) data, and if Acc>255 is exceeded, that is, if the carry flag becomes It I II as a result of the calculation, it is determined that half a cycle of the sine wave has been output. We have to invert the sine wave. Therefore, in step ST7, if the carry flag is determined to be "work", arithmetic processing of carrier wave slope KC=KC+1 is performed (Sr1), making it possible to invert the sine wave. Note that since Acc is byte data, it contains the value Acc=Ace -256.

In this way, the real-time I/O port of the control unit 5 outputs "H" and 'L" level signals similar to the signals shown in FIG.
It becomes a waveform. Therefore, by combining the waveform data in the first memory 6a, it is possible to obtain approximate sine wave PIIM waveforms of various target frequencies, so that the memory capacity does not increase each time the target frequency increases.

[Effects of the Invention] As explained above, according to the approximate sine wave PWM waveform output method of the present invention, a sine wave is equally divided into arbitrary sections,
The height value of the sine wave in each division is taken as sine wave data,
Find the position where these height values intersect with the carrier wave, obtain time data from the interval from the trough or peak of the carrier wave to that position, and also obtain the target frequency of the P8 waveform output of the approximate sine wave. Obtain step data to select the above sine wave data and time data according to
The time data based on the step data is set in the real timer of the microcomputer in a cycle of half the period of the carrier wave, and the output waveform from the real-time I/O port of the microcomputer is converted into an approximate sine wave P
Since the WM waveform is used, the target frequency of the approximate sine wave PVM waveform output can be changed using step data, and since the amount of waveform data (sine wave data, time data, and step data) can be reduced, the memory capacity is small. PV of sine waves with different target frequencies
This has the effect that M waveform output can be obtained.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention, in which the PI of an approximate sine wave is
A schematic diagram of the control circuit to which the IIM waveform is applied, FIGS. 2 and 3 are diagrams for explaining calculation of the PWM waveform data of the approximate sine wave, and FIGS. 2 and 3 are diagrams for explaining data calculated by the method shown in FIG. 3, and FIGS. 6 and 7 are flowchart diagrams and time chart diagrams for explaining the output operation of the PvM waveform of the approximate sine wave, FIG. 8 is a diagram for explaining a conventional method of calculating PWM waveform data of an approximate sine wave, and FIG. 9 is a schematic block diagram of a control circuit to which the conventional method shown in FIG. 8 is applied. In the figure, l is a sine wave, 2 is a carrier wave (triangular wave), 5 is a control unit (microcomputer), and 6 is a ROM (memory).
, 6th is the first memory (for sine wave data), 6b is the second memory
memory (for time data), and 6c is a third memory (for data on the number of steps). Figure 1 Figure 2 Figure 5 Time data settings Time data settings Time data settings Figure 6

Claims (4)

[Claims] (1) Divide the sine wave into equal parts, store the height value of the sine wave at the divided points in the first memory as waveform data, and calculate the height value from the peak or valley of the carrier wave superimposed on the sine wave. Step data for storing the interval to a predetermined position of the carrier wave corresponding to the height value in the second memory as time data, and reading out the waveform data in the first memory according to the frequency of the target waveform is stored in the third memory. The waveform data is read out based on the step data corresponding to the frequency of the target waveform, and the time data corresponding to this waveform data is sent to the real timer of the microcomputer in a cycle of half the period of the carrier wave. Set the microcomputer's real time I
An approximate sine wave PWM waveform output method, characterized in that the output of the /O port is an approximate sine wave PWM waveform output. (2) The waveform data stored in the first memory is the height value of the sine wave at the center of the equally divided section or the end of the section, or the average height value of the sine wave in the section. The approximate sine wave PWM waveform output method according to claim (1). (3) The sine wave has a distorted wave at an electrical angle of 60 degrees to 120 degrees, and the waveform data to be stored in the first memory is obtained by an approximate sine wave having this distorted wave. Or (2) the approximate sine wave PWM waveform output method. (4) The sine wave has a distorted wave whose height value at an electrical angle of 90 degrees is about the same level as the height value at an electrical angle of 60 degrees, and the approximate sine wave having this distorted wave is PWM of an approximate sine wave according to claim (1) or (2), wherein waveform data to be stored in the first memory is obtained.
Waveform output method.