JP2990779B2 - Signal waveform generation circuit by microcomputer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal waveform generation circuit by a microcomputer that generates and controls a reference signal waveform used in an inverter, a communication signal power supply, and the like.

[Conventional technology]

LS for microprocessor, memory and digital control
With the advancement of I technology, digital control using a compact, high-performance, low-cost microcomputer has been widely applied.

Conventionally, a microcomputer used to generate a reference sine wave signal for inverter PWM control has a frequency divider circuit.
A PLL converter, an address counter, a sine wave data ROM, and the like were provided as auxiliary circuits.

FIG. 2 shows a signal waveform generating circuit using a microcomputer according to the prior art.

In Figure 2, CPU in the microcomputer unit 10 for inputting a clock signal of _{5MH Z, ROM, RAM, I} / O ports, the counter-timer is built, 1 kH _Z from the counter timer
Is sent to the PLL conversion unit 11.

The signal from the counter / timer is a square wave, which is set to 20 times the frequency of the reference sine wave signal output from the D / A converter 14 at the final stage. That is, for 50H _Z
1 kH _Z, for 60H _Z is 1.2KH _Z.

The PLL converter 11 uses a PLL IC, shapes the input frequency (square wave), converts the input frequency (frequency) to a frequency 50 times, and inputs the frequency to the address counter 12.

The address counter 12 is configured by an F / F or the like, and is a counter that detects an input square wave at a rising (or falling) edge and outputs the signal as a binary 10-bit signal.

Sine wave data ROM13 is a one that writes the data of 1000 pieces of the address 0 of the address, the maximum value of the sine wave amplitude and FF _H, OO _H the minimum value, the input clock signal 50KH
_{For Z} , 1000 pieces of data decomposed every 20 μs
It is stored as the sine wave data of the cycle and is as shown in FIG.

D / A converter 14, the data up to OO _H to ff _H is a parallel signal of 10 bits outputted from the sine wave data ROM13 into an analog signal, and outputs it as a sine wave 50H _Z.

[Problems to be solved by the invention]

As mentioned above, the reason that there are many auxiliary circuits in the microcomputer
This is because not only the purpose of generating the reference sine wave signal but also the purpose of supplying a clock signal of a different frequency from the microcomputer unit and its accompanying circuit to an external circuit.

However, extracting various clock signals having different purposes of use not only complicates the circuit configuration, but also does not allow the microcomputer function to be sufficiently exhibited, and increases the dimensions due to the increase in the number of components. And increased production costs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described drawbacks, and has been made to simplify the purpose of use of a microcomputer and to limit the generation and control of a reference signal waveform.

That is, by supplying different clock signals for different purposes from a separate circuit, the above-described complicated auxiliary circuit is omitted, and a signal waveform generation circuit is provided by a simple microcomputer capable of arbitrarily generating and controlling a reference signal waveform. What you want to do.

[Means for solving the problem]

In order to solve the above-described problems, a signal waveform generation circuit using a microcomputer according to the present invention includes a microcomputer section including a CPU, a RAM, a ROM, a counter / timer, an I / O port, and the like, and an output signal of the microcomputer section. A D / A converter for converting a bit parallel signal into an analog signal waveform, means for storing signal waveform data and waveform data transmission timing as a program, and converting the stored signal waveform into an n-bit parallel signal. And a means for changing the frequency of the zero-crossing switching signal and the signal waveform at the zero-crossing point based on a program storing the signal waveform data and the waveform data transmission timing, and a timer interrupt function provided in the microcomputer unit. Generates the above-mentioned arbitrary signal waveform.

[Action]

The signal output from the microcomputer to the D / A converter is 12.
8KH _Z, is an 8-bit.

The EEP · ROM built in the microcomputer unit and the address of one cycle OO _H to FF _H (16 hex), stored reference signal waveform data the maximum value of the amplitude and FF _H, OO _H a minimum Have been.

That is, since the address is 8 bits, one cycle takes 25 times.
The signal waveform data divided into six equal parts are stored at the following time intervals.

1 / 12.8 × 10 ³ = 78.125 μs This reference signal waveform data is output from the I / O port to the D / A converter via a timer interrupt function provided in the microcomputer unit and is converted into an analog signal waveform.

In the conventional example, the signal waveform data is obtained by dividing one cycle into 1,000 equal parts. However, even with 256 equal parts, the signal waveform data can be stored and reproduced sufficiently accurately.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a signal waveform generation circuit using a microcomputer according to the present invention.

Clock signal generating circuit 3 sends a clock signal of 10 MHz _Z to the microcomputer unit 1.

The microcomputer unit 1 includes a CPU, a RAM, and an EEP, which are activated by a built-in timer interrupt function via the clock signal.
-It is composed of ROM, counter / timer, I / O port, etc.

The output signal from the I / O port to the D / A converter 2 of the microcomputer unit 1 is a 8-bit signal 12.8KH _Z, the signal waveform is converted into an analog signal waveform 50H _Z in the D / A converter 2.

The above-mentioned signal waveform data is stored in the EEPROM of the microcomputer unit 1.
The signal waveform data is stored as an 8-bit signal every 78.125 μs (1s / 12.8 × 10 ³ ) after frequency division.

As described above, since the signal waveform data stored in the EEPROM / ROM of the microcomputer unit 1 is directly output to the D / A converter 2 via the I / O port, the signal waveform data is provided in the circuit of the related art. Does not have a feedback circuit.

Therefore, the analog signal waveform can be converted to D / A without time lag.
It will be output from the converter.

Further, since the signal waveform data and its transmission timing are stored as a program, it is possible to transmit or stop an arbitrary signal waveform at an arbitrary timing.

That is, it is possible to output a switching signal at a zero cross by setting to transmit a pulse at an arbitrary predetermined point of the signal waveform data in advance, and it is also possible to output the timing of the signal waveform data with the zero cross point as a boundary. Can be adjusted to change the frequency of the reference signal waveform.

FIG. 5 is a waveform diagram showing a change in the frequency of the reference signal waveform, and FIG. 5 (a) shows a case where the frequency is increased.
FIG. 2B shows a case where the frequency is lowered.

The various means described above can be realized by operating a program storing the signal waveform data and the transmission timing of the waveform data by the timer interrupt function provided in the microcomputer unit 1, and the operation flow is shown in FIG. .

In FIG. 3, a system initialization (101) is a routine for setting an I / O port of the microcomputer unit 1 and setting a timer interrupt time, and the system monitoring (102) is performed in a loop during normal operation. This is a routine for performing a sequence of processes (start, stop, etc.). The timer interrupt (103) jumps according to the setting of the timer interrupt. Each time the timer jumps by the interrupt, data is fetched from the signal waveform data table (10
4), by outputting data to the I / O port (105), the various means described above are executed.

〔The invention's effect〕

As described above, the signal waveform generation circuit of the microcomputer according to the present invention includes the microcomputer unit storing the output signal waveform as a program and the D / A converter for converting the output signal of the microcomputer unit into an analog signal. This eliminates the need for a sine wave data ROM, address counter, and PLL converter provided as an auxiliary circuit of the signal waveform control circuit using a conventional microcomputer.

Therefore, the manufacturing cost is reduced due to the decrease in the number of parts,
There is an effect that the size of the substrate can be reduced.

Also, since the signal waveform stored in the ROM built in the microcomputer is directly output to the D / A converter, it can be output as an analog signal waveform without time lag, and the signal waveform data and its transmission timing are stored as a program. Therefore, there is an advantage that the transmission of the zero-cross switching signal and the frequency change of the signal waveform can be performed.

[Brief description of the drawings]

1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram according to the prior art, FIG. 3 is a flowchart showing a timer interrupt operation, FIG. 4 is a signal waveform diagram stored in a ROM, FIG. FIGS. 7A and 7B are waveform diagrams showing a change in signal waveform frequency. 1... Microcomputer section 2... D / A converter 3... Clock signal generation circuit.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-63982 (JP, A) JP-A-63-164602 (JP, A) JP-A-62-195903 (JP, A) 136178 (JP, A) JP-A-58-81603 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H03B 28/00 H02M 7/48

Claims (1)

(57) [Claims] A means for storing signal waveform data and transmission timing of the waveform data as a program, comprising: a CPU, a RAM, a ROM, a counter / timer, an I / O port, and the like; and a signal waveform data described in the program. , As a n-bit parallel signal, a means for sending a zero-cross switching signal by setting a pulse sending point in the signal waveform data stored in the program, Means for changing the frequency of the signal waveform by changing the transmission timing of the signal waveform data at the zero-crossing point of the signal waveform data.The above means are provided by a built-in timer interrupt function via a clock signal input. The microcomputer to be executed, and the n-bit parallel input through the I / O port of the microcomputer And a D / A converter for converting a digital signal into an analog signal waveform.