JPS58147231A - Generating device of signal applied with pulse-width modulation - Google Patents

Abstract

PURPOSE:To improve the processing functions of a microprocessor other than PWM signal generation, by shortening the time when the microprocessor is dedicated to the PWM signal generation. CONSTITUTION:The microprocessor 13 operates according to a PWM signal generating program written in an RDM24; each time an interruption pulse is generated by an interruption point generating counter 23 for generating the point of time of interruption to the microprocessor, the microprocessor generates the instantaneous value of a modulated wave signal on the basis of the counted value of a modulated-wave address counter 21, a waveform data table of the modulated waves stored in an ROM24, amplitude values of the modulated waves supplied as a command, and the instantaneous value of a carrier signal from the counted value of a carrier generating counter 22 respectively. From both values, a set value for a PWM signal generating counter 26 is calculated and the result is set in the PWM signal generating counter 26.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for generating a pulse width modulation signal used as a gate pulse of a pulse width modulation inverter.

Generally, a pulse width modulation signal (hereinafter abbreviated as a PWM signal) consists of a signal 1 called a modulated wave, which is usually a sine wave, and a signal 2, which is usually called a carrier wave, which is a triangular wave.
Signal 3 is obtained by comparing the magnitudes of .

Conventionally, as a method of generating a PWM signal using the above method, a modulated wave signal and a carrier wave signal are generated using discrete hardware, and the magnitudes of the two are compared using a digital comparator, and based on the magnitude relationship, There is a method to obtain this by switching the state of a flip-flop. The configuration of the PWM signal generator using this method is as shown in FIG. The obtained carrier wave signal and the clock pulses are divided by the division counter 5, and the frequency pulses proportional to the nine modulated waves are counted by the counter 7, and the harmonic table 9 is indexed from the counted value. A digital comparator 10 compares the magnitude with the modulated wave signal obtained by using the digital comparator 10 to generate a PWM signal.

In this method, functions from generating the modulated wave signal and carrier wave signal to comparing the sizes of the two are performed using discrete hardware, so the hardware is designed and manufactured according to the required specifications. , a PWM signal generator having the necessary functions can be obtained. However, this method is constructed using discrete hardware, and the hardware configuration is complicated by the logic circuits required to generate the modulated wave signal and carrier wave signal, and the circuits required to synchronize both signals. The drawback was that it was very complex. Furthermore, the circuit configuration lacks versatility, and when changing or adding a PWM signal generation function, the hardware has to be redesigned.

In contrast, the microprocessor and memory
Using a counter, etc., which is a four-sided element, functions such as generating a modulated wave signal and a carrier wave signal and comparing the magnitudes of both signals are performed by software processing of a microprocessor, and PWM can be performed without using special hardware elements.
A method of generating a signal has been proposed. The configuration of a PWM signal generator according to this method is shown in FIG. 3, which includes a microprocessor 13, a circuit 11 for generating a carrier signal, a circuit 12 for generating a modulated wave signal, Timer 1 that gives the interrupt processing time
5. It is composed of a programmable counter 14 which counts clock pulses outputted from the clock pulse generator 4 to which data is set from the microprocessor, and outputs a pulse after a time corresponding to the set data.

The operation of PWM signal generation using this method will be explained using FIG. 4. The microprocessor 13 calculates the instantaneous values of the modulated wave signal l and the carrier wave signal 2° at that time for each interrupt pulse of a constant dark period outputted from the timer IS, and calculates the difference in magnitude between the two signals ΔNt carrier wave frequency. proportional 7'tf
The programmable counter 14 is set to count clock pulses of f wave number. This counter 14 counts the clock pulses, and the count value 16 changes as shown in FIG. The set value ΔN corresponds to the time from when it is set until the time when the next modulated wave and the carrier wave intersect.At the 9th time, when the counter 14 finishes counting the set value, the modulated wave 12 and the carrier wave 11 intersect. It corresponds to the time when and intersect.

Therefore, pulse 1 output from this counter 14
A desired PWM signal 3 can be obtained by inputting the signal to a 7t flip-flop and switching its state every time a pulse is input.

This method has the advantage of having versatility in the hardware circuit configuration centered on the microprocessor, and being able to adapt to changes and expansions in the t+pwM signal generation capability. ,-A timer is used to generate an interrupt pulse that gives the microprocessor processing time point 1,
The microprocessor takes steps to generate a PWM signal at regular intervals regardless of the carrier wave frequency. With this method, the carrier wave signal and the interrupt pulse output from the timer are not synchronized, and the interrupt synchronization from the timer becomes long and becomes about the same as the carrier wave period, and the PWM signal cannot be generated correctly next time. There is. This will be explained using Figures 5 and 6.6 Both cases are the same carrier frequency and the same interrupt period T3, but in the case of Figure 5, the correct PWM
In the case of Fig. 6, an incorrect PW is generated.
Generating M signal.

That is, as shown in FIGS. 5 and 6, when the carrier wave signal 2 and the interrupt pulse 18 are asynchronous, if the interrupt period becomes longer than the carrier wave period, a correct PWM signal cannot be obtained. Therefore, in order to avoid such a phenomenon, it is essentially necessary to make the synchronization T1 of the interrupt pulse 18 as short as possible. The microprocessor is required to perform the ninth interrupt process of PWM signal generation at as short a period as possible regardless of the high or low carrier frequency, and the microprocessor is dedicated to the PWM signal generation process. As a result, the microprocessor cannot be responsible for processing other than PWM signal generation, and the advantage of time-sharing processing, which is a feature of the four-microphone processor system, cannot be utilized.

An object of the present invention is to reduce the time that the microprocessor devotes exclusively to PWM signal generation in a companion PWM note generation method using a microprocessor and its same side elements, and to perform processing other than PWM signal generation such as system abnormality diagnosis. We provide a PWM code generator that can be shared.

The feature of the present invention is that, as shown in FIG.
9 is used to divide the clock pulse output from the clock pulse generator 4, and the resulting signal t-r is applied to the microprocessor as an interrupt pulse giving the processing time of the microprocessor, thereby determining the interrupt processing time. This is to synchronize with the carrier wave signal.

With this method, as shown in FIG.
can be synchronized to the point in time when the value of carrier wave signal 2 having a triangular waveform becomes maximum and minimum, and the intersection point of this next modulated wave signal 2 and carrier wave signal 1 can always be accurately determined. Therefore, as shown in FIG. 8(d), a highly accurate PWM signal 3 can be obtained even if the number of interruptions during one carrier wave period is small.

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

The /1-ware configuration of the PWM signal generator according to the present invention is shown in FIG. 9, and its operating waveforms are shown in FIGS. 10 to 12. In FIG. At the output of the clock pulse generator 4 that generates the frequency multiplier pulse, a ninth frequency division counter 2G that generates a modulated wave signal, a modulated wave address counter 21, a rounded carrier wave generation counter 22 that generates a carrier wave signal, and a microbe. An interrupt point generation counter 23 for giving an interrupt processing point to the processor, and a PWM signal generation counter 26 whose setting value is reset every interrupt point from the microphone processor are connected to each other. 4. The microprocessor operates according to the PWM signal generation program written in the ROM 24, and for each interrupt pulse from the interrupt time generation counter, counts the count value of the modulated wave address counter and the ROM 24. The instantaneous value of the modulated wave signal is calculated from the nine modulated wave waveform data tables and the modulated wave amplitude value given as a command, and the instantaneous value of the carrier wave signal is calculated from the counted value of the carrier wave generation counter 22, and from both values. Calculate the set value for the PWM signal generation counter p26,
The result is set in the PWM signal generation counter 26. P
The WM signal generation counter 26 counts the clock pulses outputted from the clock pulse generator 4, and when it finishes counting the set value set from the microphone processor 13,
Outputs pulses. By switching the state of the flip-flop 27 using this pulse output, a desired PWM signal is generated.

Next, the operation of PWM signal generation according to this method will be explained using FIGS. 10 to 12. The carrier signal is
The lock pulse 28 as shown in FIG. 10(a) is counted by the carrier wave generation counter 22 to obtain a triangular wave shaped signal 29 as shown in FIG. 10(b3).

On the other hand, for the modulated wave signal, the clock pulse 28 is first frequency-divided by the division counter 20 to obtain a clock pulse 30 having a good wave number and proportional to the modulated wave as shown in FIG. 11(b). By counting the clock pulses 31 with the modulated wave address counter 21, a sawtooth waveform count value 31 is obtained in which the count value is reset every cycle of the modulated wave as shown in FIG. 11(C). By reading out data using this count value as a read address of the harmonic waveform data table stored in the ROM, a modulated wave signal 32 having a sinusoidal waveform as shown in FIG. 11(d) is obtained. The process of generating a PWM signal from the carrier wave signal and modulated wave signal obtained in this manner will be explained using FIG. 12. first,
The interrupt pulse that gives the processing time point to the microprocessor is obtained by counting the clock pulse 28 with the interrupt time occurrence counter 23, and the count value of the 0 interrupt time occurrence counter changes as shown in FIG. 12(C). , when the count value becomes zero, the count value is reset, and at this time a pulse as shown in FIG. 2(d) is output. The interrupt pulse 34 output from this counter counts the same clock pulses 28 as the one used to generate the carrier wave signal, so that the interrupt pulse 34 output from this counter is the carrier wave signal. It is synchronized with 2. FIG. 12 shows a case where interrupt pulses are input 94 times per carrier wave cycle. The microprocessor obtains the instantaneous values of the carrier wave signal 2 and the modulated wave signal 1 by the method described above for each interrupt pulse, and sets the difference between the two in the PWM signal generation counter. This counter counts the clock pulses 28 and the count value changes as shown in FIG. Since this pulse output 17 coincides with the intersection of the modulated wave signal 1 and the carrier wave signal 2, by switching the state of the flip-flop 27 for each pulse, a PWM signal 3 as shown in Fig. 812 is obtained.

As described above in this embodiment, by dividing the black and tsuku pulses of the same wave number proportional to the carrier wave into interrupt pulses that give the processing time of the microprocessor, synchronization is achieved with the carrier wave signal at the interrupt time. As a result, even if the number of interrupt processing per carrier-synchronization is smaller than when the interrupt time is asynchronous, the IAPW with better accuracy can be used.
The overall time that the M signal generator is dedicated to PWM signal generation can be shortened, and the microprocessor can perform functions other than PWM signal generation processing (for example, abnormality diagnosis of the entire system including PWM signal generation, etc.). functions).

In addition, although the above explanation was given only for one phase, it is clear from the principle that mineralization can be easily applied to three phases.

According to the present invention, it is possible to shorten the time that the microphone α processor devotes exclusively to PWM signal generation, so that the microprocessor is assigned to handle processes other than PWM signal generation.
Functionality can be improved.

[Brief explanation of drawings]

Fig. 1 is a diagram of the principle of PWM signal generation, Fig. 2 is a block diagram of a conventional digital PWM signal generator, and Fig. 3 is a fcPW using interrupt pulses from a timer at regular intervals.
A configuration diagram of the M signal generator, FIG. 4 is an operational waveform diagram of FIG. 3, FIGS. 5 and 6 are operational waveform diagrams showing that the interrupt period cannot be shortened, and FIG. 7 is a PWM generation according to the present invention. FIG. 8 is an operational waveform diagram of FIG. 7, FIG. 9 is a configuration diagram showing an embodiment of the present invention, and FIGS. 10 to 18 are operational waveform diagrams. 1...Modulated wave signal, 2...Carrier wave signal, 3...P
WM signal, 4... Clock pulse generator, 13...
Microbe processor, 14... Programmable counter, 20... Frequency division counter, 21... Modulated wave address counter, 22... Carrier wave generation counter, 23...
・Interrupt time occurrence counter, 24...ROM, 25...
・RAM. 26...PWM signal generation counter, 27...Flip=172! l, S's mouth & Figure 811 Figure 61z mouth

Claims (1)

[Claims] 1. A microprocessor and a memory for operating it; a clock pulse generator in which data is set by the microprocessor and generates a clock pulse of a desired frequency in response to the data; a set value is written by the microprocessor; , consisting of a counter that counts the clock pulses with the set value as an initial value, and the microprocessor performs calculations at predetermined intervals and writes the results to the counter to generate a pulse width modulation signal. 2. A pulse width modulation signal generating device according to claim 1, wherein the interrupt pulse for synchronizing the operation of the micro processor is obtained by dividing the simple pulse.