JPH11345033A - Method for controlling modulation of pulse width by microcontroller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to execute high speed and stable control even in the case of using an inexpensive microcontroller by setting up a timer/counter value indicating the time until interruption is generated in a main process and after the lapse of the time, generating the interruption in the main process and inverting an output signal. SOLUTION: First and second control signals TC1 , TC2 are determined based on an input signal and a timer/counter value indicating the time until interruption is generated in a main process, is set up based on the 1st and 2nd control signals TC1 , TC2 . When an interruption request is generated when an output signal is Low, a High signal is outputted (S12a). Then, an interruption request is generated after the lapse of a control variable TC1 determined by a main routine so that the Low signal is outputted (S12b). Further, an interruption signal is generated after the lapse of a control variable TC2 so that the High signal is outputted (S12a). Thereafter, a similar process is repeated up to reaching a prescribed time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse width modulation control method using a microcontroller suitable for controlling operations of a motor, a solenoid coil, a buzzer, and the like. The present invention relates to a pulse width modulation control method using a microcontroller capable of improving speed.

[0002]

2. Description of the Related Art As a method of variably controlling operations of a motor, a solenoid coil, a buzzer, and the like, there is, for example, a pulse width modulation (PWM) control method. FIG. 8A shows a conventional P
FIG. 2 is a block diagram showing a circuit used in the WM control method;
(B) is a timing chart showing the output waveform at that time. In a circuit used in the conventional PWM control method, one terminal of a load 22 to be controlled is grounded, and an output circuit 23 is connected to another terminal. Output circuit 2
3 is connected to a microcontroller 21 that performs PWM control. Further, an input device 24 to which a signal to be controlled is input is connected to the microcontroller 21. In the microcontroller 21, a program including a main routine and an interrupt routine is stored, and a central processing unit (CPU) 21a that controls an output signal.
The CPU 21a is provided with a timer / counter 21b for generating an interrupt request, and signals are exchanged between the CPU 21a, the input device 24, and the output circuit 23.

In addition, for example, 100 ms is written into the timer / counter 21b as a timer / counter value (TC value) as a control variable from the CPU 21a.
An interrupt request is issued from the timer / counter 21b to the CPU 21a at a cycle of the C value (100 ms). In the CPU 21a, a counter called a software counter (hereinafter, referred to as an S counter) is counted up by the interrupt request. Microcontroller 2
The waveform of the signal output from the output circuit 1 to the output circuit 23 is shown in FIG.
(B), the is a pulse waveform, the pulse period T and pulse width T ₁ is controlled on the basis of the S counter. Then, a duty ratio (T ₁ / T × 100 (%)) which is a ratio of the pulse width T ₁ to the pulse period T
Is variably controlled by the microcontroller 21 between 0% and 100%.

In the conventional PWM control circuit configured as described above, an input signal such as an analog signal is input to the input device 24, and the input signal is input by the microcontroller 21 as shown in FIG. It is converted into a pulse wave. Then, it is output to the load 22 via the output circuit 23.

Next, a specific method of controlling the duty ratio by the conventional PWM control method will be described. FIG. 9 is a flowchart showing a main routine in a conventional PWM control method, and FIG. 10 is a flowchart showing an interrupt routine similarly.

In the main routine, as shown in FIG.
When an input signal is input from the input device 24, the input signal is read by the CPU 21a (step S51).
Then, the pulse width T ₁ is determined on the basis of the input signal (step S52). Then, the value of the S counter is determined whether the pulse width greater than T ₁ (step S53).
Then, the signal of High is output when the value of the S counter is greater than the pulse width T ₁ (step S54a),
Otherwise, a Low signal is output (step S54b). Next, it is determined whether the value of the S counter is greater than the pulse period T (step S55). If the value of the S counter is larger than the pulse period T, the value of the S counter is cleared (cleared) to 0 (step S56). Otherwise, the process returns to step S51 as it is.

On the other hand, in the interrupt routine, when an interrupt request is generated from the timer / counter 21b at the cycle of the TC value,
As shown in FIG. 10, the TC value is set in the timer / counter 21b (step S61). Next, the value of the S counter is incremented (+1) (step S6).
2) The steps in the interrupt routine are completed. That is, TC
If the value is, for example, 100 ms, an interrupt occurs every 100 ms and the program transitions from the main routine to the interrupt routine, and the S counter has 100 ms, 200 ms, 300 ms, 400 ms,.
・ It is counted up.

As described above, in the conventional PWM control method for electronic components, the S counter is counted up by interruption at a constant period (TC value), and the duty ratio is controlled based on the S counter. .

[0009]

However, in the above-described conventional PWM control method, if an interrupt cycle is set to be small in order to obtain a high resolution using an inexpensive microcontroller, the entire interrupt time is reduced. There is a problem that the ratio becomes large and the processing becomes slow. FIG. 11A is a timing chart showing an interrupt timing in the conventional PWM control method, and FIG. 11B is a timing chart in which this is enlarged in the time axis direction. Assuming that the interrupt cycle, which is the minimum time of the S counter, is T _i , and the time required for the interrupt routine required to count up the S counter is t _i , the ratio R of the interrupt processing time to the entire control is as follows. It is shown by Equation 1.

[0010]

## EQU1 ## R = t _i / T _i × 100 (%)

Therefore, for example, if the interrupt cycle T _i is 100 μm
s, when the required time t _i is 30 μs, 30% of the entire control
Will be spent on interrupt processing. Thereby, PW
The entire control processing by the main routine including the control routine in addition to the M control is 30 times more than when there is no interrupt routine.
% Delay.

Further, when the necessary time required for the main routine one cycle and T _m, the period T _i of the interruption is less than the required time T _m, interruption while the main routine is one round It may take two times, and the value of the S counter may be T _S at the n-th cycle of the main routine, and T _S +2 at the (n + 1) -th cycle of the main routine. In this case, an error occurs in the timing of the rising or falling edge of the output waveform, and the control becomes unstable.

Further, if the interrupt cycle T _i is set smaller than the required time t _{i of the} interrupt routine, an interrupt request is issued again during the interrupt processing, and an infinite loop occurs. This causes a program runaway.

On the other hand, if a high-speed microcontroller is used, it is possible to stably control the output duty ratio with high resolution, but the high-speed microcontroller is extremely expensive.

The present invention has been made in view of such a problem, and provides a pulse width modulation control method using a microcontroller capable of performing high-speed and stable control even if an inexpensive microcontroller is used. With the goal.

[0016]

According to the present invention, there is provided a pulse width modulation control method using a microcontroller, which controls a duty ratio of an output signal output from the microcontroller based on an input signal input to the microcontroller. In the pulse width modulation control method by the controller, a main step of repeating a step of determining a first control variable and a second control variable based on the input signal; and the first control variable and the second control variable A timer / counter value setting step of setting a timer / counter value indicating a time until an interrupt is generated in the main step based on the timer; And an output inverting step of inverting the output signal.

In the present invention, since an interrupt is generated only when the output signal is inverted, the S counter is unnecessary, and the processing delay conventionally caused by the S counter is delayed. Is prevented.

The sum of the first control variable and the second control variable during each step repeated in the main step may be constant.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for controlling a PWM of an electronic component according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings. In this embodiment, the interval at which an interrupt request is generated is variable. That is, the interrupt request is not generated in a fixed cycle as in the related art. FIG. 1 is a flowchart showing a main routine in a PWM control method according to a first embodiment of the present invention, and FIG. 2 is a flowchart showing an interrupt routine similarly. The PWM control circuit used in this embodiment is the same as the conventional one shown in FIG.

In the main routine of the PWM control method according to the present embodiment, as shown in FIG. 1, when an input signal is input from an input device, the input signal is read by the CPU (step S1). Next, the control variable TC ₁ (> 0) is determined based on the input signal (step S2), and the control variable TC ₂ (> 0) is determined (step S3). The control variable T determined by the same main routine
The sum of the C ₁ and the control variable TC ₂ is always set to match the cycle T of the output pulse. Then, step S1
The process returns to.

On the other hand, in the interrupt routine of the PWM control method according to the present embodiment, when an interrupt request is generated from the timer / counter, as shown in FIG.
It is determined whether it is w (step S11). If the output is low, a high signal is set for the output (step S12a), and then the TC value is set to the control variable T.
C ₁ is set (step S13a). On the other hand, if the output is not Low in step S11, the output is Low.
The signal is set after was (step 12b), the control variable TC ₂ is set to the TC value (step S13b). Then, the process in the interrupt routine ends.

The signals controlled and output by the microcontroller in this manner are as shown in FIG. FIG. 3 is a timing chart showing output waveforms in the PWM control method according to the first embodiment of the present invention. That is,
If an interrupt request is issued when the output signal is low, H
high signal is output. Then, when the elapsed controlled variable TC ₁ determined by the main routine, the interrupt request is generated. Then, a Low signal is output. Further, when the elapsed controlled variable TC ₂ determined by the same main routine, the interrupt request is generated. Then, a High signal is output. Thereafter, the same process is repeated until a predetermined time is reached.

As described above, in this embodiment, the interrupt request is generated from the timer / counter only when High and Low of the output signal are inverted. For this reason, conventionally, an interrupt request is generated at a constant cycle to count up the S counter, and a delay occurs in other control. However, in the present embodiment, such a delay does not occur.

Further, since the timer / counter and the CPU operate independently of each other, the interval between the generations of the interrupt requests defined by the control variables TC ₁ and TC ₂ is stable. Therefore, no error occurs in the timing of the rising edge and the falling edge of the output, and a signal having a stable waveform is output by the PWM control.

Further, even if the control variables TC ₁ and TC ₂ are set extremely small to such an extent that the performance of the timer / counter is sufficiently exhibited, the interruption processing does not fall into an infinite loop. It is possible to control the ratio very finely. That is, even if the control resolution is increased, the program does not run away. The control resolution is determined by the resolution of the timer / counter.

Therefore, according to the present embodiment, short period S
Even if the counter is not used, the problems caused by the conventional PWM control method such as control delay, control instability, and program runaway can be solved. The use of a controller can be fully adapted.

That is, when a microcontroller having the same level of performance as the conventional one is used, PWM control is performed with finer control resolution and higher stability. Also, when trying to obtain the same level of control performance as before,
It can be adapted with cheaper and slower microcontrollers.

Although some microcontrollers have a built-in PWM-dedicated output port, the present invention can be sufficiently applied to a general-purpose output port without using a PWM-dedicated output port. Furthermore, when a general-purpose output port is used, the degree of freedom in setting the control resolution and the pulse period of the output signal is higher than when a dedicated output port for PWM is used.

Next, a second embodiment of the present invention will be described. This embodiment is an example applied to PWM control of an intermittent attenuation sound of a buzzer used for an alarm sound or the like. FIG. 4 is a block diagram showing a circuit used in the PWM control method according to the second embodiment of the present invention.

In the circuit used in the PWM control method according to the second embodiment, one terminal of the buzzer 2 to be controlled is grounded, and a buzzer output driver 3 is connected to the other terminal. The buzzer output driver 3 is connected to a microcontroller 1 that performs PWM control. Further, the microcontroller 1 is connected to an input switch (SW) 4 to which a signal to be controlled is input. Further, the microcontroller 1 stores a program including a main routine and an interrupt routine and controls an output signal.
A is provided with a timer / counter 1b for generating an interrupt request, and signals are exchanged between the CPU 1a, the input SW 4 and the buzzer output driver 3.

FIG. 5 shows a PWM according to a second embodiment of the present invention.
FIG. 6 is a flowchart showing a main routine in the control method, and FIG. 6 is a flowchart showing an interrupt routine in the same manner.

In the main routine, as shown in FIG.
The signal from the input SW4 is read (Step S2
1). Next, it is determined from this signal whether the input SW4 is turned on (step S22). And the input SW
4 is not turned on, the timer / counter 1
b is stopped (step S23b). Furthermore, the constant α is set to the control variable TC ₁ and TC ₂ (step S3
1, S32). Note that the value twice as large as the constant α matches the fundamental oscillation period of the buzzer 2, and the tone of the buzzer 2 is determined by the constant α. Thereafter, the timer for controlling the attenuation rate is cleared (step S33).

In step S22, the input SW
4 is turned on, the timer / counter 1b
Is driven (step S23a). Then, it is determined whether t (second) has elapsed since the last time the timer was cleared (step S24). If t (second) has elapsed since the last time the timer was cleared, the timer is cleared (step S25). Then, the control variable TC ₁ is decremented (-1) (step S26), the control variable T
C ₂ is incremented (+1) (step S2
7). Thereafter, it is determined whether the control variable TC ₁ is 0 (step S28). If the control variable TC ₁ is 0, constant α is set to the control variable TC ₁ and TC ₂ (step S29, S30). In the present embodiment, the initial value of the sum of the control variables TC ₁ and the control variable TC ₂ is 2.alpha,
Thereafter, the control variable TC ₁ is decremented, the control variable TC ₂ is being incremented, since the absolute value of the change amount is equal to the sum of the control variables TC ₁ and the control variable TC ₂ has a constantly 2α . The sum (2α) of the control variable TC ₁ and the control variable TC ₂ is the pulse period T.

[0034] Note that when not elapsed t (in seconds) at step S24, after when the control variable TC ₁ at step S28 is not zero and step S30 or step S33, step returns to step S21.

On the other hand, in the interrupt routine, when an interrupt request is issued from the timer / counter 1b, as shown in FIG. 6, it is determined whether the output signal at that time is low (step S41). When the output signal is Low, the signal of High is set to the output after was (step S42a), the control variable TC ₁ is set to the TC value (step S43a). On the other hand, if the output signal is not low in step S41, a low signal is set to the output (step 42b), and then the TC value is set to the control variable TC _2.
Is set (step S43b). Then, the process in the interrupt routine ends.

The signals controlled and output by the microcontroller are as shown in FIG. FIG. 7 is a timing chart showing output waveforms in the PWM control method according to the second embodiment of the present invention. That is,
If an interrupt request is issued when the output signal is low, H
high signal is output. Then, when the elapsed controlled variable TC ₁ determined by the main routine, the interrupt request is generated. Then, a Low signal is output. Further, when the elapsed controlled variable TC ₂ determined by the same main routine, the interrupt request is generated. Then, a High signal is output. Then, when the elapsed is determined by the new main routine is decremented controlled variable TC _1, an interrupt request is generated. Thereafter, the same process is repeated until the control variable TC ₁ becomes 0. Therefore, the duty ratio gradually decreases from 50% to 0%. That is,
While the input SW4 is turned on, the buzzer 2 emits an intermittent buzzing sound.

Also in the present embodiment, the interrupt request
What is generated from the counter is the High of the output signal.
And Low are inverted only. Therefore, similarly to the first embodiment, effects such as prevention of control delay can be obtained without using an expensive microcontroller.

[0038]

As described in detail above, according to the present invention,
Since the interrupt is generated only when the output signal is inverted, it is possible to prevent other controls from being disturbed by the interrupt. Even if the interrupt interval is set shorter, a stable output waveform is obtained without any error in the edge timing, and the stability of control is not reduced. Therefore, the control resolution of the duty ratio can be further reduced. Furthermore, even if the interrupt interval is set shorter, the program does not run out of control, so that the reliability of control is improved. The above-described effects can be obtained without using a high-speed microcontroller, so that cost can be reduced.
Further, since the microcontroller can be adapted as long as it has a general-purpose output port instead of a PWM-dedicated output port, the degree of freedom of selection is high.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a main routine in a PWM control method according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing an interrupt routine.

FIG. 3 is a timing chart showing output waveforms in the PWM control method according to the first embodiment of the present invention.

FIG. 4 is a block diagram showing a circuit used for a PWM control method according to a second embodiment of the present invention.

FIG. 5 is a flowchart illustrating a main routine in a PWM control method according to a second embodiment of the present invention.

FIG. 6 is a flowchart showing an interrupt routine.

FIG. 7 is a timing chart showing output waveforms in a PWM control method according to a second embodiment of the present invention.

8A is a block diagram showing a circuit used in a conventional PWM control method, and FIG. 8B is a timing chart showing an output waveform at that time.

FIG. 9 is a flowchart showing a main routine in a conventional PWM control method.

FIG. 10 is a flowchart showing an interrupt routine.

FIG. 11A is a timing chart showing an interrupt timing in the conventional PWM control method, and FIG. 11B is a timing chart in which this is enlarged in the time axis direction.

[Explanation of symbols]

 1, 21; microcontroller 1a, 21a; central processing unit (CPU) 1b, 21b; timer / counter 2: buzzer 3: buzzer output driver 4: input switch 22; load 23; output circuit 24;

Claims (2)

[Claims] 1. A pulse width modulation control method by a microcontroller that controls a duty ratio of an output signal output from the microcontroller based on an input signal input to the microcontroller. A main step of repeating a step of determining a control variable and a second control variable; and a timer / a timer indicating a time until an interrupt is generated in the main step based on the first control variable and the second control variable. A timer / counter value setting step of setting a counter value; and an output inverting step of inverting the output signal by generating an interrupt in the main step when a time indicated by the timer / counter value elapses. Characteristic pulse width modulation control method by a microcontroller. 2. The pulse according to claim 1, wherein the sum of the first control variable and the second control variable during each step repeated in the main step is constant. Width modulation control method.