JP2011022692A - Feedback control device and feedback control program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a feedback control device which can carry out feedback control, while being unaffected by noise due to on/off action of a switching element. <P>SOLUTION: The feedback control device includes a configuration (a delay circuit 16, and a 2-input NAND gate 13) for stopping the switching action of the switching element 14, when an analog signal from a sensor 21 is A/D-converted by an A/D converter 17 to obtain information necessary for determining the contents of control for a PWM-signal generating section 12. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The technology disclosed in the present specification relates to a feedback control device and a feedback control program for performing feedback control.

  As is well known, the amount of power supplied to a load (power supply target) is adjusted by turning on and off switching elements at high speed. In order to accurately adjust the power supply amount, it is necessary to measure a physical quantity (temperature, current value, etc.) that changes in accordance with the power supply amount and perform feedback control based on the measurement result. Therefore, a feedback control device having the configuration shown in FIG. 8 has been developed.

  This feedback control device is a device that feedback-controls the amount of power supplied to the heater 20 for heating the temperature control object based on the measurement result of the temperature sensor 21 by the temperature sensor 21.

More specifically, an AD (analog-to-digital) converter 57 provided in the feedback control device is instructed by the temperature control calculation unit 51 to receive an analog signal from the temperature sensor 21 that is input via the amplifier circuit 58. It is a circuit that converts it into digital data when The PWM signal generation unit 52 is a circuit that generates a PWM (Pulse Width Modulation) signal that changes with time in a pattern instructed by the temperature control calculation unit 51.

  The NOT circuit 59 is a circuit that supplies a signal obtained by inverting the PWM signal from the PWM signal generator 52 to the gate of the switching element 54. The smoothing circuit 55 is a circuit that generates a DC voltage of a level corresponding to the ON time of the switching element 14 and applies it to the heater 20 by smoothing the pulsed current from the switching element 54.

  The temperature control calculation unit 51 obtains a temperature control target temperature by causing the AD converter 57 to perform AD conversion, and based on the acquired temperature, sets a duty ratio that can set the temperature control target temperature as a target temperature. This is a unit that periodically performs the process of “determining and generating the PWM signal having the determined duty ratio in the PWM signal generation unit 52”.

JP 2006-145102 A

  As the frequency of the PWM signal is higher, the smoothing circuit 55 can be reduced in size. For this reason, the PWM signal generator 52 of the feedback control device described above generates a high-frequency PWM signal. However, when the switching element 54 is turned ON / OFF at high speed, a relatively large noise is generated. Will occur. The signal output from the temperature sensor 21 is a weak signal.

Further, it is practically impossible to provide a signal path from the temperature sensor 21 to the AD converter 57 at a location far away from the switching element 54. Therefore, in the conventional feedback control device (particularly, a device that is downsized), as shown in FIG. 9, when the switching element 54 is turned ON / OFF, noise is superimposed on the temperature sensor signal input to the AD converter 57. It has become something to end up. The conventional feedback control device is a device in which erroneous control may be performed on the PWM signal generator due to the influence of the noise.

  Therefore, an object of the disclosed technique is to provide a feedback control device and a feedback control program that can perform feedback control without being affected by noise caused by ON / OFF operation of a switching element.

  In order to solve the above-described problem, a feedback control device according to an aspect of the disclosed technology has a switching element for adjusting the amount of power supplied to a load and a value that changes according to the amount of power supplied to the load. An AD converter to which a measured value of an analog sensor of a specific physical quantity is input, and the switching element for making the physical quantity value coincide with a target value based on the measured physical quantity value converted into digital data by the AD converter A control unit that periodically performs a calculation process for calculating a target ratio that is a ratio of ON time of the switching element, and performs ON / OFF control of the switching element so that the ratio of the ON time becomes the calculated target ratio. The ON / OFF operation of the switching element is stopped at the time of AD conversion by the AD converter for each measured value used for calculating the ratio. And a that controller.

  According to the disclosed technology, it is possible to perform feedback control without being affected by noise caused by the ON / OFF operation of the switching element.

The block diagram of the feedback control apparatus which concerns on 1st Embodiment. The flowchart of the control process which the temperature control calculating part with which the feedback control apparatus which concerns on 1st Embodiment is provided performs. The timing chart for demonstrating operation | movement of the feedback control apparatus which concerns on 1st Embodiment. Explanatory drawing of the state of a temperature sensor signal in case the switching element is not performing ON / OFF operation. The block diagram of the feedback control apparatus which concerns on 2nd Embodiment. The block diagram of the feedback control apparatus which concerns on 3rd Embodiment. The flowchart of the control processing which the temperature control calculating part with which the feedback control apparatus which concerns on 3rd Embodiment is provided performs. The block diagram of the existing feedback control apparatus. Explanatory drawing of the state of the temperature sensor signal in the existing feedback control apparatus.

  Hereinafter, some embodiments of the feedback control device will be described with reference to the drawings. Each embodiment described below is an exemplification, and the present invention is not limited to a specific technical matter in the following description.

<< First Embodiment >>
FIG. 1 shows the configuration of the feedback control apparatus according to the first embodiment.
This feedback control device feedback-controls the amount of power supplied to a heater 20 for heating a certain object (hereinafter referred to as a temperature control target) based on the temperature measurement result of the temperature control target by the temperature sensor 21. Device.

As illustrated, the feedback control device includes a temperature control calculation unit 11, a PWM signal generation unit 12, a two-input NAND gate 13, a switching element 14, a smoothing circuit 15, a delay circuit 16, an AD converter 17, and an amplification circuit 18. Is provided.

  The amplifier circuit 18 is a circuit for amplifying an analog signal from the temperature sensor 21. The AD converter 17 is a circuit for converting an analog signal (hereinafter referred to as a temperature sensor signal) from the amplifier circuit 18 into digital data. The AD converter 17 is a circuit that starts AD conversion when the level of the AD conversion start signal from the temperature control calculation unit 11 changes to a high level.

The switching element 14 repeats an ON / OFF operation according to a gate control signal input to the gate, thereby converting a direct current of the voltage Vcc into a pulsed current and supplying the pulsed current to the smoothing circuit 15 (in this embodiment, This is a p-type MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). The smoothing circuit 15 is a circuit that generates a DC voltage of a level corresponding to the ON time of the switching element 14 by smoothing the pulsed current from the switching element 14 and applies it to the heater 20.

  The PWM signal generation unit 12 is a circuit that generates a PWM signal that changes with time in a pattern (PWM period, duty ratio) instructed by the temperature control calculation unit 11.

  The delay circuit 16 normally outputs a high-level stop control signal, and outputs a low-level stop control signal only for a certain period of time when the AD conversion start signal changes to a high level (so-called one-shot). Shot multivibrator). The delay circuit 16 is configured to output a low-level stop control signal for a time comparable to the AD conversion time (for example, 5 μs) of the AD converter 17 (in this embodiment, the same time as the AD conversion time). It has become a circuit. The AD conversion time of the AD converter 17 is a time required for AD conversion by the AD converter 17.

  The 2-input NAND gate 13 outputs a low level signal from the output terminal when a high level signal is input to both of the two input terminals, and otherwise outputs a high level signal from the output terminal. It is a circuit that outputs a signal. A stop control signal from the delay circuit 16 and a PWM signal from the PWM signal generator 12 are input to the two input terminals of the 2-input NAND gate 13, respectively. The feedback control device is a device in which a signal from the output terminal of the two-input NAND gate 13 is input to the gate of the switching element 14 as a gate control signal.

  The temperature control calculation unit 11 is a unit (a kind of computer) that executes the control process of the procedure shown in FIG. 2 according to the feedback control program set in the own unit when the feedback control device is activated.

  That is, when the feedback control device is activated, the temperature control calculation unit 11 first performs an initialization process (step S101). At the time of this initialization process, a process for initializing values of various variables used thereafter, a process for setting the PWM cycle of the PWM signal to be generated in the PWM signal generation unit 12, and the like are performed.

  Thereafter, the temperature control calculation unit 11 waits for a sampling period (for example, 5 ms) to elapse (step S102). Although not described in detail, the feedback control program set in the temperature control calculation unit 11 is a program that causes the feedback control device to function as a device that allows the user to set the target temperature.

When the sampling period has elapsed (step S102; YES), the temperature control calculation unit 11
Asserts the AD conversion start signal (that is, changes the level of the AD conversion start signal to high level) to instruct the AD converter 17 to start AD conversion (step S103).

  Thereafter, the temperature control calculation unit 11 waits for the AD conversion of the temperature sensor signal by the AD converter 17 to be completed (step S104). Then, when the AD conversion is completed (step S104: YES), the temperature control calculation unit 11 performs a target duty ratio calculation process (step S105). This target duty ratio calculation process is a process for calculating a target duty ratio that is a ratio of the ON time of the switching element 14 for matching the temperature of the temperature control target to the target temperature based on the current AD conversion result of the temperature sensor signal. It is.

Here, “the ratio of the ON time of the switching element 14 for making the temperature of the temperature control target coincide with the target temperature” (target duty ratio) is the value of the ratio of the ON time of the switching element 14, It is a value that can bring the temperature of the temperature control target closer to the target temperature, or can maintain the temperature of the temperature control target at a temperature near the target temperature. The target duty ratio calculation process that is actually executed by the temperature control calculation unit 11 according to the present embodiment is a process of calculating the target duty ratio by a so-called PID (proportional integral and differential gain) control algorithm.

  After completing the target duty ratio calculation process, the temperature control calculation unit 11 controls the PWM signal generation unit 12 to generate a PWM signal whose duty ratio is the target duty ratio (step S106). And the temperature control calculating part 11 starts the process after step S102 again.

  As is clear from the above description, the feedback control device according to the present embodiment has a configuration in which the ON / OFF operation of the switching element 14 is stopped during AD conversion for obtaining information necessary for updating / calculating the target duty ratio. have.

  More specifically, as already described, when the AD conversion start signal is asserted, the delay circuit 16 (see FIG. 1) sets the level of the stop control signal to a time comparable to the AD conversion time (hereinafter, It is a circuit that changes to a low level only during a period of time). The feedback control device has a configuration in which the stop control signal is input to one input terminal of the 2-input NAND gate 13 and the output signal of the 2-input NAND gate 13 is input to the gate of the switching element 14 as a gate control signal. is doing.

  Therefore, when the AD conversion start signal is asserted by the temperature control calculation unit 11, the level of the gate control signal is fixed at a high level thereafter until the stop time elapses, as schematically shown in FIG. Will be.

  Further, when the AD conversion start signal is asserted, AD conversion of the temperature sensor signal by the AD converter 17 is started, but the stop time is a time corresponding to the AD conversion time of the AD converter 17. Therefore, the AD conversion by the AD converter 17 is executed under the condition where the level of the gate control signal is fixed to the high level, that is, the situation where the switching element 14 which is a pMOSFET continues to be in the OFF state. become.

  When the switching element 14 is not performing the ON / OFF operation, as shown in FIG. 4, noise (see FIG. 9) due to the ON / OFF operation of the switching element 14 is superimposed on the temperature sensor signal. It will not be.

Therefore, if the feedback control apparatus according to the present embodiment is used, the temperature of the temperature control target can be controlled without being affected by noise caused by the ON / OFF operation of the switching element 14.

Even when the operation of the switching element 14 is stopped during AD conversion, there is no particular problem in controlling the temperature of the temperature control target. This is because the sampling period is a parameter whose appropriate value is determined by the allowable temperature error and the specifications / characteristics of the temperature control target, but the output resolution is 2%.
In other words, the PWM signal generation circuit of 50 steps from the output 0 to the maximum output can be accurately controlled. In the present invention, the switching element is stopped. However, if the sampling (AD conversion) cycle is 5 ms and the AD conversion time is 5 μs, the amount of electric power supplied to the heater 17 generated by stopping the operation of the switching element 14 during AD conversion. This is because the amount of change is 0.1% at most even when the sampling period is 1000 times the AD conversion time (that is, when the amount of change is relatively large).

<< Second Embodiment >>
Hereinafter, the configuration and operation of the feedback control device according to the second embodiment will be described with a focus on differences from the feedback control device according to the first embodiment.

  As shown in FIG. 5, the feedback control apparatus according to the second embodiment includes a temperature control calculation unit 11, a PWM signal generation unit 12b, a switching element 14, a smoothing circuit 15, a delay circuit 16, an AD converter 17, and an amplification circuit. 18 and NOT gate 19 are provided.

  The temperature control calculation unit 11, the switching element 14, the smoothing circuit 15, the delay circuit 16, the AD converter 17, and the amplifier circuit 18 that are included in the feedback control device are respectively configured with the same names that are included in the feedback control device according to the first embodiment. Same as element.

  The NOT gate 19 is a circuit that supplies a signal obtained by inverting the signal from the PWM signal generator 12b to the gate of the switching element 14 as a gate control signal.

  The PWM signal generator 12b is a circuit having essentially the same function as the PWM signal generator 12 described above. However, when a low level signal is input to a certain signal input terminal, the PWM signal generation unit 12b stops outputting the PWM signal and outputs a signal of a certain level (low level in this embodiment). It is a circuit that outputs.

  The feedback control device according to the second embodiment is configured such that the stop control signal from the delay circuit 16 is input to the signal input terminal of the PWM signal generation unit 12b.

  As is clear from the above description, the feedback control device according to the second embodiment is different from the feedback control device according to the first embodiment in that the ON / OFF operation of the switching element 14 is stopped during AD conversion. It is a device realized by.

  Therefore, even with the feedback control device according to the second embodiment, the temperature of the temperature control target can be controlled without being affected by noise caused by the ON / OFF operation of the switching element 14.

<< Third Embodiment >>
Hereinafter, the configuration and operation of the feedback control device according to the third embodiment will be described with a focus on differences from the feedback control device according to the first and second embodiments.

FIG. 6 shows the configuration of the feedback control apparatus according to the third embodiment.
As illustrated, the feedback control apparatus according to the third embodiment includes a temperature control calculation unit 11c, a PWM signal generation unit 12, a switching element 14, a smoothing circuit 15, a delay circuit 16, an AD converter 17, and an amplification circuit 18. And a NOT gate 19.

  The PWM signal generation unit 12, the switching element 14, the smoothing circuit 15, the AD converter 17, and the amplifier circuit 18 included in the feedback control device are the same as the components of the same name provided in the feedback control device according to the first embodiment. It is. The NOT gate 19 is the same logic gate as the NOT gate 19 provided in the feedback control device according to the second embodiment.

  Similar to the temperature control calculation unit 11, the temperature control calculation unit 11 c is a unit that starts an operation according to the feedback control program set in the own unit when the feedback control device is activated. However, the feedback control program set in the temperature control calculation unit 11c causes the temperature control calculation unit 11c to execute the control processing of the procedure / contents shown in FIG.

  That is, when the feedback control device is activated, the temperature control calculation unit 11c first performs an initialization process (step S201) having the same content as that performed by the temperature control calculation unit 11.

  Thereafter, the temperature control calculation unit 11c waits for a sampling period (for example, 5 ms) to elapse (step S202). When the sampling period has elapsed (step S202; YES), the temperature control calculation unit 11c stores the target duty ratio at that time (hereinafter referred to as the current target duty ratio) as the control restart duty ratio. The process (step S203) to perform is performed.

  Next, in step S204, the temperature control calculation unit 11c determines whether or not the current target duty ratio is 50% or more. Then, when the current target duty ratio is 50% or more, the temperature control calculation unit 11c controls the PWM signal generation unit 12 so as to generate a PWM signal having a duty ratio of 100%, and then step S204. Terminate the process. Further, when the current target duty ratio is less than 50%, the temperature control calculation unit 11c controls the PWM signal generation unit 12 so as to generate a PWM signal having a duty ratio of 0%, and then step S204. Terminate the process.

  After completing the process in step S204, the temperature control calculation unit 11c asserts an AD conversion start signal (step S205). Thereafter, the temperature control calculation unit 11c waits for the AD conversion of the temperature sensor signal by the AD converter 17 to be completed (step S206).

  When AD conversion is completed (step S206: YES), the temperature control calculation unit 11c controls the PWM signal generation unit 12 to generate a PWM signal having a duty ratio for control resumption (step S207).

  And the temperature control calculating part 11c starts the process after step S202, after performing the process of the same content as step S105 and S106 (refer FIG. 2) in step S208 and S209, respectively.

  As is clear from the above description, the feedback control device according to the third embodiment is also a device that stops the ON / OFF operation of the switching element 14 during AD conversion of the temperature sensor signal. Therefore, even with the feedback control apparatus according to the present embodiment, the temperature of the temperature control target can be controlled without being affected by noise caused by the ON / OFF operation of the switching element 14.

  Further, the feedback control device according to the third embodiment has a configuration in which the feedback control program (temperature control calculation unit 11c) stops the ON / OFF operation of the switching element 14. Therefore, this feedback control device is a device that can be manufactured more inexpensively and more compactly than the feedback control devices according to the first and second embodiments because the delay circuit 16 and the like are unnecessary.

  Furthermore, the feedback control apparatus according to the third embodiment uses the amount of power supplied to the heater 20 during AD conversion as the maximum power amount that can be supplied to the heater 20, “0”, before starting AD conversion. 20 has a function of controlling the amount of power closer to the amount of power supplied to 20. The feedback control device also has a function of starting the switching operation of the switching element 14 immediately after completion of AD conversion (without waiting for completion of calculation of the target duty ratio).

  Therefore, the feedback control device according to the third embodiment is a device that can control the temperature of the temperature control target more accurately than the feedback control devices according to the first and second embodiments that do not have such a function. It will also be.

<Deformation>
The feedback control device according to each embodiment described above can be variously modified. For example, the temperature control calculation unit 11 in the feedback control device according to the first and second embodiments can be transformed into a unit that also executes processing equivalent to the processing in steps S203 and S207 during the control processing.

  Further, as long as the feedback control device according to each embodiment does not cause a problem even if the switching operation of the switching element 14 is occasionally stopped, the amount of electric power supplied to other than the heater 20 (such as a Peltier element). It can also be used as a device for controlling. Further, the feedback control device according to each embodiment can be modified into a device in which the switching operation of the switching element 14 is stopped only when the AD converter 17 functions frequently and the AD conversion result is actually used. Furthermore, the feedback control device according to each embodiment is changed to a device that does not include the smoothing circuit 15 and the amplification circuit 18, a device that performs feedback control based on an analog signal from a sensor (for example, a current sensor) other than the temperature sensor 21, and the like. The things that can be transformed are just the same.

DESCRIPTION OF SYMBOLS 11, 11c Temperature control calculating part 12, 12b PWM signal generation part 13 2 input NAND gate 14 Switching element 15 Smoothing circuit 16 Delay circuit 17 AD converter 18 Amplifying circuit 19 NOT gate 20 Heater 21 Temperature sensor

Claims (6)

A switching element for adjusting the amount of power supplied to the load;
An AD converter to which a measured value by an analog sensor of a specific physical quantity whose value changes according to the amount of power supplied to the load; and
Based on the measured value of the physical quantity converted into digital data by the AD converter, a calculation process is periodically performed to calculate a target ratio that is a ratio of the ON time of the switching element for making the physical quantity value coincide with the target value. And a control unit for controlling the ON / OFF of the switching element so that the ratio of the ON time is equal to the calculated target ratio, and when the AD conversion is performed by the AD converter for each measurement value used for calculating the target ratio. And a control section for stopping the ON / OFF operation of the switching element. The controller is
In the case where the switching element is controlled so that the OFF time is less than the ON time, when performing the arithmetic processing, the switching element is controlled to be in the ON state, and then the ON / OFF operation of the switching element is performed. In the situation where the switching element is controlled such that the ON time is less than the OFF time, the calculation process is performed after the switching element is controlled to be in the OFF state. The feedback control apparatus according to claim 1, wherein the ON / OFF operation is stopped. The control unit is
A PWM signal generator for generating a PWM signal;
The AD converter periodically starts an AD conversion operation by asserting an AD conversion start signal to the AD converter, and the arithmetic processing is performed based on each measured value of the physical quantity converted into digital data by the AD conversion operation. An arithmetic processing unit that instructs the PWM signal generation unit to generate a PWM signal having a duty ratio according to the calculated target ratio each time the arithmetic processing is performed;
A signal supply circuit that supplies the PWM signal from the PWM signal generation unit to the gate of the switching element as a gate control signal, and has a predetermined level for a predetermined time after the AD conversion start signal is asserted. The feedback control apparatus according to claim 1, further comprising: a signal supply circuit that supplies a gate control signal to a gate of the switching element. The control unit is
The AD converter periodically starts an AD conversion operation by asserting an AD conversion start signal to the AD converter, and the arithmetic processing is performed based on each measured value of the physical quantity converted into digital data by the AD conversion operation. An arithmetic processing unit to perform,
A PWM signal generation unit that generates a PWM signal having a duty ratio corresponding to a target ratio calculated by the arithmetic processing unit and supplies the PWM signal as a gate control signal to the gate of the switching element, and the AD conversion start signal is asserted 2. The feedback control apparatus according to claim 1, further comprising: a PWM signal generation unit that generates a signal of a predetermined level for a predetermined time. The control unit is
A PWM signal generator for generating a PWM signal and supplying it as a gate control signal to the gate of the switching element;
The process of starting the AD conversion operation of the AD converter after stopping the operation of the PWM signal generation unit is periodically performed, and based on each measured value of the physical quantity converted into digital data by the started AD conversion operation An arithmetic processing unit that performs arithmetic processing and instructs the PWM signal generating unit to start generating a PWM signal having a duty ratio corresponding to the calculated target ratio each time the arithmetic processing is performed. The feedback control device according to claim 1 or 2. A switching element for adjusting the amount of power supplied to the load, an AD converter to which a measured value by an analog sensor of a specific physical quantity whose value changes according to the amount of power supplied to the load, and a PWM signal To a computer connected to a PWM signal generating unit for generating and supplying a gate control signal to the gate of the switching element,
Stopping the operation of the PWM signal generation unit and then starting the AD conversion operation of the AD converter;
Calculating a target ratio that is a ratio of the ON time of the switching element for making the physical quantity value coincide with the target value based on the measured value of the physical quantity converted into digital data by the started AD conversion operation;
Instructing the PWM signal generation unit to start generating a PWM signal having a duty ratio corresponding to the calculated target ratio.

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