JPS61123999A - A/d converter - 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] [Technical Field] The present invention relates to an analog/digital (A/D) conversion device,
In particular, it relates to an A/D conversion device with intelligent functions.

[Prior Art] With the development of microcomputers in recent years, many industrial devices and household devices have come to be digitally controlled. The control targets of industrial equipment and household equipment are often analog quantities (e.g. temperature, voltage), and A/D converters and D/A converters are becoming increasingly important as their interfaces. Ta.

For example, as a digitally controlled device, the configuration of a conventional copying machine is shown in FIG. 1. In FIG. 1, 1 is a microcomputer, 2 is a switching regulator, 3 is a halogen lamp lighting circuit, 4 is a motor drive circuit, 5 is a high voltage circuit, 8 is a fixing device halogen lamp control circuit, 7 is a display circuit, 8 is an operation input circuit, and 3 is a sensor. Here, the microcomputer 1 performs, for example, sequence control to turn on and off a halogen lamp, etc., temperature control 1 display and operation control of the fixing device, etc., in accordance with the copy processing process.On the other hand, such an external unit performs analog control itself. Attempts have been made to reduce equipment costs and improve reliability by adding analog control functions for these external units to microcomviators, which used to only instruct them to turn them on and off. ing.

For example, regarding the control of a motor (CDC motor).

A PLL IC was used for the control, but the output pulses of the encoder connected to the DC motor were directly input into the microcomputer, and the microcomputer calculated the appropriate control PWM value from the speed information.
A speed control signal is output from the output port to the motor drive circuit 4 to drive the motor. Furthermore, the voltage control section of the switching regulator 2, which used to generate a constant voltage, for example 24V DC, when the AC power is turned on, completely independent of the operation of the copying machine, uses an A/D conversion element to convert the output voltage to the microcomputer. Incorporate into
Therefore, the voltage value is calculated and high-speed PWM (e.g. 24kHz
z 8-bit PWM) control signal is created and fed back to the switching regulator 2. Furthermore, in the halogen lamp control circuit that keeps the effective value of the voltage applied to the halogen lamp constant, and in the high voltage circuit that charges the photosensitive drum of a copying machine by corona discharge, temperature control of the halogen lamp for the fuser is performed. A microcomputer can be used to control the circuit for use in the same way.

By doing so, the number of external control parts can be reduced and costs can be reduced.

However, by performing the above-mentioned control with a microcomputer, the amount of programs becomes abnormally large, the number of tasks increases, and the processing speed of the microcomputer itself becomes abnormally slow.

[Objective] An object of the present invention is to provide an A/D conversion device that can solve the above-mentioned problems and improve control efficiency by a microcomputer.

[Embodiment] FIG. 2 is a block diagram showing an embodiment of an A/D conversion device according to the present invention. ! In Figure 2, 10 is an 8-bit microcomputer, 11 is an 8-bit A/D converter, 12 is an area judger, and 13 is a control signal of the A/D converter 11 (for example, C
8 (chip selector), WR (A/D conversion star h)
, RD (output latch), etc.), 14 is a microcomputer 10. 8-bit data transmission path between the A/D converter 11 and the area determiner 12; 15 is a signal determined by the area determiner 12 (for example, a signal indicating that the area is above the set area; a signal indicating that the area is within the set area; 1B is a control signal for the area determiner 12 from the microcomputer 10 (for example, a latch signal for an area setting value, an interrupt request signal to the microcomputer 10, etc.), 17 is an A/D converter 11 This is an A/D conversion completion signal output from the area determination unit 12 to the area determination unit 12. V represents the analog input voltage to the A/D converter 11. Although not shown, the microcomputer IO outputs a signal for controlling the controlled object.

In such a configuration, the microcomputer l
O initializes the upper limit value and lower limit value of the region in the region determiner 12 via the transmission line 14. Then, when you want to know the control amount of the controlled object, the microcomputer 10 uses A/+1
A request is made to the converter 11 to start A/D conversion. Based on this
In response to the A/D conversion end signal 17 from the A/D converter 11, the area determiner 12 latches the A/D converted digital value and determines the upper and lower limits of the area set in the area determiner 12. The magnitude relationship between the value and the digital value is checked to determine whether the control amount input to the A/D converter 11 is above the set range, within the set range, or below the set range. , and inputs a signal 15 indicating the result to the microcomputer IO. At this time, if the control amount input to the A/D converter 11 by the input of the signal 15 is above or below the set range, an interrupt is requested to the microcomputer IO. Also, the A/D converter 11
If the control amount input to is within the setting range,
-f An interrupt request is not generated to the microcomputer 10. Therefore, as long as the control amount input to the A/D converter 11 is within the initial setting range as described above, the A/D conversion is not performed. Even if this is performed frequently, no load is placed on the CPU in the microcomputer 10, and when the control amount input to the A/D converter 11 is outside the set range, the area determiner 12 microcomputer lO
request an interrupt. , In the interrupt routine based on the interrupt request from the area determiner 12, the microcomputer 10
The data obtained by A/D conversion by the D converter 11 is directly read and calculated to control the controlled object so that the control amount falls within the set range again. In addition to such control, the microcomputer 10 adds a predetermined correction amount to the manipulated variable of the controlled object based on a signal 15 from the region determiner 12 indicating that the region is above the region, within the region, or below the region. Feedback can also be applied to the controlled object so that the control amount input to the A/D converter 11 falls within the set range again.

FIG. 3 shows a more specific circuit of the AID conversion device according to the present invention. In FIG. 3, 101 is an 8-bit microcomputer, 102 is an 8-bit A/D conversion element,
103, 104, 107 are parallel latch elements, 1
05, foe is a digital comparator.

Microcomputer 101 port) Pl, 0°Pl,
1. Pl,2 outputs a signal for controlling the A/D conversion element 102 to the A/D conversion element 102. Port P1.3,
Pl,4 outputs a latch enable signal for the parallel latch elements 104 and 107 to the same latch elements 104 and 107. Port P1.5 is a signal indicating that the control amount input to the A/D conversion element 102 is "above the set range, baud" Pl
, [l is a signal indicating that the controlled variable is less than or equal to the set range, and port P1.7 is a signal indicating that the controlled variable is within the set range from digital comparators 105 and 108 as region determiners, respectively. input. Note that this is not necessarily the case.
There is no need for three people at ports P1.5 to P1.7, and as long as there is no interrupt request, the control amount input to the A/D conversion element 102 is within the specified range, so one interrupt request is required. If so, port pt, s or P
By inputting a signal to either one of 1 and 8, it is confirmed whether the control amount is above or below the set range. Therefore, in reality, it is only necessary to determine during the interrupt routine whether or not a signal indicating a value greater than or equal to the set range has been input at port P1.5.
Although only one analog input system for Q2 is shown in the figure, this can be done by several people, but in that case, a signal for instructing the multiplexer and as many area determiners as the number of inputs are required.

FIG. 4 is a block diagram showing another embodiment of the A/D conversion device according to the present invention. This A/D converter can be configured as a one-chip microcomputer on the same chip as the CPU. In FIG. 4, 18 is an 8-bit CPU, 19 and 20 are 8-bit registers that store the upper and lower limit values of the area, and 21 is an 8-bit A/C that converts the analog input voltage value V into a digital value. A D converter, 22 is an 8-bit holding register that stores 8-bit digital data, and 23 is a comparator that compares the output value from registers 19 and 20 with the output value from register 22. 24 is RAM, 25
is a ROM.

In such a configuration, first, by CPU ts,
The upper and lower limit values of the area are initially set in the registers 19 and 22, and in the ROM 25, the CPU to commands the A/D converter 21 to start A/port conversion at certain time intervals. Program it to A/
When the D conversion starts, the A/D converter 21 starts A/D conversion of the analog input voltage from the controlled object.
During this time, CPo 18 is performing other tasks.

Then, when the A/D conversion is completed, the digital value obtained by the A/D conversion is stored in the holding register 22, and the digital value (measured value) stored in the register 22 is combined with the digital value (measured value) in the register 19.20 by the comparator 23. The CPU 1B compares the upper and lower limits of the set range, and if the measured value is within the set range, the CPU 1B continues with other tasks. If the measured value is outside the set range, the comparator 23 outputs an interrupt signal int to the CPo 18, and the CP018 performs feedback control of the controlled object so that the controlled amount of the controlled object returns to within the set range. do. An example of such an interrupt routine is shown in FIG. 5, and this control procedure is set in the ROM 25. As shown in FIG. 5, in step S1, a memory ADMODE indicating which input is being A/D converted among a plurality of inputs such as a temperature sensor of a fixing device, a switching regulator, etc. is read out.Next, in step S2, The address indicating the memory area where the PIIN correction table of the corresponding control target is stored is stored in the data pointer (DPTR).Next, step s3
In step s4, the central setting value of control regarding the corresponding control object is stored in the memory VREG.Then, in step s4, the AI-converted digital value from the holding register 22 is transferred to the 7 cumulator.Next, in step S5, Based on the magnitude information flag POF from the comparator 23, it is determined whether the digital value in the accumulator is above or below the set range, and if it is above or below the set range, the process proceeds to step S8, and if it is below the set range, the process proceeds to step S7. Then, the process proceeds to step S8, where the difference between the A/D-converted digital value and the center setting value is calculated ≧V. Then, the process proceeds to step S8, where ≧V is broadly categorized into n pieces. If ±3 from then ≧V
3-8 is Ao, 8-1G is A, 18-32 is A
2.32 to 69 are classified as A3...An-1. Accordingly, in step S8, the set data pointer and the offset value (A
If 2, use 2) to obtain the corrected PWM value ≧ PWM0
Next, in step SIQ, it is determined whether the digital value from the accumulator is above or below the set range using the magnitude information flag POF, and if it is above the set range, the PH set value is set in step Sll so that ≧PWM is subtracted from the PWM set price. If it is below the setting range, the PWM setting value is corrected in step S12 so that Pw is added to the setting value ≧PWM.

FIG. 8 shows an example of the configuration of a copying machine incorporating a microcomputer with a built-in A/D conversion device according to the present invention. In FIG.
/D converter (the analog input device is A/D 1 to A
An 8-bit microcomputer with a built-in
It is a switching regulator that is switched by the output from O1 to Pw, and its output is fed back through the port A/Di of the microcomputer 200. 202 is a high voltage generation circuit that generates a high voltage corresponding to the PWM output from port PO2 of the microcomputer 200, and its output is output from the port PO2 of the A/D.
Feedback is provided through 2. 203 is a developing bias generation circuit which generates an AC component according to the outputs from PO3 and PO4 of the microcomputer 200;
Generate each DC component and convert the output to baud) A/D3
Give feedback through. 213 is a DC motor, 2
14 is an encoder that rotates in synchronization with the DC motor 213 and generates pulses; 204 is a microcomputer 2;
DC motor 21 according to the output from port PO5 of
This is a motor driver that controls 3. encoder 214
The output is input to the microcomputer 200. 2
06 is a plunger or solenoid, and 205 is a driver for the plunger or solenoid 206, which controls the plunger or solenoid 206 in accordance with the output from the microcomputer 200. 218, 217 are halogen lamps for exposure and fixing; 215 is a temperature sensor provided near the lamps 218, 217; 207 is a halogen lamp 218, which responds to the pulse output from ports PO8, PO7 of the micro core computer 200; This is a halogen lamp lighting circuit that controls the amount of power supplied to the 217.

The halogen lamps 218 and 217 send measured values (analog values) from the temperature sensor 215 to the microcomputer 200.
Feedback control is performed by inputting to port A/D 4 of . Reference numeral 208 denotes a scanning section and a display section of the copying machine, which are feedback-controlled by the microcomputer 200. 208 is a sensor such as a microswitch, and the sensor output is sent to the microcomputer 2.
00 is input.

The microcomputer 200 configured as described above has a scan mode in which ports A/D 1 to A/D 4 are sequentially converted into AI ports, and a scan mode in which ports A/D input numbers are specified on the sequence program. For example, if scan mode is used, the four analog inputs from A101 to A/D4 are 2001L.
A/D conversion is performed once every sec (A10 conversion time is 504 sec). As a result, A/D conversion starts automatically and continuously, so the microcomputer 200 The burden of control by the CPU is reduced only when the copying machine is started up and when the controlled variable of the controlled object deviates from the set range, making the burden extremely light.

Furthermore, even at startup when a controlled object is turned on and guided to a certain control 1, the upper limit value of the area is set to 1/2 of the set value. If the lower limit value is set to 0, the control amount will be 1 of the set value.
/2, there is little need to perform A/D conversion for the controlled object, and in the interrupt routine when the control amount becomes 1/2 or more of the set value, for example, the upper limit of the area is set to the set value. 3/4. The lower limit value is reset to the set value of 172, and the control operation amount is also changed at the same time. By performing such steps several times, the control amount is guided within the set range, and the upper and lower limits of the range are brought within the final set range. By changing the upper and lower limit values of the area in this way, the load on the CPU of the microcomputer can be reduced even when starting up the controlled object.

[Effects] As described above, according to the present invention, it is possible to determine whether an A/D converted value is within a predetermined range. As a result, when a microcomputer handles many control objects, for example, by applying the A/D conversion device of the present invention, the microcomputer does not need to read and calculate all A/D converted values, and It is now necessary to correct the manipulated variable only when the /D-converted value is outside the predetermined range, making it possible to correct the CPU when the controlled variable is outside the predetermined range due to disturbance, etc., and the conventional sequence. The A/D conversion device of the present invention can be used exclusively for control, making it extremely effective to use. Depending on how the predetermined area is allocated, the A/D conversion device of the present invention can also be used as a comparator, such as when starting up a controlled object. can be effective.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a conventional copying machine, FIG. 2 is a block diagram showing an embodiment of an A/D conversion device according to the present invention, and FIG. 3 is a specific example of an AID conversion device according to the present invention. A diagram showing a circuit. FIG. 4 is a block diagram showing another embodiment of the A/D conversion device according to the present invention, FIG. 5 is a diagram showing an interrupt routine, and FIG. 6 is a copying machine to which the AI conversion device according to the present invention is applied. FIG. 18...Register for setting the upper limit value of the area. 20...Register for setting the lower limit value of the area, 21...
- A/D converter, 22... A register that stores the A/port converted value, 23... Comparator. Figure 1 Figure 2 Figure 5

Claims (1)

[Claims] 1) Two setting registers for setting two different setting values; a storage register for storing A/D converted measurement values; and settings from the two setting registers. An A/D conversion device comprising: a comparator that compares a value with an A/D converted measurement value from the storage register. 2) In the A/D conversion device according to claim 1, the comparator determines whether the A/D converted measured value is within the range of the two setting values and whether the two setting values are within the range of the two setting values. An A/D conversion device characterized by having a function of determining whether a value is larger or smaller than a value. 3) In the A/D conversion device according to claim 2, when the A/D converted measured value is larger or smaller than the range of the two setting values, the comparator detects whether the measured value is larger or smaller than the range of the two setting values. 1. An A/D conversion device characterized by having a function of outputting information indicating that the value is small or small and an interrupt signal to a microcomputer.