JPH01110088A - Driving current control system - Google Patents

Abstract

PURPOSE:To reduce power loss, by constituting a drive circuit with a mode switching element for carrying out ON/OFF control of driving current and a current level switching element for performing ON/OFF control of driving current level. CONSTITUTION:Outputs D0, D3 of a read only memory ROM100 are brought to H during forward driving. Consequently, switching elements S0, S3 are turned ON to supply current O01 to a motor 36. Combination of time length for ON and OFF times of the output D0 is controlled at this time so as to control current level. Outputs D1, D2 of ROM100 are brought to H during reverse driving. Consequently, switching elements S1, S2 are turned ON to supply current I02. Combination of time length for ON and OFF times is controlled at this time so as to control current level.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the control of the rotational speed, nine rotational directions, and torque of a DC motor, and to a drive current control system for actuators, coils, etc., and particularly relates to a method for controlling the drive current by digital switching. The present invention relates to a drive current control method that is controlled by.

[Prior Art] Hereinafter, the conventional technology for driving a DC motor, which is a typical application target of the present invention, will be described.

Conventionally, as a method for controlling a motor using a drive current controlled by digital switching, a step motor drive method as disclosed in, for example, Japanese Unexamined Patent Publication No. 61-46198 has been known.

As shown in FIG. 2, the drive system is one in which step motor electronic switches 3A, 3B, 3G, and 8D are used to drive the motor in a pulsative manner. Drive current I, 1e, ■. ,■. The power supply 10 is supplied by opening and closing the switch element, and the opening and closing is performed by manually addressing the memory element 4 A3 . by the output of the first address counter. This is performed by a phase switching signal given by AoA, and an average current switching signal given by the address inputs AO, AI, and All of the storage element by the output of the second address counter. Furthermore, the memory element 4 is connected to data output terminals Do, Dt* Di, D
a, each switch element is SA and SB, respectively.

Controlled by signals SC and SD, a wire current is obtained by combining the phase switching signal and the average current (drive current) switching signal, which changes the rotational speed and torque.

The rotation direction etc. are controlled.

FIGS. 3(a), 3(b), and 3(Q) are schematic diagrams showing typical configurations of conventional DC motor control circuits. Figure 3(a)
is a general schematic diagram, 31 is a control circuit that controls a DC current generator, 32 is an inductance of a controlled coil such as an armature, a field, or a combination of both in series, and 33 is an internal resistance of this coil. . FIG. 3(b) shows a case where the control circuit 31 is realized by a power source 310 and a variable resistor 311.

The inductance portion 32 and internal resistance 33 of the coil are collectively shown as a coil 36. FIG. 3(Q) shows a case where the control circuit 31 is realized by a power source 310 and a transistor 312. The drive current of the coil 36 is controlled by the input current of the transistor, and is controlled by the variable resistor 314.

Next, FIG. 4 shows an example of a control method conventionally applied to control a servo motor applied to numerical control and the like. Numerical control information shown as a digital signal SD in the figure is input from an input terminal 41 and converted into analog information Vc by a digital-to-analog converter . This analog information is compared by the comparator's differential amplifier 44 with the reference voltage Vs applied to the input terminal 43, resulting in an output current I on the coil 36 that is proportional to the difference.

Therefore, the current value is the input digital signal SD and the reference voltage V.
It is finely controlled by s.

Figure 5 shows an example of a chopper control type drive circuit that is conventionally applied to numerical control, etc., and shows digital numerical information S.
o is input from 51 and converted to an analog signal Vc at 52. This Vc is compared with a sawtooth wave Vs, which is a comparison wave, at a comparator 54, and is obtained on an output line 55 as a pulse width modulated output Vp. As shown in the figure, vp is given as the pulse width of the signal period in which Vc is lower than Vs.

The chopper 56 is operated by the output Vp, and the current Ic chopped from the DC power supply 57 is passed through the load coil 32. The diode 58 absorbs the back electromotive force generated by the inductance 32, and is a so-called return diode ( or flywheel diode).

Typical conventional techniques for DC motor control using digital switching control have been illustrated above, but all of these conventional techniques have many problems in terms of efficiency and handling, as described below.

[Problem that the invention seeks to solve]

First of all, the step motor drive method shown in Figure 2 is a drive method that intermittently provides a rotation angle determined by pulses specific to the step motor, and is applicable to a special target, and is intended for driving small and precise step motors. It is. In addition, since the step motor which is the load is unidirectional and cannot be driven in two directions, there is a problem that the utilization rate and drive efficiency of the coil are low.

Next, the drive method shown in FIGS. 3(b) and 3(c) controls the current and power by changing the amount of power consumption by the variable resistor 311 or the transistor 312, and the power loss is large. .

Another problem is that this circuit does not allow current to flow in both directions through the coil 36.

Next, in the case of the drive method shown in FIG. 4, the function of the amplifier unit 44 is to control how much power from the power supplies 320 and 321 is consumed by itself, leaving an amount to be consumed by the coils, so it is inefficient and generates less heat. Problems are unavoidable, and the amplifier inputs are analog values for both Vc and Vs, and if the stability of these signals and the stability of the amplification rate are not satisfied, accurate control is difficult. Various ideas have been made to solve this problem. For this reason, open-loop control is often insufficient due to the required precision, and closed-loop control is often used, which poses a problem that cannot be easily and economically realized. In addition, there is a Ward Leonard method which is similar to this method and has been used in the past in order to increase the power consumption (1), but the device is large-scale and inefficient, so it has not been used much recently.

In the case of the chopper control method shown in FIG. 5, since analog conversion is performed by the D/A 52 and modulation is performed by comparing analog values, precision and adjustment techniques are required, and many accessory parts are also required. Furthermore, bidirectional driving is not possible with this method, and in order to perform bidirectional driving using this method, a complex circuit configuration in which a plurality of chipper circuits of this type are combined is required.

Therefore, the purpose of the present invention is to solve these problems of the conventional technology, and to provide a digital control drive current control method that has low power loss, can perform bidirectional drive even with a single power supply, and can perform highly accurate control even with open-loop control. It is about providing.

Means for Solving Problem C] In order to achieve the above object, the present invention provides a mode changeover switching element that controls on/off the drive current of a load that has a smoothing effect, and a mode switching element that controls the current value of the drive current. a current value switching element for controlling the current value by turning on and off; a means for controlling the smoothed current value by controlling the current value switching element on and off at a predetermined cycle; The present invention is characterized by comprising means for controlling on/off of the mode switching switching element, and a structure configured to cause the smoothed current value to flow through the load in the direction given by the on/off of the mode switching switching element. .

[Function] As described above, the current control according to the present invention is freely performed by switching drive, so there is little power loss, the DC motor can be efficiently controlled, and bidirectional drive is possible with a single power source.

Furthermore, since analog signals are not used, no adjustment section is required.

Further, it is easy to control using a storage element such as a ROM, and in that case, fine control can be performed according to the number of input bits of the storage element. It has operational features such as easy synchronization with other controls. Furthermore, the present invention can be widely applied to control the drive current of inductive loads such as DC motors, actuators, and coils, and even if the target load is not inductive, the DC current can be controlled by connecting a smoothing circuit such as an inductance capacitor. It is possible to drive.

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which 100 is a read-only memory (ROM) that stores current switching control information, and switching elements 110, 11
1, 112, and 113.

Diodes 120, 121, 122, and 123 are return diodes for absorbing and protecting the back electromotive force for the switching element, and 36 is the coil of the DC motor that is the load, as shown in Figure 3 ( a).

This is the same as in the case of (b), (Q), FIGS. 4 and 5.

An input terminal 101 of the ROM 100 is an input terminal 10 to which a digital signal SDG for mode switching control that controls the direction of current and how the current flows through the switching element is input.
Reference numeral 2 denotes an input terminal for a clock pulse Pc having a speed sufficiently higher than the cycle of the mode switching, and the result of counting this by a counter 103 is input to the ROM 100.

Next, according to Table 1, the switching elements are When the switching control signal is 1'', it is in a conductive state, and when it is 0'', it is in a non-conductive state.

Therefore, the forward rotation direction is when the ROM outputs Do and Da are "1", that is, the switching elements 5o (110) and 53 (113) are in the conductive (on) state, and the reverse direction is when the ROM outputs DA and Da are "1", that is, the switching elements 5o (110) and 53 (113) are in the conductive (on) state. 81 (111) and Ss
(112) is in the on state. That is, during normal rotation, the current Io1 flows from the power supply 130 to the switching element S3.
through the coil 36, and the switching element 5o (1
10), and when reversed, IO2 flows into the power supply 130-
8l-coil 36-32-earth, flows like this.

Here, the outputs D2 and Dl are the upper address A of the ROM input,
,A, ,A, is the output for mode switching determined by ,D, and Dl are the upper addresses of the ROM input, A, ,A
, , is determined by A. This lower address is used to determine the output duty ratio by a combination of the lengths of the on state and off state of the switching elements S, , S, and to determine the DC current value by averaging this. In Figure 1 and Table 1, the lower address is A,...
Ayu, A.

Since the current value is 3 bits, it is possible to set the current value up to 8 levels. Also, the upper addresses are A, , A4. A.

Since there are 3 bits, 8 types of modes are possible.

Table 1 shows what current direction and average current value each of these eight modes has. In table 0, modes O to 2 have control data, =1. D,=
This is the case where ID,=O,D,=0, and a normal rotation direction current, that is, IOI flows. In mode 3, when the current value is zero, in modes 4 to 7, the control data is equal to 1. D, ==1. D
, =D, =O as shown in Table 1, and a reverse direction current I02 flows. Lower address Az
, At, and Ao, when mode 0 is OOO to 010 cycles, the switching element Doll is used, and for the other 5 cycles from 011 to 111, Do=O, so the period in which IOI actually starts flowing is one of the 8 cycles. 3
The duty ratio is 3/8. Since the current value 01 becomes a direct current obtained by averaging the pulses due to the smoothing effect of the coil 36, etc., the current value becomes a value proportional to 378. Based on the same principle, current values for each mode are given as shown.

As shown above, the present invention has an excellent feature of being able to drive the coils of a DC motor in both directions with a circuit having a relatively simple structure.8 When the present invention is applied to a DC motor, The operation is similar to that of the conventional system shown in FIGS. 2 to 5.

゛ Figure 1 shows the case where the current value is controlled by pulse width modulation (PWM), but based on the same principle, the pulse width of each of the eight cycles of the lower address is set to be narrower than the width of the cycle, and "1" is used. It is also possible to use pulse frequency modulation (PFM) by selecting the period at which `` occurs.

FIG. 6 shows an embodiment in which the present invention is applied to automatic door opening/closing control. A digital signal 80G is applied from an input terminal 601, converted for mode switching by ROM 600, and clocked for setting a current value. Pulse Pc is applied from input terminal 602 and counted by counter 603 to Ao.

The lower address signals of At and Ax are the same as in the case of FIG. Announcements are controlled by

The control of the door opening/closing motor 610 is the same as that shown in FIG.

Next, an example of door opening/closing and accompanying lighting and announcement operations will be explained with reference to FIG. 7 and Table 2. In Table 6, XX in the lower address indicates that any value may be used.
As a result of the digital control signal SoG being given by a computer or the like, each mode switching signal As, Aa, As is given as shown in FIG. The number of each mode is shown numerically above the upper address A3. The switching of each mode is determined by a computer sensing the movement of the door, etc. In this case, for simplicity, the lengths are the same except for the stationary period mode 4, which is particularly long. First, when the mode becomes number 1, the data Do, Dz, Da, Dam become 10 as shown in Table 2.
01, and number D, Da, and Do become 001. That is, as shown in FIG.

= 1, the door lighting 621 is turned on, the announcement circuit Da is activated by the switching signal 71, and announces the voice "Welcome" which has been stored in advance on the magnetic tape. At the same time, the DB switching signal 72 broadcasts "Please be careful where you step," and the door opening/closing motor 610
A forward current I01 of 1/8 unit is applied to the door, and the door begins to open gently. 04 in this case. When DB is "o, o", it says "Please watch your step" when it is "0.1", and "Please be careful where you step" when it is "1,0".
2 Table Slowly, J, "1.1" may be set in advance, such as silence.Furthermore, in modes 2 and 3, the data will be as shown in Table 2, and 37 as shown in Iol shown in Figure 7.
The number changes to 8 units, then 178 units, and the door opens. The period of mode 4 is a predetermined period considered to be required to enter the room through the door, and in modes 5 and 6.7 when all customers have entered the room or after the period set for entering the room, the motor drive current IO2 is flow and close the door as shown.

Towards the end of closing, the door illumination disappears as shown in 76 by switching from mode 6 to mode 7, and due to the switching signal 73 of data D8,
Announce ``please and slowly'' to the room. As described above, by using the ROM 600, the present invention allows the DC motor to be freely driven, and also allows easy synchronized operation in conjunction with other operations.

In the case of simple operation in the embodiment described above, the digital signal SDO can also be generated by a counter that counts the carry signal of the counter 603.

Although the example shows the drive method of a DC motor, it goes without saying that the drive current of an inductive load such as an actuator or coil can be controlled over a wide range with a similar configuration. It is also possible to drive with direct current by connecting a smoothing circuit such as an inductance capacitor.

〔Effect of the invention〕

As is clear from the above description, the present invention has the following effects.

(1) Current control is freely performed by switching drive, so there is little power loss and the DC motor can be controlled efficiently.

(2) Bidirectional drive possible with a single power supply (3) No analog signal is used and no adjustment section is required.

(4) Direct current bidirectional driving of inductive loads can be generally widely applied.

Furthermore, when controlling using a storage element such as a ROM, the following effects are obtained in addition to the above.

(5) Fine control can be performed according to the number of input bits of the memory element.

(6) Since all current control can be changed by simply changing the memory contents of the memory element, specifications and design changes are easy.

(7) Various control signals necessary for control can also be stored in the memory element and outputs can be obtained as before, so the number of control signals can be reduced.

[Brief explanation of the drawing]

Figure 1 is a wiring diagram showing the configuration of an embodiment of the present invention, Figure 2 is a wiring diagram showing a conventional step motor drive system, and Figures 3 to 5 are schematic wiring diagrams showing a conventional DC motor drive system. , FIG. 6 is a wiring diagram showing a modified embodiment of the present invention, and FIG. 7 is a time chart showing the operation of FIG. 6.

Claims (1)

[Claims] 1. A mode switching element for controlling on/off the drive current of a load with a smoothing effect, and a current value switching element for controlling the current value of the drive current by turning on/off the current. a means for controlling the smoothed current value by controlling the current value switching element on and off at a predetermined period; and a means for controlling the mode switching element on and off at a period longer than the period. . A drive current control method, characterized in that the smoothed current value is configured to flow through the load in a direction given by turning on and off the mode changeover switching element. 2. The drive current control method according to item 1, wherein the load is a coil of a DC motor. 3. A storage element storing the mode switching mode and the current value control, means for selecting the memory contents of the storage element, and means for setting the mode and the current value based on the selection. The drive current control method according to item 1. 4. a first address counter that sets the current value;
4. The drive current control method according to claim 3, wherein the storage content is selected in accordance with the count results of the second address counter and the first and second address counters for setting the mode. 5. The drive current control method according to item 1 or 3, wherein the current value is set by pulse width modulation. 6. The drive current control method according to item 1 or 3, wherein the current value is set by pulse frequency modulation. 7. The drive current control method according to item 1 or 3, further comprising means for controlling a controlled object other than the load in synchronization with the drive current of the load in accordance with the mode.