US3651892A - Switching techniques and devices - Google Patents

Switching techniques and devices Download PDF

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US3651892A
US3651892A US13660A US3651892DA US3651892A US 3651892 A US3651892 A US 3651892A US 13660 A US13660 A US 13660A US 3651892D A US3651892D A US 3651892DA US 3651892 A US3651892 A US 3651892A
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switch
condition
signal
waveform
output
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Andras I Szabo
Charles L Winkler
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CBS Corp
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Westinghouse Electric Corp
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
    • G05B19/07—Programme control other than numerical control, i.e. in sequence controllers or logic controllers where the programme is defined in the fixed connection of electrical elements, e.g. potentiometers, counters, transistors
    • G05B19/075—Programme control other than numerical control, i.e. in sequence controllers or logic controllers where the programme is defined in the fixed connection of electrical elements, e.g. potentiometers, counters, transistors for delivering a step function, a slope or a continuous function
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66B—ELEVATORS; ESCALATORS OR MOVING WALKWAYS
    • B66B1/00—Control systems of elevators in general
    • B66B1/24—Control systems with regulation, i.e. with retroactive action, for influencing travelling speed, acceleration, or deceleration
    • B66B1/28—Control systems with regulation, i.e. with retroactive action, for influencing travelling speed, acceleration, or deceleration electrical
    • B66B1/285—Control systems with regulation, i.e. with retroactive action, for influencing travelling speed, acceleration, or deceleration electrical with the use of a speed pattern generator
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
    • H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
    • H03K17/687—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being field-effect transistors
    • H03K17/6877—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being field-effect transistors the control circuit comprising active elements different from those used in the output circuit
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
    • H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
    • H03K17/687—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being field-effect transistors
    • H03K17/693—Switching arrangements with several input- or output-terminals, e.g. multiplexers, distributors

Definitions

  • SWITCH #2 CLOSED SWITCH #l CLOSED sIG-AI I SWITCHING TECHNIQUES AND DEVICES BACKGROUND OF THE INVENTION 1.
  • This invention relates to switching devices and techniques and more particularly to such devices and techniques for use in switching control signals wherein the application of a signal or the switching between signal sources must be smooth.
  • Smooth switching is also a problem in systems wherein a transfer is made from one signal source to another, as from a coarse control signal to a fine control signal or vice versa.
  • Such problems arise in the speed control systems for elevators. For instance, very often the speed control signal for acceleration and constant speed is generated as a function of time, while the speed control signal for the deceleration phase is controlled as a function of the distance remaining to the point at which the car is to stop.
  • a third signal generator is utilized to generate a very accurate speed control signal over the last few inches of travel to assure accurate landings.
  • the problem of providing smooth transition from one signal source to another is particularly acute in the elevator field since passengers are freestanding on a moving platform.
  • the transition time of the ramp function determines the transfer time from the full on to the full off condition of the switch and therefore establishes the rate at which the signal is applied or removed. Since the components which control this transfer time are in the control circuit for the switch and not in the circuit being switched, they do not affect the response of switched as would a filter. Consequently, the transfer time can be made reasonably slow without affecting the dynamic response of the system to the control signal once it is switched on.
  • the frequency of the sawtooth function determines the rate at which the switch is operated between the off and on conditions. If this rate is made rapid with respect to the response time of the system being controlled by the switched signal, the effect will be a smooth application or removal of the signal with the rate determined by the transition time of the ramp.
  • the invention can be used for switching smoothly from one control signal to another.
  • the transfer time will be determined by the transition time of the time ramp function and the rate of repetitive switching will be determined by the frequency of the sawtooth waveform.
  • the second switch is operated in opposition to the first switch by interposing a conventional NOT logic circuit between the comparator and the second switch. With this configuration, one switch will be on I00 percent of the time initially while the other one will be off I00 percent of the time. As the transition occurs, the relative percentage of contribution of the two signals will change progressively until the one switch will be off I00 percent of the time while the other switch will be on I00 percent of the time.
  • the ramp function is controlled as a function of time; however, the value of this waveform could be controlled as a function of another variable such as the position of the body being controlled.
  • the invention can also be applied to systems wherein a control signal is selected from more than among two signal sources.
  • a control signal is selected from more than among two signal sources.
  • a speed control signal is selected from among three signals
  • only one sawtooth generator is required while ramp function generators for each pair of signal sources between which a transfer is desired are required.
  • Separate comparators are required for comparing the value of the sawtooth waveform with the waveform of each of the ramp function generators.
  • Gate circuits operated by a supervisory control serve to insure that operation of a switch controlling a signal source common to two transfers is controlled by the output of the proper comparator.
  • FIG. I is a block diagram of a basic embodiment of the invention.
  • FIG. 2 is a block diagram of another embodiment of the invention adapted for use in switching between two signal sources;
  • FIG. 3 is a block diagram of yet another embodiment of the invention adapted for use in an elevator speed control system
  • FIGS. 4A through E illustrate waveforms appearing at- We: mihthrnssgifl'i.
  • FIG. I illustrates the invention as employed in a simple switching operation to control the circuit between the terminals A and B.
  • the device is composed of an analog switch I interposed in the circuit between these terminals.
  • An analog switch is a conventional type of a two condition switch which opens the circuit between terminals A and B in one condition and provides a short circuit so that the signal appearing at the terminal A appears at the terminal 8 when the switch is in the closed condition.
  • the switch could be of the electromechanical solenoid type, preferably the switch is a solid state switching device due to the rapid repetitive switching desired.
  • Solid state switches which are responsive to a digital control signal applied to a control Input 2 are well known.
  • An exemthe control system to the transients in the control signal being plary solid state switch is shown in FIG. I within the dashed line.
  • Base electrodes l3 and B, of a field effect transistor Q are connected between the terminals A and B.
  • a resistor R is connected between B, and the gate electrode, G, of 0..
  • the gate electrode is also connected to the collector of an NPN- transistor 0,.
  • the emitter of Q is energized by a v. DC source while the base of(), is connected to a l 2 v. DC source through resistor R,
  • the control input 2 is connected directly to the base of 0,.
  • the control signal for the analog switch is generated by a comparator 3 which has one output when the instantaneous value of a signal applied to an input 4 exceeds the instantaneous value of signal applied in input 5 and a second output when the signal applied at the input 5 exceeds the value of the signal applied at the input 4.
  • Comparators displaying such characteristics, and having as one output a zero voltage signal and having as a second output a signal of a fixed magnitude are well ltnown.
  • Signals to be compared by the comparator 3 are supplied by a first function generator 7 which generates a repetitive waveform. preferably a sawtooth waveform, and a second function generator 8 which preferably generates a ramp function.
  • the sawtooth function generator 7 can operate continuously while the ramp function generator 8 maintains an output of one peak value or the other until triggered by a transition signal. whereupon the ramp function transitions to the opposite pealt value.
  • Function generators of these general characteristics are also well known.
  • the transition time of the ramp function is the operative factor which detennines the rate at which the analog switch is operated from its predominantly closed to its predominantly open condition.
  • FIG. 40 if a continuous signal shown by the dotted line a is present at the input terminal A, the signal appearing at the terminal 8 is represented by the solid line b. Again this is an idealized representation which illustrates the theoretical signal which would appear at the terminal 8.
  • the signal at terminal B will approach this signal as the frequency of the sawtooth waveform is increased with respect to the transition time of the ramp function. it can be seen however. that the signal at terminal 8 will be zero until the ramp function begins to exceed the value of the sawtooth function during part of the cycle of the sawtooth function.
  • the signal applied to the tenninal A appears at the terminal B smoothly over a period of time determined by the transition time of the ramp function. As was mentioned previously. this transition time in one application has been set at three tenths of a second. It will be noted however. that once the switching has been completed there is no restriction in the circuit between the terminals A and B toinhibit the response of a component connected to the terminal 8 to transient signals applied to the terminal A.
  • the signal appearing at A can be applied to the system connected to the terminal B at a rate which is compatible with the dynamic characteristics of the load but yet it does not interpose a reduction in the response time of the system.
  • the filter is to dampen the response of the system to the transient caused by the switching operation it will also dampen the response of the system to transients in the control signal applied to the terminal A. According to this invention however.
  • the low pass filter 9 which may be interposed in the load circuit will pass all frequencies occurring in the normal transients of the control signal applied to the terminal A. it merely eliminates the high frequency transients caused by the switching operation itself and, as was mentioned, if the cutoff frequency of the system is low enough, this filter is not necessary.
  • FIG. 2 illustrates the application of the invention to a dual switching operation for switching between two signal sources.
  • the two signal sources are connected to the terminals A and A.
  • Analog switch l is interposed between terminal A and the output tenninal B while the analog switch I 2 is interposed between the terminal A and the output terminal 8.
  • the analog switch ll is controlled by the signal applied to its control terminal 2 in a manner similar to that described for the control of the analog switch in the device of FIG. l.
  • analog switch 01 is controlled by the output of the comparator 3 which generates a digital signal having a value of either zero or one depending upon whether the value of a sawtooth waveforrn applied to input terminal 4 of the comparator is larger than, or less than, the value of a ramp function applied to the input terminal 5 of the comparator.
  • the analog switch I l of HO. 2 will respond to the relative values of the ramp function and the sawtooth function as did the analog switch of FIG. I so that its condition is represented by the FIGS. 4A and 4B.
  • the additional analog switch 02 is also operated between its open and closed condition by a control signal applied to its control terminal 2'.
  • the control terminal 2' is connected to the output of the comparator 3 through a conventional NOT-logic circuit ill.
  • the conventional NOT circuit reverses the digital signal applied to its input. For instance, if a ONE is applied to the input of the NOT element a ZERO output is produced and vice versa.
  • control signal applied to the control input 2' of analog switch 0 2 will at all times be opposite to the control signal applied to the control terminal 2 of the analog switch 0 1. It is clear then that when the analog switch 0 l is in closed condition analog switch I 2, which is identical to the analog switch 0 I, will be in the open condition and vice versa.
  • a summing circuit ll connected to the two analog switches supplies the combined signal to the terminal B.
  • the summing circuit can be a conventional operational amplifier which may also be modified to act as a low pass filter if necessary. Alternatively, the summing circuit could be replaced by a voltale follower circuit.
  • FIG. 45 illustrates the operation of the circuit of FIG. 2.
  • the signal I 1 shown as a dashed line is applied to terminal A and that signal I 2 illustrated as a dotted line is applied to the terminal A'.
  • the solid line represents the resultant signal appearing at the terminal B assuming that the summing circuit ll does not operate as a low pass filter.
  • the dash dot line curving between the signal 0 2 and signal 01 represents the effective value of the signal appearing at the terminal B assuming that the summing circuit ll also acts as a low pass filter.
  • FIG. 3 illustrates the application of the invention to an elevator speed control system.
  • elevator car 20 is suspended from a cable 21 which passes over a sheave 22 and is connected to a counterweight 23.
  • the car 20 is caused to travel up and down serving a number of landings by a motor 24 which rotates the sheave 22 through a shaft 25.
  • the shaft 25 also drives a floor selector 26.
  • the floor selector is a device well ltnown in the elevator art which follows the position of the car relative to the landings and cooperates with a supervisory control 27 to initiate the stopping of the elevator car as it approaches a floor at which service is desired.
  • the floor selector operates as a pattern generator which develops a speed control signal as a function of the distance remaining to a floor at which the car is to stop.
  • a time ramp generator 28 which is triggered by the supervisory control system when the car is to start, can be utilized to generate a control signal for controlling the speed of the car during acceleration. It has become common practice to utilize this ramp generator also to control the speed of the car during the constant speed phase. However, as the car approaches a landing at which it is to stop, accurate landings with smooth deceleration and no overshoot can be achieved by controlling the speed of the car as a function of the distance remaining to be traveled. This signal is most often generated by pattern generator connected to the floor selector.
  • this signal produced by the pattern generator is a rough signal which controls the car very well during the initial stages of deceleration.
  • a third signal generator to control the speed of the car precisely during the last critical inches of travel.
  • a device for producing this fine signal is illustrated in US. Pat. No. 2,874,806.
  • an electromagnetic transducer 29 connected to the elevator car is activated as the car approaches a landing at which it is to stop.
  • Diamond shaped magnetic plates P located adjacent each landing. vary the coupling between the poles of the transducer. The inductor plates are so located with respect to the landings that a null signal is produced by the transducer when the car is exactly level with the landing.
  • the speed of the car then is controlled by a signal developed either by a time ramp generator. at distance dependent pattern generator or a landing transducer depending upon the phase of the trip.
  • the application of the selected signal to the motor control circuits is governed by three analog switches similar to those discussed in connection with FIGS. 1 and 2.
  • a time ramp generator which is controlled by a supervisory control system supplies a control signal during acceleration and at constant speed through the analog switch I].
  • the pattern generator which supplies the signal to the motor control circuit during the deceleration phase is controlled by the analog switch 02.
  • the landing transducer which supplies a control signal during the landing phase is rendered effective by analog switch 03.
  • the output of the terminals of the three switches are connected to the summing and filter circuits ll similar to that discussed in connection with FIG. 2 which in turn supplies the resultant control signal to the motor and control circuits 24.
  • the switching of analog switches O l and 2 is controlled by a circuit similar to that shown in H0. 2.
  • the instantaneous magnitudes of a sawtooth waveform generated by function generator 7 and of a ramp function generated by function generator 8 determine the digital output of a comparator 3.
  • the output of the comparator 3 is reversed by a NOT-circuit before being applied to the control input of analog switch 2.
  • the transition of the ramp function is controlled by a transition signal which is generated by the supervisory control 27. in these respects this portion of the circuit of FIG. 3 is identical to that of FIG. 2.
  • a second comparator 3 compares the instantaneous value of the sawtooth wavefonn 7 and a ramp function generated by an additional function generator 8 to also control the switching of analog switch 0 2 in addition to analog switch 0 3.
  • a NOT-circuit l0 interposed between the comparator and analog switch '3. assures that opposing control signals will be applied to analog switch I 2 and analog switch 03 by the comparator 3'.
  • the function generator 8' is also controlled by a transition signal generated by the supervisory control 27.
  • AND-gates 30 and 32 are interposed between comparators 3 and 3' and analog switches O l and I 2 respectively.
  • AND-gates 3i and 33 are interposed between NOT-elements l0 and 10' and analog switches 0 2 and O 3. All of these AND gates have two inputs and a single output. These gates are the conventional AND logic gates which have a ONE output only when a signal is applied to both in uts.
  • the second input to gates 30 and 31 is the signal A generated by the supervisory control system 27.
  • the second input to AND-gates 32 and 33 is the signal LAND generated by the supervisory control system.
  • Signals LAND and [AND are complementary signals in that when one of these signals is equal to ONE.
  • the other one is equal to ZERO.
  • the output of only one AND circuit at a time can be equal to ONE. For instance. if the signal LAND is equal to ONE the signal LAND will be equal to ZERO and therefore the output of AND-gates 32 and 33 cannot be equal to ONE regardless of the value of the other input. Since the second input to the AND-gate 3
  • the out ut of comparator 3 will be equal to ONE. Since the signal LA is also equal to ONE. the signal supplied to the control input of analog switch 0 l by the AND-gate 30 will be equal to ONE to operate the analog switch 0 l to the closed position. Since a ZERO will be supplied to the AND-gate 31 by the NOT-element 10. a ZERO signal will be supplied to the control input of analog switch a 2 by AND-gate 31. Therefore, with a triggering of the time ramp generator 28 by the supervisory control. the control signal generated by this element will pass through the closed analog switch 0 l and the sum'ming circuit ll to the motor and its control 24.
  • Energization of the motor in turn will cause the car 20 to begin to accelerate. Movement of the car will cause the floor selector to move in synchronism with it thereby following the position of the car. Movement of a car will also cause operation of the pattern generator which generates a speed control signal as a function of distance required for the car to come to a stop. however. this signal will not be applied to the motor control circuit since the analog switch I 2 is held in the open condition.
  • a transition signal will be supplied to the ramp function generator 8.
  • the output of the comparator 3 will reverse during those intervals when the value of the ramp function exceeds the instantaneous value of the sawtooth function.
  • analog switch 0 1 will be closed while the analog switch 0 2 will be open due to the operation of the NOT circult 10.
  • the analog switch 0 1 will progressively remain longer in the closed condition as the analog switch 0 2 remains progressively longer in the open condition until full transfer is achieved and the analog switch 01 will remain.
  • the supervisory system will cause the LAND signal to go to ZERO thereby causing the LAND signal to go to ONE.
  • This will transfer control of the switching of the analog switches to the output of the comparator 3 since. with the signal LAND equal to ZERO. the outputs of AND-elements 30 and 31 are clamped at ZERO. it will be assumed that at this point. with the output of the function generator 8' at its minimum value. the output of comparator 3' will be equal to one to maintain the analog switch 0 2 in the closed condition so that the control signal generated by the pattern generator will be continuously applied to the motor control circuit 24. At this time.
  • the supervisory controlsystem will supply a transition signal to the function generator 8 to initiate a transfer from the pattern generator to the landing transducer.
  • the output of the comparator 3 will go to ZERO thereby switching analog switch 0 2 to the open condition and analog switch I 3 to the closed condition. in a manner which should be evident at this point. the signal generated by the pattern generator will be smoothly replaced by the signal generated by the landing transducer.
  • a switching device comprising a switch having an input terminal and an output terminal. said switch being operative between a first condition wherein a circuit is completed between the input terminal and the output terminal and a second condition wherein no circuit is completed between the terminals. and control means for operating said switch between said first and second conditions including means operative to rapidly and repetitively operate the switch between said first and second conditions with said switch initially remaining in one condition longer than the other and then progressively less in the one condition and longer in the 7 other condition until the switch remains in the other condition substantially continuously.
  • the device of claim l including a summing circuit operative to produce an output signal which is a combination of the signals applied to the summing circuit. a first signal source connected to said summing circuit. a second signal source connected to the input of said switch and means connecting the output of said switch to said summing circuit whereby the signal generated by the second signal source can gradually be added to or removed from the signal appearing at the output of the summing circuit through the operation of said control means to operate said switch from being predominantly in one condition to being predominantly in the other condition.
  • control means comprises a first function generator operative to generate a repetitive signal. a second function generator operative to generate a second signal having a time constant which exceeds the period of oscillation of said first signal. and a comparator for comparing the instantaneous values of the signals generated by said function generators and having a first output when the instantaneous value of a first one of said signals exceeds the instantaneous value of the other and having a second output when the instantaneous value of the other signal exceeds that of said one signal.
  • said switch being operative to one condition in response to the first output of said comparator and operative to said other condition in response to said second output.
  • a signal generated by said first function generator is substantially a sawtooth signal wherein the signals generated by the second function generator is substantially a ramp function. the minimum value of said ramp function being less than the minimum value of said sawtooth function while the maximum value of the ramp fimction exceeds that of said sawtooth function whereby the output of the comparator and therefore the condition of the switch will remain constant except while said ramp function generator is transitioning between its peak values.
  • the device of claim 1 including a second switch which is operative between a first condition wherein a circuit is completed between an input terminal and an output terminal and a second condition wherein no circuit is completed between the terminals, and wherein the control means includcs coupling means operative to operate said second switch between said first and second conditions in opposition to the operation of said first switch between said'first and second conditions whereby as said first switch is operated from being predominantly in said one condition to being predominantly in the other condition. said second switch is operated from being predominantly in said other condition to being predominantly in said one condition.
  • control means comprises a first function generator operative to generate the repetitive waveform.
  • a second function generator operative to generate a second waveform having a time constant which exceeds the period of oscillation of said first waveform, and a comparator for comparing the instantaneous values of the first and second waveforms and having a first output when the instantaneous value of one waveform exceeds that of said other waveform and having a second output when the instantaneous value of said other waveform exceeds that of said one waveform.
  • said first switch being operative to said first condition in response to one output of said comparator and being operative to said second condition in response to the other output of said comparator while said coupling means operates said second switch to said second condition in response to said one output of said comparator and operates it to said first condition in response to the other output of said comparator.
  • the device of claim 6 adapted for use in a control system wherein the second waveform is essentially a ramp function with a minimum value which is less than the minimum value of said repetitive waveform and a maximum value which exceeds the maximum value of the repetitive waveform and including a first control signal source connected to the input terminal of said first switch. a second control signal source connected to the input terminal of said second switch. and a summing circuit connected to the outputs of said switches whereby the control signal appearing at the output of the summing circuit is one control signal or the other while the ramp function is at its maximum or minimum value and is progressively switched from one control signal to the other as the ramp function transitions from one peak value to the other.
  • the combination of claim 7 including a third switch operative between a first condition wherein a circuit is completed between an input terminal and an output terminal and a second condition wherein no circuit is completed between the tenninals.
  • a third control signal source connected to the input of said third switch the output of said third switch being connected to the summing circuit.
  • an additional second function generator operative to generate a waveform having a time constant which exceeds the period of oscillation of said first waveform.
  • an additional comparator connected to the first htnction generator and the additional second function generator and having a first output when the value of one of these waveforms exceeds that of the other and having a second output when the value of the other waveform exceeds that of said one waveform.
  • additional coupling means for operating said second and third switches in opposition to each other in response to the output of said additional comparator and actuating means operative to selectively actuate a selected second function generator to initiate a switching from one control signal to another.
  • a method of operating a first switch having an open circuit condition and a closed circuit condition from being predominately in a first one of said conditions to being predominately in a second one of said conditions. comprising the steps of: generating a repetitive function, generating a ramp function when it is desired to operate said first switch.
  • said ramp function having minimum and maximum values which are less than, and greater than, the respective minimum and maximum values of the repetitive function, comparing the repetitive and ramp functions, operating said first switch repeatedly between said first condition and said second condition in response to the instantaneous value of the repetitive function exceeding and dropping below the instantaneous value of the ramp function, with the interval that said switch remains in each condition being varied according to the transition time of the ramp function, so that initially it remains longer in said first condition and then progressively less in said first condition and longer in said second condition until it remains predominately in said second condition.
  • a method of operating a switch having an open circuit condition and a closed circuit condition from being predominately in a first one of said conditions to being predominately in a second one of said conditions comprising the steps of generating a repetitive waveform, generating a transition waveform which transitions between a minimum value which is less than the minimum value of the repetitive waveform and a maximum value which exceeds that of said repetitive waveform, comparing the instantaneous values of the two waveforms, operating said switch to said first condition when the instantaneous value of a first one of said waveforms exceeds that of said other waveform and operating said switch to said second condition when the instantaneous value of said first waveform is less than that of said other wavefonn.
  • the method of claim [4 adapted for switching between a plurality of signal sources controlled by switches similar to said switch including the steps of generating a transition waveform for each transfer between signal sources desired, selecting the pair of signal sources between which the transfer is to be made, operating a first switch controlling a first one of the selected signal sources to said first condition when the instantaneous value of the associated transition waveform exceeds that of said repetitive waveform, operating said first switch to said second condition when the instantaneous value of the associated transition waveform is less than that of the repetitive waveform and operating a second switch controlling the second one of the selected signal sources between its first and second conditions in opposition to said first switch.

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  • Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Studio Circuits (AREA)
  • Inverter Devices (AREA)
  • Control Of Direct Current Motors (AREA)
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JP (1) JPS523546B1 (fr)
BE (1) BE763355A (fr)
DE (1) DE2107410A1 (fr)
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US3919650A (en) * 1973-08-15 1975-11-11 Mi 2 329102 Mark frequency detector circuit
US20050206413A1 (en) * 2004-03-18 2005-09-22 Lin Jyh C Current driving apparatus using PWM

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JPS5436528Y2 (fr) * 1973-02-21 1979-11-05
JPS50122837U (fr) * 1974-03-22 1975-10-07
JPS5167786U (fr) * 1974-11-22 1976-05-28
US4331220A (en) * 1980-11-04 1982-05-25 Westinghouse Electric Corp. Elevator system
JPS59113771A (ja) * 1982-12-20 1984-06-30 Mitsubishi Electric Corp 電力制御装置の起動停止方法
JPS6414324A (en) * 1987-07-07 1989-01-18 Nippon Spindle Mfg Co Ltd Method for regulating acceleration in starting spinning machine

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US3516518A (en) * 1965-10-13 1970-06-23 Otis Elevator Co Elevator control system

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US3919650A (en) * 1973-08-15 1975-11-11 Mi 2 329102 Mark frequency detector circuit
US20050206413A1 (en) * 2004-03-18 2005-09-22 Lin Jyh C Current driving apparatus using PWM
US7078942B2 (en) * 2004-03-18 2006-07-18 Hon Hai Precision Ind. Co., Ltd. Driving apparatus for generating a driving current using PWM

Also Published As

Publication number Publication date
JPS523546B1 (en) 1977-01-28
GB1293097A (en) 1972-10-18
FR2083101A5 (fr) 1971-12-10
NL7102444A (fr) 1971-08-26
BE763355A (fr) 1971-08-24
DE2107410A1 (de) 1971-09-09
JPS462768A (fr) 1971-10-21

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