US3198962A

US3198962A - Transistorized control system

Info

Publication number: US3198962A
Application number: US232106A
Authority: US
Inventors: Leon R Lease
Original assignee: Electrol Equipment Inc
Current assignee: Electrol Equipment Inc
Priority date: 1962-10-22
Filing date: 1962-10-22
Publication date: 1965-08-03
Anticipated expiration: 1982-08-03

Description

g- 3, 1965 L. R. LEASE 3,198,962

TRANSTSTORIZED CONTROL SYSTEM Filed Oct. 22, 1962 2 sheets sheet 1 BASE 2 I I8 9 I3 352%; MW l9 s -.o. MC. W H4; m

Jr? /6\ V17 Nov N-c H: w

I64 --l7 l /5 ,5 Kl

L E Z q Ag SENSING COIL EX C TER FIELD I NVEN TOR. LEON R. LEA 85 FIG. 3 9%R'2UMM ATTORNEYJ United States Patent [all 3,18,9-52 TRANSESTGREZED CGNTRQL SYSTEM Leon R. Lease, Manlrato, Winn assignor to Electra)! Equipment, Inc, a corporation oft Minnesota Filed Get. 22, 1962, Ser. No. 2392,1436 11 Claims. (Cl. 307-885) This invention relates to transistorized control systems and particularly to systems including a power transistor controlled through the use of contacts. Specifically, the present invention relates to transistorized control systems including switch means with one normally open pair of contacts and one normally closed pair of contacts in a single pole-double throw arrangement for controlling a power transistor, this basic system being adapted to use in many and varied specific electrical applications.

The present invention provides a control means for switching direct current by means of a transistor through the use of contacts, specifically in a single pole-double throw arrangment. The basic structure of the control system of the present invention provides a means for switching the power to inductive, resistive or capaacitive loads, or a combination thereof, without directly having to make or break the set current providing the power to said load, by means of switch contacts whether a direct switch or a relay switch and whether manually, mechanically, electrically or hydraulically operated.

The system of the present invention makes possible the switching of higher currents than would normally be permissible for the particular contacts used as provided by good practice, thereby eliminating contact erosion due to sparking and much of the radio interference caused by sparking when said currents are switched directly with contacts. A power transistor in a switching mode is controlled in such a way that the switch contacts cannot establish or maintain an are thereby eliminating radio interference and contact erosion and greatly enhancing the serviceable life of the control means.

The basic circuit of the control system of the present invention is useful, for example, in generator voltage regulators where the transistorized control circuit is employed to switch the generator exciter field current so that the generator voltage is controlled in a predetermined manner, most generally at an essentially constant level.

Another use of the basic control circuit is in generator .voltage regulators where the generator field current is controlled by the transistorized circuit to control the output voltage or" the generator in a predetermined fashion, generally at an essentially constant level.

A still further use of the control system circuit is in th output current control of generators where the output current of the generator is controlled in a predetermined fashion, generally at a constant level, or, in the case of a D.C. generator, the output current is controlled at either on or oil or in between at any level between on and off.

The control circuit is useful as a regulating element of regulated DC. power supplies whether used to control the voltage at a predetermined level, or to control the current at a predetermined level, or a combination of the two.

Still another application of the control circuit of the present invention is as a control element in a battery charger for maintaining a battery at full charge. The control circuit may be so used whether the battery charger is of the transformer-rectifier type or is a rotating battery charger.

The control circuit may be used in the control of the field of direct current motors to maintain the motor speed generally at a constant level. The same means of control is useful in the armature of direct current motors for the control of the motor speed.

The control circuit is useful for controlling the speed of universal motors run ofi direct current in full on or off condition or any intermediate condition.

The control circuit is useful in the switching of large or small amounts of direct current under circumstances where the voltage and current would likely cause arcing with normal DC. relays.

The control circuit is useful for the transistorizing of the ignition systems of automobiles to give the points indefinite lite.

The structure of the control system circuit and its versatility in means of control are shown in the accompanying drawings in which the same numerals refer to corresponding parts and in which:

FIGURE 1 is a single pole-double throw switch operated circuit including a PNP transistor;

PEGURE 1A is a similar circuit including an NPN transistor;

FEGURE 2 is a simple electromagnetic sensing operated circuit;

FIGURE 3 is an electromagnetic senser with D.C. feed backs operated circuit; and

FiG-URE 4 is an electromagnetic senser with A.C. feed backs operated circuit.

As shown in FIGURES 1 and 1A, the transistorized control circuit in its simplest form comprises a PNP transistor, indicated generally at 10, or an NPN transistor, indicated generally at 13A, each including an emitter ll, collector l2 and base 13, inserted in a power line 14 which along with line 15, extends from a source of electrical power or input to an output or load, which may be any'of a variety of devices for absorbing or converting the power from the power source.

A single pole-double throw switch including normally open contacts 16 and normally closed contacts 17 is provided, with the common terminal of the contacts connected to the base lead of the transistor, the other terminal of the normally open contacts connected to the emitter lead of the transistor and the other term nal of the normally closed contacts connected to the collector lead of the transistor. The contacts may be those of a direct switch or a relay switch, whether manually, mechanically, electrically or hydraulically operated.

A resistor 18 is connected between the emitter and base across the terminals of normally open contacts 16 and a resistor 12* is connected betweenthe base and collector across the terminals of normally closed contacts 17.

When the normally closed contacts 17 are such that the base 13 to collector 12 is shorted, the transistor is in the saturated condition at full turn on where the base to emitter voltage is generally in the neighborhood of 0.2 volt, although this voltage may vary between about 0.1 to 0.5 volt. When both contacts are open during the operation of the switch, the ratio of the resistor 18 between the emitter i1 and base 13, to the resistor 19 between the base 13 and the collector 12 determines the percentage of turn on. This should, in general, be between about 10% and 40% of full turn on.

When the normally open contact 16 becomes closed, the emitter 11 to base 13 is shorted. Consequently, that potential is at zero and the transistor becomes fully turned off and the only current that can flow at that time is the current flowing through the resistor 19 connected between the base 13 and collector 12. This, in general, will be in the range of milliamperes. Thus, using a simple single pole-double throw switch enables the transistor to be turned fraorn full on to partially on to full off in a three step operation in which the contacts switchvery little power.

In general, the emitter to base voltage when the transistor is in the normally saturated condition will be ape proximately 0.20 volt and when both contacts are open there will be approximately 0.35 volt between the emitter and base. Assuming that the entire base current, which is generally less than 100 milliamps, is switched from 0.35 volt to 0.20 volt, or a difference of 0.15 volt, a total power of 0.015 watt is switched. The potential at which these contacts have to open, and the current through them, are not sufiicient to maintain or establish an arc with the result that radio interference due to sparking and erosion, or contact wear due to sparking, is virtually eliminated.

As shown in FIGURE 2, most applications in which the control circuit of the present invention is used in corporate an electromagnetic sensing element which in turn activates the contacts, which in turn control the transistor. Thus, in FIGURE 2, there is shown a simple electromagnetic sensing operated circuit in which the normally open contacts 16A and normally closed contacts 17A may be those of a relay. The

contacts

16A and 17A are operated in response to an electromagnetic sensing coil 29, which may be a relay coil, having sensing leads 21 and 22. The sensing coil may be connected from positive to negative, across the load, or it may have completely separate sensing.

When the control circuit is used in conjunction with an electromagnetic sensing element in a circuit as a regulator for a generator, for example, the normally closed contacts 17A drive the transistor into full turn on. The current through the transistor, and consequently through the field of the generator which is in series with the transistor, remains at full value until the voltage rises to its nominal value. The nominal value is pre-set at the point where the electromagnetic sensing element will activate the contacts.

At nominal voltage, the contacts 17A that normally short the base to the collector open, and the ratio of the two

resistors

18 and 19 connecting the emitter to the base and the base to the collector across the transistor determines the ratio of turn on, which should be between about to 70% and more generally between about and 40%. This immediately cuts back the field to between 5% to 70%, or about 10% and 40%. If this is still too high, so that the generator voltage rises above the nominal value, the contacts 16A connecting the base to the emitter close shorting these two points and bringing the base potential to that of the emitter. This consequently turns otf the transistor fully.

The only field current that is then available must go through the resistor 19 connecting the base to the collector. This, in general, is a high valued resistor which would normally allow only milliamperes of current to flow, as compared to the amperes required for full voltage on the generator.

When the current on the field is reduced to essentially zero, as happens when the emitter is shorted to the base, voltage must drop until it goes back to normal at which time the contacts 16A shorting the emitter to the base open again and allow from 10% to 40% of the current to fiow once more. If this is not sufiicient to energize the generator to nominal voltage, the voltage would drop further, at which point the contacts 17A shorting the base to the collector close and allow full potential to be applied to the field momentarily. This in turn causes the gem erator voltage to rise once more at which point the con tacts 17A open and the cycle is repeated.

Essentially, this causes a modulation of the generator voltage over a narrow band such that the contacts can be operated in sequence. The point where the normally closed contacts 17A open is a lower voltage than the point where the normally open contacts MA close. Consequently, there will be a modulation of that generator voltage, which in turn is applied to the electromagnetic senser between these two points as determined by the sensitivity of the senser. The control of the generator voltage is accomplished by the rapid switching at a rate of hundreds of times per second of the generator field cur- Itint'Or the exciter field current, as the case may be, from a condition of full turn on to part turn on to zero turn on, or between any two of these three steps.

The principal advantage is that the electromagnetic senser causes the transistor to operate in two or more of these conditions hundreds of times each second. Consequently, the regulator is many times faster than is the time constant of the generator where it would ordinarily be used. This rapid regulator response and its ability to turn fully on will give exceptionally fast recovery of generator voltage on the application of load. Its ability to turn fully ofi will give similarly fast recovery of voltage on load rejection. Modulation of the generator voltage envelope is minimized by the extremely fast-sensitive senser. Life is indefinite as the transistor, and not the contacts, switch tie field current. Consequently, the normal inductive load of the generator or exciter fields cannot cause an arc and create radio interference or contact erosion reducing contact life.

A further advantage of the control system of the present invention is that as ambient temperature increases, the field requires more voltage and consequently absorption requirements placed on the transistor are less. Further, as the temperature of the transistor rises, the forward drop of the transistor becomes lower allowing the required field current to flow with even less transistor absorption at the higher ambient temperature.

Another major advantage of the control system is that the gain of the transistor increases with increasing temperature which gives the transistor the effect of being more nearly at full turn on and full turn 05. This also reduces the absorption requirement of the transistor at higher ambient temperatures. Since the transistor operates in a switching mode during which it is operating a large percentage of the time at either full turn on or full turn off it is capable of handling several times the normal power capabilities of the transistor. In other words, in the case of a normal watt transistor at 25 C. case temperature, it is possible that by keeping the case temperature at 25 C. switching in the neighborhood of 700 to 1,000 watts may be accomplished. Even where the case temperature rises and the power dissipation consequently goes down, the system is still capable of switching several times the normal power dissipation of the transistor.

In FIGURE 3 there is shown a control circuit operated by an electromagnetic senser with D.C. feed-back in connection with a voltage regulator.

Terminals

1, 2, 3, 4 and 5 are those of the regulator,

terminals

1 and 2 being connected to the exciter field. Transformer T-l is a sensing transformer which reduces volts AC. to 12 volts A.C. Rectifiers CR]. and CR-2 are sensing recti fiers which change 12 volts AC. to 12 volts D.C. Rectifier CR-S protects transistor 10 against inverse voltage spires. Rectifier CR-'-4 allows current to flow when transistor 10 is in off position.

Windings

23 and 24 are feed-back windings on electromagnetic senser 20.

Contacts

16A and 17A are the normally open and normally closed contacts, respectively, which are responsive to the electromagnetic senser. Resistors 1S and 19 are the bias resistors for transistor 10.

In FIGURE 4 there is shown a control circuit operated by an electromagnetic senser with AC. feed-back in connection with a generator voltage regulator of a vehicle. The regulating and control portion of the circuit is indicated within

broken line boxes

25 and 25A.

Terminals

1, 2, 3, 4 and 5 are the terminals of the regulator, terminal 1 being for connection to the positive pole of the vehicle battery, terminal 2 being for connection to the negative pole of the battery, terminal 3 being for connection to the ignition coil of the vehicle and

terminals

4 and 5 being for connection to the exciter field. Normally open relay contacts K2 are activated by power to the vehicle ignition coil. Rectifiers CR1(2) and Cit-1(3) are power rectifiers; rectifiers CR1(1) and CR1(4) are sensing and power rectifiers; and rectifiers CR-Z and CR-S are sensing rectifiers. The sensing rectifiers change A.C. to D.C. for the electromagnetic sensor 20. Winding 26 is a feed-back winding on electromagnetic senser 20. Low (12 volts A.C.) voltage is supplied by the generator. Higher (110 volts A.C.) voltage is supplied to the receptacles. Frequency sensitive circuit 27 indicates if frequency is above 60 cycles, at 60 cycles, or below 60 cycles.

According to the present invention the switch means controls the transistor as distinguished from prior art circuits in which the transistor controls a relay or other switch means. The actual power switching is accomplished by the transistor, and not the switch means con tacts, nor do the contacts conduct the major portion of current.

It is apparent that many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof. The specific embodiments described are given by way of example only and the invention is limited only by the terms of the appended claims.

I claim:

1. A control system including a transistor and a single pole-double throw switch means, one of the pairs of contacts of said switch means being normally open and the other pair of contacts being normally closed, the common terminal of said pairs of contacts of said switch means being connected to the base of said transistor, the other terminal of one of said pairs of contacts being connected to the emitter of said transistor and the other terminal of the other of said pairs of contacts being connected to the collector of said transistor, a first resistor connected between the emitter and base of said transistor and another resistor connected between the base and collector of said transistor.

2. A control system according to claim 1 further characterized in that said switch means are electromagnetically actuated and said system includes an electromagnetic sensing element.

3. A control system according to claim 2 further characterized in that said switch means are relay contacts and said sensing element is a relay coil.

4. A control system according to claim 1 further characterized in that the ratio of said first resistor to said other resistor is such that when both pairs of contacts are open current flow is about 5% to 70% of full current flow.

5. A control system according to claim 1 further characterized in that said transistor, switch means and resistors are connected in a power line between a power source and load to be acted upon by said power source, the emitter of said transistor being connected to said power source and the collector of said transistor being connected to saidload. A

6. A control system according to claim 1 further characterized in that said normally open contacts of said switch means are connected between the emitter and base or" said transistor and said normally closed contacts are connected between the base and collector of said transister.

'7. A control system including a transistor and a single pole-double throw switch means, said switch means including one normally open pair of contacts and one normally closed pair of contacts, said switch means including one terminal common to both pairs of contacts, said common terminal being connected to the base of said transistor, the other terminal of said normally open contacts being connected to the emitter of said transistor, the other terminal of said normally closed contacts being connected to the collector of said transistor, a first resistor connected between the emitter and base of said transistor and another resistor connected between the base and collector of said transistor.

8. A control system according to claim 7 further characterized in that said switch means are electromagnetically actuated and said system includes an electromagnetic sensing element.

9. A control system according to claim 8 further characterized in that said switch means are relay contacts and said sensing element is a relay coil.

10. A control system according to claim 7 further characterized in that the ratio of said first resistor to said other resistor is such that when both pairs of contacts are open current flow is about 5% to of full current flow.

11. A control system according to claim 7 further characterized in that said transistor, switch means and resistors are connected in a power line between a power source and load to be acted upon by said power source, the emitter of said transistor being connected to said power source and the collector of said transistor being connected to said load.

References Cited by the Examiner UNITED STATES PATENTS 2,763,832 9/56 Schockley 307-885 3,112,410 11/63 Schmid 307-885 ARTHUR GAUSS, Primary Examiner.

Claims

1. A CONTROL SYSTEM INCLUDING A TRANSISTOR AND A SINGLE POLE-DOUBLE THROW SWITCH MEANS, ONE OF THE PAIRS OF CONTACTS OF SAID SWITCH MEANS BEING NORMALLY OPEN AND THE OTHER PAIR OF CONTACTS BEING NORMALLY CLOSED, THE COMMON TERMINAL OF SAID PAIRS OF CONTACTS OF SAID SWITCH MEANS BEING CONNECTED TO THE BASE OF SAID TRANSISTOR, THE OTHER TERMINAL OF ONE OF SAID PAIRS OF CONTACTS BEING CONNECTED TO THE EMITTER OF SAID TRANSISTOR AND THE OTHER TERMINAL OF THE OTHER OF SAID PAIRS OF CONTACTS BEING CONNECTED TO THE COLLECTOR OF SAID TRANSISTOR, A FIRST RESISTOR AND ANOTHER RESISTOR CONNECTED BETWEEN THE BASE AND COLLECTOR OF SAID TRANSISTOR.