US3114091A

US3114091A - Variable power drive system

Info

Publication number: US3114091A
Application number: US7655A
Authority: US
Inventors: Edwards Robert
Original assignee: Electronic Assistance Corp
Current assignee: Electronic Assistance Corp
Priority date: 1960-02-09
Filing date: 1960-02-09
Publication date: 1963-12-10
Anticipated expiration: 1980-12-10

Description

Dec. 10, 1963 R. EDWARDS 3,114,091

VARIABLE POWER DRIVE SYSTEM Filed Feb. 9. 1960 2 Sheets-Sheet l '74 2 ll /2 V VARIABLE g OSCILLATOR AMPLIFIER AMPL'F'ER DRIVER OUTPUT TRANSDUCER FIG. 2.

INVENTOR. ROBERT EDWARDS his ATTORNEYS.

Dec. 10, 1963 R. EDWARDS 3,114,091

VARIABLE POWER DRIVE SYSTEM Filed Feb. 9, 1960 2 Sheets-Sheet 2 TRANSISTOR 25 COLLECTOR (CONTROL RESISTOR 22 SET AT LOW VALUE) TRANSISTOR 25 COLLECTOR (b) (CONTROL RESISTOR 22 SET AT HIGH VALUE) SECONDARY WINDING 29 (CONTROL RESISTOR 22. SET AT LOW VALUE) SECONDARY WINDING 29 (CONTROL RESISTOR 22 SET AT HIGH VALUE) IN VEN TOR. ROBERT EDWARDS his ATTORNEYS.

United States Patent 0.

3,114,091 VARIABLE POWER DRIVE SYSTEM Robert Edwards, Westfield, N.J., assignor to Electronic Assistance Corporation, Red Bank, NJ a corporation of New York Filed Feb. 9, 1966, Ser. No. 7,655 '7 Uaims. (Cl. 318-118) This invention relates to an electrical drive system and, more particularly, to a drive system for a transducer having means to vary the power output.

Many transducer drive systems have been provided in the past for delivering an ultrasonically varying voltage and a relatively high amount of power. These circuits have proved to have serious disadvantages, however, in that they have very low eiliciency ratings, require a cooling system because they generatetoo much heat, and dissipate too much power at the power varying means. Another serious problem has been in matching impcdances between the transducer being driven and the system.

Accordingly, it is a purpose of this invention to provide a variable power drive system for a transducer that obviates the above-described disadvantages. This purpose is attained, in accordance with a preferred embodiment of the invention, by providing a transistorized system that includes first circuit means for generating a varying voltage having at least first and second portions, the first portion having a positive polarity relative to the second portion, second circuit means connected to be responsive to the first circuit means for varying the time duration of one of the portions of the varying voltage,

and third circuit means connected to be responsive to the second circuit means and including a switching element that is controlled by the voltage output from the second circuit means. The switching element may, for example, control the flow of power from an electrical potential source to a transducer or other power consuming element. The second circuit includes means for varying the time duration of one of the portions of the voltage so that it is able to vary the power output of the system without changing the frequency of recurrence of the varying voltage. Since most or all of the above-described circuits can be transistorized, the system has other substantial advantages in that it consumes very small amounts of power and impedance matching problems are substantially eliminated.

This invention may be more completely understood from the following detailed description of a representative embodiment of the invention taken in conjunction with the accompanying figures of the drawings in which:

FIGURE 1 is a block diagram of a variable power drive system constructed in accordance with the invention;

FIGURE 2 is a schematic diagram of the system illustrated in FIGURE 1; and

FIGURE 3 is a schedule of waveforms for a portion of the system illustrated in FIGURES l and 2.

With reference to FIGURE 1, the variable power drive system includesan oscillator which generates a periodically varying voltage, an amplifier ill, a variable amplifier 12 which is provided with a manually variable power control, a driver stage 13, and an output transformer 14. The primary winding of the transformer 14 is connected in the output circuit of the driver 13 and Edi hddl its secondary winding is connected to a power consuming device (not shown). These elements are illustrated schematically in FIGURE 2. V

The oscillator 10 includes a p-n-p transistor 15 that is connected in an emitter-driven Hartley oscillator type circuit. Its tank circuit is composed of a center-tapped inductor 16, that is connected in parallel with a capacitor ii', the values of which are set in accordance with the frequency desired. The feed-back for the circuit is provided by a capacitor 18 that is connected between the hot terminal of the tank circuit and the base electrode of the transistor 15. The operating point of the oscillator circuit is stabilized and the waveform regulated by I a resistor 19 that is connected in the emitter circuit of the transistor 5.

The output of the oscillator circuit 19 is connected to the base electrode of a transistor 2%) in the amplifier 11 through a resistor 21. The resulting output waveform on the collector electrode of the transistor 20 is a short rectangular positive going pulse that has a repetition rate equal to the frequency of the oscillator it The coupling between the amplifier 11 and the variable amplifier 12 is through a variable resistor 22 and a parallel capacitor 23, and is such that a transistor 24 in the variable amplifier 1 .2 is normally saturated. In operation, the waveform obtained from the collector electrode of the transistor 2% cuts oil the transistor 2 with the result that the waveform on the collector electrode of the transistor 24 is also a rectangular pulse but has a negative polarity. The time duration of this latter negative rectangular pulse is variable and is determined by the degree of saturation into which the transistor 24- is driven, whichin turn is controlled by the setting of the variable resistor 22.

The driver circuit 13 includes a transistor 25 that has its base electrode connected to the collector electrode of the transistor 24 through a coupling circuit that includes a resistor 26 and a parallel capacitor 27. A preferred type of transistor for this stage is a diffused base p-n-p transistor which, in operation, is driven from cutoli into saturation by the output voltage from the variable amplifier 12. A DC. potential source is connected across a pair of terminals 33 and, when the transistor 25 is saturated, causes current to fiow through the primary winding 28 of the transformer 14, the transistor 25 and a resistor 36. Since the transistor 25 is being turned on and 0d, a powerful rectangular pulse appears at the winding 255.

The output stage for this system includes the primary winding 2? and the secondary winding 29 which are wound on a core 3% of magnetic material. A resistor 31 and a capacitor 32 are connected in parallel with the primary winding 28 to make a tuned circuit. A tran ducer 3'. is connected during operation across the secondary winding 29 and the DC. potential source connected to the terminals 33 provides the necessary operating potentials for the transistor circuits 1%, l1 and 12.

The variable power drive system described may be connected to drive an ultrasonic generator. If large quantities of power are required, a bank of these systems can be coupled in parallel on thecore 34 of the transformer l4, and the secondary winding 29 can be coupled to a m agnetos-trictive element in the ultrasonic generator. The elements in the oscillator circuit 16 are preferably Patentedfiec. it 19:33

set so that they frequency of oscillation is equal to the resonant frequency of the magnetostrictive element, and the tuned circuit composed of the winding 23, the resistor 31, and the capacitor 32 is also set at this frequency. During operation the varying voltage generated by the oscillator it? alternately drives the transistor 25 from. cut-oil to saturation and causes current to flow in the secondary winding 29 of the transformer 14. This current flows through a winding that is inductively coupled with the magnetostrictive element in the ultrasonic generator and causes this element to expand and contract at the frequency of the oscillator.

The power output of the transducer is varied by changing the amount of time that current flows through the secondary winding 29. This is done by varying the time duration or the width of the portion of the voltage that drives the transistor 25 into saturation. This is best illustrated by the schedule of Waveforms shown in FIG- URE 3. When the variable control resistor 22. is set at a low resistance value, the Waveform appearing at the collector electrode of the transistor 25 is represented by the waveform (a), FIGURE 3, and the positive going portion has a relatively short width or time duration. When the control resistor 22 is set at o. relatively high value, the positive going portion of the voltage appearing on the collector of this transistor, represented by the waveform (b), has a greater width. The voltages appearing at the secondary winding terminals 23 when the variable resistor 22 is at relatively low and high values are represented by the waveforms (c) and (01), respectively. An important feature to be noted here is that the negative going portions of the waveforms (a) and (b) have relatively constant peak values irrespective of the setting of the control resistor Z2, and that the frequency remains the same regardless of the setting. These waveforms have a powerful and fast positive rise time which is necessary to cut on: the driver stage 13 and at the same time ensures a full saturating voltage during the conduction of the driver stage.

If a bank of these systems is being used to drive a single transducer, they can also be connected in parallel by providing each system with a separate transformer 14 and connecting the outputs in parallel at the transducer. Regardless of how the systems are connected to the transducer, all of the oscillators will have to be coupled together in such a manner that they will oscillate in phase.

While a representative embodiment of the present invention has been shown and described for purposes of illustration, it is apparent that the embodiment is susceptible of change and modification without departing from this invention in its broader aspects. Therefore, the invention described herein is not to be construed as limited to the specific embodiment described but is intended to encompass all modifications thereof coming within the scope of the follovn'ng claims.

I claim:

1. A variable power drive system comprising oscillator circuit means for generating a cyclically varying voltage having at least first and second portions in each cycle, the first portion having a positive polarity relative to the second portion, first circuit means connected to be responsive to the oscillator circuit means for varying the time duration of one of the portions relative to the other of the portions, the first circuit means including a transistor element having a base electrode that is connected to the output of the oscillator means through a variable resistance means, said transistor being normally biased into saturation and responsive to said cyclically varying voltage to alternately switch between said saturation condition and a less conductive condition, said variable impedance I sing operative to vary the relative durations of said two conditions within each cycle of said varying voltage, and second circuit means connected to be responsive to the first circuit means and including a switching element that is adapted to be opened by one of the portions of the volt age from the first circuit means.

2. A variable power drive system comprising irst circuit means for generating a varying voltage having at least first and second portions, the first portion having a positive polarity relative to the second portion; second circuit rs 'respon sive to the hrs-t circuit means for vary ing the time duration of one of the portions relative to the other of the portions, the second circuit means including a first transistor having base, collector, and emitter electrodes and its base electrode connected through a variable resistor means to the output of the first circuit means, said first transistor being normally biased into saturation and responsive to said varying voltage to switch between said saturation condition and a less conductive condition, said variable impedance being operative to vary the relative durations of said two conditions, and third circuit means including a second transistor having base, collector, and emitter electrodes and its base electrode connected to be responsive to the output voltage from the second circuit means; and the emitter and collector electrodes of the second transistor being adapted to be connected in series with a power consuming device and a source of electric potential.

3. A generator system comprising first circuit means for generating a regularly varying voltage having at least first and second portions, the first portion having a positive polarity relative to the second portion; second circuit means connected to be responsive to the first circuit means for varying the time duration of one of the portions of the varying voltage, the second circuit means including a first transistor having base, collector, and emitter electrodes and its base electrode connected through a variable resistor and capacitor parallel combination to be responsive to the output voltage fromthe first circuit means; third circuit means connected to be responsive to the second circuit means and including a second transistor having base, collector, and emitter electrodes and its base electrode connected to the output of the second circuit means; a Winding and a source of electric potential connected in series with the collector and emitter electrodes of the second transducer, and a transducer having a magnetostrictive element inductively coupled with the winding.

4. in a variable power generator system for driving a magnetostrictive element, a source of periodic pulses, a transistor having emitter, base and collector electrodes and norm-ally biased into saturation, variable impedance means coupling said periodic pulse source to the base electrode of said transistor to alternately switch said transistor between saturation and cut-cit conditions in synchron-ism with said pulses, said variable impedance eing operative to vary the duration of said saturation condition with respect to said cut-oil condition of said transistor within each cycle of operation thereof, and means to derive an output from said transistor.

5. The invention of claim 4 above wherein said variable impedance comprises adjustable resistance element.

6. A circuit arrangement for providing controllable amounts of power to a load in regular recurring fashion comprising, a source of regularly recurring pulses of relatively low power, a transistor having emitter, base, and collector electrodes and normally biased into saturation, variable impedance means coupling said pulse source to the base elect ode of said transistor to switch said transistor rallternately between saturation and cut-oli in synchronism with said pulses, said variable impedance means being operative to vary the relative durations of said saturation and cu t-oi? conditions within each recurring cycle or" operation thereof, a relatively high power transistor amplifier, means coupling the output of said transistor to the input of said amplifier, and means coupling the output of said amplifier to said load.

7. A c cuit arrangement for providing controllable amounts of powe to load in re u lar recurring fashion comprising, a source of cyclically varying voltage, a transistor having emitter, base and collector electrodes and norm-ally biased into a saturation condition, variable im- 5 pedance means coupling s aid cyclically varying voltage to the base eleotrode of said transistot to alternately switch said transistor between said saturation condition and a less lCOHdUJO'lIlV6 condition in sychronisun with said cyclically vaa'yving voltage, said variable impedance means being operative to vary the duration of said saturation condition with mespeot to said less conductive condition of said transistor within each cyole of openation thereof, and means to couple the output of said transistor -00 said load.

References Cited in the file of this patent UNITED STATES PATENTS Jaeschke Oct. 13, Dickenson Oct. 8, Henle Nov. 18, Walsh Nov. 18, Clapper Dec. 9, Carlin Sept. 6,

Robinson May 1,

Claims

3. A GENERATOR SYSTEM COMPRISING FIRST CIRCUIT MEANS FOR GENERATING A REGULARLY VARYING VOLTAGE HAVING AT LEAST FIRST AND SECOND PORTIONS, THE FIRST PORTION HAVING A POSITIVE POLARITY RELATIVE TO THE SECOND PORTION; SECOND CIRCUIT MEANS CONNECTED TO BE RESPONSIVE TO THE FIRST CIRCUIT MEANS FOR VARYING THE TIME DURATION OF ONE OF THE PORTIONS OF THE VARYING VOLTAGE, THE SECOND CIRCUIT MEANS INCLUDING A FIRST TRANSISTOR HAVING BASE, COLLECTOR, AND EMITTER ELECTRODES AND ITS BASE ELECTRODE CONNECTED THROUGH A VARIABLE RESISTOR AND CAPACITOR PARALLEL COMBINATION TO BE RESPONSIVE TO THE OUTPUT VOLTAGE FROM THE FIRST CIRCUIT MEANS; THIRD CIRCUIT MEANS CONNECTED TO BE RESPONSIVE TO THE SECOND CIRCUIT MEANS AND INCLUDING A SECOND TRANSISTOR HAVING BASE, COLLECTOR, AND EMITTER ELECTRODES AND ITS BASE ELECTRODE CONNECTED TO THE OUTPUT OF THE SECOND CIRCUIT MEANS; A WINDING AND A SOURCE OF ELECTRIC POTENTIAL CONNECTED IN SERIES WITH THE COLLECTOR AND EMITTER ELECTRODES OF THE SECOND TRANSDUCER, AND A TRANSDUCER HAVING A MAGNETOSTRICTIVE ELEMENT INDUCTIVELY COUPLED WITH THE WINDING.