US2427687A - Pulse control system - Google Patents

Description

Sept. 23, 1947.

D. E. NORGAARD 2, PULSE CONTROL SYSTEM Filed Dec. 9, 1942 "Fig. l-.

ALTERNATING Q CURRENT UTILIZATION To SOURCE CIRCUIT OF VARIABLE UNIDIRECTIONAL CONTROL POTE/fT/AL T0 SOURCE L 0F ALTERNATl/VG REFERENCE POTENTIAL [4 Pg 2 REFERENCE POTEO/T/AL o/v TIME ,2 v z POTENTIAL K 5+ (AT POINT 4 CONSTA NT POTENT/A L AT POINT 5 5+ /POTENT/AL CURVE OF POTEN TIA L 0 AT POINT 5 TIME /3 POTENTIAL 5+ AT POINT 4 CURVE 0F POTENTIAL AT POINT 5 Inventor: ,Dor'wald E3. Norgaard,

b' WWI MM His Attorney.

Patented Sept. 23, 1947 PULSE CONTROL SYSTEM Donald E. Norgaard, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application December 9, 1942, Serial No. 468,406

Claims. 1

My invention relates to systems for generating and controlling alternating current signals, particularly to systems for supplying to a suitable utilization circuit alternating current signals whose polarity and amplitude vary correspondingly with a direct current input control potential, and the object of the invention is to provide a simple and improved system which operates especially efiiciently in supplying, to an output circuit, square waves of low and medium frequency and any desired percentage of width, and wherein no current drain is required from the source of direct control potential.

In accordance with the present invention this object is attained by the provision of a translation circuit comprising means, the components of which are all stationary, to supply alternating current to an output circuit having the frequency of a reference alternating input potential, and means included in the translation circuit to reverse the phase of the output current in response to the magnitude of a control unidirectional input potential. The translation circuit includes an electron discharge device upon the control electrode of which the unidirectional control potential is impressed and in the anode-cathode circuit of which a potentiometer is included, a second electron discharge device being provided for determining the periods of operation of the first discharge device, thereby to initiate pulses in its anode-cathode circuit. Upon the control electrode of the second discharge device potentials are impressed from the source of alternating reference potential, and a portion of the potentiometer is included in the anode-cathode circuit of the second discharge device.

The novel features which are considered to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawing wherein Fig. l is a diagrammatic representation of a circuit embodying the invention; Fig. 2 shows a curve representing the alternating reference potential; and Fig. 3 shows curves of output alternating potential obtained from the system and corresponding to a range of values and polarities of the unidirectional input control potential, for example, to zero input potential or to a given positive or negative potential value.

In Fig. 1 a translation circuit in accordance with my invention is shown comprising electron discharge devices, designated V1 and V2, arranged to be supplied with anode current from a common source (not shown), the anode-cathode circuits of the discharge devices including a common cathode resistor I. A source (not shown) of variable uni-direction control potential is connected to the control electrode-cathode circuit of discharge device V1 and a source (not shown) of alternating reference potential is connected to the control electrode-cathode circuit of discharge device V2 through a capacitor 2. The anodecathode or output circuit of device V1 includes, in series therein, a potentiometer 3 or equivalent impedance element to the opposite terminals 4 and 5 of which any suitable alternating current utilization circuit (not shown) may be connected through a capacitor 6.

The system in accordance with my invention may be utilized, for example, for controlling, in response to the amplitude and polarity of the unidirectional potential supplied to discharge device V1, the speed and direction of rotation of a motor. However, various other utilization circuits may be employed in connection with the system, and controlled in response to the unidirectional potential.

For a purpose to be explained hereinafter, a portion of the potentiometer 3 is connected in series in the anode-cathode circuit of device V2 by connecting the latter circuit to the potentiometer at a given point, as 1. One section, as 8, of the potentiometer is therefore included in the anode-cathode or output circuit of device V2 and both sections, 8 and 9, are included in the anode-cathode or output circuit of device V1. A leak resistor 10 is preferably provided connected across the control electrode-cathode circuit of discharge device V2.

The alternating potential which is impressed upon the control electrode of discharge device V2 from the source of reference potential is preferably square wave in form as shown in Fig. 2 and is of the frequency which is desired in the utilization circuit connected to the system. The amplitude of the square wave reference potential is preferably such that during the negative peaks thereof electron discharge device V2 is cut oil, and during the positive peaks V2 draws control electrode current. Electron discharge devices V1 and V2 are so arranged and common cathode resistor I has such resistance value that the action of device V2, on the negative and the positive peaks respectively of the reference potential, is, alternately, first, to permit V1 to draw anode current through potentiometer 3 in accordance with the unidirectional input control potential, and, second, to bias device V1 to cutoff regardless of the amplitude and polarity of the unidirectional control potential applied to its control electrode.

The common cathode resistor l is preferably of such resistance value as to provide correct Class A operation of discharge device V1 when the input control potential is zero. It is desirable also that the input control potential impressed upon the control electrode of discharge device V1 be limited to a range which insures a suitable amount of linearity between anode current and control electrode potential in that portion of the operating cycle during which device V1 is drawing anode current.

The arrangement of the potentiometer 3 and discharge device V2 is thus such that the anode current drawn by the latter discharge device is permitted to flow through a portion, as 8, of the potentiometer during the positive peaks of the square wave reference potential. By suitable selection of the point at which the anode of device V2 is tapped into the potentiometer, the out put alternating potential of the system may be made zero for any chosen value of the unidirectional input control potential impressed upon device V1. For usual operation of the system it is desirable that normal adjustments be such that the output alternating potential is zero when the unidirectional input control potential is zero.

Operation of the system will be better understood by reference to Fig. 3 considered in connection with Figs. 1 and 2.

Referring, rst, particularly to Fig. 3(a) which illustrates the case of Zero unidirectional input potential and zero alternating output potential, designating the anode-cathode current of electron discharge devices V1 and V2 respectively as IPv1 and IPv2 and the resistance value of poten tiometer sections 8 and 9 respectively as He and R9, let it be assumed that the unidirectional control potential on the control electrode circuit of discharge device V1 is zero and that the output alternating potential of the system is also to be made zero. Then, when the square wave reference potential impressed upon the control electrode of discharge device V2 is at its negative peak value as designated by portion ll of curve l2, Fig. 2, the latter discharge device is out off, no anode current from device V2 flows in the common cathode resistor and therefore electron discharge device V1 is not biased to cut-01f but draws, through both potentiometer sections and 1 9 in series, the normal current which corresponds to zero value of the unidirectional input potential.

Under these conditions the potential drop b tween point 5, the potential of which is represented by the line 13 of Fig. 3(a) point 4 which in the arrangement illustrated in Fig. 1 is at the potential of the positive terminal of the anode supply source, is (IP01) (Ra-l-Rs).

When, next, the square wave reference potential changes from its negative to its positive peak value as designated by portion IA of curve 12, Fig. 2, the electron discharge device V2 then becomes conductive, its anode current flows in the common cathode resistor I, and electron discharge device V1 becomes biased to cut-off. Under these conditions, although V1 is out off and no current flows in section 9 of potentiometer 3, a flow of current occurs in the potentiometer section 8 which is included in the anode-cathode circuit of V2. Electron discharge devices V1 and V2 are so selected and arranged, V2 being preferably a device of higher rating than V1, and the section 8 of potentiometer 3 determined by the point 1, at which the anode of V2 is tapped therein is caused to be of such resistance value, that the potential drop (IPv2) (R2) across the section 3 is made substantially equal to the before-mentioned potential drop (IPv1) (RM-Rs), across the entire potentiometer 3, which was the drop obtained when the square wave reference potential was at its negative peak.

Since, when device V2 is conducting but de vice V1 is cut off and no current flows in potentiometer section 9, the potential across section 8, or between points 4 and I, is substantially that across both sections 8 and 9, or between points 4 and 5, therefore, under the condition of positive peak value of the square wave reference potential impressed upon the control electrode circuit of V2, the potential of point 5, represented by the line l5 of Fig. 3(a), remains substantially the same as represented by line l3.

Therefore when the unidirectional input con trol potential is zero and the potential drop through the potentiometer 3 and its section 8 is equalized for both negative and positive peaks of the square wave reference potential by suitable selection of the tapping point 1, no alternating component appears in the potentiometer potential across points 4 and 5 and the potential of the alternating utilization circuit is zero.

Referring, secondly, particularly to Fig. 3(b) which illustrates the case of a positive unidirectional input control potential ,assuming the same values as before for IPv1, IPv2, R8 and R9 and the same characteristics for the square wave reference potential 12, Fig. 2, impressed upon the input circuit of device V2, let it be assumed that the unidirectional control potential supplied to the control electrode circuit of V1 is changed from Zero to a given positive potential. Then when the square wave reference potential impressed upon the control electrode circuit of V2 is at its negative peak value the electron discharge device V2 is as before cut oif and the tube V1 is conducting. But since the unidirectional control potential has been changed in the positive direction from zero to a given substantial value, the anode current of V1 is increased during the conducting period and the potential drop in potentiometer 3 correspondingly increases, the potential of point 5 in Fig. 3(b) being represented for example by the line 16 of the latter figure.

When, however, the square wave reference potential impressed upon the input circuit of V2 changes to its positive peak value, then, as before, V2 becomes conductive, V1 is out off, and the potential drop across the section 8 of potentiometer 3 remains at its previously assumed value, (IP22) (R8). The potential of point 5 represented by the line H of Fig. 3 (1)) thus remains the same as in the case of zero input control potential illustrated in Fig. 3 (a).

Therefore, as represented by curve l8 of Fig. 3 (b) when, in the system originally adjusted for zero unidirectional input control potential and zero alternating output potential, the input unidirectional control potential is adjusted to a suitable positive value, an alternating utilization potential is produced having the same frequency as that of the alternating reference potential.

Referring, thirdly, particularly to Fig. 3 (c) which illustrates the case of a negative unidirectional input control potential, assuming the same circuit characteristics in general as for the cases illustrated in Figs. 3(a) and 30)), when the unidirectional control potential impressed upon the input circuit of V1 is made negative then the anode current of V1 during the conducting period is decreased instead of increased relatively to its value when the unidirectional control potential was zero. The potential drop in potentiometer 3 is correspondingly decreased, the potential of point 5 being represented by the line 19 of Fig. 3(c). However, during the period, corresponding to the positive peak M of the reference potential, when V1 is cut off and V2 is conducting, the potential drop across section 8 of potentiometer 3 remains again at its previously assumed value (IP02) (R8) and the potential of point 5, represented by the line 20 of Fig. 3 again remains the same as in the zero input control potential case illustrated in Fig. 3 (it).

Therefore, as represented by curve 2! of Fig. 3 (c) when in the system wherein the unidirectional input and the alternating output were both zero, the unidirectional input control potential, is given a. negative value, an alternating utilization circuit potential is produced having the same frequncy as that of the reference potential and opposite in phase to that of the utilization circuit potential produced when the unidirectional input control potential had a positive value.

In the arrangement of my invention illustrated in Fig. 1 the utilization circuit is described as connected directly across the potentiometer 3, the output potential being in phase with the reference potential for positive values of the unidirectional control potential and in opposite phase for negative values of the control potential. Other connection arrangements may be made, however. For example, the utilization circuit may be connected across point 5 and ground instead of across point 5 and point 4, which is at the potential of the anode current source.

While not entirely essential, because of nonlinearity of electron discharge devices it is highly desirable in a system in accordance with my present invention that, as hereinbeiore set forth square waves be employed as reference potential, since no Waveform distortion is produced by nonlinear circuit elements when the system is operating on square waves. The reference potential may be constituted by square waves of any suitable frequency and of any desired pulse width.

In a typical system in accordance with my present invention circuit elements and constants may be substantially as follows:

Resistor l-2000 ohms Resistor I0-1 megohm Potentiometer 310,000 ohms Discharge device V1- /q of type 6SL'7GT Discharge device V2 of type GSN'TGT Unidirectional input potential-+2 to 2 volts Alternating reference potential-Square topped waves, 30 volts minimum (peak to peak) Alternating output potential-+10 to 10 volts (peak to peak) Capacitor 2-Depends on frequency of alternating potential Capacitor 6--Depends on frequency Of alternating potential My invention has been described herein in particular embodiments for purposes of illustration. It is to be understood, however, that the invention is susceptible of various changes and modifications and that by the appended claims I intend to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

i. In combination, an electron discharge device having an output circuit including an impedance and an input circuit adapted to have a unidirectional potential impressed thereon, a second electron discharge device having an output circuit including a portion of said impedance an input circuit adapted. to have an alterhating reference potential impressed thereon, and means including said second-named discharge device for causing said first-named discharge device to become alternately conducting and non-conducting in response to said reference potential, whereby an alternating current component is produced in said first-named output circuit.

2. In combination, an electron discharge device having an output circuit including an impedance, a second electron dischage device having an output circuit including a portion of said impedance and an input circuit adapted to have an alternating reference potential impressed thereon, a common bias means included in said output circuits, and means including said second-named discharge device and said bias means for causing said first-named discharge device to become alternately conducting and non-conducting in response to said reference potential.

3. In combination, a first and a second electron discharge device each having a control electrode, an anode and a cathode, a source of operating potential, a common cathode resistor for said discharge devices connected between the negative terminal of said source and said cathodes, a potentiometer included in series with said source and the anode-cathode circuit of said first device, means to include a portion of said potentiometer in series in the anode-cathode circuit of said second device, a source of variable unidirectional control potential connected to the control electrode-cathode circuit of said first device, and a source of alternating reference potential connected to the control electrode-cathode circuit of said second device whereby alternating potential having the frequency of said reference potential is produced across said potentiometer having one phase or the opposite phase dependent upon the value of said variable unidirectional potential.

4. In combination, a source of variable steady unidirectional control potential, a source of alternating reference potential, a utilization circult, and means for producing in said circuit an alternating potential of the "frequency of said reference potential and of amplitude and phase determined in accordance with said control potential, said means including an electron discharge means having an output impedance connected to said utilization circuit, means including a second electron discharge means for determining the conducting periods of said firstnamed discharge means in response to said reference potential, said second electron discharge means being in series with a portion of said output impedance to determine the potential thereon when said first device is nonconducting, and means to control said first-named discharge means during said periods in accordance with said control potential.

5. In combination, an impedance, a source of variable unidirectional electromotive force, means to produce across said impedance an al- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number ance and to interrupt said unidirectional current 10 2,253,307

during said pulses.

DONALD E. NORGAARD.

Name Date Lewis Oct. 5, 1940 Blumlein Dec. 16, 1941 Richter Aug. 19, 1941 I-Iyland May 2, 1939

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