US2621321A - Voltage regulator - Google Patents

Description

Dec. 9, 1952 w. .1. HOLT, JR

VOLTAGE REGULATOR Filed March 18, 1950 INVENTOR.

WILLI M J. O T JR.

. ATTORNEY Patented Dec. 9, 1952 UNITED STATES iia'i'ENT OFFICE 3 Claims.

My invention relates to voltage regulators and more particularly to voltage regulators employing electric valves or electric discharge devices.

In many applications it is necessary to maintain a very precise constant direct current voltage across a load. In some applications the allowable voltage variation is less than three hundredths of one per cent of the normal voltage. Voltage regulators of the type in which the resistance of a first electric discharge device connected between the rectifier and the load is varied to maintain the voltage across the load constant are well known in the art. The resistance of the first electric discharge device connected between the rectifier and the load is varied to maintain the voltage across the load constant are well known :in the art. The resistance of the first electric discharge device is usually varied in accordance with the voltage across the load by means of a second electric discharge device connected across the load. The variations in the plate voltage of the latter device are amplified and impressed on the control member of the first electric discharge device. It is found that variations in the temperature of the cathode due to the changes in the heating current of the cathode or of the heating element of the cathode of the second electric discharge device introduce variations in the plate voltage of the second electric discharge means which result in variations in the voltage across the load which exceed the allowable limits. It is desirable, therefore, that the changes in the temperature of the cathode of the second discharge device be compensated by the voltage regulator circuit in order to maintain substantially constant voltage across the load.

Accordingly it is an object of my invention to provide a new and improved electric regulating apparatus.

It is another object of my invention to provide a new and improved electric regulating apparatus which maintains the voltage of a direct current load circuit substantially constant.

It is still another object of my invention to provide a new and improved voltage regulating means which compensates for the variations in temperature of the cathode of a voltage controlling electric discharge device.

Briefly stated, in the illustrated embodiment of my invention I provide a voltage regulating apparatus for energizing a load circuit from a direct current source through an electric discharge device of the high vacuum type. A second electric discharge device controls the conductivity of the first electric discharge device. In order to compensate for the variations in the conductivity of the second electric discharge device due to changes in the temperature of its cathode, I provide a third electric discharge device Whose cathode temperature varies in the same manner as the cathode temperature of the second electric discharge means and which is employed to Vary the conductivity of the second electric discharge means in accordance with the changes in the cathode temperature of the second electric discharge device.

For a better understanding of my invention, reference may be had to the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims. The single figure of the drawing illustrates diagrammatically a preferred embodiment of my invention as applied for controlling the voltage of a direct current load circuit energized from a direct current supply circuit.

Referring now to the single figure of the draw ing, I have diagrammatically illustrated my invention as applied to a voltage regulating apparatus for energizing a direct current load circuit I from a suitable source of direct current, for example the rectifier 2. Rectifier 2 comprises a secondary winding 3 of a transformer 4 whose primary winding 5 is connected to any suitable source of alternating current 6. The secondary winding 3 has its opposite ends connected to one side of load circuit I through a pair or" electric valves 1 and 8, a filter network 9 and an electric discharge means I9. The electrical midpoint ll of secondary winding 3 is connected to the other side of load circuit I through a pair of serially connected resistances l2 and 13. Electric valves 1 and 8 each comprise an anode I4, a cathode 15, a screen grid l6 connected to cathode it, a control grid I! and a heating element l8 and may be of any of the several types Well known in the art although I prefer to utilize electric valves of the gaseous discharge type.

In order to prevent conduction of current by electric valves 7 and 8 upon initiation of opera tion until the cathodes reach their proper operating temperature, I provide a time delay circuit IQ for delaying the application of potentials to control grids l 6 of such polarities as to render electric valves 7 and 8 conductive until heating elements l8 bring the cathodes 15 to their operating temperatures. Control grids l? of electric valves 1 and B are connected through current limiting resistances 29 and 2|, respectively, to opposite ends of the secondary winding 22 of a transformer 23. The electrical midpoint 24 of winding 22 is connected to cathodes I5. The primary winding of transformer 23 has one end 25 connected through a resistance 21 to one end 28 of a secondary winding 2-: on transformer The other end 36 of winding 25 is connected to end 28 of winding 29 through contact 35 of a thermal time delay relay 32 when contact BI is in its actuated position. The electrical midpoint 33 of Winding 25 is connected directly to end 35 of winding 25 and is connected to end 28 through the heating resistance 35 of time delay relay 32. Heating elements I3 of electric valves I and 8 are connected in parallel across secondary winding 36.

If we assume now that switch 31 is closed, heating elements I8 of electric valves I and 8 will be immediately energized and will begin to rise in temperature. The temperature of cathodes I8 will therefore begin tov rise. Simultaneously, alternating voltages of opposite polarities will be applied to anodes I4 of electric valves I and 8 but valves I and 8 will not conduct current since the alternating potentials on control grids I! will be of such polarities as to prevent conduction. The polarities of the potentials applied to control grids I'I, whether in-phase or out-of-phase with respect to the polarities of the voltages applied to anodes III, are determined by the position of contact 3I of timedelay relay r;

32. When time delay circuit is initially energized by the alternating current of winding 29, alternating current will flow through the portion of the winding 23 which lies between electrical midpoint 33 and end 26. The alternating voltages induced in winding 22 during this period are applied to control grids I7 but are of such polarities that electric valves I and 8 are prevented from conducting current to load circuit I. For example, during the half cycle of the alternating current in which a positive voltage is applied to anode I4 of electric valve I, a negative potential is impressed on control grid ll of valve I. At the same time a positive potential is applied to the control grid of electric valve 8 but a negative voltage is applied to its anode I4 so electric valve 8 also is non-conductive. During the succeeding half cycle, a positive voltage is applied to anode I4 of valve 8 but the potential applied to its control grid I1 is now negative.

Neither half cycle of the alternating current is therefore transmitted to load circuit I.

Resistance 35 of relay 32 is connected across winding 29 so that current flows through resistance 35 as soon as switch 37 is closed. After a predetermined period of time, resistance 35 is heated to such an extent that the bimetallic contact 3I, whose temperature varies in accordance with the temperature of resistance 35, bends and connects end of winding 25 to end 28 of winding 29. The portion of winding 25 between electrical midpoint 33 and-end '30 is therefore connected across winding 29. The portion of winding 25 between electrical midpoint 33 and end 25 is still connected across winding 29 but since it has resistance 21 connected in its circuit, the current which the current flowing in the latter portion of winding 25 tends to induce in winding 22 is less than the current induced in winding 22 by the portion of winding 23 between electrical midpoint 33 and end 39. Since the current in this portion of winding 23 flows at any one moment in opposite direction to current flowing in the other portion of winding 25, the polarities of the potentials impressed on control grids I! are now reversed. A positive potential is impressed on each control grid I'I when a positive voltage is applied to the anode I4 of its electric valve I or 8. Electric valves 1 and 8 therefore are rendered alternately conductive and transmit a pulsating unidirectional current to filter network 9. Resistance heater remains connected across winding 29 at all times and wil1 maintain contact 3| in its actuated position until switch 3'! is opened.

The filter network 9 may be of any conventional design and may comprise inductances 31 and 33 and capacitances 39 and 40. Filter network 9 smoothes out the pulsating unidirectional current transmitted from the common cathode I5 circuit of electric valves I and 8 and conducts it to the control electric discharge device IO. Electric discharge device I0 comprises an anode 4| connected to cathodes I5 through network 9, a cathode 42 connected to load circuit I, a control grid 43 and a heating element 44. Electric discharge device I9 may be of any of the several types well known in the art although I prefer toutilize an electric discharge device of the high vacuum type. By varying the potential applied to control grid 43, in accord ance with the voltage of load circuit I, the conductivity of electric discharge device II) is also varied in accordance with the voltage of load circuit I in such a fashion as to maintain the voltage of load circuit I constant.

The control circuit for electric discharge device IQ includes a voltage divider comprising resistance 45 and serially connected resistances 45, 41 and 48 which are connected across the output circuit I. resistance 45 through an adjustable contact 49 while the end of resistance 48 not connected to resistance 41 is connected to the common junction or connection 50 of resistances I2 and I3. Resistance 41 is connected to the control grid 5I of an electric discharge means 52 through an adjustable contact 53 on resistance 41. Electric discharge means 52 is preferably of the high vacuum type and comprises an anode 54, a cathode 55, and a heating element 55. In order to maintain cathode 55 at a constant potential, I provide a voltage divider bridge which comprises resistances 5I and 58 and a glow discharge means 59 connected in series across load circuit I. The common junction or connection 60 of resistance 58 and glow discharge means 59 is connected to cathode 55 of electric valve 52. The glow discharge device 59 furnishes a substantially constant voltage due to its non-linear current-int pedance characteristics. To assist the glow discharge means 59 in maintaining cathode 55 at a substantially constant potential, a capacitance GI is connected across glow discharge means 59.

Electric discharge device 52 amplifies the variations impressed on its control grid 5|. In order to further amplify the variations in potential impressed on control grid 5 I, the anode 54 of electric discharge device 52 is connected through a resistance 62 to the cathode 63 of an electric discharge device 64. Electric discharge device 64 also comprises an anode 65, a control grid 66 connected to the common junction or connection 57 of anode 54 and resistance 62, and a heating element 68. Cathode '63 is also connected to the common junction or connection 69 of resist- 58 has a relatively low impedance as compared to the impedance of resistance 62 and electric Resistance 46 is connected to discharge device 52. The anode 65 is connected to one side of load circuit I through a resistance I0.

In order to still further amplify the variations in voltage impressed on control grid SI of electric discharge device 52, I provide an electric discharge device II, preferably of the high vacuum type, which comprises an anode I2, a cathode I3, a control grid I4 and a heating element I5. Control grid 74 is connected to the common juncture or connection I6 of serially connected resistances TI and IS. The other end of resistance 11 is connected to the common juncture or connection III of resistance Ill and anode 65 while the other end of resistance I8 is connected to the common juncture or connection 83 of resistance I2 and electrical midpoint II of secondary winding 3. Anode 12 is connected to grid 43 of electric discharge device IB and also through resistance 8I to cathode 42.

Disregarding for the moment the effect of electric discharge device 82 by treating it as an infinite resistance and assuming that switch 31 is closed, the potential impressed on control grid 43 of electric discharge device I maintains the voltage of load circuit I at a predetermined value which may be set by adjustment of adjustable contact 53 on resistance 41. If the voltage of output circuit I now tends to increase, the potential of resistance 4'! at the point at which adjustable contact 53 abuts or contacts resistance 41 becomes more positive impressing a less negative potential on control grid I of electric discharge device 52. The potential of cathode 55, however, remains substantially constant due to the voltage regulating action of glow discharge means 59. Since control grid 5| is now less negative with respect to cathode 55, electric discharge device 52 is now more conductive and more current flows through resistance 62 since it is in series with anode 54.

Since opposite ends of resistance 62 are connected to control grid 66 and cathode 63, respectively, of electric discharge device 64, the change in potential across resistance 62 due to the change in conductivity of electric discharge means 52 impresses a more negative potential on control grid 66. The potential on cathode 63 remains substantially unchanged since it is connected to common connection 69 and since the impedance of resistance 58 is relatively low when compared to the impedance of resistance 62 and electric discharge device 52. The conductivity of electric discharge device 64 will be decreased due to the more negative potential on its control grid 66 and less current will flow through resistance 10. The potential impressed on control grid I4 of electric discharge device II through resistance 11 will therefore be made more positive and electric discharge means II will be rendered more conductive. The amount of current flowing through resistance BI is therefore increased. Since opposite ends of resistance 8| are connected to control grid 43 and cathode 42, respectively, a more negative potential will be impressed on control grid 43 and the conductivity of electric discharge device I0 will be decreased and the voltage of load circuit I will be decreased. If the voltage of load circuit I tends to decrease, the opposite chain of events will occur and the conductivity of electric discharge device I6 will be increased, increasing the voltage of load circuit I.

In order to make the voltage regulating circuit responsive to very fast changes in the voltage of load circuit I, I provide capacitors 83 and 84 which are connected between cathode 42 and control grids I4 and 52, respectively and which permit the potentials impressed on control grids I4 and 52 to change rapidly with rapid changes in the voltage of load circuit.

Resistances I2 and I3 are employed to compensate for changes in the load current in load circuit I and to aid in the regulation of the voltage of load circuit I. For example, if the current in load circuit I increases, more current flows through resistances I2 and I3 and the potential difference between control grid I4 and cathode I3 becomes greater, decreasing the conductivity of electric discharge means II and increasing the conductivity of electric discharge device ID. In like manner, the increase in current flowing through resistance I3 decreases the conductivity of electric discharge device 52, increases the conductivity of electric discharge device 64, decreases the conductivity of electric discharge device II, and increases the conductivity of electric discharge device I0.

In order to provide an extremely sensitive and accurate regulation of the voltage of load circuit I, the variations in the potential impressed on control grid 5I are amplified very greatly by electric discharge devices 54, 64 and II, in one application more than three thousand times, before being applied on the control grid 43 of electric discharge device I6, Extremely small variations in the conductivity of electric discharge device 52 will therefore change appreciably the conductivity of electric discharge device I0 and cause the voltage of load circuit I to depart from its predetermined value. It will be noted that heating element 56 of electric discharge device 52 is connected across a secondary winding 85 of transformer 4. The current fiowing in heating element 56, and therefore the temperature of cathode 55, will vary in accordance with the alternating voltage across primary winding 5. Since the conductivity of electric discharge device In varies in accordance with the temperature of its cathode 55, changes in the current in filament 56 will cause variations in the voltage of load circuit I. The changes in conductivity of electric discharge device 52 caused by changes in the current in heating element 56 with changes in the voltage across primary winding 5 tend to decrease the voltage of load circuit I upon an increase in the voltage across winding 5 and vice versa. The changes in the conductivity of electric discharge device 52 due to changes in the current in heatin element 56, however, cause the voltage of load circuit I to depart appreciably from its predetermined value since the potential on control grid El is set to vary the conductivity of electric discharge device III in order to maintain the voltage of load circuit I at a predetermined constant value. In one application, it was found that the voltage of load circuit I was caused to fall below the predetermined value as the voltage across primary winding 5 and the current in heating element 56 increased. It is necessary, therefore, to compensate for the variations in the conductivity of electric discharge device 5I caused by changes in the current in heating element 56.

In order to provide this compensation, electric discharge device 82 is connected across load circuit I in series with resistances 45 and 86. Electric discharge device 52 is of the high vacuum type and comprises an anode 87 connected to one side of load circuit I through resistance 45, a cathode 88 connected to the other side of load circuit I through resistance '86, a control grid 89 connected to the other side of load circuit I, and -,a heating element 90 which is connected in parallel with heating element '56 across secondary winding 85. Resistance '86 is employed to maintain a substantially constant bias potential on grid- 89. The conductivity of electric discharge means 82 will therefore depend primarily onthe variations in the current in heating element 9'0. Since heating elements 56and 90 are connected in parallel, the current in heating element 90, and therefore the conductivity of electric discharge device 82, varies in accordance with the current in heating element 56 and the com ductivity of electric discharge device 52,

Control grid of electric discharge device 52 is connected through adjustable contact 53, resistances 47 and 46, and adjustable contact 49 to resistance 45. Variations in the conductivity of electric discharge-device 82 will therefore cause variations in the potential impressed on' control grid 5| which will maintain the conductivity of electric discharge device 52 constant regardless of the variations in the current in heating element 55; For example, if the current in heating element 55 increases and the conductivity of electric discharge device 5| tends'toincrease, the current in heating element 90 also increases increasing the conductivity of electric discharge device 82 and causing more current to flow through resistance 45; A more negative potential is therefore impressed on control grid 5| which tends to decrease the conductivity of electric discharge device 52. By adjusting the position of adjustable contact 49 on resistance 45, the changes in the potential on control grid 45 can be set .to exactly compensate for the changes in conductivity of electric discharge device It due tochanges in the current in heating element 55. Theconductivity of electric discharge device 52 will therefore vary only with the variations in the voltage across load circuit l.

Electric discharge devices 52 and 82 are preferably contained in a single envelope so that the temperatures of cathodes 55 and 88'will be equal at all times. If discharge devices 55 and 88 are in, individual envelopes and are separated,- one discharge device, say device 55, maybe in a better ventilated or cooler locationthan the other discharge device 88 and its cathode 55 will thereiore be at a lower temperature than cathode 88 even though the currents in heating elements 56 and 90 are equal. Use of a singe envelope precludes disparities in the temperatures of oath-- odes 55'and 88.

I It will be noted that heating elements and 68 of electric discharge devices 11 and 64 are also connected in parallel across secondary winding 85. It will be apparent that changes in the conductivity of electric discharge device H due to changes in the temperature of its cathode 13 will be compensated by changes in the conductivity of electric discharge device 64 due to similar changes in the temperature of its cathode 63; Electric discharge devices 64 and H are also contained in a single envelope, I

While I have shown and described my inventionas applied to a particular system of connections and as embodying various devices di agrammatically shown, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my inven- 'tion,,and I, therefore, aim in the appended claims to cover all such changes and, modifications as (ill 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:

V 1. In combination: a direct current supply circult; a load circuit; an electric discharge device connected in series between said supply and load circuits, said first electric discharge means'in eluding a pair 'of principal electrodes and a con-'- trol grid; a voltage divider connected across said load circuit; a second electric discharge device having an anode, a cathode and a control grid; a-resista'n'ce connected in with anode and to one side cfsaid load circuit; a second voltage divider including a resistance'and a glow dischargedevice connected across said output circuit, said glow discharge means being connected with said cathode and the other side of said output circuit, means connecting said control grid of said second electric discharge means to an intermediate point of said voltage divider; a third electric discharge device having an anode and a cathode connected in series with a resistance across a portion of said voltage divider, said second and third electric discharge devices having cathode heaters connected to the same source of heater current; and means connecting the anode of second electric discharge device to the control grid of said first electric discharge device.

2. The device of claim 1 characterized in that said last mentioned means includes amplifying means for ampliiying the variations in the voltage of said anode and impressing them on said control grid of said first electric discharge device.

3. In combination: a direct current supply circuit; a load circuit; an electric discharge device connected in series between said supply and load circuits, said first electric discharge means including a pair of principal electrodes and a con-' trol grid; a voltage divider connected across said load circuit; a second electric discharge device having an anode, a cathode and a control grid;

a resistance connected in with said anode and to one side of said load circuit; a second voltage divider including a resistance and a glow discharge device connected across said output circuit, said glow discharge means being connected with said cathode and the other side of said output, circuit, means connecting said control grid of said second eiectric discharge means to an intermediate point of said voltage divider; a third electric discharge device having an anode and a cathode connected in series with a resistance across a portion of said voitage divider, said second and third electric discharge devices hav-'- ing cathode heaters connected to the same source of heater current; a fourth electric discharge device having an anode, a cathode and a control grid; a resistance connected with the anode of said fourth electric discharge means and to said one side of said output circuit, the cathode of said fourth electric discharge device being connected to the other side of said output circuit through said glow discharge means; a fifth electric discharge means having an anode, a cathode and a control grid; a resistance connected with the anode of said fifth electric discharge means and to said one side of said output circuit, said cathode of said fifth electric discharge means being connected to the other side of said output circuit through said glow discharge means; a third voltage divider comprising a resistance connected in se has with said resistance connected ,with the anode of said fourth electric discharge means, said third voltage divider being connected across said output circuit; means connecting said control grid of said fifth electric discharge means to an intermediate point of said third voltage divider; said fourth and fifth electric discharge 5 devices having cathode heaters connected to the same source of heater current; and means connecting the anode of said fifth electric discharge means to the control grid of said first electric discharge device.

WILLIAM J. HOLT, JR.

REFERENCES CITED The following references are of record in the file of this patent:

Number Number 10 UNITED STATES PATENTS Name Date Hansell Feb. 9, 1943 Lord Apr. 22, 1947 Mayle Dec. 30, 1947 Paradise et a1 Aug. 30, 1949 FOREIGN PATENTS Country Date Great Britain Feb. 28, 1946

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