US2318644A - Voltage regulation and supply - Google Patents

Description

May 11, 1943. E. A. TU BBS 2,313,644 7 VOLTAGE REGULATION AND SUPPLY Filed Dec. 24, 1958 2 Sheets-Sheet 2 IIIIF 91 INVENTOR.

ERNET A .TUBBs MMW4QM A TTORNEYS.

Patented May 11,1943

UNITED STATES PATENT OFFICE 2,318,644 voursoa REGULATION AND surrey Ernest A. Tubbs, Long Island City, N. Y., assignor to National Television and Manufacturing Corporation, a corporation of Delaware Application December 24, 1938, Serial No. 247,721

7Claims.

This invention relates to voltage regulation, and has, for is principal object, to provide a power supply having an extremely constant voltage which will not be appreciably disturbed by changes in load conditions or variationsof the source.

Another object of the invention is to provide a regulated power supply with an extremely low internal impedance.

Still another object of the invention is to provide a voltage regulation circuit comprising a gas discharge device with means to operate said device so that it always has its substantially maximum regulating eilect.

Another object of the invention is to provide a voltage regulation network, including a pentode tube, with means to maintain a substantially constant potential diil'erence between the screen and the cathode of the tube, while com.

pensating action is provided by variations of the control grid.

Another object of the invention is to provide a I regulated power supply with a wide voltage range.

Another object of the invention is to provide a voltage regulating circuit with an adjustable range of o utput'voltage in which the effective regulation is substantially constant over the output voltage range.

Another object ofthe invention is to provide the output voltage.

Another. object of the invention is to provide a regulated voltage supply comprising a Plurality of regulating networks connected in series or parallel, or both, for providin several difierent voltages at the same time'without the loads of either aflecting the others. 7

The invention has been illustrated in the accompanying'drawings, in which: Fig.1 is a circuit diagram of one form of the invention;

Fig. 2 is a diagram of a portion of the circuit of Fig. 1 showing .a modified form of voltage regu-' lation device; I

Fig. 3 is a diagram of an'equivalent circuit of v a portion of the circuit oi'Flg. 1;

Fig. 4 is a circuit diagram of a modified i'orm of the circuit of Fig. 1;

Fig. 5 is a circuit diagram of still another modified form of the circuit of Fig. 1; 4

Fig. 6 is a circuit diagram of a modified form of the circuit of Fig. 1 showing the'simultaneous inputind output voltage control;

Fig. 'l is a circuit diagram of a form of the invention adapted to permit several difierent output voltages; and

Fig. 8 is a circuit diagram of modified form of Fig. 6, arranged for a supply of negative voltage.

As will be understood, no power supply system Hence there' can have zero internal impedance. must always exist across the terminals oithe power supply device under load conditions a voltage which is somewhat less than the voltage w ch would exist for open circuit or zero load. I the load fluctuates, the terminal'voltage will fluctuate also. A power, supply system in which the drop in voltage under load is excessive is spoken of as having poor regulation; one in which the drop is small is said to have good regulation or to be tight.

For the purposes of this application, applicant chooses the following definitions:

"Direct current" is considered to be 'a current flowing always in the same direction and having, over the entire period of time involved, the same value.

' "Alternating current is the current which is left after the direct current component, as above defined, is subtracted from the total current.

Alternating current has a constant frequency only when its wave form is a mathematically pure sine wave. Any deviation from this condition may be shownto introduce frequencies other than the original frequency. From the foregoing it follows that when a power supply system is supplying an alternating current load, the voltage at the terminals 01' the power supply fluctuates at the frequency drawn by the load and by an amount depending upon iii, the primary of which may be connected to a source of alternating current supply, as, for instance, the sixty cycle lighting mains, while the secondary is connected to the anodes of a full wave rectifier H. Following the usual practice, the mid-point of the secondary of the transformer may be connected to the neutral side-of the circuit, as represented by the wire i2, while the cathode of the rectifier ii may be connected to the choke #3 which is placed in the high potential side of the circuit. 'The usual potentiometer resistance M may be connected-between the high voltage side of the circuit and the neutral side, and in series with the choke i3 and the potentiometer resistance Ed I provide a thermionic tube l5, the anode it of which may be connected directly to the choke it, while the cathode I! may be connected to the potentiometer M. This tube acts as a variable resistance in the circuit to automatically regulate the voltage output. The output voltage is taken off between the point Ma. at the high potential end of the potentiometer it and the neutral wire '82.

I preferably use a three element tube with an independently heated cathode, although a tube with a filamentary cathode may be used if desired. The heater for the cathode .I I has been omitted in the drawing, and it will be understood that separate filament windings on the transformer id will be provided for energizing this heater and the heaters of other tubes in the circuit, or a separate filament transformer may be used for this purpose. The latter may be preferred as it provides a means to control the high voltage supply independently of the filaments of the tubes used in the circuit.

- A filter condenser it may be connected across the high and low sides of the circuit between the choke and tube i5, following ordinary practice. However, the regulating eifect of the circuit is such that no particular care need be taken in filtering the voltage supply up to the tube I 5, and hence a single sixteen microfarad condenser has been found to be sufficient for this purpose.

A second thermionic tube l9 and a voltage regulating device 20 may be connected in series between the grid 2! of the tubev I 5 and the neutral wire l2. The tube is preferably a pentode tube. with the plate 22 being connected directly to the grid 2| of the tube I5, and the cathode 28 being connected directly to one terminal of the regulating device 20, the other terminal of which is connected to the wire I 2. The plate potential may be supplied through a resistance 2212 from the high side of the circuit. The suppressor grid 24 of-the tube l9 may be connected directly to the cathode. The screen grid 25 of the tube l9 maybe connected to a point 26 on the potentiometer H,-which will give it a suitable operatin: potential. The control grid 21 of the tube I9 may be connected through a resistance 28 to a movable contact arm 29, which may be adjusted along the potentiometer It to give the grid 21 a potential slightly negative with respect to the cathode 23, which is given a potential by the operating voltage of the regulating device.

A condenser 30 may also be connected between the grid 2l-and the high side of the line at the cathode of the tube H5. The cathode 23 of the tube i9 may also be connected through a resistance 3! to the high potential end of the potentiometer M, to insure sufiicient operating current for the regulating device 20. Across the particular regulating device 213, used in Fig. 1, I preferably connect a condenser 32 for the purpose of v insuring better regulation for alternating current components.

I have found that the action of any device in regulating the voltage depends on the favorable ratio of its equivalent direct current resistance to its incremental resistance. If the equivalent direct current resistance is very high in comparison to the incremental resistance, a good regulating ei'ect will be obtained when the device is connected in series with a large resistance. The voltage drop across the device may be used as a reference voltage in the control network.

One device in which the above mentioned ratio may be made high enough for good regulating efiects is a gaseous discharge device in which a pair of electrodes are arranged in spaced relation immersed in an inert gas under reduced pressure. Neon, argon, helium, krypton, and zenon might be used in such a device with gas pressures somewhere around 10 millimeters of mercury, depending on the particular gas used and the positioning and character of the electrodes. For such a device I prefer to have a ratio over 300 for conditions of stable operation.

In Fig. 1 a gas discharge lamp has been used for the regulating device 20. The condenser 32 across the lamp decreases the incremental resistance between the terminals'of the device and therefore has the efiect of improving the ratio.

Another device which might be used in place of the device 20 in Fig. 1 for producing the desired high ratio of equivalent direct current resistance to incremental resistance is a high vacuum tube in which the plate-cathode circuit has the desired ratio. Such a voltage regulating device is illustrated in Fig. 2 where the .triode 33, having an the plate.

- is so balanced that there is a certain normal predetermined potential difference between the points" 29 and 23 for a given voltage across the bridge. It is desired to have a maximum of unbalance for voltage changes. If the voltage changes, the action of the regulating device upsets the balance of the circuit with the result that the potential difference between points 29 and 23 changes, and this means that the potential of the grid 21 will change with respect to the cathode 23. This change in potential is then amplified by the entire circuit.

thetube ".mdasthenhtecirrrentofthat tube passes through the resistance 220, the amplified voltage variation will take place across this resistance. The resistance 2241, however, is also between the cathode I1 and grid II of the tube i5,

and hence the plate cathode resistance of thisv tube is varied, thus varying the potential across Itwillbeseenthatasthe voltage across the bridge rises there will be a rise in the resistance of the tube ll, so that the action of this tube compensates for the original change in voltage. This tends to maintain the voltage constant across the entire circuit.

I have found that maximum regulating effect of the circuit will be obtained when the following equation is a maximum:

.of the change on the grid of the screen grid tube to the total voltage change is also increased.

I have found that one method of unbalancing the bridge circuit for changes is the use of the condenser 30 and resistance 28. When the resistance 28 is very large compared to thegreactance of the condenser 30, for the frequency components present in the voltage change, the grid 21 will be effectively directly tied to the point l4a for these frequencies.

In determining'the respective sizes of the condenser and resistance consideration should of course be given to the fact that the change in grid voltage (AE should beas nearly in phase with the total change (AEt) as possible. I prefer to use a resistance of at least a half million ohms,

with which, for even relatively rapid variations, the condenser can be relatively small. With only .1 mid. condenser and this resistance value, improved regulation is insured for changes down to at least one cycle per second.

. This grid leak and condenser arrangement enables the circuit to efl'ectively compensate for surges and other objectionable transients coming in over the power lines. The internal impedance (the impedance looking back into the output terminals I 40 and ll of the circuit) is also greatly reduced for alternating currents.

The potential output of the system of Fig. i may be adJusted within certain limits by adjusting the arm 28 on the potentiometer l4.

With the circuit of Fig. l the tube I! will not always operate with maximum amplification, and

to improve this condition I may use the arrangement shown in Fig. 4. The same circuit as shown in Fig. l is used including the. tube l9, and

in addition another tube, 35, is connected in parallel with the tube I. This may be a pentode tube with its cathode 36 connected directly to the neutral wire I! through a biasing resistance 31, by-passed by a condenser 38. The anode II of this tube may receive its operating potential suppressor grid 42 of the tube 36 may be connected to the cathode as shown, while the screen grid 43 may receive a suitable potential from a point 44 on the potentiometer l4. The control grid 45 of the tube 35 may be connected directly to the high side of the potentiometer l4 through a condenser 48, while a grid leak 41 may be inserted between the grid and the neutral wire l2.

When adjusting for low voltage output the grid of the tube is may be backed oil to such an extent that this tube is no longer an eillcient ampliher for voltage changes. It will be seen that the rid 45 of the tube ll receives its potential changes through the condenser 46 from the high side Ila of the potentiometer I4. Therefore the tube 35 is more effective than the tube is for changes under these conditions.

Another modified form of the arrangement of Fig. l is shown in Fig. 5, in which the tubes II' sistance 48 connected to the high point Ma, and

a parallel circuit connected between the variable resistance and the neutral wire II. The parallel circuit may comprise in one leg a voltage regulating device, such as the gas discharge lamp 49, in series with a resistance 50, and in the other leg a resistance 5|.

The discharge lamp, together with the resistance 48, preferably has the same voltage drop as the upper part of the potentiometer I4 of Fig. 1, from the point 29 to the point I4a, so that the point 52 in Fig. 5 provides the grid 21 of the tube IS with the same average potential as in the case of Fig. 1. The screen grid 25 of the tube It, however, is given its potential from a point on the resistance II.

In order to provide higher operating plate potential for the tube I 8 I connect the plate of the tube through a resistance I4a to the plate of the tube l5 instead of to the cathode, as' in the previous figures. Also the cathode of the tube is is preferably connected through a resistance 48a to the junction of the resistance 48 and the gas discharge tube 49.

In this arrangement the equivalent bridge circuit has the gas discharge lamp 20 and the cathode-anode circuit of the tube i9 forming one arm. while the resistance 50, the gas discharge lamp 49. and the resistance 48 forms the other arm. The cathode and the grid of the tube- N form the neutral or balance points of the bridge. When the potential across the bridge changes,

the two gas discharge lamps being diagonally J opposite each other, will tend to upset the balance of the bridge in the same direction, so that they will both tend to make the grid of the tube l9 more positive or more negative, depending on the change in potential across the bridge. The gas device being inherently a requisite for extremely slow varlationsbecomlng less effective at relatively rapid variations, therefore cooperate; with the condenser and resistance which is increasingly eil'ective for variations of higher frequencies. to increase the regulation for any and all variations regardless of their rapidity.

Two important advantages are obtained by the variable resistance 4! which is used for adjusting the output potential within certain predetermined limits. It has already been stated that it is important have a voltage regulating device with I a high ratio of equivalent direct current resistance to incremental resistance. However, in many gas discharge devices this ratio will change with the voltage applied to the device, as the operation takes place on;a different portion of the voltage-current characteristic curve. Thus it may be possible to have a high-ratio for one part of the curve and a very low ratio for another part of the curve. As the regulating action of the discharge device is a function of this ratio, poorer regulation will take place when the voltage has been changed to shift the operation to the part of the curve having the lower ratio.

I have found that with the adjusting arrangement of Fig. 1, where the arm 29 adjusts the output potential, the current through the gas discharge lamp 20 is also changed, which changes the ratio, with the result that the regulation of the circuit is changed for different adjusted.

values of output potential. In the arrangement of Fig. 5 this defect is overcome, because the adjustment of the resistancev dB, for making the adjustment of output potential, makes relatively no change in the current through the gas discharge lamps and therefore keeps the ratio constant. This permits the adjustment of the circuit for difierent output potentials, within certain limits, without changing the regulation, which remains substantially constant.

The other important fact which also insures constancy of regulation through various adjustmerits of the output potential, is that the circuit provides substantially constant potentials for the elements of the tube l9. In Fig. 1 adjustment of the arm 29 toward the neutral end of the potentiometer, to give the control grid a more negative potential, will also give the screen grid a more positive potential, because it is connected to the same potentiometer, which tends to compensate for the change in potential on the grid.

The grid, therefore, has to be made more negative by moving the arm 29 still farther down on the potentiometer. This change in the potential of the screen -grid with respect to'the cathode and control grid changes the amplification factor of the tube, and hence variations impressed on the grid will not be' amplified as much under one condition as under another. Therefore the regulating ability of the circuit is different for different adjustments of the output potential. In the circuit of Fig. 5-, where the adjustment is made by changing the resistance 38, the screen grid potential remains substantially constant with respect to the cathode; so that amplification of the tube is is kept substantially constant and'the regulation is therefore substantially constant for various adjustments of the output voltage.

The above two facts, acting together, give greatly improved regulation over the circuit of Fig. 1. The grid leak 53 and condenser Mact in the same way as the corresponding parts of Fig. 1 to make the circuit faithfully respond to surges and other sudden changes of input voltage, as well as load variations, which tend to reflect back into the circuit. 7

In certain cases, especially where low voltages are required, I may substitute a resistance for the regulating device 20 of Fig. 5 and depend on the voltage regulation of the device 59.

In some instances I may prefer to insert in place of the resistance Ell or the resistance illa,

or both, the plate-cathode circuit of a screen grid tube orsome kind of a ballast tube, such as a tube with an iron wire filament which has a ratio of equivalent direct current resistance to incremental resistance of less than unity. Either of these devices will act opposite to the action of the device 20 by still further unbalancing the equivalent bridge circuit.

.The resistance 5i] or the screen grid tap on the resistance 5!, may be varied to initially insure the grid 2? being negative with respect to its cathode, a condition which should always obtain.

In Fig. 6 I have shown a modification of the invention which may have certain advantages over the circuits of the previous figures. A transformer 55 may be used as a source of high alternating voltage. This transformer may have a primary winding 55 which may be connected to the source of alternating current power, and this primary may be provided with a control device $1 for adjusting the voltage applied to the primary.

This control device may be any device suitable for this purpose, and it may be either incorporated in the primary winding of this transformer, or provided as a separate unit in series with the primary winding. As shown, an arm provided with a carbon contact is arranged to sweep across certain of the'primary turns, thus regulating the number of turns in the primary coil. The carbon contact is provided so that no turn of the primary can becompletely short-circuited.

' Otherwise the transformer 55 may be the same as'the transformer it of Fig. 1,.and may be provided with a similar rectifier tube 53, which may feed the high voltage rectified current into the choke 59, which may be similar to the choke of Fig. l The mid-point of the high'voltage secondary E9 of the transformer may be connected to ground, as indicated, and to the wire ti, form- 7 the cathode $5 is connected to thepoint tit on the high voltage side of the potentiometer. The other end oi the potentiometer is connected to the neu= tral wire ti. A filter condenser til may be connected across the system between the choke 59 and the neutral wire ti, forthe same purpose as the condenser it of Fig. 1, to filter out extreme variations in the voltage supply.

Also in this modified form I provide a tube 68, which may be similar to the tube i9 of Fig. 1, and connect it in the same way, with the anode t5) connected directly to the grid it of the tub b2, and the cathodell connected through a, gas discharge tube .772 to the neutral wire ti. A con= denser it may be connected across the gas discharge lamp ?2. The operating potential for the anode 85in this case, similar to Fig. 3, may be provided directly from the choke 59 through a resistance it. The screen grid 75 may be connected to a point it on the potentiometer 63 to provide it with a suitable potential, and the control grid ll may be given its suitable potential through a resistance It at the point it on the potentiometer 63. A condenser may also be used to connect the grid li directly to the point 66 at the high side of the potentiometer.

Similar to the arrangement of Fig. 5, I use a resistance 8i is used, as in Fig. 5, for adjusting the output voltage of the system.

With the arrangement showrrin Fig. 6 I have many of the advantages egrplain ed in connection with Fig. 5. In fact the circuit of Fig. could be substituted for the right hand side of Fig. 6, where good regulation for slow change is desired.

I have found that if I couple the control of the resistance 9| withthe control 91 of the input voltage, as indicated by the dotted line 94, I am able to produce a wide range of voltage output for the particular circuit arrangement.

It can be appreciated that the output voltage can be adjusted only within certain limits by the adjustment of'the variable resistance 9|. These limits are chiefly determined by the allowable plate dissipation of the tube 62 and the voltage between its cathode 95 and the cathode H of the tub 99, which is the voltage available for negatively biasing the grid ill of the tube 62. It will be seen, therefore, that the voltage of the point" 99 cannot be lowered beyond a certain value for a given voltage on the plat 94. If it is desired to In some cases it may be desirable to have a regulated voltage supply which will provide several different voltages, ranging say, from 80 to -300 volts. In order to provide several points at which the different voltages may be taken off, I may use the circuit arrangement of Fig. 7 which may have the power supply transformer'and rectifler the same as is shown for Fig. l or 6, al-

though these have not been shown in Fig. 7. The transformer, of course, should be designed to have a high voltage output in excess of 300 volts.

' connected to the output side of the filter choke 99.

there being a filter condenser 91 connected between this point and ground, the arrangement being similar to the arrangement of the choke and filter of the previous figures. The circuit 95 may have its neutral side 99 connected to ground, and the various components may be so chosen that a maximum voltage of 300 volts may be provided at the point 89, which is the high side of that particular circuit.

The circuit 99 may also be exactly similar to the circuit 95, and may be connected to the same side of the choke 99. This circuit-may have its components so chosen that a potential of about 200 volts will be found at the tap 9|, which is connected to the high side of the circuit 99.

The circuit 92 may also be exactly the same 5 desirable combination or circuits may be used in this manner for producing diiferent potentials,-

and the range may be still further increased by using the variable input arrangement as shown in Fig. 6.

,Wherever the voltage regulating devices are used in the circuits it will be understood that two or more may be connected in series if a greater voltage drop across the device is desired. I have discovered that connecting such circuits in series has the result of decreasing the internal resistance If it is desired to obtain a regulated supply of negative voltage, any one of the circuits may be used. with the choke inserted in the lead to the mid point of the high voltage winding of the transformer, instead of the location shown, and with the positive side of the output connected to ground instead of the low side. The arrangement is indicated in Fig. 8, which shows the circuit of Fig. 6 arranged for a negative supply.

Under certain conditions I have foundit desirable to provide a variable resistance at the lower end of the potentiometer which may be used for adjusting the voltage. Such a resistance, indicated at 19a in Fig. 6, may preferably be used in place of the variable contact 19 to initially adjust the grid of the tube 99 to insure its being negative with respect to the cathode.

.Various combinations of the circuit arrangements shown in the different figures may be made to obtain certain results, as desired. The circuit of Fig. 5 is particularly advantageous for holding a constant voltage output for slow variations I in the voltage of the alternating current source.

ply filter circuit, so that a cheap filter circuit may be used. I have found that when properly adjusted, the regulating circuits shown in Figs. 5. 8 and 7 may be made to have an internal resistance of less than one ohm.

Having thus described my invention, what I desire to secure by Letters Patent and claim is:

1. A voltage regulating system comprising, in

' combination, a rectified supply circuit, an electronic relay having a cathode, an anode, and a as the two circuits 95 and 99, but may be concircuit 92 is in series with the circuit 90. Any

control electrode, and having a variable'resistance space path connected in series in'the current supply path, means for controlling the resistance of said path in a manner to maintain a substantially constant output voltage, said means comprising a circuit having a pair of branches across said supply circuit, one branch having therein a portion having diiferentimpedances for direct and alternating current, the other branch having in parallel with a portion thereofla resistance and condenser in series, the values of said resistance and condenser being such that the impedance of said condenser is low relative to said resistance at low frequencies, a second electronic relay having a cathode, an anode and a control electrode, said cathode being connected to an intermediate point in the first branch, and the control electrode being connected between said resistance and condensenin said second branch. and a" connection between able resistance varies the output voltage without substantially varying the voltage across said I branches.

4. A voltage regulating system comprising, in combination, a rectified supply circuit, an electronic relay having a cathode, an anode, and a control electrode, and having avariable resistance space path connected in series in the currentsupply path, means for controlling the resistance of said path in a manner to maintain a substantially constant output voltage, said means comprising a circuit having a pair of branches across said supply circuit, one branch having therein a portion having difi'erent impedances for direct and alternating current, a second electronic relay having a cathode, an anode, and a control electrode, said cathode being connected to a point in one branch, and said control electrode being connected to a point in the other branch,

means for supplying changes of voltage from said path, means for controlling the resistance of said path in a manner tovmaintain a substantially constant output voltage, said means comprising a circuit having a pair of branches across said supply circuit, one branch having therein a portion having different impedance for direct and alternating current, a second electronic relay having a cathode, an anode, and a control electrode, said cathode being connected to a point in one branch and said control electrode being connected to a point in the other branch, means for Supplying changes oi voltage from said anode to the control electrode of the first relay, a resist= aerator ance in series between the Junction of said branches and the cathode of'the said first relay, means for varying said resistance, means for varying the effective turns ratio of said transformer, and a single means for operating both said last mentioned means simultaneously.

6. A voltage regulating system comprising, in combination, a rectified supply circuit, an electronic relay having a cathode, an anode and a control electrode, and having a variable resistance space path connected in series in the current supply path, means for controlling the resistance of said path in a, manner to maintain a substantially constant output voltage, said means comprising a circuit having a pair of branches across said supply circuit, one branch having therein a portion having different incremental and direct current resistances, the

other branch having therein a portion having:

different incremental and direct current resistances, a second electronic relay having a cathode, an anode and a control electrode, said cathode being connected to a point on one of said branches and the control electrode being connected to a point on the other branch, and means for supplying changes of voltage from the anode of said second electronic relay to the control electrode of the first relay.-

7. A voltage regulating system comprising, in

combination, a rectified supply circuit, an electronic relay having a cathode, an anode and a having therein a portion having different incremental and direct current resistances, and including in parallel with a portion thereof a resistance and condenser in series, the value of said resistance and condenser being such that the impedance of said condenser is low relative to said resistance at low frequencies, a second electronic relay having a cathode, an anode and a control electrode, said cathode being connected to a mint on one of said branches and the control electrode being connected to a point-on the other branch, and means for supplying changes of voltage from the anode of said second electronic relay to thecontrol electrode oi the first relay.

ERNEST A. TUBES.

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