US2753509A - Regulated high voltage power supply - Google Patents

Description

July 3, 1956 F. F. MERRIAM REGULATED HIGH VOLTAGE POWER SUPPLY Filed Oct. 29, 1951 @Wk MEQ A T TOR/VEV United States Patent O REGULATED HIGH VOLTAGE POWER SUPPLY Francis F. Merriam, Mountain Lakes, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application October 29, 1951, Serial No. 253,657

4 Claims. (Cl. 321-18) This invention relates to power supply systems and, more particularly, to a power supply whose output is regulated by electronic control.

Electronically regulated power supplies from a radio frequency alternating source have been found to be limited in their range of regulation. Generally the power supply consists of an oscillator, means for amplifying or multiplying its output, and a rectifier; and regulation is usually achieved by controlling the output of the oscillator in response to a sample of the output voltage fed to the screen grid of the oscillator tube. However, it can be shown that the amount of regulation achieved through such means is necessarily limited to the range of operation of the oscillator tube in that if the change in the output voltage of the supply which is applied to the screen grid causes the amplification of the tube to become less than unity, the condition necessary for oscillation will be destroyed.

It is, accordingly, a primary object of this invention to overcome this dependency of the regulated power supply upon the amplification factor of the oscillator tubes and to provide a regulated power supply system which can operate at any fixed voltage taken from a broad range of possible high and low voltages.

It is a further object of this invention to provide means for regulating the output of a power supply system by controlling the gain of an amplifier therein without affecting the oscillator source.

Furthermore, in power supply systems which make use of multiplier circuits, it has been the practice to heat the lament cathodes of rectifier tubes therein from a source within the voltage generator circuit. Thus, the filament voltage has become a function of the output voltage of the supply, and because the filament voltage must be kept within certain operational limits, the output voltage has been limited proportionately. Consequently, a feature of this invention is the provision of means for supplying the output tubes of a power supply system with a constant voltage the magnitude of which is independent of the voltage of the supply system. Moreover, in order to remove spurious low frequency oscillations generally found in feedback circuits, which may destroy the stability of regulated power supplies, an additional feature of this invention is the incorporation of means for providing a frequency non-sensitive divider in that portion of the feedback circuit where a portion of the output voltage is taken as a sample for feedback purposes.

In accordance with an exemplary embodiment of the present invention, the output of a master oscillator is amplied and applied through a resonant transformer to a series of vacuum tube rectifiers connected in a multi` plying circuit. From this multiplying circuit, the output k 2,753,509 Patented July 3, 1956 ice system. By this means, the gain of the amplifier in the voltage generator circuit is controlled by the output of the power supply and varies the output in response to any change in the output. The tubes of the multiplier are maintained at a constant operating voltage by supplying the filament cathodes from an independent transformer energized through an appropriate amplifier from the output of the master oscillator.

The invention will be more readily understood by referring to the following description, taken in connection with the accompanying drawing forming a part thereof, in which the single figure is a circuit diagram, partially in block schematic form, of a power supply system in accordance with the invention.

Reference will now be made more specifically to the drawing, in which there is shown, by way of example, a power supply system 1l) in accordance with the invention. The supply 10 comprises a master oscillator 11 coupled to a radio frequency amplifier 12 in the main voltage generator circuit. Another signal is fed into the amplifier 12 from a direct-current amplifier 2l, the effective operation of which will be described below. The signal from 12 is reamplified in radio frequency amplifier 13 and fed into the resonant transformer 14. The output of transformer 14 is multiplied and rectified through the tripler 15, comprising tubes V2, V3, V4, and circuits associated therewith and fed to the supply output terminals 16. In order to maintain the filaments of the tubes in tripler 15 at constant operational voltage, excitation voltage is drawn from the master oscillator 11 through the radio frequency amplifier 17 to the transformer 18, which in turn supplies the three tube filaments of the tripler 15 through individual secondary windings. The regulation circuit of the supply 10 includes the frequency non-sensitive voltage divider 19 with inner voltage tap 22, the constant voltage source 20 and the direct-current amplifier 21, the latter of which compares the voltage at the tap 22 with that taken from the source 2t) and applies the amplified difference voltage to the radio frequency amplifier 12.

The master oscillator 11 may have any suitable form; for example it can be of the type disclosed in the R. V. L. Hartley Patent 1,356,763, issued October 26, 1920. The output of this oscillator can be, for example, in the range of 2 to l0 volts and at a frequency in the 200 kilocycles per second range. The oscillator 11 is coupled through the anti-sing resistor 31 and the capacitor 32 to the control grid of the pentode V1 of the amplifier 12. Also coupled to the control grid of V1 through resistance 33 is the direct-current amplifier 21, the function of which will be disclosed below. The suppressor grid of V1 is tied to the cathode and the screen grid is held at a positive potential by a direct-current source 35 connected to ground through resistor 34. A by-pass condenser 35A is also connected between the screen grid and ground. The potential on the plate is supplied by the source 35 through resistor 34 and the LC circuit of capacitor 36 and inductor 37, the latter circuit serving to tune the plate circuit of the tube V1 to resonance. Amplifiers 12 and 13 are coupled by capacitor 38, the input circuit of the amplier 13 also including a voltage source 39 connected through the inductor 39A which maintains the proper bias on the tubes in amplifier 13.

Step-up transformer 14, which is excited by the output of amplifier 13, supplies a constant operational voltage to the three diodes of V2, V3, and V4 comprising the tripler 15 with which the charging condensers 40, 41 and 42 are also associated. Triplers of this type are old in the electrical art. It is more fully described, for example, in Termans Radio Engineers Handbook (1943), page 593. In the supply output circuit, there are the high frequency by-pass circuits comprising capacitors 43, .45` and .47 and resistor 44. Across the output terminals 16 is a frequency non-sensitive 'divider i9 consisting of resistors 46 and 48 and capacitors 45 and 47. To those familar with the art, it is well known that in feedback amplifier circuits of this type the Vfloop gain-frequency 4ratio must be maintained above ycertain cut-off limits to pre-vent spurious low frequency 4oscillations in the circuit. (This subject is more completely covered in Terman, Radio Engineers Handbook, 1943, page 222 et seq.) In order to prevent the voltage divider vmade up of lresistors 46 and 4-3 from contributing to the cut-off characteristics of the feedback loop, it is made frequency-non-sensitive by the addition of capacitors 45 and 47. To accomplish this purpose successfully `it is necessary that the resistors `and capacitors V'be of such magnitude thatCisXRisfCoXRis.

For purposes of regulation, a sample of the outputvoltage is taken from the tap 22 of the voltage divider and applied to the cathode of tube Vs in the amplilier Applied to the grid of Vthe same'tube is the voltage taken from the movable arm of the potentiometer 49, the resistance element of which is connected in parallel with the voltage regulator tube Vr. The latter is supplied from a suitable direct-current source '50 through resistor 50A. Potential for the plate of tube V5 is derived from the source 53A through the resistor 5l and the voltage divider 52 and 53 which plate is connected to the grid of the tube Vs. The potential on the plate of tube Vs comes from the direct-current source 53A through the resistor 54 and the cathode of the tube is given its potential Vfrom the same source through the'voltage dividerEZ vand 53. .Plate responses of the tube Vs, representing the difference between the output voltage sample and the 'fixed voltage from the tube V7, are then fed through the resistor 33 to the control grid of the tube V1 in the amplier l2, which amplifier .gain responds inversely to any change in the output of the power supply, thereby causing the output to 'oe constant.

In keeping with the spirit of the invention, it is possible to ground the positive output terminal instead of the negative one as shown in the drawing and make other minor changes in the circuit constants in order to provide a negative regulated power supply voltage. lilhile there are a number of possible Values suitable for use in the circuit elements, values used in an operative embodiment of the supply system (foren output voltage of 20 kilovolts in operation from a master oscillator frequency of 200 kilocycles at l0 volts) are:

Resistor 3l 60,000 ohms. Condenser 32 500 micromicrofarads. Resistor 33 ll,000 ohms.

Resistor 34 l0() ohms.

Source 35 400 volts.

Condenser 35A 0.1 microfarad Condenser 36 0.012 microfarad. Inductor 37 100 mierohenry. Condenser 38 0.001microfarad. Source 39 45 volts.

Inductor 39A l millihenry. .Condenser 40 500 micromicrofarads. Condenser 41 00 mierornicrofarads. Condenser 42 V 500 micromicrofarads. Condenser 43 '5010 micromicrofarads. Resistor 44"".` 0.2 megohm. Condenser 45 500 micromicrofarads. Resistor 46 200 megohrn. Condenser 47 0.1 microfarad. Resistor 48 1 megohm. Potentiometer@ 50,000 ohms.

Source 50 200 volts.

Resistor 50A 7,500 ohms.

Resistor 51 lmegohm.

Resistor 52 68,000 ohms.

Resistor '53 0.13 megohm.

Source 53A 200 volts.

Resistor 54 10.5.6 megohm.

4 l f i Tube V1 6V6.

Tube V2 lB3.

Tube V3 1B3.

Tube V4 1B3.

Tube V5 1/2 6SL7` Tube Ve 1/2 6SL7. Tube V7 0C3/VR105.

It is .understood that the above-describld arrallllll is illustrative of the application of the principles of the invent n. Numerous other arrangements might be devised by those skilled in the art Without departing from the spirit and scope of the invention.

What is claimed is:

1. In a power supply adapted to feed a load which may vary,V a source of alternating voltage, an amplifier connected to said alternating voltage source, means for rectifying the output of said amplifier, means for obtaining from the rectified voltage a multiplied output voltage comprising a plurality of heated filament-cathode discharge tubes and means associated with the source for applying constant filament voltage to said discharge tubes, means for obtaining from the multiplied output voltage a fixed portion of said Voltage as a sample, a constant voltage source, means for comparing said sample voltage and the output of said constant voltage source to obtain a difference voltage, a direct-current amplier suppliedwith said difference voltage, means for applying the output of said direct-current amplifier to the inputof said amplifying means to thereby regulate said multiplied output voltage, and means for eliminating spurious low frequency oscillations in the sampler circuit comprising two series resistors connected across said multiplied output voltage, and a capacitor in parallel with each resistor and the said resistors and capacitors having such values that the product of the values of one resistor and capacitor in parallel is equal to the product ofthe values of the other resistor and capacitor.

2. In a power supply adapted to feed a load which may vary, a source of alternating voltage, an amplifier connected to said alternating voltage source, means for rectifying the output of said amplifienvmeans for obtaining from the rectified voltage a multiplied output voltage, means for obtaining from the multiplied output voltage a fixed portion as a sample, a constant voltage source, means for comparing said sample-'andthe output of said constant voltage vsource to obtain a difference voltage, means for applying said difference voltage to the input of said amplifying means to thereby regulate said output voltage, and means for eliminating spurious low-frequency oscillations in the sampler circuit, said means compris-ing two series resistors across the supply output land a capacitor in parallel with each resistor and said resistors :and capacitors having values such that the productof the values of Vone resistor and parallel capacitor combination is equal to-the product ofthe value of theotherresistor and capacitor.

3. The power supply according to vclaim 2 in which said constant voltage source comprises -a direct current source,a voltage regulator tube-anda variable resistance potentiometer, said direct-current source, tube-andthe-resistance element of said potentiometer being connected in a parallel circuit.

4. In a power supply adapted to feed a variableload connected across its output terminals, a sourceof radio frequency alternating voltage, an amplifier connected to the `outputof said alternatingvoltage source, means for rectifying the output of said .amplllrmeans Vincluding a heated filament discharge tube forfoblaiuinsifromaid rcfifyins :means-.a multiplied :output :voltasefnleanssoanected to said alternating voltage sourcefar supnlyingaid discharge Vtube with latnent voltageJ --voltaee divider meansfor obtainiuaaifixed portion-Qi:saidallulfipled:.Qui- Put Vvoltage Yasa salrlitzlr, .of constant Wallage., means for comparingsaid Sample ,-withqsaid;cqnstantyoltage to obtain a diterence voltage, means including a direct-current ampliiier for applying said dilerence voltage to said first-named amplifier to regulate said multiplied output voltage, and means for reducing spurious low frequency oscillations in said power supply comprising means for rendering the said sample obtaining means substantially frequency nonsensitive.

References Cited in the file of this patent UNITED STATES PATENTS 1,499,078 Schroter June 24, 1924 6 Rentschler Dec. 8, 1931 Plathner et al. July 16, 1935 Smith `Tuly 16, 1935 Schlesinger Nov. 22, 1938 Wilcox Iuly 4, 1944 Fogel Oct. 9, 1945 Parker Oct. 25, 1949 Miller Feb. 14, 1950 Olson Aug. 28, 1951 Anderson Sept. 11, 1951 Stone Apr. 15, 1952

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