US2565621A

US2565621A - Regulated high-voltage power supply

Info

Publication number: US2565621A
Application number: US119587A
Authority: US
Inventors: Olson Alton Le Roy
Original assignee: Allen B du Mont Laboratories Inc
Current assignee: Allen B du Mont Laboratories Inc
Priority date: 1949-10-05
Filing date: 1949-10-05
Publication date: 1951-08-28
Anticipated expiration: 1968-08-28

Description

1951 A. LE- R. OLSON 2,565,621

REGULATED HIGH-VOLTAGE POWER SUPPLY Filed Oct. 5, 1949 INVENTOR. ALTON LE ROY OLSON PWQ AJ Patented Aug. 28, 1951 2,565,621 REGULATED HIGH-VOLTAGE POWER SUPPLY Alton Le Roy Olson, Lodi, N. J., assignor to Allen B. Du Mont Laboratories, Inc., Passaic, N. J., a

corporation of Delaware Application October 5, 1949, Serial No. 119,587

4 Claims.

My invention relates to electronic power supplies and more particularly to regulated power supplies.

In power supplies where a high voltage of the order of 20,000 volts is desired and where the current drawn from the supply is around 400 microamperes, it is common practice to generate this voltage by means of a so-called radio-frequency power supply comprising an oscillator, a comparatively low voltage power supply of the order of 300 volts output to operate the oscillator, and a tuned circuit coupled to the oscillator with a detector to detect the high voltage appearing across the tuned circuit. It is frequently desirable to maintain the output voltage as close as possible to a fixed value while the current drawn from the supply varies from about zero to 500 microamperes. In this case a regulator is necessary, and, if it is also desired to have the output voltage remain fixed as the A. C. line voltage supplying power to the low voltage supply varies about its nominal value, it has heretofore been the practice to employ a second regulator to keep the output voltage of the low voltage supply at a fixed value.

It is one object of my invention to provide an improved power supply.

A second object is to provide an improved, regulated power supply.

A further object is to provide a regulator which will perform the functions of two regulators previously required as pointed out above.

Other objects will be apparent after a study of the specification and drawing, in which;

The only figure is a schematic diagram of a i power supply employing the invention.

A standard low voltage power supply I is shown having an output lead 2 which conducts current to the screen grid of an amplifier tube 3 through a dropping resistor l, and to the plate of the amplifier tube 3 through a load resistor 5. .I he. lateof a tube 6 functioning as a variable impedance is connected directly to the lead 2 and the plate Of an oscillator tube II is connected to the lead 2 through aradiofrequency choke l and the inductance ll of a tuned circuit 9. A voltage divider comprising a resistor 12 and a resistor I3 is connected between lead 2 and ground.

A voltage regulator tube H such as a VR150 is connected between the screen grid and cathode of the amplifier tube 3 which may be a 6AC'7. Another voltage regulator tube 16 is connected from the cathode of the amplifier tube 3 to round.

The oscillator tube II is connected in a tunedplate oscillator circuit although other types of oscillator circuits would work as well. A portion 01' the energy of this tuned circuit 9, which comprises inductance 8 in parallel with condenser I0, is picked up by the feedback coil is and applied to the grid of tube II by means of the RC coupling circuit consisting of condenser is and resistor 2 I. The screen grid of the oscillator tube II is connected to the cathode of the variable impedance tube 8. A bypass condenser 22 connects the grid and cathode of this variable impedance tube 8. The screen and plate supply voltages of the oscillator tube H are bypassed to ground by

condensers

23 and 24 respectively.

The high voltage rectifier section 25 consists of an inductance 26 which is inductively coupled to inductance 3 and is generally wound on the same coil form therewith. The inductance 28 has an inherent capacity indicated at 21, so that a parallel tuned circuit is formed. A voltage doubling rectifier circuit comprises a pair of diodes 23 and 3| connected in the usual manner with a series capacitor 28 and a load impedance 32. A condenser 33 is connected in parallel with a voltage divider, comprising a resistor 34 in series with a potentiometer 36, forming one current return path for the supply. The arm of the potentiometer 36 is directly connected to the control grid of the amplifier tube 3. The common, low potential terminal of the inductance coil 26, condenser 33 and potentiometer 36 is connected directly by a load 35 to the junction of a pair of resistors 12 and I3, connected in series from the power supply lead 2 to ground.

In operation the power supply I supplies D. 0. power to the oscillator which transforms it into A. C. power. The oscillator may be tuned by adjusting condenser ill, in order that the maximum voltage which is obtained at the frequency at which the inductance 26 resonates with the inherentcapacity 2.1, may be realized across the lead- 32. The voltage doubler rectifier changes the A. C. voltage across the inductance 23 into a D. C. voltage approximately equal to twice the peak value of said A. C. voltage.

The power supply I also supplies power to the plate and screen grid circuits of the amplifier tube 3. A current flows to ground through the plate load 5, through the tube 3 and through the constant voltage tube I6, which furnishes a comparison voltage by holding the voltage at the cathode of tube 3 at a fixed potential. The arm of the voltage divider potentiometer 36 is ad- 3 justed so that the tube 3 operates essentially as a class A amplifier.

The variable impedance tube 6 operates in series between the power supply i and the screen grid of the oscillator tube Ii. The impedance of this tube 6 is controlled by its grid potential, and since the grid of the tube is directly connected to the plate of the amplifier tube 3, any variation of the potential at the plate of the amplifier tube 3 produces variation of the impedance of the tube 8.

An increase in the A. C. line voltage to the power supply I varies the output D. C. voltage on lead 2. A fixed percentage of this change appears at the junction of resistors l2 and 13, thereby raising the potential of the common terminal of inductance 26 and potentiometer 36. This in turn raises the potential of the arm of potentiometer 36 and makes the grid of tube 3 more positive (or less negative) with respect to its cathode. More current flows through resistor 5, lowering /the potential of the plate of tube 3 and the grid of tube 6. The impedance of tube 6 consequently increases, and this results in a decrease of the screen potential of tube II. If the resistors l2 and I3 have been chosen to have the proper resistance, the screen voltage will decrease sufllciently to counteract the oscillator tube plate voltage increase due to the line voltage increase. Therefore the voltage across inductance 26, and consequently across the load 32, will remain constant. There is the same end result if the A. C. line voltage drops.

Most of the current of the high voltage supply normally flows from plate to cathode of the voltage doubler diode tube 3|, through load 32 to ground, through resistor l3, and back through the inductance 26. Thus the voltage across resistor l3 depends on the resultant of the current of power supply I flowing therethrough in one direction and the current of the high voltage rectifier flowing through it in the other direction.

The load 32 is shown as variable to indicate a varying impedance load. As the impedance of the load increases, the voltage thereacross would normally increase except that the current through the load 32, the upward current through resistor 13, decreases. Thus the voltage at the junction of

resistors

12 and 13 increases, and the analysis of operation is the same as in the preceding case. The final result in the case of an increasing impedance of load 32 is that the voltage on the screen grid of oscillator tube II is lowered, thereby decreasing the amplitude of the oscillations suihciently to maintain the voltage across the load 32 at a fixed value.

Although I have described the invention in terms of a specific embodiment, it is obvious that modifications may be made within the scope thereof.

What I claimis:

1. A high-voltage power supply comprising a source of alternating voltage, a low-voltage power supply energized by said alternating voltage and having output terminals, a voltage divider across said output terminals. an oscillator connected to and energized by said low voltage power supply, a tuned circuit coupled to said oscillator, said tuned circuit having a plurality of terminals with a higher voltage between a pair. of said terminals than the voltage between the output terminals oi. said low voltage power supply, a rectifier circuit to rectify the high voltage between said pair of tuned circuit terminals, said rectifier circuit having a pair of output terminals and a voltage divider therebetween, one of said output terminals being conductively connected to one of said pair of tuned circuit terminals, a conductive connection between the tuned circuit terminal to which said rectifier circuit output terminal is conductively connected and a tap on said first-mentioned voltage divider, a vacuum tube having an input electrode connected to a tap on said second mentioned voltage divider, a source of relatively fixed voltage connected to a second electrode of said vacuum tube, and a plate circuit for said tube having current flow controlled by thevoltage difierence between said input and said second electrode, and a conductive connection between said plate circuit and said oscillator.

2. A controlled direct current power supply comprising a first source of D. C. voltage and an oscillator connected thereto and energized thereby, a rectifier circuit connected to said oscillator and energized thereby, said rectifier circuit providing a second source of direct current at the output terminals thereof, a voltage divider connected across said first source and a conductive connection from a tap thereon to one of said output terminals of said rectifier circuit, a source of constant voltage, a control amplifier connected to said rectifier circuit to derive voltage therefrom and to said source of constant voltage, said amplifier being connected also to said first source of D. C. voltageto be energized thereby and being controlled by the diiference in voltage between said constant voltage and said derived voltage, an output terminal of said control amplifier being connected to said oscillator to control the amplitude of oscillations thereof.

3. A controlled direct current power supply comprising a first source of D. C. voltage and an all oscillator connected thereto and energized thereby, a rectifier circuit connected to said oscillator and energized thereby, said rectifier circuit providing a second source of direct current at the output terminals thereof, a first voltage divider connected across said output terminals, a second voltage divider connected across said first source, a conductive connection from a tap on said second voltage divider to a point on said first voltage divider, a source of constant voltage, a control tube having its plate circuit connected to said first source of D. C. voltage to provide plate current therein and having one input electrode connected to a point on said flrst voltage divider and a second input electrode connected to said source of constant voltage, said plate current being controlled by the difi'erence in voltage between said constant voltage and the voltage at said point on said first voltage divider, said tube being connected to said oscillator to control the amplitude of oscillations therein.

4. The device of claim 3 in which the load circuit is connected between a point on said first voltage divider and one terminal of said second voltage divider.

ALTON LE ROY OLSON.

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

UNITED STATES PATENTS Number Name Date 2,386,548 Fogel Oct. 9, 1945 2,424,972 Dubin Aug. 5, 1947 2,485,652 Parker Oct. 25 1949 2,497,182 Miller Feb. 14, 1950