US2900511A - Regulated power supply - Google Patents

Description

Aug. 18, 1959" M. s. SPARKS, JR., ETAL REGULATEDL POWER SUPPLY Filed July 23, 1956 SAMPLE 3 CELL AMPLIFIER RECORDER INVENTORS M.S. SPARKS JR. TH HARP JR.

A TTORNEYS United States Patent 2,900,511 REGULATED POWER SUPPLY Marshall S. Sparks, Jr., Los Angeles, Calif., and Thomas vH. Harp, Jr., Bartlesville, 0kla., assignors to Phillips [Petroleum Company, a corporation of Delaware Application July 23, 1956, Serial No. 599,576

7 Claims. (Cl. 250-435) This invention relates to regulated power supplies. In one aspect it relates to an analytical instrument utilizing such powersupply in conjunction with a hydrogen discharge lamp.

Heretofore, many circuits have been proposed to produce a constant voltage output from a power supply, ranging from rather simple circuits to quite complex hook-ups. However, where current isto be supplied to a discharge device, such as a hydrogen lamp, a high voltage is necessary to start the lamp and thereafter, the operating voltage drops substantially. After the initial ignition, the current through the lamp should remain quite uniform, particularly where the radiation therefrom is utilized in an analytical instrument, such as an ultraviolet analyzer.

In accordance with this invention, the foregoing results are obtained with simple inexpensive equipment of small size and having low heat dissipation, an output of very low ripple being obtained. To this end, a reference impedance, usually a resistance, is connected in series with the load and the voltage appearing across this resistor is applied to the grid of a control tube having its cathode connected to a discharge device, such as a neon lamp. A voltage from the anode-cathode circuit of this tube is applied to the control grid of a regulator tube connected in series with the output of the power supply to be regulated. In this fashion, the neon lamp, which has a constant voltage thereacross, serves as a source of reference voltage with which the voltage drop across the aforesaid series resistance is compared to provide excellent constant current characteristics.

Where the power supply is utilized in conjunction with'a discharge device, such as a hydrogen lamp, the usual bleeder resistor connected across the output terminals is eliminated so that the discharge device constitutes the sole connection between the output terminals. This contributes to producing a high starting voltage with a subsequent well regulated constant operating current.

It is a feature of this invention that radiation produced by the lamp is of very constant intensity and substantially unaffected by changes in line voltage so that this radiation can very advantageously be utilized in an analytical instrument, such as an ultra-violet analyzer. It is a further feature of this invention that a bridge rectifier circuit is utilized in conjunction with a filter of high capacitance and low inductance, resulting in low heat output, eflicient filtering, and circuit components of small size.

Accordingly, it is an object of this invention to provide a regulated current supply having improved characteristics and advantages in operation over previous regulated power supplies.

It is a further object to provide a very simple unit of this type wherein the components can be of quite small sizeand yet produce a voltage very free from ripple. .[It is a still further object to provide an improved radiation source for an analytical instrument.

str ument utilizing the improved power supply of this invention.

Referring now to the drawing in detail, a power transformer 10, which can be of small size, has its primary winding connected in circuit with a switch 11, a fuse 12 and a plug 13 adapted for connection to an alternating current main. The secondary winding of the transformer 10 is connected to two opposite corners of a rectifier bridge 14 defined by four fused germanium power rectifiers 14a to 14d. The other .pair of opposite corners of the bridge 14 are connected respectively to ground at 15 and to a filter which includes a series inductance 16 and a pair of large filter condensers 17 and 18.

Due to the small size of the power transformer and the use of a choke 16 of low inductance in conjunction with condensers of high capacity, the size of the parts required is quite small, and a relatively small amount of heat is produced in the rectifier due to the germanium units 14.

The junction between the choke 16 and condenser 18 is connected to the anode of a voltage regulator tube 19, the cathode of which is connected to an output terminal 20.

A load, such as a discharge device 21, which can advantageously be a hydrogen lamp, is connected to the output terminal 20, and to a second output terminal 22 which, in turn, is connected through an impedance unit 23 to ground, thus completing the power supply circuit.

The impedance unit 23 includes three fixed resistances 23a, 23b, 23c and a potentiometer 23d, any one of which can be selected for operation by manipulation of switches 24 and 25. One terminal of the switch 25 is connected to the control grid of a tube 26, the cathode of which extends to ground through a discharge device 27, such as a neon tube, and the anode of which is connected through a fixed resistance 28 to the cathode of the tube 19.

The anode of the tube 26 is further connected by a lead 29 to the control grid of the voltage regulator tube 19, and the cathode of the tube 26 is connected through a fixed resistance 30 to the cathode of the tube 19.

In operation, when the power supply is energized by the switch 11 with the discharge device 21 in a static condition, i.e., heater on but are not formed, the static current flowing through reference impedance 23 is not of sufiicient magnitude to create a voltage high enough to cause control tube 26 to become operative. Therefore, the voltage drop across resistance 28, which appears as the grid bias voltage on regulator tube 19, is of such small magnitude that the voltage drop across regulator tube 19 is very small, and a high voltage appears between the output terminals 20, 22, sufiicient to initiate operation of the discharge device 21. In order that the initial high voltage may be provided, the usual bleeder resistor connected between the output terminals 20, 22 is eliminated so that the device 21 forms the sole conneotion between the output terminals.

Also, at the time the power supply is turned on, the discharge device 27 is energized due to the connection of one terminal thereof to the cathode of tube 19, which is positive, and the connection of the other terminal thereof to ground. Such energization of the device 27 produces a constant voltage at the cathode of the tube 26. Moreover, the current flowing through the selected impedance 23 causes a desired predetermined voltage to be impressed upon the control grid of the tube 26 when the current flow through the load 21 is atthe desired Patented Aug. 18, 1959 grid of the tube 19 of the correct value to provide the desired current flow through the load.

Should the current through the load tend to increase, due to a change in line voltage or other upset, an increased current flows through the selected impedance 23, thus increasing the voltage drop across this resistance and raising the potential of the control grid of tube 26. This results in an increased current fiow through the tube, due to the maintenance of the cathode at a constant potential by the discharge device 27. This reduces the anode voltage of the tube 26 and the voltage applied to the control grid of the tube 19, thus tending to decrease the current flow through the load to its desired value. Should the current flow through the load tend to decrease, an opposite action occurs and the potentials at tubes 26, 19 are adjusted to increase the current and restore it to the desired value.

Where the circuit of the present invention is utilized, excellent load and line regulation can be obtained as compared to power supplies previously utilized for this purpose, a load regulation of l/ 30 and a line regulation of 1/ 38 being readily obtained with the present equipment. That is, a 30 percent change in voltage across the load would produce only a 1 percent change in the current flowing therethrough.

The provision of the selector switches 24, 25 and impedances 23 permits the flexibility of the unit to be substantially increased and, where these resistors are of low temperature coefficient, extremely fine regulation can readily be obtained.

Suitable values for the circuit components are as follows:

voltage 275 volts, operating Voltage 90 volts at 200 milliameters.

Neon tube 27 Constant operating potential of 50 volts.

It will be understood, of course, that the above circuit components may be changed somewhat depending upon the particular hydrogen lamp or other discharge device utilized as the load, upon the particular line voltage available, and other factors.

It is a feature of the invention that the system as thus far described produces an excellent radiation source for an analytical instrument, such as an ultra-violet analyzer. Such instrument can include a chopper 32 driven by a motor 33, a filter 34, and a sample cell 35 having an inlet 36 and an outlet 37, all disposed in the path of a radiation beam passing from the source 21 to a detector 38, such as a photoelectric cell, which in turn is connected to an amplifier-recorder 39. Such an instrument alternately passes a filtered radiation beam including wave lengths absorbed by the sample, and a filtered radiation beam not including such wave lengths through the cell 35 whereby the average output of the unit 39 is representative of the concentration of a component of interest in the sample flowing through the cell. The source is also applicable to other types of analyzers where two beams are utilized, one passing through the sample and the other through a standard material in order to produce an output representative of the concentration of a component of interest in the sample.

Although the invention has been described in connection with a preferred embodiment thereof, such descrip- .4 tion is merely explanatory of the invention and is not to be construed as limiting the scope thereof.

We claim:

1. An analytical instrument comprising, in combination, a source of alternating current, a rectifier connected thereto, a filter connected to said rectifier, a regulator tube including at least an anode, a cathode, and a control grid, and a hydrogen discharge lamp, all connected in series with the output of said filter; an impedance connected in series with said hydrogen discharge lamp; a control tube having at least an anode, a cathode, and a control grid; a discharge device connecting the cathode of said control tube to that terminal of said impedance remote from said lamp; a lead connecting the control grid of said control tube to the other terminal of said impedance, means for impressing an operating voltage upon said discharge device, and means for applying a control voltage from the anode-cathode circuit of said control tube to the control grid of said regulator tube; a detector sensitive to ultra-violet radiation arranged to receive a beam of radiation from the said hydrogen lamp; and means for positioning a sample to be analyzed in the path of said radiation beam.

2. A current regulating power supply comprising, in combination, a source of alternating voltage, a rectifier connected to said source, a filter connected to said rectifier, a pair of output terminals, a voltage regulator tube having at least an anode, a cathode, and a control grid connecting one output terminal to said filter, a resistance connecting the other output terminal to said filter, a hydrogen discharge lamp connected between said output terminals, said lamp forming the sole connection between said terminals, a control tube having at least an anode, a cathode, and a control grid, a neon tube connecting the terminal of said resistance remote from said output terminal to the cathode of said control tube, a lead connecting the grid of said control tube to a portion of said resistance remote from the terminal thereof connected ot said neon tube, a lead connecting the anode of said control tube to the control grid of said regulator tube, and means for applying a positive voltage to the cathode of said control tube and a more positive voltage to the anode thereof.

3. A current regulating power supply comprising, in combination, a power transformer having a primary winding and a secondary winding, means for supplying line voltage to said primary winding, a rectifier bridge defined by four fused germanium diodes connected to the secondary winding of said transformer, a filter connected to said rectifier and comprising a series choke of low inductance and a plurality of parallel condensers of high capacitance, a regulating tube having at least an anode-cathode control grid, first and second output terminals, means for connecting said regulating tube in series between said filter and said first terminal, hydrogen discharge lamp connected between; said output terminals, said lamp forming the sole connection between said terminals, a control tube having at least an anode, a cathode, and a control grid, a resistance having one terminal thereof connected to the second of said output terminals, a neon tube connecting the terminal of said resistance remote from said output terminal to the cathode of said control tube, a lead connecting the grid of said control tube to a portion of said resistance remote from the terminal thereof connected to said neon tube, a lead connecting the anode of said control tube to the control grid of said regulator tube, and means for applying a positive voltage to the cathode of said control tube and a more positive voltage to the anode thereof.

4. An analytical instrument comprising, in combination, a power transformer having a primary winding and a secondary winding, means for supplying line voltage to said primary winding, a rectifier bridge defined by four fused germanium diodes connected to the secondary winding of said transformer, a filter connected to said rectifier and comprising a series choke of low inductance and a plurality of parallel condensers of high capacitance, a regulating tube having at least an anode-cathode control grid, first and second output terminals, means for connecting said regulating tube in series between said filter and said first terminal, hydrogen discharge lamp connected between; said output terminals, said lamp forming the sole connection between said terminals, a control tube having at least an anode, a cathode, and a control grid, a resistance having one terminal thereof connected to the second of said output terminals, a neon tube connecting the terminal of said resistance remote from said output terminal to the cathode of said control tube, a lead connecting the grid of said control tube to a portion of said resistance remote from the terminal thereof connected to said neon tube, a lead connecting the anode of said control tube to the control grid of said regulator tube, means for applying a positive voltage to the cathode of said control tube and a more positive voltage to the anode thereof, a photoelectric cell arranged to receive a beam of radiation from said hydrogen lamp, an amplifier-recorder unit connected to said photoelectric cell, a sample cell positioned in the path of said beam, means for feeding a sample to said cell and Withdrawing said sample therefrom, and a rotatable chopper in the path of said beam.

5. In a current regulating power supply that includes, in combination, a series circuit having a source of alternating current, a rectifier connected thereto, a filter connected to said rectifier, a regulator tube connected to said filter and including at least an anode, a cathode, and a control grid, and a pair of output terminals having one terminal thereof connected in series with said regulator tube and the other terminal thereof electrically iso lated therefrom, the improvement comprising an impedance having a first terminal thereof connected to said other output terminal; a control tube having at least an anode, a cathode, and a control grid; a discharge device connected between the cathode of said control tube and a second terminal of said impedence; a lead connecting the control grid of said control tube to said first terminal of said impedence; means for impressing an operating voltage upon said discharge device; and means for applying a control voltage from the anode-cathode circuit of said control tube to the control grid of said regulator tube.

6. The power supply of claim 5 further including a hydrogen discharge lamp connected between said pair of output terminals.

7. A current regulating power supply according to claim 5 wherein said impedence comprises a plurality of fixed resistances of low temperature coetlicient, and a switch arranged to select one of said fixed resistances for operation by placing one of said resistances in series be tween said discharge device and said other output terminal.

References Cited in the file of this patent UNITED STATES PATENTS 2,286,985 Hanson June 16, 1942 2,318,644 'Iubbs May 11, 1943 2,468,638 Rosenbaum Apr. 26, 1949 2,579,816 Gluyas Dec. 25, 1951 2,624,039 Jorgensen Dec. 30, 1952 2,654,845 Presenz Oct. 6, 1953

Images