US2745022A - Voltage regulator - Google Patents

Description

May 8, 1956 J SNYDER 2,745,022

VOLTAGE REGULATOR Filed Jan. 5, 1954 SECOND (men) CURRENT VOLTAGE SUPPLY -0 FIRST (LOW) CONTROL 22 VOLTAGE SUPPLY LOAD DETECTOR O- '2 FIG I \26 INVENTOR.

JAMES SNYDER ATTORNEY United States Patent VOLTAGE REGULATQR James Snyder, Asbury Park, N. J assignor to the United States of America as represented by the Secretary of the Army Application January 5, 1954, Serial No. 402,417

Claims. (Cl. 307-43) (Granted under Title 35, U. 5. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment of any royalty thereon.

This invention relates to voltage regulators and more particularly to means for controlling a low voltage supply.

The voltage regulation systems well known in the art usually rely on a variable resistance in the form of a vacuum tube between the source of voltage and the load to supply a substantially constant current or voltage to a given load. Other systems include applying the variable resistance tube in parallel with the load to draw more or less current through a common series resistor from the power supply to compensate for variations in the load or power supply. These systems are generally applicable to high voltage power supplies since they require a substantial voltage in excess of the voltage on the load as part of the control circuit and to be within the useful range of the control of the vacuum tube.

The problems of control of a low voltage are much more difiicult since the current is comparatively greater for the voltage involved and the current may be excessive for a vacuum tube while the voltage may not be great enough to operate the vacuum tube. The voltage regulating circuit of this invention uses a series resistor connecting the load to the low voltage power supply. This series resistor is effectively a volta e source since it is included in a second variable electronic circuit which need only supply the necessary current or voltage to compensate for the changes in the load. A variation of this circuit includes a bridge rectifier in place of or in conjunction with the voltage dropping resistor in series with the load. An alternating current controlled by the variations in voltage across the load is applied through the bridge to compensate for the changes in the voltage acres the load.

It is, therefore, an object of this invention to provide a voltage regulator.

It is a further object of this invention to provide a means in series with a load for compensating for the variations in the supply of voltage or current to the load.

It is a further object of this invention to provide a voltage regulator circuit applicable to low voltages.

It is a further object of this invention to provide a voltage regulating circuit that does not draw power back from the voltage supply being regulated.

Other and further objects of this invention will become apparent from the following specification and the drawings of which:

Figure 1 shows the basic concept of this invention in block diagrammatic form; and

Figure 2 shows a typical circuit for accomplishing the low voltage regulation.

Referring now more particularly to Figure l, a low voltage supply across terminals 1d and 12 provides energy through resistance 14 for a load 16. A second voltage supply which may be of substantially higher voltage than the first is applied across terminals 20 and 22 through the .dropping resistor 14 and a current control 24. The load 2,745,022 Patented May 8, 1956 voltage actuates the detector 26 which regulates the current control 24.

In operation a variation in the voltage across the load 16, which may be the result of a variation in the internal impedance of the load or a variation in the voltage of the first voltage supply, applies a signal to the detector 26 which may be the grid of a vacuum tube or any of several means, well known in the art, sensitive to variations in voltage or current. For critical purposes the variations detected may be amplified in voltage or in power to provide a stronger signal for a more precise control of the current from the second voltage supply. The current control 24 causes more or less current to flow through the resistance 14 which indirectly adds or subtracts to the voltage across the load 16 until its correct operating voltage is restored to rebalance the detector.

In Figure 2 the resistance 14 may be replaced by rectifier bridge 30, although a variable resistance 32 may also be provided, in series with the load 216 across the low voltage supply 210 and 212. In this circuit the detection and current control is realized by a sampling circuit which transfers the variation in voltage across the load to a proportional modulation of a relatively higher frequency alternating current. This is amplified and applied back to the bridge 30 to provide a voltage to compensate for any variation in the load.

In operation the voltage level across the load 216 is applied to the grid of tube 226 whose cathode circuit is keyed by the multivibrator 40 to gate or sample the signal. The output of tube 226 at 42 is an amplitude modulated envelope of the frequency of multivibrator 40. This is applied to tube 44 which may be biased by network 46 to increase the ratio of modulated to unmodulated signal. The output of tube 44 at 43 is passed through a second limiting circuit 50 including diode 52 to obtain a still greater percentage of the modulation of the multivibrator frequency across the tuned circuit 54. This is adjusted to thefrequency of the multivibrator and acts as a filter to provide a better waveform for the modulated frequency by reducing the peaks and harmonics of the original square waveform. The amplified and filtered modulation envelope is passed through tube 56 which is transformer coupled to push-pull stage 58 for power amplification. The output of the push-pull stage 58 is transformed in 60 to the level voltage to be applied across terminals 36 and 38 of bridge 30 which rectifies and applies D. C. voltage in series with the low voltage supply.

In operation the variations in voltage across the load 216 are transformed into modulated high frequency energy to be amplified and filtered and applied back across the rectifier which adds or subtracts the necessary voltage to restore the voltage across the load to substantially its correct value.

While this circuit is useful primarily in low voltage circuits Where relatively few forms of voltage regulation of a satisfactory or adequate nature are available, it would be obvious to anyone skilled in the art that this form of voltage regulation could also be advantageously applied to high voltage systems.

The limiting factor in the voltage control is the stray or undesired feedback in the amplifier, particularly between the high and low level sections of an amplifier as shown in Figure 2; however, in practice with good shielding techniques a regulation of better than 1% can be achieved. The circuit of Figure 2 utilizing sampling techniques can provide regulation not only of alternating current variations but also of substantially direct current variations while still using relatively simple alternating current techniques of amplification. Having thus described my invention what is claimed is:

1. In a control for low voltages, below the normal operating potentials of vacuum tubes, a first low voltage supply, a voltage-dropping resistance, a load connected in series with said voltage-dropping resistance across said first voltage supply, a second low voltage supply, a current regulating device connected in series with said voltagedropping resistance across said second voltage supply, means for detecting the voltage variations across said load, said detecting means connected to said current regulatng device to vary the current of said second voltage supply through said voltage-dropping resistance to compensate for the variations in voltage across said load.

2. 'In a voltage regulator, a low voltage supply, a rectifier bridge, a load connected in series with one pair of arms of said rectifier bridge across said voltage supply, an alternating current source, means for modulating said alternating current source in accordance with the variations involtage across said load, means for coupling the modulated alternating current output to a second pair of arms of said bridge.

3. A low voltage supply, a rectifier bridge having a first and second pair of arms, a load connected in series with the first pair of arms of said rectifier bridge across said voltage supply, means for detecting variations in voltage across said load, an oscillator, said oscillator modulated by said detecting means, means for amplifying the modulated oscillations, means for transforming said modulated oscillations to a low impedance circuit, said low impedance circuit connected across the other two arms of said rectifier bridge to compensate for variations in voltage across said load.

4. In a voltage supply circuit as in claim 3, said oscillator being in the form of a multivibrator.

5. A low voltage supply, a load, a variable resistance, a rectifier bridge having a first two terminals connected in series with said variable resistance and said load across said voltage supply, a vacuum tube actuated by the voltage across said load, a multivibrator circuit connected to gate said vacuum tube, means for amplifying the output of said vacuum tube, means for increasing the proportion of modulation of the output of said vacuum tube, means for transforming the output of said vacuum tube to a lower impedance output, means for connecting the lower impedance output across a second two terminals and said rectifier bridge to compensate for the variations in voltage across said load.

References Cited in the file of this patent UNITED STATES PATENTS 1,893,767 Fitzgerald et al. Jan. 10, 1933 2,035,263 Cushman et al. Mar. 24, 1936 2,098,370 Bartels Nov. 9, 1937

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