US2490063A - Voltage regulator circuit - Google Patents

Description

. 6, 1949 w. L. KINSELL VDLTAGE REGULATOR CIRCUIT Filed June 14, 1947 INVENTOR WILLIAM L. KINSELL ATTORNEY reamed Doc. a, 1949 UNITED STATES PATENT OFFICE VOLTAGE REGULATOR CIRCUIT m a m srxmasa m "a Corporation, a corporation of Indiana Application June 14, 1947, Serial No. 754,757

6 Claims, (Cl. 323-41) This invention relates to regulated power supplies and particularly to a voltage regulator circuit wherein the output voltage rises slowly to the predetermined value to prevent damage of the load fed by the regulator.

A conventional voltage regulator comprises a rheostat tube connected in series with a direct current supply and the load. The rheostat tube is controlled by a high gain amplifier responsive to variations of the output voltage. The regulator action accordingly depends on the control tube which varies the grid bias of the rheostat tube and hence the current flowing through the load. The direct current supply conventionally consists of a full wave rectifier and a filter network which supply the unregulated power. when the full wave rectifier circuit is turned on, it will heat up almost instantaneously and supply the full power to the rheostat tube. The rheostat tube in turn may be a directly heated tube which will also heat up practically instantaneously. Alternatively, the recently developed GAS? tube may be used for the rheostat tube which, although indirectly heated, will also be operative in a comparatively short time. On the other hand, the control tube is a high gain amplifier such as a pentode which will require an interval of time of the order of ten seconds before it becomes effective to control the rheostat tube.

Consequently, when the power is turned on, the output voltage developed by a conventional voltage regulator will initially be considerably higher than the desired value which may damage the load. The load of a voltage regulator frequently consists of amplifier tubes which are easily damaged when too high a voltage is applied thereto. It is accordingly desirable to provide a voltage regulator having an output voltage which rises slowly until the control tube becomes effective for controlling the current through the rheostat tube.

It is an object of the present invention. therefore, to provide an improved voltage regulator circuit.

A further object of the invention is to provide a voltage regulator of the type having a rheostat tube controlled by a high gain amplifier tube responsive to variations of the output voltage, with a time delay circuit to prevent a too rapid rise of the output voltage when the regulator 2 is turned on which might damage the load fed by the regulator.

In accordance with the present invention there is provided a voltage regulator comprising a direct current supply, a load and a rheostat tube for regulating the voltage of the supply and connected in series with the direct current supply and the load. The rheostat tube has a control element. There is further provided a control tube responsive to variations of the voltage across the load. The control tube has an output electrode. The output electrode of the control tube is connected to the control element of the rheostat tube. Furthermore, there is provided a time delay circuit. Finally means is provided for coupling the time delay circuit.to the control element of the rheostat tube. The time delay circuit accordingly functions to delay the current fiow through the rheostat tube until the control tube becomes efiective to control the voltage across the load.

For a better understanding of the invention, together with other and further objects thereof, reference is made to the following description.

taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

The single figure of the drawing is a schematic circuit diagram of a voltage regulator embodying the present invention.

Referring now to the drawing, there is shown a voltage regulator comprising a direct current source such as a full wave rectifier circuit. Transformer I has a primary winding 2 which is connected to an alternating current source as indicated through a switch 3. Full wave rectifier tube 4 has its anodes connected to secondary winding 5, the mid point of which is connected to ground through lead IS. The cathode of full wave rectifier tube 4 is directly heated by secondwave rectifier circuitand a loadsch indicated at H. Rheostat tube-i6 its shod connected to filter network I while its cathodes are connected to load" '1'. Thetwoeontrolit of rheostat tube |6 areconnected together and control the current flowthrough tube. It.

Rheostat tube I6 is controlledby a -eontrol tube which, as illustrated, may be a pentode or any other high gain amplifier tube. Control tube 2|! comprises cathode 2|, control grid 22, screen grid 23, suppressor grid 24 and anode 26. Anode 26 is connected to control grids ll of rheostat tube l4. For the purpose of controlling control tube 24 in accordance with the variations of the voltage across load I! there is provided a potentiometer including resistors 26, 21 and 26 connected in series across load II. Control grid 22 is connected by lead 23 to adjustable tap on resistor 21. Condenser 3| shunts leads l4 and 23, that is resistor 26 and that portion of resistor 21 arranged between resistor 26 and adjustable tap 36.

Control tube 20 is also made responsive to the voltage variations across filter network I. To this end there is provided another voltage divider including resistors 32 and 33 and voltage regulator tubes 34 and 35 connected in series across leads l4, l5. Voltage regulator tubes 34, 35 may be gas-filled diodes such as glow discharge tubes having a constant voltage drop thereacross. Screen grid 23 of control tube 20 is connected to adjustable tap 36 on resistor 33.

Cathode 2| of control tube 20 is connected to the junction point of voltage regulator tubes 34 and 35, while suppressor grid 24 is tied to cathode 2|. Cathode 2| of control tube 20 may be indirectly heated by a filament 31 connected to secondary winding 38 of transformer I having one of its terminals grounded. The cathodes of rheostat tube It may also be indirectly heated through secondary winding 40 of transformer l which has its center point grounded as illustrated.

In accordance with the present invention there is provided a time delay network consisting oi the series combination of resistor 4| and condenser 42 connected across load II, that is, in parallel to voltage divider 26, 2'! and 23. Resistor 43 connects the junction point. of resistor 4| and condenser 42 to the junction point of anode 25 of control tube 20 and control grid l8 of rheostat tube I6.

The voltage regulator of the invention operates as follows. The full wave rectifier circuit including rectifier tube 4 develops a unidirectional current which is filtered by filter network I. The amount of current flowing through rheostat tube l6 and accordingly through load I! is determined' by the bias of its control grids l6. This bias is controlled, as is conventional, by the current flowing through control tube 20. Assume, for example, that the voltage across load I1 is reduced below the desired value due either to an increase of the current through load ll or due to a decrease of the voltage impressed upon the primary winding 2. Accordingly, the voltage on adjustable tap 30 will be reduced so that less current flows through control tube 20. Consequently, the voltage drop across resistors 4| and 43 is reduced which increases the bias of control grids l8 and permits more current to flow through rheostat tube l6.

In the same manner control tube 20 is also responsive to variations 0! the voltage derived fitter network 3.. .rissume that the cunt voi'tege oi the full. waverectifier circuit is re,

- duced. The voltage drop across resistors 82 t re duce the potential'or screen'd 23;

iii-i iseccogly reduced which have the same siiiect asipreviouslyndcscribed so that the current through rheostate tube it is remains assistant; 7

By adjusting tap at, the regulator action of the circuit may be adjusted to zero or may even be made negative. Voltage regulator tube 34 serves the purpose of impressing a constant voltage between screen grid 23 and cathode 2| of control tube 20 to which is added a variable voltage which may then be adjusted by movable top 36 to obtain the desired regulation action. As pointed out hereinbefore, full wave rectifier tube 4 and rheostat tube l6 will become operative almost instantaneously while control tube 20, which is a pentode, requires more time before it becomes eflective for controlling the current through rheostat tube l6. Accordin ly. immediately after switch 3 has been closed to supply power to the voltage regulator, a fairly high output voltage would ordinarily be developed across load H. In order to provide for a slow rise 0! the output voltage, the time delay circuit consisting of resistor 4| and condenser 42 is provided in the circuit of control grids iii of rheostat tube l6. The time constant of resistor 4| and condenser 42 may, for example, be of the order of two seconds.

As long as no power is applied to the voltage regulator, condenser 42 will be discharged and control grids l8 will accordingly be at ground potential. When switch 3 is closed, the full voltage developed by the rectifier circuit is applied to the anodes of rheostat tube l6. Since its control grids l8 are initially at ground potential, only a small current can flow through rheostat tube I6 which will slightly increase the potential of condenser 42. In view of the degenerative action of the time delay circuit 4|, 42, it will require approximately between 15 and 20 seconds before the potential of control grids I8 is raised to its normal operating value. During that time, control tube 20 has become fully operative for controlling the current through rheostat tube H5 in the manner previously described. The .voltage regulator of the present invention accordingly provides a simple and effective circuit which will prevent damage of the load when the voltage regulator is turnedon.

The output voltage supplied to load l1 may be adjusted .by tap 30. Adjustment of tap 30 will change the voltage between cathode 2| and control grid 22 of control tube 20 which must be kept within very narrow Accordingly, control tube 20 will regulate the current through rheostat tube |6 until the potential between cathode 2| and control grid 22 is again at the value required for the operation of the tube, and consequently this will adjust the output voltage within certain limits.

While it will be understood that the circuit specifications of the voltage regulator of the invention may vary according to the design for 7 any particular application, the following circuit specifications for a voltage regulator are included, by way of example only, as suitable for an output voltage variable between 200 and 350 volts and a maximum continuous output current of milli-amperes with a 60 cycle alternating iii see, and consequently, the output. voltage input voltage which may vary between 90 and 130 volts:

Full wave rectifier tube 4 5H4 Rheostat tube I0 6A8! Control tube 6SJ7 Voltage regulator tube 34 VR75 Voltage regulator tube 35 VR'75 Output voltage of secondary r heater winding 38 6.3 volts Output voltage of secondary heater winding 40 6.3 volts Choke coil 8 150 milli-henries Choke coil l0 150 milli-henries Filter condenser .Il 4 microfarads Filter condenser l2 4 microfarads Filter condenser l3 4 microfarads Resistor 32 15,000 ohms Resistor 33 10,000 ohms Resistor 4| 1,000,000 ohms Condenser 42 2 microfarads Resistor 43 560,000 ohms Condenser 3| .1 microfarad Resistor 2G 47,000 ohms Resistor 21 100,000 ohms Resistor 28 27,000 ohms While there has been described what is at pres ent considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A voltage regulator comprising a direct current supply, a load, a rheostat tube for regulating the voltage of said supply and connected in series with said supply and said load, said rheostat tube having a control element, a control tube responsive to variations of the voltage across said load and having a cathode, an anode and a control grid, a voltage divider connected across said load, said control grid and cathode being coupled to said voltage divider, said anode being connected to said control element, a time delay circuit coupled to the output of said rheostat tube and including a first impedance element and a charge storage element, and means for coupling the junction point of said first impedance element and said charge storage element to said control element, thereby to delay the current fiow through said rheostat tube until said control tube becomes efiective to control the voltage across said load.

2. A voltage regulator comprising a direct current supply, a load, a rheostat tube for regulating the voltage of said supply and connected in series with said supply and said load, said rheostat tube having a control element, a control tube responsive to variations of the voltage across said load and having a cathode, an anode and a control grid, a voltage divider connected across said load, said control grid being connected to a tap on said voltage divider, means coupled to said supply for maintaining said cathode at a predetermined potential, said anode being connected to said control element, a time delay circuit connected in parallel to said voltage divider and including a first impedance element and a condenser, and a second impedance element connected between the junction points of said first impedance element and condenser and of said anode and control element, thereby to delay the current flow through said rheostat tube until said control tube becomes effective to control the voltage across said load.

3. A voltage regulator comprising a direct current supply, a load, a rheostat tube for regulating the voltage or said supply and connected in series with said supply and said load, said rheostat tube having a control element, a high gain control tube responsive to variations of the voltage across said load and having a cathode, an anode and a control grid, a voltage divider connected across said load, said control grid being connected to an adjustable tap on saidvoltage divider, a constant voltage drop diode coupled to said supply for maintaining said cathode at a predetermined potential, said anode being connected to said control element, a time delay circuit having a predetermined time constant and by-passing said load, said circuit including a first resistor and a condenser connected in series, and a second resistor connected between the junction points of said first resistor and condenser and of said anode and control element,

- thereby to delay the current flow through said rheostat tube until said control tube becomes efiective to control the voltage across said load.

4. A voltage regulator comprising a direct current supply, a load, a rheostat tube having a control element and connected in series with said supply and said load for regulating the voltage of said supply, a first voltage divider connected across said load, a second voltage divider connected across said supply, a control tube having a cathode, an anode, a control grid and a screen grid, said anode being connected to said control element, said control grid being connected to a tap on said first voltage divider, said screen grid being connected to a tap on said second voltage divider, means coupled to said supply for maintaining said cathode at a predetermined voltage, whereby said control tube is responsive to voltage variations across said supply and across said load, an impedance element and a condenser connected in series across said load and having a predetermined time constant, a resistor connected between the junction points of said impedance element and condenser and of said anode and control element, thereby-to delay the current fiow through said rheostat tube until said control tube becomes fully effective to control said rheostat tube.

5. A voltage regulator comprising a direct current supply, a load, a rheostat tube having a control element and connected in series with said supply and said load for regulating the voltage of said supply, a first voltage divider connected across said load, a second voltage divider and a constant voltage drop tube connected across said supply, a control tube having a cathode, an anode, a control grid and a screen grid, said anode being connected to said control element, said control grid being connected to a tap on said first voltage divider, said screen grid being connected to a tap on said second voltage divider, said cathode being connected to the junction point of said second voltage divider and said constant voltage drop tube, whereby said control tube is responsive to voltage variations across said supply and across said load, a first resistor and condenser connected in series across said load and having a predetermined time constant, a second resistor connected between the junction points of said first resistor and condenser and of said anode and control element, thereby to delay the current flow through said rheostat tube until said control tube becomes fully eflective to control said rheostat tube.

6. A voltage regulator comprising a direct current supply, a load, a rheostat tube having a control element and connected in series with said supply and said load for regulating the voltage of said supply, a first voltage divider connected across said load, a second voltage divider and a first and a second constant voltage drop diode connected across said supply, a high gain control tube having a cathode, an anode, a control grid and a screen grid, said anode being connected to said control element, said control grid being connected to an adjustable tap on said first voltage divider, said screen grid being connected to an adjustable tap on said second voltage divider, said cathode being connected to the junction point of said diodes, whereby said control tube is responsive to voltage variations across said supply and across said load, a first resistor and condenser connected in series across said load and 8 having a predetermined time constant. a second resistor connected between the junction points of said first resistor and condenser and of said anode and control element, thereby to delay the current flow through said rheostat tube until said control tube becomes fully eflective to control said rheostat tube.

- WILLIAM L. KINSEIL.

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

UNITED STATES PATENTS Number Name Date 2,210,394 Braden Aug. 6, 1940 2,275,165 Wasserman Mar. 3, 1942 2,301,343 Tarr Nov. 10, 1942 2,316,577 Ford Apr. 13, 1943 2,377,500 Johnson June 5, 1945 2,433,702 Mayle Dec. 30, 1947

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