US2424214A

US2424214A - Unidirectional voltage generator

Info

Publication number: US2424214A
Application number: US540567A
Authority: US
Inventors: John A Buckbee
Original assignee: Farnsworth Television and Radio Corp
Current assignee: Farnsworth Television and Radio Corp
Priority date: 1944-06-16
Filing date: 1944-06-16
Publication date: 1947-07-22
Anticipated expiration: 1964-07-22

Description

July 22, 1947. J, BUCKBEE 2,424,214

UNIDIRECTIONAL VOLTAGE GENERATOR Filed June 16, 1944 FIG. l

20 DZ i- 29 /|9 L Eg/ T25 FIG. 2 '-'|'|ME INVE NTOR JOHN A'.' BUCKBEE ATTORNEY Patented July 22, 1947 UNIDIRECTIONAL VOLTAGE GENERATOR John A. Buckbee, Fort Wayne, Ind., assignor to Farnsworth Television and Radio Corporation, a corporation of Delaware Application June 16, 1944, Serial No. 540,567

9 Claims. (Cl. 17197) This invention relates to power supply apparatus and particularly to apparatus of this character wherein the supply voltage is divided among a, plurality of loads.

In the operation of multistage electron multipliers it is the conventional practice to derive the accelerating voltages for the secondary electron emissive multiplier electrodes from a voltage divider which is connected across a. source of direct current energy. The voltage which is developed in each divider component is dependent upon the total current flow in that component. The total current flow consists of the circulating current through the divider component from the energy source and the electron current flow between the associated multiplier electrodes. Where it is desired that the multiplier have a substantially linear response, it is necessary that the interelectrode accelerating voltages be maintained at substantially constant values. In order to effect this result the circulating current through the respective voltage divider components must be considerably greater than the associated inter electrode electron current. In this manner fluctuations of the electron current due to signal variations have little or no eifect upon the voltage drop in the respective divider components. In order to achieve this end with a voltage divider consisting of equal impedance components, the components must have relatively low values of impedance.

However, as is well known in the art, a voltage divider made up entirely of relatively low impedance components consumes considerable power from the source of energy. Inasmuch as the voltage developed in some of the divider components is not subject to appreciable variation by reason of variations of the electron current flow between the associated multiplier electrodes, it is not necessary that the impedances of these divider components be of relatively small values. Such a condition is particularly true in the initial multiplier stages where the magnitude of the electron current flow is comparatively small. I

It, therefore, has become the practice to employ a voltage divider consisting partly of a group of relatively low impedance components and partly of a group of relatively high impedance components. One such arrangement is disclosed in a copending application of Donald R. Rasley, Serial No. 512,541, filed December 2, 1943. The relatively, high impedance divider components are used in association with those multiplier stages where the electron current densities are relatively small and the relatively low impedance divider components 55 are used in association with those multiplier stages where the electron current densities are relatively large. In this manner it is possible to provide accelerating voltages for the electron multiplier stages which are substantially constant, irrespective of fluctuations in the electron current densities representing intelligence signals and at the same time to minimize the consumption of power from the source of energy for the voltage divider.

Inasmuch as the energy source most conveninetly used with apparatus of the character described consists of rectified alternating current energy, it becomes necessary to adapt such a power supply suitably to provide energy to a load consisting of both relatively high and low impedance elements. 'For certain television applications the source of alternating current energy from which the unidirectional power supply is derived also serves as the source of scanning voltage for the deflector elements. Devices of this character used heretofore have been required to deliver unidirectional energy to only one load.

It, therefore, is an object of the present invention to provide a novel power supply for a load circuit consisting of a plurality oi impedance elements.

In accordance with this invention, there are provided a source of impulses and a load circuit including the series connection of a plurality of impedance devices. Additionally, there is pro vided a. voltage multiplier of which the high voltage terminals are connected to the terminals of the load circuit. An intermediate terminal of the voltage multiplier is coupled both to the source of impulses and to the junction point between two 01' the load circuit impedance devices. More specifically, the voltage multiplier may be that type of device known as a voltage doubler.

For a. better understanding of the invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

In the accompanying drawing:

Fig. 1 is a circuit diagram of apparatus embodying the present invention; and,

Fig. 2 is a group of curves illustrating the mode of operation of the apparatus of Fig. 1.

Having reference now particularly to Fig. 1 of the drawing, the source of impulses is a relaxation oscillator including a vacuum tube ii. The anode of this tube is connected through an inductive winding suchas a coil I 2 to the positive terminal of a source of direct current energy such as a battery i2. The negative terminal of this battery is connected to ground. The cathode of the tube is connected. through a resistor l4 to ground. The control'grld i5 of the oscillator tube is connected through a coil ii to ground. The coils i2 and iii are inductively coupled in such polarity that the relationship is regenerative. The screen grid H of the oscillator tube is connected through a resistor i2 to the positive terminal of the battery i2.

The load circuit for the device comprises the series connection of a relatively high impedance device such as a resistor i9 and a relatively low impedance device such as a resistor 2|. One terminal of the resistor 2| is connected to ground. The anode of oscillator tube ii is coupled by an energy storage device such as a condenser 22 through a choke coil 22 to the junction point 24 between the load resistors l9 and 2|. The resistor 2| is shunted by a condenser 25. The choke coil 23 and condenser 25 comprise a filter for a purpose subsequently to be described. A rectifier tube 26 is connected with its anode to the junction point of the condenser 22 and the choke coil 23. The cathode of the rectifier tube is connected to ground. A condenser 21 is connected between ground and the terminal 22 of the load resistor IS. A rectifier tube 22 is provided with its anode connected to the terminal 28 of the resistor is and with its cathode connected to the anode of the rectifier tube 26.

Referring now to the operation of the apparatus comprising the unidirectional power supply in accordance with this invention, a brief consideration will be given to the operation of the relaxation oscillator as a source of impulses. During conducting periods of the tube when the current is increasing through the space discharge path of the tube and through the anode coil i2, the voltage induced in the control grid coil i8 impresses a voltage upon the control grid i5 suitable to maintain conduction in the tube. At the same time the anode voltage oi! the oscillator tube is maintained at a substantially constant value. When a critical interelectrode potential condition within the tube ii is reached. the current increase through the tube and the coil i2 ceases and this current flow begins to decrease in magnitude. By reason of the fact that the current decrease through the coil I2 induces a voltage of opposite polarity in the coil ii, the control grid I5 is driven more negative than the space current cutoff value. Thus, the current decay in the coil i2 and the tube l is at a relatively rapid rate as compared with the rate of increase, and as a result the current flow soon is completely interrupted. The described cycle of operation then is repeated.

During periods of current decay in the coil i2 and in the tube ii the voltage at the anode increases positively to a relatively high value. Since these periods are of relatively short durations there thus is developed at the anode of the oscillator tube a series of voltage impulses.

In considering the manner in which these impulses are utilized to develop two unidirectional voltages for impression upon load circuitsot different impedance, assume that the

condensers

22 and 21 are completely charged at the termination of one of the voltage impulses. During the time that the anode of the tube ii is maintained at the described constant value the energy stored in the condenser 22 is slowly dissipated through the relatively low impedance of the resistor 2|. Also, during this period the energy stored in the condenser 21 i dissipated also at a relatively slow rate through the load resistors i2 and 2|. The dissipation rates of the respective condensers are determined by the time constants of the dissipation circuits. These constants are a function of the values of each condenser and its associated load resistor. In the case of the dissipation circuit for the condenser 21 the resistor 2| has negligible effect upon the determination of the time constant for the reason that it is of a relatively low order of magnitude as compared with the resistor l9.

Immediately after the termination of one of the voltage impulses, the potential of the anodes of the

rectifier tubes

22 and 22 are considerably negative with respect to their associated cathodes. These conditions are illustrated in Fig. 2, wherein the trace 2| represents the variation of the voltage at the point 24 of the load circuit and the trace 22 represents the variation 0! the voltage at the point 22 of the load circuit. These two voltages also correspond substantially to the respective voltages appearing at the anodes o! the

rectifier tubes

22 and 22. The dissipation of the energy stored in the condenser 22 during the periods between impulses is illustrated by the exponentially curved portion 22 of the trace 2|. Similarly, the dissipation of the energy stored in the condenser 21 during these periods is illustrated by the exponentially curved portion 24 of the trace 22. It is seen that in both instances the negative voltages appearing at the load points 24 and 22 gradually are decreased. As a result of the development of these negative voltages, the respective anodes of the

tubes

22 and 22 are maintained at negative potentials with respect to their associated cathodes. Neither of these tubes. therefore, is conditioned for conduction.

The impression 01! one or the positive impulses developed at the anode of the oscillator tube ll upon the condenser 22 immediately changes the potential of the anode of the rectifier tube 22 from some negative value to ground potential. This change is illustrated by the rectangular impulsive portion 25 of the trace 2|. The rectifier thus becomes conducting and energy derived from the impulse is stored in the condenser 22. During the impulse period no change is eflected with respect to the rectifier tube 22. The condenser 21 continues to dissipate some or its stored energy through the load resistors i2 and 2|.

Immediately upon the termination of the impulse, the voltage of the point 24 in the load circuit is abruptly changed to its most negative value represented by the point 26 on the trace 2|. As soon as this voltage change is eflected, the anode of the rectifier tube 22 immediately becomes more negative than the cathode 0! this tube and the tube ceases to conduct. Also, as an imme e c s quence of the change 01 voltage at the load point 24 the cathode of the rectifier tube 29 becomes more negative than its associated anode. The tube 28 thus is conditioned for conduction to store energy in the condenser 21. The time requiredfor this operation is extremely short. As a result. the volttage of the condenser and also that of the anode of the tube 29 and the point 22 o! the load circuit is changed to the voltage of the load point 24 which at this time is at its most negative value illustrated by the point 26 on the trace 2|.

For the purpose of illustrating the voltage changes during the charging period of the condenser 21, the trace 32 is displaced slightly in time from the trace 2|. It is to be understood that the relationship between the traces 2| and 22 during the interval immediately succeeding the termination 01' one oi the oscillator developed impulses is much exaggerated. The volt,- age change of the point 28 in the load circuit from the negative value represented by the point I! on the trace 22 to its most negative value illustrated by the point 38 on this trace occurs substantially simultaneously with the depression of the voltage of the load point 2| to the negative value illustrated by the point 38 on the trace 8|. The described cycle of operation is then repeated.

It is readily apparent from Fig. 2 that the average value of the load point 24 is maintained considerably negative with respect to ground. Also, it is evident that the average value 01' the voltage at the load point 28 is maintained at a negative polarity not only with respect to ground but also with respect to the average value or the negative potential at the point 24 of the load circuit.

The choke coil 22 with its associated filter condenser 25 prevents the feedback of energy from the load circuit to the oscillator circuit. In this manner the functioning of the relaxation oscillator is not afiected by voltage changes occurring in the load circuit during the periods when the energy stored in the

condensers

22 and 21 is being dissipated through the load resistors 18 and 2|.

Instead oi connecting the condenser 21 to ground, as shown, it may be connected alternatively to the junction point between the cathode and anode of the

rectifier tubes

22 and 28, respectively. Also. it is considered to be within the scope 01' the instant invention to connect additional stages to the disclosed apparatus. Each one of such additional stages would be similar to that including the resistor II, the condenser 21 and the rectifier tube 28. The connections required would be similar to those shown.

The values 01' the various circuit components instrumental in the development of the unidirectional power supply depend in some measure upon the voltage and load requirements of apparatus to be supplied with unidirectional voltages. Without intending to limit the present invention, the following table of values for the essential circuit components of a device in accordance with this invention is given by way 01' example. A 'source producing impulses at the rate of approximately 14,000 per second is used to supply energy at approximately 1500 volts with a current drain or approximately 0.8 miliiampere in a relatively high impedance resistor of 1,880,000 ohms and at approximately 1000 volts with a current drain or 7 milliamperes in a relatively low impedance resistor oi 140,000

ohms.

Resistor ll 1,880,000 ohms Resistor 2| 140.000 ohms Condensers 22 and 2| 0.001 microiarad Choke coil 23 0.5 henry Rectifier tube 26 i. 6x5 both sections in parallel Condenser 2'| 0.008 microtarad Rectifier tube 28 8016 While there has been described what, at present, is considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifica tions may be made therein without departing from the invention, and therefore. it is aimed values-and a voltage doubler and scope oi the invention.

. .6 in the appended claims to and modifications as tall cover all such changes What is claimed is:

1. A unidirectional power supply comprising, a source of impulses, a load circuit including the series connection of a plurality of impedance devices, and a voltage multiplier having the high voltage terminals thereof connected to the terminals of said load circuit and an intermediate terminal thereof coupled to said source of impulses and to the Junction point between two of said impedance devices.

2. A unidirectional power supply comprising, a source of impulses, a load circuit including a series connection of two impedance devices of different having the high voltage terminals thereof connected to the terminals of said load circuit and an intermediate terminal thereof coupled to said source of impulses and to the Junction point between said load impedances.

3. A unidirectional power supply comprising, a source of impulses, a load circuit including the series connection of two impedance devices, a voltage doubler having the high voltage terminals thereof connected to the terminals of said load circuit and an intermediate terminal thereof coupled to said source of impulses, and means including a filter network for coupling the intermediate terminal 01' said voltage doubler to one of said impedance devices.

4. A unidirectional power supply comprising, a source of impulses, a plurality of 'energy storage devices, one 01' said storage devices being connected to said impulse source, a plurality of energy dissipation circuits connected respectively to said energy storage devices, means operative under the control and for the duration of said impulses ior efiecting the storage of energy in said one storage device, and means operative in response to the inoperative conditioning oi said first named means for ei'lecting the storage of energy in another one of said storage devices.

5. A unidirectional power supply comprising, a source of impulses, first and second condensers, said first condenser being connected to said impulse source, two energy dissipation circuits connected in series and also connected respectively to said condensers, means operative under the control and for the duration of said impulses ior efiecting the storage oi energy in said first condenser, and means operative in response to the inoperative conditioning of said first named means for efi'ecting the storage of energy in said second condenser.

6. A unidirectional power supply comprising, a source of impulses, first and second condensers, said first condenser being connected to said impulse source, two energy dissipation circuits of difierent impedance values connected in series and also connected respectively to said condensers, means including a first rectifier operative under the control and for the duration of said impulses for efi'ecting the storage of energy in said first condenser, and means including a second rectifier operative in response to the inoperative conditioning oi said first rectifier for efi'ecting the storage oi energy in said second condenser.

7. A unidirectional power supply comprising, a source of impulses, a load circuit including the series connection of two impedance elements 01' diflerent values, a first condenser connected between a terminal of one oi said impedance elements and said impulse source, a second condenser connected to a terminal of the other of said imwithin the true spirit 7 pedance elements, and two rectifiers connected respectively in parallel with said impedance elements.

8. A unidirectional power supply comprising. a relaxation oscillator having an output circuit for the development of a series of impulses, a load circuit including the series connection of a relatively high impedance element and a relatively low impedance element, a first condenser connected between one terminal of said relatively low impedance element and said output circuit, a second condenser connected to one terminal of said relatively high impedance element, a first rectifier connected in parallel with said relatively low impedance element,'and a second rectifier connected in parallel with said relatively high impedance element.

9. A unidirectional power supply comprising, a relaxation oscillator having an output circuit for the development of a series of voltage impulses, a load circuit including the series connection of a relatively high impedance element and a relatively low impedance element, a first condenser REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PAIENTS Number Name Date 2,179,447 Dome 1307. l, .1939 2,179,448 Dome Nov. 7, 1939