US2499484A - Voltage rectifying circuit - Google Patents

Description

INVEN TOR.

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March 'i 1950 /gff //igm BY am AHORA/El l Patented Mar. 7, 1950 t UNITED STATES mulini' OFFICE y vorxraoa mime cmcurr l I Albert W. Friend,

Collingswood, J., assignor to Radio Corporation of America, a vcorporation of Delaware Application November 28, 1945, Serial No. 631,434 claims. (ci. 321-15) This invention relates generally to voltage rectifylng circuits and more particularly to voltage rectifying and multiplying circuits employing phototubes as voltage rectifying devices.

Voltage rectifying and multiplying circuits for delivering high voltages of the order of to 100 kilovolts to cathode ray, X-ray and electron microscope apparatus require the use of expensive, high-voltagc-insulated transformers which are relatively large in size and uneconomical in view of the relatively low power delivered by the circuit, since such load devices usually require currents of less than one milliampere. Voltage multiplying circuits provide means for developing a unidirectional voltage greater than the peak alternating voltage of the source. Such circuits frequently are employed when such high voltages are required that it is. impractical to utilize a transformer for developing the full output voltage, or when it is desired to derive sufcient output voltage to operate low power load devices from a line voltage source without the use of transformers. However, thek use of conventional thermionic rectifier tubes in voltage multiplying circuits requires the use of high-voltage-insulated thermionic cathode transformer supply windings in order that the cathode heaters or thermionic cathodes of the several cascaded thermionic rectiers may be operated at widely differing voltage levels with respect to the supply voltage source. Such conventional voltage multiplying circuits also require the use of power dissipating resistors in each cascaded stage of the circuit.

The instant invention contemplates the use of conventional high impedance phototuloes to replace the thermionic rectiers. and, if desired, the power dissipating resistors, of conventional voltage multiplying circuits. Thus, the high-voltage-insulated cathode energizing windings of such circuits may be eliminated with resulting economy and reduction of circuit size. The impedance of the vacuum type phototubes may be controlled selectively by means of radiation from a light source directed at each of the phototubes. The light source preferably should be of the incandescent type having high heat capacity so that the alternating current heating thereof may he `filtered effectively to produce continuous, substantially constant intensity, illuminationof the phototubes. Thus, for high voltage, low current 50 load devices the only apparatus required for deriving suitably high load voltage from the power line is a plurality of phototuhes serially connected in cascade with a plurality of capacitors in a manner whereby the voltage developed across 55 the several capacitors is effectively added and applied to the load circuit. The irradiating light source for the phototubes may be supplied directly from the alternating current source, or it may be connected thereto through a suitable low voltage transformer. If desired, light from the irradiating source may be impressed separately at the desired intensity on each ofthe phototubes by means of a plurality of light conduits comprising suitably shaped transparent rods of Lucite, glass or fused quartz, whereby the light may be directed substantially only upon the photos-sensitive elements of the phototubes.

Among the 'objects of the invention are to provide an improved'method of and means for rectiying alternating voltages. Another object is to provide an improved voltage multiplying circuit. An additional object is to provide an improved voltage rectifying or multiplying circuit employ- 20 ing phototubes as voltage rectifying devices. A

further object is to provide an improved voltage rectifying circuit employing phototubes as voltage rectifyng and resistive devices. A still further object is to provide an improved voltage 26 Yrectifying and multiplying circuit requiring no high-voltage-insulated transformer windings for energizing the rectifying devices. Another object is to provide an power voltage rectifier and multiplier circuit having selective control of circuit impedance. A further object is to provide an improved high voltage, low power rectifying and voltage multiplylng circuit employing phototubes as voltage rectiers and resistors, and including means for controlling the circuit impedance by selectively ccntrolling the irradiation of the phototubes.

The invention'will be described in greater detail by reference to accompanying drawings of which Figure 1 is a schematic circuit diagram of a conventional voltage multiplying circuit employing thermionic diodes as rectifying devices, Figure 2 is a schematic circuit diagram of a preferred embodiment of the invention, and Figure 3 is a schematic circuit diagram of a second embodiment of the invention. Similar reference characters are applied to similar elements throughout the drawings.

Referring to Figure 1 of the drawing, a conventional voltage multiplying rectier circuit utilizing thermionic diodes as rectifying devicesincludes an input transformer l having its primary winding 3 connected to input terminals 5, l to which is applied an alternating voltage derived from a power line. VThe transformer l includes a secondary winding t providing the desired improved high voltage, low.

de of said first diode -voltage increase in view of practical transformer design characteristics. The voltage derived across the secondary winding 9 of the transformer I is applied to the anode of a first diode rectifier II and through a first capacitor I3 to the cath- II. The cathode of the first diode II is energized from a first low voltage secondary winding I5 of a filament transformer I1, the primary winding I9 of which is connected to the alternating current input terminals 5 and 1.

The anode of the first diode II is connected through a second capacitor 2I to the anode of a second diode 23 and resistor 25. The remaining terminal of the first resistor 2l is connected to the cathode of the first diode II, and is also coupled through a third capacitor 21 to the cathode of the second diode 23. The cathode of the second diode 23 is energized from a second low voltage secondary winding 23 of the filament transformer I1.

Similarly the anode of the second dio connected through a fourth capacitor 3I to one 'terminal of a second resistor 33 and to the anode of a succeeding diode 35. The remaining terminal of the second resistor 33 is connected to the cathode of the second diode 23 and is coupled through a fifth capacitor 31 to the cathode of the succeeding diode 35. The cathode of the diode 35 is energized from a third low voltage secondary winding 39 of the filament transformer I1. The low voltage secondary windings I5, 29 and 39 of the filament transformer I1 require high voltage insulation between each other and from the primary winding I9 thereof, since the cascaded diode rectiflers are at increasingly high voltage levels with respect to each other and to the voltage source. The multiplied output voltage is derived from output terminals 4I, 43 which are connected, respectively, to the cathode of the last diode 35 and to the grounded terminal of the high voltage secondary winding 9 of the first transformer I.

In operation, the diodes II, 23 and 35 each conduct on positive half cycles of the alternating potential applied to each of them. Thus, a voltage substantially equal to the peak voltage derived across the high voltage secondary winding 3 of the first transformer I is developed across each of the capacitors I3, 21 and 31. Since these capacitors are effectively connected in series relation, the voltages developed thereacross are effectively added and are applied to the output terminals 4I and 43, whereby the output voltage is substantially equal to the peak voltage developed across the high voltage secondary winding 9 of the transformer I multiplied by the number of cascaded diode rectlfiers employed in the circuit. It should be understood that the first high voltage transformer I maybe omitted if the additional voltage multiplication provided thereby is not required.

Figure 2 shows a circuit employing a plurality of alternately oppositely polarized radiationresponsive high impedance vacuum type phototubes 45, 41, 49, 5I and 53 which replace respectively the diodes and resistors II, 25, 23, 33 and 35 of the voltage multiplying circuit described heretofore by reference to Fig. 1. Since the phototubes require no cathode excitation voltage, the filament transformer of the circuit of Fig. 1 is omitted. The high voltage developed across the secondary winding 9 of the input transformer I is applied to the serially-con- VAnected first phototube 45 and first capacitor I3` to develop thereacross a rectified voltage subto one terminal of a first denisstantially equal to the peak voltage developed across the high voltage transformer secondary winding 9. Similarly the serially-connected second capacitor 2I and third phototube 49 develop across the third capacitor 21 a second voltage equal to the peak voltage across the transformer secondary winding 9. The second oppositely- -polarized phototube 41 operates as a polarized resistor which completes the charging circuit of the third capacitor 21.

Similarly the fourth capacitor 3I and the fifth phototube 53 in conjunction with the oppositelypolarized fourth phototube 5I develop a voltage across the fifth capacitor 31 which is substantially equal to the peak voltage developed across the transformer secondary winding 9. Since the first, third and fifthcapacitors I3, 21 and 31 are effectively connected in series, the output voltage developed across the output terminals 4I and 43 is equal to the sum of the capacitor voltages, and thus is equal to three times the peak voltage across the secondary winding 9. The conductivity of each of the phototubes is selectively controlled by means of an incandescent lamp 55 which irradiates each of the phototubes at the desired light intensity. The incandescent lamp 55 is energized from a low voltage secondary winding 51 of the transformer I or from any other suitable voltage source. Preferably the incandescent lamp 55 should have a filament of high heat capacity so that the alternating current heating thereof may be effectively filtered to minimize illumination ripple. The illumination may be controlled, for example, by means of an adjustable tap 59 on the low voltage secondary winding 51 of the transformer I. The several phototubes also may be differently masked, not shown, to provide the desired control of illumination thereof for regulating the conductivity and impedance of each of the phototubes- The circuit of Figure 3 utilizes resistors 25 and 33 in place of the oppositely-polarized second and fourth phototubes 41 and 5I, respectively, of the circuit of Fig. 2. The operation of the circuit otherwise is identical to that of Fig. 2. with the exception that the light source 55 illuminates the phototubes 45, 49 and 53 through separate light conduits 6I, 63 and 65, respectively. The light conduits 6I 53 and 65 may comprise, for example, 4suitably shaped solid rods of Lucite, glass or fused quartz whereby light from the source 55 may be directed substantially only upon the radiation-responsive cathodes of the individual phototubes. The intensity of illumination irradiating each phototube may be separately controlled by suitable masking of the phototube or light conduit in any manner well known in the art.

Thus, the invention disclosed and claimed herein contemplates the use of high impedance, vacuum type phototubes as rectifiers and resistors in voltage rectifying and multiplying circuits. to provide an efficient, compact and economical circuit arrangement wherein the impedance or conductivity of the several phototubes may be selectively controlled by the intensity of illumination irradiating said phototubes. The improved circuits disclosed eliminate the necessity for expensive and bulky filament transformers which require high voltage insulation between transformer windings connected to each of the cascaded rectifiers of a voltage multiplying circuit.

I claim as my invention:

5 '1; A voltage multiplying rectifier circuit comprising, in combination. a source of alternating potential, a plurality of cascaded radiation responsive voltage rectifiers, a plurality of capacitors each serially-connected between corresponding electrodes of successive ones of said cascaded rectiiiers, a plurality of resistors each seriallyconnected with two of said capacitors, means for deriving a multiplied rectified output voltage between one of said rectiers and said source, and means for predeterminately irradiating said rectifiers to control the conductivity thereof.

2. A voltagemultiplying rectier circuit comprising, in combination. a source of alternating potential, a plurality of cascaded radiation responsive voltage rectiers, a plurality of capacitors serially-connected between successive ones of said cascaded rectifiers, means for deriving a multiplied rectified output voltage between one of said rectiflers and said source, and means comprising a radiation source and separate radiation conduits from said radiation source to said rectiers for predeterminately irradiating said rectiers to control the conductivity thereof.

3. A voltage multiplying rectifier circuit comprising, in combination, means for connecting said circuit to a source of alternating potential, a plurality of radiation-responsive voltage rectiers, a plurality of capacitors, means serially connecting a iirst of said rectiflers and a first of said capacitors in shunt with said source, an impedance device. means serially connecting said impedance device and a second of said capacitors in shunt with said flrst rectifier, means serially connecting a second of said rectiiiers and a third of said capacitors in shunt with said impedance device. means for deriving a rectied output volt-y age between said second rectifier and said source, connecting means and radiation means for predeterminately irradiating said rectiilers to control the conductivity thereof.

4. A voltage multiplying rectifier circuit comprising. in combination, a source of alternating potential, a plurality of cascaded radiationresponsive voltage rectiers, a plurality of capacitors, means serially connecting a first of said rectiers and a ilrst of said capacitors in shunt with said source, a resistor, means serially connecting said resistor and a second of said capacitors in shunt with said ilrst rectier, means 5. A voltage multiplying rectifier circuit comprising, in combination, a source of alternating potential,

a plurality of cascaded rectifying photocells, a plurality of capacitors, means serially connecting a iirst of said photocells and a first of said capacitors in shunt with said source, a resistor, means serially connecting said resistor and a second of said capacitors in shunt with said iirst photocell, means serially connecting a second of said photocells and a third of said capacitors in shunt with said resistor, means for deriving a rectiiied output voltage between said second photocell and said source, and radiation means for predeterminately irradiating said photocells to control the conductivity thereof.

ALBERT W. FRIEND.

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

UNITED sTATEs PATENTS Number Number

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