US2458366A

US2458366A - Saw-tooth voltage generator

Info

Publication number: US2458366A
Application number: US20250A
Authority: US
Inventors: George W Fyler
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 1946-09-11
Filing date: 1948-04-10
Publication date: 1949-01-04
Anticipated expiration: 1966-01-04

Description

Patented Jan. 4, 1949 sew-room VOLTAGE cmmmrron George W. Fyler, Lombard, Ill., asslgnor to lvnllilizoiigla, Inc., Chicago,'lll., a corporation of Original application September 11, 1946, Serial No. 696,129. Divided and this application April 10, 1948, Serial No. 20,250

1': Claims. 1

This invention relates generally to television receivers and in particular to a power supply system for producing the voltages required for operation of a te'evision receiver including a cathode ray tube. This application is a division of my application Serial No.-696,129 filed Sept. 11, 1946.

In prior television receivers it has been necessary to use relatively large amounts of current at high voltage to provide energy for operation of the cathode ray receiver tube and for deflecting the electron beam thereof. Also in most television receivers a relatively large number of amplifying stages are required which also draw current at high voltage. For the above reasons a power supply network has been necessary which is capable of producing very high voltages, and to provide such a supply a relatively large power transformer has generally been provided. Such a power transformer is objectionable because of the high cost thereof and also because of the size and weight added to the receiver.

Heretofore television receivers of conventional design have required power inputs of 300 watts or more. The large amount of power required prevented the p'acing of a receiver in a small cabinet because of the difficulty of keeping the components reasonably cool. Also hum effects from the power supply are more pronounced when the power transformer is near the picture tube. This further prevented placing the television receiver in a small cabinet.

An object of this invention is to provide a small television receiver having simple and' efiicient means for providing the potentials required for operation of the television receiver tube.

Another object of this invention is to provide an inexpensive teevision receiver having a power supply system which does not require a power transformer to reduce the cost of the receiver and to eliminate hum in the picture normally produced by the transformer.

A feature of this invention is the provision of a television receiver having a power network which does not require a power transformer.

A further feature of this invention is the provision of a horizontal deflection generator which operates from relatively low voltage direct current and produces a sawtooth output having a relatively large amplitude.

Further objects, features and advantages will be apparent from a consideration of the following description taken in connection with the accompanying drawing in which a schematic diagram of a television receiver utilizing the horizontal deflection generator in accordance with vision receiver of the superheterodyne type capable of receiving modulated composite video signals and sound signals and deriving video, synchronization, and sound signals therefrom. A simplified power supply network is used in which selenium-rectifiers are used for energizing a system which operates at re'atively low voltages. A horizontal defiection generator is provided which operates from the low voltage power supply and produces a sawtooth voltage of relatively high magnitude for causing the horizontal deflections of the electron beam. This is accomplished by reversely charging condensers so that a sawtooth voltage is developed thereacross.

In the drawing, a schematicdiagram of a television receiver of the superheterodyne type is shown. The various components of the receiver which are not a part of this invention are shown by block diagrams and the function thereof indicated therein. These components will not be describ ed in detail but will be referred to in such a manner that the operation of the television receiver will be apparent. The receiver includes an antenna circuit 24 which may include a suitable antenna such as a dipole. The signals picked up by the antenna circuit are then amplified in the tuned radio frequency amplifier 28. A local oscillator 3| is provided for producing oscillations for converting the radio frequency signals into intermediate frequency signals in converter 34. Switching means for these units may be ganged together so that by a single operation, the antenna, radio frequency amplifier, and oscillator are tuned to the desired frequencies.

For the purpose of selectively amplifying the intermediate frequencies, an intermediate frequency amplifier 36 is provided. The video and sound intermediate frequency signals are both passed through the intermediate frequency amplifier 36 and are separated after passing through the video amplifier as is explained in my copending application Serial No. 676,651 filed June 14, 1946, subject Television receiver circuit. The amplified intermediate frequency signals are applied to detector 40 wherein the video and sound frequency signals are derived. These signals are then amplified in video amplifier 42. The amplified video and sound signals are separated in the video and sound separation circuit 44 with the video signal being applied to the cathode ray tube l5 and theclipper I1, and the sound signal being applied to the limiter 50. The sound signal is 3 1611 applied to the discriminator 5I and audio nplifier 53 and is reproduced in loud speaker I4. The composite video signal is applied to the ithode 6| of the cathode ray tube I6. The con- 'ol grid 62 of the tube may be connected to the egative side of the power supply and the cath- :le may be biased with respect thereto through ariable resistor '64, the resistor being variable control the intensity of the cathode ray beam nd thereby the brightness of the image prouced. Electrostatic deflection is utilized in the ibe, the vertical deflection being controlled by Iates 68 and 69 and horizontal deflection by 1e plates I0 and II. Potentials for causing vercal deflection are applied to the plates by vercal deflection generator I2 and potentials for orizontal deflection are produced by horizontal efiection generator I3. The clipper functions to erive the synchronization pulses from the comosite video signal, the derived pulses being aplied to the generators I2 and 13 to control the Lwtooth voltage waves produced thereby.

The television receiver in accordance withthe ivention is adapted to be energized from the andard 110 volt alternating current household :vwer supply. In order to provide the power reuired for operation of the television receiver iergy must be available for supplying the heaters )r the cathodes of the various tubes and also igh potential direct current of various voltages lust be available for providing the plate and :reen voltages necessary for the tubes and for roviding the potentials required for focusing and efiecting the beam of the cathode ray tube. The JWel supply system in accordance with the in antion includes terminals I00 and MI adapted I be connected to a source of 110 volts alternatlg current, a power switch I02 being included )r controlling the energization of the system. he connection from terminal IOI continues irough switch I02 to a pair of selenium rectifiers l2 and I33. The selenium rectiflers are conacted so that the positive portion of the alternat- Ig current cycle is rectified by rectifier I32 and spears across condenser I34 which is connected e'tween the rectifier I32 and the terminal I00 hich forms the other side of the alternating cur- :nt source. The rectifier I33 is connected to pass 11y negative currents so that a negative potential ppears across condenser I35 connected between- :ctifier I33 and the common terminal. It is aparent that there will be relatively large 60 cycle pple in the voltages across each of the condensers i4 and I35. However, the ripple in the voltages ill be out of phase so that the combined pontial across the two condensers will have a 120 ole ripple which will be of much smaller mag- .tude than the 60 cycle ripple across each conanser. It is obvious that by completely elim- .ating the center wire the 60 cycle ripple would 2 thereby eliminated. However, substantially 1e same effect can be obtained by retaining the enter wire and placing a relatively large restor I36 therein to reduce the effect of the 60 'cle ripple. Resistors I31 and I38 are provided the positive and negative wires and condensers I9 and I40 are provided across the positive and agative branches, respectively, of the power supy to provide stable operating potentials. A1- lough the power supply system is illustrated as Innected only to the horizontal deflection genator 33, it is apparent that it can also be used energize the other components of the television :ceiver.

Referring now more specifically to the horizontal deflection generator I3. the generator includes a triode tube 62 which functions as a blocking oscillator. The tube includes a cathode I50, grid I5I and plate I52. The plate and grid are connected to the windings I53 and I54 of a transformer in a manner to provide regeneration therebetween. A damping resistor I6'I is shown connected across winding I53 and a similar damping resistor may be provided across winding I54. The grid is also connected to coupling condenser 8| to receive synchronization pulses therefrom. The negative side of the power supply network is connected through choke coil I55 to the cathode I and the plate is connected to the positive wire through choke coil I56 and variable resistor I43. The coils I and I56 are mounted on a common core and are so wound and connected that the inductance between points I63 and I64 is a maximum. It is seen that the total power supply voltage can be applied to the horizontal deflection generator, or the voltage can be reduced by resistor I49 to reduce thereby the amplitude of the generator output. The frequency of the oscillator can be controlled by changing the bias on grid I5I as by adjusting resistor I51. Condenser I59 acts as a by-pass for resistor I51. A series circuit is provided between the terminals of the power supply through the choke coils I55 and I56 and condensers I60, I6I and I62. The coils are preferably identical and as they are wound so that the inductances thereof are additive, the total inductance is four times that of either coil. In order that the system is balanced the total capacitance of the condensers I60 and I'6I in' series is made substantially equal to the capacitance of condenser I62 and the common connection therebetween is connected to the center wire of the power supply. The two condensers I60 and IN are provided so that a sawtooth voltage of smaller amplitude can be derived from terminal I68 if desired, as for exciting a high voltage power supply.

In operation, the blocking oscillator circuit, including windings I53 and I54 the condensers I60, I6I and I62 and the stray circuit capacities, is adjusted to a high frequency substantially five times that of the horizontal synchronization pulses. More specifically, when the tube 82 conducts, a series circuit is formed through winding I53 and condensers I60, I6I and I62 which is resonant at a frequency substantially five times that of the horizontal synchronization pulses. The choke coils I55 and I56 and condensers I60, I6I and I 62 are so chosen that the series circuit through these components will be resonant at a relatively low frequency, a frequency one-tenth that of the horizontal scanning frequency being suitable. As the coil I 56 is connected to the positive wire of the power supply and the coil I55 is connected to the negative wire, the current through this circuit will cause the condensers I60, I6I and I62 to charge so that the point I63 becomes positive and the point I64 becomes negative. It is noted that this will cause a positive potential on the plate I52 which tends to cause the tube to conduct. When the tube 82 conducts a heavy plate current will flow through the high frequency series resonant circuit producing current through the condensers I60, I 6I and I62 in an opposite direction to that produced by the power supply. The transfer of energy through the windings I 53 and I54 will render the tube 82 highly conductive. The blocking oscillator circuit is arranged so that the tube 82 will conduct for one-half cycle which will cause the point I63 power supply source.

aesaaec to become negative and the point I to become positive. Said tube therefore operates as a circuit charging means. As the natural frequency of the the retrace period will be fast as is desired. If

the frequency of the oscillator is five times the frequency of the horizontal pulses as stated; since the retrace is only one-half a cycle the time required for the retrace would be one-tenth of the total time of one horizontal deflection cycle. The reversing potentials on points I63 and IE5 are applied through condensers I65 and I68 to the horizontal deflecting plates l and H, respectively. The voltage appearing on each plate will swing from positive to negative values and vice versa to thereby provide a relatively large balanced sawtooth voltage across the deflecting plates 70 and ii.

In a specific model constructed in accordance with the invention, with standard 110 volt alternating current power applied to the terminals I00 and ill! of the power supply, voltages of approximately 130 volts were produced between the positive and negative wires and the center wire of the power supply, thus making the total voltage between the negative and positive wires approximately 260 volts. When using one section of a 12SN7 tube as the blocking oscillator in the horizontal deflection generator 13, and applying the entire 260 volts thereto, voltages varying plus i and minus approximately 300 volts were obtained across the sides of the horizontal deflection generator circuit thereby providing a sweep voltage having an amplitude of 600 volts for deflection of the cathode ray beam in a horizontal direction. This voltage was ample for operating a seven inch direct viewing cathode ray tube such as type 7GP4.

As previously stated, horizontal synchronization pulses are applied to the generator from the clipper ll through coupling condenser 8! to the grid il of tube 82. This signal is applied across the winding l5d of the blocking oscillator transformer which acts as a filter to further select the horizontal synchronization pulses. By properly tuning the coil I55 a series resonant circuit having a very sharp characteristic can be provided.

It is seen from the above that I have provided a simple horizontal deflection generator which is effective to provide balanced sawtooth voltages of relatively high amplitude from a low voltage Only a single triode tube section is required in the generator so that the cost thereof is very small. The trace portion of the voltage wave is linear and the retrace portion is relatively fast so that the resulting wave is highly satisfactory for providing deflection voltages.

Although I have illustrated one specific embodiment of my invention, it is apparent that various changes and modifications can be made therein which fall within the intended scope of the invention as defined in the appended claims.

I claim:

1. In a television receiver including a, cathode ray tube having horizontal and vertical deflection electrodes for deflecting the electron beam of said tube and means for deriving synchronization pulses for controlling the deflection of said beam. a generator for providing sawtooth voltages for said horizontal deflection electrodes comprising an electron discharge valve having input and output electrodes, a transformer having a-pair of windings, a plurality of condensers, a pair of equal inductances, a source of potential, said inductances and condensers being connected in series across said source of potential, said input and output electrodes of said valve being coupled through said windings of said transformer, said output electrodes of said valve being connected across said condensers so that the voltage built up on said condensers because of current flowing from said source of potential is applied thereto, said valve being arranged to conduct when a predetermined potential is applied to said output electrodes to provide current throughsald condenser in a direction opposite to the current flow caused by said source of potential to thereby charge said condensers in the opposite direction,

and means for applying said synchronization pulses to the input terminals of said valve to cause said valve to conduct at a. predetermined time.

2. A voltage generator adapted to produce a sawtooth voltage wave comprising condenser means, a pair of equal closely coupled inductances, a source of potential, and a blocking oscillator including an electron discharge valve, said inductances and said condenser means being connected in series across said source of potential and being of such value that a series circuit resonant at a relatively low frequency is provided for charging said condenser means in one direction, said electron discharge valve being connected across said condenser means and being,

biased to conduct when a predetermined potential is applied thereto, said blocking oscillator having a, relatively high frequency and being arranged so that said valve is blocked after an oscillation of one-half cycle duration so that said condenser means is discharged and then charged in the opposite direction.

3. A voltage generator adapted to produce a sawtooth voltage wave comprising condenser means, a. pair of equal closely coupled inductances, a source of potential, and a blocking oscillator including an electron discharge valve, said inductances and said condenser means being connected in series across said source of potential for charging said condenser means in one direction, said inductors providing a steady charging current whereby said condenser means charge to a, voltage greater than the voltage of said source, said electron discharge valve being connected across said condenser means and being biased to conduct when a predetermined potential is applied thereto, said blocking oscillator having a relatively high frequency and being arranged so that said .valve is blocked after an oscillation of onehalf cycle duration so that said condenser means is discharged and then charged to substantially the same voltage in the opposite direction. I V

4. A voltage generator adapted to produce a sawtooth voltage wave comprising condenser means, a pair of equal closely coupled inductances, a source of potential, and a, blocking oscillator including an electron discharge valve, said inductances and said condenser means being connected in series across said source of potential for charging said condenser means in one direction, said inductors providing a steady charging current sreby said condenser means charge to a voltage ater than the voltage of said source, said :king oscillator being connected across said denser means for applying the voltage on said .denser means to said valve, said blocking [llator and said condenser means forming a Les circuit resonant at a relatively high fre- :ncy when said valve conducts, said valve being :ked after an oscillation of one-half cycle dura- 1 so that said condenser means is discharged l then charged to substantially the same voltin the opposite direction, so that the sawtooth age wave developed across said condenser ins has an amplitude variation greater than :e the voltage of said source. A voltage generator adapted to produce a tooth voltage wave of a predetermined frency comprising, a plurality of condensers, a r of equal closely coupled inductances, a source Jotential, and a blocking oscillator including electron discharge valve, said inductances and densers being connected in series across said roe of potential and being of such value that series circuit is resonant at a frequency of order of one-tenth that of said predetermined uency, said electron discharge valve being nected across said condensers so that the voltbuilt up on said condensers because of curt flowing from said source of potential is lied thereto, said valve being biased to cont when a predetermined potential is applied reto to cause current to flow through said consers in a direction opposite to the current flow sed by said source of potential, said blocking llator having a frequency of the order of live as that of said predetermined frequency and lg arranged so that said valve c onducts duran oscillation of one-half cycle so that said :lensers are rapidly discharged and then rged in the opposite direction.

A sawtooth voltage generator comprising ienser means, a pair of equal closely coupled ictances a source of potential, and a blocking llator including an election discharge valve ing input and output electrodes and a trans- 181 having windings coupling said electrodes, condenser means being connected interliate said inductances in series across said cc of potential, said output electrodes of said 'e being connected in series with one of said isformer windings across said condenser us so that the voltage built up thereacross is lied to said valve, said valve being biased to iuct when a predetermined potential is applied etc to provide a high frequency series resot circuit through said condenser means and one winding permitting the flow of current ugh said condenser means in a direction oppoto current fiow caused by said source of potensaid transformerproviding energy to said it electrodes to render said valve highly con- ;ing, said valve being blocked when an osciln of one-half cycle has taken place so that condenser means is discharged and then 'ged in the opposite direction.

A sawtooth voltage generator comprising a ality of condensers, a pair of equal inductas, a source of potential, and a blocking oscil- 7 including an electron discharge valve having .t and output electrodes and a transformer ng a pair of windings coupling said electrodes, inductances-and said condensers being coned in series across said source of potential, output electrodes of said valve being coned across said condensers so that the voltage built up thereacross because of current flowin from said power supply is applied to said valve, said valve being biased to conduct when a predetermined potential is applied thereto to provide current through said condensers in a direction opposite to current flow caused by said source of potential, said blocking oscillator being arranged so that transfer of energy through said transformer from said output electrodes to said input electrodes blocks said valve when an oscillation of one-half cycle has taken place to discharge said condensers and then charge said condensers in the opposite direction.

8. A .voltage generator adapted to produce a sawtooth voltage wave comprising, condenser means, a pair of equal closely coupled inductances, a source of potential, and a blocking oscillator including an electron discharge valve, said inductances and said condenser means being connected in series across said source of potential and being of such value that a series circuit resonant at a relatively low frequency is provided so that voltage is built up on said condenser means at a uniform rate to provide a substantially linear trace, said electron discharge valve being connected across said condenser means so that the voltage thereon is applied to said valve to render said valve to conduct when said voltage reaches a, predetermined value, said blocking oscillator being tuned to resonate with said condenser means at a relatively high frequency to form a high frequency resonant circuit through which said condenser means discharges when said valve conducts, said valve being blocked after an oscillation of one-half cycle duration so that said condenser means is rapidly discharged and then charged in the opposite direction to provide a fast retrace.

9. A voltage generator adapted to produce a sawtooth voltage wave of a predetermined frequency comprising, condenser means, a pair of equal closely coupled inductances, a source of potential, and a blocking oscillator including an electron discharge valve, said inductances and said condenser means being connected in series across said source of potential and being of such value that the series circuit is resonant at a frequency of the order of one-tenth that of said predetermined frequency, so that voltage is built up on said condenser means at a. uniform rate to provide a substantially linear trace, said blocking oscillator being connnected across said condenser means so that the voltage on said condenser means is applied to said electron discharge valve to cause said valve to conduct when said voltage reaches a predetermined value, said blocking oscillator being tuned to resonate with said condenser means at a frequency of the order of five times that of said predetermined frequency when said valve conducts, said valve being arranged to conduct for an oscillation of onehalf cycle so that said condenser means is rapidly discharged and then charged in the opposite direction to provide a fast retrace.

10. A sawtooth voltage generator adapted to produce sawtooth voltage waves comprising, a pair of equal condenser means, a pair of equal closely coupled inductances, a source of potential, and a blocking oscillator including an electron discharge valve, said condenser means being con nected intermeidate said inductances in series across said source of potential and being of such value that a series circuit resonant at a relatively low frequency is provided so that voltage is built up on said condenser means at a uniform rate to provide a substantially linear trace, said blocking oscillator being connected across said condenser means so that the voltage on said .condenser means is applied to said valve to cause said valve to conduct when said voltage reaches a predetermined value, said blocking oscillator being tuned to resonate with said condenser means at a relatively high frequency and arranged so that -said valve conducts for one-half cycle so that said condenser means is rapidly discharged and then charged in the opposite direction to provide a fast retrace, whereby balanced sawtooth voltage waves are developed across said pair of condenser means.

11. In a television receiver including a cathode ray tube having horizontal and vertical deflection electrodes for deflecting the electron beam of said tube and means for deriving synchronization pulses for controlling the deflection of said beam, a generator for providing sawtooth voltages for said horizontal deflection electrodes comprising a pair of condenser means, a pair of equal inductances, a source of potential, a blocking oscillator including an electron discharge valve and a transformer including a pair of windings, said inductances and condenser means being connected in series across said source of potential, said valve being connected across said condenser means so that the voltage built up thereon because of current flowing from said source of potential is applied to said valve, said valve being arranged to conduct when a predetermined potential is applied to said output electrodes to provide curent through said condenser means in a direction opposite to the current flow caused by said source of potential, said blocking oscillator being so arranged that said valve conducts during one-half cycle of said oscillator so that said condenser means are discharged and then charged in the opposite direction, and means for applying said synchronization pulses to said valve across one of said windings to cause said valve to conduct at a predetermined time.

12. In a television receiver including a cathode ray tube having horizontal and vertical deflection electrodes for deflecting the electron beam of said tube and means for deriving synchronization pulses for controlling the deflection of said beam, 2. generator for providing sawtooth voltages for said horizontal deflection electrodes comprising a plurality of condensers, a pair of equal inductances, a source of potential, a blocking oscillator including an electron discharge valve having input and output electrodes and a transformer having a pair of windings coupling said electrodes, said inductances and condensers being connected in series across said source of potential, said output electrodes of said valve being connected across said condensers so that the voltage built up thereacross because of current flowing from said source of potential is applied to said valve, and means for applying said synchronization pulses across one of said windings to said input electrodes to cause said valve to conduct to provide current through said condenser in a direction opposite to the current flow caused by said source of potential, said one winding being tuned to act as a filter for said synchronization pulses, said blocking oscillator being so arranged that transfer of energy through said transformer blocks said valve when an oscillation of one-half cycle has taken place.

13. The method of producing a sawtooth voltage wave across condenser means which is connected to a blocking oscillator including an electron discharge valve and a transformer having primary and secondary windings, said method comprising the steps of, charging said condenser means to one polarity at a uniform rate. discharging said condenser means and storing energy therefrom in said primary winding, transferring energy from said primary winding to said secondary winding to render said valve more conductive, charging said condenser to the polarity opposite to said one polarity by the energy stored in said primary winding, and utilizing said valve to prevent transfer of current between said primary winding and said condenser means for a succeeding linear charging step.

14. A sawtooth voltage generator circuit for producing a sawtooth voltage wave of one frequency comprising, condenser means, means for charging said condenser means at a uniform rate, an electron discharge valve having input and output electrodes, a transformer having primary and secondary windings, said output electrodes of said valve and said primary winding being connected across said condenser means and forming a series circuit thereby in which oscillations can take place when said valve conducts, said series circuit being resonant at a frequency at least five times said one frequency,

said secondary winding being connected to said input electrodes of said valve to transfer energy thereto for rendering said valve more conductive.

15. A sawtooth voltage generator circuit comprising, condenser means, means for charging said condenser means at a uniform rate, an electron discharge valve having input and output electrodes, a transformer having primary and secondary windings, said output electrodes of said valve and said primary winding being connected across said condenser means and forming a series resonant circuit thereby in which oscillations can take place when said valve conducts, said secondary windings being connected to said input electrodes of said valve to transfer energy thereto for rendering said valve more conductive.

16. A sawtooth voltage generator circuit for producing a sawtooth voltage wave of one frequency comprising, condenser means, means for charging said condenser means at a uniform rate, an electron discharge valve having input and output electrodes, a transformer having primary and secondary windings, a damping resistor connected across said primary winding, said output I electrodes of said valve and said primary winding being connected across said condenser means and forming a series circuit thereby in which oscillations can take place when said valve conducts, said series circuit being resonant at a frequency at least flve times said one frequency, said secondary winding being connected to said input electrodes of said valve to transfer energy thereto for rendering said valve highly conductive.

17. A sawtooth voltage generator circuit for producing a sawtooth voltage wave of one frequency comprising, condenser means, means for charging said condenser means at a uniform rate,

and a blocking oscillator including an electron discharge valve and a transformer having a pair of windings, said valve being connected in series with one of said windings to said condenser means and forming a series circuit in which oscillations can take place when said valve conducts, said series circuit being resonant at a frequency at least five times said one frequency, said one winding providing energy to said blocking oscillator to render said valve more conduc- 11 tive, said valve operating to disconnect said inductance means from said condenser means when said resonant circuit has completed one-half cycle of an oscillation.

GEORGE W. FYLER;

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

UNITED STATES PATENTS Number 12 Name Date Caweln Jan. 18, 1938 Barthelemy Aug. 8, 1939 Norton Nov. 21, 1939 Faudell Jan. 30 1940 Norton July 16, 1940 Eaglesfleld et a]. June 3, 1941 Baldwin, Jr Oct. 14, 1941 Wheeler Dec. 2, 1941 Campbell Oct. 6, 1942 Milward Aug. 21, 1945 Edson et a1 Dec. 10, 1946