US2478744A - Power recovery system - Google Patents

Description

Aug. 9, 1949. E. l.. CLARK POWER RECOVERY SYSTEM Filed Dec. 26, 194e Patented Aug. 9, 1949 have Radio Corporation of A Delaware marica, a corporation of application December ze, 11946, serial No. 718,499

(ci. sis-2i l l Claims.

The present invention relates to power recovery systems, and in a preferred form relates to means whereby normally unused power may be recovered from the horizontal, or line, cathode ray beam deflection circuit of a television receiver or other unit utilizing a cathode ray device to scan a target area or to reproduce an image of any sort on such an area.

It is known in the art to connect a so-called damper tube across the cathode ray beam deflection coils, or across one winding of the transformer which may couple these coils to the power output tube in the horizontal deflection circuit of a television receiver. One purpose of this damper tube is to aid in suppressing the highfrequency oscillations which would otherwise occur, due to the inductive nature of the deflection circuit, following the retrace, or snap-back, of the cathode ray scanning beam at the end of each line-scanning operation. Such a system is exemplified by Blumlein United States Reissue Patent No. 21,400, dated March 19, 1940.

It is also known to employ a grid-controlled damper tube for the above purpose, and to control the conduction of this tube by applying to its grid a voltage variation having a particular" waveform, so that the flow of current through the damper tube will combine with the current output of the power tube to result in a substantially linear summation current through the cathode ray beam deflection coils. A system of the latter type is disclosed, for example, in Tolson United States Patent No. 2,280,733, granted April 21, 1942.

Damper tubes, such as set forth above, are

frequently employed in combination with an ance, or other non-useful load. However, in a copending United States patent application of Otto H. Schade, Serial No. 593,161, filed May 11, 1945, there is disclosed a method and means for reclaiming a portion of the energy which is thus developed in the damper tube circuit, and for applying this reclaimed energy so as to either (l) increase the amount of power available for application to the load circuit, or (2) maintain the same power output to the load circuit while reducing the amount of input, or source, energy required. In other words, the reclaimed D.C. power may be used to reduce the required supply voltage while maintaining the same deflection 2. original supply voltage to result in greater scanning power.

A preferred type of circuit set forth in the above-mentioned Schade application makes use of a triode damper, or suppressor, tube in combination with a condenser. The D.C. voltage developed on the condenser during operation of the circuit is fed back with proper polarity to the plate of the power output tube in series with the tube supply voltage, so that the latter, is in effect, increased or boosted One necessary condition for such'operation is that the average plate currents of the power tube and of the damper tube be substantially equal. This may be accomplished by a proper selection of deflection coil impedance and/or transformer stepdown ratio.

The amount of power which may be reclaimed in the above manner is an inverse function of the internal resistance of the damper tube. Since .the internal resistance' of a triode is relatively great,'the degree of power recovery is limited. It has, therefore, been found that an increase in the amount ofpower which is available for recirculation may bebrought about by utilizing a damper tube having a lower internal resistance, such, for example, as a diode. A system of this nature is disclosed in a copending United States patent application of Charles E. Torsch, Serial No. 610,368, filed August 11, 1945.

When a diode damper' `tube is employed, however, itis difficult to obtain linearity of deflection, as ordinarily the flow of damper tube current is not subject to control due to the fact that the tube resistance is a fixed quantity. In a United States Patent of Simeon I. Tourshou, No. 2,440,418, granted April 27, 1948, this difculty is partially overcome by applying to one of the electrodes of the diode damper tube a Voltage having a predetermined phase displacement with respect to the voltage appearing across the primary winding of the coupling transformer. In this manner, a cathode ray tube deection which is sufiiciently linear for most purposes is conveniently obtained, especially in the case of relatively inexpensive television apparatus. The degree of linearity in such a system, however, does not approach that of the grid-controlled suppressor tube circuitin which the waveform of the voltage variation applied to the grid of the damper tube may be 'chosen so as to compensate for circuit conditions which would otherwise tend to produce -a relatively high degree of distortion.

According to one feature of the present inamplitude, 01 it may be added to boost the 55 Yention, therefore, a cathode ray beam deflection circuit is provided utilizing a pair of damper, or suppressor, tubes. One of these tubes is utilized for the purpose of obtaining linearity of deflection of the cathode ray scanning beam, and hence is preferably a triode, or other grid-controlled tube, to the control electrode of which a voltage variation is applied having a lwaveform which,is chosen to producelinearity of scan under the prevailing circuit conditions. The other damper tube is preferably of the diode type, and is connected in series with a condenser, or other energy-stor-V age element. Since the internal resistance of the diode is relatively low, amaximum Voltage is developed on its associated condenser, and this condenser voltage is preferably fed back to the power tube with proper polarity and in series with the supply Voltage source so as to result in increased scanning output. Furthermore, since two damper tubes are utilized, the suppression of high-frequency oscillations following retrace is more complete, resulting in less image distortion. One object of the present invention, therefore, is to provide an improved system for recovering a portion of the reclaimable energy normally lost in cyclic reactiveload circuits.

A further object ofthe invention is to provide a power recovery system particularly adapted for the horizontal deflection circuit of a television receiver, and possessing the advantages enumerated in part above.,

Other obj ects and advantages will be apparent from the following description of a preferred form Y of the invention and from the drawing, the single figure of which is a sellematic representation vof a preferred form of the present invention.

Referring now to the drawing, there is shown a television deflection and highvoltage rectifier circuit which includes a horizontal or line frequency power output tube I0. Power tube Ill is adapted to supply, when voltage variations which may have a, waveform such as indicated by the reference numeral I2 are applied to the controlelectrode thereof, cyclically varying vcurrent to a pair of horizontaLorl line, cathode ray beam deflectioncoilsll through a coupling transformer I6.

Transformer I6 ris provided 4 witna .primary winding I8, astep-up wlnding 2ll forming, in effect, an extensionof theprimary winding I8, and a secondary winding 22. This secondary winding 22 is connected across the horizontal cathode ray beam deflection coils I4 in series with all or a portion of a centeringresistor 23the function of which willbe later described. The horizontal cathode ray beam deflection coils 'I4, together with a pair of vertical, or field, deection coils 24, preferably formpart of a yokeassembly encircling the neck of a cathode ray image-reproducing tube, or kines cope 26..y The vertical cathode ray beam deection coils 24 .are energized by sawtooth current of field-scanning frequency from a deflection generatorI 28, which may be of any suitablev design. It will not, therefore, be set forth in detail.

During operation of theillustrated circuit, as will be subsequently brought out, voltage. surges are produced across the primary `winding I8 `of transformer I6. These voltage surges are stepped up by the winding 20 and applied to a surge-type rectifier 3D which may, for example, be of rthe type disclosed in United States patent of Otto H. Schade, No. 2,439,223, granted April 6, '1948, or in a United States patent of Albert W.' Friend, No. 2,452,013, issuedpn October 19;.194'8. The output of rectifier 30, which is a substantially smooth D.C. potential and which is diagrammatically represented in view of the disclosure in the mentioned Schade application, for instance, is applied to the second anode 32 of the kinescope, or cathode ray imagereproducing tube, 26 over the conductor 34.

The voltage variations I2 appliedto the control electrode of power tube III, together with its bias potential, produce a rising current in tube i6 during scansion. This current is cut 01T at the beginning of retrace time. The current in the deflection coils I4 and transformer I6 does not disappear at the instant of out off of tube i6, however, due to the inherent distributed capacity of the circuit. This distributed capacity, at the instant of the beginning of retrace, is charged to a relatively low voltage.

The inductance of the deection coils I4 and transformer I 6, together with the above-mentioned distributed capacity, forms atuned circuit in which high-frequency oscillations would normally be produced,'these oscillations beginning with the start of retrace time. After onehalf cycle of the natural period of oscillation of the circuit, the current in the deiiection coils i4 is reversed, and the oscillation isstopped at the negative current peak. The means for producing such a result include a triode, or other grid-controlled damper tube 36, connected across the secondary winding 22 of transformer l5, and also the series combinationof a diodel damper tube 46 and acondenser 42 connected across the secondary winding 22 of transformer I6 through all or a portion of the centering resistor 23.

During retrace-that is, during the half-cycle of the natural period 4of oscillation of the circuit, the current in each of tubes III, 36 and 49 is completely blocked, the voltage across the deflection coils i4 and transformer I6 reaching a high value at one-quarter vcycle when the current passes through zero. In order that linear defiectionof the cathode ray beam be produced, it is necessary that the rate of change of the current in the de,- flection coils I4 be maintained constant during the scanning portion of the deflection cycle, and as long as this rate of changeY of current is constant, the voltage across the deflection coils I4 will remain steady at a predetermined level.

The polarity of the voltage applied to the anode of each of the damper tubes 36 and 40 immediately following retrace is such as to cause these damper tubes 36 and 40 to conduct.v When the combined currents of the damper tubes 36 and 46 are properly matched with the power tube current, the summation of these currents will have a linear characteristic which represents the cur.- rent actually flowing through the deflection coils I4 during scansion.

In accordance with the present invention. the overall, or combined, value of thev currents flowing through the dampertubes Y36 and 4e is adjusted for linearity of deflection coil current by adjusting the waveform of thev voltage variation applied tothe control electrodev 44 of the triode damper tube 36. This voltage variation must be such that the damper tube 36 begins to conduct immediately following the retrace time,and operates to produce a decreasing plate current. Accordingly, the voltage variation may have a waveform such as indicated inthe drawing by the reference numeral 46.

The voltage variation 46 applied to the control electrode 44 of the damper tube 36, and the nor.- mal bias on the electrode 44 must, therefore, be so adjusted as to give the desired waveform to the anode current permitted to iiow through the damper tube 36. The most positive part of the waveform 46 accordingly occurs immediately following the retrace time, with negative peaking impulses occurring concurrently with the retrace time.

After the initiation of current flow in the damper tube 36, the waveform 46 of the potential on the control electrode 44 is is changed exponentially in a negative direction. This reduces, at a predetermined rate, the current ow through the damper tube 36, thereby resulting in a combined current flow through the power tube ID, damper tube 36 and damper tube 4i! that is linear, and that will produce linear deflection of the cathode ray beam of the image-reproducing tube or kinescope 26.

The means for obtaining a voltage variation having a waveform such as represented by the curve 46 includes a diiferentiating network cornprising a condenser 48 and resistors 5t and 52, the upper plate of condenser 48 being connected through the relatively small resistor 54 to the upper end of the secondary winding 22 of transformer I6 and also to the high-impedance end of the horizontal deflection coils i4. Bias for the control electrode 44 of damper tube 36 is obtained from the grid current iiow through a resistor 56 in parallel with a by-pass condenser 53, one end of resistor 56 being connected to the cathode of damper tube 36. The resistor 52 is made adjustable and acts as a linearity control by changing the diierentiating constant of the elements 48, 50 and 52. The voltage output of the differentiating networky as developed on resistors 50 and 52, is applied to the control electrode44 of tube 36 through a shaping resistor 60.

The voltage appearing on the control electrode 44, as represented by the waveform 46, has two exponential sections. When the control electrode 44 is positive, current ows through the resistor 60 and the grid-cathode impedance of tube 36. This impedance shunts the diierentiating resistor 53 so as to change the diilerentiating constant of the network 48, 58 and 52. The result is a fast-decaying transient during the initial portion of the scanning period, and this transient products a heavy initial plate current output from the damper tube 36 which is effective in damping out the rst strong parasitic oscillations in the circuit.

The second section of Waveform 46 is a slowdecaying transient caused by the resistor 5i! when the control electrode 44 is negative and no currentl flows through resistor 65. Resistor 60, therefore, acts in eifect as a current limiter to vary the impedance of the control electrode 44 of tube 36.

The series combination of diode damper tube 40 and condenser 42, as above brought out, is connected, in parallel with the triode damper tube 36, across both the secondary winding 22 of transformer I6 and also across the horizontal deection coils I4. As such, the conduction of the diode damper tube 46 occurs substantially simultaneously with the conduction of the triode damper tube 36. This results in a substantially smooth D.C. potential being developed on condenser 42, However, the magnitude of this voltage on condenser 42 is dependent upon the internal resistance of tube 49, since the greater the voltage drop across the tube, the less will be the voltage developed on the condenser. The internal resistance of the diode 4I), however, is normally considerably less than the internal resistance of the triode 36, or of any other grid-controlled damper tube, Accordingly, the D.C. potential developed on the condenser 42 will be greater than if the diode 4t were replaced with a tube having one or more additional electrodes.

The anode of power tube III is supplied with operating potential from a source indicated in the drawing as +B. The condenser 42, on which a relatively smooth potential is developed in the manner above described, is connected between this source of operating potential +B and the anode of power tube I6 in series with the primary winding It of transformer I6. Furthermore, the

Vpolarity of the voltage developed on condenser 42 is such as to additively combine with the supply source voltage to result in increased anode voltage for the power tube I6, and hence increased scanning power. It will be appreciated, however, that, if desired, the amplitude of the current flowing through. the horizontal deiiection coils I4 may be maintained constant, and the value of the supply voltage source +B reduced by an amount equal to the voltage developed on condenser 42.

The remaining elements of the television system of which the deection and high-voltage circuit above described forms a part may be supplied with energy from the +B source illustrated in the drawing through the centering resistor 23. This resistor, which is adjustable as shown, permits a selected steady current of relatively low value to ow through the deflection coils I4, and hence provides for horizontal centering of the cathode ray beam of the kinescope 26. The portion of the centering resistor 23 included in the secondary circuit of transformer I6 is bypassed by a capacitor 62 which provides a low-impedance path for the beam deection current, thus effectively removing resistor 23 for the A.C. deflection components. A centering arrangement of this general nature is illustrated and described in the above-mentioned Tourshou application.

An adjustable reactance element such as an lnductor 64 may, if desired, be connected across all or a portion of the secondary winding 22 of transformer I6 so as to provide a size, or width, control of the image raster produced on the face of the image reproducing tube 26. Such an arrangement is set forth in a United States patent of Antony Wright, No. 2,449,969, issued September 28, 1948.

It will thus be seen that, by means of the disclosure herein set forth, a maximum amount kof power may be reclaimed from the energy normally lost in the horizontal deflection circuit of a television system without a sacrifice of scanning linearity. In other words, the present disclosure incorporates in a preferred embodiment the linearity-producing advantages of a triode damper tube with the increased boost voltage available in damping circuit utilizing a diode.

I claim:

1. In a cathode ray beam deilection circuit, the combination of a grid-controlled power output tube and a source of operating voltage therefor, means for applying a voltage variation to the grid of said power output tube so as to produce a cyclically varying current output therefrom, a transformer, a pair of cathode ray beam deflection coils connected to receive the cyclically Varying current output of said power tube through said transformer, a first grid-controlled damper tube connected across one winding of said transformer, means for applying a voltage variation to the grid of said first damper tube to control the conduction thereof, an energy-storage device, a seconu; twoelectrodadamper;tube.- connected in se, ries with. said. energy-storage device, the series combination o said energy-storagedevice ,and said second damper tube being connected across one winding .of said. transformerl in parallel 'with said iirstdamper tube, and means connecting said energy-storage device to said power output tube additively inseries with said source of power output tube operating voltage.

2. Ina power recovery system ofthe type in which at least one power output tube is connected to. deliver, cyclically. varying currentto an inductive loadV member, the combination of damping means vfor reducing undesired oscillations in said system during a portion of each current cycle due: in` part to the inductive naturek of said load member, said means including a triocle damper tube, a diode damper tube, and a condenser, said diode damper tube and said condenser being connected in series, with the resulting series combination being connected in parallel relation with said triode damper tube so that a substantially constant l3.-C. voltage developed on said con denser during operation of said system, and means for applying the said substantially constant D.-C. voltage thus developed on said conm denserrto increase the normal current output of said power output tube.

3. a power-recovery system according to claim 2, further comprising means for selectively con.- trolling the conduction of said rtriode damper tube.

.A Ypower recovery system according to claim further comprising means for differentiating the voltage developed across said inductive load member during operation oi said system, and means for applying said differentiated voltage to control the conduction of said triode damper tube.

5. A power recovery system according to claim in which the said inductive load member comprises a pair of cathode ray beam deflection coils.

6. In a cathode ray beam deflection circuit of the type in which at least one power output tube connected to deliver cyclically varying current to a pair of cathode ray beam denectioncoils tlf-.rough an inductive coupling member, the combination of a grid-controlled electron discharge device in parallel with at least a portion of said inductive coupling member, an energy-storage element, a two-electrode electron discharge device connected in series with said energy-storage element, means for connecting the series combination of said energy-storage element and said twoelectrode electron discharge device effectively in parallel with said grid-controlled electron discharge device, and means for applying the energy 8 stored in. said, energy,-,StorageA element. during op',-l erationV of saidcircuit to increase the current output ofisaid power ,output tube.

7. A -cathodefray beamdeecton circuit according toclaim 6, in whichy said` energy-storage element is a condenser of high capacity having low surge, impedance` relative to the internal resistance of said two-electrode device.

8. A cathode ray beam deflection circuit ac-Y cording to claimt in which said inductive coupling member isa transformer, said grid-con-` trolled electron-,discharge device being connected across at leastl a portion of one windingof said transformer.

9. in la cathode ray beam deection circuit of thetypeinwhich at least one power output tube, is connected to deliver cyclically Varying current to va pair of .cathodev ray beam deflection coils through an inductive coupling member, the combination ofa grid-controlled dampertube connected in parallel Withat least a portion of said inductive coupling member, a condenser, a diode damper tube connected in series with said condenser, the series vcombination of said condenser and. lsaiddiode damper tube also being connected in parallel with at least a portion of said inductive couplingmemben-and means connecting said condenser. to said power output tube through at least-a portion of said inductive cou-` pling. memberzo thatthe energy stored in said condenser during operation of Asaid circui-twill be effective Atogincrease the normalcurrentout# put of said power output tube.

l0. A cathode ray deflection vcircuit comprising, a deection coil, means for supplying deecting current to said coil, two damping circuits for said coilconnected in` parallel, one said damping circuit comprising a grid-controlledY damper tube, the other damping circuit comprising a diode damper tube and sa storage condenser connected in series, the internal resistance oiY said diode beingl -low compared to the impedance of said grid-controlled tube lwhereby a portion of the reactive energy developed in said deflection coil is stored in said condenser, and meansA connecting said condenser effectively in series With said means for supplying deflecting current.

EDWIN L. CLARK,

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

`UNITED STATES PATENTS Number

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