Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N3/00—Scanning details of television systems; Combination thereof with generation of supply voltages
  • H04N3/10—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical
  • H04N3/30—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical otherwise than with constant velocity or otherwise than in pattern formed by unidirectional, straight, substantially horizontal or vertical lines
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N3/00—Scanning details of television systems; Combination thereof with generation of supply voltages
  • H04N3/10—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical
  • H04N3/16—Scanning details of television systems; Combination thereof with generation of supply voltages by means not exclusively optical-mechanical by deflecting electron beam in cathode-ray tube, e.g. scanning corrections
  • H04N3/22—Circuits for controlling dimensions, shape or centering of picture on screen
  • H04N3/23—Distortion correction, e.g. for pincushion distortion correction, S-correction
  • H04N3/233—Distortion correction, e.g. for pincushion distortion correction, S-correction using active elements

Definitions

• a line deflection circuit for a picture tube e.g. for a television receiver or a monitor
• the electron beam is deflected from the left to the right edge of the picture during the running time of a line. This is followed by a return time during which the electron beam returns to the left edge of the image at high speed.
• a relatively high voltage peak arises at the line output stage transistor and the line deflection coil, which must be taken into account when dimensioning these parts.
• HDTV line duration
• a symmetrical deflection Line deflection current for example, a triangular course from a negative value to a positive value during one line and from this positive value to the negative value during the subsequent line.
• the deflection current can also have a sinusoidal shape in approximation to this triangular shape.
• the maxima of the current are each between two lines outside the screen and the zero crossings in the middle of the line.
• a rectangular voltage at half the line frequency is applied to the deflection coil via a corresponding circuit.
• this square-wave voltage generates a triangular current in the deflection coil, namely with a positive square-wave voltage with a positive slope and with a negative square-wave voltage with a negative slope, the zero crossing of the deflection current being in the middle of the line and the deflection current in the two halves of the line lead time before and after the zero crossing runs symmetrically with the opposite sign.
• the desired course of the deflection current is not always given in practice. This means that the deflection current does not have its zero crossing in the middle of the line during a line duration and also has a differently curved course in the two line halves. This causes errors in the geometry and brightness of the displayed image when displaying the image.
• the invention is based on the object of avoiding the described deviation of the current profile from the target profile with simple circuitry means.
• the actually flowing deflection current is detected by means of a resistor or the voltage at the deflection coil causing the deflection current.
• the solution is based on the fact that the deviations from the described target position can be recognized from these two values. Control variables are obtained from this. These control the deflection current via the amplifier according to the principle of negative feedback or control circuit in such a way that it describes the. assumes a desired course during the line.
• the deflection current can be influenced for the purpose of correction by means of the amplifier as a function of the deflection current, as a function of the voltage applied to the deflection coil, or else in combination on the basis of both criteria.
• the zero crossing of the deflection current is additionally detected and an additional control voltage is obtained from its deviation from the center of the line. which additionally controls the amplification of the voltage proportional to the deflection current.
• influences on the zero position of the deflection current can be compensated for by temperature changes on the deflection unit.
• This control voltage is not a dynamic control voltage that changes during a row, but rather a DC voltage-like, that is to say slowly changing control voltage.
• FIG. 1 shows an embodiment of the invention
• Circuit and Fig. 2 curves to explain the operation.
• two power transistors T1, T2 are alternately controlled and blocked alternately in a push-pull manner by two switching voltages U1 ⁇ U2.
• the switching voltage U1, U2 have half the line frequency, that is 16 kHz, with one half-wave of the switching voltage U1, U2 being equal to one line duration.
• the free-wheeling diodes D1, D2 and capacitors C1, C2 are connected in parallel to the transistors T1, T2 for the temporary current transfer.
• Cs is the so-called tangent capacitor, which is used for DC decoupling and for tangent equalization.
• the right end b of Cs is not grounded, but is connected to the output a of the amplifier VI via the resistor R4.
• Fig. 2 shows the voltages and currents in Fig. 1.
• the dashed line shows the actual course that occurs in practice and deviates from the target course without corrective measures.
• the voltage Ucb between the points c and b which determines the value of the deflection current ia, has the drop shown in broken lines due to the voltage drop across the resistors R4 and R5. As a result of this voltage drop, the course of the current shown in dashed lines generally arises.
• ge to achieve the ideal current profile of ia, which are described in the following in succession.
• the voltage between the points b and a which is proportional to the deflection current, is fed to the inputs of the differential amplifier V2.
• a voltage is generated which is proportional to the deflection current ia to the input f of the amplifier VI, which is fed back via the resistor R6 and works as an analog linear amplifier.
• the manipulated variable Usl changes the voltage Ua at point a in accordance with the actually flowing deflection current ia.
• the deflection current ia has the desired profile if the voltage UCB via the inductance of the deflection coil and the capacitor Cs AS an exactly rectangular shape, that is constant during ei ⁇ ner line period each.
• the voltage Ua at point a is controlled by the manipulated variable Usl so that the voltage Ucb is exactly rectangular is rmig, that is, has a constant value during a line duration and does not fall according to the dashed line. With the amplifier VI, the voltage Ua is thus generated at point a. The voltage Ua thus compensates for the voltage drop of the voltage Ucb shown in dashed lines. It is a negative feedback to point a in the sense that the deflection current generally corrects itself.
• the manipulated variable Usl is a dynamic manipulated variable that changes during a line duration.
• a pulse shaper or a distortion can be arranged in the path of the manipulated variable Usl, which changes the course of the manipulated variable Usl during one line in order to correct the deflection current properly.
• the target course of the deflection current ia means that ia has its zero crossing in the middle of the line and in the two Halves of lines on both sides of the zero crossing run symmetrically in mirror image with opposite signs.
• the voltage Ud at point d is fed to comparison stage 1, which on the other hand is supplied with a comparison voltage Uv with an exactly rectangular profile and half the line frequency. In comparison level 1, the deviation between Uv and Ud is registered. A manipulated variable Us2 is obtained from this, which represents the undesired drop in Ud each during a line period. Such a drop in the voltage would likewise affect the deflection current.
• the manipulated variable Us2 also acts via the resistor R2 on the input f of the amplifier VI in addition to the manipulated variable Usl. Us2 is also able to change the voltage Ua during a line duration such that the deflection current generally has the desired course during the line duration.
• the manipulated variables Us1 and Us2 can each serve for correcting the deflection current, generally or individually, as shown.
• the voltage at the point e which is proportional to the deflection current, is additionally fed to the zero crossing detector 2 and the result of the time comparison stage 3.
• the voltage Ud is fed to the detector 4, which detects the elanks of Ud and feeds the result of the time comparison stage 2.
• stage 3 the zero crossings of ia and the pulse edges of Ud are compared with one another in their temporal position.
• a counter is started in stage 3, which is in positive direction counts upwards.
• the counter is stopped and is controlled in the opposite direction by t2 or t3-t4, that is to say up to the next edge from Ud. If the zero crossing of ia is at t3, that is to say in the middle of the line duration from tl-t4, the counting result at t4 is zero and the control voltage Ur is also zero. If, owing to a drop in the voltage Ud and / or the voltage Ucb, as shown in dashed lines, the current generally assumes the dashed course, its zero crossing t2 is shifted with respect to the desired zero crossing t3. The counter is incremented positively from tl-t2 and negatively from t2-t4.
• the count result is negative.
• the generated control voltage Ur changes in the negative direction.
• the control voltage Ur controls the controllable resistor R3 and thus the negative feedback and amplification of the amplifier V2. This changes the voltage at point a in the sense that the current resumes its zero crossing at the desired time t3. If the zero crossing t2 is later than t3, Ur becomes positive and changes the resistance R3 in the opposite direction.
• the control with Ur has the effect that the zero crossing of ia is always in the desired manner at t3, that is to say in the middle of the line. If this condition is met, it can be assumed that the current generally has the desired profile symmetrical to the zero crossing t3.
• Ur is an equilibrium-like control voltage, which brings about slow regulation. It serves in particular to compensate for deviations in the zero crossing from ia by temperature changes, that is to say in particular changes in the values of R4 and R5 in the sense of long-term control.
• the voltage Ua shown in full line in FIG. 2 is the voltage effective at point a for the correct correction of the deflection current ia, ie for the course shown in full line.
• the curve of Ua shown in broken lines applies in the event that the compensation of Ua is not is sufficient and the deflection current generally takes the dashed course.
• the operating voltage UB of + 200 V applied to the switch S1 is constant.
• This voltage can additionally be amplitude-modulated in order to achieve a correction of the geometry of the deflection grid. If the line deflection current e.g. for an east / west correction to be modulated according to the vertical frequency steering voltage, the operating voltage ÜB can additionally be amplitude modulated by a vertical frequency voltage. Then the amplitude of the deflection current would generally be modulated at a vertical frequency for an east / west raster correction.
• the voltage Ua at point a so that the voltage effective at the deflection coil AS and thus the deflection current ia are therefore regulated on the basis of three criteria, first dynamically as a function of ia itself by means of the manipulated variable Usl, depending on the span applied to the deflection coil AS ⁇ voltage Ud also dynamically by means of the manipulated variable Us2 and additionally statically as a function of the position of the zero crossing of the current generally by means of the statically acting control voltage Ur.
• stages 1-4 shown in Fig. 1 e.g. commercially available comparators of the type LM2901 from Motorola can be used.

Landscapes

• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Details Of Television Scanning (AREA)
• Structure Of Telephone Exchanges (AREA)
• Use Of Switch Circuits For Exchanges And Methods Of Control Of Multiplex Exchanges (AREA)
• Pharmaceuticals Containing Other Organic And Inorganic Compounds (AREA)
• Compositions Of Oxide Ceramics (AREA)
• Saccharide Compounds (AREA)
• Supports For Pipes And Cables (AREA)
• Paper (AREA)

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• 1987
  • 1987-04-02 DE DE19873711173 patent/DE3711173A1/de not_active Withdrawn
• 1988
  • 1988-03-29 AT AT88105125T patent/ATE73287T1/de active
  • 1988-03-29 EP EP88903221A patent/EP0359749A1/de active Pending
  • 1988-03-29 US US07/411,486 patent/US4956585A/en not_active Expired - Fee Related
  • 1988-03-29 ES ES198888105125T patent/ES2030454T3/es not_active Expired - Lifetime
  • 1988-03-29 WO PCT/EP1988/000259 patent/WO1988007799A1/de not_active Application Discontinuation
  • 1988-03-29 JP JP63503310A patent/JP2716495B2/ja not_active Expired - Lifetime
  • 1988-03-29 EP EP88105125A patent/EP0285114B1/de not_active Expired - Lifetime
  • 1988-03-29 DE DE8888105125T patent/DE3868657D1/de not_active Expired - Fee Related
  • 1988-12-02 KR KR1019880701586A patent/KR890700986A/ko not_active Application Discontinuation
• 1989
  • 1989-09-29 DK DK480089A patent/DK480089D0/da not_active Application Discontinuation
  • 1989-10-02 FI FI894654A patent/FI894654A/fi not_active Application Discontinuation
• 1992
  • 1992-06-02 GR GR920401119T patent/GR3004770T3/el unknown

Non-Patent Citations (1)

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