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application note tv east/west correction circuits AN393/1193 summary page i general principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 i.1 introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 i.2 diode modulator principle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 i.3 pulse-width modulator principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 i.4 general considerations to generate the correction parabola . . . 7 i.5 adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 i.5.1 horizontal size adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 i.5.2 pin cushion correction adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 i.5.3 trapezium correction adjustment (keystone correction) . . . . . . . . . . . . . . . . . . . . . . . . . 11 i.6 products presentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 ii tea2031a general description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 ii.1 introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 ii.2 parabola generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 ii.2.1 multiplier stage operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 ii.2.1.a operation without keystone correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 ii.2.1.b operation with keystone correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 ii.2.1.c example of applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 ii.3 line saw tooth generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 ii.3.1 role of resistors r7, r8, rt1 and d2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 ii.3.2 role of diode d1 and capacitor c3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 ii.4 output stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 ii.4.1 operation of the output stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 ii.4.1.a output in the low stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 ii.4.1.b output in the high stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 8 ii.4.1.c output with commutation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 ii.4.1.d conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 ii.4.2 operation in association with the diode modulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 ii.5 selection of the values of capacitors c2 and c3. . . . . . . . . . . . . . . . . . . 20 ii.5.1 selection of c3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 ii.5.2 selection of c2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 ii.6 application example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 iii tda4950 - tda8145 general description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 iii.1 introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 iii.2 description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 iii.3 application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 1/32
summary (continued) page iv tda8146 general description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 iv.1 introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 6 iv.2 input amplifier and rectifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 iv.3 vertical clamping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 iv.4 reference and starting circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 iv.5 parabola generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 iv.6 pulse-width modulator and output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 iv.7 application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 v tda8147 general description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 v.1 introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 v.2 input amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 v.3 voltage reference and starting circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 v.4 pwm modulator and output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 v.5 application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1 i - tv east/west correction general principles AN393-01.eps figure 1 : test grid on a 110 o color tube i.1 - introduction all color picture tubes which are used in the present tv-sets have a magnetic deflection system. using a homogenous magnetic field, we have generally a pillow-distortion of a rectangular picture on the screen. this is mainly due to the tangens relation between the deflection angle and the beam posi- tion on the screen using a well dimensioned and optimized inhomo- genous magnetic deflection field, this distortion can be eliminated completely for picture tubes with a deflection angle of 90 o . in the same way the pillow- distortion of 110 o deflection tubes can be elimi- nated in the vertical direction (north-south direction). but until now the distortion in the hori- zontal direction (east-west direction) can not elimi- nated with special designed deflection yokes. a distortion remains in figure 1. in order to compensate this effect, the horizontal deflection current in the yoke must be modulated. this means a large amplitude of the deflection current in the middle of the screen and a small amplitude on the top and the bottom of the screen. the general behaviour of the deflection currents is illustrated in figure 2. in this picture t v and t h are the time periods for the vertical and the horizontal deflection. note that the envelope of the horizontal yoke current must be a parabola with the same phase as the vertical saw-tooth current. this means an east/west cor- rection can be reached by modulating the horizon- tal yoke current with a parabola. there are different possibilities to modulate the yoke current. the most convenient modulator is the so-called diode modulator described in the next chapter. tv east/west correction circuits 2/32
t t i horizontal yoke yoke t t v i vertical h AN393-02.eps figure 2 : horizontal and vertical yoke current (t h = 64 m s, t v = 20ms) i.2 - diode modulator principle let us consider the basic circuit of the horizontal deflection unit as shown in figure 3. ltr line transformer v ltr v ly v lm y c c v 0 v m m l l y lm i i ly s 1 s 2 m l y : line yoke l m : modulator coil v m : modulator voltage v 0 : supply voltage s 1 and s 2 : electronic switches AN393-03.eps figure 3 : basic circuit of the horizontal deflection power stage including modulator for the sake of simplicity, the electronic switches (diodes and transistors) are drawn as simple switches s 1 and s 2 . the deflection time t h of 64 m s can be divided in two parts : the scan time t s at which the electronic switches s 1 and s 2 are closed and the flyback time t f (s 1 and s 2 opened). the total time period is the t h = t f + t s (1.1) we assume now that the line trans former l tr have a neglectable high inductance and the time behav- iour is mainly determined by l y , l m , c y , c m . small modifications are necessary to consider also the electrical characteristics of l tr , but they should not be discussed here. during the scan time the inductors l y and l m are directly connected to the voltage sources v 0 and v m : v ly = v 0 - v m s 1 and s 2 closed (scan time) (1.2) v lm = v m (1.3) neglecting any power consumption in possible se- ries resistors, the current in the two inductors in- creases linear in time : i ly = t ( v 0 - v m ) l y (1.4) i lm = t v m l m (1.5) tv east/west correction circuits 3/32
t i ly t ly t v v ltr independent from v m v m v m v m t s t f 0 - v 0 t s 2 lc v ( - 1) AN393-04.eps figure 4 : currents and voltages of the basic circuit since the current i ly and i lm must be zero-symmet- rical (average value = 0), the peak value of i ly and i lm is obtained after half of the scan time t s /2 i ^ ly = t s ( v 0 - v m ) 2 l y (1.6) i ^ lm = t s v m 2 l m (1.7) after this time, s 1 and s 2 are opened and the energy in the inductors l y and l m changes to the capacitors c y and c m . we assume now the same resonance frequency for both lc parts (1.8) l y c y = l m c m = l c (1.8) under this condition, both capacitors c y and c m have its peak voltage at the half of the flyback time t f /2. the energy in the inductors stored at the end of the scan period e l = 1 2 l ( i l ) 2 is then (1.9) completely transformed into the capacitor e c = 1 2 c ( v c ) 2 (1.10) under this condition, we obtain the general equa- tion for the peak voltage in the middle of the flyback period v ^ c = - i ^ l ? ` ` l c + v init (1.11) this voltage is the addition of the initial voltage and the voltage increase due to the energy transfer. with (1.6) and (1.11) we get v ^ ly = v ^ cy = - v 0 - v m ? ````` ` l y c y t s 2 + ( v 0 - v m ) = ( v 0 - v m ) ( 1 - t s 2 ? ``` ` l c ) (1.12) in the same way (1.7 and 1.11) we obtain v ^ lm = v ^ cm = v m ( 1 - t s 2 ? ``` ` l c ) (1.13) the resulting peak voltage during the flyback time at the line transformer is then v ^ ltr = - v ^ ly - v ^ lm = v 0 ( t s 2 ? ``` ` l c - 1 ) (1.14) please note that in this circuit, the horizontal flyback voltage v ltr (1.14) is independent from the modu- lation voltage v m , though the yoke current i ly can be changed via the modulator voltage v m (see 1.6) an overview of the currents and voltages is given in figure 4. tv east/west correction circuits 4/32
y c c v 0 m l l y line transformer c s v m m t e.g. bu508a or s2000afi m i m AN393-05.eps figure 5 : standard diode modulator with class-a modulator driver y c c v 0 m l l y line transformer c s l s i s a v a t m AN393-06.eps figure 6 : standard diode modulator with class d modulator driver (pulse-width modulator) for a practical application, a large capacitor c s can be inserted in series to the yoke to get an s-correc- tion of the deflection current i ly . simultaneously, the voltage v m can be grouded to have a simpler handling of the modulator driver. the switch s 1 is a standard high voltage power transistor (e.g. bu508a or s2000afi), the switch s 2 can be re- placed by 2 diodes as shown in figure 5. normally, the current i m into the modulator voltage source is positive and v m must only be realized as a variable resistor (e.g. transistor t m ). many manufacturers use this simple diode modu- lator with such active load. a disadvantage of this application is the power consumption in the power transistor t m (~2w). under ideal conditions, v m should have no power consumption (average i m = 0), but in practice the coils and the line trans- former are not free from parasitic resistors. further- more a reasonably large power is used from the various loads on the line transformer. an improvement from the power consumption point of view is the use of a switched power stage v m . for this purpose, an additional inductance l s (5...20mh) is used and connected as shown in figure 6. point a is biased from a pulse-width modulated rectangular wave. the frequency is arbitrary, for a simple pulse-width modulator, the horizontal line frequency is used normally. tv east/west correction circuits 5/32
l v t out v cc to diode modulator s s i v out k r k c r in v par c s flyback pulses from the line transformer + v par yoke i vertical t t AN393-07.eps figure 7 : pulse-width modulator i.3 - pulse-width modulator principle the pulse-width modulator for driving the diode modulator contains mainly one power comparator with the external circuitry shown in figure 7. the working frequency is determined by the linear saw-tooth voltage biasing the positive comparator input. it is generated by the flyback pulses of the line transformer. the current sink on the positive input discharges the capacitor c s during the scan time t s and yields the negative slope of the saw- tooth voltage. the negative input is biased from a parabola volt- age, its generation is discussed later. to improve the performance of this pulse-width modulator, a feedback path r k is provided com- pensating variations in the power supply v cc of the comparator. the capacitor c k together with r in and r k serves as a low-pass filter to suppress the line frequency coming from the comparator output. if the current i s in the inductor l s (see figures 6 and 7) is only positive, the output stage can have a simple darlington transistor and a diode as seen in figure 8. if the darlington stage is switched on, the current i s is flowing through t a and t b into ground. other- wise, the diode d is conducting and i s flows into the supply voltage. the power, consumed normally in l m (see fig- ure 5) is then redelivered into this supply voltage. a greater flexibility in the design of the diode modu- lator can be reached, if the current i s is allowed to have negative values. for this case, the compara- tor power stage must be realized as push-pull stage (see figure 9). due to the voltage drop across the transistors and diodes, the transition from positive values i s and negative values i s yields a voltage step on the output as illustrated in figure 10. in this case the steps in the output voltage produce an additional undesired modulation of the yoke current. then you can see some irregularities in the vertical lines of the test grid on the screen. with the aid of a reasonable large fedback factor (small r k , small c s , large parabola amplitude) this effect be- comes neglectable. tv east/west correction circuits 6/32
+ d v t t il cc a b ss to diode modulator AN393-08.eps figure 8 : comparator output stage, only posi- tive modulator current i s is allowed v il cc ss + out AN393-09.eps figure 9 : comparator output push-pull stage, negative and positive modulator cur- rent i s allowed t t v v i out cc s AN393-10.eps figure 10 : voltage on the comparator output by zero crossing of i s i.4 - general considerations to generate the correction parabola the correction parabola which drives the pulse- width modulator (figure 7) must have the same frequency and phase as the vertical deflection current in the yoke. therefore, the parabola can be generated directly from the vertical saw-tooth sig- nal which drives the deflection output stage. prin- cipally there are two different kinds for generating the parabola: a) integrator-network (linear) b) functional-network (non linear) let us consider first the integration method : the vertical saw-tooth signal can be described with the following simple equation, valid for one period s saw-tooth (t) = a t t v 0 < t < t v (1.15) where a is the amplitude, t v the time period and t the time. integrating this signal we get 0 t s saw - tooth ( t ) dt = 0 t a t t v dt = a 2 t v t 2 (1.16) since the relation between the current and the voltage on a capacitor is given by v c (t) = i c ( t ) dt (1.17) the parabola can be obtained directly from the coupling capacitor c y in the vertical output stage as illustrated in figure 11. due to the aging and the temperature dependence of this (electrolytic) capacitor c y , some manufac- turers prefer to gener ate the parabola from the voltage drop across r y (v ry ) with the aid of a separate integrator. tv east/west correction circuits 7/32
v c ry v v t vertical yoke dc - feedback ac - feedback v c ry v cy ry i yoke AN393-11.eps figure 11 : vertical output stage and corresponding voltages t t s s parabola a 0 saw-tooth AN393-12.eps figure 12 : generation of the parabola with functional network due to the small amount of active and passive components, this integration method is the usual method to realize the east/west correction circuit with discrete elements. the functional network realization requires a quite larger amount of active components and is there- fore especially suited for integrated circuits. the input signal for this kind of parabola generation is also the vertical saw-tooth signal corresponding to (1.15). with the aid of a functional (square) net- work, the square of this signal can be formed according to the following equation : s parabola = k ( s saw - tooth - s 0 ) 2 = k ( a t t v - a 0 ) 2 (1.18) and is illustrated in figure 12. thereby, k is the gain and a 0 is a dc-level which allows to adjust the symmetry of the parabola ("trapezoidal" or "keystone" correction). comparing the two methods, the following proper- ties are evident : - the parabola amplitude using the integration method is frequency dependent : assuming a constant amplitude of the saw-tooth s ignal, the amplitude of the parabola is linear in the time period t v (see 1.16) . this means different adjust- ments between 50 and 60hz tv-sets. the func- tional (square) method gives a frequency-independent amplitude of the parab- ola, if a constant saw-tooth signal is provided. - during the flyback time of the saw-tooth signal, the functional network produces a second (para- sitic) parabola as shown in figure 12 tv east/west correction circuits 8/32
v i yoke par t t AN393-13.eps figure 13 : modified parabola : constant during the flyback time although this parasitic parabola is present during the vertical flyback time (dark screen) this small parabola (like a spike) produces a damped oscilla- tion of the diode modulator. the result is a damped sinusoidal vertical line on the top of the screen, if a test-grid is on the screen (the vertical lines are similar to a crutch-stick). the maximum amplitude of this oscillation is pre- sent on the left and right top of the screen. though its amplitude is normally only about 3mm, this effect must be suppressed. this can be reached by two different methods : - the linear saw-tooth voltage generating the pa- rabola must have an extremely small flyback time. then the very small parasitic parabola is inte- grated in the capacitor c k of the comparator and has no effect (see figure 7). the saw-tooth volt- age coming from the vertical oscillator fulfills this requirement wherefore the deflection yoke-cur- rent has a too large flyback time. - another possibility is to hold the parabola signal constant during the flyback time as illustrated in figure 13. this behaviour can be reached by providing a parabola output limitation and then overmodulat- ing the functional network during the flyback time. overcoming the problems of the parasitic parabola, the functional method should be preferred due to the independence of the frequency (50/60hz com- patibility). the nonlinearity which forms the parabola can be realized in two different ways : - use of an analog multiplier - forming a nonlinear network by piece wise lineari- zation. i.5 - adjustments i.5.1 - horizontal size adjustment adjustment of horizontal amplitude is made by modifying the mean cyclic ratio (duty factor) of the output pulses. when this mean cyclic ratio is mini- mum, the picture width is maximum, because the output is more frequently in the low state, and therefore the highest current is drawn from the diode modulator and the deflection current is maxi- mum. to change the mean cyclic ratio of the pulse train (in addition to the change due to the parabolic shape of the signal) it is necessary to change the continuous level of the sawtooth pulse train (see figure 14). the rise of the continous level of the parabola is due to the increase of the cyclic ratio, as we have seen above. the value of pincushion correction is not modified since the parabola peak-to-peak am- plitude is kept the same. only the mean cyclic ratio varies, i.e. also the horizontal scan width. i.5.2 - pincushion correction adjustment pincushion cor rection is made by varying the peak- to-peak amplitude of the parabola. the greater this amplitude,the greater the variation of the output signal cyclic ratio is between the ends and the top of the parabola, and therefore the more important is the parabolic modulation of the current drawn from the diode modulator (see figure 15). tv east/west correction circuits 9/32
t t t deflection current pwm output signal line sawtooth signal and vertical parabola broad picture narrow picture AN393-14.eps figure 14 : horizontal size adjustment t t t deflection current pwm output signal slight pincushion correction pronounced pincushion correction line sawtooth signal and vertical parabola AN393-15.eps figure 15 : pincushion correction adjustment tv east/west correction circuits 10/32
t t t deflection current pwm output signal line sawtooth signal and vertical parabola picture broad at top and narrow at bottom picture narrow at top and broad at bottom top of picture bottom of picture bottom of picture top of picture AN393-16.eps figure 16 : keystone correction i.5.3 - trapezium correction adjustment (keystone correction) trapezium correction is made by modifying the symmetry of the left and right sides of the parabola (figure 16). i.6 - products presentation all the east/west correction devices are with class d diode modulator driver. concerning the frame parabola generation, tda4950, tda8145 and tda8146 use a non-linear network whereas tea2031a uses an analog multiplier. tda4950 and tda8145 generate a parabola with a fixed shape; this shape is different between the two devices and makes the tda4950 intended for standard crt and tda8145 for square tubes. these two devices have a parasitic parabola sup- pression (during vertical flyback time) by current limitation. tda8146 has a programmable parabola shape generation by segments which makes it suitable for different crts. it has also a parasitic parabola suppression by pulse during vertical fly- back. all the devices can support a keystone correction adjustment (parabola symmetry) and have 50/60hz capability. some others adjustments are possible (picture width...). finally, another available device the tda8147 has been designed for use in the east/west pincushion correction by driving a diode modulator but since this device has not the parabola generator and is drived by a pwm, it is very useful in digital tv-sets. a detailed description about all the devices is done in the next chapters. tv east/west correction circuits 11/32
comparator multiplier 87 6 5 12 3 4 tea2031a v cc 12 k . (i - i ) 2 v ref 6.3v i 1 i 2 50 m a 120 m a AN393-17.eps figure 17 : block diagram ii - tea2031a general description ii.1 - introduction the tea2031a circuit comprises (see figure 17) : an analog multiplier that uses a frame sawtooth signal applied on pin 1 so that the current on pin 7 has a parabolic modulation. this multiplier operates in current differential mode and uses a reference dc voltage, selected accord- ing to the continuous level of the sawtooth voltage, and applied on pin 2. the level of this dc voltage also serves to correct trapezium distortion. - a reference voltage available on pin 3 that can be used (via a voltage divider) to provide input 2 of the multiplier with a reference voltage. - a current generator, producing a line frequency sawtooth signal by integrating the line flyback signal and generating current available on pin 8. - a comparator controlling the output stage by us- ing the line sawtooth signal applied on its +input (pin 8) and the parabolic signal generated by the multiplier and applied on its -input (pin 7). an output stage that can absorb or deliver current and comprises a diode connected to the dc volt- age supply in order to limit the voltage applied on the output terminal during line flyback. this stage enables the diode modulator of the line scan circuit to be driven directly with a maximum current of 0.5a. this maximum current that the output can absorb is not limited by the size of the transistors but by the maximum power dissipated by the package (minidip). ii.2 - parabola generation using a fixed continuous current and a vertical sawtooth current, the multiplier generates an out- put current on pin 7 with parabolic modulation. ii.2.1 - multiplier stage operation the multiplier inputs (pins 1 and 2) operate in current differential mode (figure 18). tv east/west correction circuits 12/32
v cc v v ref v dc 7 i 7 i 7dc 7 ref v 1 0v 0v 0a r 5 rr 12 r 3 i 1 ii 23 k (l1 - l2) 2 tea2031a 12 3 v = 6.5v AN393-18.eps figure 18 : multiplier stage the output current is given by : i 7 = i 7dc - k ( i 1 - i 2 ) 2 i 7dc and k depend on the current reference on pin 3. remarks : as we can see, the two inputs can be inverted and the slope of the sawtooth has no influence on the parabola shape. ii.2.1.a - operation without keystone correction in order to eliminate supply and thermal drift influ- ences, r 1 is taken equal to r 2 . in this case, v 1dc = v 2dc (figure 19). ii.2.1.b - operation with keystone correction in order to correct keystone correction, v 2 voltage becomes adjustable. in this case, the parabola shape presents a dissymmetry (figure 20). ii.2.1.c - example of applications 1. sawtooth coming from the horizontal:vertical processor (e.g. tda8185, tea2028b, ...) in this case, v 1dc = 2.5v (figure 21). for practical reason, the dc voltage comes from internal voltage reference.impedance value seen between pin 3 and ground must be 22k w for best conditions of operation (to have the good internal current reference). 2. sawtooth coming from the vertical output stage (figure 22) in this casev 1dc = 0v and r1 = r2 + 1 2 rt2 tv east/west correction circuits 13/32
t t v 1 v 7 v v 7h 7l v 2 v 7l1 v 7l2 21 v = v dc = 2.5v 4v 3v 2.5v 2v 1v 10ms 0 20ms 10ms 0 AN393-19.eps figure 19 : operation without keystone correction t t v 1 v 7 v v 7h v 2 21 4v 3v 2.5v 2v 1v 10ms 0 20ms 10ms 0 7b v 7a 2 v = 3v 2 v = 2v v v dc AN393-20.eps figure 20 : operation with keystone correction 1234 tea2031a + 3.8v + 2.5v + 1.2v 0v typical frame saw-tooth keystone adjustment 3v 2v 39k w 39k w 10k w i reference 3 4.7k w 3.9k w AN393-21.eps figure 21 : sawtooth coming from h/v processor 1234 tea2031a 3 22k w i i 2 i 1 r r 3 2 r 1 r t2 0v vertical yoke AN393-22.eps figure 22 : sawtooth coming from vertical output stage tv east/west correction circuits 14/32
tea2031a 87 output parabola (50hz) line sawtooth line flyback (16khz) r7 d2 rt1 r8 d1 c3 i 8 i 7 AN393-23.eps figure 23 : line sawtooth generation ii.3 - line sawtooth generation the line sawtooth signal is applied as a reference at the +input terminal of the comparator. it is ob- tained by integrating the line flyback and the con- stant current discharge of capacitor c3 in pin 8 (figure 23). ii.3.1 - role of resistors r7, r8, rt1 and d2 by means of the voltage divider bridge comprising resistors r7, rt1 and r8, a signal that is the image of the line flyback signal applied on r7, is obtained on the slide contact of potentiometer rt1. the peak amplitude of this signal depends on the nomi- nal voltage of the zener diode d2 and on the adjustment of rt1. the role of zener diode d2 is to maintain a constant amplitude of the signal on the slide contact of rt1 whatever the variations in amplitude of the line flyback signal. this diode d2 can be also replaced by a single diode connected to a regulated 12v or 15v power supply. ii.3.2 - role of diode d1 and capacitor c3 during line flyback, diode d1 rapidly charges ca- pacitor c3 at the potential available on the s lide contact of rt1. then during line scanning, d1 is blocked and c3 is discharged at constant current (about 50 m a) through pin 8. the peak-to-peak amplitude of the line frequency sawtooth signal obtained in this way depends di- rectly on the value of capacitor c3 since it is def ined by the discharge current of the capacitor and the line period (figure 24). this amplitude can be calculated using the fo llow- ing equation : v 8 (peak-to-peak) = dt i 8 c3 where dt = duration of line and i 8 = current in pin 8. the continuous level of this sawtooth signal is set by adjusting potentiometer rt1 (figure 25). tv east/west correction circuits 15/32
t 0v voltage on rt1 slide contact continuous level 11s 53s sawtooth wave on c3 AN393-25.eps figure 25 : continuous level of swatooth signal for two different adjustments of rt1 line flyback voltage on r7 line flyback voltage on rt1 slide contact sawtooth signal on c3 c3 = 10nf c3 = 3.3nf same peak level t t 0v 0v 250mv 0.8v AN393-24.eps figure 24 : peak-to-peak amplitude of sawtooth signal versus two different values of c3 (with rt1 = constant) ii.4 - output stage the output stage is controlled by the comparator fed by signals applied on its inputs, i.e. the saw- tooth signal at line frequency on +input (pin 8) and the parabola at vertical frequency on -input (pin 7) (see figure 26). the comparison between the 50hz parabola and the sawtooth signal at line frequency (16khz) pro- duces pulses at line frequency with a duty cycle that is modulated at vertical frequency. this allows, by means of the diode modulator, the modulation of the line scanning current during each field period in order to carry out the pincushion correction (or east/west correction) (see figure 27). the role of the filter c2 and rt3 + r6 is to suppress the line frequency of the feedback output signal. tv east/west correction circuits 16/32
tea2031a 8765 c2 r5 rt3 r6 i v cc r5 i i 8 i 7 i c2 5 i 8 i 7 AN393-26.eps figure 26 : output stage 64s 20ms continuous level output pin 5 t t input pin 7 input pin 8 0v 0v AN393-27.eps figure 27 : pwm output signal (with adaptation of time scales) ii.4.1 - operation of the output stage the operation of the output stage can be consid- ered as 3 separate cases according to the 3 possi- ble states of output pin 5. ii.4.1.a - output in the low state (figure 28) in this case resistances r6 and rt3 are connected to the ground, therefore they are in parallel with r5, according to the following diagram. the continuous level and the peak-to-peak ampli- tude of the parabola are at their minimum when the rt3 value is minimum. it is possible to calculate the voltage for a given point of the parabola (pin 7) using the following equation : v 7b = i 7 r5 ( r6 + rt3 ) r5 + r6 + rt3 the capacitance of c2 is neglected as this capaci- tor is equivalent to an open-circuit at vertical fre- quency. tv east/west correction circuits 17/32
tea2031a i 8 765 7 r6 rt3 r5 c2 saturated v v < v cc 7 8 0v 0v 0v t 7 v output low state AN393-28.eps figure 28 : output in low state tea2031a i 8 765 7 r6 rt3 r5 c2 v v < v cc 7 8 0v t 7 v continuous level is maximum when rt3 is minimum high state output cc v - 1 v d i 5 AN393-29.eps figure 29 : output in high state ii.4.1.b - output in the high state in this case, resistances r6, rt3 and r5 form a voltage divider bridge which returns on pin 7 and capacitor c2 part of the continuous voltage avail- able on the output terminal that is added to the parabola voltage. the equivalent circuit diagram is the following : see figure 29. it is possible to calculate the voltage for a given point of the parabola (pin 7) with the following equation : v 7h = i 7 r5 ( r6 + rt3 ) r5 + r6 + rt3 + v 5 r5 r5 + r6 + rt3 ii.4.1.c - output with commutation in this case and if capacitor c2 is eliminated, figure 30 gives the signal obtained on pin 7. it corresponds exactly to the levels and amplitudes of the parabolas for output in the high state and the low state, linked by 16khz commutations. in normal circuit configuration, capacitor c2 is con- nected and constitutes a filter with r6 and rt3. the preceding signal is filtered and is transformed into the signal shown in figure 31. the 16khz line frequency component has disap- peared in the signal and only the 50hz parabola remains, but slightly modulated at line frequency by the c2 charge when the output is in the high state, and by the c2 discharge when the output is in the low state; this gives a tiny triangular modula- tion signal. so the continuous level of the parabola depends only on the cyclic ratio of the output pulse train. this level can be calculated by means of the following equation : v mean = m v 7h + (1 - m) v 7b where m : output pulse cyclic ratio v 7h : mean level on pin 7, output blocked in the high state v 7l : mean level on pin 7, output blocked in the low state tv east/west correction circuits 18/32
20ms parabola level for high state output 16khz commutations parabola level for low state output t 0v v 7 AN393-32.eps figure 30 : output with commutation (without c2) v 0v 7 mean continuous level as a function of the cyclic ratio of the output pulses t AN393-31.eps figure 31 : output with commutation (with c2) we see that, when the cyclic ratio increases, the continuous level of the parabola also increases and approaches its maximum level when the output is in the high state. conversely, when the cyclic ratio decreases, the continuous level of the parabola also decreases since it approaches its minimum continuous level when the output is in the low state. ii.4.1.d - conclusion for a given parabolic current i 7 , the parabola peak- to-peak amplitude depends only on resistance val- ues r5,r6 and rt3. therefore by adjusting rt3, it is possible to obtain a more or less pronounced parabola and so adjust the importance of pincush- ion correction. the continuous level of the parabola depends prin- cipally on the mean cyclic ratio at the output, and much less on the adjustment of rt3. ii.4.2 - operation in association with the di- ode modulator (see figure 32) in the majority of cases, the system operates by drawing more or less high current from the modu- lator through the connecting inductor. the current through terminal pin 5 of tea2031a is entering into the circuit. it flows, either to the ground when the output is in the low state, or to v cc through the internal diode when the output is in the high state and the output voltage tends to exceed v cc . the circuit can also produce current. tv east/west correction circuits 19/32
tea2031a 8765 v cc 1234 comp v cc ht eht ly lm ls line flyback AN393-32.eps figure 32 : operation with diode modulator t voltage at pin 7 current in connecting inductor ls line deflection current t 0a t 0a 0v AN393-33.eps figure 33 : output oscillagrams ii.5 - selection of the values of capacitors c2 and c3 correct operation of tea2031a depends par tly on the choice of these values for two reasons : - for a given amplitude of the parabola, the impor- tance of final pincushion correction at the output of tea2031a is determined by defining, by means of c3, the amplitude of the line sawtooth wave. - the absence of oscillation at circuit output is con- trolled through adjustment of the value of c2 as described below. ii.5.1 - selection of c3 as seen before (chapter ii.3.2), the value of c3 and only this value (in the limits of the available voltage on the slider of rt1) can fix the value for the amplitude of the line sawtooth wave. now this amplitude must be greater than the parabola am- tv east/west correction circuits 20/32
plitude (pin 7) but not so far in order to have a correction amplitude sufficient but permitting also an horizontal amplitude adjustment : - if the line sawtooth wave and the parabola have the same amplitude, the pincushion correction is maximum but the horizontal amplitude adjust- ment range is non-exutent - if the line sawtooth amplitude is much greater than the parabolas one, we will have a large range for the horizontal amplitude adjustment, but it will be to the detriment of the pincushion correction amplitude. once the desired line sawtooth amplitude has been fixed, we can calculate the value of c3 with the following formula c3 = dt i 8 v 8 where dt : line scan duration (around 53 m s) i 8 : pin 8 current (around 50 m a) v 8 : line sawtooth peak-to-peak amplitude (pin 8) ii.5.2 - selection of c2 the selection of c2 is related to the values of r5, r6 and rt3. the value of c2 must be large enough to avoid any risk of oscillations at output for the entire range of adjustment of potentiometers rt1 and rt3. the value of c2 must be small enough not to influence the shape of the vertical frequency parabola. ii.6 - application example a typical application diagram is given in figure 34. tea2031a 8765 1234 cc line flyback c2 22nf r5 100k w rt3 1m w c1 10 m f r6 33k w v 24v c3 1.8nf d1 1n4148 rt1 2.2k w r7 2.2k w r8 470 w d2 bzx 46c15 3.8v 2.5v 4.2v r1 39k w r2 39k w r3 10k w rt2 4.7k w r4 3.9k w typical frame sawtooth l1 6.3mh output (to diode modulator) AN393-34.eps figure 34 : typical application tv east/west correction circuits 21/32
iii - tda4950 - tda8145 general description iii.1 - introduction the tda4950 and tda8145 consist mainly of 5 parts as seen in the simplified circuit diagram (fig- ure 35). 1. full-wave rectifier for the input current i in . 2. current limiter in order to limit the rectified current i in to the maximum value of 40 m a (with this functional block a suppression of the parasitic parabola is possible, see chapter i.4). 3. parabola network producing the current i a = k(i in ) 2 (k = constant). 4. comparator and output stage working as a pulse-width modulator for driving the diode modulator. 5. voltage reference and current reference which produces the reference current i ref via external resistor ri between pin 3 and ground. q14 q16 r2 r3 q17 q19 q20 r8 q21 q13 q12 r5 r6 r7 6 5 op2 i c ref v i o 78 q3 q4 q15 q2 i lim q1 cc v - 3 v be i ref q22 r13 r12 r11 r10 q11 r9 q10 i a i z z 3 i zz 5 i 7 i i e 4 3 q9 q8 q7 q6 q5 1 2 i e5 i e6 i c6 i c9 i c5 op1 s i = i in cc be v - 6 v current limiter comparator and output stage current reference parabola network full-wave rectifier i et24 op3 d1 d4 d2 d3 z1 i in AN393-35.eps figure 35 : simplified circuit diagram for tda4950 - tda8145 tv east/west correction circuits 22/32
iii.2 - description let us consider the blocks in detail : the input amplifier op1 drives the transistor q5 or q6. they offer two different signal paths, depend- ing on the sign of the input current i in . assuming that i in is negative, the feedback loop is closed via the transistor q5 and the output current i c5 is given by i c5 = i e5 ? ? b 5 1 + b 5 ? ? = - i in ? ? b 5 1 + b 5 ? ? where b 5 is the current gain of the transistor q5. b 5 can be assumed to be more than 100, so the mismatching between i c5 and i in is less than 1%. for a positive current i in the output voltage of op1 decreases : q5 is switched off the current i in is the emitter current i e13 of q6. its collector current i c6 is given by i c6 = i in ? ? b 6 1 + b 6 ? ? since the maximum input current is 40 m a, the current gain of this pnp transistor is still high enough to give a reasonable small error. this cur- rent biases the current mirror q8 and q9. a good matching between the current i c8 and i c9 must be provided. thus the current i s is given by i s = - i in ? ? b 5 1 + b 5 ? ? i in < 0 + i in ? ? b 6 1 + b 6 ? ? i in > 0 neglecting the base current of q6 and q5, i s is nearly the absolute value of i in . note that for both signal paths, the op1 has a feedback factor of 1. this means op1 must be frequency compensated for unity gain. the transistors q3 and q4 work as a normal current mirror if the current i s plus i e is smaller than the current i lim : 2 i s < i lim in this case the excess current is shunted via the pnp transistor q1. if the current i s becomes higher i s > i lim /2 the transistor q1 switches off and q2 picks up the current i s from the rectifier which exceeds the maximum value of i lim /2. using the proposed reference resistor ri bet ween pin 3 and ground (11k w ) the current i e can be described with i e = i in i in < 40 m a 40 m ai in > 40 m a the parabola network produces an output current i a which is approximately a parabola : i a = k i e 2 the parabolic behaviour i a is obtained via piecewise linear approximation. for this purpose the identical resistors r z are connected with the four emitters. the four different biasing currents i z , 3i z , 5i z , 7i z yield four different threshold voltages, so the four emitter currents of q11 are switched stepwise. a schematic illustration of the single emit- ter currents i eq11 (1...4) of q11 as a function of the current i e is given in figure 36. eq11 eq11 eq11 eq11 i (1) i (2) i (3) i (4) e eq11 i (ma) a i (ma) i (a) AN393-36.eps figure 36 : transfer characteristic of the parabola network tv east/west correction circuits 23/32
due to the exponential character of the emitter current as a function of the base emitter voltage, the output current i a is smoothed. for designing the values of r z and i z of this parab- ola network we must take a compromise between the smoothing effect and the temperature depend- ence. small values of r z and i z yield small thresh- old voltages for the 4 emitters of q11. this means a good smoothing of the edges, but a worse tem- perature dependence. large values of r z and i z yield the opposite result. practical experiences show that a value of 0.5v for the 4th emitter (r13 7i z ) for i in = 0 gives an accept- able cmpromise. due to different values of resistor r z , the tda 8145 is adapted to flat square tubes (see figure 37 for the two different shapes of the parabola). t (ms) par v (v) 0.5 2ms tda4950 tda8145 AN393-37.eps figure 37 : parabola shapes for tda4950 and tda8145 the parabolic output current i a produces a corre- sponding voltage drop across an external resistor between pin 7 and ground (18k w ). the additional constant current source i 0 shifts the d.c. voltage level to achieve an appropriate operating point of the comparator. its non-inverting input is connected with a horizontal saw-tooth voltage. for this pur- pose an external capacitor is connected with pin 8 and ground which is discharged with the internal current source i c . it will be charged with the positive flyback pulses produced in the line transformer during the flyback time. due to the linear saw-tooth voltage on pin 8 this comparator works as a pulse-width modulator. the output of this comparator controls the output stage. if the output of the comparator op2 is high, q21 and q12 are saturated. therefore, the dar- lington output transistor q19, q20 is switched off. the transistor q13 and the resistor r5 acts as a current source biasing the current mirror q14, q15. the transistor q16 is switched on. if the output of op2 becomes low, q12 and q21 are switched off. in this case the current in q14 and q15 dissappears and q16 is switched off. synchro- nously the darlington stage q19 and q20 is satu- rated. in order to achieve a fast commutation from q16 to q19/q20 an active discharging of q16 is prov ided with the aid of the transistor q17. during a normal operation range if the output cur- rent i out is positive, only the darlington stage (q19, q20) and the diode d1 are necessary to drive the external inductor. with the aid of q16 and the intrinsic substrate diode d4 the output current i out can become negative, too; so that the modulation range of the diode modulator becomes larger. the zener diode z1 serves as the voltage refer- ence. with the aid of the diodes d2 and d3, a good temperature compensation can be achieved. using an external resistor of r i = 11k w between pin 3 and ground we get an accurate and tempera- ture independent current reference to bias the in- ternal current sources. iii.3 - application a standard application diagram is given in fig- ure 38. pin 2 is biased from a linear saw-tooth voltage, the resistor r in produces the input saw-tooth current. the non-inverting input (pin 1) is connected with an adjustable voltage (keystone correction). with the aid of this trimmer, the symmetry of the parab- ola can be adjusted in order to correct a trapezoidal error in the colour picture tube. a further adjustment trimmer is responsible for the picture width and influences only the dc-level of the comparator input (pin 8). (since the discharging current sink on pin 8 is constant, the amplitude of the horizontal saw-tooth voltage (v pp ) remains constant). the thrid trimmer is in the feedback path and is responsible for the parabola correction factor. with the aid of this trimmer the distortion on the screen can be changed from pillow-distortion up to an over-correction (tun-distorsion). for some applications the keystone adjustment trimmer is not necessary (small trapezoidal error of the picture tube). in this case, a symmetric parab- ola should be produced. tv east/west correction circuits 24/32
5 6 3 7 8 1 2 4 i i b c i c i b u a t v fr rin v ref ref i cc v - 4v cc v cc v 26v 100 m f 1n4148 47nf 18k w 4.7nf pp 2v picture width 1k w 12k w 100k w keystone correction diode modulator 10mh 4.7k w 47k w east-west amplitude v t l from line transformer u 40 m a a i b AN393-38.eps figure 38 : standard application diagram of tda4950 and tda8145 this can easily be obtained by ac-coupling the input (pin 2) as seen in figure 39. 3 1 2 cin rin AN393-39.eps figure 39 : ac-coupled vertical saw-tooth voltage, no keystone (trapezoidal) correction in order to avoid any distorsion, the time constant c in r in should be at least 10 times larger than the time period (c in r in > 10 20ms). on the other hand a too large time constant yields an undesired bouncing effect in the east/west correction. the dc voltage on pin 1 is arbitrary. for the sake of simplicity, connect pin 1 with pin 3. another possible application with parasitic parab- ola suppression is given in figure 40. the input current into pin 2 is generated via the voltage drop on r m . due to the common mode rejection of the input operational amplifier, the volt- age change during the vertical scan time (saw- tooth voltage) has nearly no effect. during the flyback time, a positive pulse (> v cc ) is present on pin 1 and pin 2. with this flyback pulse the current limitation in the parabola generation circuit is acti- vated and limits the parabola amplitude. since the flyback time is relatively long, this limitation is nec- essary to suppress the parasitic parabola (see chapter i.4). tv east/west correction circuits 25/32
5 6 3 7 8 1 2 4 i i b c i c i b u a v ref ref i cc v - 4v cc v cc v ri rm rin yoke deflection unit u 40 m a a i b AN393-40.eps figure 40 : application of tda4950 and tda8145 with parasitic parabola suppression iv - tda8146 general description iv.1 - introduction 48 7 14 13 12 11110 96 32 5 ref i 1.2v 1.2v 60 m a 22v 8.2v i ref ignd c pw z gnd i ref v gl v i v out s par ps p4 v tea8146 AN393-41.eps figure 41 : block diagram the tda8146 was designed for tv and monitor sets with various types of picture tubes, where a programmable parabola is mandatory. the com- plete block diagram is shown in figure 41. the following features confer to this ic an all-pur- pose suitability : - programmable parabolic current generator - parasitic parabola suppression during vertical fly- back - output sink current up to 800ma and source cur- rent up to 100ma - vertical current sense inputs ground compatible tv east/west correction circuits 26/32
iv.2 - input amplifier and rectifier the input circuitry (figure 42) is designed for a common mode range up to 12v. the voltage drop on r1 gives on i gnd (pin 3) : v r1 = r1 i ref the operational amplifier op regulates the current through r2, thus : i r2 = (v r1 - v in ) / r2 = (r1 i ref - v in ) / r2 for v in > 0, we note the output current of the input amplifier i n : i n = i ref - i r2 = i ref - (r1 i ref - v in ) / r2 for v in < 0, we note the output current of the input amplifier i p : i p = i r2 - i ref = (r1 i ref - v in ) /r2 - i ref the rectifier is formed by q2, q3 and q4. for v in > 0, i n flows through q2 to the rectifier output, thus i r = i n . for v in < 0, i p flows through q3 from v s into the output of the input amplifier. q4 reflects the i p current, thus the rectifier output currrent will be i r = i pm = i p . if the sign convention of i r is considered, we have : i r = ? ? ? ( r1 i ref - v in ) r - i ref ? ? ? = ? ? ? i ref ? ? r1 r2 - 1 ? ? + v in r2 ? ? ? in our case, r1 = r2 = 10k w and i ref = 120 m a thus, i r = ? ? ? v in r2 ? ? ? if v in is a symmetrical saw-tooth with gnd as the average value and 1.6 v peak-to-peak , the rectified peak current will be : i rp = 0.8 10 10 - 3 = 80 m a iv.3 - vertical clamping to avoid the parasitic parabola during the vertical flyback time a vertical clamp circuit was used. the vertical clamping principle is presented in fig- ure 43. the rectified sawtooth current i r flows through d2 to the output. when v goes over v s , q1 switches off and q2 on. i ref flows now through d1 to the output and i r through q2 to the ground. i rc = i ref is now the clamped value of the output current. iv.4 - reference and starting circuit figure 44 presents the complete voltage and cur- rent reference circuitry. the reference current is i ref = 8.2v 100 k w = 82 m a to guarantee the start of the device, it is necessary to choose the value of the resistor r5 in order to have a minimum current of 56 m a. 32 i ref ignd v i v s i ref q4 q2 q3 q1 op i p i n i r i s s v i pm i n i p v in r 2 r 1 input amplifier rectifier t t 0 0 i r v in v ip v ir i rp AN393-42.eps figure 42 : input and rectifier principle diagram tv east/west correction circuits 27/32
i ref q2 op i r v t t 0 0 i v q1 v i v vertical flyback rectified sawtooth current rectified and clamped sawtooth current rc v s d1 d2 inv rc i ref v v s AN393-43.eps figure 43 : vertical clamping principle diagram i ref op d1 d2 t1 5 w r5 100k current reference d3 AN393-44.eps figure 44 : reference and starting circuit iv.5 - parabola generator figure 45 presents the simplified circuit diagram of the parabola generator. the parabolic behaviour of the parabola output current is obtained via piecewise linear approxima- tion. two external pins permit an external adjustment of the parabola shape (these pins can be connected to ground or to resistors). the parabolic output current on pin 12 produces a corresponding voltage drop across an external re- sistor between pin 12 and ground. as it can be seen in figure 46 the parabola can be corrected in the following limits : v c5 /v c = k5 = 1.07 with pin 5 to gnd v c4 /v c = k4 = 1.17 with pins 4 and 5 to gnd an application specific correction can be thus ob- tained for various picture tube types. iv.6 - pulse-width modulator and out- put the simplified diagram of the pulse-width modula- tor and output is presented in figure 47. the non-inverting input of the comparator (pin 11) is connected to a horizontal saw-tooth voltage. an external capacitor connected on pin 11 is charged during the flyback time and then discharged by the internal current source generating the saw-tooth voltage. due to the linear saw-tooth voltage on pin 11, the comparator works as a pulse-width modulator. the output of this comparator controls the output stage. if the output of the comparator is high, q67 and q64 are saturated. the darlington output configu- ration q65/q66 is switched off. q62 acts together with r53 as a current source, biasing the current mirror q58/q59. the transistor q60 is switched on. if the output of the comparator becomes low, q64 and q67 are switched off. the current thr ough d58/q59 disappears and q60 is switched off. syn- chronously the darlington stage q65/q66 is satu- rated. in order to achieve a fast commutation, an active discharging of the q60 base charge is pro- vided with the aid of q63. tv east/west correction circuits 28/32
i i e5 i e4 i i i e3 e2 e1 12 1k w 1k w w 3k w 3k w 3k 1k w 1k w w 2k w 2k iii i 1234 5 i gl 14 13 cc p4 p5 s4 s5 v cc v * * 720mv 560mv 400mv 240mv 80mv constant current sources parabolic output current par rectified input current 0 note : * it is possible to replace the switches s4 and s5 by this conf iguration in order to have a cont inuous shape variations. AN393-45.eps figure 45 : parabola generation 9.6v 9v 8v 7v -0.8v -0.6v -0.3v 0 +0.8v during flyback v se vv v v v v df par par0 a c v v c4 c5 AN393-46.eps figure 46 : parabola correction tv east/west correction circuits 29/32
d58 q62 q59 q60 8 7 v out s q64 q63 r53 r52 q65 q66 q67 v ref 12 11 c par AN393-47.eps figure 47 : pulse-width modulator and output iv.7 - application an application diagram is presented in figure 48. the internal zener configuration on pin 9 can be useful in certain application. 1 2 3 4 5 6 7 t d a 8 1 4 6 8 9 10 11 12 13 14 p4 p5 100nf 3.3nf v cc 10k w 100k w 4.7k w 47k w 10k w 3.3m w 330k w 15mh to diode modulator +27v 1nf 220 m f vertical deflection vertical flyback vertical yoke rs v gl v cc horizontal flyback 2.2k w * 3.3k w * * note : depending on flyback voltage AN393-48.eps figure 48 : application diagram tv east/west correction circuits 30/32
v - tda8147 general description v.1 - introduction the tda8147 was designed as an interface ic between the digital circuitry and the diode modulator in digital chassis. the complete block diagram is shown in figure 49. v.2 - input amplifier the pulse-width modulator of the tda 8147 is work- ing with input voltages from 1v to 23v. to have the same range for the parabola voltage an input am- plifier is necessary. digital tv sets deliver an ana- log parabola or a pwm-signal with small amplitude (2v to 3v). an additional signal ground (sgnd pin) separates the digital ground from the deflection circuit ground. the internal feedback loop of the amplifier gives a voltage gain a v = 17.5 5 + 1 = 4.5 (see figure 50) v.3 - voltage reference and starting circuit the voltage reference and starting circuit have the same configuration as for the tda8146 (see para- graph iv.4). v.4 - pwm modulator and output the pwm modulator (figure 51) has the same configuration as for the tda8146. so see para- graph iv.6 for explanation. 7 pw modulated parabola 8 4 2 63 1 5 9..16 10mh to diode modulator 100nf 39k w 17.5k w 5k w 100k w 47k w +24v 1nf r1 r2 60 m a h out h gnd c sgnd in amp par v s 0.2 - 5v av = 4.5 pinning for 8 + 8 dil package tda8147 AN393-49.eps figure 49 : tda8147 block diagram v.5 - application a standard application diagram is given in fig- ure 51. since all the adjustment of the parabola are made by the digital processor, only the feedback loop of the pwm modulator must be carefully designed. the tda8147 is well-suited for new tv concepts with 32khz line frequency. 7 8 6 17.5k 5k w w sgnd in amp AN393-50.eps figure 50 : input amplifier tv east/west correction circuits 31/32
7 pw modulated parabola 8 4 2 63 1 5 9..16 10mh to diode modulator 100nf 39k w 17.5k w 5k w 100k w 47k w +24v 1nf 60 m a h out h gnd c sgnd in amp par v s 0.2 - 5v av = 4.5 pinning for 8 + 8 dil package tda8147 4.7nf 50v pp w 1k w 2.2k w 6.8k AN393-51.eps figure 51 : application diagram information furnished is believed to be accurate and reliable. however, sgs-thomson microelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. no licence is granted by implication or otherwise under any patent or patent rights of sgs-thomson microelectroni cs. specifications mentioned in this publication are subject to change without notice. this publication supersedes and replaces all information previously supplied. sgs-thomson microelectronics products are not authorized for use as critical components in lif e support devices or systems without express written approval of sgs-thomson microelectronics. ? 1994 sgs-thomson microelectronics - all rights reserved purchase of i 2 c components of sgs-thomson microelectronics, conveys a license under the philips i 2 c patent. rights to use these components in a i 2 c system, is granted provided that the system conforms to the i 2 c standard specifications as defined by philips. sgs-thomson microelectronics group of companies australia - brazil - china - france - germany - hong kong - i taly - japan - korea - malaysia - malta - morocco the netherlands - singapore - spain - sweden - switzerland - taiwan - thailand - united kingdom - u.s.a. tv east/west correction circuits 32/32

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