IT8320695A1 - HORIZONTAL DEFLECTION CIRCUIT, VARIABLE TYPE, ABLE TO GUARANTEE EAST-WEST CORRECTION OF BEARING DISTORTION - Google Patents

Description

DESCRIPTION OF THE INVENTION

The present invention relates to a deflection circuit in which the amplitude of the deflection current can? be varied

over a relatively wide range, without varying the amplitude of the high voltage or the retraction time of the deflection. Should it be noted that modulation of the deflection current amplitude is desirable for certain specific purposes, i.e., for example, for east-west correction of pincushion distortion, for image width adjustment or for similar applications?

The general disadvantages of the known circuits for EAST_WEST correction are represented

from the fact that they consume a quantity?

of relatively high power, impose limitations on the design of certain linearity correction circuits, or produce an undesirable nodulation of the retrace time? Also, some EAST-WEST correction circuits require additional components, connected in series in the path followed by the deflection current. This series connection complicates the design of linearity correction circuits. which require an "S" shaped capacitor connected to circuit ground for proper circuit operation?

The complexes proposed by the invention, which will be described hereinafter, allow these disadvantages to be avoided in general. In accordance with an aspect of the invention, a controllable switch, operated at the deflection frequency, is connected to a deflection winding so as to generate a sweep current in the winding during a one-cycle trace interval. of deflection. A capacity? deflection retrace forms a deflection retrace resonant circuit with the deflection winding, during a retrace interval. A power supply inductance is connected to a second capacitance. and to the controllable switch, to form a second resonant circuit within the retrace interval, for generating a pulse voltage. siva which excites a load circuit. During the retrace interval, the two resonant circuits are substantially decoupled from each other at the retrace frequency of the deflection and at frequencies of value pi? high.

This decoupling avoids an undesirable interaction of the two circuits.

In a practical embodiment of the invention, the decoupling of the two resonant circuits is obtained by means of a relatively high value inductive impedance, interposed between the two resonant circuits, within the retrace interval. During the trace interval, the controllable switch derives current from the impedance and moves that current away from the deflection winding and supply inductance.

In accordance with another aspect of the invention, the EAST-WEST correction of pincushion distortion is also achieved by coupling the impedance to a modulating current source which is varied at the vertical frequency. During the retrace interval, energy is fed to the resonant retrace circuit in a manner that is controlled by the amount of time. of nodulation current which is supplied by the nodulation source. By varying the nodulation current at the vertical frequency, in a parabolic node, the energy fed to the resonant retrace circuit is also varied at the vertical frequency. The peak current circulating in the deflection winding at the start of the trace also varies at the vertical frequency, in a parabolic node, in order to obtain an EAST-WEST correction of the pincushion distortion.

The present invention will result? pi? evident from the analysis of the following detailed description, which must be considered in conjunction with the accompanying drawings, in which;

Figure 1 illustrates a deflection circuit with control of the amplitude of the scanning current in accordance with the characteristic principles of the present invention;

Figures 2-4, considered constituted by Figures 2a-2_2, 3a-3e and 4a-4_e, respectively, illustrate the waveforms of quantities associated with the operation of the circuit represented in Figure 1;

Figure 5 illustrates a different practical embodiment of a deflection circuit with control of the amplitude of the scanning current in accordance with the characteristic principles of the present invention;

Figures 6-8, considered constituted by Figures 6_a-6_e, 7a-7e and 8a ~ 8_ef respectively, illustrate waveforms of quantities associated with the operation of the circuit represented in Figure 5;

Figure 9 illustrates a deflection circuit with an EAST-WEST correction of pincushion distortion, in accordance with the characteristic principles of the present invention; And

Figure 10, considered constituted by Figures 10a-10g, illustrates the waveforms of the quantities which are associated with the operation of the circuit represented in Figure 9;

As shown in Figure 1, a source of stabilized direct voltage B + is connected between a terminal 21 and the circuit ground, said direct voltage being fed, through a resistor RI, to a first terminal of a winding wl of a transformer horizontal output T, said voltage being filtered by means of a capacitor C1 connected between the output of the resistor Ri and the circuit ground. The other terminal of the winding w1 is connected to a junction terminal 22.

A horizontal output transistor 01 has its own collector-emitter path connected between terminal 22 and the circuit ground. In parallel to the transistor Q1 e1 connected a complex series formed by two rectifying diodes Di and D2. Between the anode electrode and the cathode electrode of the diode Di is connected an assembly comprising a horizontal deflection winding L ^ and a trace capacitor Cs or 3-shaped shaping capacitor. A deflection retrace capacitor is connected across the assembly. series formed by the horizontal deflection winding L ^ and the trace capacitor Cs. A second trace capacitor is employed to form a resonant circuit 50 which resonates with the v / 1 winding of transformer T. The capacitor is connected between terminal 22 and circuit ground.

Connected between the lower terminal of the trace capacitor at C5 and the circuit ground is a series assembly comprising a block inductor L1 having a relatively large inductance and a controllable DC voltage source V *.

Will come now analyzed the operation of the power supply and of the horizontal deflection circuit schematized in Figure 1 when the voltage source, of the controllable type 24 has a certain positive direct voltage V, with respect to the circuit net, this voltage having a value lower than the amplitude of the voltage B +. For the description will come? reference is made to the waveforms shown in figures 3a-3e}.

during the initial portion of the horizontal trace interval, the diode Pi is in the conduction state, so as to allow the application of the trace voltage developed across the trace capacitor Cg across the horizontal deflection winding L. ? In accordance with As shown in FIG. 3e, when the trace voltage is applied across the horizontal deflection winding L-j, the horizontal sweep current i ^ is represented by a sawtooth waveform of polarity. negative, but tending towards positive values.

During the initial portions of the trace, the diode D2 is also in the conduction state, in such a node as to bring the voltage at the terminal 22 to a value corresponding to the reference voltage substantially equal to the voltage of the circuit ground. The stabilized voltage B + is then applied to the ends of the winding v / 1 of the horizontal output transformer T, in such a way as to produce the sawtooth current, with a positive trend i ^? as shown in Figure 3b. When the diode 1) 2 is in the conduction state, the tensile LO developed by the voltage source 24, of the controllable type, is applied to the ends of the block inductor L1, in order to develop the sawtooth current i ^, of limited amplitude, illustrated in Figure 3c.

To allow the circulation of polarity currents? positive i and the assembly 23 comprising the oscillator and the horizontal driver bias, in a direct direction, the horizontal output transistor Q1 at a certain instant, before the center of the horizontal tracing interval. During the last portions of the in? In the horizontal trace range, the positive horizontal scan current i flows from the right terminal of the horizontal deflection winding I ^ j? through the horizontal output transistor Q1, through the diode D2, to the lower terminal of the trace capacitor C8. The diode D1 becomes reverse biased when the horizontal output transistor Q1 conducts a collector current, in the forward direction. The positive current iT circulating in the winding wl of the horizontal output transformer T circulates towards ground, through the horizontal output transistor Ql.

At the beginning of the horizontal retrace interval, the assembly 23 consisting of the horizontal oscillator and the horizontal pilot applies a reverse bias signal to the base electrode of the horizontal output transistor Q1, at such node. determine the interdiction of the immediate collector conduction ^ upstream of the moment considered. When the horizontal output transistor Q1 is in the non-conducting state, the horizontal deflection winding forms a resonant retrace circuit 25 with the retrace capacitor of the deflection C ^, a ^? ac? P? to develop a retrace impulse voltage V ^?

Similarly, as a function of the non-conduction changeover of the horizontal output transistor Q1, the winding w1 of the horizontal output transformer T forms the second resonant circuit 30 with the second retrace capacitor C1 .H value of the condenser. The retrace sator with respect to the value of the effective inductance presented by the winding v / 1 is such that the resonant frequency of the resonant circuit 30 is close to corresponding to the resonant frequency of the retrace of the deflection?

The pulse voltage developed across the second retrace capacitor is represented by the voltage VI illustrated in FIG. 3a. A similar inpulsive voltage, of alternating character, is developed across the winding wl of the horizontal output transformer T. This pulse voltage is coupled, as a transformer, to the other windings of the transformer illustrated, collectively, in Figure 1, as a single winding v / 2. The transformed impulse voltages, after an appropriate rectification and filtering action, allow the excitation of various load circuits of the television receiver, not shown in figure 1. The amplitude of the impulse voltage Vi and of the impulse voltage developed at the ends of the winding wl, is correlated to the amplitude of the voltage B +. Therefore, by stabilizing the B + voltage it is also possible to stabilize these pulse voltages

amplitude of the horizontal scan current i and, therefore, the amplitude of the retrace pulse voltage represents a function of the average value of the trace voltage developed across the trace capacitor Cs? Since it is not possible to develop any voltage having a direct current component at the ends of an inductance, the average value

of the trace voltage assumes a value equal to the difference between the direct voltage B + and

the direct voltage V? by varying the amplitude of the controllable developed voltage of the source 24, the average trace voltage and the peak scanning current can be varied simultaneously. For example, when the modulation voltage V is equal to the voltage B +, the current ij flowing in the inductor II is substantially equal to zero, as shown in Figure 2_c. Consequently,

from winding vi of the horizontal output transformer T will not circulate? no current in the retrace resonant circuit of the deflection 25. Is it not possible to transfer energy from the power supply supplying the voltage B + for maintaining the current in the deflection winding? ? The deflection current i is therefore equal to zero, in accordance with what is illustrated in Figure 2je.

The waveforms shown in figures 3ja - 3e illustrate the case in which the nodulation voltage VQ is regulated in such a way as to present a certain amplitude lower than the amplitude of the voltage B +. The nodulation current i ^ has been shown in Figure 3c. During retrace, the current i? ^ Circulates in the inductor L1, through the retrace capacitor of the deflection C ^? The resulting extra charge on the capacitor RD is transferred, during retrace, into the horizontal deflection winding L, so as to replenish the resistive losses encountered during each deflection cycle. Since? ' the nodulation voltage VQ has a reduced amplitude with respect to its own amplitude referred to the case of the wave forms of figures 2ja_2e., the average trace voltage, equal to the difference between the voltage B + and the nodulation voltage Vm, will present ? a greater breadth. The amplitude of the deflection current is increased from zero, as shown in Figure 2e, to a certain value other than zero, as indicated in Figure 5_e. The retrace impulse voltage of the deflection V ^, whose value is? equal to the voltage VI decreased by the voltage V2, it is also increased until reaching a? non-zero amplitude?

A further decrease in the modulation voltage Vm up to a value equal to zero, in which the source 24 which supplies the modulation voltage assumes the character of a functional equivalent of a short circuit, results in the production of quantities whose waveforms? have been shown in figures 4a - 4e. In this situation, the deflection current i has reached its maximum amplitude level. Since ?? the amplitude of the deflection current i is greater, in figure 4e, compared to what is reported in figure 3e, also the resistive losses that are found in the deflection winding I ^ j increase? Therefore, the average value of the modulation current i ^ is also increased, as shown in Figure 4c. Since? ' the current i ^ during the retrace, is derived from the current ij circulating in the winding wl of the horizontal output transformer T, the positive peak value of the current of the transformer winding is increased as a function of an increase in the average value of the current ij ^?

The inductor L1 is circuitally connected in the resonant retrace circuit of the deflection 25 and in the resonant retrace circuit 30, substantially during the entire interval d? retrace the deflection. Consequently, the circuit impedance coupled to the resonance circuit of the retrace of the deflection 25 does not undergo variations and will not occur. no significant modulation of the retrace time of the deflection. It must be emphasized that the ten? sion VI developed at the terminal 22 of the winding 1 of the return transformer, remains unchanged as the voltage d? nodulation Vn. Therefore the final acceleration voltage (ultor) and other direct voltages derived by rectifying and filtering the voltages developed at the ends of the secondary windings of the horizontal output transformer represented by the winding w2, are not influenced by the nodulation of the horizontal scanning current i?

Using two retrace capacitors represented by the first retrace capacitor

for the resonant circuit for the retrace of the deflection indicated at 25 and by the second retrace capacitor C ^ it, for the resonant circuit 30 of the transformer, the energy flow during the retrace in the resonant circuit for the retrace of the deflection 25, can? ' be controlled independently, without altering the amplitude of the voltage pulse T1 developed by the resonant retrace circuit of the transformer 30. impedance? i relatively high value of the blocking inductor Li connected in the path of the circulating current dr. 11 the winding wl of the horizontal output transformer T to the resonant retrace circuit of the deflection 25, the two resonant circuits 25 and 30 are substantially decoupled at deflection retrace frequencies or higher frequencies? Therefore, any modulation of the pulse voltage VI due to the loading variations by the consequently energized load circuits does not result in an undesirable modulation of the retrace pulse voltage of the deflection V.

During retracement, the effect of the condenser Cs can be neglected due to the fact that the capacitance is it is much higher than that of the CR capacitor. Thus, the resonant circuit 25 includes the parallel connection of the deflection winding L2 and the deflection retrace capacitor CR? This cir? cuito has a high impedance at its resonant frequency and a low impedance at other frequencies. Since? ' the circuit 25 is driven by the high impedance inductor Pi, the circuit 25 operates as a filter? The impedance of circuit 25 is high only at the retrace frequency of the deflection (44 kllz). All the voltages generated by the horizontal output transformer T with substantial frequencies? Differently from the deflection retrace frequency, will appear across the inductor L1 due to the impedance of inductor L1 which is much greater than the impedance of the deflection retrace resonant circuit 25 at these different frequencies.

By connecting the inductor L1 between the ground cir? and the lower terminal of the deflection retrace capacitor at terminal 27, the deflection retrace resonance circuit 25 may fluctuate above ground potential during the retrace interval. Thus, during retrace, the voltage at the upper plate of the retrace capacitor C1, on terminal 22, is equal to the sum of the pulse retrace voltage of the deflection and the voltage V2 developed between terminal 27 and ground. This fluctuating complex results in the aforementioned decoupling of the two resonant circuits 25 and 30, during retrace at frequencies equal to and above the retrace frequency of the deflection.

5 illustrates another embodiment of the invention in which the track capacitor C is connected to the circuit ground, as occurs for the deflection retrace resonant circuit 25. The circuit elements shown in FIGS. 1 and 5 that have been identified by the same reference numbers, operate in a similar way or represent quantities? similar. In the power supply and in the modulated deflection circuit of FIG. 5, the inductor Li is connected to the junction point between the diodes Li and L2, at the terminal at 27. The retrace capacitor of the transformer, ancient? be connected between terminal 22 and circuit ground? And? now connected, in FIG. 5, between the terminal 22 and the left terminal of the inductor Li, at the terminal 27. In this arrangement, the resonant circuit 30 of the transformer, formed by the winding w1 and the retrace capacitor of the transformer, is it kept floating above the mass potential during its resonant retrace interval?

The complex schematized in Figure 5 has the advantage deriving from the use of a trace capacitor Cg connected to the circuit ground. A complex of this type is required by certain linearity correction circuits, of the type described, for example, in U.S. Pat. filed on 30 - March 1972 to none P.E. Ilaferl, entitled "LIirdARITY CO-tECTXD OIJIVsL DZPLSCLIOIi BLIND ??, corresponding to patent application ?? published 2098424? *., Published on November 17, 1982. The circuits represented in Figures 1 and 5 have the common characteristic that the inductor UL operates as a high value impedance towards the high frequency currents circulating between the two resonant circuits 25 and 30.

The amplitude nodulation of the horizontal scanning current i is obtained, in the circuit shown in Figure 5, in a node similar to that previously described with reference to Figure 1. Figures 6a - 6e illustrate

the situation which occurs when the modulation voltage of Figure 5 has a value equal to zero. Consequently, the current i ^ of Figure 5c is equal to zero, as occurs for the voltage V2 between the terminal 27 and the circuit ground. With zero current in the inductor L1, the circuit path with respect to the circuit ground, through the inductor L1 and the source 24 represents, in effect, an open circuit. the pulse voltage of the deflection retrace has an amplitude determined only by the stabilized voltage B +; similarly, the deflection current i has an amplitude determined only by the voltage B +.

Figures 7a-7e illustrate the situation that occurs when the modulation voltage Vm is increased to a certain level above zero. The current i ^, during the trace, circulates

horizontal, through the diode Di and also through the horizontal output transistor Q1 when 10 itself conducts a forward collector current? During the horizontal retrace, the inductor Di is serially connected with the resonant retrace circuit of the transformer 30. The impulse voltage V2 is fed to the cathode of the diode D3 through a filtering capacitor, of considerable capacitive value, indicated by the reference Cl, in so as to interrupt the conduction through the diode, during the retrace. The retrace voltage of the deflection V ^ is represented by the sum of the voltage V2 and the pulsed retrace voltage VI * developed across the retrace capacitor of the transformer. Is the mean value of the voltage V2 equal to the amplitude of the modulation voltage Vm? Therefore, the mean value of the retrace impulse voltage and the amplitude of the scanning current i increase with the increase of the nodulation voltage Vrn? So long as? the voltage B + and? stabilized, the voltage Vi? it remains unchanged as an average value, and as well as amplitude.

A further increase in current i due to a further increase in the modulation voltage produces the quantities whose waveforms have been shown in FIGS. 8a - 8e? The amplitude of the pulse voltage V2 undergoes an increase and, consequently, there is also an increase in the amplitudes of the retrace pulse voltage of the deflection and of the deflection current i, as shown in Figures 8a and 8e? It must be noted that the current iT circulating in the winding wl of the horizontal output transformer? remains unchanged as the modulation voltage Vm varies since the current i-j ^, during the retrace, circulates towards the resonant retrace circuit of the deflection 25, through the retrace capacitor C ^, instead of through the winding wl?

Comparing the similarities? and the differences in the operation of the circuits shown in FIGS. 1 and 5, it should be noted that the scanning current of the circuit shown in FIG. 1 can be varied from a value of approximately zero to a certain value. By the voltage B + j the scanning current i of the circuit represented in Figure 5 can be varied from the value determined by the voltage B + to a value determined by the maximum amplitude that is allowed for the modulation voltage Vm? A limiting factor as regards the maximum amplitude of the voltage Vm is represented by the maximum voltage stress that is allowed between the collector electrode and the emitter electrode of the horizontal output transistor Q1. The pulse voltage applied to the collector of the horizontal output transistor Q1 is constant in the circuit shown in Figure 1, while it varies in the circuit shown in Figure 5. The current iT varies in the circuit of Figure 1 but remains constant in the circuit of Figure 5. The circuits of FIG. 1 and FIG. 5? if the modulation voltage is varied, as amplitude, to the vertical frequency, in a parabolic way, the amplitude of the horizontal scanning current i is modulated in a similar way, so as to provide an EAST-WEST correction of the pincushion distortion .

Figure 9 illustrates a modulator and a modulated deflection circuit embodying the subject invention, in which the primary winding of the horizontal output transformer is connected to a switching-type power supply, while the horizontal deflection circuit is connected to the secondary winding of the transformer. The elements shown in Figures 1, 5 and 9, which have been identified by the same reference numerals, operate in an analogous manner or represent quantities. similar.

compliance now shown in FIG. 9? a winding w2 * of a horizontal output transformer T e * connected to a power supply of the switching type, indicated by reference 50 and constituted, for example, by the power supply of a single conversion system (3IC0S-single conversion) described in US Patent Application No. 535.610, filed December 22, 1981 in the name of P. E. Haferl, and filed REGULATED DEFLECTION CIRCUIT, corresponding to published UK patent application 2094GS5A, published September 8, 1982.

The assembly represented in Figure 9, in a manner similar to that previously defined with reference to the assembly illustrated in Figure 5? includes an S-shaped capacitor Cs, connected to circuit ground, in order to allow the use of a linearity circuit, not shown in FIG. In Figure 9, a modulation circuit 26 provides for the EAST_WEST correction of the pincushion distortion while maintaining, at the same time, the amplitude of the pulse voltage VT across the winding wl * stabilized by the switching-type power supply. The deflection resonant circuit 25 and the transformer resonant circuit, indicated at 30, are individually tuned to the deflection retrace frequency. When a switching power supply, of the SICOS type previously defined, is used, the effective inductance presented by the winding wl 'is relatively high and, as such, the capacit? of retrace

CRT and CRD1 * CRD2 * associated with the two resonance circuits, are selected in such a way as to present, approximately? the same value.

During the horizontal trace interval, the retrace capacitor of the transformer and the DC blocking capacitor C1 are connected to the circuit ground through the diode D2 in the conducting state or through the diode D1 in the conducting state and the horizontal output transistor Q1, also in the conduction state, during the first half? of the horizontal retrace interval, the resonant circuit 30 of the transformer and the resonant circuit 25 of the deflection retrace produce, individually, an impulsive voltage or by means of the transfer of the inductively stored energy in substitution of the stored capacitive energy, this energy being stored in the respective retrace capacitor CRT 0 CPD1 RD2 * This energy is subsequently returned to the respective inductance wl 'o during the second half? retrace interval?

Is the impulse voltage V ^ sampled by means of a tap present on the winding w2? of the horizontal output transformer T and applied to the switched type power supply 50, in such a way as to stabilize the amplitude of the impulse voltage during the variations of the load and of the mains supply voltage. Is the energy transferred from the switched mode power supply 50, during retracement, through the windings w2? and wl ', to the resonant circuit 30 of the transformer and to other load circuits driven by the retrace, coupled to the other secondary windings w3'-w5'.

By way of example, the resistive losses introduced by the horizontal deflection winding L-j are replenished at each horizontal retrace interval through the diode D2, by the energy transferred to the resonant circuit 30 of the transformer. As a further example, the stabilized pulse voltage produced in the winding w1 * of the horizontal output transformer T is increased by the high-voltage winding w5 *, in order to excite the high-voltage circuit 31 which provides the final acceleration voltage, in order to precisely produce the final acceleration voltage, of the established type, at the respective terminal U for the final acceleration voltage (ultor).

Now assume that a current i2 having a given amplitude flows through the winding of a transformer T2 of the modulation circuit 26. During the horizontal trace interval, the current i2 flows from the circuit ground through the winding w ^, and a diode D4, at terminal 27 which is at ground potential due to the conduction of diode Di and diode D2 or of the horizontal output transistor Q1 * During the horizontal retrace interval, the transistor Q1 is in the state of interdiction. If the current ?? is greater than the current flowing through the diode D2, this diode D2 is also in the non-conducting state. The current i2 now flows in the resonant circuit 30 of the transformer and, from this circuit, passes into the deflection retrace circuit 25, thereby replenishing the losses that have occurred in the deflection retrace resonant circuit. The voltage difference between the retrace pulse voltage of the deflection Vpjj and the sum of the stabilized pulse voltage of the transformer and the voltage across the capacitor C1 will be highlighted. across the diode 12, in the form of an impulse voltage V2.

During the retrace, in the interval to-tl or to'-tl * represented in Figures 10a? 10g, a decrease of the current i2 occurs. If the inductance presented by the winding of the transformer 12 is sufficiently high, the current i2 does not decrease to a level of zero at the end of the horizontal retrace interval. Thus, the winding is coupled through the resonant circuit of transformer 30 to the deflection retrace circuit 25 substantially during the entire horizontal retrace interval. Will the variations 3i encounter in the amplitude of the current i2 produce no significant nodulation of the retrace time of the retrace pulse voltage of the deflection Vgp?

Since two separate resonant circuits 25 and 50 come into play, in the production of the two impulse voltages and V ^, the wave form of the impulse voltage V ^ may tend to vary with the loading of the current of the electron beams on the final acceleration terminal U or with the variations of the load on the winding w4 ', without producing a simultaneous variation in the waveform of the retrace impulse voltage of the deflection V ^? Does the relatively high value inductance of the transformer T2 winding act as a filter to prevent such simultaneous modulation or distortion of the retrace pulse voltage? Due to this fact, the horizontal synchronization pulse 44, used for the timing of the horizontal pilot-oscillator 25? it can be advantageously derived from the capacitive voltage divider comprising the elements instead of the elements. from a winding of the horizontal output transformer T.

Helle figures lOa? the envelope of the waveforms indicates the variations of the recurrent waveform at the vertical frequency, produced by the nodulator circuit 26, required to correct the EAST-WEST pincushion distortion of the frame.

The modulation circuit 26 generates a variable current i2 to vary the amplitude of the retrace pulse current of the deflection and to simultaneously vary the amplitude of the horizontal scanning current i? A connecting transistor Q2, operating in a back converter mode with the rectifier D4? controls the amplitude of the current i2. As illustrated in Figure 10a by means of the collector voltage V3 of the transistor Q2, the transistor Q2 is in the conduction state before the beginning of the horizontal retrace interval, before the instant tO or tO *, the voltage V3 is * equal to zero before the instant tO, while the current circulating in the winding w of the transformer T2 is * close to its maximum value, as illustrated in figure 10b.

At the instant tO, the voltage 81 across the winding \ v3 * of the transformer d? horizontal output T is inverted as polarity? and causes switching to the interdiction state of the diode D5. The current circulating in the winding rapidly decreases to zero in the vicinity of the winding. of the instant tO, as illustrated in Figure 10b. A reverse bias voltage 46 produced during retrace by the negative-going connutation waveform present at the output of a voltage comparator UIA is applied to the base of the switching transistor Q2. It must be emphasized that the current il in the winding wa of the transformer T2 and in the collector of the switching transistor Q2 is interrupted due to the reverse bias of the diode D5 due to the inversion of the polarity. of the voltage across the winding v / 3 * of the horizontal transformer T instead? Due to any reverse bias applied to the base of the switching transistor Q2, therefore, the time delay due to accumulation in switching to the non-conducting state of the connecting transistor Q2 is negligible and does not represent a factor in the inhibition. of the current the.

To maintain continuity? of the flux in the core of the transformer T2, in the vicinity? of the instant tO, G? verifies a rapid increase of the current? 2, as illustrated in Figure 10c. This current, during the horizontal retrace, circulates from the winding through the diode D4, to the retrace capacitor of the transformer * The voltage V2, whose course is? been represented in Figure 10d, and therefore represented by an impulse voltage developed within the retrace interval, this voltage being fed to the winding of the transformer T2. The application of this impulse voltage to the winding causes the decrease of the current i2 during the horizontal retrace. As illustrated in FIG. 10c, the current i2 does not decrease to zero before the end of the horizontal retrace. 3 if the current i2 decreases to a value equal to zero, significantly before the moment considered, the inductance w.D would be disconnected from the two resonant circuits 25 and 30, during a substantial portion of the horizontal track and an unacceptable modulation of the track time.

Should it be noted that the voltage V2 begins to increase just after the instant tO while it begins to decrease until the value of the ground reference voltage is reached just before the instant tl? This behavior occurs due to the time delay in switching to the off state of the diode 12, at the instant t0 when a reverse bias voltage is applied to the diode, and due to the conduction of the diode D2 just before the instant tl, in such a way as to determine the transfer of a certain quantity? of energy from the resonant circuit 30 of the transformer to the resonant circuit of the deflection retrace 25?

at the instant tl, corresponding to the beginning of the next horizontal trace interval, the switching transistor Q2 is in the non-conducting state. ? voltage V3 increases until the level of the trace voltage developed across the winding w3 'of the horizontal output transformer is reached. The termination of the winding w2, marked by the transfer point of the transformer T2, is connected to the terminal 27 by virtue of the latter. of the conduction of the diode 14. The terminal 27 is at ground potential due to the conduction of the diode 12 just before the instant tl. The current i2 then circulates with a substantially constant amplitude, as illustrated in Figure 10c, after the start of conduction of the diode D2 until the switching transistor Q2 is switched to the conduction state at a certain time within the time interval t2_t3.

The instant t2 corresponds to the center of the vertical scan where a large horizontal deflection current is required to compensate for the EAST-WEST pincushion distortion. The instant t3 corresponds to the upper or lower part of the horizontal sweep where a lower amplitude horizontal deflection current is required.

When the switching transistor Q2 is switched to the conducting state, the positive trace voltage developed across the winding V3 'of the horizontal output transformer is applied across the winding Y7 of the transformer T2. This voltage is coupled, by means of the transformer action, to the winding in such a way that the terminal of the winding marked by the reference dot, can have a polarity. negative and the commutation of diode L4 to the interdiction state may occur. The current i2, circulating in the winding drops to a level equal to zero. The energy stored in the transformer? 2 induces a voltage in the winding w? to produce the rapid increase of the current il, as illustrated in Figure 10b, starting at a certain instant within the interval t2-t3.

From the instant in which the switching transistor Q2 is switched to the conduction state until the end of the horizontal trace interval at the instant tO *, the energy is still stored in the transformer T2 due to a current of increasing value the circulating in the winding V7 &? as shown in Figure 10b. Is this energy transferred? through the winding in the resonant circuit 30 of the transformer and in the resonant retrace circuit of the deflection 25? during the retrace interval tO? -tl *.

In order to provide for a correction of the EAST-WEST pincushion distortion, the switching transistor Q2 of the modulation circuit 26 is impulsively modulated in duration at a vertical frequency, in a parabolic node, by means of the pulse duration control circuit 40 shown in figure 9 * The tooth tension of 3ega 41? recurring to the vertical frequency? developed at the ends of the vertical deflection winding L ^? is integrated? in such a way as to obtain a parabolic signal, recurring to the vertical frequency, indicated at 42, at the ends of the integrating capacitor C3. This parabolic signal is inverted and amplified by means of a transistor Q3. Part of the sawtooth voltage, occurring at the vertical frequency, is applied to the emitter of the transistor Q3, through the trapezoidal voltage control resistor RI, in order to compensate for a slight inclination of the inverted parabolic signal 43.

The amplitude of the inverted parabolic wave symmetrical signal 43? developed in correspondence with the collector of the transistor 03, it is regulated by means of a resistor R4, said signal being applied, through the direct current block capacitor C4 to the inversion input terminal of the voltage comparator U1A. Is the DC level present at this input terminal? it can be slightly shifted from the direct current level present at the non-inversion input terminal by means of the width control resistor R6. Is a voltage comparator UXB controlled by horizontal retrace pulses 44? in such a way as to produce a sawtooth signal 45? recurring to the horizontal frequency, across a capacitor C5. By comparing this saw-tooth signal, recurring to the horizontal frequency, with the parabolic signal, recurring to the vertical frequency, applied to the non-inversion input terminal of the comparator U1A, the comparator U1A produces, at its output, the required signal of switching 46, modulated as a pulse width, this signal being fed to the base of the switching transistor Q2.

The increase in the amplitude of the parabolic signal 43 due to the adjustment of the amplitude control resistor R4 results in an interval t2-t3 pi? ample, with reference to figures 10a-10c, thus producing a quantity? increasing pincushion distortion correction. The decrease in the difference in the levels of the direct voltages between the inversion terminal and

Claims (13)

1. Power supply and deflection circuit, of the modulated type, comprising: a deflection winding; switching means coupled to said deflection winding and operated at a deflection frequency for generating a scan current in said deflection winding during a trace interval of one deflection cycle; a deflection retrace capacitor for forming a deflection retrace resonant circuit with said deflection winding to produce a retrace pulse voltage during a retrace interval of said deflection cycle; a source of supply energy, a supply inductor coupled to said source, characterized by a second capacitor (C) coupled coupled to said power inductor (W1) and to said switching means (Q1) to form a second resonant circuit (30) with said power inductor (VI) within said retraction range, to generate a voltage pulse; a load circuit (W2) excited by said impulse voltage; an inductor (Li) interposed during said retrace interval, in a current path between said deflection retrace circuit and said second resonant circuit and a modulation current source (24) coupled to said impedance (Li) to produce modulation of said scanning current as the said modulation current varies. 2. Power supply and deflection circuit, of the modulated type, according to claim 1, characterized in that said impedance comprises a modulation inductance (Li) having a relatively high value at the high frequencies represented, for example, by the retrace frequency deflection. 3 Power supply and deflection circuit, of the modulated type, according to claim 2, characterized by the fact that a resonant frequency of said second resonant circuit (30) is located in correspondence with or in proximity to the second resonant circuit (30). of said deflection retrace frequency. 4. Power supply and deflection circuit, of the modulated type, according to claim 2, including a capacitor. of trace coupled to said deflection winding, to apply, thereto, a trace voltage and in which the amplitude of said scanning current varies as said trace voltage varies, characterized in that said impedance (Li) couples said modulating current ^? (121) to said resonant retrace circuit of the deflection (25) to vary said trace voltage as said modulation current varies. 5. Power supply and deflection circuit, of the modulated type, according to claim 1, or claim 2, wherein said deflection circuit comprises a horizontal deflection circuit, characterized by a source of recurrent signals at the vertical frequency (43) coupled to said modulating current source (Q2) to vary said modulating current at a vertical frequency, to provide a waveform of the scan current corrected for the EAST-WEST pincushion twist. 6. Power supply and deflection circuit, of the modulated type, according to claim 1, or claim 2, characterized in that said impedance (T2) comprises a first winding (Va) connected to said source (W3 *) of modulation current and a second winding (wb) magnetically coupled to said first winding and sandwiched between said deflection retrace circuit and said second resonant circuit, during said deflection retrace interval. 7. Power supply and deflection circuit, of the modulated type, according to claim 6, characterized in that said modulating current source comprises a voltage source (81) connected to the first winding (Va) of said impedance (T2) and to a first switch (Q2), of the controllable type, said switch, of the controllable type, being sensitive to a control signal to impulsively modulate the switching of the same. 8. Power supply and deflection circuit, of the modulated type, according to claim 7, characterized in that they comprise a rectifier (D4) connected to the second winding (Vb) of said impedance (T2) to produce an operating mode of the controllable switch back converter type (Q2). 9. Power supply and deflection circuit, of the modulated type, according to claim 8, wherein said deflection circuit and said deflection winding comprise, respectively, a horizontal deflection circuit and a horizontal deflection winding, characterized by means (Q3) for developing a repeating signal at the vertical frequency and means (UlA) coupled to said first controllable switch (Q2) and responsive to said repeating signal at the vertical frequency, to develop said control signal, as a control pulse which it is modulated at the vertical frequency and applied to said first controllable type switch, in order to produce a modulation of said scanning current, in such a way as to provide an EAST-WEST correction of the pincushion distortion. 10. Power supply and deflection circuit, of the modulated type, according to claim 2, characterized in that said switching means (Q1) operating at the deflection frequency, the resonant retrace circuit of the deflection (25) and said second resonant circuit (30) are connected to a common junction terminal (22). 11. Power supply and deflection circuit, of the modulated type, according to claim 10, characterized in that said switching means operated at the deflection frequency, comprise a deflection output device (Q1) having a current conduction path main, switched at said deflection frequency, and two rectifiers (D1, D2) connected in series, said complex series being arranged in parallel with said conduction path of the main current of said output device (Ql) said impedance (T2) being coupled to a junction terminal, in common with the two rectifiers. 12. Power supply and deflection circuit according to claims 1, 2, 4? 10 and 11, characterized by the fact that said supply inductance (?) Comprises a transformer for pulses, having a first winding (wi *) coupled to said second capacitance, to generate said impulse voltage at the ends of said first winding and having a high voltage winding (W5 ') for boosting said pulse voltage, said load circuit including a terminal for the final acceleration voltage (u) and a high voltage circuit (31) connected to said terminal for voltage. of final acceleration (u) and to said high voltage winding (V5 *) for the development of a final acceleration voltage at said terminal for the final acceleration voltage (u). 13 Power supply and deflection circuit, according to claim 12, wherein the variations in loading by the current on said terminal for the final acceleration voltage tend to distort said pulse voltage, characterized in that said impedance (T ) allows the deflection retrace pulse voltage developed by said deflection retrace resonance circuit (25) to be substantially free of any tendency to crochet as a function of said variations in current charging.