FR2520958A1 - AUXILIARY CIRCUIT FOR TELEVISION - Google Patents

Abstract

THE INVENTION RELATES TO A DISPLAY SYSTEM RESPONDING TO THE STATE OF AN ON-OFF CONTROL SIGNAL AND WHICH INCLUDES A DEVIATION WINDING; A DEVIATION GENERATOR PRODUCING, IN NORMAL MODE, A SCAN CURRENT IN THE DEVIATION WINDOW; A SWITCHING CURRENT SUPPLY DEVIATION SYNCHRONIZED BY THE OPERATION OF THE DEVIATION GENERATOR DURING NORMAL MODE TO APPLY CURRENT TO THE DISPLAY SYSTEM. ACCORDING TO THE INVENTION, A MEANS (Q2, W, W) COUPLED TO THE DEVIATION GENERATOR 21 AND RESPONDING TO THE ON-OFF CONTROL SIGNAL SENSITIVELY SHORTS THE DEVIATION GENERATOR 21 ON RECEPTION OF THE STOP STATE FROM THE CONTROL SIGNAL TO CHANGE THE OPERATION OF THE SWITCHING CURRENT SOURCE 20 TO A RESERVE OPERATION MODE. THE INVENTION APPLIES IN PARTICULAR TO TELEVISION.

Description

The present invention relates to the function

  The present invention can be used in main power supplies for back-up operation, and in particular can be used in conjunction with a power supply that supplies remote control circuits in the television during auxiliary operation. in a simple conversion system power supply (SICOS) as described in the publication

  British Patent No. 2 094 058 A, published September 8, 1982.

  Several types of auxiliary circuits are known

  for TV We know, for example, a small transformation

  AC power supply that powers the TV's remote control circuits, and a relay that turns the TV on and off. Such an auxiliary circuit can consume only about 6 watts, but it is a relatively expensive attempt for a source.

auxiliary power supply.

  Another type of auxiliary circuit is a switched-mode power supply with integrated circuit control such as with a TDA 4600 control integrated circuit, and a relay which stops most of the secondary voltages of the circuit. power supply in switched mode during the

  reserve or auxiliary operation The source of food

  Switching mode operation operates at approximately k Hz during auxiliary operation to achieve the required wide range of control. Auxiliary or reserve dissipation of such a system is

  relatively large, between 10 and 20 watts.

  Another type of auxiliary circuit is a trans-

  network current trainer that is coupled to a switched mode regulator without relays During auxiliary or standby operation, the horizontal oscillator is de-energized by the remote control circuit The use of a network current transformer is a relatively cumbersome to the design of a circuit

auxiliary or reserve.

  The spare circuit according to the invention has the following characteristic: the initiation of the auxiliary or reserve operation by short-circuiting the horizontal switch, for example by continuously maintaining the horizontal output transistor in saturation during operation. When using a main power source such as the above-mentioned SICOS power supply, short-circuiting of the go switch results in the SICOS power supply being switched on. autonomous oscillation approximately at the horizontal deflection frequency, with a ratio of the pulse duration per cycle which is almost equal to the ratio between the forward and return intervals During the reserve, the current for the remote control circuit is flows through the switch to short circuit, a secondary winding of the return transformer The reserve power consumption can be lower

  at 10 watts and typically it is of the order of 6 watts.

  The usable current for the remote control circuit can

  be in the range of 1.5 watts to 12 volts.

  The invention will be better understood, and other purposes, features, details and advantages thereof

  will become clearer during the description

  explanatory text which will follow with reference to the accompanying schematic drawings given solely by way of example illustrating an embodiment of the invention and in which: FIG. 1 shows a source of power supply and a deflection circuit for a television set with backup remote control circuit according to the invention; Fig. 2 illustrates waveforms associated with the circuit of Fig. 1 during normal mode operation; Fig. 3 illustrates waveforms associated with the circuit of Fig. 1 during a standby mode of operation; and FIG. 4 illustrates a detailed embodiment of the output circuit of the power supply.

SICOS.

  In Fig. 1, a SICOS power supply 20, described in the aforementioned UK publication, serves to transfer current from an unregulated power supply terminal B + to various charging circuits of the television which are coupled to the secondary windings. of a return transformer T 1, comprising a high-voltage final load 33 which is coupled to a high-voltage winding W 4 During operation in normal mode, horizontal return pulses, voltage V 3, illustrated in FIG. 2c, developed by the horizontal deflection generator 21 are coupled, by the transformer, to the secondary winding W 2 of the return transformer T 1,

at the primary winding W 1.

  At the take-up of the primary winding W1, the positive return pulses are rectified in peak by a diode D 1, filtered by a capacitor C 1 and applied to the SICOS regulator circuit 22 along a line 34. Controller control 22 is synchronized to the horizontal deflection by the voltage of the return pulses which is applied along a line 29 to develop signals 23 whose pulse width is modulated, having a useful duration which varies with the variations of the amplitude of the voltage of the return pulses The signals whose pulse width is modulated are applied to an input terminal 24 of the power supply source SICOS 20 to modulate according to the width of the pulses, of the push-pull switches 51 and 52 Each switch comprises a transistor, Trl or Tr 2, having an antiparallel unedb, not shown in Figure 1, which is coupled between its collector and its emitter By modulating, according to the width of the pulses, the operation of the switches S1 and 52, the amplitude of the return pulses is maintained relatively constant under variable load and voltage conditions B +.

  The positive voltage developed in the condensa-

  C 1 maintains a transistor Q 1 in saturation, thereby bringing its collector voltage to the potential of the ground 25 and polarizing in reverse a diode D 10 On the secondary side of the return transformer T 1, a reserve or auxiliary switching transistor, the transistor Q 2 in Darlington, is maintained at saturation by the base current flowing from a holding rail 26 through a resistor R 9 and a Zener diode D 5 Thus, the switch to go horizontal 27 and the horizontal driving transistor Q 5 are connected to chassis earth 28 by the switch

remote control driver Q 2.

  The waveforms of FIGS. 2a-2e illustrate

  normal operation of the power source

  SICOS current and horizontal deflection circuit

  of Figure 1 Figure 2a illustrates the voltage of

  V 1 at the junction of the output switches 51 and 52 of the SICOS power supply 20 The dotted waveforms of FIG. 2 indicate the regulation range of the power supply. in solid lines represent waveforms that are

  taken at a typical point of operation of the food

current.

  FIG. 4 shows a detailed embodiment of the circuit of the SICOS power supply source 20 of FIG. 1. The switch 51 becomes conductive at an adjustable instant, T 4, during the forward interval of the horizontal deflection cycle. for coupling the energy storage inductance coil L 1 to the input voltage terminal B + The switch 51 becomes conducting because, near the time T 4, the positive edges of the signal 23 whose pulse width is modulated, turn on the transistor Tr 4, thus passing the transistor Tr 2 of the switch 52 to the opening To maintain the current i 1 in the main winding Lla of the inductor L1, the terminal provided with a point of the winding Lia becomes positive with respect to the terminal without point, thus polarizing the diode D 51

  of the switch If a current decreasing in the winding

  Lia flows to the B + terminal of Fig. 1. The positive voltage at the terminal provided with a point of the winding Lla induces a positive voltage at the terminal provided with a point of the control winding L1 for direct biasing the base-emitter junction of the transistor Trl The transistor Tri resumes the current conduction in the winding Lia when the current i 1 of FIG. 2b becomes positive at a certain moment after

  the time T 4 but during the interval to go T 2 -T 6.

  At the end of the go interval, at time T 6, an adjustable amount of energy has been stored in the inductance coil LM Much of this stored energy is then transferred to the load circuits that are coupled to the return transformer Tl during

  the horizontal return interval T 6-T 7.

  At time T 6, the positive return pulse voltage developed at the winding terminal W1 of the return transformer T1, provided with a point, is applied to the pointless terminal of the winding Lia of the inductor L1. , making positive the terminals without winding point Lia and the control winding or control Llb and Lic The transistor Tr 3 becomes conductive, passing the transistor Tr I to the opening The positive current i 1 is taken by the diode D 52 of the switch 52 almost to the center of the return where the transistor Tr 2 resumes the conduction when the current i 1 becomes negative During the return,

  a resonant transfer of energy takes place by transforming

  back-converter T1, between the inductor L1 and the resonant return circuit comprising the capacitor CR and the horizontal deflection winding LH and the load circuits coupled to the secondary windings W 3

  and W 4 of the return transformer T1.

  FIG. 2 d illustrates the base current i 3 in the horizontal output transistor Q 4, which flows

  of a winding Wbdtun horizontal attack transformer

  FIG. 2 e illustrates the current flowing in a winding WO of the driving transformer T 2. In the vicinity of the time TO, a horizontal driving transistor Q is switched on, producing a reverse current of base i 3 which turns off the horizontal output transistor Q 4 at time T 1 A current i 2, also starting near the time T 0, is produced which charges a capacitor C 8 by a diode D 2 The currents i 2 and during a normal mode of operation are therefore produced by the switching action of the

  horizontal drive transistor Q 5.

  To switch the television to reserve or auxiliary operation mode, a remote control circuit 30 applies the potential of the chassis ground for about one second, as a signal

  stopping control, at the base of the transistor Q 2 of

  When the transistor Q 2 is switched off, the current in the winding W 2 of the return transformer T1 is forced to flow towards the chassis 28 by the winding W of the control unit. horizontal drive transformer T 2 When the conventional current flows out of the terminal provided with a point of winding W 2 of the return transformer, the return current path for this current passes through the output transistor horizontal Q 4 at the winding terminal Wc of the drive transformer T 2 provided

  one point, then the diode D 2 to charge the condensa-

  C 8 at a positive voltage When the conventional current

  tional i flows from the terminal without point of the winding

  W 2 of the return transformer, the return path passes through the diode of the Darlington transistor Q 2, the damping diode D 7 of the go switch 27 and the diode formed by the base-collector junction of the transistor of

horizontal output Q 4.

  The positive current i 2 induced in the winding Wb of the horizontal drive transformer T 2, a current

  positive base i 3 for the horizontal output transistor

  The current i 3 keeps the horizontal output transistor Q 4 in the conducting state. The transformer T 2 therefore serves as a starter transformer which produces a positive feedback of the output of the transistor.

  transistor Q 4, to keep the transistor at saturation.

  During the reserve, the transistor Q 4 is either in direct conduction condition saturated or in condition

  of reverse collector conduction with the amorphous diode

  These conditions result in a short-circuit switch 27 which connects the terminal provided with a point of the winding W 2 of the return transformer to the terminal provided with a point of the With the switch to go continuously short-circuited, the resonant return circuit does not form, thus lowering the return pulse voltages. The supply currents through the diodes D 4 and D 6 become as well as the supply voltage Vb and the current to

  through the retaining rail 26

  command Q 2 therefore remains cut off, even after

  the interval of the stop command signal of a

second above mentioned.

  The voltage Va in the capacitor C 4 is the source voltage for the remote control circuit 30

  excitation of the 12-volt supply rail and the

  This voltage is developed, in reserve operating mode, by the diodes D 2 and D 3, from the positive current of the current 11, which flows in the winding Wc of the drive transformer in the form of current i 2 The horizontal oscillator 32 is in operation during the reserve to facilitate the setting

  in the TV, as will be explained below.

  A Darlington transistor Q 3 serves as a shunt regulator

  to limit the voltage in the capacitor C 8.

  On the primary side of the return transformer T1, while the return impulses collapse during the start of the reserve operating mode, the power source SICOS'20 begins to operate in autonomous mode. Return pulse voltages inhibit the control circuit 22 and cause the transistor Qi to go off With the transistor Q1 off, an RC network comprising resistors R1-R4 and a capacitor C2 is enabled to form a multivibrator arrangement. astable with switches SI and 52

of SICOS.

  The waveforms of FIG. 3 show waveforms associated with the circuit of FIG. 1 in reserve operating mode. As indicated in voltage VI of FIG. 3a, after the time t 1 'the switch If the power source 20 in SICOS is conducting Similarly, near the time t, 1 the left armature of the capacitor C 2 is positive relative to the right armature Therefore, when the switch S1 becomes conductive, the capacitor C 2 begins to discharge through the resistors R 2 and R 3 as indicated in FIG. 3b by the voltage V 2 which decreases

  at the collector of the transistor QI after the time t 1.

  The switch SI of the current source 20 remains conductive due to the regeneration action produced by the control windings Llb and L Ic of FIG. 4. As indicated in FIG. 3a, the switch S1 remains conductive until at time t 3, at which time the transistor Tr I of the switch S1 starts to open At the time t 4, the transistor Tr I is in the off state and the switch 52 has been switched on because of the conduction of the diode D 52, thus bringing

  the voltage VI to the potential of the mass.

  At time t 4, the capacitor C 2 was charged at a voltage of opposite polarity such that the right armature of the capacitor is positive with respect to the left armature With the positive right armature of capacitor C 2 blocked to ground by the switch 52, the base-collector junction of the transistor QI is directly biased, blocking the voltage V 2 to a value just below the potential of the mass, between the times t 4 and t 6 of FIG. time t 4 and t 6, the capacitor C 2 discharges through the base-collector junction of the transistor Qi and through the resistor R 2 of the terminal B + A near the time t 6, the voltage in the capacitor C 2 changes polarity, polarizing in

  reverses the base-collector junction of the transistor QI.

  The capacitor C 2 starts charging from the terminal B +, charging the left armature of the capacitor

  positively compared to the right armature.

  At time t 7, of FIG. 3b, the capacitor C 2 has sufficiently charged to bias the diode D 10 directly and to put the control transistor Tr 4 of the power supply 20 into circuit.

  of the control transistor Tr 4 turns off the transistor

  When the transistor Tr 2 goes off, the diode D 51 of the switch S1 is turned on to resume the current conduction of the main winding Lla of the inductance coil LI of FIG. voltage Vi therefore increases to voltage level B + as illustrated on

Figure 3a.

  The duration of a complete autonomous oscillation of the switches S1 and 52 is, for example, microseconds, which is almost the duration of the horizontal deflection T = 64 microseconds. The autonomous operating period of 70 microseconds is chosen. to be short enough to be

  inaudible to most people in reserve mode.

  The adjustment of the autonomous period can be done by adjusting the value of the resistance R 2 of the multivibrator

astable.

  FIG. 3c illustrates the current i 1 in the winding W1 of the return transformer T1 during a reserve operation As the windings W1 and W2 are coupled very tightly to one another and have approximately

  the same number of turns, the current it in the winding

  W 2 and thus in the collector of the horizontal output transistor Q 4 in reserve mode has about the same shape and the same amplitude as the current i 1 Compared to the currents i 1 and it in normal operating mode, the The current consumption of the power source 20 during the standby is therefore relatively low, for example

6 watts.

  FIG. 3 d illustrates the voltage V 4 in the remote control switching transistor Q 2 during a reserve operation Between the times t 0 and t 2 an interval where the currents in the windings W 1 and W 2 of the return transformer T 1 are negative, the diode of the Darlington transistor Q 2 is forward biased,

  blocking the voltage V 4 at the chassis ground potential.

  Between the time t 2 and the time t 3, the currents i 1 and it are positive and ramp upwards In this interval, the current i 2 in the winding W c of the transformer T 2 is positive, polarizing the diode D 2 in direct and charging the capacitor C 8 to a voltage of the order of 20 volts During this interval, the voltage V 4 is positive and is blocked at the voltage level established by the voltages that were developed in the windings Wc

  of the drive transformer T 2 and in the capacitor C 8.

  In the vicinity of the time t 3, the switch 52 of the power source 20 becomes conductive, starting the negative slope portion of the currents i 1 and i '. After the time t 3, the current i 1 flowing towards the winding Wc of the driving transformer T 2 causes an inversion of the polarity of the voltage developed in the winding Wc The voltage V 4 consequently decreases from the time t 3 to the time t, the moments of the zero crossing of the current. t 5, the current becomes negative, directly biasing the diode of the Darlington transistor Q 2, again blocking the voltage V 4 at the

chassis mass.

  Since the go switch 27 is a short circuit during standby operation, the voltage developed in the return transformer winding W 2 and the same voltage V 4 illustrated in FIG. 3 d, but at a reference level in different alternating current, zero volt Thus, during reserve operation, the peak-to-peak voltage in winding W 2

  is about 25 volts, by way of example in comparison with

  at 900 volts, during normal operation, by reducing the peak-to-peak voltage to about 3% of that achieved during normal operation. The conduction in the horizontal driving transistor Q 5 is prevented due to the reverse bias of diode D 8 or diode D 9.

  of the horizontal oscillator 32 during the operating mode

  Therefore, reserve funds can not interfere with

  the autonomous operation of the power supply 20.

  The reserve current for the telecommunication circuit

  control 30 and the oscillator 32 is derived from the winding Wc of the horizontal drive transformer T 2 by the

  current i 2 which charges the capacitor C 8 and the capacitor

  The average value of the positive part of the current i 2, which can be seen in FIG. 3 f, reaches about 150 milliamperes, reaching about 1.8 watts of usable power at the output of the generator. 12-volt regulator The positive current i 3 in the winding Wb of the transformer T 2, which can be seen in FIG. 3 e, is induced by the current i 2. The current i 3 has a greater amplitude because the Wb winding is only about half the number of turns of the winding Wc For example, the inductance of the winding Wb can be of the order of 200 microhenrys and thus the inductance of the winding W, can be of

the order of 800 microhenrys.

  The resistors R 7 and R 8 serve to filter the base current i 3 By the resistor R 7, energy is stored in the winding Wc to lengthen the base current i 3 when D 2 switches off. horizontal output Q 4 is safely maintained at saturation until the current through its

collector be zero.

  To return the television to normal operation, the remote control circuit 30 applies a positive pulse, an ON command signal to the base of the switching transistor Q 2 by the control rail 31 for about one second until the Subsequently, the holding rail 26 is provided with a sufficient holding current for the transistor. The deflection generator 21, comprising the forward switch 27, is again connected to the ground of the ch seated 28 directly by the switching transistor Q. 2, bringing the potential of

  mass at the emitter of the horizontal output transistor Q 4.

  As a result, the current II in the winding W 2 of the trans-

  feedback transformer is by-passed to ground by the transistor Q 2 away from the winding Wc of the drive transformer T 2 As a result, the current i 2 decreases sharply, and the horizontal output transistor Q 4 is not in

continuous saturated conduction.

  The operation of the SICOS power source 20 changes to a start-up sequence similar to that described in the above British Haferl patent publication. This sequence is controlled by the return oscillations until the voltage is reached. of

  return coupled to the primary winding W1 of the transforma-

  Tl is sufficiently high in amplitude to revalidate the SICOS controller control circuit 22 With the regulator control circuit revalidated, the output switch S1 is turned off in synchronization with the horizontal return At the same time, the voltage return impulse produces the saturation of the IQ transistor, inhibiting the multivibrator network of

  resistors Rl-R 4 and capacitor C 2.

  During the transition from the reserve to the

  while running or passing, the current i 3 changes, no longer being induced by the current in the winding WC of the drive transformer T 2 but being induced by the current in the winding Wa Similarly, during the transition of operating in operation or passing to the reserve or auxiliary, the current i 3 is no longer induced by the winding Wa but is induced by the winding Wc to perform these transitions safely without damaging the horizontal output transistor Q 4, the switching sequence of the transistor Q 4 is not interrupted during the transitions The transistor Q 4 is not switched on when a significant positive voltage V 3

is present at his collector.

  In standby or at rest, the horizontal oscillator 3 Z operates but it is in circuit with the BSE horizontal drive transistor Q 5 only when the voltage V 4 is low Current il, when the voltage V 4 is low , flows in a negative direction from the diode of the Darlington transistor Q 2 Thus, even if switching signals are applied to the base of the drive transistor Q 5 in reserve, only a small negative current i 3

  and does not disturb the operation of the transistor Q 4.

  When the current becomes positive, the voltage V 4 becomes high Conduction in the collector

  of transistor Q 5 is interrupted by diodes D 8 and D 9.

  A positive current i 3 flows to maintain the transient

tor Q 4 in saturation.

  With the television switched from its standby operation to its running or running operation, the transistor Q 2 goes into saturation Immediately after receiving the start control signal, the voltage Vb is at zero volts, resulting in a current

  no i 3 to attack the horizontal output transistor Q 4.

  The current supply circuit 20 continues to operate freely as during standby. The return circuit LH, CR oscillates to produce a voltage of increasing amplitude V 3 at the return frequency during the interval t 1 -t 3 of the FIG. 3. The phase and frequency automatic adjustment part of the horizontal oscillator 32, which can not be seen in FIG. 1, begins to put the output of the oscillator in phase with the phase of the oscillator. oscillating voltage V 3 The oscillating voltage of increasing amplitude developed in the return capacitor CR is coupled, by the winding W1 of the return transformer and the control winding Lic of the inductance coil L1, to the base of the transistor Tr 3 to make it go to closing, thus passing the transistor Tri of the output switch SI to the opening Therefore, the oscillating voltage of increasing amplitude V 3 starts to synchronize the switchover opening of the switch SI

  on the phase of the output of the horizontal oscillator 32.

  As the voltage Vb increases, the oscillator 32 already in the correct phase controls the switching of the horizontal drive transistor Q 5 to apply a base current i 3 in correct phase to the horizontal output transistor Q 4. The oscillating voltage of increasing amplitude causes the transistor QI to close, thereby inhibiting the multivibrator arrangement of the resistors R1-R4 and the capacitor C2, and at the same time validating the regulator control circuit 22 When the regulator control circuit 22 is enabled , the voltage V 3 increases slowly to its nominal value at

steady state.

  When the television switches from standby or standby operation, the transition is controlled and safely brings the horizontal output transistor Q 4 into saturated conduction on a continuous basis When the stop control signal is received , the remote control transistor Q 2 switches to the opening, thus inhibiting the operation of the horizontal driving transistor Q If it happens that the transistor Q 2 passes to the opening during the return, the current induced in the winding Wb of the drive transformer T 2 by the winding Wa is greater than that induced by the winding WC The horizontal output transistor Q 4 remains at the cut-off until the end of the return. Subsequently, the

  transistor Q 4 is maintained in continuous saturation.

  During the first few milliseconds after receiving the stop command signal, the operation

  of the power source 20 is at the lowest frequency

  According to the above-mentioned British publication of P Haferl, the capacitor C1 of FIG. 1 has sufficiently discharged to make the transistor QI open, the multivibrator arrangement of the resistors R1-R4 and capacitor C 2 is enabled and increases the operating frequency of switches SICOS SI and S52 at an autonomous frequency close to that of the horizontal deflection frequency,

  as previously described.

  The arrangement of the reserve circuit of FIG. 1, which has just been described, also offers protection against short circuits and overloads. The switching transistor Q 2 is only controlled by on-off control pulses which When the transistor is turned on or off, it is kept at saturation by the base current applied by the holding rail 26. A short circuit or overload producing a decrease in voltage Vb at a voltage of less than about 6.5 volts will switch the transistor Q 2 switching remote control to the opening and put the TV and the power source 20 in reserve operating mode In reserve operating mode, the voltage Vb collapses totally, preventing the excessive current condition from continuing. Thus, the television generally returns to its operating mode of reserve in persistent condition ante overload, even if attempts

  repeated attempts are made to turn it on.

  An example of a horizontal drive transistor T 2 is the following core: cylindrical 30 x 6 mm, material N 27; Wa = 350 turns of wire of 0, 2 mm, 4 m H; Wb = 80 turns of 0.4 mm wire, 200 AH; Wc = 160 turns of wire of 0.2 mm, 800 j "H.

Claims (13)

R E V E N D I C A T I 0 N S   A television viewing system responsive to the state of an on-off control signal, of the type comprising: a deflection winding; a deflection generator operable during a normal mode to produce a flushing current in said deflection winding; a switching current supply deflection synchronized by the operation of said deflection generator during a normal mode for applying current to said television display system; characterized by means (Q 2, Wb, Wc) coupled to said deflection generator (21) and responsive to said on-off control signal for substantially shorting said deflection generator (21) upon receipt of the state stopping the control signal to change the operation of the power supply of   switching (20) to a reserve operating mode.   System according to claim 1, characterized in that the switching power source (20) in stand-by mode operates freely to produce a substantially reduced current. 3. System according to claim 2, characterized in that the deflection generator (20) comprises a return resonant circuit (CR, LH) to produce a   impulse voltage return and o the power source   switching current (20) comprises an inductance (W1) which is coupled to the resonant circuit of   return (C R LH) for transfer of energy between them.   System according to Claim 3, characterized   in that the switching power supply source   (20) comprises a voltage source (B +), an output switching means (S1, 52) coupled to said source (B +) and said inductance (W1) and a control circuit (22) for generating synchronized operation on the deflection of said output switching means during a normal mode, said control circuit (22) responding to the absence of said return pulse voltage to produce autonomous operation of said output switching means (Si, 52); ). 5. System according to claim 1, of the type comprising an input voltage source, the aforementioned supply of switching current coupled to said source, characterized by a transformer (T1) having a first winding (VI) coupled to said power supply. a switching current (20) and a second winding (W 2) coupled to said deflection generator (21) for transferring current from said source to said deflection generator during a normal operating mode, and a power supply source resistor (W, D 2 CS) for producing an operating supply voltage during a reserve operating mode, the current flowing to said reserve supply source by a short-circuit path produced by said means   responding to the on-off command signal.   System according to claim 5, characterized in that the aforementioned switching power supply comprises a control circuit which, in the off state of said control signal, produces an autonomous operation of said switching power supply. for producing an alternating polarity voltage across the second winding (W 2) of said power transformer, the current flowing from said second winding through said path short circuit.   System according to Claim 6, characterized   in that the means responding to the control signal operates   shutdown includes an adjustable switch (Q 2) in parallel with the standby power source (WC 9 D 2, C 8) for shunting the current away from said standby power source during a normal mode of operation . 8. System according to claim 6, characterized in that the switching current source (20) comprises an inductance (LI) for storing therein the energy of the input voltage source (B +), a return pulse voltage developed by said deflection generator being applied to said inductor during a normal mode of operation to transfer stored energy into said inductance.   9. System according to any one of the claims   1, 5 or 8, characterized in that the switching power supply comprises an output switching means (Tri, Tr 2) which is coupled to the input voltage source (B +), a reactive network ( R 1, R 2, R 3, R 4, C 2) coupled to said output switching means and means (QI) responsive to a signal indicating the absence of the generation of feedback pulses to activate the responsive network so as to   to produce autonomous operation.   System according to claim 9, characterized in that the control circuit (22) of the switching power supply responds to a signal at the deflection frequency (at 29) during a normal operating mode to produce an operation. of said switching power supply source in synchronism with the generation of the scanning current and o the reactive network (R1, R2, R3, R4, C2) produces autonomous operation during a standby operating mode at a frequency close to the frequency of deviation. 11. System according to claim 5, characterized in that the short-circuit path is produced by the continuous conduction of the go switch (Q 4) and in that the means responding to the on-off control signal comprises a second a transformer (T 2) having a first winding (Wb) coupled to a control terminal of the go switch and a second winding (Wc) coupled to an output terminal of said go switch and coupled to said power source; reserve current to produce a positive feedback to maintain   the continuous conduction of said switch to go.   System according to claim 11, characterized in that the means responding to the on-off control signal comprises an adjustable switch (Q 2) which is coupled to the go switch (Q 4) for shunting the current away from the second winding (WC) of the second   transformer (T 2) during a normal mode of operation.   13. System according to any one of   claims 11 or 12, characterized by an oscillator   deviating (32) coupled to a third winding (Wa) of said second transformer (T 2) to provide switching at the switch deflection frequency   to go (Q 4) during a normal mode of operation.