FR2788920A1 - Control method for vertical deflection screen sweep circuit, involves using output amplifier stage, principal and auxiliary voltage supplies, and two bidirectional interrupters - Google Patents

Abstract

The method involves using a control circuit with an output amplifier stage (ETS), a main voltage supply, and an auxiliary step-up voltage supply (ALM). A first bidirectional interrupter (T3, D3) is connected to the output stage and controlled so to allow the delivery of stepped-up voltage for a rapid return of spot. The the second bidirectional interrupter (T4, D4) is connected between the principal voltage supply (+Vcc) and the output stage, and controlled so to prevent the delivery of stepped-up voltage during the vertical spot sweep. The output stage (ETS) comprises two transistors (T1, T2) functioning in class D in alternating switching mode for the control of vertical spot sweep. The common node (BSS) of the two transistors is connected to a current-smoothing filter (F) with output to vertical deflector (Vers DV). Each interrupter comprises a transistor (T3, T4) and a diode (D3, D4) in antiparallel connection. The vertical spot sweep comprises two phases; in the first phase the current is positive, ie. in the direction of deflector, and in the second phase the current is in opposite direction, ie. back to the output stage (ETS); the total duration is e.g.19 ms. The rapid spot return is in two following phases. In the first phase the current is negative, and in the second it is positive. The duration is e.g. 0.1 ms, and 0.9 ms, respectively. In the course of the second phase the transistor (T3) is conducting, the transistor (T4) is blocked, and the deflector voltage is constant. A variant of the control circuit comprises an auxiliary, known as flyback, capacitor and an additional transistor interrupter. The second variant of the control circuit comprises a capacitor known as bootstrap for utilising the stored energy. The third variant of the control circuit comprises the flyback capacitor for the control of the first bidirectional interrupter. The fourth variant comprises an output stage in the form of a full bridge circuit, containing four transistors with diodes in antiparallel connection and current-smoothing filter with two inductors for a symmetric connection to the deflector in series with a resistor, and a capacitor.

Description

I Device for controlling a vertical deflection circuit of a spot

  scanning a screen, in particular for a television or computer monitor. The invention relates to the control of the vertical deflection of a

spot scanning a screen.

  The invention is advantageously but not limited to the screens of televisions and / or computer monitors. A spot scans a screen in two orthogonal directions, namely a line scan and a vertical scan. Line scanning

  occurs at a much higher frequency than vertical scanning.

  For example, for a television application, scanning-

  line can be carried out at 15625 Hz, while the vertical scanning is carried out for example at 50 Hz. When the spot has undergone a line sweep, there is then a line feed to carry out the scanning of the next line. Simultaneously with the line scan, the vertical scan allows the spot to scan the screen from top to bottom. At the end of the forward vertical scan, there is then a rapid return of the spot at the top left of the screen (frame return) and commonly called by the man of the

  profession in English "Flyback".

  The vertical deflection of the spot therefore comprises a forward phase of vertical scanning followed by a rapid return phase of the spot. The vertical deflection is generated by a vertical deflection circuit, conventionally

  inductive, generating a magnetic spot deflection field.

  Conventional devices for controlling vertical deflection circuits (or more simply "vertical deflectors") are essentially formed by amplifiers operating in class AB (linear), that is to say whose output stage is formed by transistors working in their linear domain and therefore producing a continuous output voltage. The amplifier amplifies a setpoint signal, generally in the form of a sawtooth, so as to deliver a signal for controlling the vertical scanning of the spot. Furthermore, in order to ensure the rapid return of the spot, these control devices are equipped with means for generating an overvoltage at the terminals of the deflector. Currently, such control devices have an actual efficiency of the order of 50% and generally require heat sinks

relatively large heat.

  The invention aims to remedy this drawback and one of the aims of the invention is to increase the efficiency of such a control circuit while reducing the complexity of the heat sinks, so as to

  reduce the overall cost of the control device.

  Another object of the invention is to produce such devices for

  control in the form of integrated circuits.

  The invention therefore proposes a device for controlling a vertical deflection circuit of a spot scanning a screen, comprising an output amplifier stage supplied by a main power supply (for example 12 Volts) for controlling the vertical scanning of the spot, an auxiliary power supply capable of delivering an overvoltage, and a first bidirectional switch connected to the output stage and controllable so as to allow the delivery of said overvoltage to the

  vertical deflection circuit for rapid return of the spot.

  According to a general characteristic of the invention, the output stage is a stage with at least two transistors capable of operating in alternating switching at least for the vertical scanning control of the spot, this stage being associated with a smoothing filter connected to the common terminal of the two transistors. In addition, the device comprises a second bidirectional switch connected between a first transistor of the output stage and a first terminal of the main supply, this second bidirectional switch being controllable so as to prevent the delivery of said overvoltage during the control of

vertical scanning of the spot.

  In other words, the invention proposes the production of a control device, the output stage of which operates in class D, which makes it possible to obtain a yield which can range up to 90%. In addition, in combination with this operation in class D, it is necessary to provide the second bidirectional switch which is controlled so as to prevent the delivery of the overvoltage, in particular when, in a second phase of the forward scan, the second transistor

the output stage is blocked.

  All the transistors of the control device, whether those of the output stage or those forming the various bidirectional switches, can be bipolar transistors. This being so, in particular with a view to production by integrated circuit, it is particularly advantageous for these transistors to be field effect transistors with isolated gate (MOS transistors), for example with N channel. Although in theory, it does not it is not necessary to connect a diode mounted in anti-parallel to its terminals on each transistor, this is preferable, especially if bipolar transistors are used, in order to allow good conduction of the transistors in both directions, but also when MOS transistors are used so as to avoid an increase in the threshold voltage of these transistors which generally operate under strong signals. In practice, the diode mounted in anti-parallel is produced by connecting the source of the transistor to the substrate ("bulk" in English). We recall here more generally,

  that in the sense of the present invention, a diode is said to be mounted in anti-

  parallel to the terminals of a transistor when the anode of the diode is connected to the source of the transistor, while the cathode of the diode is connected to the drain

  of the transistor (when it is a MOS transistor).

  According to one embodiment of the invention, the first bidirectional switch comprises a transistor and a diode mounted in antiparallel across the terminals of the transistor, the anode of the diode being connected to the first transistor of the output stage. The second bidirectional switch, which makes it possible to avoid the delivery of the overvoltage during the vertical scanning control of the spot, comprises a transistor connected in series between the first output stage transistor and the first terminal of the main power supply (by example + Vcc). This second bidirectional switch also includes a diode mounted in anti-parallel to the terminals of the transistor, the cathode of this diode being connected to the first transistor of the output stage and the anode being connected to said first terminal of the main power supply. In addition, the transistor of this second switch is conductive while the transistor of the first switch is blocked, and vice versa. Two alternative embodiments are possible to generate the overvoltage necessary for the rapid return of the spot. One can provide an external auxiliary power supply or an auxiliary power supply called

  internal and generally consisting of a capacitor.

  In the first variant (external auxiliary power supply), the first bidirectional switch is connected in series between

  the auxiliary power supply and the first transistor of the output stage.

  In the second variant (internal auxiliary power supply), the auxiliary power supply includes a capacitor, a first terminal of which is connected on the one hand to the first terminal of the main power supply (+ Vcc for example) via the first bidirectional switch , and on the other hand to a second terminal of the main supply (- Vcc) by means of a controllable auxiliary switch. The second terminal of the capacitor (positive terminal for example) is connected to the first transistor of the output stage and to the second bidirectional switch. The auxiliary switch is then

  open when the first bidirectional switch is closed and vice

  vice versa. According to one embodiment of the invention, the control device comprises control means capable of controlling the

  transistors of the output stage and the various switches of the device.

  More specifically, during the vertical spot scan control, the control means control the transistors of the output stage alternately taking into account a setpoint signal present at the input of the device. In addition, during this vertical scanning phase of the spot, they open the first bidirectional switch and close the second bidirectional switch. Furthermore, during the fast spot return command, the control means make the first transistor of the output stage conductive, close the first switch.

  bidirectional and open the second bidirectional switch.

  Furthermore, when the so-called internal auxiliary power supply variant is used, the control means close, during the vertical scanning command of the spot, the auxiliary switch and open it during

  the spot fast return command.

  According to one embodiment of the invention, the device comprises a pre-amplification stage receiving the reference signal counter-reacted by the current passing through the vertical deflection circuit. This pre-amplification stage delivers an error signal. The device further comprises detection means capable of detecting the crossing of a predetermined threshold by the error signal. The control means then trigger the rapid return phase of the spot when the

  error signal crosses said threshold.

  It is also possible, as a variant, for the output stage to be formed by four transistors in a complete bridge arrangement. In other words, the output stage then comprises two other transistors capable of operating in alternating switching at least for the vertical scanning control of the spot. The smoothing filter is then connected between the common terminal of the first two transistors and the common terminal of the other two transistors of the output stage. The smoothing filter is also distributed on either side of the vertical deflection circuit. Of course, in this case, the means making it possible to generate the overvoltage necessary for the rapid return of the spot, as well as the means making it possible to inhibit the delivery of this overvoltage during the vertical scanning of the spot, do not

  are connected to only one pair of bridge transistors.

  Other advantages and characteristics of the invention

  will appear in the description of embodiments, in no way limiting,

  and attached drawings, in which: - Figure 1 very schematically illustrates the architecture of a control device according to the invention, - Figure 2 illustrates in more detail an embodiment of the output stage and the means for generating the overvoltage necessary for the rapid return of the spot, - Figure 3 illustrates a setpoint signal and an operating mode of the device according to the invention, Figure 4 illustrates another embodiment of an output stage and means for generating the overvoltage necessary for the rapid return of the spot, and - Figure 5 schematically illustrates another alternative embodiment of a device according to the invention, comprising an output stage in full bridge. In FIG. 1, the reference DCS generally designates a device for controlling a DV circuit for vertical deflection of a spot scanning a screen, for example a television screen or a computer monitor screen. The vertical deflection circuit is of conventional, essentially inductive structure. The passage of an IDV current in the vertical deflection circuit creates a magnetic field allowing the

deviation of the spot.

  The control circuit DCS comprises an input terminal BE receiving a reference signal SC which will be discussed in more detail below on the form, and an output terminal BS delivering a current IDV in the

vertical deflector DV.

  The DCS control device has at its head a PMP preamplification stage, mounted in this case as an inverter, and whose inverting input is connected to the input terminal BE via a first resistor R1. The inverting input of the PMP preamplifier is also connected via a second resistor R2 to another terminal BA of the deflector DV. This inverting input is

  also connected to the output of the PMP amplifier by a resistor R4.

  Resistors R1 and R4 set the gain of the PMP preamplifier relative to the setpoint signal and resistors R2 and R4 set the gain for

the feedback loop.

  A resistance R3, typically of the order of 1 Ohm, connects

  conventionally the deflector DV to ground.

  The non-inverting input of the PMP preamplifier is connected to

a reference voltage Ref.

  The output of the PMP preamplifier delivers an error signal ú which will be taken into account in particular by DTF detection means

  which will be discussed in more detail below on the structure and function.

  The DCS device also includes a BLS output block comprising, as will be seen in more detail below, an output stage with two or four transistors operating in class D. In FIG. 1, a PWM block illustrated very schematically upstream of the BLS block, receives the signal ú and includes control means intended to control the various transistors of the BLS output block. These control means include in particular, as will be seen in more detail below, means for generating pulses of variable widths intended to be applied to the gates of the transistors of

the output amplifier stage.

  If we now refer more particularly to FIG. 2, it can be seen that the BLS output block comprises an ETS output amplifier stage formed here of two half-bridge transistors T1 and T2. These two transistors TI and T2 are here two NMOS transistors each associated with a

  diode D1 (respectively D2) mounted in anti-parallel to their terminals.

  More specifically, the cathode of diode D 1 is connected to the drain of transistor T1, while the anode of diode D2 is connected to the source of transistor T2

  itself connected to the negative terminal - Vcc of the main power supply.

  The anode of diode D 1 and the cathode of diode D2 are connected together to the common terminal of transistors T1 and T2 and form the output terminal BSS of this stage ETS. This output terminal BSS is connected to the terminal BS of the control device DCS, and therefore to the deflection circuit DV

  via a smoothing filter F, capacitive inductive.

  The gates of the transistors T1 and T2 are controlled by the

  control means incorporated in the PWM block.

  The diodes Dl1 and D2 are here produced by the link of the source

  from each transistor T1, T2 to the substrate.

  The BLS block also includes MFB means associated with this ETS output stage and intended in particular to control the generation of

  the overvoltage necessary for the rapid return of the spot.

  More specifically, in the variant described in this FIG. 2, and corresponding to an auxiliary supply ALM external to the BLS block (for example an auxiliary voltage source of several tens of Volts), the means MFB comprise a first bidirectional switch formed here of an NMOS transistor T3, the source of which is connected to the drain of the first transistor T1 of the ETS stage, and the drain of which is connected to a terminal BAL intended to receive the voltage VF delivered by the auxiliary supply ALM. This first bidirectional switch also includes a diode D3 whose anode is connected to the source of transistor T3 and whose cathode is connected to the drain of transistor T3. The gate of transistor T3 is also controlled by the control means incorporated in the PWM block. In addition to this first bidirectional switch, the MFB means comprise a second bidirectional switch formed by an NMOS transistor T4 and a diode D4 mounted in anti-parallel mode across the terminals of transistor T4. More specifically, the drain of transistor T4 and the cathode of diode D4 are connected to the drain of the first transistor T1, while the source of transistor T4 and the anode of diode D4 are connected together to the + terminal.

Vcc of the main power supply.

  We will now describe in more detail the operation of the device according to the invention, with particular reference to

Figures 1, 2 and 3.

  The upper part of FIG. 3 illustrates a conventional form of a reference signal SC. Such a signal SC which illustrates either the current or the voltage at input terminal BE, consists of a succession of ramps RP1 centered in the example described around the level 0 and each typically having a duration of 19 ms. Each ramp RP1 is followed by a decreasing portion RP2 having a duration of the order of 0.1 ms, itself followed by a flat portion whose duration is of the order of 0.9 ms. Well

  of course, these numerical values are given here by way of example.

  The lower part of Figure 3 illustrates the shape of the IDV current

  circulating in the vertical deflector DV.

  The ramp RP1 of the setpoint signal SC corresponds to a linear decrease in the current IDV corresponding to the vertical scanning phase of the spot on the screen. This decrease takes place between two opposite values, for example + 1 Ampere. In a first phase B 1 of the scanning, the current IDV is positive, that is to say it is outgoing

  vis-à-vis the ETS output stage and therefore entering the DV deflector.

  In the second phase B2 of vertical scanning, the current IDV is negative, that is to say that it is outgoing with respect to the deflector DV and by

  therefore re-entering vis-à-vis the ETS floor.

  The rapid return phase of the spot corresponds to the growth of the DV current from the value -1 Ampere to the value +1 Ampere. It should be noted here that this rapid return of the spot is initialized by the decreasing portion RP2 of the setpoint signal SC, but takes place over a slightly longer duration, typically of the order of 0.8 to 0.9 ms. . This is the reason why the setpoint signal SC comprises a flat part making it possible to trigger the next ramp only when the spot has actually returned to its starting position (at the top left of the screen). During this rapid return phase, the MFB means create an overvoltage, typically of the order of a few tens of volts, at the terminals of the deflector DV. Again, the rapid return of the spot comprises two phases, namely a first phase FB 1 during which the current IDV is entering the stage ETS, and a second phase FB2 during

  which the IDV current is outgoing vis-à-vis the ETS stage.

  During the vertical scanning of the spot (phases B1 and B2), the control means alternately make the transistors TI1 and T2 conductive and blocked at a switching frequency much higher than the vertical scanning frequency (in this case, for example higher or equal to 100 kHz). The average value of the voltage, at the common point BSS of the transistors, is then recovered at the output terminal BS of the output stage, which is smoothed in the smoothing filter F, so as to obtain the decreasing appearance of the IDV current illustrated in Figure 3 (phases B 1 and B2). Of course, the width of the control pulses intended to make each of the transistors conductive or blocked, depends on the value of the setpoint signal, and consequently on the current instant of the vertical scanning phase. Thus, in the first phase B1 of the scanning, the

  transistor T1 will be longer conductive than transistor T2 and vice

  versa in the second phase B2 of the scan. In other words, the duration of a control pulse intended to make the transistor T1 conductive decreases from approximately 90% of the switching period to approximately 10% of the switching period. Simultaneously, the duration of the control pulse intended to make the transistor T2 conductive increases from approximately 10% of the switching period to approximately 90% of the switching period. When the IDV current passes through the zero value, O10 each of the control pulses occupies 50% of the switching period. During the two scanning phases B 1 and B2, the control means block the transistor T3 (first bidirectional switch open) and make the transistor T4 conductive (second switch

bidirectional closed).

  Consequently, during the first phase of the scan B1, when the transistor Tl conducts, the current flows in the transistor T4, the diode D4 and the transistor T1. When transistor T1 is blocked, the current

  flows through transistor T2 and diode D2.

  In the second phase B2 of the scanning, when the transistor T2 conducts, the current flows in the transistor T2. On the other hand, when the transistor T2 is blocked, the current flows in the transistor Tl and in the

  diode D1, then in transistor T4.

  It should be noted here that the presence of the bidirectional switch T4, D4 is essential to prevent the re-entering recirculation current passing through the diode Dl and the transistor T1 from prematurely triggering the generation of the overvoltage VF, when the transistor T2 is blocked in the second phase B2 of the scan. Indeed, in the absence of conduction of the transistor T4, the recirculation current could then cross the diode D3 and cause the generation of a start of overvoltage at the terminals of the deflector, causing a start of rapid rise of the spot

  until the transistor T2 is again conductive.

  On the other hand, due to the conduction of the transistor T4 and due to the fact that the overvoltage VF is chosen to be greater than the main supply voltage + Vcc, the current does not flow in the diode D3

  and does not cause the premature generation of the overvoltage.

  It should also be noted here, that in theory it would be necessary to close the second bidirectional switch (that is to say to make the transistor T4 conductive) only in the second phase of the scan B2 and during the periods during which transistor T2 is blocked. This being the case, this would require controlling the transistor T4 at the high switching frequency. It is therefore much simpler to leave the transistor T4 conductive for the entire duration of the scan.

  vertical of the spot (phases B 1 and B2).

  At the end of the vertical scanning of the spot, the control means interrupt the switching of the transistors TI1 and T2 at the switching frequency and make the transistor T1 conductive. In addition, the control means open the second bidirectional switch, that is to say block the transistor T4 and close the first bidirectional switch, that is to say make the transistor T3 conductive. This therefore results in the generation of an overvoltage across the terminals of the DV deflector and therefore the rapid return of the spot. During the first part FB 1 of the fast return, the current flows in the diode Dl and the transistor T1, then in the diode D3 and the transistor T3. During the second part FB2 of the fast return, the current flows in the transistor T3, then in the

transistor T1.

  It should be noted here that it would have been possible to continue, during this rapid return phase, the alternating switching of the transistors T1 and T2 of the output stage at the switching frequency. This being so, the fact of interrupting this switching and of making the transistor T1 conductive throughout the duration of the fast return, makes it possible to permanently apply the overvoltage VF across the terminals of the deflector (that is to say without loss of voltage during periods when the TI transistor would have been

blocked).

  The control means which make it possible to control the various transistors of the control device according to the invention, in the manner which has just been described, can be easily produced by a person skilled in the art using conventional logic circuits. That said, it is advantageous to detect the end of the vertical scanning of the spot in order to be able to control the transistors T3 and T4 to trigger the fast return phase. This is the role of the DTF detection means. These are essentially formed by a comparator which compares the error signal ú

  at a predetermined threshold, for example + 0.5 volts.

  When, at the end of the vertical scanning of the spot, the error signal increases until it exceeds the threshold, due to the inertia of the deflector, the detection means then deliver to the control means a detection signal in response to which the control means control the

  different transistors of the control device as indicated above.

  The variant illustrated in FIG. 4 corresponds to the use of an internal auxiliary supply consisting of a capacitor C. More specifically, in the example illustrated, the positive terminal of the capacitor is connected to the drain of the transistor T1 and to the drain of the transistor T4, while the other terminal of the capacitor is connected to the source of transistor T3, as well as to the terminal - Vcc of the main supply via an auxiliary switch T5 which can also be formed of a transistor

  NMOS controlled on its grid by the control means.

  Furthermore, in this variant, the drain of the transistor T3 and the cathode of the diode D3 are connected together to the terminal + Vcc of

main power.

  During the vertical scanning of the spot, the control means control the transistors T1 and T2 as explained above and render

  the transistors T4 and T5 conductors. The transistor T3 is blocked.

  During the first phase B 1 of the scanning, the current then passes through the transistor T4 in the diode D4, then through the transistor T1 when the latter is conductive. When the transistor T 1 is blocked, the current flows

  in transistor T2 and in diode D2.

  In the second phase B2 of the vertical scanning, the current passes through the transistor T2 when the latter conducts, and when it is blocked,

  it passes through transistor T1 and diode D1, then through transistor T4.

  At the end of the second phase B2 of the scanning, the capacitor

It is loaded.

  The detection of the end of the scanning is carried out as explained above. During the rapid return phase of the spot, the transistors T4 and T5 are blocked by the control means and the transistor T3 is returned

  conductor, as well as transistor T1.

  During the first phase FB 1 of the rapid return, the current flows through the diode D1 and the transistor T1, then into the capacitor C, then into the

transistor T3 and diode D3.

  In the second phase FB2 of the fast return, the current, coming from the terminal + Vcc passes through the transistor T3 then the capacitor C and the transistor T1. The voltage present at the terminals of capacitor C during the rapid return of the spot allowed the generation of the overvoltage. The function of transistor T4 is identical to that which was described above for the

  variant using the external auxiliary power supply.

  In one or other of the variants which have just been described, the output stage ETS, the means MFB and the filter F can be easily

  made within the same integrated circuit. FIG. 5 schematically illustrates an alternative embodiment of

  the exit floor in full deck. More precisely, according to this variant, two other transistors are added to the first transistors T1 and T2

  transistors T 10 and T20 associated with two diodes D10 and D20 mounted in anti-

  parallel. The transistors T 1, T2, T 10 and T20 are supplied between + Vcc and ground. The transistors T1 and T10 are controlled simultaneously and the transistors T2 and T20 are controlled simultaneously. Of course, the MFB means are only connected to one of the two pairs of transistors, in this case for example the transistors T1 and T2. The smoothing filter then consists of two inductors LF, respectively connected to the common terminals of the two transistors of each pair. The deflector and the resistor R3 are connected in series between the two inductors LF, and the capacitance CF of the filter F is mounted in parallel across the terminals of the deflector DV and of the resistor R3. The feedback loop is here performed in a differential manner as indicated very schematically by the two

  arrows across the resistor R3.

Claims (10)

  1. Device for controlling a vertical deflection circuit of a spot scanning a screen, comprising an output amplifier stage (ETS) supplied by a main power supply for controlling the vertical scanning of the spot, an auxiliary power supply (ALM) capable to deliver an overvoltage, and a first bidirectional switch (T3, D3) connected to the output stage and controllable so as to allow the delivery of said overvoltage to the vertical deflection circuit for rapid return of the spot, characterized in that the output stage (ETS) is a stage with at least two transistors (T1, T2) capable of operating in alternating switching at least for the vertical scanning control of the spot, this stage being associated with a smoothing filter ( F) connected to the common terminal (BSS) of the two transistors, and by the fact that the device comprises a second bidirectional switch (T4, D4) connected between a first transistor (T1) of the output stage and a first terminal (+ Vcc) of the main supply and controllable so as to prevent the delivery of said overvoltage during the order vertical scanning of the spot.   2. Device according to claim 1, characterized in that each transistor (T1, T2) of the output stage comprises a diode (D1,   D2) mounted anti-parallel to its terminals.   3. Device according to claim 1 or 2, characterized in that the first bidirectional switch comprises a transistor (T3) and a diode (D3) mounted in anti-parallel across the terminals of the transistor (T3), the anode of which is connected to the first transistor (T1) of the output stage, by the fact that the second bidirectional switch includes a transistor (T4) connected in series between the first transistor (TI1) of the output stage and the first terminal (+ Vcc ) from the main power supply, and a diode (D4) mounted in anti-parallel mode across the transistor (T4), whose cathode is connected to said first transistor (T1) of the output stage and whose anode is connected to said first terminal (+ Vcc) of the main power supply, and by the fact that the transistor (T4) of this second switch is conductive while the transistor (T3) of the first switch is blocked, and vice versa.   4. Device according to claim 1, 2 or 3, characterized in that the first bidirectional switch (T3, D3) is connected in series between the auxiliary supply (ALM) and the first transistor (T1) of the output stage.   5. Device according to claim 1, 2 or 3, characterized in that the auxiliary supply comprises a capacitor (C) of which a first terminal is connected on the one hand to the first terminal (+ Vcc) of the main supply by means of the first bidirectional switch (T3, D3) and on the other hand to a second terminal (- Vcc) of the main supply by means of a controllable auxiliary switch (T5), by the fact that the second terminal of the capacitor is connected to the output stage and to the second bidirectional switch (T4, D4), and by the fact that the auxiliary switch (T5) is open when the   first bidirectional switch (T3, D3) is closed and vice versa.   6. Device according to one of the preceding claims,   characterized by the fact that it includes control means (PWM) capable of controlling the transistors of the output stage and the various switches of the device, by the fact that during the vertical scanning control of the spot, the control means control the transistors (T 1, T2) of the output stage alternately taking into account a setpoint signal (SC) present at the input of the device, open the first bidirectional switch (T3, D3) and close the second switch bidirectional (T4, D4), and by the fact that during the fast spot return control, the control means make the first transistor (T1) of the output stage conductive, close the first bidirectional switch (T3, D3) and open the second two-way switch (T4, D4).   7. Device according to claims 5 and 6, characterized by the   fact that during the vertical spot scan command, the control means close the auxiliary switch (T5), and by the fact that during the fast spot return command, the control means open the auxiliary switch (T5).   8. Device according to claim 6 or 7, characterized in that it comprises a pre-amplification stage (PMP) receiving the reference signal (SC) counter-reacted by the current (IDV) passing through the deflection circuit, and delivering an error signal (ú), and by the fact that it further comprises detection means (DTF) capable of detecting the crossing of a predetermined threshold by the error signal (ú), and by the fact that the control means trigger the rapid return phase of the spot when the error signal crosses said threshold.   9. Device according to one of the preceding claims,   characterized by the fact that the output stage (ETS) comprises two other transistors (T10, T20) capable of operating in switching mode alternately at least for controlling the vertical scanning of the spot, the four transistors forming a complete bridge arrangement , and by the fact that the smoothing filter (F) is connected between the common terminal of the first two transistors and the common terminal of the other two transistors, and is   distributes on both sides of the deflection circuit.   10. Device according to one of the preceding claims,   characterized by the fact that all the transistors are insulated gate field effect transitors, with the source connected to the substrate so as to form the associated diode mounted in anti-parallel mode, and by the fact that it is produced under the form of an integrated circuit.