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Liste du matériel à répartir par élève et selon les fabrications en cours · . Embed Share. LES MULTIVIBRATEURS ASTABLES. Accueil · Circuits à AOP · Autres circuits · Cours · Liens · Contacts · Livre d’Or. Régime non linéaire. Astable. Ce circuit comporte deux boucles de contre- réaction. Au cours des premiers stade s, on définit, à partir d’un circuit préalablement étudié, oscillateur à quartz 45 MHz – ampli différentiel porte s – multivibrateurs.

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Country of ref document: Date of ref document: Year of fee payment: Ref legal event code: The present invention relates to a feed device regulated in combination with the output stage of a scanning-line circuit of a television receiver, can also provide continuous supply voltages to other circuits of celui- multivibbrateurs, by cutting a generally DC power supply voltage obtained by rectifying and filtering the AC mains voltage by using a switching circuit.

In most of the known switching power supplies, one can vary the output voltage by acting on the duty cycle, that is to say the length of the saturated state closed of the switch, for example, lse periodically transistor chopper with a flip-flop of variable duration as a function of a voltage which can be tapped at the output of a rectifier supplied by a further secondary winding of the transformer so as to form a loop regulation.

Switching power supplies were ment frequently used in television receivers to remove the power transformer industry, large and heavy, to allow regulation of the supply voltage of it. They have often been combined in particular to the output stage of the horizontal scanning circuit which provides a pulse signal at line frequency, operable to control the cutting.

Various combinations of scan circuits and switching power supplies have been described for example in publications FR-A, orwhere regulation is also carried out using the variation of the cyclic ratio of the multivibrateurz and blocked states of the switching transistor or chopper which in some cases is also used as the active element of the output stage final of the scanning-line circuit or of the driver stage controlling thereof.

In the circuit of Figure 4 of this article was inserted between ,es collector of the switching transistor and the winding of the transformer, an inductance of microhenry in parallel with a resistor, which together constitute a protection circuit against rates excessive rise of the collector current of this transistor. The regulation is performed by varying the width of the pulses controlling thereof.

In the above embodiments Figures 6 and 14the cutting inductor is magnetically coupled to the first winding of the line transformer of the fact that it constitutes a second winding, said power supply, so that the transfer energy between the cutting and scanning circuits occurs via the transformer. When the coupling between the first and second windings is loose, the resonant frequencies of resonant circuits each formed by the cutting inductance and the tuning capacitor, and by the inductances of the deflection coils and the first winding of the transformer in parallel with the return capacitor, can be very different and the times of recurring blockage of scanning switches and cutting each followed by half an oscillation period of the oscillating circuits can be out of phase with respect to each other.

The change in this relative phase shift or this delay interval gives rise to a variation of the power supplied, and therefore, the voltage across the reservoir capacitor. This fact is used for the regulation of this voltage supplying tank, in particular, the output stage and on which, on the multibibrateurs hand, the courz of the waveform of the scanning-line current sawtooth and, on the other hand, the very high voltage to the cathode ray tube.

For predetermined relative directions of said two windings of the line transformer, the energy transfer increases in one direction, when the phase difference becomes smaller multivibraters that corresponding to a zero transfer, and in the other direction, when becomes greater.

This implies, firstly, that the reversal of the direction of one xours the windings makes it possible to reverse the direction of energy transfer and hence, the variation of the phase delay and, hand, the circuit is reversible so that if one combines the terminals of the storage capacitor to those of a DC voltage source, the scanning circuit can supply energy in a controlled manner to the cutting circuit, if one replaces the power source by a filter capacitor connected to a load in parallel.

From the foregoing, it follows that to obtain a regulation of the voltage across the reservoir capacitor, it is necessary to control the opening of the cut-off switch with a delay with respect to multtivibrateurs of the scanning switch which is variable according to this reservoir voltage or a voltage dependent thereof such that one of the amplitudes of the return pulse line. It has many known circuits for varying the delay of a pulse on a transition leading or trailing of output relative to an input pulse or transition on the basis of a DC voltage, called generators delay, such as in particular monostable tipping type differential amplifier coupling emitters which a bias voltage of the base or the collector varies, or a saw-tooth generator triggered by the input waveform and feeding a voltage comparator, where is the threshold voltage of the comparator, or the slope of the sawtooth is changed in accordance with a voltage multivibraheurs from the reservoir voltage.

In the switching power supply device according multvibrateurs the preamble, the cutting inductance is no longer constituted by the single second winding of the line transformer, but includes an inductor choke coil in series with said second winding called “d ‘food”.

According to the invention, the value of this coil several millihenries is selected so as to make that of the cutting inductance which is composed of the leakage inductance of the power winding and that of the coil in series, substantially equal to or greater than three times that of the deflection coils back into the power winding circuit by the line transformer.

This coil is an integral part of the cutting inductance and, therefore, the resonant circuit comprising the tuning capacitor. The inductance reduced by the line transformer in the switching circuit is substantially equal to the inductance of the line-deflection coil multiplied by the square of the transformation ratio between the first and second windings of the transformer.

The measure according to the invention allows good separation between circuits on cuttings and scanning. The switching transistor is controlled by a control circuit fed by pulses return line from an auxiliary winding of the line transformer, which triggers a variable delay generator and of which a rectified peak amplitude variation of the delay control. According to a preferred embodiment of the invention, the second bidirectional switch comprising switching transistor which is controlled at its base by means of an improved control circuit, powered by the voltage rectified and stabilized network and which comprises an astable multivibrareurs operating to start independently to allow the supply of the entire scan-line circuit from the power capacitor or tank which is charged by a current due to switching of current induced in the first winding of the transformer -line and rectified by the diode in anti-parallel with the scanning transistor.

Upon start-up of the oscillator line supplied by the voltage tank, the outlet line stage provides the auxiliary winding of the line transformer of the flyback pulses which trigger the variable delay generator and whose rectified amplitude provides a control voltage to the generator.

These pulses can also provide synchronization of the multivibrator prior to regulation by variation of the phase shift. The invention will be better understood and other characteristics and advantages appear from the following description given by way of example, and the appended thereto, wherein: Figure 1 schematically shows a switching power supply device of the output stage 30 of scan line according to the invention having a galvanic isolation between the AC network feeds a rectifier 5, the output voltage is cut.

This winding 21 of line transformer 20 whose primary winding is usually connected in parallel with the coils of the line deflection courrs the circuit of the output stage 30 of the scan line to provide via secondary windings of the voltage supply, in particular cathode ray tube will be called in the following power winding, because the transfer of energy between the chopper circuit 10 and the output stage 30 will be conducted through it.

The switch 15 is connected in parallel with a capacitor 13 and is connected in series with the inductor 16 coil 14 and power winding 21 in series between the output terminals 6 and 7 of the DC voltage source 5. This capacitor 13 is, due to its low capacity compared to that of the smoothing capacitor 4, with the inductor 16, a resonant circuit oscillating parallel at the opening of the electronic switch 15 by blocking the switching transistor 11 by means of a control signal applied to its base.


It should be noted that the use of a bidirectional switch with unidirectional control comprising a led transistor and a diode, mounted to cohrs in opposite directions and connected in series with an inductor constituted by the winding of a transformer and parallel with a capacitor ensuring the agreement of the inductance at the opening of the cut-off switch is known from dE-B The transistor switch 11 is met here by its lew to one of the terminals of the inductor 16 whose other terminal is connected to the positive terminal 6 of the source 5 supplying the voltage VA continues to feed, by multivibrateurd emitter to 7 the negative terminal of the source 5 which constitutes a ground, or so-called hot primary 8, connected to the AC mains, but insulated from the TV The base of transistor 11 is controlled by means of rectangular signals provided by a control mmultivibrateurs 40, described later, so as to be alternately saturated and blocked.

The control circuit 40 is, for example, powered by an auxiliary winding 25 of transformer 20, providing signals whose peak-to-peak is proportional to the peak amplitude of the return pulse multicibrateurs. This peak amplitude is a function of transfer of the chopper circuit 10 to the energy output stage 30 of the scan-line which is secured to the other winding 22 of the transformer It will be noted here that the switching circuit multivibrtaeurs similar to a scanning-line output stage transistor, vector and the switching transistor 11 is selected to withstand high voltages collector-emitter about Vthe diode 12 to withstand the same reverse voltage during the opening of the switch It is also noted that the inductance of the choke 14 may be provided in part according to the invention, or in full, according to FR-Aby the leakage inductance of the winding 21 of power transformer The output stage of the scanning line 30 arranged in conventional manner, includes horizontal deflection coils 31 mounted in parallel and connected by one of their terminals to a first capacitor 32, said “go” or “d ‘ S effect “, which feeds the go during the scan.

The coil series circuit 31 and the capacitor to go 32 is joined in. The other terminal of the winding 22 is connected to one terminal of a third capacitor 33 of high capacity, the other terminal is connected to the junction of deflection coil 31, return capacitor 34, the anode of the second diode 35 and the emitter of the second transistor 36, which is also joined to the body 39 of the chassis of the television receiver, known as “cold” ground because it is isolated from the AC power supply network.

It is the terminals of the third capacitor 33 as the DC voltage is obtained supplying this stage, the value of which determines, on one hand, the peak-to-peak scan-line current in the form of teeth -de-saw and, on the other hand, the amplitude of the flyback voltage pulse which, rectified after processing, provides the high-voltage polarizing the anode of the cathode ray tube not shown here. The second transistor muptivibrateurs, also of switching is controlled by rectangular signals supplied to input terminals 37 and 38 of the stage 30, respectively connected at its base and its emitter by a driver not shown and called “driver” in the Anglo-American literature so as to render the blocked alternately, during the return scan, and saturated, during the second part of the outward scan.

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In conventional scanning-line circuit transistor, a DC voltage source is generally fed either directly to terminal of the coil 22, an intermediate outlet thereof through a diode see publications FR-A In the circuit of Figure mutlivibrateurs is multivibrzteurs AC electrical energy transmitted by the switching circuit 10 through the windings 21 and 22 of transformer 20 which charge capacitor 33 as IF provides a regulated supply voltage to the output stage During periods of the outward scan line, when the second bidirectional switch 35, 36 of the output stage of the scan 30 is closed conductiveckurs terminals of the winding 22 of the the transformer 20 are joined directly to those of the capacitor 33 which therefore receive power supplied from the chopper circuit In Figure 1, the line transformer 20 comprises, moreover, a very high voltage winding multivibraheurs, one terminal can be connected to earth 39 or terminal of the coil 22 and the multivibrateufs terminal is joined to the multivibrageurs of the very high-voltage rectifying circuit or the voltage multiplier not shown in a conventional manner, and an auxiliary winding 24 which can be used to feed either a low voltage rectifier assembly, a corus charge controller or the filament of the cathode ray tube not shown.

These secondary windings 23, 24 receive their energy primarily from multivibratsurs output stage of the scanning-line circuit through the coil 22 of the transformer 20, that is to say the pulses of line return, lfs coupling between the windings 22, 23 and 24 will be as tight as possible.

Figures 2 and 3, the diagram A shows the waveform teeth saw-scanning current i 3 courw in the coils 31 of the horizontal deflector. B shows the waveform of the voltage v ZZO t at terminal of the winding 22, which is also that across the second switch 35, The diagram C is in the form of wave voltage v 21 t across the power winding 21 when the leakage inductance is negligible, it is obtained by processing the alternating component of the voltage v t.

The diagram D shows the waveform of the voltage v 19 t across the first switch 15 of the switching circuit 10, that is to say between the juncture 19 thereof with the inductor 16 and the primary mass 8 and the diagram e shows dashed the current i 16 t in the inductor 16, when the output stage 30 is not controlled and in full line 21 the current i t resulting from the superposition in the winding 21 of the current i 16 t to that induced by the coil 22 when the output stage 30 is on.

Conversely, the current in the winding 22 of the transformer 20 results from the superposition of the current induced by the winding 21 the current produced by closure of the multkvibrateurs switch 35, 36, 31 analogous to i t of the diagram A.

The operation of the output stage 30 of the scan-line vector as soon as the power supply capacitors 33 and 32 are loaded to move to a DC voltage V with a number of cutting cycles, autonomous startup, during which the negative half of the chopped voltage waveform recovered by the recovery diode During the intervals of the scanning go t A, where the switch 35, 36 is closed at time t 1 at the instant t a, the current i 31 see A of the deflector varies substantially linearly between the values negative peak at t 1 and positive at t 3 with a zero crossing at time t 2, when the current i 31 passes from the diode 35 to the transistor 36 to drive previously polarized.

This corresponds to a voltage v 22o substantially zero see B at the terminals of the switch 35, The average value of the voltage waveform V t to terminal is equal to the DC supply voltage V across the power supply capacitors 33 and move or effect S The respective amplitudes of peak-to-peak current i 31 t hence the width of the excursion of the beam scanning lex screen and the voltage V t hence the THT depend on the value multivirbateurs the V direct voltage which feeds the output stage of the horizontal scanner 30 and which in most switching power supplies of the prior art, is regulated and stabilized by modulating the duration of the saturated state the duty ratio of cpurs transistor of cutting 11 as a function of the amplitude of the flyback pulse taken from an auxiliary winding of the line transformer 20 and therefore the voltage across the capacitor 33 and curs the voltage rectified and filtered network.

In this case, the less t s of the saturated state of the switching transistor 11 and the conductive state of the diode 12 and, therefore, the ratio of this length to that of the full cycle line period T H or the t B of the locked state, are constant and chosen so as to make the peak amplitude of the voltage multivibrateure 19 v, applied multivinrateurs the collector of transistor 11 during the blocking interval t a, substantially less its voltage collector-emitter breakdown in the locked state V CEX which can now exceed volts.

Then, the capacitor 13 discharges through the inductor 16 also oscillatably until, at time t 7, the voltage v 19 reaches a zero value corresponding to a minimum value, that is, negative maximum multivibrteurs, 16 of the current i t whose absolute value is slightly less than the maximum positive value i 16 t 6.

The difference between the peak values 16 i t 6 and 16 i t 7 in absolute be explained, firstly, by the ohmic losses in the circuit lrs and, secondly, by the transfer of energy between the latter and, mainly, the output stage When the oscillatory voltage v 19 t slightly exceeded the value zero to negative values, the diode 12 begins to conduct so as to join terminal 19 to ground and to generate in the inductor 16 a current i 16 t increases linearly from its maximum negative value i 16 t 7 to a zero value when the transistor 11, mu,tivibrateurs biased to be saturated, resumed for it to reach, at time t mulltivibrateurs, again its value maximum positive time t 6.


It is noted here that the average value of the voltage waveform multivobrateurs v 19 to terminal 19 is equal to the supply voltage VA between the terminals 6 and 7 of the filter capacitor 4 of the rectifier circuit 5. Comme la tension continue V aux bornes du condensateur 33 est fonction de l’inductance. As the DC voltage V across the capacitor 33 is a function of inductance.

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The transformer 20 may be formed to have a little tight coupling between the windings 21 and 22, the inductance “inductive” is then composed of the L 14 the throttle 14 and the leakage inductance L 21 suitable for winding It is therefore advantageous, when using a core magnetic circuit in rectangular ferrite frame-shapedplacing the windings 22, 23 and on one of the legs thereof, and the coil 21 and possibly coil 25, on the other, which also contributes to a good isolation between the primary and secondary masses 8 It can be assumed that, from the viewpoint of transfer of the energy of the switching circuit 10 to the output stage 30, the winding 21 is traversed by the current i 21 of the current i multicibrateurs 18 of triangular shape and winding current 22 induced in the shape of sawtooth, superimposed and the voltage V 21 appears at its terminals, as shown in the diagrams C of figures 2 and 3, is substantially similar to that V at the terminals of the ‘scan switch 35, 36 but with a zero mean value.

The energy transmitted by the transformer 20 will be approximately equal to the product of the voltage V 21 t and the current i 21 t multiplied by the cosine of the phase angle p, if the fundamental waves are considered at the line frequency 15, Hz. This is also true for each of the harmonics of the current waveforms 21 i t and voltage V 21 tif one develops in Fourier series. The energy transferred during each line period T H by the switching circuit 10 to the output stage 30 via the transformer 20 can therefore cry: This is sustainably possible that if the output stage 30 and therefore the capacitor 33 which is fed by a rectifier circuit, demonstrating the reversibility of the feeder according to the invention unlike conventional switching power supplies.

The regulation is performed by varying the phase of the opening of the switch 15 of the switching circuit 10 by the blocking of the transistor 11, relative to that courx the opening of the scan switch 36, 35 controlled by the line oscillator not shown which is generally controlled in frequency and phase to the synchronization-line pulse of the complex video signal. Such a variable phase courss is obtained here from the pulses return line drawn from one of the windings of the transformer 20 such that the winding 21 itself or, as illustrated in Figure 1, the auxiliary winding These pulses can trigger a flip-flop corus variable duration depending on the error voltage supplied by a comparator in the form of differential amplifier, whose one input receives a voltage corresponding to either the positive amplitude of 21 V t proportional to the voltage V 33 V at the terminals of the supply capacitor 33 of the output stage 30 or to the peak-to-peak pulse of flyback, that is mlutivibrateurs to THT, or a combination of these two criteria.

Note here that the power winding 21 may be connected between the terminal 6 of the capacitor 4 and the choke coil 14 in two opposite directions, so that the flyback pulse may appear on the junction of self 14 with opposite polarities which shows two phase Actions on the voltage V 21 t with respect to the current i 21 t of this winding In Figure 4, there is shown a partial block diagram without ignition device of a simple embodiment of the control circuit 40 which controls the blocking of the transistor 11 of the chopper circuit 10 with a variable delay with respect to the return pulse line, according to the negative peak amplitude of the signal v 25 t lee by the auxiliary winding 25 of the transformer This multivibrateurz input supplies, through a first lezthe trigger input of a first monostable rocker 41, variable length producing at its output in response to leading edge of the flyback pulse, a rectangular signal whose duration varies according to a DC voltage applied to its control input of duration.

The rockers monostable with variable pulse duration depending on a DC voltage are known and an example embodiment is described, for example, in the publication FR-A This voltage continues to control the duration the pulse is obtained with the aid of a rectifier assembly 42 also fed by the first input and having a second diode connected for.

This circuit 44 includes a resistor and a Zener diode connected in series between the input and the primary mass 8 and provides, in using a resistive divider circuitoptionally adjustable, connected in parallel with the Zener diodethe reference voltage at the input of the comparator The rising edges of the pulses supplied by the output of the rocker 41 substantially coincident with those pulses flyback, their descent or falling edges that occur with variable delays with respect to the first are used to trigger, possibly through an inverter stage, a second flip-flop 45 whose output feeds the base of chopper transistor 11 to block it.

Figure 5 is a preferred embodiment of the block diagram of a control circuit 40 of Figure 1 which controls the transistor 11 of the chopper circuit 10, according to the invention.

In Figure 5, the control circuit 40 has an input connected to the one terminal of the auxiliary winding 25 of line transformer 20 which feeds lez parallel a first control input of a stage phase shifter 46, the input of a control stage 47 and possibly the input of cuors synchronization circuit The output of stage phase shifter 46 feeds a first trigger input of an astable multivibrator 49 whose second clock input is fed by the output of the synchronization circuit The synchronization circuit 49, whose operation will be described further, is only required if the frequency of self-oscillation of the multivibrator 48 is greater than the line frequency.

Otherwise, the multivibrator 48 is conventionally synchronized by the trigger pulse applied to its input The output of the astable multivibrator 48 feeds the input of a driver or controller 50 consisting of an amplifier. The output cour the control stage 50 called a “driver” in the Anglo-American literatureconnected courw the output of the control mutlivibrateurs 40, feeds the base of the switching transistor 11 of the chopper circuit The auxiliary winding 25 supplies to the input of the voltage waveform control circuit comprising the flyback pulses on line with a negative polarity, for example, similar to that shown in the diagrams C of Figures 2 and 3.

These flyback pulses applied to the input of the stage phase shifter 46 or delay generator, controls the triggering of a signal generator multicibrateurs a voltage-tooth-shaped positive saw which is applied to one of the inputs of a voltage comparator stage whose other input is supplied with a fixed reference voltage and that switches its “high” state to its “low” state when the amplitude of the voltage tooth saw exceeds the value of the reference voltage.

The control muktivibrateurs 47 also receives the pulses of line return, the recovering and transmits to the control input of multivibrateurd phase shifter 46 a floor should sign shaped current for changing the slope of the saw tooth function of the amplitude of the flyback pulse which is a function of the DC multivibrayeurs at the terminals of the supply capacitor 33 Figure 1 of the output stage Accordingly, the slope of the sawtooth must decrease with increasing amplitude of the pulse return.

The astable multivibrator 48 is, preferably, synchronized in frequency with the output stage of the scanning line 30 in a manner that will be explained later, with the synchronizing circuit 49 which feeds its synchronization input To allow starting of the chopper circuit 10 before the start of the scanning-line circuit and in particular of its output stage 30, the astable multivibrator 48 must oscillate independently, and stage 50 must amplify the signal substantially square it provides.

For this purpose, an autonomous multjvibrateurs supply voltage source 51 is connected to terminals 1, 2 alimenation the AC network and tensions it provides supply the power supply terminalsand of the control circuit This start and subsequent regulation will be explained in more detail in the following.