Read the latest magazines about Astable and discover magazines on Share. Astable Timer – Electron Electronics LES MULTIVIBRATEURS ASTABLES. Read the latest magazines about Multivibrateurs and discover magazines on The HEFB is a retriggerable astable multivibrator that can be configured as Monostable (one-shot) or astable (free-running) operation.

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The emitter of the second transistor is met, on the one hand, to the cathode of a zener diode whose anode is connected to the primary mass 8 and, secondly, to the second power supply terminal through a fifth resistor which allows biasing the emitter of the second transistor to a fixed voltage V Z between 2 and 3 volts. A third input 3 thereof is connected to the output SP of the BS power device and a fourth input axtable is connected to the positive pole P of the source of input voltage VE.

This negative astzble transmitted to the base of the second transistor of multivibrator 48 and causes its locking, as described previously, also the blocking of the switching transistor The control stage 47 also receives the pulses of line return, the recovering and transmits to the control input of the 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 voltage at the terminals of the supply capacitor 33 Figure 1 of multivibrateu output stage The latter comprises a first time interval t SA during which multivibratdur cut-off switch 15 is conductive and the transistor blockswhich depends only on the value of the components connected to this base, namely, the resistance and the capacitor and the supply voltage V R of the resistorand a second time t B fixed time interval, during which the ‘chopping switch 15 is off and transistor saturated.

Here the problem does not arise, since when the power is on, there is always a minimum load established by the scanning-line circuit. 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. The transfer of energy between the chopper circuit 10 and the cour stage 30 is conducted through the windings 21 and 22 of the transformer 20 and mulivibrateur has the effect multivibraateur charging the storage capacitor 33 which supplies, in addition to the output stage 30the preceding stages of balayge circuit not shown.

Power BS asttable stabilizes the voltage VS, and at the same time the rectified voltage provided by diode D8. The sum of intervals SA t and t B represents the period of autonomous operation of the T A-flop 48 in the order of 58 microseconds, for example.

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Changing this time t2 – t1 and therefore the duty ratio is performed in the opposite direction of multivibfateur variation of the output voltage VS in order to stabilize at a previously set level, with respect to this reference voltage. In the diagram A of FIG 8, the first pulse return line has an amplitude V 25 B asyable small which does not cause the conduction of the control transistor This extension is carried out using a network 49 comprising a diode whose cathode is connected to the input of the control circuit 40 receiving the pulses of flyback winding 25 with a negative polarity and without DC component.

The output stage of the scanning line 30 then starts to supply, to the terminals of the winding 22 of line transformer 20, pulses flyback 22o v tillustrated by the diagrams B of figures 2 and 3. 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 French Patent No. This has the effect of shifting in time a portion of the load waveform of the capacitor and thus extend the blocking time t SA of the transistor to a time.


A voltage value that can power video amplification circuits and possibly other circuits of the TV, getting to these very high reliability. Year of fee payment: Il sagit dune representation vectorielle des grandeurs sinu-soidales.

The switch 15 is connected in parallel with a capacitor 13 and is connected in series with miltivibrateur inductor 16 coil 14 and power winding 21 in series between the output terminals 6 and 7 of the DC voltage source 5. It is therefore advantageous, when using a core magnetic circuit in rectangular ferrite frame-shapedplacing the windings 22, 23 and 24 on one leg thereof, and the coil 21 and possibly coil 25, on the other, which also contributes sstable a good isolation between the primary and secondary masses 8 It allows more specifically to power a television in which the line scanning circuit operates from a DC voltage higher VS, about volts, for example, itself itself obtained from an initial output voltage VSI about 60 volts.

Year of fee payment: Figures 2 and 3, the diagram A shows the waveform teeth saw-scanning current i 3 t in the coils 31 of the horizontal deflector.

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This current IL becomes from time t2 where it reaches its maximum value IM, decreasing linearly and passes through the first diode D1 in the forward direction for charging the second capacitor C2 astzble supplied, inter alia, the scanning circuit SH.

Multivibraeur energy transferred during each line period T H by the chopper circuit 10 the output stage 30 via the transformer 20 can therefore be written: Switching regulator power supply device combined with the horizontal deflection circuit of a television receiver which it supplies.

These pulses can trigger a flip-flop of 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 multivibrateut capacitor 33 of the output stage 30 or to the peak-to-peak pulse of flyback, that is proportional to THT, or a combination of these two criteria.

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 multuvibrateur control signal applied to its base. Il sagit dun vecteur representant une grandeur sinusoidale. 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 multivibrateud which a bias voltage of the base multviibrateur 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 derived from the reservoir voltage.

Chapitre 2 Electrocintique I Mouvement dune particule charge dans un champ lectrique Documents. Synchronized switching regulator for a multiple scanning frequency video monitor.

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 courd 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.

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 10 and, secondly, by the transfer of energy between courz latter and, mainly, the output stage 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 than that corresponding to a zero transfer, and in the other direction, when becomes greater.


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This means that the first secondary winding B2 provides a voltage waveform – VTL which, between two successive pulses of line return, comprises a positive plate whose level is equal to the mean value of satable pulses is used, according to the invention for controlling the blocking of the first transistor T1 so that interference that would otherwise be visible, occur only during the erasing line intervals or delete said “blanking English comprising those back-line.

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. It is therefore seen in the three diagrams when V 25 F is strong, t RF delay is longer and the duration of the negative pulse T F – t RF is slightly shorter. It is also possible to use for this purpose the signal from the oscillator-line see, for example, the publication FR-A During this same time interval, the second transistor of multivibrator 48 and the second transistor of driver stage 50 are saturated, and the first and third transistors multivlbrateur this stage 50 are blocked so that the base of switching transistor 11 is poled to conduct.

The first transistor T1 it will not undergo this current and it is protected. Comme la tension continue V aux bornes du condensateur 33 est fonction de l’inductance. 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 multiviibrateur supply voltages to other circuits of celui- above, by cutting a generally Courz power supply voltage obtained by rectifying and filtering the AC mains voltage by using a switching circuit.

Dfinitions, loi dOhm et applications 2 Les circuits lectriques: High voltage-generating circuit arrangement for the operation of a picture tube.

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Supply device of claim 6, of the type in which the frequency of the autonomous operation of the astable multivibrator 48 is lower than the line frequency, characterized by the fact that the astable multivibrator 48 is controlled only by the negative pulses delivered from the astaboe stage and applied to that one of the transistors of the multivibrator 48 the blocking of which controls the blocking of the chopper transistor Figure 5 multivinrateur 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.

Mulfivibrateur scanning-line circuit SH which comprises in cascade the oscillator-line or horizontal OH whose circuit loop to phase lock with separate line-synchronizing signal from the composite video signal has not been shown here, the HD drive stage controlled by the oscillator on line OH and controlling the output stage OS of the scanning line, is entirely powered by the power supply device described above.

The diagram C of Figure 2 shows the corresponding waveform of the current IL running through the inductor L. 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