EP0012634B1 - Voltage regulator device, in particular for portable television receiver - Google Patents

Description

The present invention relates to a voltage regulating device with protection against overloads and short-circuits for portable television receivers, in particular of the type supplied by a low DC voltage coming either from a storage battery or from a battery. rectifier assembly preceded by a transformer and followed by a filter to eliminate snoring.

Television receivers, which can be supplied with electrical energy by batteries providing low continuous voltages, pose the problem of protection against short circuits and overloads and of obtaining a minimum waste voltage between the collector and the emitter of the series regulation transistor (ballast).

The series voltage regulator of the type in which a transistor or the output stage of a circuit comprising several transistors directly coupled in cascade, of the type of a so-called multiple "Darlington" circuit or of a pair of complementary transistors, is inserted in series in the DC power supply line between the primary source (battery or filtered rectifier) and the load, forming a common collector type arrangement whose control electrode (base) is supplied by a control voltage from a regulation loop provided with a voltage comparator which compares a fraction of the output voltage across the load to a stabilized reference voltage (collected across a Zener diode). Circuits of this type are well known and described, for example, in the work of MILLMAN and HALKIAS entitled "ELECTRONIC DEVICES AND CIRCUITS", published by McGRAW-HILL Book CO. in 1967 or in PASCOE's book "FUNDAMENTALS OF SOLID-STATE ELECTRONICS", published by JOHN WILEY & SONS in 1976.

Such a circuit must include a device for protecting the series regulation transistor against overloads and short-circuits on the load side, which would cause collector-emitter currents and voltages such that its dissipation would exceed the permitted limits defined by the safety area (called "safe operating area" or "SOAR" in Anglo-American literature) causing its destruction. In the prior art, as mentioned in the aforementioned works, a fuse was used in series in the supply line of the circuit which tripped (by melting), when the current exceeded the calibrated value and whose speed could prove to be insufficient. . There is also described a current limiting circuit in which a series resistor R _s is inserted between the emitter of the regulation transistor and the load, the base of this transistor is joined at the junction of this resistor with the load by two or several diodes in series oriented in the same direction as its base-emitter junction. When the sum of the base-emitter voltage V _BE and the voltage drop R _S .I _L caused at the terminals of the resistance R _s by the current in the load I _L , i.e. (V _BE + R _S .I _L ), is sufficient to polarize the diodes positively, they start to drive so as to reduce the base current I _B of the transistor and, consequently, also its emitter current I _E supplying the load. However, this series resistance adds an additional voltage drop to the waste voltage between the collector and the transmitter at nominal power, which is already too large for battery-powered devices.

A voltage regulator corresponding substantially to the preamble of claim 1 is already known from the article by SCIDMORE entitled "JUNCTION DIODE REGULATES LOW-VOLTAGE SUPPLY", on pages 55 and 56 in the American review "ELECTRONICS", N °. 27 of volume 37, dated October 19, 1964, wherein a first tran _- sistor NPN type ballast is connected in common collector between the input and the positive output of the regulator, whose collector is joined to the base, a on the one hand, by a first resistor and, on the other hand, by the emitter-collector path of a second NPN type transistor in series with a diode. The base of the second transistor is connected, on the one hand, by a second resistor to the positive input of the regulator and, on the other hand, to the collector of a third comparator transistor mounted as a common base, the base of which is connected at the junction of a third resistor and a voltage stabilizer assembly composed of two diodes in series whose free terminals are respectively connected to the output terminals of the regulator and whose transmitter is connected to the midpoint of a divider of resistive voltage connected between these same output terminals.

The serial regulation circuit, object of the present invention, makes it possible to provide protection against overloads and short-circuits to the regulation transistor, a limitation of its operation to the safety area (SOAR), the increase and the maintenance constant gain of the circuit with open control loop and reduce its collector-emitter waste voltage V _CE ,

The subject of the invention is a DC voltage regulating device of the type comprising a regulating element which comprises a first transistor mounted as a common collector, inserted in series between an input terminal and an output terminal of the same polarity and whose impedance is controlled using an amplifier-comparator comprising a third transistor whose emitter is polarized using a diode Zener at a constant reference voltage and whose base receives a fraction of the device output voltage, in order to provide a collector current which is a function of the difference between the reference voltage and this fraction and which supplies the input of this regulating element so that the voltage drop between these terminals varies so as to compensate for variations in the input voltage, the regulating element further comprising a second transistor of a type complementary to the first, including the emitter is connected to the collector thereof, whose collector is connected to the base of the first and whose base is connected to the collector of the third transistor, and a first resistor uniting the collector and the base of the first transistor and making it possible to ensure its start-up conduction and limit its maximum transmitter current in the event of a short circuit.

According to the invention, the DC voltage regulator further comprises a second resistor joining the collector of the first transistor to the emitter of the second and making it possible to limit the collector current thereof which constitutes the basic current of the first transistor , so that the power dissipated by the first transistor, equal to the product of its collector-emitter overload voltage and its collector current limited using its base current, does not exceed a predetermined value, the emitter of the third transistor being connected to that of the first via the Zener diode and to the other output terminal of the device through a resistor.

• -la figure 1 montre un schéma de principe d'un circuit de régulation de tension de la technique antérieure, utilisable avec une batterie d'accumulateurs, par exemple;
• -la figure 2 est un schéma de principe partiel montrant une première modification du circuit de la figure 1; et
• -la figure 3 est un schéma de principe du mode de réalisaiton préféré du circuit de régulation de tension suivant l'invention, utilisé dans un récepteur de télévision portable pouvant être alimenté par batterie ou redresseur.

The invention will be better understood and other of its characteristics and advantages will appear from the following description and the attached drawings relating thereto, given by way of example, in which:

• FIG. 1 shows a block diagram of a voltage regulation circuit of the prior art, usable with an accumulator battery, for example;
• FIG 2 is a partial block diagram showing a first modification of the circuit of Figure 1; and
• FIG. 3 is a block diagram of the preferred embodiment of the voltage regulation circuit according to the invention, used in a portable television receiver which can be powered by battery or rectifier.

In all the figures, the same elements have been designated by the same number of references.

In Figure 1 there is shown the block diagram of a voltage regulator device 10 of the prior art (conventional) of the type using the series regulation using a pair of complementary transistors.

This regulation circuit 10 comprises a first input terminal 1 to be connected to the positive pole of a non-stabilized DC voltage source, the negative pole of which is connected to a second input terminal 2 of this circuit. This voltage source can be constituted either by a battery 5 of accumulators or batteries, rechargeable or not, or by a rectifier assembly 6 supplied by a step-down transformer 7 whose secondary winding supplies a diode 8 connected in series with a filtering capacitor 9 whose armatures constitute the poles of the source. The single-wave rectifier illustrated can obviously be replaced by a two-wave rectifier with two diodes or with four diodes in a bridge and the filter can also include one or more inductors and additional capacitors to obtain better attenuation of snoring. The switching of the two sources 5 and 6 is carried out using an inverter 21, the movable contact of which is connected to terminal 1.

The regulation circuit 10 also comprises two output terminals 3 and 4 supplying a stabilized direct voltage V ₃₄ , the first output terminal 3 being joined to the first input terminal 1 by means of a regulation element 100 to semiconductor which here comprises an assembly of two complementary transistors with direct coupling generally called "complementary pair" (a pair of transistors of the same type with direct emitter-base coupling being called "Darlington" circuit).

The first transistor 11 is of the NPN type and the second transistor 12 is of the PNP type; they are both transistors of power. The collector of the first transistor 11 and the emitter of the second transistor 12 are connected together to the first input terminal 1 of the regulation circuit 10. The collector of the second transistor. 12 is connected to the base of the first transistor 11 1, the emitter of which is connected to the first output terminal 3. There is therefore a power amplifier with two stages in cascade, including that comprising the PNP transistor 12 mounted as a common emitter controls the one comprising the NPN transistor 11 mounted as a common collector, which work together as a single NPN transistor, mounted as a common collector and whose direct current transfer ratio between the base and the collector connected to the transmitter h _FE or the gain of direct current A would be equal to the product of those of these two transistors.

The base of the second transistor 12 is connected to the collector of a third transistor 13 of the NPN type which constitutes a voltage comparator stage, the emitter of which is connected to the common point of a series arrangement of a Zener diode 15 and of a resistor 14, connected between the output terminals 3 and 4 of the circuit 10 and the base of which is supplied by an adjustable fraction of the output voltage V ₃₄ collected on the cursor of a potentiometer 17 forming with two resistors 16 and 18, respectively connected to its terminals a series circuit connected between the output terminals 3 and 4. In the circuit 10 of FIG. 1, the Zener diode 15 is connected between the first output terminal 3 and the emitter of the third transistor 13, and the resistor 14 between the latter and the second output terminal 4 in order to polarize the emitter at a voltage V _E fixed with respect to the first terminal (V _E = V ₃ - V _I , where V _Z is the Zener voltage of diode 15). In conventional transistor control circuits, in particular those of the aforementioned works, the Zener diode 15 is generally connected between the emitter of the transistor 13 and the second input 2 and output 4 terminals and it is then possible, optionally, either to omit the resistor 14, or connect it between this emitter and the first input terminal 1. Without this resistor 14, the Zener diode 15 remains blocked until the voltage at its terminals exceeds its Zener voltage V _Z , the comparator transistor 13 remaining blocked until then. If the resistor 14 joins the emitter to the second terminals 2 and 4, the transistor 13 will conduct as soon as its base-emitter voltage has exceeded 0.7 volts by bringing the second transistor 12 to the conduction. As soon as the Zener diode 15 starts, the potential of the transmitter V _E is fixed relative to one of the output terminals 3 or 4, while that of the base V _B varies in proportion to the variation of the voltage of output V ₃₄ . A base-emitter voltage V _BE13 of the third transistor 13 is then obtained equal to the difference between these potentials, that is to say at V _B13 ―V _E13 , so as to generate in this transistor a collector current I _C13 proportional to this difference.

The collector current I _C13 constitutes the base current IB ₁₂ of the second transistor 12 whose collector current IC ₁₂ in turn constitutes the base current IB ₁₁ of the first 11 which then forms a variable impedance inserted between the first input terminals 1 and output 3 acting so as to compensate, by the voltage drop at these terminals, for variations in the input voltage V ₁₂ supplying the circuit 10.

A resistor 19 capable of dissipating high power (of the order of 10 watts) is connected here between the collector and the emitter of the first transistor 11, that is to say between the first input 1 and output terminals. 3, in series with a fast blow (thermal) protection fuse 20.

This resistance is used to reduce the dissipation of the first transistor 11 by conducting a bypass part of the direct current supplying the load 22 and also at the start of the regulation circuit. This resistor 19 however has a negative effect on the regulation (limitation of the range of admissible variations of the input voltage) and directly transmits the humming voltage (residual ripple of the rectifier) to the load 22 which then requires a filtering capacitor high capacity, can be bulky and heavy.

The circuit of FIG. 1 has other disadvantages, such as: the impossibility of saturating the first transistor 11 so that the minimum value of the waste voltage between its emitter and its collector, V _{CELL min} = V _{CE12 sat} ⁺ V _{BE11 '} can never be less than 1 volt; reducing the gain of the control loop for control voltages (V _CE11 ) less than 2 volts, due to the fact that the second transistor 12 then approaches saturation; and the lack of effective protection against short circuits and overloads.

In Figure 2, there is shown a modification of the regulating element 100 of the circuit of Figure 1 to eliminate the starting resistor 19 and also provide effective protection against short circuits and overloads.

The replacement of the starting resistor 19 is obtained using a resistor 101 positively biasing the base of the transistor 11 when the circuit 10 starts.

When the circuit 10 is energized, a basic starting current I _{B11D is} established through the basic resistance 101 which is equal to (V _CE11 ―V _BE11 ) / R ₁₀₁ , where V _CE11 is initially equal to the input voltage V ₁₂ supplied by the source 5 or 6 and V _BE11 is initially zero. If V ₁₂ = 16 V is selected and R ₁₀₁ = 4.7 kQ is chosen, a basic starting current I _B11D of 3.4 mA is obtained. This base current I _B11D causes an emitter current I _E11D in the first transistor 11 which, for a typical current gain β ₁₁ = 40, gives a starting current I _E11D = 130 mA approximately. In the absence of a short circuit in the emitter circuit of the first transistor 11, the current I _E11D will charge the filtering and decoupling capacitors of the load circuit 22 (not shown in FIG. 1) at a voltage slightly greater than approximately 2 volts . As soon as the comparator transistor 13 (Figure 1), whose emitter joined by the resistor 14 to the second terminals 2 and 4 of the circuit 10, is at zero potential before the ignition of the Zener diode 15 by an output voltage exceeding its Zener voltage V _Z , receives a base-emitter voltage V _BE greater than about 0.7 volts, it will begin to conduct a collector current I _C13 by supplying a base current I _B12 = I _C13 to the second transistor 12. Consequently, the second transistor 12 provides a collector current I _C12 which will be added to the starting base current I _B11D = I ₁₀₁ passing through the base resistance 101. This will have the effect of increasing the current of I _B11 = I _C12 + I ₁₀₁ of the first transistor 11 and, consequently, also the emitter current I _E11 of the latter so as to increase the output voltage V ₃₄ of the circuit 10 (FIG. 1) until the aforementioned ignition of the Zener diode 15 which signifies establishment of regulation. A resistor 102 inserted in the emitter circuit of the second transistor 12, that is to say between the first input terminal 1 and the emitter thereof, has the effect of limiting the emitter currents I _E12 and collector I _C12 of the second transistor 11 by ensuring, on the one hand, a gradual starting of the regulated supply and, on the other hand, a protection in the event of overload (absence of a short-circuit) of the first transistor 11 by limiting its base current I _B11 and, therefore, its emitter current I _E11 .

To illustrate a case of overload of the regulator circuit 10, let us consider that the switch transistor of the horizontal scanning (see figure 3, element 37) in a television receiver 22 forming the load, remains conductive after the establishment of the supply voltage V ₃₄ therefore with the comparator transistor 13 already in operation. The voltage V ₃₄ will then be reduced to approximately 2 V, constituted by the sum of the collector-emitter saturation voltage of the transistor ³⁷ (V _{CE37 sat} ) and the direct anode-cathode voltage (V _F32 ) of the voltage step-up diode 31 or recovery series (called "booster" in Anglo-American literature).

ce qui donne pour

un courant I_B11M de 16 milliampères, d'où l'on calcule de courant émetteur de surcharge

The maximum current in the base I _B11M with the second saturated transistor can then be calculated as follows:

which gives for

an I _B11M current of 16 milliamps, from which we calculate the overload emitter current

This example represents the most unfavorable case of the overload of the first series regulation transistor 11. The power dissipated in this case will then be

These considerations also apply to the start of the regulator circuit 10, because for a non-frank short-circuit through semiconductor elements, the comparator transistor 13 starts to conduct for an output voltage V ₃₄ of the order of 2 V.

watts environ, qui est nettement inférieure à la dissipation en cas de surcharge P_Mç.When there is a short circuit between terminals 3 and 4 (V ₃₄ = 0) the process described above cannot take place because the base-emitter voltage V _EB13 of the comparator transistor 13 remains zero in the now blocked. The first transistor 11 then continues to conduct a so-called short-circuit current I _E11K which is equal to the starting emitter current I _E11D of 130 milliamps. Its dissipation in the event of a short circuit will then be equal to

watts approximately, which is much lower than the dissipation in the event of overload P _Mç .

By choosing for the first transistor 11, a power transistor NPN having a maximum collector-emitter voltage V _{CEO max} greater than the maximum input voltage V ₁₂ ^max, a maximum collector current I _{C max} equal to the maximum current consumed by the load 22 and a total admissible dissipation P _tot greater than or equal to the product of this maximum current with the difference between the maximum input voltage and the nominal output voltage, we are sure to operate, with a regulation circuit of this kind (element 100 of Figure 2), inside its safety area, even in the event of an overload or short circuit.

FIG. 3 schematically illustrates the preferred embodiment of a voltage regulating device 10 supplying a solid-state television receiver which constitutes the load 22 thereof.

A television receiver of this kind generally comprises a line-scanning circuit, the output stage 30 of which comprises a controlled bidirectional switch, formed by a switching transistor 38 and a parallel recovery diode 37, connected in parallel and oriented in a manner to drive in opposite directions. This output stage 30 further comprises, connected in parallel with the switch 37, 38, a series connection composed of the deflection coils 34 and of a capacitor 35, said to be "going" or "of effect S ", which supplies the deflection coils 34 during the forward scan periods and a return capacitor 36 forming with the coils 34 a parallel resonant circuit during the scan return periods where the switch is open and the there observe pulses of semi-sinusoidal voltage of high amplitude, which can be used to generate the very high voltage which must supply the cathode ray tube (not shown) and possibly other voltages, after their rectification. To this end, the common point of the collector of the transistor 38 and of the cathode of the diode 37 is connected to one of the terminals of the primary winding 320 of a transformer 32, called a line transformer, which comprises a secondary winding 322 very-high voltage supplying a very-high voltage rectifier 28 (not shown) and also other secondary windings, one of which 321 is used here as indicated below.

The other terminal of the primary winding 320 is connected, by means of a capacitor 33, called "reservoir" or "supply", to the first output terminal 3 of the regulation circuit 10 which is, on the other hand, connected to a bypass or intermediate socket of this primary winding 320 through a lifting diode (or series recovery) 31 which makes it possible to increase the supply voltage of the output stage 30 by charging the reservoir capacitor 33 for the return of the scan.

The secondary winding 321, one of the terminals of which is connected to the second terminal of output 4 of regulator 10, supplies by its other terminal a rectifier assembly comprising a rectifying diode 25 which rectifies the transformed return pulses and a filtering capacitor 26 connected between the cathode of diode 25 and the second output terminal 4 and charged by this diode 25. The number of turns of this secondary winding 321 and their direction of winding relative to that of the primary winding 320 is chosen so as to make appear at the terminals of the capacitor 26 a DC supply voltage V ₂₆ auxiliary, higher than the input voltage V ₁₂ of the regulator 10. The secondary winding 321, the diode 25 and the capacitor 26 therefore together form a source of auxiliary supply voltage. In the present case, an auxiliary voltage V ₂₆ of 26 volts has been chosen, when the regulator supplies its nominal voltage V ₃₄ of 10.8 volts and when the oscillator of the line-scanning circuit (not shown) is slaved to the frequency _F. synchronization-line pulses transmitted in the complex video signal. From which it appears that the auxiliary voltage V ₂₆ is equal to 2.4 times the regulated nominal voltage V ₃₄ . The line oscillator and the drive circuit (not shown) of the output stage 30 are also supplied by the regulation circuit 10.

If there is no overload or short circuit between the output terminals 3 and 4 of the voltage regulator circuit 10, the line-scanning circuit of the receiver starts up and the line oscillator controls the attack stage which in turn controls the output stage 30 as soon as the output tenion V ₃₄ of the circuit 10 reaches the value of approximately 6 volts with an emitter current I _E11 of the first transistor 11 of the order of 300 milliamps . The transformed and rectified return pulses then supply an auxiliary supply voltage V ₂₆ of 14.4 volts which is applied to an auxiliary supply input 27 of the regulation circuit 10. This auxiliary input 27 is connected to the transmitter of the second PNP transistor 12 via another emitting resistor 103 (a few hundred ohms). The auxiliary supply voltage V ₂₆ will then supply, through the other emitting resistor 103, an additional emitter current I ₁₀₃ = I _E12S of the second transistor 12, which will allow the regulation circuit 10 to work fully, because the emitter current I _E12 ⁼ I ₁₀₃ + I ₁₀₂ of the second transistor 12 is then limited and controlled only by its base current I _B12 which is constituted by the collector current I _C13 of the third comparator transistor 13. The auxiliary supply voltage V ₂₆ supplying, through the other emitting resistor 103, the emitter of the second transistor 13 makes it possible, from the start of the line-scanning circuit for an output voltage V ₃₄ of l '' order of 6 volts, a rapid rise in the output voltage V ₃₄ , while keeping below this threshold, i.e. in the event of an overload (2 V) or a short circuit (0 V ), the previously described protection of the first transistor 11.

It can easily be seen that for operation at the nominal output voltage V ₃₄ = 10.8 V with an input voltage V ₁₂ = 16 V and an auxiliary voltage V ₂₆ = 26 V, the current I ₁₀₁ supplying the base of the first transistor 11 from the first input terminal 1 is negligible compared to that provided by the collector of the second transistor 12. Consequently, the alternating component of the base current, which is caused by the humming voltage of the rectifier filtered will also be negligible.

The auxiliary supply voltage V ₂₆ makes it possible, on the other hand, to bring the first transistor 11 to saturation so as to minimize the waste voltage between its collector and its emitter, since it is this which supplies then the emitter current I _E12 of the second transistor 12 whose collector current I _C12 supplies the base of the first 11. The other emitter resistance 103 will therefore be calculated so as to obtain, with I _{B11 max} = I _C12 = 50 mA a voltage V _{E12 min} minimum at the emitter of the second 15 volt second transistor 12, hence R ₁₀₃ = (V ₂₆ - V _E12 ) / I _E12 will give 220 ohms. We then obtain a minimum emitter-collector voltage of the second transistor 12 VEC12 min = V _{E12 min} min - (V ₃₄ + V _BE11 ) of the order of 4 volts indicating that it will not saturate, so that the gain of open loop control circuit is not reduced for low input voltages V ₁₂ .

We can then regulate the output voltage V ₃₄ from 10.8 volts to an input voltage of 11.3 volts, because the collector-emitter waste voltage of the first 11 V _{CE11 min} transistor will then be 0.3 approximately volts instead of 2 volts with the conventional circuit (Figures 1 or 2).

• a) une protection contre les court-circuits,
• b) une protection contre les surcharges,
• c) le maintien du fonctionnement du transistor régulateur dans les limites de son aire de sécurité (SOAR),
• d) une augmentation et le maintien constant du gain à boucle de régulation ouverte, et
• e) l'extension de la limite inférieure de la gamme de régulation du fait de la réduction de la tension de déchet V_{CE11 min} en saturation, permettant de maintenir constante la largeur de l'image (l'amplitude du courant de balayage horizontal) jusqu'à une tension d'accumulateur de 11,3 volts (la tension nominale étant de 16 volts).

The preferred embodiment of the regulation circuit 10 combined with the line-scanning circuit of a television receiver which supplies it with an auxiliary supply voltage V ₂₁ greater than its input voltage V ₁₂ in the manner described above. above and illustrated in FIG. 3, makes it possible to simultaneously ensure:

• a) short circuit protection,
• b) overload protection,
• c) maintaining the operation of the regulating transistor within the limits of its safety area (SOAR),
• d) an increase and the constant maintenance of the gain with open regulation loop, and
• e) the extension of the lower limit of the regulation range due to the reduction of the waste voltage V _{CE11 min} in saturation, making it possible to keep the width of the image constant (the amplitude of the horizontal scanning current) up to a battery voltage of 11.3 volts (the nominal voltage is 16 volts).

The invention is also applied to any load circuit 22 comprising a switching power supply (called "switch mode power supply") or a DC-AC converter making it possible to have an auxiliary supply voltage greater than the supply voltage. voltage regulator device input.

Claims (3)

1. DC voltage regulator device of the type comprising a regulating member (100) comprising a first transistor (11) mounted in common collector and series-connected between a first input terminal (1) and a first output terminal (3) of the same polarity and the impedance of which is controlled by means of a comparator amplifier including a third transistor (13) the emitter of which is connected through a resistor (14) to the second terminals (2, 4) of the member (100) and biassed by a zener diode (15) connecting it to the first output terminal (3), at a constant reference voltage, and the base of which receives a fraction of the output voltage (V₃₄) of the device (10), to supply a collector current (I_C13) dependent on the difference of the reference voltage and the said fraction, and which feeds the input of this regulating member (100) so that the voltage drop (V_CE11) between the first terminals (1, 3) will vary in a manner to compensate for the input voltage (V₁₂) variations, the regulating member (100) further comprising a second transistor (12) of a type complementary to the first (11), the emitter of which is connected to the collector thereof and the collector thereof being connected to the base of the first (1 1 ), and its base being connected to the collector of the third transistor (13), a first resistor (101) connecting the collector with the base of the first transistor (11) and allowing the conductive state thereof to be assured at the beginning of operation and to limit its maximum emitter current in case of short circuit, characterized by the fact that a second resistor (102) connects the collector of the first transistor (11) to the emitter of the second (12) to limit the collector current (I_C12) thereof which feeds the base (I_B11) of the first transistor (11), so that the power dissipation of the first transistor (11) equal to the product of its overload collector-emitter- voltage and its collector current limited by its base current, will not exceed a predetermined value.

2. Voltage regulator device of claim 1, combined with a line scanning circuit (22) of a television receiver supplied by the voltage provided thereby, and the autonomous operation thereof starting from a predetermined output voltage (V₃₄) of this device (10), the line scanning circuit (22) comprising a line transformer (32) the primary winding of which (320) is periodically supplied by the output voltage (V₃₄) of the regulator through an electronic interrupter (38, 37) which is periodically opened and closed, and a secondary winding of which (321) supplies a rectifying circuit (25, 26) providing an auxiliary supply voltage (V₂₆) which is at least slightly higher than the input voltage (V₁₂) of the device (10), characterized by the fact that this auxiliary voltage (V₂₆) is applied to a further input (27) of the device (10) which is connected to the emitter of the second transistor (12) through a third resistor (103) to supply an emitter current (I_EII) thereto sufficient to bring the first transistor (11) to saturation without saturating the same, in order to amplify the open loop regulation gain and to keep it constant, and to reduce the loss voltage between the connector and the emitter of the first transistor to a minimum value.

3. Portable television receiver adapted to be supplied by an accumulator or by the ac mains through a filtered rectifier, characterized by the fact that it comprises a voltage regulator device in accordance with claim 2, the further input (27) of which is supplied through the rectifier circuit (25, 26) from a secondary winding (321) of the line transformer (32) the primary winding (320) of which is connected to one of the terminals of the bidirectional interrupter (38, 37) of the output stage (30) of the line scanning circuit and is supplied by the output of the regulating device (10).

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