EP3108719A1 - Optoelectronic circuit with light-emitting diodes - Google Patents

Abstract

The invention concerns an optoelectronic circuit (20) comprising a full-wave rectifier circuit (21) comprising light-emitting diodes (27) and a circuit (30) limiting the current passing through the light-emitting diodes.

Description

 OPTOELECTRONIC CIRCUIT WITH ELECTROLUMINESCENT DIODES

The present patent application claims the priority of the French patent application FR14 / 51230 which will be considered as an integral part of the present description.

Field

 The present description relates to an optoelectronic circuit, in particular an optoelectronic circuit comprising light-emitting diodes.

Presentation of the prior art

 It is desirable to be able to supply an optoelectronic circuit comprising light-emitting diodes with an alternating voltage, in particular a sinusoidal voltage, for example the mains voltage.

FIG. 1 shows an optoelectronic circuit 10 comprising input terminals IN 1 and I 2 between which an alternating voltage j 1 is applied. The optoelectronic circuit 10 further comprises a rectifying circuit 12 comprising a diode bridge 14, receiving the voltage V 1 and supplying a rectified voltage V ^" ALIM which supplies light-emitting diodes 16, for example connected in series. ^e current flowing through the light emitting diodes 16.

2 shows a CYALJM curve of evolution of the supply voltage and f ^ _dd CJALJM evolution curve of the IALIM supply current ^{as a} function of time for an example in which the alternating voltage V _j ^ corresponds to a sinusoidal voltage. However, the VJN voltage may not be sinusoidal. For example, the voltage V ^ _j can be provided by a regulating circuit, in particular using triacs. Even though the regulator element is powered by a sinusoidal voltage, the voltage V _i then does not generally have a sinusoidal shape. When the voltage _dd ^ f is greater than the sum of threshold voltages of the LEDs 16, the LEDs 16 become conductive and behave substantially as resistors. The supply current ± ALIM then follows the supply voltage VALIM.

 A disadvantage is that the supply current I - LIM is not constant. This causes variations in the light intensity provided by the light-emitting diodes 16 which can be perceived by an observer.

 A current limiting circuit may be interposed between the rectifier circuit 12 and the light emitting diodes 16 to maintain the supply current at a substantially constant level. The structure of the optoelectronic circuit can then be relatively complex and the size of the optoelectronic circuit can be important. In addition, it may be difficult to achieve at least partly the rectifier circuit and the current limiting circuit integrated with the light emitting diodes to further reduce the size of the optoelectronic circuit.

summary

 An object of an embodiment is to overcome all or some of the disadvantages of the optoelectronic circuits described above.

 Another object of an embodiment is to reduce the size of the optoelectronic circuit.

Another object of an embodiment is to reduce the variations in light intensity provided by the optoelectronic circuit. Another object of an embodiment is to be able to produce a large number of components of the optoelectronic circuit in an integrated manner.

 Thus, an embodiment provides an optoelectronic circuit comprising:

 a full-wave rectifier circuit comprising light-emitting diodes; and

 a circuit for limiting the current flowing through the light emitting diodes.

 According to one embodiment, the circuit comprises first and second input terminals for receiving an alternating voltage and the full wave rectifier circuit comprises:

 first, second, third and fourth branches, the first and second branches having a first common node connected to the first input terminal, the third and fourth branches having a second common node connected to the second input terminal, the first and third branches having a third common node and the second and fourth branches having a fourth common node;

 a first set of light-emitting diodes mounted on the first branch in the direction from the third node to the first node; and

 a second set of light-emitting diodes mounted on the second branch in the direction from the first node to the fourth node or on the third branch in the direction from the third node to the second node,

 and the current limiting circuit traversing the light emitting diodes comprises at least one component mounted between the third node and the fourth node.

According to one embodiment, the full-wave rectifier circuit further comprises a third set of light-emitting diodes mounted on the third branch in the forward direction from the third node to the second node. According to one embodiment, the second set of light-emitting diodes is mounted on the second branch and the full-wave rectifier circuit comprises a fourth set of light-emitting diodes mounted on the fourth branch in the direction from the second node to the fourth node.

 According to one embodiment, the current limiting circuit comprises an inductance mounted between the third node and the fourth node.

 According to one embodiment, the current limiting circuit comprises a sensor of the current flowing through the inductor.

 According to one embodiment, the current limiting circuit comprises at least one first switch provided on one of the first or third branches, between the third and fourth nodes, between the first input terminal and the first node or between the first and second nodes. second input terminal and the second node and a control module for opening and closing the first switch, the control module being connected to the sensor.

 According to one embodiment, the current limiting circuit is adapted to maintain the current between a first threshold and a second threshold when the first set of light-emitting diodes or the second set of light-emitting diodes is conducting.

According to one embodiment, the circuit opto ^¬ e further comprises, means for modifying the first and second thresholds.

 According to one embodiment, the control module is adapted to control the opening of the first switch when the current flowing through the light emitting diodes of the first set or the second set is greater than the first threshold.

 According to one embodiment, the control module is adapted to control the closing of the first switch when the current flowing through the light emitting diodes of the first set or the second set is lower than the second threshold.

According to one embodiment, the first switch is mounted on the first branch or the fourth branch and the current limiting circuit comprises a second switch mounted on the second branch or the third branch, the control module being adapted to control the opening of the first switch when the current flowing through the light emitting diodes of the first set is greater than the first threshold and that the alternating voltage is of a first sign, and being adapted to control the opening of the second switch when the current flowing through the light-emitting diodes of the second set is greater than the first threshold and the alternating voltage is of a second sign opposite to the first one; sign. Brief description of the drawings

 These and other features and advantages will be set forth in detail in the following description of particular embodiments in a non-limiting manner with reference to the accompanying drawings in which:

 FIG. 1, previously described, is an electrical diagram of an example of an optoelectronic circuit comprising light-emitting diodes;

 FIG. 2, previously described, is a timing diagram of the voltage and the supply current of the light-emitting diodes of the optoelectronic circuit of FIG. 1;

 FIG. 3 is a circuit diagram of an embodiment of an optoelectronic circuit comprising light-emitting diodes;

 Figures 4 and 5 illustrate two arrangements of light emitting diodes of the optoelectronic circuit of Figure 3;

 Figure 6 is a more detailed circuit diagram of a portion of the optoelectronic circuit of Figure 3;

 FIG. 7 represents an evolution curve of the input voltage of the optoelectronic circuit of FIG. 3 and an evolution curve of the supply current of an inductance of the optoelectronic circuit of FIG. 3;

FIG. 8 represents a detail of the evolution curve of the supply current of the inductance of FIG. 7 and current evolution curves passing through global light emitting diodes of the optoelectronic circuit of Figure 3;

 Figure 9 is a more detailed circuit diagram of a portion of the optoelectronic circuit of Figure 3;

 FIGS. 10, 11 and 12 are diagrams of other embodiments of an optoelectronic circuit comprising light-emitting diodes;

 Figure 13 is a figure similar to Figure 8 obtained with the optoelectronic circuit of Figure 12;

 Fig. 14 shows an embodiment of a global light emitting diode; and

 Figures 15 to 18 each show an equivalent electrical diagram of the overall light emitting diode of Figure 13 in four operating configurations.

detailed description

 For the sake of clarity, the same elements have been designated by the same references in the various figures and, in addition, the various figures are not drawn to scale. In the rest of the description, unless otherwise indicated, the terms "substantially", "about" and "of the order of" mean "to within 10%".

According to one embodiment, the diodes electro luminescent ^¬ the optoelectronic circuit are used to make the diode bridge rectifier circuit. This makes it possible to reduce the total bulk of the optoelectronic circuit. In addition, a current limiting circuit is integrated directly into the diode bridge. This makes it possible to reduce the variations in the supply current of the light-emitting diodes while reducing the overall size of the optoelectronic circuit.

3 shows an embodiment of an opto-electronic circuit 20 comprises two input terminals _IN] _ and IN2 receiving the input voltage ^ _j. By way of example, the input voltage V _j may be a sinusoidal voltage whose frequency is, for example, between 10 MHz and 1 MHz. The Voltage V _j corresponds, for example, to the mains voltage which may possibly have been modified by a control circuit. For example, the mains voltage can be lowered or chopped by the control circuit.

The circuit 20 includes a double-wave rectifier circuit 21 comprising a diode bridge formed from four sets _D] _, D2, D3 and D4 of light emitting diodes, called global emitting diodes in the following description. Each global electroluminescent diode is composed of the series and / or in parallel of several elementary light-emitting diodes. The diode overall electro luminescent ^¬ _D] _ is mounted on a first leg 22 between a node E and a node F in the direction from the node E to the node F. The overall emitting diode D2 is mounted on a second leg 23 between the node F and a node G in the direction from the node F to the node G. The global light emitting diode D3 is mounted on a third branch 24 between the node E and a node H in the direction from the node E to the node H. The global light-emitting diode D4 is mounted on a fourth branch 25 between the node H and the node G in the forward direction from the node H to the node G.

Preferably, all the light emitting diodes of the optoelectronic circuit 20 are part of an overall light-emitting diodes _D] _, D2, D3 and D4. The overall emitting diodes _D] _, D2, D3 and D4 may include the same number of elementary emitting diodes or different numbers of individual light emitting diodes.

4 shows an embodiment of the overall light-emitting diode _D] _. The diode overall electro luminescent _D] _ R comprises branches 26 connected in parallel, each branch comprising S elementary luminescent diodes electro ^¬ 27 connected in series, R and S being greater than or equal to 2 integers. Fig. 5 shows another embodiment of the overall light emitting diode D 1. The overall light-emitting diode D1 comprises P blocks 28 connected in series, each block comprising Q elementary light-emitting diodes 27 connected in parallel, P and Q being integers greater than or equal to 2 and Q being able to vary from one block to the next. other.

 The global light-emitting diodes D2, D3 and D4 may have a structure similar to the overall light-emitting diode D 1 shown in FIG. 4 or 5.

 Returning to FIG. 3, the optoelectronic circuit

20 comprises a current limiting circuit 30 comprising an inductor 32 mounted between the nodes E and G. For example, the inductor 32 has a value between 0.1 μΗ and 10 μH. Called II ¾1 '¾2' ¾3 ^e ^ ^e ^ ¾4 current respectively flowing through inductance 32, the overall light emitting diode D] _, the overall light emitting diode D2, the overall LED D3 and the overall light-emitting diode D4. The current limiting circuit 30 further comprises a current sensor 34 adapted to supply a signal Sj representative of the current II to a control module 36. The current limiter circuit 30 further comprises a switch 38 provided between the input terminal IN _] _ and the node E and controlled by a signal S _Q provided by the control module 36. The node H is connected to the input terminal I¾. The control module 36 can be realized by a dedicated circuit.

According to one embodiment, the control module 36 is adapted to control the opening and closing of the switch 38 so that the current II remains between a lower threshold IJNF and a higher threshold IsuP- ^The upper threshold IsuP ^is strictly greater than the lower threshold IJNF.

The lower threshold IJNF is strictly greater than 0 A. For example, the current thresholds IJ ^ F and IsuP can be from a few milliamperes to several hundred milliamps. FIG. 6 is a circuit diagram of one embodiment. of the control module 36. The control module 36 can comprise a hysteresis comparator 40 receiving the signal S _j representative of the current II and providing a signal OUT which can take two values OUT + and OUT-. By way of example, when the signal S _j increases, the signal OUT is at the value OUT- when the current II is lower than the threshold IgUP ^e ^ passes to the value OUT + when the current II becomes greater than the threshold IsuP- When the current I decreases, the OUT signal is at the + OUT value when the current I is greater than the threshold ^e t P ISUP ^asse OUT- to the value when the current I becomes smaller than the threshold IsuP- control unit 36 comprises a setting module form 42 receiving the signal OUT and providing the signal SQ.

 The switch 38 is, for example, a bidirectional switch based on transistors, in particular metal oxide gate field effect transistors or MOS transistors, enrichment (normally closed) or depletion (normally open).

Elementary LEDs 27 are, for example, planar light emitting diodes or light emitting diodes formed from tri- dimensional elements, including nanowires or microwires ^¬ semi conductors, comprising a semiconductor material of a compound having my oritairement at least one group III element and a group V element (for example gallium nitride GaN), hereinafter referred to as III-V compound, or at least one group II element and a group VI element ( for example zinc oxide ZnO), hereinafter called II-VI compound.

 Advantageously, the switch 38 can be made based on a compound III-V, for example gallium nitride GaN. In this case, the switch 38 can be integrated with the light-emitting diodes.

FIG. 7 is a timing diagram of the input voltage VJ and the current II. As an example, the voltage V N is a sinusoidal voltage. FIG. 8 is a detailed view of the evolution curve of the current IL of FIG. 7 and represents, in in addition, curves of currents evolution ¾] _, ¾2 '¾3 ^e ^ ¾4 · The instants tg to t] _3 are successive instants.

An embodiment of a control method of the switch 38 during a positive half cycle and a negative half cycle of the input voltage V ^ _j will now be described.

The input voltage V _i increases from zero at time t g. The switch 38 is initially closed. The overall emitting diodes D2 and D3 are forward biased while the overall light-emitting diodes _D] _ and D4 are reverse biased. When the V _j ^ input voltage is sufficiently high at time _t] _, the current begins to flow between the terminals _IN] _ and I¾ passing successively through the overall light emitting diode D2, the inductor 32, node G to the node E, and the light-emitting diode D3.

At time t2, the current II exceeds the threshold IsuP- ^{The control} module 36 then controls the opening of the switch 38, which causes a discharge of the inductor 32. The current IL then continues to flow through II of the inductance while decreasing and is divided into a first portion which passes successively through the overall light-emitting diodes _D] _ and D2 and a second portion which successively passes through the overall light-emitting diodes D3 and D4.

At time t3, the current II decreases below the threshold I JNF- The control module 36 then commands the closing of the switch 38. The current II begins to flow again while rising between the terminal IN] _ and the terminal I¾ passing successively by the global light emitting diode D2, the inductance 32, from the node G to the node E, and the light emitting diode D3. Current II continues to increase until it exceeds the threshold IsuP at time tq. The switch 38 is then open until the current II decreases below the threshold ^ INF ^ the instant t5. The cycle between instants t2 and t is repeated as long as the input voltage Vj1 is sufficiently high. The currents ¾] _, ¾2 '¾3 ^e1: ¾4 then remain each between IJ ^ F and IsuP- At the moment tg, the input voltage Vj ^ decreases so that the current II remains below the threshold IsuP- The switch 38 then remains closed.

 At the instant ίη, the input voltage Vj ^ is no longer high enough for a current to flow between the input terminals IN ^ and I¾.

 At the moment tg, the input voltage Vj ^ vanishes and begins a negative half cycle. The switch 38 is closed. The global light-emitting diodes D 1 and D 4 are forward biased while the global light-emitting diodes D 2 and D 3 are reverse biased. When the voltage V N is sufficiently high in absolute value at the instant t g, the current begins to flow between the terminals IN 1 and I 1 passing successively by the global light-emitting diode D 4, the inductance 32, from the node G towards the node E, and the light-emitting diode D] _.

 At time t] _g, the current II exceeds the threshold IsuP-

Current regulation between I JNF and IsuP ^is performed as previously described between times t2 and tg.

At the instant t] _] _, the input voltage Vj ^ decreases so that the current II remains below the threshold IsuP ^e ^ the switch 38 remains closed.

 At time t] _2, the input voltage VJN is no longer sufficiently high in absolute value for a current to flow between the input terminals IN] _ and I¾.

 The alternation ends at the instant t] _3 when the input voltage Vjj ^ reaches zero.

When the input voltage V 1 is sufficiently high for the global light-emitting diode D 1 or D 2 to be on, the current limiting circuit 30 makes it possible to maintain the current, passing through the global light-emitting diode D 1 or D 2 which is passing between the thresholds I JNF and IsuP- Advantageously, the optoelectronic circuit 20 comprises means for modifying the thresholds I JNF ^{e "} t ^ SUP- ^The current limiting circuit 30 then makes it possible to control the current supplying the global light emitting diodes and thus to control the luminous intensity emitted by the optoelectronic circuit 20.

When the difference between the thresholds I INF ^e ^ ^ ^ ~ SUP ^are reduced, as is the case in Figure 8, the limiter circuit 20 acts as a control circuit adapted to maintain the current through the diodes emitting substantially equal to a reference current, for example equal to the average of the I JNF ^e ^ t SUP the difference between the thresholds I JNF ISUP and then represents the control accuracy around the current setpoint. For example, the gap between the stages I JNF ^{e "t} ^ ^ SUP ^are less than 10%, preferably less than 5% of stage I JNF -

Advantageously, the control module 36 may be supplied by a voltage obtained from the voltages across the overall light-emitting diodes _D] _ to D4 or other diode present in the assembly.

FIG. 9 is a circuit diagram of one embodiment of a portion of the optoelectronic circuit 20. The global light-emitting diode D2 is represented as two sets 52 and 54 of light-emitting diodes connected in series. A capacitor 50 is connected in parallel across the array 52 of light emitting diodes. The control module 36 is powered by the voltage Vj _[ across the capacitor 50. The capacitor 50 is charged whenever the global light emitting diode D2 is conducting. The voltage across the capacitor 50 is substantially constant and can be used as the supply voltage of the control module. The number of individual LEDs of the set 52 is selected based on the voltage V _[sought. For example, the voltage Vj _[ may be a few volts. In the embodiment described above, when the switch 38 is open, the current II passing through the inductor 32 is distributed between the branch 22 and the branch 24. However, it may be desirable to select in which branch the current will flow when the switch 38 is open.

 FIG. 10 represents another embodiment of an optoelectronic circuit 60 enabling such a selection to be made. The optoelectronic circuit 60 comprises all the elements of the optoelectronic circuit 20 shown in FIG. 3 and furthermore comprises a switch 62 located on the branch 25, for example between the global light-emitting diode D4 and the node G. As a Alternatively, the switch 62 may be located on the branch 24. The switch 62 is controlled by a signal S 'Q provided by the control module 36. Advantageously, the current flows between the nodes H and G always in the same direction so that the switch 62 can be a unidirectional switch.

 The switch 38 can be controlled as previously described for the optoelectronic circuit 20. Preferably, the switch 62 is closed when the switch 38 is closed and the switch 62 is open when the switch 62 is open. Alternatively, the switch 62 can be held open during all the positive half-wave of the voltage VJ and be controlled as previously indicated for the negative half-wave of VJJJ. This advantageously makes it possible to reduce the consumption of the circuit and not to have to control the switch 62 during the positive half-cycles of the supply voltage VJJJ.

When the switches 38 and 62 are opened, the inductor 32 discharges and current flows through the overall light-emitting diodes _D] _ and D2. Alternatively, the switch 62 may be located on the branch 22 or on the branch 23 if it is desired for the current to flow through the global light emitting diodes D3 and D4 when the switch 38 is open. Alternatively, in addition to the switch 62, another switch can be located on the branch 23 or the branch 24. This allows to select one of the branches 22 or 24 in which the current will flow when the switch 38 is open, this selection may vary over time.

 FIG. 11 represents another embodiment of an optoelectronic circuit 70. The optoelectronic circuit 70 comprises all the elements of the optoelectronic circuit 20 represented in FIG. 3, with the difference that the switch 38 is replaced by a switch 72, situated between the node G and a node K, the inductor 32 and the current sensor 34 being connected in series between the node E and the node K. The switch 72 is controlled by the control module 36. The optoelectronic circuit 70 comprises in addition, a diode 74 connected in parallel with the inductor 32. By way of example, the anode of the diode 74 is connected to the node E and the cathode of the diode 74 is connected to the node K. The diode 74 can be electroluminescent.

 Advantageously, the current flows between the nodes G and E always in the same direction so that the switch 72 can be a unidirectional switch.

 The control method of the switch 72 may be the same as that described above for the switch 32 in relation to the optoelectronic circuit 20. The diode 74 makes it possible to prevent the current flowing in the inductor 32 from stopping when the switch 72 is open.

FIG. 12 represents another embodiment of an optoelectronic circuit 80. The optoelectronic circuit 80 comprises all the elements of the optoelectronic circuit 20 shown in FIG. 3 except that the switch 38 is replaced by a first switch 82, located on the branch 22, for example between the node E and the global light emitting diode D3, and a second switch 84, located on the branch 24, for example between the node E and the global light emitting diode D2. Alternatively, the switch 82 may be located on the branch 25 and the switch 84 can be located on the branch 23.

The switches 82 and 84 are controlled by the control module 36. Advantageously, the current flows between the nodes E and F and between the nodes E and H always in the same direction so that each switch 82, 84 can be a unidirectional switch. The control module 36 is further adapted to detect the sign of the supply voltage VJJJ. This can be achieved by measuring the voltage across one of the individual light emitting diodes of an overall light-emitting diodes _D] _ to D4.

 One embodiment of the control method of the switches 82, 84 will be described in connection with FIGS. 7 and 13.

The input voltage V _i increases from the zero value at time tg. Switches 82 and 84 are initially closed. The overall emitting diodes _D2 and D3 are forward biased while the overall light-emitting diodes _D] _ and D4 are reverse biased. When the input voltage V _j ^ is sufficiently high, at _t] _, the current starts flowing between the IN terminal] _ and the terminal IN ₂ passing successively through the overall light-emitting diode D _2, the inductance 32, from the node G to the node E, and the light emitting diode D3.

At time t2, the current II exceeds the threshold IsuP- ^ e control module 36 then controls the opening of the switch 84, the switch 82 remaining closed. Current II then continues to flow through inductance II while decreasing and successively traverses the global electroluminescent diodes D 1 and D ₂ .

At time t3, the current II decreases below the threshold I INF- The control module 36 then commands the closing of the switch 84. The current II begins to flow again while rising between the terminals IN] _ and IN ₂ passing successively by the global light emitting diode D ₂ , the inductance 32, of node G to the node E, and the light emitting diode D3. Current II continues to increase until it exceeds the threshold IsuP at time tq.

The cycle between instants t2 and t repeats several times as long as the input voltage V _i is sufficiently high. The currents ¾] _, ¾2 '¾3 ^e ^ ¾4 then remain each between IJ ^ F and IsuP-

At time t g, the input voltage V _i decreases so that current II remains below the threshold IsuP. Switch 84 then remains closed.

At time tj, the input voltage V _i is no longer high enough for a current to flow between the input terminals IN 1 and I 2.

At instant tg, the input voltage VNN vanishes and begins a negative half cycle. Switches 82 and 84 are closed. The overall emitting diodes _D] _ and D4 are forward biased while the overall light-emitting diodes D2 and D3 are reverse biased. When the input voltage V _i is sufficiently high in absolute value, at the instant t g, the current begins to flow between the terminals IN 1 and IN 2 passing successively through the global light-emitting diode D 4, the inductance 32, from the node G to the node E, and the light-emitting diode D _] _.

At the instant t] _g, the current II exceeds the threshold IsuP- The regulation of the current between I JNF and IsuP ^is carried out as described previously from time t2 except that the switch 84 remains closed and the switch 82 is open.

At time t _] _ _] _, the input voltage V _j ^ decreases so that the current II remains below the threshold IsuP ^e ^ the switch 84 remains closed.

Alternatively, the current sensor 34 may be replaced by two current sensors, one being disposed on the branch 22 or 25 and the other being disposed on the branch 23 or 24. In Figure 7, between the times tg and _t] _, and tg and _t] _2 and _t] _3, VJN the input voltage is not high enough for the overall light-emitting diodes _D] _ and D4 or D2 and D3 are busy. There is no light emission. To reduce the duration of the phases of absence of light emission, the elementary light emitting diodes that make up each global light emitting diode can be connected to each other by a network of switches. These switches are then controlled to modify the connection of the elementary light-emitting diodes so as to modify the threshold voltage of the global light-emitting diode.

Figure 14 shows an embodiment of a global LED DC variable threshold voltage which may correspond to one of the global light-emitting diodes _D] _, D2, D3 and D4 described above. The overall emitting diode Dc includes, for example, N elementary LEDs _d] _, d2, d3 and ά ^, where N is an integer, preferably even, equal to four between Figure 14. The overall emitting diode Dc comprises an anode Ac and a cathode Cc. Each elemental light-emitting diode d 1, i being an integer ranging from 1 to N, comprises an anode A 1 and a cathode C 1. For i ranging from 1 to Nl, the anode Aj_ is connected to the anode A _j _ _+] _ by a switch SWl _j _. For i varying from 1 to Nl, the cathode Cj_ is connected to the cathode j_ + by a switch SW2 _j _. For i varying from 1 to N, the cathode C _j _ is connected to the anode A _{j + _]} _ _ _j by a switch SW3.

 FIGS. 15 to 18 are equivalent electrical diagrams of the global light-emitting diode D 1 of FIG. 14 for different configurations of closing and opening of the switches SW 1, SW 2, and SW 3, ranging from 1 to N-1.

In FIG. 15, the switches SW1 and SW2 are closed and the switches SW3 are open for i varying from 1 to N. The N elementary light-emitting diodes d1 are then connected in parallel. In FIG. 16, for i ranging from 0 to N / 2, the switches SW12 + 1 and SW22 + 1 are closed, the switches SW321 + 1 are open, the switches SW122 and SW221 are open and the switches SW32 are closed. The elementary light-emitting diodes d1 are connected in parallel in pairs, these pairs being connected in series.

In FIG. 17, the switches SW1 _] _ and SW2 _] _ are closed, the switch SW3 _] _ is open, and for i varying from 2 to N, the switches SW1 and SW2 are open and the switch SW3 is closed. Elementary LEDs _d] _ and d2 are connected in parallel, said pair being connected in series with the other elementary LEDs.

The threshold voltage of the overall light-emitting diode DC increases the configuration shown in Figure 15 to the configuration shown in FIG 18. Therefore, the SWlj_ switches, SW2j_ SW3j_ and can be controlled depending on the input voltage V _j or as a function of the current flowing between the input terminals IN _] _ and I¾ to pass successively through the configurations shown in FIGS. 15, 16, 17 and 18 as the input voltage V _i increases. By way of example, the transition from one configuration to another can be controlled when the input voltage V _i exceeds, in absolute value, a threshold. By way of example, the transition from one configuration to another can be controlled when the current flowing between the input terminals IN _] _, I¾ falls below a threshold.

 As a result, the overall light-emitting diode Dc can be on for a longer duration and the light-emitting time of the optoelectronic circuit can be increased.

 Particular embodiments have been described.

Various variations and modifications will be apparent to those skilled in the art. In particular, in the embodiments described above, the current limiting circuit comprises an inductor 32 mounted between the nodes E and G. However, the current limiting circuit can be implemented differently. he can in particular include constant current diodes or CLDs (acronym for Current Limiting Diode). Further, in the embodiments described above, the overall light emitting diodes Dl, D2, D3 and D4 are provided on each leg 22, 23, 24, 25. However, alternatively, the overall light-emitting diodes _D] _, D2 can be provided only on the branches 22 and 23, each global light emitting diode D3 and D4 being replaced by a switch controlled by the control module 36 and which is open when the global LED D3 or D4 it replaces would be polarized into direct and closed when the global light emitting diode D3 or D4 that it replaces would be reverse biased during the evolution of the input voltage VJJJ.

Claims

An optoelectronic circuit (20; 60; 70; 80) comprising: first and second input terminals (IN _] _, I¾) for receiving an alternating voltage (V _j ^); a full wave rectifier circuit (21) comprising first, second, third and fourth legs (22, 23, 24, 25), the first and second legs (22, 23) having a first common node (F) connected to the first input terminal (IN _] _), the third and fourth branches (24, 25) having a second common node (H) connected to the second input terminal (Σ¾), the first and third branches (22, 24) ) having a third common node (E) and the second and fourth branches (23, 25) having a common fourth node (G), a first set (D _] _) of light-emitting diodes (27) mounted on the first leg (22). ) in the direction from the third node (E) to the first node (F); and a second set (D2) of light-emitting diodes (27) mounted on the second branch (23) in the forward direction from the first node (F) to the fourth node (G) or on the third branch (24) in the forward direction of the third node (E) at the second node (H); and a current limiting circuit (30) traversing the light emitting diodes comprising an inductor (32) mounted between the third node (E) and the fourth node (G), a sensor (34) of the current flowing through the inductor and at least one first switch (38; 72; 82,84) provided on one of the first or third branches (22,23) between the third and fourth nodes (E, G) between the first input terminal (IN ₎ _ ) and the first node (F) or between the second input terminal (Σ¾) and the second node (H) and a control module (36) of the opening and closing of the first switch, the module control being connected to the sensor (34). Optoelectronic circuit according to claim 1, wherein the full-wave rectifier circuit (21) further comprises a third set (D3) of diodes. electroluminescent devices (27) mounted on the third branch (24) in the direction from the third node (E) to the second node (H).  Optoelectronic circuit according to Claim 2, in which the second set (D2) of light-emitting diodes (27) is mounted on the second branch (23) and in which the full-wave rectifier circuit (21) comprises a fourth set ( D4) of light emitting diodes (27) mounted on the fourth branch (25) in the direction from the second node (H) to the fourth node (G). Optoelectronic circuit according to any one of claims 1 to 3, wherein the current limiting circuit (30) is adapted to maintain the current between a first threshold (II F) ^e ^ ^a second threshold Usup) when the first together (D] _) of light-emitting diodes or the second set (D2) of light-emitting diodes is passing.  Optoelectronic circuit according to claim 4, further comprising means for modifying the first and second thresholds (IINF, SUP SUP).  Optoelectronic circuit according to claim 4, wherein the current limiting circuit (30) plays the role of a current regulating circuit passing through the light emitting diodes at a current set point.  Optoelectronic circuit according to claim 4 or 5, wherein the control module (36) is adapted to control the opening of the first switch (38; 72; 82; 84) when the current flowing through the light-emitting diodes (27) of the first set (D] _) or the second set (D2) is greater than the first threshold. Optoelectronic circuit according to claim 4 or 5, wherein the control module (36) is adapted to control the closing of the first switch (38; 72; 82; 84) when the current flowing through the light-emitting diodes (27) of the first set (D] _) or the second set (D2) is less than the second threshold. Optoelectronic circuit according to claim 4 or 5, wherein the first switch (82) is mounted on the first leg (22) or the fourth leg (25) and wherein the current limiting circuit (30) comprises a second switch (84) mounted on the second leg (25) or the third leg (24), the control module (36) being adapted to control the opening of the first switch when the current flowing through the light emitting diodes (27) of the first set (D _] _) is greater than the first threshold and that the alternating voltage (V _j ^) is of a first sign, and being adapted to control the opening of the second switch when the current flowing through the light-emitting diodes (27) of the second set (D2) is greater than the first threshold and the alternating voltage is of a second sign opposite to the first sign.