Electronic converters for light sources that comprise, for example, at least one LED (Light-Emitting Diode) or other solid-state lighting means, can supply at output a d.c. current. Said current may be stable or even vary in time, for example, for adjusting the intensity of the light emitted by the light source (the so-called “dimming function”).
FIG. 1 shows a possible lighting system including an electronic converter 10 and a lighting module 20 comprising, for example, at least one LED L.
FIG. 2 shows an example of a lighting module 20 that comprises a LED string, i.e., a plurality of LEDs connected in series. For instance, in FIG. 2 four LEDs L1, L2, L3 and L4 are shown.
The electronic converter 10 usually comprises a control circuit 102 and a power circuit 12 (for example, an AC/DC or DC/DC switching supply), which receives at input a voltage or generally a supply signal (for example, from the electric power line) and supplies at output, via a power output 106, a d.c. current. Usually, the power output 106 comprises two power supply terminals or lines, wherein the negative terminal represents a ground GND. This current may be stable or even vary over time. For instance, the control circuit 102 can set, via a reference channel Iref of the power circuit 12, the current required by the LED module 20.
For instance, this reference channel Iref may be used for adjusting the intensity of the light emitted by the lighting module 20. In fact, in general, an adjustment of the intensity of light emitted by the LED module 20 can be made by adjusting the average current that traverses the lighting module, for example by setting a lower reference current Iref or activating or de-activating the power circuit 12 through a signal with a pulse-width modulation (PWM).
In general, the LED module 20 may also comprise an identification element 202 that identifies the current required by the lighting module 20 (or in general control parameters). In this case, the control circuit 102 communicates with the identification element 202 and adapts operation of the electronic converter 10.
For instance, FIG. 3 illustrates an embodiment in which the identification element 202 comprises a simple resistor Rset.
In this case, the control unit 102 can measure the resistance of the resistor Rset and adapt operation of the power circuit 12 as a function of the resistance detected. For instance, in the example considered, the resistor Rset is connected to the control unit 102 by means of two terminals or lines S1 and S2. Typically, the line S2 is connected to ground GND and consequently could be also provided only the measuring line S1.
For instance, in the example considered, the control unit 102 comprises a pull-up resistor R1 connected in series with the resistor Rset. In this case, the voltage divider, comprising the resistors R1 and Rset, can be supplied via a voltage Vcc, and the voltage Vset at the intermediate point between the resistors R1 and Rset, i.e., on the line S1, identifies the resistance of the resistor Rset.
Instead, FIG. 4 shows an example where the resistor Rset is directly supplied through a current generator that generates a reference current Iset.
In general, the identification element 202 may also comprise a temperature sensor. For instance, this may be useful for varying the supply current on the line 106 as a function of the temperature of the lighting module 20 and/or for deactivating supply in the event of overheating of the lighting module 20.
For instance, FIG. 5 shows an identification element 202 that comprises both a resistor Rset for setting the nominal current and a temperature sensor TS, such as for example a thermistor of the negative-temperature-coefficient (NTC) type. For instance, in the embodiment considered, the NTC thermistor is connected between an auxiliary line AUX and the line S2, and the resistance of the NTC thermistor can be measured as the resistance of the resistor Rset.
In general, the value of the resistance between the measuring lines S1 and S2 could be varied also directly as a function of the temperature of the lighting module 20. Consequently, in general, the resistance of the resistor Rset or the resistance between the lines S1 and S2 is not necessarily fixed, but could also vary during operation.
The solutions described previously may also be used when a plurality of lighting modules 20 is connected in parallel.
For instance, FIG. 6 shows an example in which two lighting modules 20a and 20b are connected in parallel between the line 106 and ground GND.
In this case, also the respective identification elements 202a and 202b can be connected in parallel. In this way, the resistance detected between the lines S1 and S2 always identifies the global current required by the lighting modules 20, i.e., the sum of the current required by the module 20a and the current required by the module 20b. 
However, the inventors have noted that the solutions described previously cannot be used when the lighting modules 20 are connected in series.
For instance, FIG. 7 shows an example in which two lighting modules 20a and 20b are connected in series between the line 106 and ground GND.
The inventors have noted that in this case the current supplied by the electronic converter 12 should be set at the minimum value required by one of the lighting modules 20a and 20b. However, this cannot be obtained either with a connection in series or with a connection in parallel of the identification elements 202a and 202b when these are resistors.