1. Field of the Invention
The invention deals with the field of light devices for motor vehicles. In particular, the invention relates to a light module which comprises a set of light sources, subsets of which can be switched on or off according to the required light function.
2. Description of the Related Art
A light or lighting device of a motor vehicle generally makes it possible to implement one or more light functions. They can be for example daytime running lamp (DRL) functions, headlights (HL), position lights or turn indicators (TI). Different light intensities are required according to the function.
It is common practice to use light-emitting diodes, LEDs, to implement one or more light functions of a motor vehicle. A light-emitting diode, LED, is an electronic component capable of emitting light when it is passed through by an electrical current. The light intensity emitted by an LED is generally dependent on the intensity of the electrical current which passes through it. The use of LEDs makes it possible to produce original optical signatures when designing motor vehicle lighting devices. Since a light function is often produced by a plurality of LEDs, it is becoming possible to propose a module to produce a number of functions. For example, by switching on only half of the available LEDs, it is possible to produce a light that is less intense than if all of the available LEDs are switched on. Similarly, scrolling lights, which involve a sequential and predefined switching on of LEDs arranged physically along a predefined curve, can be produced.
It is known practice in the art to use a driving circuit to drive the power supply for one or more LEDs. The circuit defines the current which passes through a branch mounted as a load and comprising the group of LEDs connected in series. It is also known practice to use a dedicated driving circuit for each of a plurality of LEDs of a light device. In this way, it becomes possible to drive each of the LEDs independently of the other LEDs of the light device. This solution presents the drawback of being costly since it requires a plurality of identical driving circuits to be implemented. In addition, such an approach does not allow for scale factoring, since the device has to be completely re-adapted and redesigned if a parameter of the light device, for example the number of LEDs used, is changed.
Alternatively, it is also known practice to incorporate switches in the driving circuit which make it possible to short-circuit one or more LEDs connected as load. Short-circuiting a group of LEDs involves diverting the load current, which bypasses the group concerned without switching on the LEDs which form part thereof. Such an architecture makes it possible to switch on or switch off groups of LEDs out of a plurality of LEDs independently by acting on the switches. However, this approach also presents drawbacks since it requires a new design of the driving circuit each time the number of LEDs used in a light device changes.