Furthermore, there are many companies like Marvell, Dialog, and Infineon that are working on an LED driving project for ICs and commonly the PWM (pulse width modulation) solution is utilized to deliver the required stable power to an LED row that is utilized for many common consumer applications, for example to illuminate the displays of smartphones or tablets.
Such an IC that provides very stable electric power required by the LED is constituted basically of switching voltage regulators that are able to manage the power coming from a DC source, typically a lithium battery, by guaranteeing good conversion efficiency, i.e., the ratio between the output power and the input power of the voltage regulator which feeds the LED.
The basic mechanism of the power conversion of the switching power regulator is the PWM strategy: An integrated power switch is turned on and off for a fixed time interval, during a period of switching, the resulting pulsed waveform is filtered by a capacitor filter at the output, to provide a constant DC voltage and current to the LED array (see Figure1):
The ST new smart solution is very interesting to me because it improves the LED driver by means of the action of the microprocessor that is the key core of the smart light system.
The microprocessor can regulate the brightness of the light emitted by the LED by using the feedback signal of a light sensor integrated in the smart packaged system. The microprocessor puts intelligence into the management of the light emitted by the LED and makes it possible for smart energy saving for street illumination purposes. This new solution holds a great deal of potential because of the high number of possible functionalities that can be added to the microcontroller.
The management of the energy supplied to the street lights for the illumination of cities usually does not take into account environmental conditions, in which the lights have to operate regardless of the material constituting the lamps, but something is changing. From an ST press release:
Many cities around the world have started to convert their existing streetlamps to use LED technology and even more are drawing up plans to do so. In the USA, for example, Boston, Massachusetts had converted 40% of its 64,000 electric streetlamps to LEDs by the end of 2012 and was already realizing $2.8 million savings annually in electricity cost, about 35% of that expense.
The city of San Jose, Calif., has agreed to this project (see Figure 2): “At the AlwaysOn GoingGreen conference in Sausalito, Calif., San Jose Mayor Chuck Reed discusses a plan to update the city's 62,000 street lights with motion sensor controls, networking technologies, and LED bulbs.”
Do you think this solution will impact the environment of the cities less than the present solution? Do you prefer LED lights for their low power consumption and the simple driving circuitry?