An integrated digital PFM DC-DC boost converter for a power management application: a RGB backlight LED system driver

In this paper is presented a system that has been designed in the frame of a co-operation between the ON Semiconductor Microelectronics Company, at its Toulouse (France) Design Centre and the Electronics Department of the University of Barcelona (SIC Group). The system that has been designed is a high efficiency boost converter to supply and drive multicolour LEDs (light emitting diodes). The paper presents the switching power DC/DC boost converter performances, based on a current peak PFM (pulse frequency modulation) system, with the objective to design this system for in low-voltage portable applications. The DC/DC converter is able to source an output current up to 300 mA, and it presents good performances for very low load conditions (100 μA), for an input battery of 3.6 V (nominal value). It needs an external inductor of 10 μH. From an external micro-controller the output voltage value can be programmed to either two values of 4 V or 5 V. LED´s brightness is controlled by a digital pulse width modulation (PWM) procedure.