An efficiency-enhanced low dropout Linear HB LED driver for automotive application

An efficiency-enhanced linear LED driver, which operates with a wide input voltage range (6.3 V~32 V) and is able to provide output current up to 350 mA with accuracy of plusmn3%, is presented in this paper. To improve driving efficiency, an operational amplifier is exploited to lower current-sense voltage while PMOS pass element with elaborate metal layout pattern is used to reduce dropout loss. Besides, a 5 V regulated voltage is obtained from the wide range input voltage to supply some modules in the driver so as to further diminish power dissipation of the driver. The proposed driver has been fabricated on a 0.5 mum BCD process occupying 1.4 mm times 1.8 mm area. Post-simulation results show that the proposed scheme driving three HB-LEDs in series can achieve the maximum efficiency of 91.04% at I_LOAD=350 mA, which is enhanced by 7.2% compared with that of the typical linear LED driver under the same condition. The dropout voltage is 450 mV when the load current is 350 mA. Besides, it is able to recover within 99 mus.