Design of HBLED Driver IC with a Built-In Bandgap Reference Voltage Generator of Stable Output Current

In this paper, we design a HBLED (Hight-brightness LED) driver IC in the 350mA class which is needed in application fields such as the back-light unit of laptops and LCD monitors, automobiles, and general lights. The designed HBLED driver IC operates at the maximum drive frequency of 250kHz and the output current of 1.5A. It is possible for the conventional band gap reference voltage generators to generate the fixed voltage but difficult to provide the fixed current as a source of current irrespective of temperature variations. On the other hand, our newly proposed band gap reference voltage generator guarantees stable IC operation by outputting both the fixed reference voltage and current as temperature changes. In addition, over-current and over-heat protection circuits are built in it. The HBLED drive IC is designed with X-Fab´s 1.0μm 650V BCD process.