A novel monolithic white LED driver with dual dimming mode

摘要

This paper presents a hysteretic-current-control LED driver with the dual dimming mode. This novel monolithic driver includes an output switch and a high-side output current sensing circuit using an external resistor to set the nominal average output current (I_(OUTnom)). By applying an external control signal to the DIM pin, it can alter flexibly the control mode between the analog (DC) and switching (PWM) dimming. In the DC dimming mode, when the input DC control voltage is adjusted from 0.5 to 2.5 V, the average output current can be changed from 20 to 100% of the current I_(OUTnom). While in the switching dimming mode, the output current is proportional to the duty cycle of the input switching signal and changed from about 0 to 100% of the current I_(OUTnom). The driver circuit has been verified in a 0.5 μm HVCMOS process and the die size is about 1.2 × 1.5 mm~2. This proposed driver can work in 8-40 V power supply, the maximum average output current is up to 1.0 A.