Abstract
In the AC- or battery-powered LED lighting systems, it is vital to regulate the average LED current for maintaining the constant luminous intensity. A constant-current LED driver that can handle a wide input range and various numbers of series-connected output LEDs would be desirable. This work presents a novel average current-detection and hysteresis turn-off (ACHT) method to achieve the current accuracy of LED drivers based on discontinuous low-side current sensing topology under wide range input and output voltages. The enhanced adaptive off-time (EAOT) loop of the LED driver is developed to solve the stability problems and control the amplitude of LED current ripple. Implemented in a 0.8-μm HV BCD process, the simulation results show that this method can remain stable and achieve accurate constant current (variations of I Avg: DC ±2.7%, AC+4.1%) independent of the peripheral circuit parameters.
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