Design of a LED constant-current driver using a novel hysteresis-current control method with adaptive off-time control

A novel adaptive off-time (AOT) technique, which is applicable to the circuit design of an AC-DC constant-current LED driver using hysteresis-current control method, is proposed in this paper. The AOT is achieved by a novel off-time control method, which is based on the combination of peak-current-loop and error sample feedback-loop, to solve the problem that peak current is not consistent with average current due to the constant off-time (COT) technique in the typical low side current sense topology. Output current magnitude is controlled by sense resistor. The simulation result shows that the average current error is no more than 1.1%. The average current achieves less than 1.5% variation in the output voltage range from 20V to 100V, which means good load regulation characteristic can be achieved. The design was implemented with TSMC´ 0.25μm 40V BCD process.