Abstract: A multi-stage LED driving circuit capable of eliminating current undershoot, including: an LED module having a plurality of stage output terminals; a plurality of switch units coupled with the stage output terminals to receive a plurality of branch currents and provide a plurality of current sensing signals; a current regulation circuit, having a control end coupled with a variable reference voltage, and a current path for receiving the branch currents; and a control unit, receiving the current sensing signals and a voltage signal at an input terminal of the current path, and controlling the switch units; wherein, the control unit uses every two adjacent signals of the current sensing signals to get a ratio in turn to determine whether to switch off a corresponding switch unit of the switch units after a deferred time, and uses the voltage signal to determine whether to change the deferred time.

Abstract: An LED driver having one end coupled with an LED module and another end coupled to a ground, being capable of generating a duty current and a duty in response to a dropout voltage across the LED driver in a way that, the duty current will increase and the duty will decrease when the dropout voltage exceeds a first threshold, and the duty current will decrease and the duty will increase when the dropout voltage falls below a second threshold.

Abstract: An LED driver having one end coupled with an LED module and another end coupled to a ground, being capable of generating a duty current and a duty in response to a dropout voltage across the LED driver in a way that, the duty current will increase and the duty will decrease when the dropout voltage exceeds a first threshold, and the duty current will decrease and the duty will increase when the dropout voltage falls below a second threshold.