System and method for voltage conversion to drive one or more light emitting diodes with at least a TRIAC dimmer. For example, the system includes: a phase detector configured to receive a first rectified voltage generated based at least in part on an AC input voltage processed by at least the TRIAC dimmer, the phase detector being further configured to generate a digital signal representing phase information associated with the first rectified voltage; a voltage generator configured to receive the digital signal and generate a DC voltage based at least in part on the digital signal; and a driver configured to receive the DC voltage and affect, based at least in part on the DC voltage, a current flowing through the one or more light emitting diodes; wherein the current changes with the phase information according to a predetermined function.