A light-emitting element driver system has a power conversion circuit, a second switch and a control circuit, the power conversion circuit has a primary circuit, a transformer, a first rectified circuit and a second rectified circuit, the second rectified circuit provides a first signal, the second switch has a first terminal coupled to an output terminal of the first rectified circuit and a second terminal to provide a second signal, when a dimming signal is in a first state, the control circuit provides a first control signal to control the power conversion circuit based on the first signal, and meanwhile provides a second control signal to control the second switch based on the second signal.