A light-emitting element driving device and controller and dimming method for the light-emitting element driving device. The light-emitting driving device has a dimming resistor and a power converter. A first current is provided to the dimming resistor, and a voltage across the dimming resistor is compared with a first threshold voltage. Then a second current is provided according to the comparison result. A dimming signal is generated based the voltage across the dimming resistor and a current flowing through the dimming resistor, to control the power converter to drive a plurality of light-emitting elements. A plurality of voltage windows may be configured for the dimming signal. a 2-step dimming function may be activated for high precision.