The disclosure regards to drivers and driving methods for a LED string consisting of LEDs. The LED string and a current switch are coupled in series between a power line and a ground line. The power line is powered to regulate a signal representing a current passing through the LED string. An enable signal capable of switching the current switch is provided. Whether a predetermined event occurs is detected. When the predetermined event occurs, the enable signal is clamped to have a predetermined logic value, the current switch thereby being kept either open or short.