Abstract: In a LED driver with electric-leakage protection, a series cascade of a current sensor and a solid-state switch connects a converter circuit to a unipolar voltage source powered by an external voltage source connected to the driver through two electrical contacts. The current sensor measures a return current returned from the converter circuit to the unipolar voltage source. The switch isolates the unipolar voltage source from the converter circuit for electric-shock prevention when the external source is determined not connected to both contacts. To determine it, the switch is switched on for a test duration to drive the converter circuit. This duration is not greater than a maximum test duration predetermined to avoid a person absorbing an energy greater than a pre-defined human-tolerable shock energy when the person accidentally touches one of the contacts. Whether the external source is connected to both contacts is determined according to the return current.