Abstract: A lighting system and a circuit for a solid state lighting apparatus are provided. The circuit includes an AC power source, an AC TRIAC dimmer, a plurality of light emitting diodes (LEDs), a bridge rectifier for providing a rectified AC waveform, and at least one capacitor for reducing flicker in the LEDs, and a plurality of LEDs with lower forward voltage connected to a static dimming bleeder or bleeder circuit for providing holding current to the triac of a dimmer circuit to increase the overall efficiency of the lighting system without dynamic control of the bleeder circuit. In some embodiments, the circuit includes a plurality of current sinks used for setting and maintaining a current to the main LEDs and to establish a stable bleeder current.

Abstract: A light emitting diode (LED) tube supporting dimming by a low voltage dimmer for replacing a conventional fluorescent lamp is disclosed. The LED tube comprises a tube body, two end caps, four pins, as well as a dimmable LED driver and one or more LEDs in the tube body wherein the LEDs are connected to the dimmable LED driver and driven by the dimmable LED driver. Two of the four pins are used for receiving power input from an AC power supply, and the other two of the four pins are used for receiving dimming control signals from a low-voltage dimmer. The tube body is a hollow cylindrical tube with the same mechanical structure of a conventional fluorescent lamp.

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.