Lighting device

摘要

In one embodiment of lighting devices and lighting systems, the lighting device has a connection for connecting to a primary power supply and has a secondary power supply, such as a battery. A measuring circuit is operable to measure an impedance of the primary power supply connection and to determine from the measurement if a main power supply has failed, and if so whether to power light sources using power from the secondary power supply.

主权项

1. A method of controlling a lighting apparatus comprising one or more light sources, a primary input power connection for receiving primary power from a primary power supply, for powering a light source, a secondary input power connection for receiving secondary power from a secondary power supply, for powering a light source, the method comprising:
controlling power delivery to the one or more light sources using power received at the input power connections, such that in the event of a power failure, power from the secondary power supply is used for powering a light source; sensing an external impedance connected to the primary input power connection by applying measurement pulses to the primary input power connection to obtain an impedance measure of the external impedance; said sensing including applying a measurement pulse to the primary input power connection and measuring a decaying transient signal on the primary input power connection resulting from applying the measurement pulse to the primary input power connection; determining whether a manually operable switch coupled to the primary input power connection is in an open state or a closed state using said measure of the external impedance; and wherein the controlling step controls the power delivery in dependence upon a result of said determining.