Abstract: An apparatus and a method monitor the status of a thermal protection device within a surge protection device (SPD). A monitoring circuit connected to a monitor output signal of the SPD is responsive to the presence of a time-varying voltage on the monitor output signal. The time-varying voltage is present during a selected half of each AC cycle when the thermal protection device is intact such that the SPD is no longer providing surge protection. The time-varying voltage is not present when the thermal protection device is no longer intact. When the time-varying voltage is not present for a selected duration, the monitoring circuit illuminates a light-emitting diode (LED) to indicate that the thermal protection device has failed.

Abstract: A multi-channel LED driver is provided with a negative current sensing method for inherent output short circuit protection, as well as protection from output misconnection. A plurality of power converters are configured to drive respective LED arrays, each power converter respectively comprising a first stage configured to provide current through a primary winding of an isolation transformer. A second stage has a capacitor coupled in parallel with a secondary winding of the isolation transformer, a current sensing resistor coupled between the secondary winding and a circuit ground for the second stage. A filtering circuit is coupled on a first end to a node between the secondary winding and the current sensing resistor, and on a second end to the circuit ground. A feedback circuit is coupled between the first stage and the filtering circuit, and configured to deliver a control signal corresponding to current through the secondary winding.