1. An add-on luminaire control gear, comprising:a rechargeable battery;
a full-wave rectifier coupled to alternating current (AC) mains and configured to convert a line voltage from the AC mains into a first direct current (DC) voltage;
a charging circuit comprising a transformer, a feedback control circuit, a control device, a first electronic switch, a diode, a first ground reference, and a second ground reference electrically isolated from the first ground reference, wherein the charging circuit is coupled to the full-wave rectifier and configured to convert the first DC voltage into a second DC voltage that charges the rechargeable battery to reach a third DC voltage, and wherein the feedback control circuit is configured to monitor the second DC voltage and to regulate the control device according to charging voltage and current requirements;
at least one DC-to-DC converter comprising a step-up converter comprising an input inductor, a second electronic switch, a logic control device, at least one diode rectifier, and an error amplifier, the at least one DC-to-DC converter configured to couple to the third DC voltage from the rechargeable battery and to convert the third DC voltage into a fourth DC voltage when the line voltage from the AC mains is unavailable; and
a power detection and control circuit comprising a transistor circuit and a relay switch, wherein the transistor circuit is configured to enable and disable the at least one DC-to-DC converter according to availability of the AC mains, and wherein the relay switch comprises a power sensing coil with a pick-up voltage and a drop-out voltage and is configured to couple either the fourth DC voltage or an external DC voltage to an external one or more light-emitting diode (LED) arrays to operate thereon,
the relay switch further comprises a first pair of input electrical terminals, a second pair of input electrical terminals, and a third pair of input electrical terminals, wherein the first pair of input electrical terminals are configured to couple to the fourth DC voltage with respect to the second ground reference, wherein the second pair of input electrical terminals are configured to couple to the external DC voltage with respect to a ground reference thereof, and wherein the third pair of input electrical terminals are configured to receive the pick-up voltage to operate the power sensing coil;
the relay switch further comprises a pair of output electrical terminals configured to relay either the fourth DC voltage or the external DC voltage to the external one or more LED arrays to operate thereon; and
the transistor circuit is further configured to disable the relay switch when required.