A light-emitting diode (LED) lighting system, comprising:
- a luminaire, comprising:
- one or more LED arrays with an intrinsic forward voltage across thereon;
- and
- a power supply unit, comprising:
- at least two electrical conductors configured to couple to a line voltage from alternating-current (AC) mains;
- an input filter configured to suppress electromagnetic interference (EMI) noises;
- a first full-wave rectifier coupled to the at least two electrical conductors, the first full-wave rectifier configured to convert the line voltage from the AC mains into a fifth DC voltage;
- at least one isolated power converter comprising a first transformer and a third ground reference, wherein the at least one isolated power converter is coupled to the first full-wave rectifier via the input filter and configured to improve a power factor, to reduce voltage ripples, and to convert the fifth DC voltage into a sixth DC voltage when the line voltage from the AC mains is available;
- and
- a first at least one DC-to-DC converter coupled to the at least one isolated power converter, the first at least one DC-to-DC converter configured to convert the sixth DC voltage into a seventh DC voltage with respect to the third ground reference;
- and
- an add-on luminaire control gear, comprising:
- a rechargeable battery;
- a second full-wave rectifier coupled to the AC mains and configured to convert the line voltage from the AC mains into a first DC voltage;
- a charging circuit comprising a second 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 second 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;
- a second 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 second 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 the seventh DC voltage to the one or more LED arrays to operate thereon,
- wherein:
- the at least one isolated power converter and the first at least one DC-to-DC converter are combined to form a current source, wherein, when the one or more LED arrays require more current than a predetermined maximum, the seventh DC voltage drops accordingly;
- the relay switch further comprises a first pair, a second pair, 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 seventh DC voltage with respect to the third ground reference, 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 seventh DC voltage to the one or more LED arrays to operate thereon;
- and
- the transistor circuit is further configured to disable the relay switch when required.