A small cell networking device mountable to a streetlight fixture includes circuitry for converting alternating current power into direct current (DC) power and providing a digitally stable ground for operation of the small cell device. The circuitry includes a transformer isolating a primary side from a secondary side of the circuitry. A switching controller on the primary side directs a switching circuit to selectively permit current flow through a primary side of the transformer to a first ground node on the primary side. A secondary winding of the transformer sources a rectified DC output relative to a second ground node that is isolated from the first ground node. In some cases, compensation on the secondary winding side provides isolated feedback to the controller, such as via an optical isolator. The controller directs the switching circuit based at least on the feedback and input from an auxiliary winding of the transformer.

Fault-protection is provided in electrical devices by redundancy in diodes on diode legs of the bridge rectifier and a fault-protection circuit. The fault-protection circuit is configured: (i) for electrical coupling between a return of input DC power to a step-down switching DC-DC converter and a return rail of rectified DC voltage of the output DC power generated by the bridge rectifier, and is configured to perform opening the switch based on sensing a current fault or voltage fault, or (ii) to sense current from a step-down switching DC-DC converter, a first voltage from the step-down switching DC-DC converter, and/or a second voltage at an output of the step-down switching DC-DC converter, and open the circuit on a fault.

Fault-protection is provided in electrical devices by redundancy in diodes on diode legs of the bridge rectifier and a fault-protection circuit. The fault-protection circuit is configured: (i) for electrical coupling between a return of input DC power to a step-down switching DC-DC converter and a return rail of rectified DC voltage of the output DC power generated by the bridge rectifier, and is configured to perform opening the switch based on sensing a current fault or voltage fault, or (ii) to sense current from a step-down switching DC-DC converter, a first voltage from the step-down switching DC-DC converter, and/or a second voltage at an output of the step-down switching DC-DC converter, and open the circuit on a fault.

A non-isolated LED driver has a converter which delivers first and second outputs. A sense circuit is coupled to both the first output and the second output, between the converter and an LED unit. The currents at the first output and the second output are compared to obtain a difference therebetween, and a leakage fault is determined based on an alternating current component of the difference. This avoids the need for an isolated driver, by instead detecting a leakage fault and then taking appropriate safety actions.

A non-isolated LED driver has a converter which delivers first and second outputs. A sense circuit is coupled to both the first output and the second output, between the converter and an LED unit. The currents at the first output and the second output are compared to obtain a difference therebetween, and a leakage fault is determined based on an alternating current component of the difference. This avoids the need for an isolated driver, by instead detecting a leakage fault and then taking appropriate safety actions.

A warning device (100, 212, 301, 302, 510) for use in a luminaire (201, 410, 501), comprising a housing (110, 210, 310) accommodating a drive module (115, 215, 401, 402, 520) arranged to be coupled to a luminaire and to a mains voltage (260, 560). The drive module comprises a light source (120, 420) coupled to a switch (180, 380, 491, 492) and an electrical interface (140, 240) configured to electrically connect the drive module and the mains voltage to a light element (530) of the luminaire. The housing comprises a lid (130, 230, 330) operably coupled to the switch of the drive module and configured to activate the switch upon an opening of the lid for switching on the light source upon a current of the mains voltage passing in the electrical interface and deactivate the switch module upon a closing of the lid for switching off the light source.

A lamp comprises an input for connection to a high frequency ballast for gas discharge lamps. A power supply unit obtains power from a LED on voltage of the LED of the lamp, and the power supply unit powers an isolation switch at the input. During a preheat stage of the ballast, the power supply unit does not close the isolation switch, but the isolation switch is closed when the high frequency ballast is in a later state, i.e. the ignition phase.

A lamp has a safety circuit connected to first and second electrical connection terminals. A test is used to detect if the first and second electrical connection terminals are both connected to external power without an interfering impedance such a human body, and only then enable operation of the lamp. A time for the test is different from a time when another lamp in the system applies a test.

A lamp tube with anti-shock protection and compatible with a plurality of current stable power supply modes is provided. The lamp tube includes a plurality of lighting loads and a control circuit. The control circuit includes an electric shock protection circuit, a filtering and constant current driving circuit, an electronic rectifier circuit and a fast-start inductive rectifier detection and driving circuit.

A light emitting device includes a series connection unit constituted of N light emitting elements, a light emitting element driving circuit having an output terminal connected to an anode of the series connection unit, N short-circuit switches respectively connected in parallel to the light emitting elements, and a switch control unit arranged to control on and off of the short-circuit switches. A ground fault detection circuit, which detects a ground fault of the light emitting device, includes a reference voltage source arranged to generate a reference voltage, and a comparator arranged to compare the anode voltage of the series connection unit with the reference voltage. The reference voltage has a value smaller than the product of an on-resistance of one of the short-circuit switches and output current of the light emitting element driving circuit.