Flexible light engines capable of being cut, and methods thereof, are provided. A cuttable flexible light engine includes a flexible strip and strings of solid state light sources coupled in parallel. A voltage balancer establishes a desired current flow through the strings of solid state light sources when the flexible strip is cut to a desired length, and may be part of a connector placed where the strip is cut. The strings may be provided in a first set of strings coupled in parallel between a first conductive path and an intermediate conductive path and a second set of strings coupled in parallel between the intermediated conductive path and a second conductive path. A cuttable flexible light engine may also include test points positioned within the strings.

A light fixture usable in train tunnels provides normal mode downlighting for track and walkway lighting and a selective task lighting mode where higher-lumen lighting is provided in at least the same downlighting direction as the track and walkway lighting. The normal lighting illumination level is at least 0.25 to 2.00 foot-candles at the illuminated surfaces. The task lighting mode provides at least 5.00 foot-candles to the same illuminated surfaces. The task lighting mode is achieved with the same light source that provides the normal mode lighting or with additional light sources that are activated together with or instead of the normal lighting mode light sources. The light sources can be a plurality light emitting diode (LED) engines that include a plurality of LEDs. The task lighting mode can also use another light source to provide additional task lighting up from the fixture.

A lighting assembly that includes a heatsink housing, a plurality of light emitting diode (LED) modules, and a power supply disposed within a power supply casing, wherein the power supply is for providing power to the LED modules. Each LED module includes a plurality of LEDs and is thermally connected to the heatsink housing. The power supply casing includes a structure for cooling the power supply.

A lighting assembly that includes a heatsink housing, a plurality of light emitting diode (LED) modules, and a power supply disposed within a power supply casing, wherein the power supply is for providing power to the LED modules. Each LED module includes a plurality of LEDs and is thermally connected to the heatsink housing. The power supply casing includes a structure for cooling the power supply.

An LED driving system for synchronizing two LED driving integrated circuits to drive LED strings. The LED driving system sequentially activates the LED strings driven by the first LED driving integrated circuit and then outputs a downstream enabling signal from the first LED driving integrated circuit to the second LED driving integrated circuit to activate the LED strings driven by the second LED driving integrated circuit.

An LED driving system for synchronizing two LED driving integrated circuits to drive LED strings. The LED driving system sequentially activates the LED strings driven by the first LED driving integrated circuit and then outputs a downstream enabling signal from the first LED driving integrated circuit to the second LED driving integrated circuit to activate the LED strings driven by the second LED driving integrated circuit.

A lighting device circuit comprising: a reference LED string, a mirror LED string coupled in parallel to the reference LED string, an operational amplifier based current mirror circuit coupled to the reference LED string and to the mirror LED string, and a window comparator circuit that includes only a single input that is coupled to a fault sense node. The fault sense node directly connects to a drain node of a transistor within the operational amplifier based current mirror and a LED within the mirror LED string.

A lighting device circuit comprising: a reference LED string, a mirror LED string coupled in parallel to the reference LED string, an operational amplifier based current mirror circuit coupled to the reference LED string and to the mirror LED string, and a window comparator circuit that includes only a single input that is coupled to a fault sense node. The fault sense node directly connects to a drain node of a transistor within the operational amplifier based current mirror and a LED within the mirror LED string.

The invention provides a retrofit LED lamp driver having a shunt switch to alternately shunt (for a first duration) and not shunt (for a second duration) received AC power. The first duration is concurring with a first polarity of each AC cycle of the AC power, for a first period comprising at least one AC cycle, and the first duration is concurring in a second, opposite polarity of the AC power, for a second period comprising another at least one AC cycle not overlapping with the first duration. Alternating the first and second periods are provided. Any DC offset in the current drawn caused by the shunting operation is thereby cancelled over time.

The invention provides a retrofit LED lamp driver having a shunt switch to alternately shunt (for a first duration) and not shunt (for a second duration) received AC power. The first duration is concurring with a first polarity of each AC cycle of the AC power, for a first period comprising at least one AC cycle, and the first duration is concurring in a second, opposite polarity of the AC power, for a second period comprising another at least one AC cycle not overlapping with the first duration. Alternating the first and second periods are provided. Any DC offset in the current drawn caused by the shunting operation is thereby cancelled over time.