A driving apparatus configured to drive a light emitting device includes a driving current source module operable to supply current to the light emitting device via a node during operation. A protection module coupled to the node and the driving current source module selectively injects current to the node during operation. The driving current source module is controlled based on a detection result of a voltage on the node.

A dimmable lighting system may replace a bi-level lighting system without having to modify or supplement the existing wiring between a bi-level control unit and one or more light fixtures. The dimmable lighting system may include a dimming controller that may be configured to replace a bi-level control unit in situ (i.e., e.g., in a wall-mounted dual-gang switch box). The dimmable lighting system may also include a dimming driver that may be coupled to the dimming controller via the existing wiring of the bi-level lighting system. The dimming controller may output to the dimming driver a 0-10 volt DC dimming signal referenced to an AC utility voltage. In response, a dimmable lighting device coupled to the dimming driver may output light over a wide range of dimming light levels. Methods of replacing a bi-level lighting system with a dimmable lighting system are also provided, as are other aspects.

A power conversion apparatus including a power conversion circuit, a light-emitting unit and a control chip is provided. The control chip has a multi-function pin and a feedback pin, where the multi-function pin and the feedback pin respectively receive a dimming signal and a feedback signal reflecting an output current of the light-emitting unit, and the control chip determines whether to generate a PWM signal to a power switch of the power conversion circuit according to the dimming signal and the feedback signal based on a duty ratio of the dimming signal.

Method and means for driving one or more LEDs. The method includes turning a power switch on to provide current through an inductor and the power switch, measuring voltseconds of the LEDs at a cycle time, comparing the measured voltseconds to a reference signal at an end of the cycle time, generating a signed discrete logical signal based on a difference between the measured voltseconds and the reference signal, and generating a control signal using the signed discrete logical signal to regulate a peak current through the power switch by keeping the cycle time voltseconds substantially constant. The reference signal may be proportional to a set average LED voltage.

Systems and methods are provided for determining a light intensity level of emitted light from an illuminator of a display device and the ambient light surrounding the display device such that, for example, the display device may compensate for performance variations of the illuminator over time.

A ballast circuit for a lighting system using an induction fluorescent lamp utilizes an AC-DC rectification circuit, a DC-DC boost power conversion circuit, a DC-AC half bridge inverter circuit, and a resonating circuit to ignite the lamp and maintain substantially constant power output of the lamp, while the DC-AC half bridge inverter circuit is further comprised of a gate isolation transformer connected in a half bridge inverter schematic which uses a ballast integrated circuit (IC) to drive a high side MOSFET and a low side MOSFET and the gate isolation transformer electrically isolates a gate signal to the high side MOSFET.

A power supply includes an alternating current input, a rectifier operable to generate a rectified signal based on the alternating current input, a voltage multiplier configured to generate a multiplied voltage based on the alternating current input, and an output configured to yield an electrical current based on the rectified signal from the rectifier and on the multiplied voltage from the voltage multiplier. Current is drawn from the alternating current input only during a fraction of each half-cycle of a waveform at the alternating current input.

A light emitting diode (LED) lighting system and method are disclosed. The LED lighting system and method include an LED controller to accurately control a current in an LED system. The LED controller includes components to calculate, based on the current and an active time period of an LED current time period, an actual charge amount delivered to the LED system wherein the LED current time period is duty cycle modulated at a rate of greater than fifty (50) Hz and to utilize the actual charge amount to modify and provide a desired target charge amount to be delivered during a future active time period of the LED current time period. The LED system and method further involve components to compare the actual charge amount to a desired charge amount for the active time period and compensate for a difference between the actual charge amount and the desired charge amount during the future active time period.

A lighting system includes a light-emitting diode (LED) that emits light having a hue that varies in response to variations in a voltage applied to the LED and an intensity that varies in response to variations in a duty cycle of the applied voltage. The lighting system includes a controller configured to receive a command signal having a periodic peak voltage and a periodic valley voltage. The controller includes a peak detector and a valley detector that detects the peak voltage and the valley voltage, respectively. The controller includes a pulse generator that generates a pulse stream having a pulse-voltage magnitude substantially equal to the detected peak voltage and a pulse-voltage duty cycle substantially equal to the ratio of the detected valley voltage to the detected peak voltage. The generated pulse stream is applied to the LED resulting in light emission of the controlled hue and of the controlled intensity.

A color-controlled light source includes a plurality of light emitting diodes, the light emitting diodes being configured to emit different colors of light, intensity of the light emitted by the light emitting diodes being selectably adjustable. A sensor receives the light emitted by the light emitting diodes and converts the received light to electrical feedback signals corresponding to the emitted light. A processor generates an electrical reference signal. An amplifier receives the reference signal and the feedback signal, compares the feedback signal and the reference signal, and generates an error signal corresponding to a difference between the feedback signal and the reference signal. A current control receives the error signal and adjusts the intensity of at least one light emitting diode to cancel the error signal. A composite color emitted by the plurality of light emitting diodes has a predetermined, closed-loop controlled chromaticity.