A driving circuit includes a first inductor coupled in series with a light source for providing power to the light source. A controller coupled to the first inductor can control a switch coupled to the first inductor, thereby controlling a current flowing through the first inductor. A current sensor coupled to the first inductor can provide a first signal indicative of the current flowing through the first inductor, regardless of whether the switch is on or off. The switch is controlled according to the first signal. A second inductor magnetically coupled to the first inductor is also electrically coupled to the first inductor via a common node between the switch and the first inductor for providing a reference ground for the controller. The reference ground is different from the ground of the driving circuit.

Circuits and methods for driving light sources

Illumination sources are turned ON and turned OFF in response to detected levels of illumination in an ambient environment reaching respective thresholds, which may be user set. The detection of these turn ON and turn OFF events is verified, for instance against expected events or conditions for the particular location, date and/or time. An alert or log entry may be generated if a detected event or condition appears to be invalid. For instance, if an amount of illumination in the environment is different than predicted by a threshold amount or if a time that the event occurs or is detected is different than expected or predicted by more than a threshold amount. A level of illumination may be decreased to some non-zero level after a specified time after turn ON, and increased at some specified time before turn OFF. Use of information from external sources (e.g., satellites, cell towers) may allow times to be using local time, including daylight savings if applicable.

Apparatus and method of energy efficient illumination using received signals

A series of methods of driving multiple LED devices with high efficiency balancing technique is disclosed. The regulation of the LED current is accomplished by switching operation to compensate the difference of the LED operating voltage. Reactive components are also employed to construct non-dissipative balancing networks to drive multiple LED strings with low losses. Additionally, a series of concept is presented to drive the LED devices from PFC voltage directly with low cost circuit architecture.

Method and apparatus for driving multiple LED devices

An illumination system and methods to control a light source are provided. An illumination system includes a light source, a two-dimensional non-Passive Infrared (non-PIR) imager, and a controller. The light source provides at least two levels of illumination. The non-PIR imager images an area and to produce image data representative of images across at least part of a visible portion of an electromagnetic spectrum. The controller is communicatively coupled to receive the image data from the non-PIR imager and process the received image data to detect at least one ambient environmental characteristic of the area in the part of the visible portion of the electromagnetic spectrum, where the ambient environmental characteristic is indicative of a presence or imminent presence of a body in the area. The controller is also coupled to control operation of the light source based on, at least in part, detection of the ambient characteristic of the environment.

Long-range motion detection for illumination control

A light source apparatus includes a light source module, a local dimming control part and a light source driving part. The light source module includes a plurality of light-emitting blocks. Each of the light-emitting blocks includes a first color light source, a second color light source and a third color light source, respectively. The local dimming control part drives the light-emitting blocks by blocks. The local dimming control part sets a reference duty signal for first, second and third color driving signals in accordance with a driving mode of the light source module. The light source driving part generates the first color driving signal, the second color driving signal and the third color driving signal by using the reference duty ratio set in accordance with the driving mode and a driving current having a same peak current level in accordance with the driving mode.

Method of driving a light source, light source apparatus for performing the method and display apparatus having the light source apparatus

An LED driver is disclosed that boosts an input voltage to drive any number of LEDs in series. The driver includes a switch-mode current regulator that supplies regulated current pulses to the LEDs. No high voltage output capacitor is used to smooth the current pulses, so the LEDs are turned on any off at the switching frequency. Also, no blocking diode between the switching transistor and the LEDs is used. The cathode of the “bottom” LED in the string is connected to ground via a current sense resistor. In parallel with the sense resistor is connected an RC filter using a small, low voltage filter capacitor. The RC filter provides a substantially smooth feedback voltage for the current regulator to control the duty cycle of the switching transistor so that the feedback voltage matches a reference voltage.

Mark Ziegenfuss

Papers

Boost LED Driver Not Using Output Capacitor and Blocking Diode