Osram Ag

Osram Gesellschaft MIT Beschraenkter Haftung

Alberto Ferro

Paolo De Anna

Nicola Zanforlin

A circuit for supplying a light source (L) such as a high flux (HF) LED with Pulse Width Modulation (PWM) dimming capability includes: a rectifier () for receiving an input bipolar PWM modulated signal (v) representative of a desired dimming level for the light source (L) and produce therefrom a rectified signal; a current regulator () to receive the rectified signal and produce therefrom a supply current for the light source (L); and a control module () sensitive to the input bipolar PWM modulated signal (v) to control the current regulator () to produce a PWM modulated supply current for the light source (L); and a capacitor () arranged between the rectifier () and the current regulator () to stabilize the rectified signal. The circuit typically includes ancillary circuitry (), such as a microcontroller, connected to the capacitor to be supplied with the rectified signal as stabilized by the capacitor (). The ancillary circuitry () is thus supplied irrespective of the dimming level associated with the input bipolar PWM modulated signal.

Circuit for driving light sources and related method

A LED driver arrangement including a switching-mode stage to produce a drive current for feeding a LED from a DC input; a current sensor for the current fed to the LED for producing a feedback signal; error amplifier circuitry for generating a control signal from the feedback signal; and control circuitry sensitive to the control signal to control the switching-mode stage so that the drive current fed by the switching-mode stage to the LED corresponds to the LED current. An opto-coupler feeds the control signal to the control circuitry, and the opto-coupler having associated biasing circuitry to increase current on the opto-coupler when the LED current decreases. The opto-coupler is configured to saturate when the drive current reaches a minimum level. There is also an auxiliary supply voltage for the control circuitry to keep the auxiliary supply voltage above a minimum level when the opto-coupler is saturated.

Drive device for LEDs and related method

A circuit for driving LEDs includes: &#x2014;a transformer with a secondary winding for driving the LEDs and a primary winding, &#x2014;a half-bridge arrangement fed with an input voltage and coupled to the transformer, &#x2014;a resonant circuit between the half-bridge arrangement and the primary winding of the transformer, the resonant circuit having a given resonance frequency, and&#x2014;a controller configured for switching the half-bridge arrangement with a switching frequency variable between first and second values. The second value is closer than the first value to the resonance frequency of the resonant circuit created between the half-bridge arrangement and the primary winding of the transformer. This boosts the voltage fed towards the LEDs via the transformer. The LEDs are preferably included in the form of series of LEDs connected to the secondary winding of the transformer via a rectifier placed outside the housing of the power-supply.

LED driving arrangement

A current generator arrangement for use, e.g., in 1-10V interfaces for lighting systems, includes at least one transistor (Q) having a base-emitter junction wherein the voltage drop across the base-emitter junction defines the intensity of the output current and wherein the base-emitter junction is exposed to temperature drift. A resistive network (R) is coupled to the transistor (Q), whereby the intensity of the output current is a function of both the voltage drop across the base-emitter junction of the transistor (Q) and the resistance value of the resistive network (R). The resistive network (R) includes at least one resistor element (NTC; NTC) whose resistance value varies with temperature to keep constant the intensity of the output current irrespective of any temperature drift in the voltage drop across the base-emitter junction of the transistor (Q).

Growing community of inventors

Preganziol, Italy

Alberto Ferro