National Semiconductor Corporation

Texas Instruments Corporation

Semiconductor Components Industries, LLC

Steven Michael Barrow

Irwin Nederbragt

James Harbison Masson

Steven L Harris

Robert Oppen

Jade H Alberkrack

Daniel Ross Herrington

Craig Steven Cambier

Robert Bell

Yan Yin

Montu Virendra Doshi

Chi Yuen Lai

Circuits and methods for driving an LED from a secondary side of a transformer are disclosed herein. An embodiment of the method includes monitoring an input voltage to determine the power level intended to drive the LED. The current flow through the primary side of the transformer is adjusted to make the power actually driving the LED equal to the power intended to drive the LED.

Circuit and method for driving a light-emitting diode

Circuits and methods for detecting the presence of a leading-edge phase-cut dimmer. The dimmer detector comprises an edge detector, a pulse stretcher and a filter. The edge detector detects whether an input signal has a rapidly rising edge and generates an output signal pulse if a rapidly rising edge is detected. If the edge detector outputs a signal pulse, the pulse stretcher generates a stretched pulse having a duration that is longer than the signal pulse received from the edge detector. The filter produces a dimmer detect signal that indicates whether a leading-edge phase-cut dimmer is detected. If the pulse stretcher output signal comprises at least a predetermined number of stretched pulses within a predetermined amount of time, the dimmer signal signals the presence of a leading-edge phase-cut dimmer.

Leading-edge phase-cut dimmer detector

A lighting system includes a switch configured so that when the switch is in a first state, current from a supply flows to a light emitter, and when the switch is in a second state, current from the supply flows through the switch bypassing the light emitter. A capacitor in parallel with the light emitter provides current to the light emitter sufficient to cause the light emitter to emit light when the switch is in the second state.

Lighting system

A method includes receiving a sense signal having multiple pulses, where the sense signal is based on an output of a dimmer. The method also includes, for each of multiple sampling periods, (i) identifying a pulse duty cycle by sampling at least one pulse in the sense signal and calculating a duty cycle of the at least one pulse and (ii) generating an output value identifying a duty cycle for driving one or more LEDs. The output value is based on the pulse duty cycle. The method further includes generating a holding current for the dimmer (i) during the sampling of the at least one pulse in at least one of the sampling periods and (ii) when the pulse duty cycle is less than a specified threshold. The holding current can be applied continuously when the pulse duty cycle is less than the specified threshold (such as 15%).

Dimmer decoder with low duty cycle handling for use with LED drivers

A method includes receiving a sense signal having multiple pulses, where the sense signal is based on an output of a dimmer. The method also includes, for each of multiple sampling periods, (i) identifying at least one pulse duty cycle for at least one pulse in the sense signal during that sampling period and (ii) generating an output value identifying a duty cycle for driving one or more light emitting diodes (LEDs). The output value is based on the at least one pulse duty cycle. The method further includes filtering the output values using a filter and adjusting the filter based on a rate at which the output of the dimmer changes. The filter could be adjusted by controlling whether an additional resistor forms part of an RC filter based on a sampling state.

Dimmer decoder with adjustable filter for use with LED drivers

A method includes receiving a sense signal having multiple pulses, where the sense signal is based on an output of a dimmer. The method also includes, for each of multiple sampling periods, sampling a subset of the pulses in the sense signal during that sampling period. The method further includes generating a holding current for the dimmer during the sampling of the subset of pulses in at least one of the sampling periods. In addition, the method includes, for each of the sampling periods, generating an output value identifying a duty cycle for driving one or more light emitting diodes (LEDs). The subset of pulses in each of the sampling periods includes multiple pulses during that sampling period but not one or more initial pulses at a beginning of that sampling period.

Dimmer decoder with improved efficiency for use with LED drivers

Two comparators are arranged to generate a pulse-width modulator (PWM) control pulse. The first comparator is arranged to start the PWM control pulse, while the second comparator is arranged to stop the PWM control pulse. The first comparator can be a high speed CMOS comparator that includes a built-in offset. The first and second comparators can be arranged such that the built-in offset of the first comparator dominates the overall operation at the start of the control pulse. The start of the PWM control pulse is initiated by a ramp voltage and a predetermined reference level instead of a clock edge. The PWM control pulse can be linearly varied down to a zero pulse width. The PWM control pulse may be used to control the on-time of the switching element in a switching-type converter.

Two comparator voltage mode PWM

The on-time of a pulse signal is controlled by comparing a ramp signal to an input signal that is dynamically selected from two signals. A first operating mode is active when a clock signal is in a first logic state, where the pulse signal is reset. A second operating mode is initiated when the clock signal changes from the first logic state to a second logic state. During the second operating mode, the ramp signal is compared to the first signal. A third operating mode is initiated when the ramp signal exceeds the first signal during the second operating mode. During the third operating mode, the pulse signal is set and the ramp signal is compared to the second signal. The pulse signal is reset when the when the ramp signal exceeds the second signal in the third operating mode such that the on-time of the pulse signal is controlled.

System and method for generating minimum on-time pulses

A pulse frequency modulation switching regulator varies the forced off-time of a load circuit when the load circuit is subject to an overload or short circuit event. An on-switch of the circuit is deactivated for a variable time interval when an output current of the load circuit exceeds a threshold. The time interval that the on-switch is deactivated is dependent on an output voltage of the load circuit. The on-switch is deactivated for a short time interval when the load circuit is subject to a slight overload. The on-switch is deactivated for a long time interval when the load circuit is subject to a short circuit.

Apparatus and method for deactivating an on-switch of a circuit for a variable time interval

A circuit for optimizing the operation of a comparator capable of rail-to-rail operation and relatively high speed. The optimized comparator can output relatively narrow pulses in response to an input signal swinging between the rails of the power supply. Further, the comparator can provide an indication of an under voltage condition of an input signal with respect to a reference voltage. Also, the comparator can conserve power consumption by disabling those portions of the comparator that are not currently employed to resolve a high or low swing of the input signal.

Apparatus for an optimized high speed comparator

A semiconductor device ( ) includes a protection circuit ( ) that has an input ( ) for activating the protection circuit in response to a sampling pulse (V ) to detect a fault condition of the semiconductor device, and an output ( ) for producing a control signal (V ) when a fault condition is detected.

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Longmont, CO, United States of America

Steven Michael Barrow