Intersil Americas Inc.

Intersil Corporation

Fred F Greenfeld

Xiaodong Zhan

Xiangxu Yu

Weihong Qiu

Grady M Wood

Rakesh Anumula

Guruprakash Radhakrishnan

An embodiment is an apparatus that includes an energy-storage circuit and a rectifying circuit. The energy-storage circuit is configured to generate a current that flows in a direction, and the rectifying circuit is configured to substantially block the current from flowing in a reverse direction in response to the current. Such an apparatus may be configured to block a reverse current before it begins to flow. For example, such an apparatus may include a transistor disposed in the path of the current, and may be configured to deactivate the transistor while a forward current is still flowing. Furthermore, by being configured to block the current from flowing in a reverse direction in response to the current itself, such an apparatus may better block a reverse current than an apparatus that blocks a reverse current in another manner, such as in response to a voltage across a rectifying transistor.

Current-responsive active rectification for a power supply operable in a discontinuous mode

An LED driver system including an input receiving a rectified AC conductive angle modulated voltage on a rectified node, a converter, a low-pass filter, and AC detector, and a driver network. The converter is coupled to the rectified node and includes a power switching device coupled to a switching node, in which the power switching device is controlled to convert the rectified AC conductive angle modulated voltage to an output voltage and output current. The low-pass filter is configured to filter voltage of the switching node to provide a filtered voltage. The AC detector receives the filtered voltage and provides a current sense signal indicative thereof. The driver network controls duty cycle of the power switching device based on the current sense signal.

LED driver system with dimmer detection

An LED driver with open loop dimming including a full wave rectifier circuit, a DC/DC converter, and an oscillator circuit. The rectifier is configured to receive an input voltage in the form of an AC conductive angle modulated voltage and to provide a rectified voltage. The DC/DC converter converts the rectified voltage to an output voltage and an output current, where the output current has a magnitude which varies proportionately with a square of a quadratic mean of the input voltage. The oscillator circuit controls switching of the DC/DC converter with constant frequency and constant duty cycle. The DC/DC converter may be a flyback converter and may include a transformer operated in DCM. The driver may include output voltage and/or output current limit. The output current may be limited when the input voltage is within normal operating range of an AC line voltage from which the input voltage is derived.

LED driver with open loop dimming control

An inrush current limiter for use with an LED driver including a current limiting device, a bypass switch device, and a switch drive. The current limiting device is placed in the input current path of the LED driver to limit input current to a predetermined maximum level in response to an AC conductive angle modulated voltage. The bypass switch device is coupled in parallel with the current limit device. The switch drive turns on the bypass switch device to at least partially bypass the current limiting device as a voltage level of an input of a switching converter rises. The input current remains sufficiently high without exceeding the maximum level. The switch drive is implemented with a delay network driven either by a separate transformer winding or by a snubber network. The delay network may have a delay based on the delay caused by the current limiting device.

Inrush current limiter for an LED driver

Disclosed are full-bridge power converters providing DC output power at increased conversion efficiencies, and methods of operating full-bridge power converters providing DC output power at increased conversion efficiencies. In disclosed embodiments, the switches of the full-bridge are operated to reduce conduction losses and to provide for zero-voltage switching.

Asymmetric zero-voltage switching full-bridge power converters

A dimming control circuit for dimming light emitting diodes receives an AC input voltage signal from a dimming circuit. The control circuit includes a power stage and a current control loop coupled to the power stage. An AC detector is operable to detect an instantaneous value of the AC input voltage signal and to generate a signal indicating whether the AC input voltage signal is present or absent. A current control circuit is operable responsive to the signal to adjust the operation of the current control loop and to control current through the light emitting diodes to achieve the desired dimming, and to prevent inrush current on the AC input voltage signal.

Method and system for dimming AC-powered light emitting diode (LED) lighting systems using conventional incandescent dimmers

A drive circuit supplies a drive current to a plurality of light emitting diodes. The drive circuit includes a voltage converter circuit having a particular topology and including at least one inductive element and at least one switching element. The drive circuit senses a current through one of the inductive and switching elements and generates a feedback signal from the sensed current. The feedback signal has a value indicating the drive current being supplied to the light emitting diodes and the drive circuit controls the operation of the voltage converter responsive to the feedback signal.

Constant current light emitting diode (LED) driver circuit and method

A connector-less charging circuit includes a transformer having a primary side associated with a secondary side. A primary switch is responsive to a control signal for connecting the transformer to ground during a first portion of a duty cycle, and disconnecting the transformer from ground during the second portion of the duty cycle. An active clamp circuit connects to the primary side of the transformer for recycling leakage energy from the transformer back to the source responsive to the control signal during the second portion of the duty cycle. A PWM controller generates the control signal to both the active clamp circuit and the primary switch.

High frequency connector-less charging scheme

A current averaging circuit for averaging a piecewise linear switching current waveform of a PWM power converter including first, second and third sample and hold circuits and a sample averaging circuit. The first sample and hold circuit samples a short duration of the current waveform for each PWM cycle and provides corresponding short samples. The second sample and hold circuit samples a long duration of each PWM cycle and provides corresponding long samples. The sample averaging circuit is coupled to the first and second sample and hold circuits, averages corresponding ones of the short and long samples and provides corresponding average values. The third sample and hold circuit samples each average value and provides a current average signal. The waveform may include ramp-on-a-step voltage pulses representing switching current. The current average signal is updated after each current pulse.

Current averaging circuit for a PWM power converter

A feed forward pulse width modulator compares a ramp signal with a control voltage to control respective states of a pulse width modulation signal. A respective cycle of the ramp signal is generated by charging a capacitor with a charging current that is proportional to input voltage until the voltage across the capacitor reaches a peak threshold that is also proportional to the input voltage. The capacitor is thereupon discharged with a discharging current proportional to the input voltage until the voltage across the capacitor reaches a (non-zero) valley threshold.

Growing community of inventors

Satellite Beach, FL, United States of America

Fred F Greenfeld