Microchip Technology Inc.

Supertex, Inc.

Scott Lynch

Benedict C K Choy

Jimes Lei

Roshanak Aflatouni

Benedict Choy

Employed within an LED driver operating from the AC power line, the invention controls both input current and output power. With this regulation circuit, input current appears purely resistive, precisely tracking the input voltage waveshape. At the same time, it provides good line regulation and inherent phase dimmer compatibility, requiring no special circuitry to detect and handle a dimmer.

Current control circuit for linear LED driver

A sequential linear LED driver circuit is provided. The sequential linear LED driver circuit may include a plurality of current sinks, wherein each of the plurality of current sinks is configured to be coupled to a segment of a string of light-emitting diodes (LEDs), and a voltage divider that generates a plurality of reference voltages, wherein each of the plurality of reference voltages is applied to a respective current sink of the plurality of current sinks. The output of each current sink of the plurality of current sinks may be connected at a summing node.

Commutation circuit for sequential linear LED drivers

A ripple reduction circuit is provided. The ripple reduction circuit may include a ripple capacitor configured to drive at least a first segment of a string of light emitting diodes (LEDs), a first diode having an anode coupled to the ripple capacitor, and a cathode configured to be coupled to an input end of the first LED segment, a second diode having a cathode coupled to the ripple capacitor and the anode of the first diode, and an anode configured to be coupled between the first LED segment and a second LED segment of the string of LEDs, a third diode having an anode coupled to the ripple capacitor, and a cathode configured to be coupled to a last LED segment of the string of LEDs, and a fourth diode having a cathode coupled to the ripple capacitor and the anode of the third diode.

Ripple reduction circuit for sequential linear LED drivers

An LED driver circuit for controlling direct current supplied to a plurality of serially connected segments of Light Emitting Diodes (LEDs) is disclosed. In one embodiment, the LED driver circuit comprises a self-commutating circuit, which comprises a plurality of current control elements, each current control element having two ends, a first end connected to a different end of each segment along the plurality of serially connected segments of LEDs and a second end connected to a path to ground. The path to ground comprises a sense resistor and the path to ground is shared by the second end of each current control element. Each current control element is coupled to an adjacent current control element by a cross-regulation circuit and controlled by a signal from an adjacent current control element.

Multiple stage sequential current regulator

An LED driver circuit is disclosed. The top of a string of series connected LED segments is connected to the output of a rectifier, which in turn is connected to an AC source. The string is tapped at various locations, including the bottom of the string. Each segment can consists of any number of serial or parallel connected LEDs. Current control elements or regulators sink current at each tap and are sequentially turned on and off one at a time, tracking the rectified sine wave voltage. Voltage across each regulator and current when conducting is individually controllable. The regulators may control current in a multitude of ways, including a constant current, or a current dependent on voltage across the regulators including a resistor, or a combination. The driver is self-commutating, with the sequencing of the current control elements an inherent feature closely integrated with the current control elements and providing optimal performance over variable operating conditions.

An electroactive lens driver generates a variable root-mean-square drive voltage for controlling an electroactive lens by controlling the duty cycle of a modified square wave.

Pulse width modulation driver for electroactive lens

An electroactive lens driver comprises a voltage generator generating a high alternating current voltage signal for application to an electroactive lens in response to a low direct current voltage signal. The voltage generator does not include an inductor or a transformer.

Inductorless electroactive lens driver and system

A method and circuit for converting high voltage AC to low voltage DC using a switched power supply and rising edge conduction has an alternating current (AC) power source. A rectifier is coupled to the AC power source. A switching device is coupled to the rectifier. The switching device is opened and closed only during rising edge conduction. Control circuitry is coupled to the switching device for opening and closing of the switching device only during rising edge conduction. A storage capacitive element is coupled to the switching device.

Device for converting high voltage alternating current (AC) to low voltage direct current (DC) and method therefor

A low noise method and apparatus for driving electroluminescent (EL) panels provides reduction in EL panel noise, and in the preferred embodiment, voltage compensation as the EL panel ages. The output of a high voltage power supply is applied to the EL panel through a circuit having an optimized time-constant, producing a waveform that reduces EL panel vibration. Additionally, if the time constant is derived in part from the capacitance of the EL panel, the time constant may be chosen such that aging of the EL panel maintains the time constant in the proper range to maintain noise reduction over the life of the panel and compensate for brightness reduction due to aging of the EL panel.

Growing community of inventors

Half Moon Bay, CA, United States of America

Scott Lynch