Linear Technology Corporation

Iwatt Inc.

Yuhui Chen

Robert C Dobkin

Randy Guy Flatness

John William Kesterson

Junjie Zheng

Stephen W Hobrecht

Thomas P Hack

Mitchell Edward Lee

Doug Allen LaPorte

Howard H Haensel

An automatic voltage compensation circuit in a voltage regulator compensates the output voltage for a voltage drop along lines leading to a remote load. A load capacitor is connected across the load for providing a low impedance across the load during a test phase of the regulator. In one embodiment, during the test phase, the load current is changed up or down a small percentage (e.g., 10%). As a result, the regulator voltage changes due only to the line resistance since the load is bypassed by the load capacitor. The voltage drop at full load current is then derived by detecting the change in regulator output voltage (a fractional voltage drop) and multiplying it. The normal mode is resumed, and the derived voltage drop is added to the regulator output by either compensating the feedback loop or by adding the voltage drop to the output of the regulator.

Voltage regulator compensating for voltage drop along conductors between regulator output and load

An LED driver includes at least two interlocked closed feedback loops. One feedback loop controls the duty cycle of the on/off times of a switch connected in series to the LED string, and the other feedback loop controls the duty cycle of the on/off times of a power switch in the switching power converter that provides a DC voltage applied to the LED string. The LED driver of the present invention achieves fast control of the LED brightness and current sharing among multiple LED strings simultaneously in a power-efficient and cost-efficient manner.

LED driver with multiple feedback loops

The present invention comprises methods and circuits for spread spectrum frequency modulation that reduce peak spectral noise at the outputs or inputs of switching regulators. More specifically, the present invention modulates the operating frequency of the switching regulator in accordance with a frequency modulation waveform having a shape coordinated to a peak noise amplitude waveform that describes the correlation between the operating frequency of a switching regulator and the peak noise amplitude at the regulator's input or output absent spread spectrum frequency modulation.

Methods and circuits for frequency modulation that reduce the spectral noise of switching regulators

A monolithic switching regulator that flexibly distributes its output current among its output channels is provided. The monolithic switching regulator includes one or more additional channels that are externally connected to the output channels for providing additional current partitioning configurations. The external connections may be autosensed or programmed with an additional input pin. A switching logic circuit is provided for distributing the current among the output channels according to their external connections to the additional channels.

Circuits and methods for flexible current partitioning in monolithic switching regulators

Circuits and methods for providing an accurate phase shift between a generated output signal and an input signal are disclosed. The circuits and methods enable any amount of accurate phase shift to be set without requiring significant changes in circuitry with each phase shift. The phase shift is set by a voltage applied to a feedback amplifier connected to a low-pass filter and a timer circuit that resets a latch circuit.

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Fremont, CA, United States of America

Yuhui Chen