US 8,786,268 B2Granted

Current mode voltage regulator with auto-compensation

AssigneeLinear Technology Corporation

InventorsJian Li, Jindong Henry Zhang

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Abstract

A method for automatically compensating a voltage regulator initially disconnects the error amplifier and compensation network from the feedback loop. A DC bias voltage is applied to the feedback loop to cause the regulator's output voltage to be at 90% of its nominal value. An AC perturbation signal is then added to the DC bias voltage to cause the output voltage to have a ripple at a frequency of the AC signal. The gain of the feedback loop and the phase difference between the AC signal and the ripple is then measured. The measured values are then used to automatically adjust operating characteristics of the error amplifier and the compensation network such that, when these components are connected back in the feedback loop during normal operation, the feedback loop has the desired gain and phase margin at the frequency of the AC signal, such as the loop's unity gain frequency.

Claims34

Dependent claims

A method for automatically compensating a voltage regulator, the regulator having a nominal output voltage, the method comprising:

applying a DC bias voltage to a first node in a feedback loop in the regulator to cause the output voltage to be at a first value;
applying an AC perturbation signal to the DC bias voltage to cause the output voltage to have a ripple at a frequency of the AC signal;
detecting a gain of the feedback loop and a phase difference between the AC signal and the ripple in the output voltage;
using the detected gain and phase difference to automatically adjust operating characteristics of one or more components in the regulator such that, when the one or more components are connected in the feedback loop, the feedback loop has a desired gain and phase margin at the frequency of the AC signal, wherein the one or more components are not connected in the feedback loop during the steps of applying the AC perturbation signal and detecting the gain of the feedback loop and the phase difference between the AC signal and the ripple in the output voltage;
and
operating the regulator with the one or more components in the feedback loop, wherein the feedback loop detects the output voltage of the regulator and regulates a duty cycle of one or more switches to maintain a regulated output voltage.

3 more elements

A voltage regulator system comprising:

a voltage regulator portion and an automatic compensation portion, the regulator portion having a feedback loop receiving a first voltage proportional to an output voltage of the regulator portion, the regulator portion adjusting a duty cycle of one or more switches, in response to the first voltage, to output a regulated output voltage, the automatic compensation portion comprising:
a controller, the controller being configured for controlling circuitry in the regulator portion and in the automatic compensation circuitry portion for automatically carrying out the following method to set a desired gain of the feedback loop and phase margin at a particular frequency, the method comprising:
applying a DC bias voltage to a first node in the feedback loop in the regulator portion to cause the output voltage to be at a first value;
applying an AC perturbation signal to the DC bias voltage to cause the output voltage to have a ripple at a frequency of the AC signal;
detecting a gain of the feedback loop and a phase difference between the AC signal and the ripple in the output voltage;
using the detected gain and phase difference to automatically adjust operating characteristics of one or more components in the regulator portion such that, when the one or more components are connected in the feedback loop, the feedback loop has a desired gain and phase margin at the frequency of the AC signal, wherein the one or more components are not connected in the feedback loop during the steps of applying the AC perturbation signal and detecting the gain of the feedback loop and the phase difference between the AC signal and the ripple in the output voltage;
and
operating the regulator portion with the one or more components in the feedback loop, wherein the feedback loop detects the output voltage of the regulator and regulates the duty cycle of the one or more switches to maintain the regulated output voltage.

5 more elements

Dependencies are inferred from the claim text.