# US 8,786,268 B2 · Current mode voltage regulator with auto-compensation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,786,268 B2 - Document ID: US8786268B2 - Status: Granted - Kind: B2 - Application number: 13/536,596 - Filed: 2012-06-28 - Published: 2014-01-02 - Granted: 2014-07-22 - Earliest claimed: 2012-06-28 - Assignees: Linear Technology Corporation - Applicants: Jian Li; Jindong Henry Zhang - Inventors: Jian Li; Jindong Henry Zhang - Web page: https://patentgrep.com/patent/US8786268B2 ## CPC - H02M 3/156: with automatic control of output voltage or current, e.g. switching regulators - H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P) ## 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. ## Claims ### Claim 1 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. ### Claim 2 (depends on 1) The method of claim 1 wherein the frequency of the perturbation signal is selected to be approximately a unity gain frequency of the feedback loop. ### Claim 3 (depends on 1) The method of claim 1 wherein the one or more components comprises an error amplifier, and wherein the step of automatically adjusting operating characteristics of the one or more components comprises adjusting a transconductance of the error amplifier. ### Claim 4 (depends on 1) The method of claim 1 wherein the one or more components comprises a compensation network, and wherein the step of automatically adjusting operating characteristics of the one or more components comprises adjusting a characteristic of the compensation network. ### Claim 5 (depends on 4) The method of claim 4 wherein the one or more components comprises a compensation network having a resistance, and wherein the step of automatically adjusting operating characteristics of the one or more components comprises adjusting a value of the resistance. ### Claim 6 (depends on 4) The method of claim 4 wherein the one or more components comprises a compensation network having a capacitance, and wherein the step of automatically adjusting operating characteristics of the one or more components comprises adjusting a value of the capacitance. ### Claim 7 (depends on 4) The method of claim 4 wherein adjusting the characteristic of the compensation network comprises adjusting a time constant of the compensation network. ### Claim 8 (depends on 1) The method of claim 1 further comprising the feedback loop comparing a first voltage proportional to the output voltage of the regulator to a sum of the DC bias voltage and AC perturbation signal to cause the output voltage of the regulator to have the ripple. ### Claim 9 (depends on 8) The method of claim 8 wherein the first voltage and the sum of the DC bias voltage and AC perturbation signal are applied to inputs of a subtractor, wherein an output of the subtractor sets a duty cycle of the one or more switches. ### Claim 10 (depends on 1) The method of claim 1 wherein the regulated output voltage is a nominal output voltage, and wherein the step of applying the DC bias voltage causes the output voltage to be less than the nominal output voltage. ### Claim 11 (depends on 10) The method of claim 10 wherein the step of applying the AC perturbation signal to the DC bias voltage causes the output voltage to not exceed a predetermined maximum output voltage. ### Claim 12 (depends on 1) The method of claim 1 further comprising amplifying a divided output voltage of the regulator by an amplifier in the feedback loop, wherein the step of applying the AC perturbation signal to the DC bias voltage comprises applying a sum of the AC perturbation signal and DC bias voltage to a first input of a subtractor and applying an amplified divided output voltage to a second input of the subtractor, wherein an output of the subtractor is a threshold voltage that is compared to a ramping current through a power switch of the regulator. ### Claim 13 (depends on 1) The method of claim 1 further comprising generating a first voltage proportional to the output voltage of the regulator, wherein the step of applying the AC perturbation signal to the DC bias voltage comprises applying a sum of the AC perturbation signal and DC bias voltage to a first input of a subtractor and applying the first voltage to a second input of the subtractor, wherein an output of the subtractor is a threshold voltage that is compared to a ramping current through a power switch of the regulator. ### Claim 14 (depends on 13) The method of claim 13 wherein the step of operating the regulator comprises applying a reference voltage to the second input of the subtractor and applying an output of an error amplifier to a third input of the subtractor, the error amplifier comparing a feedback voltage to the reference voltage. ### Claim 15 (depends on 1) The method of claim 1 wherein the step of using the detected gain and phase difference to automatically adjust operating characteristics of one or more components in the regulator comprises selectively interconnecting a plurality of resistors in a compensation network to achieve a desired time constant of the compensation network. ### Claim 16 (depends on 1) The method of claim 1 wherein the step of using the detected gain and phase difference to automatically adjust operating characteristics of one or more components in the regulator comprises selectively interconnecting a plurality of adjustable current sources in a transconductance amplifier to achieve a desired transconductance of the transconductance amplifier. ### Claim 17 (depends on 1) The method of claim 1 wherein the steps of applying the DC bias voltage, applying the AC perturbation signal, detecting the gain and phase difference, and using the detected gain and phase difference to automatically adjust operating characteristics of one or more components in the regulator are carried out automatically under control of a digital controller. ### Claim 18 (depends on 1) The method of claim 1 wherein the feedback loop includes a digital circuit that generates a threshold voltage for comparison to a current ramp through a power switch in the regulator for regulating the output voltage. ### Claim 19 (depends on 1) The method of claim 1 wherein the feedback loop includes only analog circuitry that generates a threshold voltage for comparison to a current ramp through a power switch in the regulator for regulating the output voltage. ### Claim 20 (depends on 1) The method of claim 1 wherein the regulator is a current mode voltage regulator, and wherein the feedback loop generates a threshold voltage that is compared to a ramping current through a power switch in the regulator. ### Claim 21 (depends on 1) The method of claim 1 wherein the method is automatically carried out upon power being applied to the regulator. ### Claim 22 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. ### Claim 23 (depends on 22) The system of claim 22 wherein the frequency of the perturbation signal is selected to be approximately a unity gain frequency of the feedback loop. ### Claim 24 (depends on 22) The system of claim 22 wherein the regulator portion comprises an error amplifier, wherein the one or more components comprises the error amplifier, and wherein the step of automatically adjusting operating characteristics of the one or more components comprises adjusting a transconductance of the error amplifier. ### Claim 25 (depends on 22) The system of claim 22 wherein the regulator portion comprises a compensation network, wherein the one or more components comprises the compensation network, and wherein the step of automatically adjusting operating characteristics of the one or more components comprises adjusting a characteristic of the compensation network. ### Claim 26 (depends on 25) The system of claim 25 wherein the compensation network comprises a resistance element, and wherein the step of automatically adjusting operating characteristics of the one or more components comprises adjusting a value of the resistance element. ### Claim 27 (depends on 25) The system of claim 25 wherein adjusting the characteristic of the compensation network comprises adjusting a time constant of the compensation network. ### Claim 28 (depends on 22) The system of claim 22 wherein the regulator portion is a current mode voltage regulator. ### Claim 29 (depends on 22) The system of claim 22 further comprising an amplifier in the feedback loop amplifying a divided output voltage of the regulator portion, wherein the step of applying the AC perturbation signal to the DC bias voltage comprises applying a sum of the AC perturbation signal and DC bias voltage to a first input of a subtractor and applying an amplified divided output voltage to a second input of the subtractor, wherein an output of the subtractor is a threshold voltage that is compared to a ramping current through a power switch of the regulator portion. ### Claim 30 (depends on 22) The system of claim 22 wherein the method further comprises generating a first voltage proportional to the output voltage of the regulator, wherein the step of applying the AC perturbation signal to the DC bias voltage comprises applying a sum of the AC perturbation signal and DC bias voltage to a first input of a subtractor and applying the first voltage to a second input of the subtractor, wherein an output of the subtractor is a threshold voltage that is compared to a ramping current through a power switch of the regulator portion. ### Claim 31 (depends on 30) The system of claim 30 wherein the regulator portion comprises an error amplifier, wherein the step of operating the regulator portion comprises applying a reference voltage to the second input of the subtractor and applying an output of the error amplifier to a third input of the subtractor, the error amplifier comparing a feedback voltage to the reference voltage. ### Claim 32 (depends on 22) The system of claim 22 wherein the regulator portion comprises a compensation network, wherein the step of using the detected gain and phase difference to automatically adjust operating characteristics of one or more components in the regulator portion comprises selectively interconnecting a plurality of resistors in the compensation network to achieve a desired time constant of the compensation network. ### Claim 33 (depends on 22) The system of claim 22 wherein the regulator portion comprises a transconductance amplifier, wherein the step of using the detected gain and phase difference to automatically adjust operating characteristics of one or more components in the regulator portion comprises selectively interconnecting a plurality of adjustable current sources in the transconductance amplifier to achieve a desired transconductance of the transconductance amplifier. ### Claim 34 (depends on 22) The system of claim 22 wherein the method is automatically carried out upon power being applied to the regulator.