# US 2021/0281161 A1 · Predictive active filter for emi attenuation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0281161 A1 - Document ID: US20210281161A1 - Status: Published application - Kind: A1 - Application number: 17/196,736 - Filed: 2021-03-09 - Published: 2021-09-09 - Earliest claimed: 2020-03-09 - Assignees: Enphase Energy, Inc. - Applicants: Enphase Energy, Inc. - Inventors: Brian Acker; Patrick L. Chapman; Martin Fomage - Web page: https://patentgrep.com/patent/US20210281161A1 ## CPC - H02M 1/143: {using compensating arrangements (for reducing noise from the supply in transmission systems H04B15/005)} - H02M 1/14: Arrangements for reducing ripples from DC input or output - H02M 1/15: using active elements - H02M 1/44: Circuits or arrangements for compensating for electromagnetic interference in converters or inverters - 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 Methods and apparatus for reducing electromagnetic interference (EMI) in power conversion stage line filter are provided herein. The method, for example, includes determining an estimated ripple voltage or estimated ripple current using a predictive model, generating a ripple cancellation signal of opposite polarity to the estimated ripple voltage or ripple current, while compensating for at least one of magnitude or phase distortions in a signal path, and injecting the ripple cancellation signal into a power supply's line filter to reduce a ripple voltage. ## Claims ### Claim 1 A method for reducing electromagnetic interference (EMI) in a power conversion stage line filter, comprising: determining an estimated ripple voltage or estimated ripple current using a predictive model; generating a ripple cancellation signal of opposite polarity to the estimated ripple voltage or estimated ripple current, while compensating for at least one of magnitude or phase distortions in a signal path; and injecting the ripple cancellation signal into a power supply's line filter to reduce a ripple voltage. ### Claim 2 (depends on 1) The method of claim 1, wherein generating the ripple cancellation signal comprises reconstructing an ac bridge output current in response to receiving semiconductor gating waveforms or measured resonant tank current. ### Claim 3 (depends on 2) The method of claim 2, wherein reconstructing the ac bridge output current comprises selecting at least one of an offset-compensated tank current measurement or using an estimated resonant current. ### Claim 4 (depends on 1) The method of claim 1, wherein compensating for the at least one of magnitude or phase distortions in the signal path comprises generating a transfer function of the magnitude or phase based on equation H_EQ(z)=−STF−1(z)·H−1LP(z)·H−1INJ(z) and compensating for frequency response within a signal passband of about 100 kHz to 1 MHz. ### Claim 5 (depends on 1) The method of claim 1, further comprising indexing through a raised cosine lookup table to adjust an amplitude of the ripple cancellation signal to avoid excitation of line filter resonant modes. ### Claim 6 (depends on 1) The method of claim 1, further comprising generating at least one of firmware enable signal, a blend duration signal, or a firmware gain control signal. ### Claim 7 (depends on 1) The method of claim 1, further comprising autonomously enabling or disabling signal injection circuitry dependent on a power level of the estimated ripple voltage or estimated current. ### Claim 8 (depends on 1) The method of claim 1, wherein the ripple cancellation signal reduces the ripple voltage about 15 dB. ### Claim 9 A non-transitory computer readable storage medium having stored thereon instructions that when executed by a processor perform a method for reducing electromagnetic interference (EMI) in power conversion stage line filter, the method comprising: determining an estimated ripple voltage or estimated ripple current using a predictive model; generating a ripple cancellation signal of opposite polarity to the estimated ripple voltage or estimated ripple current, while compensating for at least one of magnitude or phase distortions in a signal path; and injecting the ripple cancellation signal into a power supply's line filter to reduce a ripple voltage. ### Claim 10 (depends on 9) The non-transitory computer readable storage medium of claim 9, wherein generating the ripple cancellation signal comprises reconstructing an ac bridge output current in response to receiving semiconductor gating waveforms or measured resonant tank current. ### Claim 11 (depends on 10) The non-transitory computer readable storage medium of claim 10, wherein reconstructing the ac bridge output current comprises selecting at least one of an offset-compensated tank current measurement or using an estimated resonant current. ### Claim 12 (depends on 9) The non-transitory computer readable storage medium of claim 9, wherein compensating for the at least one of magnitude or phase distortions in the signal path comprises using a transfer function of the magnitude or phase based on equation H_EQ(z)=−STF−1(z)·H−1LP(z)·H−1INJ(z) and compensating for frequency response within a signal passband of about 100 kHz to 1 MHz. ### Claim 13 (depends on 9) The non-transitory computer readable storage medium of claim 9, further comprising indexing through a raised cosine lookup table to adjust an amplitude of the ripple cancellation signal to avoid excitation of line filter resonant modes. ### Claim 14 (depends on 9) The non-transitory computer readable storage medium of claim 9, further comprising generating at least one of firmware enable signal, a blend duration signal, or a firmware gain control signal. ### Claim 15 (depends on 9) The non-transitory computer readable storage medium of claim 9, further comprising autonomously enabling or disabling signal injection circuitry dependent on a power level of the estimated ripple voltage or estimated current. ### Claim 16 (depends on 9) The non-transitory computer readable storage medium of claim 9, wherein the ripple cancellation signal reduces the ripple voltage about 15 dB. ### Claim 17 An active electromagnetic interference (EMI) filter comprising: an active filter management and control module configured to: determine an estimated ripple voltage or estimated ripple current using a predictive model; generate a ripple cancellation signal of opposite polarity to the estimated ripple voltage or estimated ripple current, while compensating for at least one of magnitude or phase distortions in a signal path; and inject the ripple cancellation signal into a power supply's line filter to reduce a ripple voltage. ### Claim 18 (depends on 17) The active electromagnetic interference (EMI) filter of claim 17, wherein the active filter management and control module is further configured to reconstruct an ac bridge output current in response to receiving semiconductor gating waveforms or measured resonant tank current. ### Claim 19 (depends on 18) The active electromagnetic interference (EMI) filter of claim 18, wherein reconstructing the ac bridge output current comprises selecting at least one of an offset-compensated tank current measurement or using an estimated resonant current. ### Claim 20 (depends on 18) The active electromagnetic interference (EMI) filter of claim 18, wherein the active filter management and control module is further configured to generate a transfer function of the magnitude or phase based on equation H_EQ(z)=−STF−1(z)·H−1LP(z)·H−1INJ(z) and compensate for frequency response within a signal passband of about 100 kHz to 1 MHz.