# US 12,184,186 B2 · Power supply with active power buffer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,184,186 B2 - Document ID: US12184186B2 - Status: Granted - Kind: B2 - Application number: 17/663,141 - Filed: 2022-05-12 - Published: 2023-08-31 - Granted: 2024-12-31 - Earliest claimed: 2022-02-28 - Assignees: Apple Inc. - Applicants: Apple Inc. - Inventors: Yantao Song; Chanwit Prasantanakorn; Bharat K Patel; Abby Cherian - Web page: https://patentgrep.com/patent/US12184186B2 ## CPC - H02M 3/1566: {with means for compensating against rapid load changes, e.g. with auxiliary current source, with dual mode control or with inductance variation} - H02M 3/33592: {having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer} - H02M 1/007: {Plural converter units in cascade (push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826)} - H02M 1/15: using active elements - H02M 1/4208: {Arrangements for improving power factor of AC input} - H02M 1/4258: {using a single converter stage both for correction of AC input power factor and generation of a regulated and galvanically isolated DC output voltage (H02M1/4241 takes precedence)} - H02M 7/04: by static converters - H02M 7/217: using semiconductor devices only - H02M 1/4225: {using a non-isolated boost converter} - H02M 3/33507: {with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence)} - H02M 3/33523: {with galvanic isolation between input and output of both the power stage and the feedback loop} - H02M 3/33569: {having several active switching elements (H02M3/3353 takes precedence)} - Y02B 70/10: Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes - 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) - Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS ## Abstract A power converter can include a DC-DC converter having an output with an active power buffer coupled thereto. The active power buffer can include an energy storage capacitor and one or more switching devices selectively coupling the capacitor to the output to alternately store energy in and discharge energy from the capacitor. Control circuitry can include a DC-DC converter control loop that operates the DC-DC converter to regulate an average voltage across the capacitor and an active power buffer control loop that operates the one or more switching devices of the active power buffer to regulate an output voltage of the power converter. The DC-DC converter control loop can include a relatively slower control loop that controls the DC-DC converter during steady state load conditions and at least one relatively faster control loop that controls the DC-DC converter during transient load conditions. ## Claims ### Claim 1 A power converter comprising: a DC-DC converter stage having an input coupled to an input of the power converter and an output coupled to an output of the power converter; and an active power buffer coupled to the output of the power converter, the active power buffer further comprising: an energy storage capacitor; and one or more switching devices selectively coupling the energy storage capacitor to the output of the power converter so as to alternately store energy in and discharge energy from the energy storage capacitor; wherein control circuitry of the power converter comprises a DC-DC converter control loop that operates the DC-DC converter stage to regulate an average voltage across the energy storage capacitor of the active power buffer and an active power buffer control loop that operates the one or more switching devices of the active power buffer to regulate an output voltage of the power converter; and wherein the DC-DC converter control loop comprises a relatively slower control loop that controls the DC-DC converter stage during steady state load conditions and at least one relatively faster control loop that controls the DC-DC converter stage during transient load conditions. ### Claim 2 (depends on 1) The power converter of claim 1 wherein the at least one relatively faster control loop comprises a first relatively faster control loop that controls the DC-DC converter stage during transient load conditions resulting from a load increase and a second relatively faster control loop that controls the DC-DC converter stage during transient load condition resulting from a load decrease. ### Claim 3 (depends on 2) The power converter of claim 2 wherein the control circuitry further comprises selection circuitry configured to select a reference signal from among the output signals of the relatively slower control loop, the first relatively faster control loop, and the second relatively faster control loop. ### Claim 4 (depends on 3) The power converter of claim 3 wherein the selected reference signal is provided to a current controller and a pulse width modulation signal generator that generate drive signals for a switching device of the DC-DC converter. ### Claim 5 (depends on 1) The power converter of claim 1 wherein the relatively slower control loop is responsive to the voltage across the energy storage capacitor, and the at least one relatively faster control loop is responsive to the voltage across the energy storage capacitor and a load current of the power converter. ### Claim 6 (depends on 5) The power converter of claim 5 wherein the at least one relatively faster control loop compares the voltage across the energy storage capacitor to a reference voltage that is different than a reference voltage of the relatively slower control loop. ### Claim 7 (depends on 5) The power converter of claim 5 wherein the at least one relatively faster control loop compares an instantaneous value of the load current to an average value of the load current over a time period. ### Claim 8 (depends on 7) The power converter of claim 7 wherein the relatively faster control loop compares the instantaneous value of the load current to the average value of the load current over the time period plus an offset. ### Claim 9 (depends on 1) The power converter of claim 1 wherein the power converter is an AC-DC converter, and the DC-DC converter stage is coupled to the input of the power converter by a rectifier. ### Claim 10 (depends on 1) The power converter of claim 1 wherein the DC-DC converter stage is a flyback converter employing a split magnetics arrangement having two or more flyback transformers with their secondary windings connected in parallel. ### Claim 11 (depends on 1) The power converter of claim 1 wherein the relatively slower control loop has a bandwidth less than the line frequency of an AC input to the power converter. ### Claim 12 (depends on 11) The power converter of claim 11 wherein the relatively slower control loop has a bandwidth less than half the line frequency of the AC input to the power converter. ### Claim 13 An AC-DC converter comprising: a rectifier coupled to an AC input of the AC-DC converter; a flyback converter having an input coupled to the rectifier and an output coupled to an output of the AC-DC converter; an active power buffer coupled to the output of the AC-DC converter, the active power buffer further comprising: an energy storage capacitor; and one or more switching devices selectively coupling the energy storage capacitor to the output of the AC-DC converter so as to alternately store energy in and discharge energy from the energy storage capacitor; and control circuitry including: a flyback converter control loop that operates the flyback converter to regulate an average voltage across the energy storage capacitor of the active power buffer while providing unity power factor at the AC input of the AC-DC converter, the flyback converter control loop comprising a relatively slower control loop that controls the flyback converter during steady state load conditions and at least one relatively faster control loop that controls the flyback converter during transient load conditions; and an active power buffer control loop that operates the one or more switching devices of the active power buffer to regulate an output voltage of the AC-DC converter. ### Claim 14 (depends on 13) The AC-DC converter of claim 13 wherein the at least one relatively faster control loop comprises a first relatively faster control loop that controls the flyback converter during transient load conditions resulting from a load increase and a second relatively faster control loop that controls the flyback converter during transient load condition resulting from a load decrease. ### Claim 15 (depends on 14) The AC-DC converter of claim 14 wherein the control circuitry further comprises selection circuitry configured to select a reference signal from among the output signals of the relatively slower control loop, the first relatively faster control loop, and the second relatively faster control loop. ### Claim 16 (depends on 15) The AC-DC converter of claim 15 wherein the selected reference signal is provided to a current controller and a pulse width modulation signal generator that generate drive signals for a switching device of the flyback converter. ### Claim 17 (depends on 13) The AC-DC converter of claim 13 wherein the relatively slower control loop is responsive to the voltage across the energy storage capacitor, and the at least one relatively faster control loop is responsive to the voltage across the energy storage capacitor and the load current. ### Claim 18 (depends on 17) The AC-DC converter of claim 17 wherein the at least one relatively faster control loop compares the voltage across the energy storage capacitor to a reference voltage that is different than a reference voltage of the relatively slower control loop. ### Claim 19 (depends on 17) The AC-DC converter of claim 17 wherein the at least one relatively faster control loop compares an instantaneous value of the load current to an average value of the load current over a time period. ### Claim 20 (depends on 19) The AC-DC converter of claim 19 wherein the relatively faster control loop compares the instantaneous value of the load current to the average value of the load current over the time period plus an offset. ### Claim 21 (depends on 13) The AC-DC converter of claim 13 wherein the relatively slower control loop has a bandwidth less than the line frequency of an AC input to the AC-DC converter. ### Claim 22 (depends on 21) The AC-DC converter of claim 21 wherein the relatively slower control loop has a bandwidth less than half the line frequency of the AC input to the AC-DC converter. ### Claim 23 (depends on 13) The AC-DC converter of claim 13 wherein the flyback converter employs a split magnetics arrangement having two or more flyback transformers with their secondary windings connected in parallel; and the two or more flyback transformers have their primary windings connected in series and driven by a single switching device; or the two or more flyback transformers have their primary windings connected in parallel and driven by respective switching devices for each primary winding. ### Claim 24 (depends on 13) The AC-DC converter of claim 13 wherein the active power buffer further comprises an inductor coupling the one or more switching devices to output of the AC-DC converter, wherein the active power buffer control loop operates the inductor and one or more switching devices as a bi-directional buck-boost converter. ### Claim 25 A method of operating an AC-DC converter having a rectifier, a DC-DC converter, and an active power buffer coupled to an output of the DC-DC converter, the method comprising: operating one or more switching devices of the active power buffer to regulate an output voltage of the AC-DC converter; and operating one or more switching devices of the DC-DC converter to maintain an average voltage across an energy storage capacitor of the active power buffer by controlling switching of the one or more switching devices of the DC-DC converter using a relatively slower control loop that controls the DC-DC converter during steady state load conditions and at least one relatively faster control loop that controls the DC-DC converter during transient load conditions. ### Claim 26 (depends on 25) The method of claim 25 wherein the average voltage is selected to be approximately half-way between an output voltage of the AC-DC converter and a voltage rating of the energy storage capacitor. ### Claim 27 (depends on 25) The method of claim 25 wherein operating the DC-DC converter to maintain an average voltage across an energy storage capacitor of the active power buffer further comprises operating the DC-DC converter to present unity power factor at an input of the AC-DC converter.