# US 11,309,801 B2 · Flyback converter with improved dynamic load response > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,309,801 B2 - Document ID: US11309801B2 - Status: Granted - Kind: B2 - Application number: 16/903,138 - Filed: 2020-06-16 - Published: 2020-12-31 - Granted: 2022-04-19 - Earliest claimed: 2019-06-27 - Assignees: Dialog Semiconductor GmbH - Applicants: Dialog Semiconductor Inc. - Inventors: Pengju Kong; Tao Li; Juyoung Yoon - Web page: https://patentgrep.com/patent/US11309801B2 ## CPC - H02M 3/33523: {with galvanic isolation between input and output of both the power stage and the feedback loop} - 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 3/33515: {with digital control} - H02M 3/33592: {having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer} - H02M 1/0025: {Arrangements for modifying reference values, feedback values or error values in the control loop of a converter} - 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 secondary-side control loop for a flyback converter is provided that generates a secondary-side control signal during normal operation using a compensator. In periods of significant load changes, the compensator is bypassed so that the secondary-side control signal is generated as an open-loop signal. ## Claims ### Claim 1 A secondary-side controller for a flyback converter with secondary-side regulation, comprising: an error amplifier configured to generate an error signal responsive to a difference between an output voltage and a reference voltage; a compensator configured to compensate the error signal to produce a closed-loop control signal; an output state monitor configured to determine whether a threshold load change has occurred for the flyback converter, wherein the secondary-side controller is configured to drive an optocoupler with the closed-loop control signal in response to an absence of the threshold load change and to drive the optocoupler with an open-loop control signal in response to the threshold load change; and a multiplexer configured to select between the open-loop control signal and the closed-loop control signal to provide a selected control signal for driving the optocoupler. ### Claim 2 (depends on 1) The secondary-side controller of claim 1, wherein the output state monitor is configured to determine the threshold load change using a rate of change for an output voltage. ### Claim 3 (depends on 1) The secondary-side controller of claim 1, wherein the output state monitor is configured to determine the threshold load change using a rate of change for an output current. ### Claim 4 (depends on 1) The secondary-side controller of claim 1, wherein the output state monitor is configured to transition from the drive of the optocoupler with the open-loop control signal to again drive the optocoupler with the closed-loop control signal responsive to a threshold change in a switching frequency for a power switch transistor. ### Claim 5 (depends on 1) The secondary-side controller of claim 1, wherein the secondary-side controller is further configured to increase a response speed for the compensator in response to the threshold load change. ### Claim 6 (depends on 1) The secondary-side controller of claim 1, further comprising: a lookup table configured to generate the open-loop control signal. ### Claim 7 (depends on 1) The secondary-side controller of claim 1, wherein the output state monitor is further configured to control the multiplexer to select for the open-loop control signal in response to the threshold load change and to select for the closed-loop control signal in response to the absence of the threshold load change. ### Claim 8 A method of secondary-side regulation of a flyback converter, comprising: during periods in which a load change for the flyback converter is less than a threshold load change: comparing an output voltage to a reference voltage to generate an error signal and processing the error signal in a compensator to produce a closed-loop control signal in a secondary-side controller and transmitting the closed-loop control signal to a primary-side controller; and during periods in which the load change for the flyback converter is greater than the threshold load change: generating an open-loop control signal that does not involve a use of the compensator in the secondary-side controller and transmitting the open-loop control signal to the primary-side controller. ### Claim 9 (depends on 8) The method of claim 8, further comprising: detecting whether the load change for the flyback converter is greater than the threshold load change by using a rate of change for the output voltage. ### Claim 10 (depends on 8) The method of claim 8, further comprising: detecting whether the load change for the flyback converter is greater than the threshold load change by using a rate of change for an output current. ### Claim 11 (depends on 8) The method of claim 8, further comprising: switching from a generation of the open-loop control signal to a generation of the closed-loop control signal responsive to a change in a switching frequency of a power switch transistor. ### Claim 12 (depends on 8) The method of claim 8, further comprising: adjusting the cycling of a power switch transistor responsive to a receipt of the open-loop control signal at the primary-side controller. ### Claim 13 (depends on 8) The method of claim 8, wherein the threshold load change is a threshold load change for an application of a load. ### Claim 14 (depends on 8) The method of claim 8, wherein the threshold load change is a threshold load change for a removal of a load. ### Claim 15 A flyback converter with secondary-side regulation, comprising: a secondary-side controller configured to generate an open-loop control signal during an open-loop period in response to a load change for the flyback converter being greater than a threshold level and configured to generate a closed-loop control signal after an expiration of the open-loop period, the secondary-side controller including a multiplexer configured to select between the open-loop control signal and the closed-loop control signal to provide a selected control signal; an optoisolator configured to transmit the selected control signal; and a primary-side controller configured to control a cycling of a power switch transistor in response to a receipt of the selected control signal from the optoisolator. ### Claim 16 (depends on 15) The flyback converter of claim 15, wherein the secondary-side controller includes: an output state monitor configured to determine whether the load change is greater than the threshold level. ### Claim 17 (depends on 16) The flyback converter of claim 16, wherein the threshold level is threshold level for an output current change. ### Claim 18 (depends on 16) The flyback converter of claim 16, wherein the threshold level is a threshold level for an output voltage change.