# US 2019/0356232 A1 · Flyback converter and control method thereof > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0356232 A1 - Document ID: US20190356232A1 - Status: Published application - Kind: A1 - Application number: 16/385,138 - Filed: 2019-04-16 - Published: 2019-11-21 - Earliest claimed: 2018-05-21 - Assignees: Delta Electronics, Inc. - Applicants: Delta Electronics,Inc. - Inventors: Haibin SONG; Daofei XU; Jinfa ZHANG - Web page: https://patentgrep.com/patent/US20190356232A1 ## CPC - H02M 3/33507: {with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence)} - H02M 3/33592: {having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer} - H02M 1/08: Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters - H02M 1/0003: {Details of control, feedback or regulation circuits} - H02M 1/0009: {Devices or circuits for detecting current in a converter} - H02M 1/0025: {Arrangements for modifying reference values, feedback values or error values in the control loop of a converter} - H02M 1/0035: {using burst mode control} - 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 flyback converter includes: a transformer, including a primary winding and a secondary winding; a primary side switch electrically coupled to the primary winding; a feedback circuit, configured to detect an output voltage of a load and output a feedback voltage signal; a current detecting circuit, configured to sample current flowing through the primary side switch and output a current signal; and a control circuit, coupled to the feedback circuit and the current detecting circuit and configured to respectively receive the feedback voltage signal and the current signal, and output a switch control signal to the primary side switch; and wherein the control circuit configured to control a switching frequency of the primary side switch to increase with increase of an output power, and an increasing speed of the switching frequency to decrease with the increase of the output power. ## Claims ### Claim 1 A flyback converter, comprising: a transformer, comprising a primary winding and a secondary winding; a primary side switch electrically coupled to the primary winding; a feedback circuit, configured to detect an output voltage of a load and output a feedback voltage signal; a current detecting circuit, configured to detect current flowing through the primary side switch and output a current signal; and a control circuit, coupled to the feedback circuit and the current detecting circuit, and configured to respectively receive the feedback voltage signal and the current signal, and output a switch control signal to the primary side switch; wherein the control circuit is further configured to control a switching frequency of the primary side switch to increase with increase of an output power, and an increasing speed of the switching frequency to decrease with the increase of the output power. ### Claim 2 (depends on 1) The flyback converter according to claim 1, wherein the control circuit comprises: a frequency regulator, configured to receive the feedback voltage signal and output a frequency control signal; a current regulator, provided with a first input terminal configured to receive the feedback voltage signal, and a second input terminal configured to receive the current signal and output a peak current control signal; and a switch signal regulator, configured to respectively receive the frequency control signal and the peak current control signal, and output the switch control signal to a control terminal of the primary side switch. ### Claim 3 (depends on 2) The flyback converter according to claim 2, wherein the frequency regulator comprises: a first regulator, configured to receive the feedback voltage signal and output a first control signal, the first regulator having a first regulation coefficient greater than zero; and a voltage-controlled oscillator, configured to receive the first control signal and output the frequency control signal. ### Claim 4 (depends on 2) The flyback converter according to claim 2, wherein the current regulator comprises: a second regulator, configured to receive the feedback voltage signal and output a second control signal, the second regulator having a second regulation coefficient greater than zero; and a comparator, provided with an inverting input terminal configured to receive the second control signal, and a noninverting input terminal configured to receive the current signal and output the peak current control signal. ### Claim 5 (depends on 2) The flyback converter according to claim 2, wherein the control circuit comprises: a third regulator, configured to receive a preset voltage signal and output a third control signal to add with the first control signal, the third regulator having a third regulation coefficient greater than zero. ### Claim 6 (depends on 2) The flyback converter according to claim 2, wherein the control circuit comprises: a fourth regulator, configured to receive a preset voltage signal and output a fourth control signal to add with the second control signal, the fourth regulator having a fourth regulation coefficient greater than zero. ### Claim 7 (depends on 2) The flyback converter according to claim 2, wherein the switch signal regulator comprises: a trigger, provided with a first input terminal coupled to the frequency regulator, a second input terminal coupled to the current regulator, and an output terminal coupled to the control terminal of the primary side switch. ### Claim 8 (depends on 1) The flyback converter according to claim 1, wherein the switching frequency of the primary side switch is great than or equal to a threshold. ### Claim 9 (depends on 8) The flyback converter according to claim 8, wherein the threshold is greater than or equal to 20 kHz. ### Claim 10 A control method of a flyback converter, comprising: detecting an output voltage of a load and generating a feedback voltage signal; detecting a current flowing through a primary side switch and generating a current signal; and generating a switch control signal based on the feedback voltage signal and the current signal to control a switching frequency of the primary side switch to increase with increase of an output power, and an increasing speed of the switching frequency to decrease with the increase of the output power. ### Claim 11 (depends on 10) The control method according to claim 10, further comprising: outputting a first control signal based on the feedback voltage signal and a first regulation coefficient, wherein the first regulation coefficient is greater than zero; and providing a voltage-controlled oscillator to output a frequency control signal based on the first control signal. ### Claim 12 (depends on 10) The control method according to claim 10, further comprising: outputting a second control signal based on the feedback voltage signal and a second regulation coefficient, wherein the second regulation coefficient is greater than zero; and providing a comparator to output a peak current control signal based on the second control signal and the current signal. ### Claim 13 (depends on 10) The control method according to claim 10, further comprising: receiving a preset voltage signal. ### Claim 14 (depends on 13) The control method according to claim 13, further comprising: outputting a third control signal based on the preset voltage signal and a third regulation coefficient, and adding the third control signal with the first control signal, wherein the third regulation coefficient is greater than zero. ### Claim 15 (depends on 13) The control method according to claim 13, further comprising: outputting a fourth control signal based on the preset voltage signal and a fourth regulation coefficient, and adding fourth control signal with the second control signal, wherein the fourth regulation coefficient is greater than zero. ### Claim 16 (depends on 12) The control method according to claim 12, further comprising: providing a trigger to generate the switch control signal based on the frequency control signal and the peak current control signal. ### Claim 17 (depends on 10) The control method according to claim 10, wherein the switching frequency of the primary side switch is great than or equal to a threshold ### Claim 18 (depends on 17) The control method according to claim 17, wherein the threshold is greater than or equal to 20 kHz.