# US 12,224,669 B2 · Flyback power converter and secondary-side 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 12,224,669 B2 - Document ID: US12224669B2 - Status: Granted - Kind: B2 - Application number: 18/104,260 - Filed: 2023-01-31 - Published: 2023-09-21 - Granted: 2025-02-11 - Earliest claimed: 2022-03-17 - Assignees: Leadtrend Technology Corp. - Applicants: Leadtrend Technology Corp. - Inventors: Chung-Wei Lin; Hung-Ching Lee; Tzu-Chen Lin - Web page: https://patentgrep.com/patent/US12224669B2 ## CPC - H02M 3/33507: {with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence)} - H02M 1/32: Means for protecting converters other than automatic disconnection - H02M 1/36: Means for starting or stopping converters - H02M 3/33592: {having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer} - 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 method of a flyback power converter includes a primary controller included in the flyback power converter generating a first gate control signal to turn on a power switch at a first predetermined valley of a first voltage after the primary controller enters a start-up mode; and a secondary controller included in the flyback power converter generating a trigger pulse to a synchronous switch at a second predetermined valley of a second voltage to make the primary controller enter a secondary-side control mode from the start-up mode after the secondary controller detects a first coupling voltage corresponding to the first gate control signal on the second voltage. ## Claims ### Claim 1 A secondary-side control method of a flyback power converter, wherein the flyback power converter comprises a primary-side controller and a secondary-side controller, the secondary-side control method comprising: the primary-side controller generating a first gate control signal to turn on a power switch at a first predetermined valley of a first voltage after the primary-side controller enters a start-up mode; and the secondary-side controller generating a trigger pulse to a synchronous switch at a second predetermined valley of a second voltage to make the primary-side controller enter a secondary-side control mode from the start-up mode after the secondary-side controller detects a first coupling voltage corresponding to the first gate control signal on the second voltage. ### Claim 2 (depends on 1) The secondary-side control method of claim 1, wherein after the secondary-side controller detects the first coupling voltage corresponding to the first gate control signal on the second voltage consecutive N cycles, the secondary-side controller generates the trigger pulse to the synchronous switch at the second predetermined valley of the second voltage, wherein N is a positive integer, and the N cycles relates to the first gate control signal. ### Claim 3 (depends on 1) The secondary-side control method of claim 1, wherein when the primary-side controller detects a second coupling voltage corresponding to the trigger pulse on the first voltage, the primary-side controller generates the first gate control signal after the second coupling voltage, and the primary-side controller enters the secondary-side control mode from the start-up mode. ### Claim 4 (depends on 2) The secondary-side control method of claim 2, wherein after the primary-side controller enters the secondary-side control mode from the start-up mode, and after the secondary-side controller consecutively detects the first coupling voltage corresponding to the first gate control signal generated after the second coupling voltage on the second voltage a predetermined times, the secondary-side controller generates the trigger pulse to the synchronous switch according to the second voltage and at least one of an output voltage and an output current of a second side of the flyback power converter to make the primary-side controller generate the first gate control signal after the second coupling voltage, wherein the second voltage is a drain voltage of the synchronous switch. ### Claim 5 (depends on 1) The secondary-side control method of claim 1, wherein the power switch is installed in a primary side of the flyback power converter, and the synchronous switch is installed in a second side of the flyback power converter. ### Claim 6 (depends on 1) The secondary-side control method of claim 1, wherein the first voltage is an auxiliary voltage of an auxiliary winding installed in a primary side of the flyback power converter. ### Claim 7 (depends on 1) The secondary-side control method of claim 1, further comprising: generating a pulse width modulation (PWM) signal to the power switch according to a direct voltage of a primary side of the flyback power converter to make the primary-side controller enter the start-up mode, wherein the pulse width modulation signal has a predetermined frequency, and the direct voltage is generated by rectifying an alternating voltage inputted in a primary side of the flyback power converter. ### Claim 8 (depends on 1) The secondary-side control method of claim 1, wherein after the primary-side controller enters the start-up mode, if the primary-side controller does not detect a second coupling voltage corresponding to the trigger pulse on the first voltage consecutive M cycles, the primary-side controller enters a protection mode from the start-up mode, wherein M is a positive integer, and the M cycles relates to the first gate control signal. ### Claim 9 (depends on 1) The secondary-side control method of claim 1, wherein a width of the trigger pulse is changed with an output voltage of a second side of the flyback power converter in reverse. ### Claim 10 (depends on 1) The secondary-side control method of claim 1, wherein a width of the trigger pulse is changed with an alternating voltage inputted in a primary side of the flyback power converter in reverse. ### Claim 11 A flyback power converter with secondary-side control, comprising: a primary-side controller, comprising: a first gate control signal generation circuit for generating a first gate control signal; a trigger pulse detection circuit for receiving a first voltage; and a start-up circuit coupled to the trigger pulse detection circuit and the first gate control signal generation circuit, wherein after the primary-side controller enters a start-up mode, the start-up circuit generates a first control signal to the first gate control signal generation circuit at a first predetermined valley of the first voltage, and the first gate control signal generation circuit generates the first gate control signal to turn on a power switch according to the first control signal; and a secondary-side controller, comprising: a voltage detection signal generation circuit coupled to an output terminal of a second side of the flyback power converter; a valley detection circuit for receiving a second voltage; and a second gate control signal generation circuit coupled to the voltage detection signal generation circuit and the valley detection circuit, wherein after the valley detection circuit detects a first coupling voltage corresponding to the first gate control signal on the second voltage, the second gate control signal generation circuit generates a trigger pulse to a synchronous switch at a second predetermined valley of the second voltage to make the primary-side controller enter a secondary-side control mode from the start-up mode. ### Claim 12 (depends on 11) The flyback power converter of claim 11, wherein after the valley detection circuit detects the first coupling voltage corresponding to the first gate control signal on the second voltage consecutive N cycles, the valley detection circuit generates the trigger pulse to the synchronous switch at the second predetermined valley of the second voltage, wherein N is a positive integer, and the N cycles relates to the first gate control signal. ### Claim 13 (depends on 11) The flyback power converter of claim 11, wherein the trigger pulse detection circuit is coupled to an auxiliary winding installed in a primary side of the flyback power converter, and the first voltage is an auxiliary voltage of the auxiliary winding. ### Claim 14 (depends on 11) The flyback power converter of claim 11, wherein when the trigger pulse detection circuit detects a second coupling voltage corresponding to the trigger pulse on the first voltage, the trigger pulse detection circuit further generates a second control signal to the first gate control signal generation circuit after the second coupling voltage, the first gate control signal generation circuit generates the first gate control signal according to the second control signal, and the primary-side controller enters the secondary-side control mode from the start-up mode. ### Claim 15 (depends on 14) The flyback power converter of claim 14, wherein after the primary-side controller enters the secondary-side control mode from the start-up mode, the voltage detection signal generation circuit generates a first detection signal to the second gate control signal generation circuit when an output voltage of the flyback power converter is less than a predetermined voltage. ### Claim 16 (depends on 15) The flyback power converter of claim 15, wherein after the valley detection circuit consecutively detects the first coupling voltage corresponding to the first gate control signal generated after the second coupling voltage on the second voltage a predetermined times, the second gate control signal generation circuit generates the trigger pulse to the synchronous switch according to the first detection signal and the second voltage to make the first gate control signal generation circuit of the primary-side controller generate the first gate control signal after the second coupling voltage. ### Claim 17 (depends on 15) The flyback power converter of claim 15, further comprising: a current detection signal generation circuit coupled to the second gate control signal generation circuit, wherein after the primary-side controller enters the secondary-side control mode from the start-up mode, when an output current of the flyback power converter is greater than a predetermined current, the current detection signal generation circuit generates a second detection signal to the second gate control signal generation circuit. ### Claim 18 (depends on 17) The flyback power converter of claim 17, wherein after the valley detection circuit consecutively detects the first coupling voltage corresponding to the first gate control signal generated after the second coupling voltage on the second voltage a predetermined times, the second gate control signal generation circuit generates the trigger pulse to the synchronous switch according to the first detection signal, the second detection signal, and the second voltage to make the first gate control signal generation circuit of the primary-side controller generate the first gate control signal after the second coupling voltage. ### Claim 19 (depends on 11) The flyback power converter of claim 11, wherein the power switch is installed in a primary side of the flyback power converter, and the synchronous switch is installed in the second side of the flyback power converter. ### Claim 20 (depends on 11) The flyback power converter of claim 11, wherein the start-up circuit further generates a pulse width modulation signal to the first gate control signal generation circuit according to a direct voltage of a primary side of the flyback power converter, and the first gate control signal generation circuit generates the first gate control signal to the power switch according to the pulse width modulation signal to make the primary-side controller enter the start-up mode, wherein the pulse width modulation signal has a predetermined frequency, and the direct voltage is generated by rectifying an alternating voltage inputted in the primary side of the flyback power converter. ### Claim 21 (depends on 11) The flyback power converter of claim 11, wherein after the primary-side controller enters the start-up mode, if the trigger pulse detection circuit does not detect a second coupling voltage corresponding to the trigger pulse on the first voltage consecutive M cycles, the primary-side controller enters a protection mode from the start-up mode, wherein M is a positive integer, and the M cycles relates to the first gate control signal. ### Claim 22 (depends on 11) The flyback power converter of claim 11, wherein a width of the trigger pulse is changed with an output voltage of the second side of the flyback power converter in reverse, and is also changed with an alternating voltage inputted in a primary side of the flyback power converter in reverse.