# US 2014/0192575 A1 · Method of forming a synchronous rectifier controller and structure therefor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0192575 A1 - Document ID: US20140192575A1 - Status: Published application - Kind: A1 - Application number: 13/737,081 - Filed: 2013-01-09 - Published: 2014-07-10 - Earliest claimed: 2013-01-09 - Assignees: Semiconductor Components Industries, LLC - Inventors: Lukas Olivik; Roman Stuler; Tomas Tichy - Web page: https://patentgrep.com/patent/US20140192575A1 ## CPC - 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 In one embodiment, a synchronous rectifier controller is configured to initiate forming an off-time interval for a first period of time responsively to the controller forming a disable state of a switching signal wherein the control circuit maintains the switching signal in the disable state for at least the off-time interval. The controller is also configured to restart forming the off-time interval responsively to a voltage of a synchronous rectifier becoming a first value prior to expiration of the first period of time. ## Claims ### Claim 1 A synchronous rectifier controller comprising: a control circuit configured to form a switching signal with an enable state to enable a synchronous rectifier and with a disable state to disable the synchronous rectifier; a sync input configured to receive a sync signal that is representative of a voltage drop across the synchronous rectifier; a first circuit configured to initiate the enable state of the switching signal responsively to the sync signal becoming a first value; a second circuit configured to initiate the disable state of the switching signal responsively to the sync signal becoming a second value that is greater than the first value; an off-time control circuit having a first timer circuit that is configured to initiate forming an off-time interval for a first period of time wherein the control circuit maintains the switching signal in the disable state for at least the off-time interval; and the off-time control circuit configured to restart forming the off-time interval responsively to the sync signal becoming a third value prior to expiration of the first time period. ### Claim 2 (depends on 1) The synchronous rectifier controller of claim 1 wherein the off-time control circuit maintains the switching signal in the disable state for at least the off-time interval subsequently to forming the disable state of the switching signal. ### Claim 3 (depends on 1) The synchronous rectifier controller of claim 1 wherein the off-time control circuit initiates forming the off-time interval responsively to one of the disable state of the switching signal or the sync signal becoming the third value. ### Claim 4 (depends on 1) The synchronous rectifier controller of claim 1 wherein the first circuit includes an on-time control circuit having a second timer circuit that is configured to initiate forming an on-time interval for a second period of time responsively to the control circuit forming the enable state of the switching signal wherein the control circuit maintains the switching signal in the enable state for approximately the second period of time. ### Claim 5 (depends on 4) The synchronous rectifier controller of claim 4 wherein the second circuit initiates the disable state responsively to the sync signal increasing to the second value. ### Claim 6 (depends on 4) The synchronous rectifier controller of claim 4 wherein the first timer circuit includes a current source configured to form a current to charge a capacitor and wherein the off-time control circuit includes a transistor configured to reduce the value of the current. ### Claim 7 (depends on 6) The synchronous rectifier controller of claim 6 further including, the off-time control circuit configured to enable the transistor responsively to the sync signal becoming the third value prior to expiration of the first time period. ### Claim 8 A method of forming a synchronous rectifier controller comprising: configuring the synchronous rectifier controller to initiate disabling a synchronous rectifier responsively to a voltage on a winding of a transformer that is coupled to the synchronous rectifier becoming a first value; configuring an off-time control circuit to form an off-time interval for a first period of time wherein the synchronous rectifier controller maintains the switching signal in the disable state for at least the off-time interval; and configuring the off-time control circuit to increase the off-time interval by increasing the first period of time to a second period of time responsively to the voltage becoming a different value prior to termination of ringing of the voltage. ### Claim 9 (depends on 8) The method of claim 8 wherein configuring the off-time control circuit to form the off-time interval includes configuring the off-time control circuit to form the off-time interval responsively to one of initiating disabling the synchronous rectifier or responsively to a second value of the voltage on the winding of the transformer. ### Claim 10 (depends on 8) The method of claim 8 wherein increasing the first period of time to the second period of time includes configuring a first timer to change a value of a current used to change a voltage on a capacitor. ### Claim 11 (depends on 10) The method of claim 10 wherein configuring the first timer to change the value of the current includes configuring the first timer to decrease the value of the current to substantially zero. ### Claim 12 (depends on 8) The method of claim 8 wherein increasing the first period of time to the second period of time includes configuring a first timer to discharge a capacitor responsively to the voltage becoming the different value prior to expiration of the first time period. ### Claim 13 (depends on 8) The method of claim 8 wherein configuring the off-time control circuit to increase the off-time interval includes configuring the off-time control circuit to increase the off-time interval prior to expiration of the first period of time. ### Claim 14 (depends on 8) The method of claim 8 wherein configuring the off-time control circuit to increase the off-time interval by increasing the first period of time to the second period of time includes configuring the off-time control circuit to restart forming the first period of time prior to the expiration of the first period of time. ### Claim 15 (depends on 8) The method of claim 8 wherein configuring the off-time control circuit to increase the off-time interval by increasing the first period of time to the second period of time includes configuring the off-time control circuit to restart forming the first period of time subsequent to the expiration of the first period of time and prior to termination ringing of the voltage. ### Claim 16 A method of forming a synchronous rectifier controller comprising: configuring the synchronous rectifier controller to initiate a disable state a synchronous rectifier responsively to a voltage of the synchronous rectifier becoming a first value; configuring an off-time control circuit to form an off-time interval responsively to the first value of the voltage; and configuring the off-time control circuit to one of increase the off-time interval or reinitiate forming the off-time interval prior to termination of ringing of the voltage wherein the synchronous rectifier controller maintains the switching signal in the disable state for at least a portion of the off-time interval. ### Claim 17 (depends on 16) The method of claim 16 wherein configuring the off-time control circuit to one of increase the off-time interval includes configuring the off-time control circuit to form a first period of time responsively to the first value of the voltage and to form a second period of time responsively to a second value of the voltage wherein the off-time interval continues until expiration of both the first and the second time periods of time. ### Claim 18 (depends on 16) The method of claim 16 wherein configuring the synchronous rectifier controller to initiate disabling the synchronous rectifier responsively to the voltage of the synchronous rectifier includes configuring the synchronous rectifier controller to initiate disabling the synchronous rectifier responsively to a voltage across the synchronous rectifier becoming the first value. ### Claim 19 (depends on 16) The method of claim 16 wherein configuring the off-time control circuit to one of increase the off-time interval or reinitiate forming the off-time interval includes configuring the off-time control circuit to form a first period of time and to one of increase the first period of time to a second period of time or reinitiate forming the first period of time prior to termination of the ringing of the voltage. ### Claim 20 (depends on 19) The method of claim 19 further including configuring the off-time control circuit to one of increase the first period of time to a second period of time prior to expiration of the first period of time or to reinitiate forming the first period of time prior to expiration of the first period of time.