# US 9,520,797 B2 · Adaptive reference voltage for switching power converters > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,520,797 B2 - Document ID: US9520797B2 - Status: Granted - Kind: B2 - Application number: 14/584,859 - Filed: 2014-12-29 - Published: 2016-06-09 - Granted: 2016-12-13 - Earliest claimed: 2014-12-08 - Assignees: Dialog Semicoductor Inc. - Applicants: Dialog Semiconductor Inc. - Inventors: Pengju Kong; Hien Bui; Duc Doan; Fuqiang Shi; Judy Sha - Web page: https://patentgrep.com/patent/US9520797B2 ## CPC - H02M 3/33523: {with galvanic isolation between input and output of both the power stage and the feedback loop} - H02M 3/335: using semiconductor devices only - H02M 3/33546: {with automatic control of the output voltage or current (H02M3/33561 takes precedence)} - H02M 1/0032: {Control circuits allowing low power mode operation, e.g. in standby mode} - H02M 3/33576: {having at least one active switching element 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 switching power converter is provided that detects an activity signal generated in response to load activity using an adaptively-declining threshold. ## Claims ### Claim 1 A switching power converter, comprising: a power switch coupled to a primary winding of a transformer; a controller configured to cease a cycling of the power switch responsive to processing a first reflected voltage produced at a transformer reset time after each cycling of the power switch, the controller being further configured to time a detection period beginning after a termination of a blankout period following a last cycle of the power switch; and a comparator configured to determine whether a second reflected voltage triggered by an activity detector coupled to a secondary winding of the transformer exceeds an adaptive threshold that declines during the detection period, wherein the controller is further configured to initiate an additional cycle of the power switch responsive to a determination by the comparator that the second reflected voltage exceeds the adaptive threshold, wherein the controller is configured to control the adaptive threshold such that it has a maximum value at an initiation of the detection period and such that it declines from this maximum value over the detection period until it is clamped at a minimum value. ### Claim 2 (depends on 1) The switching power converter of claim 1, further comprising an auxiliary winding configured to produce the first reflected voltage, the switching power converter further comprising a voltage divider coupled to the auxiliary winding, wherein the voltage divider is configured to produce the second reflected voltage. ### Claim 3 (depends on 1) The switching power converter of claim 1, wherein the comparator is configured to assert a fault alarm signal responsive to a determination that the second reflected voltage exceeds the adaptive threshold, and wherein the controller is further configured to trigger the additional cycle of the power switch responsive to the assertion of the fault alarm signal. ### Claim 4 (depends on 1) The switching power converter of claim 1, wherein the controller is configured to control the adaptive threshold such that it linearly declines from the maximum value to the minimum value. ### Claim 5 (depends on 1) The switching power converter of claim 1, wherein the controller is configured to control the adaptive threshold such that it stepwise declines from the maximum value to the minimum value. ### Claim 6 (depends on 1) The switching power converter of claim 1, wherein the power switch is a BJT power switch. ### Claim 7 (depends on 1) The switching power converter of claim 1, wherein the power switch is a MOSFET. ### Claim 8 (depends on 1) The switching power converter of claim 1, wherein the controller is further configured to time the detection period such that it begins after a blanking period terminates subsequent to the transformer reset time after the last cycle of the power switch. ### Claim 9 (depends on 8) The switching power converter of claim 8, wherein the controller is further configured to time the detection period such that the blanking period termination occurs while a resonant oscillation continues responsive to the last power switch cycle. ### Claim 10 A method, comprising: responsive to the removal of a load coupled to a secondary winding of a transformer, stopping the cycling of a power switch after a last power switch cycle, wherein the power switch is coupled to a primary winding of the transformer; after a blanking period has expired from a transformer reset time following the last power switch cycle, generating an adaptive threshold that declines as a function of a delay from a termination of the blanking period, wherein generating the adaptive threshold comprises generating an adaptive threshold that linearly declines until it is clamped at a minimum value; and detecting whether a reflected voltage on an auxiliary winding of the transformer exceeds the adaptive threshold, wherein the reflected voltage is generated by an activity detector coupled to the secondary winding. ### Claim 11 (depends on 10) The method of claim 10, wherein the blanking period that expired after the transformer reset time following the last power switch comprises a blanking period that expired while a resonant oscillation was still ongoing. ### Claim 12 (depends on 10) The method of claim 10, wherein detecting whether the reflected voltage exceeds the adaptive threshold comprises asserting a fault alarm signal responsive to the detection, the method further comprising: triggering an additional power switch cycle responsive to the assertion of the fault alarm signal. ### Claim 13 (depends on 12) The method of claim 12, wherein triggering the additional power switch cycle comprises triggering an additional cycle of a BJT power switch. ### Claim 14 (depends on 12) The method of claim 12, wherein triggering the additional power switch cycle comprises triggering an additional cycle of a MOSFET power switch. ### Claim 15 A switching power converter, comprising: an activity detector coupled to an output diode on a secondary side of a transformer, the activity detector being configured to activate a low impedance path bypassing the output diode in response to a detection of activity by a load, wherein the activation of the low impedance path triggers a current pulse in a secondary winding in the transformer; a power switch coupled to a primary winding of the transformer; and a controller configured to cycle the power switch responsive to a detection that a reflected voltage produced on an auxiliary winding of the transformer in response to the current pulse exceeded an adaptively declining threshold following a blankout period subsequent to a previous cycle of the power switch, wherein the adaptively declining threshold is a linearly-declining threshold. ### Claim 16 (depends on 15) The switching power converter of claim 15, further comprising: a comparator coupled to an auxiliary winding, the comparator configured to compare the reflected voltage produced by the current pulse to the adaptively declining threshold to produce the detection. ### Claim 17 (depends on 15) The switching power converter of claim 15, wherein the power switch is a BJT power switch.