# US 9,438,127 B2 · Reverse current control for an isolated power supply having synchronous rectifiers > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,438,127 B2 - Document ID: US9438127B2 - Status: Granted - Kind: B2 - Application number: 13/947,820 - Filed: 2013-07-22 - Published: 2014-09-11 - Granted: 2016-09-06 - Earliest claimed: 2013-03-11 - Assignees: Analog Devices Global - Applicants: Analog Devices Technology - Inventors: Yingyang Ou; Qingyi Huang; Renjian Xie; Ling Ren - Web page: https://patentgrep.com/patent/US9438127B2 ## 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 certain example embodiments, a system is provided that includes a circuit. The system also includes a reverse current control module that provides an isolated power supply in order to protect one or more devices in a power chain during one or more testing activities having one or more requirements. ## Claims ### Claim 1 A power supply, comprising: a synchronous rectifier that rectifies an AC voltage to a DC voltage; a reverse current control module configured to generate a signal when an input voltage is lower than a threshold, the reverse current control module including a transistor and a shunt regulator, wherein, when a voltage across a reference pin of the shunt regulator is lower than an internal reference voltage of the shunt regulator, a cathode of the shunt regulator is changed to a high resistance status, resulting in the turning off of the transistor; and a control module that turns off the synchronous rectifier, after receiving the signal from the reverse current control module. ### Claim 2 (depends on 1) The power supply of claim 1, further comprising: an input power source that provides energy to a load, and an input filter that decouples a ripple interference from the input power source. ### Claim 3 (depends on 1) The power supply of claim 1, further comprising: a switch located on a primary side to invert an input DC voltage into an AC voltage. ### Claim 4 (depends on 1) The power supply of claim 1, further comprising: a transformer that isolates an input and an output. ### Claim 5 (depends on 1) The power supply of claim 1, further comprising: an output filter that smooths a DC voltage rectified by the synchronous rectifier. ### Claim 6 (depends on 1) The power supply of claim 1, wherein the reverse current control module senses an input voltage on a primary side and an output voltage on a secondary side. ### Claim 7 (depends on 1) The power supply of claim 1, wherein the reverse current control module includes an input voltage detector, an output voltage detector, and a compare module configured to compare one or more voltages. ### Claim 8 (depends on 7) The power supply of claim 7, wherein the input voltage detector includes an input for an input voltage sensing and an output coupled to the compare module. ### Claim 9 (depends on 7) The power supply of claim 7, wherein the output voltage detector includes an input for an output voltage sensing and an output coupled to the compare module. ### Claim 10 (depends on 7) The power supply of claim 7, wherein the compare module includes two inputs from the input voltage detector and the output voltage detector, and the compare module is configured to calculate a threshold based on an output voltage and at least one other parameter. ### Claim 11 (depends on 1) The power supply of claim 1, wherein an input voltage detector senses a voltage on both a primary side and a secondary side that reflects the input voltage or that has relationship with the input voltage. ### Claim 12 (depends on 1) The power supply of claim 1, further comprising: a compare module configured to perform a compensation for both the input voltage and an output voltage to calculate a correct input and output voltage value. ### Claim 13 (depends on 1) The power supply of claim 1, further comprising: a compare module that calculates a voltage threshold dynamically or sets the threshold as a predetermined value. ### Claim 14 (depends on 1) The power supply of claim 1, further comprising: a first block that decouples noise, and a second block that attains a certain delay time, wherein at least some portions of the power supply maintain an input signal and an output signal for a predetermined time. ### Claim 15 (depends on 1) The power supply of claim 1, wherein the control module is configured to disable one or more driving signals for the synchronous rectifier. ### Claim 16 (depends on 1) The power supply of claim 1, wherein the reverse current control module and the control module are implemented as an analog circuit, a digital circuit, a hybrid circuit, or software executed in a memory or in conjunction with a processor. ### Claim 17 (depends on 1) The power supply of claim 1, further comprising: a compare module that senses the input voltage on a primary side. ### Claim 18 (depends on 1) The apparatus of claim 1, wherein, when the voltage across the reference pin of the shunt regulator is higher than the internal reference voltage of the shunt regulator, the cathode of the shunt regulator leads to a saturation of the transistor. ### Claim 19 A method, comprising: sending a first signal from a reverse current control module to a control module when an input voltage is lower than a threshold, the reverse current control module including a transistor and a shunt regulator, wherein, when a voltage across a reference pin of the shunt regulator is lower than an internal reference voltage of the shunt regulator, a cathode of the shunt regulator is changed to a high resistance status, resulting in the turning off of the transistor; and sending a second signal from the control module to turn off a synchronous rectifier, in response to the first signal. ### Claim 20 (depends on 19) The method of claim 19, wherein the first signal is sent when an input voltage dips. ### Claim 21 (depends on 19) The method of claim 19, further comprising: sensing the input voltage on a primary side and an output voltage on a secondary side; and calculating the threshold based on at least the output voltage. ### Claim 22 (depends on 19) The method of claim 19, further comprising: compensating a voltage plateau to achieve a value for the input voltage. ### Claim 23 A method implemented by a power supply, the method comprising: rectifying, with a synchronous rectifier, an AC voltage to a DC voltage; generating, with a reverse current control module, a signal when an input voltage is lower than a threshold, the reverse current control module including a transistor and a shunt regulator, wherein, when a voltage across a reference pin of the shunt regulator is lower than an internal reference voltage of the shunt regulator, a cathode of the shunt regulator is changed to a high resistance status, resulting in the turning off of the transistor; and turning off the synchronous rectifier, with a control module, after the control module receives the signal from the reverse current control module. ### Claim 24 (depends on 23) The method of claim 23, further comprising: sensing the input voltage on a primary side and an output voltage on a secondary side; and calculating the threshold based on at least the output voltage.