# US 2010/0165671 A1 · Switched-mode Power Supplies > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2010/0165671 A1 - Document ID: US20100165671A1 - Status: Published application - Kind: A1 - Application number: 12/492,451 - Filed: 2009-06-26 - Published: 2010-07-01 - Earliest claimed: 2008-06-30 - Assignees: Cambridge Semiconductor Limited - Inventors: David Robert Coulson; Antonius J.J. Werner; Vladimir Alexiev - Web page: https://patentgrep.com/patent/US20100165671A1 ## CPC - H02M 3/33523: {with galvanic isolation between input and output of both the power stage and the feedback loop} - H01F 27/324: {Insulation between coil and core, between different winding sections, around the coil; Other insulation structures} - H01F 27/38: Auxiliary core members; Auxiliary coils or windings - H01F 27/34: Special means for preventing or reducing unwanted electric or magnetic effects, e.g. no-load losses, reactive currents, harmonics, oscillations, leakage fields - 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) - H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES ## Abstract This disclosure relates to switched-mode power supplies, to transformers for such power supplies, and to methods of operating switched-mode power supplies. A switch mode power supply (SMPS), the switched-mode power supply having a power input, a switch, a transformer, and a power output; said transformer having a primary winding on a primary side of said power supply coupled to said power input via said switch, and a secondary winding on a secondary side of said switched-mode power supply coupled to said power output; wherein said transformer further includes first and second auxiliary windings, wherein said first auxiliary winding is more closely coupled to said primary winding than to said secondary winding and wherein said second auxiliary winding is more closely coupled to said secondary winding than to said primary winding. ## Claims ### Claim 1 A switch mode power supply (SMPS), said switched-mode power supply comprising a power input, a switch, a transformer, and a power output; said transformer comprising a primary winding on a primary side of said power supply coupled to said power input via said switch, and a secondary winding on a secondary side of said switched-mode power supply coupled to said power output; wherein said transformer further comprises first and second auxiliary windings, wherein said first auxiliary winding is more closely coupled to said primary winding than to said secondary winding and wherein said second auxiliary winding is more closely coupled to said secondary winding than to said primary winding. ### Claim 2 (depends on 1) A switched-mode power supply as claimed in claim 1 further comprising a controller to control said switch and a power supply circuit for said controller coupled to be powered by said first auxiliary winding. ### Claim 3 (depends on 2) A switched-mode power supply as claimed in claim 2 wherein said power supply circuit is configured to provide power to said controller when an output voltage of said SMPS falls to substantially zero. ### Claim 4 (depends on 1) A switched mode power supply as claimed in claim 1 further comprising at least one of a voltage clamping component and a voltage clamping circuit connected to the auxiliary winding, to thereby provide partial clamping of the switched primary winding. ### Claim 5 (depends on 1) A switched-mode power supply as claimed in claim 1 configured for primary side sensing of an output voltage of said SMPS, and wherein said primary side sensing is configured to employ said second auxiliary winding. ### Claim 6 (depends on 5) A switched-mode power supply as claimed in claim 5, further comprising a controller to control said switch, and wherein said controller is configured to sense a voltage on said secondary side of said SMPS by sensing a voltage on said second auxiliary winding. ### Claim 7 (depends on 1) A switched-mode power supply as claimed in claim 1 wherein said transformer further comprises a spacer to physically separate said first and second auxiliary windings from one another. ### Claim 8 (depends on 1) A switched-mode power supply as claimed in claim 1 wherein at least one of layers and turns of said primary winding and said first auxiliary winding are interleaved. ### Claim 9 (depends on 1) A switched-mode power supply as claimed in claim 1 wherein at least one of layers and turns of said secondary winding and said second auxiliary winding are interleaved. ### Claim 10 (depends on 1) A switched-mode power supply as claimed in claim 1 wherein said first and second auxiliary windings are electrically connected to one another. ### Claim 11 (depends on 1) A switched-mode power supply as claimed in claim 1 wherein said SMPS is a flyback SMPS. ### Claim 12 A method of providing a power supply to the controller of a switched-mode power supply (SMPS), said switched-mode power supply including a power input, a switch, a transformer and a power output; said transformer including a primary winding on a primary side of said power supply coupled to said power input via said switch, and a secondary winding on a secondary side of said switched-mode power supply coupled to said power output, wherein said transformer further comprises an auxiliary winding, in operation of said SMPS said auxiliary winding including a voltage waveform with a ringing component when said switch turns off, said ringing component comprising energy stored in leakage inductance and stray capacitance of said SMPS, the method comprising extracting energy to power said controller of said SMPS from said ringing component of said auxiliary winding voltage. ### Claim 13 (depends on 12) A method of providing a power supply to the SMPS controller as claimed in claim 12 wherein said SMPS comprises an output characteristic including a substantially constant current portion in which an output voltage of said SMPS falls towards zero at substantially constant output current with increasing output load, and wherein said energy is extracted from said ringing component as said output voltage falls to substantially zero. ### Claim 14 (depends on 12) A method of providing a power supply to the SMPS controller as claimed in claim 12 further comprising winding said auxiliary winding interleaved with said primary winding. ### Claim 15 A switched-mode power supply, said switched-mode power supply including a power input, a switch, a controller to control said switch, a transformer, and a power output; said transformer including a primary winding on a primary side of said power supply coupled to said power input via said switch, and a secondary winding on a secondary side of said switched-mode power supply coupled to said power output, and wherein said transformer further comprises an auxiliary winding to provide a power supply for said controller, in operation of said SMPS said auxiliary winding including a voltage waveform with a ringing component when said switch turns off, said ringing component comprising energy stored in leakage inductance and stray capacitance of said SMPS, said switched-mode power supply further comprising means for extracting energy to power said controller of said SMPS from said ringing component of said auxiliary winding voltage. ### Claim 16 A method of suppressing emissions from a switched-mode power supply (SMPS) said switched-mode power supply including a power input, a switch, a transformer, and a power output; said transformer including a primary winding on a primary side of said power supply coupled to said power input via said switch, and a secondary winding on a secondary side of said power supply coupled to said power output, wherein said transformer further comprises an auxiliary winding to sense a voltage on said secondary side of said SMPS, and wherein said SMPS includes a controller to control said switch in response to said sensed voltage, the method comprising winding said auxiliary winding interleaved with said secondary winding and coupling each of said secondary winding and said auxiliary winding to a reference voltage connection on respectively said secondary side and said primary side of said SMPS. ### Claim 17 A switched-mode power supply said switched-mode power supply including a power input, a switch, a transformer, and a power output; said transformer including a primary winding on a primary side of said power supply coupled to said power input via said switch, and a secondary winding on a secondary side of said power supply coupled to said power output, wherein said transformer further comprises an auxiliary winding, wherein said auxiliary winding is interleaved with said secondary winding, and wherein each of said secondary winding and said auxiliary winding is coupled to a reference voltage connection on respectively said secondary side and said primary side of said SMPS. ### Claim 18 A switched-mode power supply (SMPS) said switched-mode power supply including a power input, a switch, a controller to control said switch, a transformer, and a power output; said transformer including a primary winding on a primary side of said power supply and coupled to said power input via said switch, and a secondary winding on a secondary side of said power supply coupled to said power output, wherein said transformer further comprises an auxiliary winding to provide a power supply for said controller, wherein said SMPS comprises an output characteristic including a substantially constant current portion in which an output voltage of said SMPS falls towards zero at substantially constant output current with increasing output load, and wherein said power supply for said controller is configured to provide power for said controller as said output voltage falls from a maximum value at said substantially constant output current to a voltage of less than one third of said maximum value. ### Claim 19 (depends on 18) A switched-mode power supply as claimed in claim 18 wherein said power supply for said controller is configured to provide power for said controller as said output voltage falls from a maximum value at said substantially constant output current to a voltage of less than one tenth of said maximum value.