Switched-mode Power Supplies

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.

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.

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.

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.

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.