| US 7,567,445 B2 | ||
| Switch mode power supply controllers | ||
| David Robert Coulson, Comberton (United Kingdom); Johan Piper, Cambridgeshire (United Kingdom); and David M. Garner, London (United Kingdom) | ||
| Assigned to Cambridge Semiconductor Limited, (United Kingdom) | ||
| Filed on Jun. 01, 2006, as Appl. No. 11/445,473. | ||
| Prior Publication US 2007/0274106 A1, Nov. 29, 2007 | ||
| Int. Cl. H02M 3/335 (2006.01); H02M 1/12 (2006.01) | ||
| U.S. Cl. 363—21.12 [363/41] | 17 Claims |
| 11. A system for sensing an output voltage of an SMPS, the SMPS including a switched magnetic energy storage device for conveying
power from an input to an output of said SMPS, said magnetic device having at least one winding, the system comprising:
means for inputting a sensing signal from said at least one winding of said magnetic device, said sensing signal having a
waveform with a first, decaying portion during which power is supplied by said magnetic device to said SMPS output and a second
portion during which substantially no power is supplied by said magnetic device to said SMPS output;
means for identifying a knee point on said sensing signal waveform between said decaying portion and said second portion of
said waveform; and
means for using a value of said sensing signal at said knee point to sense said SMPS output voltage; and
wherein said means for said identifying of said knee point comprises:
means for fitting an approximate tangent to said decaying portion of said sensing signal waveform; and
means for identifying departure of said sensing signal waveform from said approximate tangent to identify said knee point,
wherein said means for identifying includes means for comparing said tangent approximating signal and said sensing signal
waveform to identify a time when said sensing signal waveform departs from said tangent approximating signal to identify said
knee point.
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