Patent ID: 7551460
Filing Date: 2009-06-23
Classification: H02M

Abstract:
1. A switch mode power supply (SMPS) controller for regulating the output of a discontinuous conduction mode SMPS in response to a feedback signal from a winding of a magnetic energy storage device forming part of an output circuit of said SMPS, said feedback signal having a waveform with a decaying portion representing a decaying voltage in said output circuit of said SMPS followed by an oscillatory portion when substantially no energy is being transferred to said SMPS output, the SMPS controller comprising: a feedback signal input to receive said feedback signal waveform, said feedback signal waveform being responsive to a voltage on said winding; a first timing signal generator coupled to said feedback signal input to identify a first reference point in said feedback signal waveform at a transition between said decaying and oscillatory portions of said waveform and having an output to provide a first timing signal responsive to said identification; a second timing signal generator coupled to said feedback signal input to identify a second point located in said oscillatory portion of said feedback signal waveform and having an output to provide a second timing signal responsive to said identification; an area correlator coupled to said feedback signal input and to said first and second timing signal generator outputs, said area correlator being configured to compare an area under said feedback signal waveform between a start point defined by said first timing signal and an end point defined by said second timing signal with a reference and having an output to provide an error signal responsive to said comparison; and a controller output coupled to said area correlator output.