Switch mode power supply controllers
AssigneeCambridge Semiconductor Limited
InventorsMahesh Devarahandi Indika de Silva, Jay Kumar, Vinod A. Lalithambika
Life of this patent
Estimating the term…
Abstract
This invention generally relates to discontinuous conduction mode switch mode power supply (SMPS) controllers employing primary side sensing. We describe an SMPS controller which integrates a feedback signal from a point determined by a target operating voltage to a peak or trough of an oscillatory or resonant portion of the feedback signal when substantially no energy is being transferred to the SMPS output. When regulation is achieved this value should be zero; the difference from zero can be used to regulate the output voltage of the SMPS.
Claims18
A switch mode power supply (SMPS) controller for regulating the output of a discontinuous conduction mode (DCM) 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 an oscillatory portion when substantially no energy is being transferred to said SMPS output, the SMPS controller comprising:
- a reference level input to receive an output voltage reference level signal;
- a feedback signal input to receive said feedback signal, said feedback signal being responsive to a voltage on said winding;
- a first comparator coupled to said reference level input and to said feedback signal input and having an output responsive to a comparison of said reference level signal and said feedback signal;
- a timing signal generator coupled to said feedback signal input to identify a point in said oscillatory portion of said feedback signal and to provide a timing signal responsive to said identification;
- an integrator coupled to said feedback signal input and to said first comparator output and configured to start integration responsive to said comparison of said reference level signal and said feedback signal, to provide an integrated feedback signal output;
- a second comparator to compare said integrated feedback signal output at said time identified by said timing signal generator timing signal with a second reference value, and having an output to provide an error signal responsive to said comparison;
- and
- a controller output coupled to said second comparator output to provide a control signal for regulating said SMPS output responsive to said error signal.
An SMPS controller comprising:
- a winding signal input to receive a winding voltage waveform from a winding of a magnetic energy storage device of the SMPS;
- an integrator coupled to said winding signal input to integrate said winding voltage waveform;
- a reference voltage input to receive a reference voltage signal;
- a first comparator coupled to said winding signal input, to said reference voltage input and to said integrator to reset said integrator responsive to a comparison between said winding voltage waveform and said reference voltage signal;
- a timing circuit to generate a timing signal at a timing point in said winding voltage waveform;
- and
- a control output to provide an SMPS control signal responsive to a value of said integrated winding voltage waveform at said timing point.
A power converter comprising:
- a transformer and a switch that electrically couples and decouples the transformer to and from a power source;
- an event detection module for generating a reference voltage timing signal indicating when a primary or auxiliary winding flyback voltage waveform of the transformer substantially equals a reference voltage;
- an integration module for generating a signal indicating when said flyback voltage waveform has reversed phase starting from a timing point indicated by said reference voltage timing signal;
- a critical conduction point detector for generating a second signal indicating when a critical conduction point has been reached;
- and
- a phase detection circuit for generating an error signal which indicates a relative timing of an output of said integration module and an output of said critical conduction point detector.
Dependencies are inferred from the claim text.