| 摘要 |
A switch mode power supply is regulated using primary side sensing of a magnetic energy storage device such as a transformer (fig 1, 18). A voltage waveform signal Vaux from a winding such as auxiliary winding (fig 11, 26) feeds comparator 202, integrator 204, and timing circuit 206, 216. Integration takes place when waveform Vaux exceeds a reference voltage Vref, and integrator output Vint provides a control signal ZCINT to regulate output in response to a timing signal ZCDIFF that may be a peak or a trough of the waveform Vaux, detected by differentiator 206 and comparator 216. Comparator 214 may produce control signal ZCINT by comparing the integrated waveform Vint with another reference such as ground. The circuit may integrate a decaying portion of a feedback waveform (fig 3) followed by an oscillatory resonant portion when no energy is being transferred to the output, commencing from a point in the waveform defined by a target output voltage and generate an error signal when the differentiated waveform indicates a peak or a trough. The circuit is particularly used in a discontinuous conduction mode (DCM) SMPS. |
