| High efficiency and power density are the trends of switching power supply. Theeffective methods are increasing switching frequency and switching speed, anddecreasing the volume of passive components. However, as switching speed enhanced,parasitic inductance influence can’t be ignored. On the one hand, parasitic inductancewill highly influence switching loss. On the other hand, parasitic inductance willinfluence the converter reliability. These problems reflect the parasitic influence onswitching characteristic. So the goal of this dissertation is to research the characteristicbased on the circuit parasitic inductance, which is benefit to power supply design. Thedetailed research aspects are as follows:Create a new switching loss model which takes the consideration of parasiticinductance. Output-diode reverse recovery, absorption circuit and nonlinearcharacteristic of power switch are also considered in the new model. The modelaccuracy is proved by Saber simulation.Research the constraint mechanism of MOSFET reliable work. Create analyticexpression of switching speed which takes the consideration of circuit parasiticparameters. Then derivate the value of driving resistance. Theoretical analysiscorrectness is varied by simulation.Analyze how the circuit parasitic parameters are being brought in and comparedifferent methods of parasitic parameters extraction. The accuracy of softwareextraction method is being verified. Research the influence of the PCB geometric sizeand angle on the results of parasitic parameters extraction.Set up the experimental platform and extract circuit parasitic. Then set up thecircuit simulation model. Compare the simulation waveforms with measuredwaveforms thus to verify the influence of parasitic elements on switchingcharacteristics. In order to further verify the accuracy of parasitic extraction, carry outtemperature-rise simulation. And compare it with test results thus to verify theaccuracy of parasitic extraction method. |
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