New Oscillation Circuit Discovered in Switching-Mode Power Supplies

A new oscillation circuit has been discovered in switching-mode power supply (SMPS) circuits and is presented for the first time. The new oscillation circuit naturally exists in various SMPS, generates electric oscillation, and, as a result, causes high radiation noise. Small-signal analysis of the new oscillation circuit model was executed and analytical solutions of the oscillation criterion have been derived. Experimental measurements of the oscillation frequency in various circuits showed good agreement with the analytical solutions and proved the applicability of the new oscillation circuit model to SMPS circuits. Guideline for designing high-efficiency and low-noise SMPS is demonstrated together with guideline for designing low-loss and low-noise power MOSFET.