In-depth analysis of an RCD snubber applied to a DC-DC boost converter

摘要

Resistor-capacitor-diode (RCD) snubbers are traditionally used in practice aiming to maintain the stresses on semiconductors within safe operating limits. However, a serious drawback is the power lost in the resistor, which may affect the converter efficiency significantly. In this context, this work proposes a detailed procedure for the accurate design of an RCD snubber based on two additional key parameters that are not considered in typical guidelines provided in didactic books, that is, the forward recovery time of the main diode and the inductor current ripple. The impact of the maximum additional voltage spike on the switch is first assessed considering that it influences both the power dissipated in the snubber resistor and the current stresses on all semiconductors. A systematic optimization of the design is presented later on, considering that proper tradeoffs can be made among the type of main diode used in the converter, the maximum voltage spike on the switch, and the inductor current ripple as demonstrated mathematically. A dc-dc boost converter operating in continuous conduction mode (CCM) is thoroughly analyzed so that is possible to derive a consistent methodology comprising all power stage elements. This study intends to shed new light on an old research topic, as well to investigate the snubber impact on the converter operation and overall performance. The effectiveness of the proposed approach is demonstrated experimentally employing a laboratory prototype rated at 200 W. The results clearly show that is possible to optimize the design as desired, with good overall performance over a wide load range considering all aforementioned aspects.