Quasi-Resonant, Zero-Current Switching DC / DC Converters

摘要

Switching converters were introduced in the 1960s to achieve the reductions in size and weight promised by higher than line frequency operation. Initial products had switching frequencies of 20 - 30 kHz. By the late 1970s, with the advent of component improvements such as high-speed transistors, frequencies over 100 kHz were being achieved. Unfortunately, switching-related losses, which also increased with frequency, were becoming prohibitively high. Against this backdrop, the quasi-resonant, zero-current switching (ZCS) DC/DC converter was introduced with switching frequencies of 1 MHz, overcoming the frequency-related loss barrier. Each switch cycle delivers a quantized packet of energy to the converter output, with each switch turn-on and turn-off occurring at zero current, resulting in switch losses related only to current conduction, independent of frequency.