Abstract: A voltage transformer for AC/DC comprising an IC having a rectifying unit with a function to transform AC of full waveform to continuous semi waveform, and a wave-filtering unit employing Gate transient voltage preset by Field Effect Transistor to proceed with filtering sample by ON and OFF method such that the preset voltage passes through the output terminal and achieves the effect of transformed voltage, and a voltage stabilizing unit which processes the output voltage for suitable utilization, wherein the sampling method of the AC with respect to Field Effect Transistor includes: (i) Fixed voltage sampling and (ii) Fixed time sampling method.

Abstract: A cooling fan dust guard has provided on the inner side of fan blades ribs and recess that mutually form an overcut height difference with a bushing opening so to prevent the airflow carrying dust an easy ingression and even keep off the flying dust from entering into the spindle.