The invention relates to a high voltage and low voltage switching circuit for an LLC (Logical Link Control) conversion output. The high voltage and low voltage switching circuit comprises an output end, n transformer secondary sides, n rectifiers and a selection switch, wherein n is larger than 1; two ends of the n transformer secondary sides are connected with an alternating-current side of an nth rectifier; a low voltage end of a direct current side of an mth rectifier is connected with a high voltage end of a direct-current side of an (m+1)th rectifier; m is larger than 0 and smaller than n; and the selection switch is used for adjusting the magnitude of an output voltage of the output end by selection of the number of the rectifiers accessing the output end. According to the technical scheme, the number of the rectifiers accessing the output end can be controlled through the selection switch, and the magnitude of the output voltage at the output end is adjusted, so that the problem that an LLC converter output voltage is non-adjustable is solved.