The present provides a secondary power
system and a power supply device. The secondary power
system is used for supplying power for a load equipment, and comprises: a fuse circuit, a filter circuit, a convertor circuit and an over-
voltage and under-
voltage protection circuit, wherein, the fuse circuit, the filter circuit, the over-
voltage and under-voltage protection circuit and the convertor circuit are sequentially connected in series; the over-voltage and under-voltage protection circuit is configured to
cut off power supplied to the convertor circuit when power supplied by the primary power source is an under-voltage or over-voltage; the convertor circuit is configured to convert the primary power source into a secondary power source. The secondary power
system, by providing an over-voltage and under-voltage protection circuit, can not only lower the cost of the convertor circuit, but also save the space occupied by the convertor circuit.