The fixed output DC regulated power source is composed of isolation transformer, bridge rectifier, large capacity filter, power tube or big power modular regulating circuit, protective circuit, it can work continuously for a long time with the function of sufficient output current, small wave, high stability, reliable performance, limited over-current protection and self-recovery. It is available for and places that requires DC power supply as laboratory, industrial control, telecommunication, electrical maintenance, accumulator charging, electrolysis and electroplating etc.