Main and standby power supply automatic switch -over circuit is prevented pouring in down a chimney in low pressure drop

The utility model discloses a main and standby power supply automatic switch -over circuit is prevented pouring in down a chimney in low pressure drop, including first power and second source to and install two field effect transistor between first power and second source seat, and meeting a resistance protection field effect transistor respectively in two field effect transistor's outside, and increase a diode and prevent that first power and second source from passing through resistance and linking to each other, the input of first power has a stabilivolt, and set up two triodes between first power and second source. The utility model provides a current main and standby power supply switching mode prevents flowing backward the problem, protects two way powers not influence each other, simultaneously, reduce the pressure drop problem that has main and standby power supply switching mode now, reduce the influence of switching circuit to power efficiency. 本实用新型公开了种低压降防倒灌主备电源自动切换电路，包括第电源以及第二电源，以及安装于第电源与第二电源座之间的