Abstract: In a complex power distribution network (e.g. CATV), a switching mode power supply at a node, automatically recovers from low input voltage conditions. When the input voltage to a switching power supply decreases to a critical level, the output voltage is no longer regulated and input current increases, and then the network becomes unstable. The network can enter a quasi-stable high current condition in which the output voltage remains unstable. In one specific embodiment, an automatic shut down circuit senses the unstable condition (or a voltage or current indicating the potential for instability) and latches the power supply into a shut down state. After a predetermined pause (that may depend on the input voltage), the power supply automatically restarts. Upon restarting, if the power supply is still unstable or potentially unstable, then the shut down circuit shuts the power supply down again and so forth.