Method and apparatus for distinguishing between failure of a power supply versus failure of its power source from the secondary of the power supply

A power loss detection system of a power system for distinguishing between failure of a power supply versus failure of a power source, comprising:

• at least one power supply for receiving power from the power source, comprising:
• a main converter for converting source power from the power source to regulated power and for providing regulated power;
• an activation circuit coupled to said main converter and receiving an active low activation signal, wherein said activation circuit turns on said main converter when said activation signal is asserted low, but otherwise turns off said main converter;
• a standby power circuit for providing low secondary power on a standby power signal whenever the power source is providing power;
• and
• a current device coupled between said standby power circuit and said activation circuit for pulling said activation signal to said standby power signal when said activation signal is not otherwise asserted low;
• a detection circuit for monitoring said regulated power and for asserting a power status signal indicative thereof;
• and
• a control circuit for asserting said activation signal low to turn on said main converter, for floating said activation signal to turn off said main converter, and for monitoring said activation and power status signals, wherein if said power status signal indicates loss of said regulated power, said control circuit floats said activation signal to determine whether said standby power circuit is enabled;
• wherein said activation signal being low indicates that the power source has failed and said activation signal being high indicates that said power supply has failed.

A redundant power supply system for providing power to an electronic device, comprising:

• first and second power sources for providing first and second unregulated source signals;
• first and second power supplies coupled to said first and second power sources, respectively, for converting said first and second unregulated source signals to regulated power on first and second power buses, respectively, each power supply comprising:
• a main converter for converting received unregulated source power to regulated power and for providing said regulated power on a power bus;
• an activation circuit coupled to said main converter and receiving an active low activation signal, wherein said activation circuit turns on said main converter when said activation signal is asserted low, but otherwise turns off said main converter;
• a standby power circuit for providing secondary low power on a standby power signal whenever said received unregulated source power is available;
• and
• a pullup device coupled between said standby power circuit and said activation circuit for pulling said activation signal to said standby power signal when said activation signal is not asserted low;
• first and second detection circuits coupled to said first and second power supplies, respectively, for monitoring said first and second power buses and for asserting first and second power status signal indicative of regulated power on said first and second power buses, respectively;
• and
• a control circuit for asserting said first and second activation signals low to turn on said main converter of said first and second power supplies, respectively, for floating said first and second activation signals to turn off said main converter of said first and second power supplies, respectively, and for monitoring said first and second activation and power status signals, wherein if a power status signal indicates loss of regulated power on a respective power bus, said control circuit floats a corresponding one of said first and second activation signals to determine whether a corresponding standby power circuit is enabled;
• wherein if said corresponding one of said first and second activation signals remains low, then the corresponding power source has failed and if said corresponding activation signal goes high, the corresponding power supply has failed.