A circuit for power management on a circuit board , comprising: a first power connector coupled to a first power input rail and arranged to be selectively coupled to a second power input rail ; a second power connector ; wherein the second power input rail is arranged to be coupled to either the first power connector or the second power connector; and wherein the first and second power input rails are arranged to deliver power received through the first power connector and the second power connector to the circuit board; and a power control module configured to: determine a power specification of the circuit board ; determine how much power is being delivered through the first power connector ; sense a voltage at the second power connector ; wherein, if the sensed voltage at the second power connector is zero, and, if a total power supplied to the circuit board meets the determined power specification , the power control module is configured to couple the second power input rail with the first power connector, or otherwise if the total power supplied to the circuit board does not meet the determined power specification, the power control module is configured to decouple the second power input rail from the first power connector; and wherein, if the sensed voltage at the second power connector is nonzero, the power control module is configured to couple the second power connector to the second power input rail, provided that the total power supplied to the circuit board meets the determined power specification. a first power connector coupled to a first power input rail and arranged to be selectively coupled to a second power input rail ; a second power connector ; wherein the second power input rail is arranged to be coupled to either the first power connector or the second power connector; and wherein the first and second power input rails are arranged to deliver power received through the first power connector and the second power connector to the circuit board; and a power control module configured to: determine a power specification of the circuit board ; determine how much power is being delivered through the first power connector ; sense a voltage at the second power connector ; wherein, if the sensed voltage at the second power connector is zero, and, if a total power supplied to the circuit board meets the determined power specification , the power control module is configured to couple the second power input rail with the first power connector, or otherwise if the total power supplied to the circuit board does not meet the determined power specification, the power control module is configured to decouple the second power input rail from the first power connector; and wherein, if the sensed voltage at the second power connector is nonzero, the power control module is configured to couple the second power connector to the second power input rail, provided that the total power supplied to the circuit board meets the determined power specification. determine a power specification of the circuit board ; determine how much power is being delivered through the first power connector ; sense a voltage at the second power connector ; wherein, if the sensed voltage at the second power connector is zero, and, if a total power supplied to the circuit board meets the determined power specification , the power control module is configured to couple the second power input rail with the first power connector, or otherwise if the total power supplied to the circuit board does not meet the determined power specification, the power control module is configured to decouple the second power input rail from the first power connector; and wherein, if the sensed voltage at the second power connector is nonzero, the power control module is configured to couple the second power connector to the second power input rail, provided that the total power supplied to the circuit board meets the determined power specification. <EOS>