System and Method to Increase a Hold Up Time of a Power Supply Unit

A multiple power supply system includes first and second power supply units. The first power supply unit provides a main output voltage while in a normal mode of operation. The first power supply unit includes a first bulk capacitor, and first standby power circuitry. The first standby power circuitry provides a standby voltage while the first power supply unit is in the normal mode of operation. The second power supply unit provides the main output voltage while in the normal mode of operation. The first power supply unit includes a second bulk capacitor, and second standby power circuitry. The second standby power circuitry provides the standby voltage while the first power supply unit is in the normal mode of operation, and enables reverse charging of the second bulk capacitor by the first power supply unit while the second power supply unit is in a reverse charging mode of operation.