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.
1. A method comprising:
detecting a loss of a first input voltage source to a first power supply unit of a multiple power supply system, the multiple power supply system including the first power supply unit and a second power supply unit;
operating the first power supply unit in a reverse charging mode of operation in response to the loss of the first input voltage source;
charging a bulk capacitor of the first power supply unit while in the reverse charging mode of operation;
determining whether a voltage level of the bulk capacitor is equal to a threshold voltage level;
providing a lower charging cycle in the reverse charging mode of operation in response to the bulk capacitor being charged to a predetermined voltage level;
detecting a loss of a second input voltage source to the second power supply unit while the first input voltage source is lost;
operating in a hold up mode of operation in response to the loss of the second input voltage source and the first input voltage source being lost; and
providing an output voltage from the bulk capacitor while in the hold up mode of operation.
2. The method of claim 1 further comprising:
determining whether a standby power integrated circuit of the second power supply unit is off while the first power supply unit is in the reverse charging mode of operation; and
forcing the standby power integrated circuit to power off in response to determining that the standby power integrated circuit is not off.
3. The method of claim 2 wherein forcing the standby integrated circuit to power off protects components of the power supply unit while in the reverse charging mode of operation.
4. The method of claim 2 wherein forcing the standby integrated circuit to power off comprises:
turning on a transistor coupled to the standby integrated circuit to pull a working voltage of the standby integrated circuit to ground.
5. The method of claim 1 further comprising:
determining whether a high current is received in the first power supply unit; and
ending the reverse charging mode for a predetermined amount of time in response to determining that the high current is received in the first power supply unit.
6. The method of claim 1 further comprising:
operating the first power supply unit in a hot spare mode of operation in response to the reverse charging mode of operation ending and prior to resuming a normal mode of operation.
7. The method of claim 6 further comprising:
maintaining the voltage level of the bulk capacitor at the predetermined voltage level while operating in the hot spare mode of operation.
8. A method comprising:
detecting a loss of a first input voltage source to a first power supply unit of a multiple power supply system, the multiple power supply system including the first power supply unit and a second power supply unit;
operating the first power supply unit in a reverse charging mode in response to the loss of the first input voltage source;
charging a bulk capacitor of the first power supply unit while in the reverse charging mode;
determining whether a standby power integrated circuit of the second power supply unit is off while the first power supply unit is in the reverse charging mode;
forcing the standby power integrated circuit to power off in response to determining that the standby power integrated circuit is not off;
determining whether a voltage level of the bulk capacitor is equal to a threshold voltage level;
providing a lower charging cycle in the reverse charging mode in response to the bulk capacitor being charged to a predetermined voltage level;
detecting a loss of a second input voltage source to the second power supply unit while the first input voltage source is lost;
operating in a hold up mode in response to the loss of the second input voltage source and the first input voltage source being lost;
providing an output voltage from the bulk capacitor while in the hold up mode; and
operating the first power supply unit in a hot spare mode in response to the reverse charging mode ending and prior to resuming a normal mode.
9. The method of claim 8 wherein forcing the standby integrated circuit to power off protects components of the power supply unit while in the reverse charging mode.
10. The method of claim 8 wherein forcing the standby integrated circuit to power off comprises:
turning on a transistor coupled to the standby integrated circuit to pull a working voltage of the standby integrated circuit to ground.
11. The method of claim 8 further comprising:
determining whether a high current is received in the first power supply unit; and
ending the reverse charging mode for a predetermined amount of time in response to determining that the high current is received in the first power supply unit.
12. The method of claim 8 further comprising:
maintaining the voltage level of the bulk capacitor at the predetermined voltage level while operating in the hot spare mode.
13. The method of claim 8 further comprising:
maintaining, at a direct current to direct current converter, an internal voltage at a level that is slightly lower than a main output voltage.