With the development of information technology, the demand for data processing equipments such as server computers and telecom apparatuses is gradually increasing and they have become a large market for power supply industry. The power system for these equipments need the high reliability and high maintainability since an interruption of the power supply causes a large cost.
To meet these requirements, parallel operation of power supply units (PSUs) is widely employed for data processing equipments. In general, the parallel power system can provide advantages such as the high-current capacity, simple thermal management, and easy standardization compared with a large single power supply. Especially, the parallel power system can cope with a sudden failure of an arbitrary PSU by adding one redundant PSU to N PSUs handling the rated power. Besides, the parallel power system can provide high maintainability since the broken PSU can be replaced with a new PSU without shutting down the whole system by the hot-swap.
In this dissertation, control methods to improve reliability and efficiency of the parallel power system are studied. The hot-swap is the operation which inserts a new PSU to the powered system. Therefore, the load current can be concentrated to the new PSU by the interaction among paralleled PSUs. To prevent the current concentration, a start-up control is proposed. Also, in the parallel power system with N+1 redundancy, each PSU has more chance to operate at light loads since the number of PSUs which share the load current is increased. Therefore, to improve the light load efficiency, a PFC on/off control is proposed.
1. Start-up control for reliable hot-swap of parallel power system
To make the maintenance, repair, and upgrade of the parallel power system simple, a hot-swap which means the replacement of a PSU without shutting down the whole system is necessary. A practical issue for the hot-swap is a current concentration toward a newly activating PS...