A rack-mounted DC power-supply system utilizing Li-ion batteries, which have higher energy density than conventional VRLA batteries, was developed. The system was designed to have the management functions of Li-ion batteries, such as overcharge protection, over-discharge protection, and cell-voltage equalization, by taking operational requirements into consideration. The volume and weight of the entire system were decreased to one-fourth and three-fifths, respectively, of the volume and weight of a conventional system, making the proposed system ideal as a high-energy-density backup power supply. The functions, system configuration, and characteristics of this rack-mounted DC power supply system utilizing Li-ion batteries are described.

We describe a simulation method and design for a stand-alone hybrid power supply system composed of a wind turbine generator and photovoltaic modules. The system has been developed to supply power for telecommunications equipment in areas with no commercial power sources. We also report a comparison of the simulation results with actual measured data. The results show that the hybrid system can function effectively as a power supply for telecommunications equipment.

This paper describes the design concept and characteristics of a power supply for optical network units in Fiber To The Home (FTTH) systems. Powering architectures of local powering, network powering and power hub powering are compared in terms of cost and maintainability. A local powering architecture is selected for an ONU power supply because it is the most cost-effective overall compared with the others. The local power supply is mainly composed of a rectifier, DC-DC converters, a ringer, and batteries. A battery deterioration test function is important for the local power supply because battery lifetime varies depending on ambient temperature, discharge history, and charging conditions, and it is shorter than other electrical components used in ONU. Supplying power using alternative batteries is also necessary because the capacity of batteries installed in the power supply is limited. These functions and electrical characteristics are checked using an experimental power supply with Ni-Cd batteries.

A distributed power supply system with highly efficient characteristics has been developed to replace conventional centralized power systems in telecommunications offices. In this system as in conventional centralized power systems, a stand-by energy system composed of batteries and engine-generator sets is used as a back-up system for the commericial power lines. However, the distributed power system, except for the engine-generator set, is installed in the telecommunications room. Thus, the floor load limitation is an important design factor. This paper describes a stand-by energy system design that considers floor load conditions and is based on reliability analyses. These analyses show that the distributed power system should be designed as follows: (1) Using a fully duplicated engine-generator set. (2) With battery reserve time reduced to one sixth that of conventional centralized power systems. (3) With transfer switch unavailability designed to be less than one half of the existence switch unavailability.

This letter describes an analysis of a series resonant converter in which the effects of the output transformer's magnetizing inductance on the converter's output characteristics are considered. It is clarified that the output power decreases when the magnetizing inductance has a low value.

A UPS with an energy storage function using long-cycle-life VRLA batteries has been developed. Combining the functions of UPS and energy storage is effective to enhance the cost-effectiveness of the UPS. New long-cycle-life VRLA batteries, with capacities of 1000 or 1500 Ah at 2 V, have been developed for the UPS. A cycle life of 3000 or more cycles was estimated from our cycle test. The UPS has been installed in a telecommunications building for field-testing. This paper describes the system configuration, electrical characteristics of the UPS and its components, and result of our field test.

The proposed high-power-factor converter is constructed with a flyback converter, and locates the energy-storage capacitor on the secondary side of the transformer. A high power-factor can be obtained without needing to detect any current, and the ZVS operation can be achieved without auxiliary switches. To make the best use of these advantages in the converter, ZVS operations and power-factor characteristics in the converter were analyzed. From the analytical results, the effective control method for achieving ZVS was examined. Using a bread-board circuit controlled by this method, a power-factor of 0.99 and a conversion efficiency of 88% were measured.

The designed converter has a two-input-winding transformer powered by single-phase AC voltage and an energy storage capacitor. Small size and enhanced conversion efficiency are achieved, because more than half of the energy is supplied to the load via a single conversion stage, and fast output-voltage regulation is achieved by controlling the charging and discharging of the storage capacitor. The design and control methods for the converter take into account the reset conditions of the transformer and stability in the output voltage control. An almost unity power factor and a low output voltage ripple were achieved with this converter fabricated as a breadboard circuit using small capacitors.

This paper describes a new configuration and control method for an uninterruptible power supply (UPS) with a bidirectional cycloconverter. When commercial AC power is operating normally, the load is supplied by commercial AC power and the bidirectional cycloconverter operates as a battery charger. During interruptions of commercial AC power, the bidirectional cycloconverter operates as an inverter and supplies AC power to the load. Unlike a conventional UPS, this new configuration does not require a battery charger, so it can be small, light-weight, cost-effective, and highly efficient. The output voltage characteristics and the transient voltage drop in the output when commercial AC power fails are also discussed by numerical analysis and experiments.

This paper describes the characteristics of lithium-ion cells developed for stationary use, as in the case of stand-by sources in power systems. The effect of a cell-voltage-equalizing circuit developed for batteries of cells is also demonstrated. The tested lithium-ion cells were suitable to be charged by the constant-current, constant-voltage (CCCV) method and could be charged efficiently over a wide range of temperatures. They also showed good discharge performance with little dependence on the discharge current and temperature. Total capacity reduction of over 60% can be expected in batteries of lithium-ion cells. The cell-voltage-equalizing circuit was shown to be useful and necessary for batteries of lithium-ion cells in order to suppress deviations in the cell voltage and capacity loss.