DC power supply redundancy devices

The needs

The development of broadband telecommunications networks led to a widespread diffusion of decentralized network nodes (e.g. miniDSLAM VDSL2, MSAN, DPU...), typically installed in street side cabinets, and new needs to power feed them.

These network devices require a 48-60Vdc power supply obtained in different ways, the most common of which is a direct connection with the electric grid and the use of dedicated AC/DC converters with suitable features and low maintenance costs. The most used choice is a class II and category OVC4 AC/DC converter with a rated power of 420W.

In scenarios requiring a high rated power (e.g. MSAN multiservice nodes) or power redundancy to increase system reliability, it is necessary to use special devices that allow the aggregation of multiple DC power supply sources.

The aggregation and redundancy device must have features such as to minimize its dissipation and perform a balanced power delivery from all its inputs, even in presence of different voltage from the various AC/DC input converters.

The challenges

  • Symmetrical power delivery on all inputs with continuous balancing when varying load and voltages on individual input
  • High output current (up to 40A) and low thermal dissipation
  • Possibility of exclusion of inputs with out-of-range voltage
  • Alarm generation on dry contact and visual status indications
  • DIN-rail mounting and compact dimensions (reduced installation spaces)
  • Wide range of operating temperatures (street side cabinets exposed to the sun and bad weather)
  • Resistance to mechanical stress (vibrations on street installations)

The realization

RU0x series devices are aggregation and redundancy units for DC power sources with DIN-rail mounting, specially designed to meet the requirements of telecommunications applications.

The devices are available with a maximum operating voltage of 72V, a rated current of 10A for each input and a total rated output current of up to 40A for the RU04 model.

RU0x devices integrate electronic components and a MCU for the correct and continuous balancing of power delivery from the active inputs, and for the management of alarm and visual signalling.

The device continuously monitors the status of the inputs and outputs to maximize the overall efficiency and maintain the correct balance between the inputs of total required output power, even when load and voltages on individual inputs vary.

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