Full-brick 700W DC-DC converters

7th December 2006
Posted By : ES Admin
Full-brick 700W DC-DC converters
UR has introduced the RFF series of isolated full-brick converters, manufactured by Artesyn Technologies and suitable for use with RF (radio frequency) power amplifiers. The new RFF series of converters comprises five 28V output models, offering a choice of two input voltage ranges and three output current ratings for optimum application flexibility. The range-topping RFF700 model is capable of delivering 25A at 28V (700W), yielding a power density in excess of 7.7 W/cm3.
All five models feature high power output capabilities and are rated for continuous operation across a wide temperature range, making them ideal for use with high-availability equipment deployed in demanding outdoor environments, such as cellular base stations and last-mile broadband systems.

RFF series full-brick converters are primarily intended for generating the regulated intermediate bus voltage in telecom systems that use a distributed power architecture. All five modules produce a nominal 28V DC output, which can be adjusted over the range 16.8 to 29.4V via a single resistor or a suitable control voltage.

The RFF500 and RFF600 have output current capabilities of 17.9A and 21.4A respectively, and both models are available with a choice of 24V nominal (18 to 36V) or 48V nominal (36 to 75V) inputs. The RFF700 handles output currents of up to 25A and has a nominal 48V (36 to 75V) input. All RFF series converters also feature a low voltage (7-10V DC) auxiliary output, which can supply up to 20 mA for power control signalling purposes.

A key advantage of RFF series converters is that they can be connected in parallel for high current applications and will automatically current share, without the need for any additional circuitry. As many as 11 converters can be connected in this manner, and by adjusting their output voltages to within 1%, users can obtain up to 95% rated current from each unit. This enables extremely high-power 28V DC sources to be configured very easily and cost-effectively. Simply by paralleling RFF700 models, for example, users can implement a power supply capable of delivering more than 260A – equating to 7.3 kW of fully regulated power.

RFF series full-brick converters are based on an advanced single forward topology, using ultra-fast recovery output diodes and a high fixed switching frequency of 1 MHz, to provide conversion efficiencies of up to 91% at full load. This minimises internal power dissipation, which simplifies thermal management and contributes to the converters’ excellent reliability. Feedback isolation is achieved without the use of opto-couplers, which helps maximise bandwidth to ensure excellent transient response and regulation characteristics. All five converters maintain line and load regulation to within ±0.54% and ±0.2% respectively.

The converters have an industry-standard full-brick pin-out and footprint of 11.7 x 6.1 cm, and an above-board height of 1.3 cm. They are packaged as fully encapsulated units intended for through-hole board mounting, and incorporate aluminium baseplate technology for conduction cooling. Various heatsink attachment methods are available, and the modules can be supplied with threaded or blank inserts to suit customers’ preferences.

RFF series converters carry a full set of international safety approvals – including EN60950 VDE, UL/cUL60950 and an IECEE CB Scheme test certificate and report, all of which help customers reduce system compliance costs and accelerate time to market. The converters are compliant to RoHS directive EU 2002/95/EC and utilise the lead in solder for telecoms, server and storage exemption.

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