Power Supplies Pack 27 W/In³ in 1U Space

Jan 17, 2007 4:06 PM
by David Morrison, Editor, Power Electronics Technology

A series of front ends/rectifiers from Cherokee International delivers 2500 W of output in a 1U format, achieving a power density of 27 W/in.³. These units, which measure 1.61 in. by 4.00 in. by 14.25 in, offer twice the output power of existing units in the same format according to the vendor. As many as four CAR2500 power supplies may be placed side-by-side in a 1U shelf to provide up to 10,000 W of output or 7500 W of N+1 redundant power. In addition to high power density, the supplies offer high efficiency, multiple options for communications interfaces, hot swappability, and the ability to start up in cold environments.

The CAR2500 is designed as a customizable power platform—a flexible building block to satisfy various OEM power applications including network routers and switches, enterprise servers, telecommunications equipment, and industrial ATE applications. A choice of +48-V output at 52 A (the CAR2548FP front end) or -54-V output at 46.3 A (the CAR2548TN rectifier) supports the most common DPA architectures used in these applications. In addition, a version with +12-V output (the CAR2512FP front end) will be available soon. These units also permit adjustment of the output voltage over the specified ranges.

Beyond the output voltage options, the CAR2500 series is customizable in terms of its communications interface. The power supplies support interfaces such as I²C, PMBus, CAN, and Ethernet, which are implemented via corresponding “personality cards.”

An onboard microcontroller equipped with a 10 bit A-to-D converter facilitates a number of other features such as accurate temperature, current, and voltage sensing. In addition, automatic fan speed control regulates the internal supply temperature for increased reliability and audible noise control. This capability enables -10ºC to +70ºC operation and also a -40ºC startup capability. The latter is ideal for uncontrolled environmental conditions such as outdoor telecom equipment, RF amplifiers, and wireless applications.

To achieve high efficiency—about 92% efficiency at 48-V output—Cherokee employs a number of circuit design techniques. These include a proprietary PFC circuit with zero-voltage switching; a 400-kHz switching frequency (which allows use of a small output choke with low core and copper losses); and a proprietary clamp circuit across the output diodes for the units with 48-V and -54-V outputs.

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© 2007 Penton Media, Inc.