AC-DC power

Emerson Network Power has launched a digitally controlled 500 W AC-DC supply that offers a power density of 0.7 W per cm3.

The Astec NTS503 has a 10.2 x 17.8 cm footprint, making it easy for OEMs to incorporate a single unit that satisfies all their bulk DC power needs and offers a choice of convection or forced-air cooling.

The convection-cooled model has an output of 200 W and a height of 3.8 cm.

Intended primarily as medium power front-end units for distributed power systems, the small physical size and high functionality makes them especially suitable for use in information technology equipment and light industrial systems.

The supplies are also available with medical approvals, for applications such as patient monitoring systems and other portable equipment used in medical wards and operating theatres.

The units supply tightly regulated 12 V output that can be used to directly power boards fitted with multiple non-isolated point-of-load DC-DC converters. The convection cooled model can deliver up to 16.6 A and the forced-air version can deliver up to 41.7 A.

Both versions also provide an auxiliary 'always-on' regulated 5 VDC at 2 A output for applications that require standby operation, as well as a 12 V output for powering fans.

The supplies feature a universal input that accepts any voltage from 85 to 264 VAC at any frequency from 47 to 440 Hz, enabling them to be used in equipment destined for any part of the world. Active power factor correction minimises input harmonic current distortion and ensures compliance with the international EN61000-3-2 standard.

The supplies employ the latest high-frequency switchmode technology to maximise conversion efficiency, typically achieving 85% at full load with a nominal 115 VAC input.

Built-in control and monitoring features include 'AC power fail' and 'DC OK' output signals and a remote on/off input, and the supplies are protected against overvoltage, short-circuit and overtemperature conditions. Single-wire current sharing is available as standard, and the power supply incorporates an internal O-ring diode on its main 12 V output, for fault-tolerant and N+1 redundancy applications.

The main 12 V output can be adjusted 5% either side of nominal via an internal trim potentiometer or through the digital interface, and regulation is maintained to within ±2% for all line and load conditions. Differential remote sense facilities are provided to compensate for up to 0.5 V drop between the output terminals and the load.

The auxiliary 5 VDC output is regulated to within ±5% and can deliver up to 2.0. It is primarily intended for powering 'standby' circuitry that needs to remain on for most of the time, such as power-up/down sequencers, and is unaffected by the on/off status of the main 12 V output. The auxiliary 12 V fan output can deliver up to 1 A, or up to 0.5 A on the forced-air version, and is present whenever the main 12 V output is on.