Littleton, Mass.—Touting a step advance in miniaturization, XP Power's EMA212 draws on a collection of design techniques and technologies to deliver what the company claims is the world's smallest 212-watt, single-output AC/DC switching supply. The open-frame 12-volt (or 48-VDC) single supply, with a 5-volt, 100-mA standby output and a 12-volt, 1-amp output for powering a fan, fits onto a 3-by-5 inch board and in a 1U format for networking equipment, voice over IP systems, wireless LANs, servers, storage area networks and post-production broadcast equipment.
Techniques for compact design have been applied at virtually every stage. The EMA212's input filter comprises a 2-stage topology using miniature high permeability cores to save space. Additionally, the cores are stack-mounted to minimize the printed circuit board area and maximize cooling effectiveness. Its active power-factor-correction (PFC) stage uses a silicon carbide (SiC) diode to gain an additional 1 percent efficiency over traditional diode and snubber circuit combinations. A so-called stepped-gap inductor (i.e., a swinging choke, where the inductance is a function of operating current) operating in continuous mode reduces peak switching current and minimizes filter requirements. The PFC controller stage uses a one-cycle control (OCC) circuit, rather than relying on an average-current control mode. The OCC technique eliminates six passive components.
The main converter's resonant zero current switching (ZCS) topology virtually eliminates switching losses. Switching occurs at the zero current point from 0 to 100 percent load. The PWM control circuitry operates at a switching frequency of 100 kHz, which facilitates the use of sufficiently small magnetic components without compromising efficiency. Also in the main converter, a ceramic substrate replaces the conventional heat sink, thus offering additional space savings.
The same thermal management technique is applied to the output rectifiers. Here, synchronous rectification is used to minimize switching losses, keep noise levels low, and minimize both cost and board area.
The EMA212 features a line regulation of ±0.5 percent and a load regulation of ±1 percent on the main output, and ripple and noise of 1 percent. Transient response, for a 50 percent load change, is 500 microseconds for recovery to typically within 1 percent of nominal output voltage.
With efficiency over 90 percent at full load (for 230 VAC input), the EMA212 needs just 12 CFM air-flow for full power operation at up to +50°C ambient. It will operate at up to +70°C ambient with suitable derating, and thus minimize the need to rely on the system network architecture for cooling.
The unit incorporates a fully featured signal set including AC fail/DC OK, remote on/off and active current sharing. Over-current, over-voltage and short-circuit protection are all built into the EMA212 and the power supply meets all major international specification for safety and EMC performance.
Contact the company directly for the product datasheet.
The EMA212 is sampling now with production quantities available in September. Units are priced at $82 each for 1000 pieces. Contact Duane Darrow.
XP Power, 1-978-287-7260, www.xppower.com