So what's happening in medium-sized power supplies? These days, the power output is the only thing that's medium-sized as these smaller devices provide more power density.
Aimed primarily at the telecom market, XP Power's 12-, 24-, and 48-V dc output MFA350 may hold the current record for the world's smallest 350-W supply, cranking out 11.2 W/in.3 in its base version. That's 364 W across the entire 90- to 264-V ac input range from a 3.2- by 6.8- by 1.5-in. U-bracket package (see the figure).
A 48-V dc input version is additionally available. Outputs include 12 V at 1 A for a fan and 5 V at 0.3 A for standby power. The fan requirement is a modest 13 cubic feet/minute (CFM). Available now, the MFA350 costs $175.00 in OEM lots.
The slightly larger Emerson Network Power Astec NTS503 universal-input 12-V supply boasts 500 W and 11.9 W/in.3 The tradeoff for the extra 150 W is cooling-air volume: 30 CFM. With only convection cooling, maximum output is 200 W. Both versions provide an auxiliary "always-on" regulated 5 V dc at 2-A output for applications that need standby operation and a 12-V output for powering fans.
Now that Emerson has acquired Artesyn, it's no surprise that control and telemetry comply with the PMBus standard. The NTS503 can monitor temperature, output voltage, and current with limited (5% either side of nominal) control of VOUT. Pricing starts at $299 for ITE/industrial models and $325 for medical models, in production quantities.
In a similar but deeper 1U/2U configuration (10.25 in.), Excelsys Technologies' Xlite series delivers up to 600 W at 10.5 W/in.3 Three different chassis provide system power levels of 200, 400, and 600 W. These chassis may be populated with any combination of four output modules from a range of seven types offering nominal outputs from 2.5 to 48 V dc. All of the output modules may be user-adjusted over a wide range to meet end-system requirements. For pricing, contact the company.