It used to be that compact dc/dc brick supplies were only something common to 48-V telco applications. That changed recently with the development of something called the Cool Power PI3106.
It is an isolated dc/dc converter targeting 24-V industrial and 28-V military applications. According to the developer, Vicor Corp., the device uses a Zero Voltage Switching (ZVS) architecture, state-of-the-art planar magnetics, and ultra-high density Power System in Package (PSiP) packaging.
The PI3106 uses about 50% less board space than equivalent designs, thereby allowing for power conversion closer to the point-of-load. It also works at a high switching frequency (900 kHz) which cuts the input filter and output capacitance requirements.
The converter chips occupy a little over a half-square-inch. A Cool-Power PSiP (power system on a chip) module consisting of a controller, transformer, and FETs occupies just 0.57 in2, a little less than half the board area of conventional approaches. Power density 334 W/in3, about three times that of conventional modules, claims Vicor.
The input range on the 24-V devices is 18 to 36 V; on the 28-V chips it is 16 to 50 V (for MIL-COTs). The operating temperature range is -400 to 1,250°C, -550 to 1,250°C for MIL-COTs. Regulated output is –12 V/4.2 A (±3% over line/ load/temperature). Efficiency exceeds 88%.
More info, Vicor Corp.: http://www.vicorpower.com/