Sinrace Power Supply Technology (Shenzhen) Co., Ltd.

FPA is a response to the limitations of conventional distributed power. Current FPA products include the voltage transformation module (VTM), which is in some ways a point-of load (POL) alternative, and the pre-regulator module (PRM). Enhanced versions of both combine to make the PFM.

VTMs, which arrived in April 2003, are more sophisticated-than their conventional non-isolated POL brethren. They can function as either a step-up or step-down dc-dc transformer and can operate on a voltage significantly higher than the usual 12-V distributed on an IBA bus. A loop regulates the VTM's output by controlling input voltage.

Since the VTM isn't switching into an inductance, it can respond virtually instantaneously to a changing load. As a result, with a VTM, designers need less bulk capacitance to support fast load di/dt changes. Moreover, they can place the bulk capacitance needed for energy storage ahead of the VTM, thereby dividing it by the square of the VTM step-down ratio. Finally, a VTM, although more complex than an IBA POL, operates vastly more efficiently at high step-down ratios. This, in turn, permits the use of higher bus voltages.

We followed up the VTM with the announcement of a PRM, a dc-dc converter module crafted to work with its VTMs. A PRM generates a controlled bus voltage typically several times higher than an intermediate bus voltage, resulting in lower voltage drops and reduced I²R losses on the bus.

The VTM's and PRM's isolation functions are reversed from the roles of the POL and upstream converter in the IBA. The VTM at the point of load provides isolation, not the PRM. Therefore, system designers can locate the regulation function anywhere in the system.

WHAT THE PFM ADDS
The new PFM contains what we call an adaptive VTM plus a microprocessor-controlled PRM. The adaptive VTM steps down the rectified line voltage, which is then sent to a special kind of PRM.

The VTM is "adaptive" in the sense that it automatically configures its own step-down ratio based on where it's being used. If the input is in the range of 90 to 132 V ac, as it would be in North America or Japan, the VTM parallels its input cells. If the input is between 180 and 264 V ac, as it would be in the rest of the world, it connects its input cells in series. Adaptability makes possible an improvement over conventional ac-dc converters, which take an efficiency hit of around 3% when wrangling with the ac mains in Japan or North America.

The PRM in the PFM is like our earlier PRMs, but with power-factor correction. This is provided by an on-board microcontroller that monitors the PRM and adaptive VTM outputs to generate a control signal to an in-module ASIC. The ASIC both regulates the output and provides shaping of the module input current to achieve power-factor correction.