Using FPA: Why Factorize?

Small size—more power in less space

V•I Chips are the smallest power components available today — about the size of a 1/16 brick — and very power dense. VI BRICKs, which are based on V•I Chips, are also highly efficient and utilize advanced packaging to facilitate thermal management, mounting and soldering operations. Either can be used as building blocks to replace existing circuits (quarter bricks and silver box power supplies). Factorized Power means more space at the point(s) of load: one-half the power dissipation and the regulation function can be remotely located.

Flexibility — more options for designing a power system

One of the key objectives of factorized power and VI BRICKs is to increase power system flexibility. In DPA, DC-DC converters bundle the three classic converter functions (isolation, transformation and regulation) into bricks that are no longer adequate in terms of performance or cost-effectiveness. In IBA, non-isolated POL converters forego isolation and high-ratio voltage transformation to improve cost-effectiveness. But they depend upon a nearby bus converter to supply power at a low input voltage and expose overvoltage sensitive loads to deadly faults and ground loops.

Families of VI BRICK BCMs, VTMs and PRMs, optimized for different nominal input and output voltages, and packaged for power capabilities, provide power systems designers with a stable of power conversion components that can be used to economically solve a virtually limitless variety of power conversion problems. Complex systems can use combinations of VI BRICKs in a variety of control modes to rapidly configure high-density, low-profile solutions that minimize the need for external components, are cost-effective and highly efficient, and provide state-of-the-art performance.

VI BRICKs provide isolation and regulation where they are needed. You can put the VTM at the point of load and the PRM alongside or remotely, in the backplane or on a daughtercard.

FPA systems with a multiplicity of input and output voltages may actually have fewer unique components compared to a brick-based equivalent. With the VTM you use the same device no matter what the input voltage; with the PRM you use the same device no matter what the output voltage. There’s a continuum of output voltages available.

You can design new systems with PRMs and VTMs or retrofit existing architectures. Figs. 12, 13, 14 and 15 illustrate a few of the design options.

Figure 12 - High-current, low-voltage supply Click image for larger view

Figure 13 - High-voltage outputs Click image for larger view

Figure 14 - High-power arrays Click image for larger view

Figure 15 - Multiple outputs Click image for larger view

Efficiency — more power for the load, less heat left behind

Both the VI BRICK PRM and VTM can achieve higher than 97% efficiency. Overall efficiency for a power system – including the combination of a PRM and a VTM – operating from an unregulated DC source and supplying a low-voltage DC output typically ranges from 90% to 95%. In many cases, it is possible to achieve overall efficiency exceeding 95% even at full load. With higher efficiency comes lower total heat dissipation, another important consideration in power systems design.

VI BRICKs offer flexible thermal management: a low thermal impedance package and the design of the VI BRICK package simplifies heat sink design and thermal management.

Fast Transient Response — providing more power for fast changing loads

Many of today’s loads require not only higher current but faster transient response. VTMs respond to load changes, regardless of magnitude, in less than one microsecond with an effective switching frequency of 3.5 MHz. This is 20 times faster than the fastest competitive brick. (see Fig. 16).

Figure 16 - Fast transient response Click image for larger view

The VTM's high bandwidth obsoletes the need for massive point-of-load bypass capacitance. Even without any external output capacitors, the output of a VTM exhibits a limited voltage perturbation in response to a sudden power surge. A minimal amount of external bypass capacitance, in the form of low ESR / ESL ceramic capacitors, suffices to eliminate any transient voltage overshoot.

Architecture — IBA, niPOLs and VI BRICKs

IBA has proven effective as an interim method of containing power system cost while addressing the trend toward a proliferation of lower load voltages. IBA relies on non-isolated point-of-load regulators (niPOLs), reducing the POL function to regulation and transformation. The niPOLs operate from an intermediate bus voltage provided by upstream isolated converters. However, traditional IBA has inherent limitations that require trade-offs between distribution and conversion loss and that limit responsiveness to rapid load changes. VI BRICK BCMs can be used to solve these problems and several others.

Conclusion

FPA and VI BRICKs offer a power conversion architecture and enabling power building blocks that overcome these limitations while providing higher performance in every critical system specification. Factorized power, in fact, maximizes the competitiveness of a power system by providing the highest degree of system flexibility, power density, conversion efficiency, transient responsiveness, noise performance, and field reliability.