DC-DC ConvertersSponsored by: DATEL

Jan. 12, 2004
The Basics Of Using DC-DC Converters

The Black Box. Put succinctly, dc-dc converter modules make it easier to implement on-board voltage conversion.They integrate all required power-conversion circuitry into a compact package that can be placed onto the board—often with no external components. Such parts can be incorporated into designs without worrying about what’s happening inside the "black box. "But comprehending their underlying principles of operation and key performance parameters can help users to optimize converter performance.

Modular dc-dc converters generally employ switch-mode regulation rather than less-efficient linear regulation.Typically,switch-mode converters take a dc voltage, violently chop it at several hundred kilohertz, filter it, and then regulate it at a lower (or higher) output voltage. Aside from voltage conversion, these converters can also help to isolate different portions of the system, reducing crosstalk and ground-loop effects.

Chopping the input waveform is necessary because the power transistors are most efficient if they’re fully on or off. Even so, by just transitioning through the linear operating range, the transistors generate heat that must be dissipated. Losses also occur in the magnetics and other passives. Plus, switch-mode operation produces output spikes and noise.

The design goal for vendors of dc-dc converters is to reduce the impact of heat and noise while achieving low output impedance, excellent dynamic response, low cost, and minimal size. To satisfy these diverse design criteria requires innovations in circuit architecture, control ICs and power semiconductors, magnetics, capacitors, interconnects, and packaging.

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