Low Power, High Efficiency Can Degrade Performance Significantly

Focus:

Improving power supply efficiency and lowering standby power, the current trends in power supply development, may come at the cost of degraded noise performance, stability, and suspectibility to EMI. This articles explains why designers need to understand these tradeoffs when selecting voltage regulators. The article discusses semiconductor device physics and the relationships between impedance, bias currents, and noise, explaining how striving for higher efficiency leads to greater noise at the transistor and circuit level. It explains how lowering the output current of a linear regulator reduces its stability and degrades closed-loop characteristics. Voltage regulators are ranked according to their relative noisiness: voltage references (quietest), linear regulators, LDOs, and switching regulators (noisiest). The author gives some general advice on selection of voltage regulators based on application sensitivity to noise.

What you’ll learn:

• How to understand the tradeoffs in power consumption, efficiency, noise, and other characteristics when selecting voltage regulators
• How to understand why the most efficient voltage regulator is not necessarily the best voltage regulator for a given application

Notes:

The author summarizes his message as follows, “While RF engineers use many classes of amplifiers, it is advisable for power engineers to also learn to use many classes of voltage regulators. Each type of regulator has its place, and when evaluated properly, a balance between performance and power consumption can be achieved.”

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Author & Publication:

Steven Sandler, Picotest, Power Electronics Technology, Aug 01 2012

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