Circumventing Loss In An RC Circuit Leads To More Efficient Power Converters
by by Nihal Kularatna, University of Waikato, Hamilton, New Zealand; Kosala Gunawardane, Auckland University of Technology, Auckland, New Zealand; and Thilanga Ariyarathna, University of Waikato, Hamilton, New Zealand , How2Power Today, Aug 15 2017
Focus:
The efficiency of a simple RC charging circuit varies with the initial voltage on the
capacitor. If the capacitor is a supercapacitor, which results in long time constants,
we can take advantage of this relationship between circuit efficiency and capacitor
voltage to create novel ac-dc converters with improved efficiency. This article
describes two novel ways in which the RC circuit can be combined with power converters
to negate the resistive loss of the RC circuit. One approach replaces the resistive
part of the circuit with a useful resistance such as a loaded dc-dc converter or
voltage regulator. The other places a supercapacitor ahead of a linear regulator as a
lossless voltage dropper. This technique has been dubbed the supercapacitor-assisted
low dropout regulator (SCALDO). After explaining the key principles of SCALDO
operation, the article presents a discrete implementation to demonstrate its
performance and discusses the benefits of implementing the SCALDO in silicon.
What you’ll learn:
- How to build a LDO-based regulator circuit with high efficiency
- How to improve LDO efficiency using a supercapacitor as a voltage dropper
- How to reduce overall losses in a simple RC charging circuit
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