Page 185 - Anatomy of a Robot

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170 CHAPTER SEVEN
The following PDF files contain basic information about both linear and switch-
ing power supplies:
www.web-ee.com/primers/files/f4.pdf
www.web-ee.com/primers/files/AN-556.pdf
An offshoot of linear regulators is the Low Drop Out (LDO) regulator. LDOs are
linear regulators that expect a very low difference between Vin and Vout. They are
used primarily for the local regulation of voltage or in situations where Vin is very
low and Vout must be as high as possible. Since the efficiency is high (Vout/Vin),
LDOs generally do not need large heatsinks.
LDOs can be used for distributed regulation. Instead of having a single power sup-
ply in the robot, Vin is distributed throughout the robot and sent to several LDOs,
which provide regulated Vout power to different parts of the robot.
Switching regulators Switching regulators are generally more efficient than
linear regulators. In addition, they can perform feats like making Vout higher than
Vin, but this does not mean the efficiency is higher than 100 percent. Because cur-
rent does not flow linearly through a switcher, the efficiency cannot be easily
computed.
Switchers basically take Vin and convert it to a high-frequency AC voltage wave-
form. This high-frequency current is transformed in various ways to a raw DC
voltage that can be higher or lower than Vin. Then the AC components are re-
moved to form Vout, an action made easier because these AC components are high
frequency and are easily filtered out. The following PDF files have further expla-
nations of this process:
www.web-ee.com/primers/files/webex9.pdf
www.web-ee.com/primers/files/f5.pdf

Switchers can run at a very high efficiency (above 90 percent) when used care-
fully. In practice, don’t count on achieving the claims made by the manufacturer.
Count on 75 percent and be surprised if the real number comes out higher. But in
a robot, this type of power supply can conserve energy. The downside is that
switchers will generate significant amounts of electrical interference of all types.

PROCESSOR

All further considerations of hardware energy savings must start with the processor. The
processor has several energy-saving features, which we have discussed before, and they
are outlined in the following sections.