Agilent Technologies E3631-90002, User Manual, Page: 140 / 166

Chapter 7 Tutorial
Overview of Agilent E3631A Operation
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7
Overview of Agilent E3631A Operation
Series regulated power supplies were introduced many years ago and are
still used extensively today. The basic design technique, which has not
changed over the years, consists of placing a control element in series with
the rectifier and load device. Figure 7-1 shows a simplified schematic of a
series regulated supply with the series element depicted as a variable
resistor. Feedback control circuits continuously monitor the output and
adjust the series resistance to maintain a constant output voltage. Because
the variable resistance of Figure 7-1 is actually one or more power transistor
operating in the linear (class A) mode, supplies with this type of regulator
are often called
linear
power supplies. Linear power supplies have many
advantages and usually provide the simplest most effective means of
satisfying high performance and low power requirements.
Figure 7-1. Diagram of Simple Series Power Supply with Tap Selection
To keep the voltage across the series resistance low, some supplies use
preregulation before the rectifier bridge. Figure 7-1 shows a controlled
transformer tap as used in the Agilent E3631A. This is one of several
techniques using semiconductors for preregulation to reduce the power
dissipated across the series element.