User`s guide

6 Tutorial
Overview of the Power Supply Operation
150 E3632A User’s Guide
Overview of the Power Supply 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 6- 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 6- 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 6-1 Diagram of a 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 6- 1 shows a controlled transformer tap as used in
the Agilent E3632A. This is one of several techniques using
semiconductors for preregulation to reduce the power
dissipated across the series element.