Agilent Technologies E364XA Series, User Manual

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Chapter 7 Tutorial
Overview of this Power Supply Operation
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7
Overview of this Power Supply Operation
The basic design model for power supplies 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 phase-controlled
pre-regulator described as a power switch and the series element depicted as
a variable resistor. The phase-controlled pre-regulator minimizes the power
dissipated at the series element by maintaining the voltage drop across the
series element at a low and constant. 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
This power supply has two ranges, allowing more voltage at a lower current
or more current at a lower voltage. Single range supplies can only output
maximum power at full scale voltages and full scale current. This supply can
provide output power that is close to maximum at full scale for both ranges.
The pre-regulator in this power supply uses solid state transformer tap
switches on the secondary winding of the power transformer. This technique
is very effective in reducing the power dissipated in the series element.