Power Supply Theory - Agilent Technologies 8753ES Option 011 Service Manual

Theory of Operation

Power Supply Theory

Power Supply Theory
The power supply functional group consists of the A15 preregulator and the A8 post
regulator. These two assemblies comprise a switching power supply that provides
regulated DC voltages to power all assemblies in the analyzer. The A15 preregulator is
enclosed in a casting at the rear of the instrument behind the display. It is connected to the
A8 post regulator by a wire bus A15W1. Figure 12-2 is a simplified block diagram of the
power supply group.
Figure 12-2 Power Supply Functional Group, Simplified Block Diagram
A15 Preregulator
The A15 preregulator steps down and rectifies the line voltage. It provides a fully
regulated +5 V digital supply, and several preregulated voltages that go to the A8 post
regulator assembly for additional regulation.
The A15 preregulator assembly includes the line power module, a 60 kHz switching
preregulator, and overvoltage protection for the +5 V digital supply. It provides LEDs,
visible from the rear of the instrument, to indicate either normal or shutdown status.
Line Power Module
The line power module includes the line power switch, voltage selector switch, and main
fuse. The line power switch is activated from the front panel. The voltage selector switch,
accessible at the rear panel, adapts the analyzer to local line voltages of approximately
115 V or 230 V (with 350 VA maximum). The main fuse, which protects the input side of
the preregulator against drawing too much line current, is also accessible at the rear
panel. Refer to your analyzer's Installation and Quick Start Guide for line voltage
tolerances and other power considerations.
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