3. Theory of Operation
Functional Block Descriptions
158
A12 Dc-Dc Power Converter Module
The primary components on A12 module are three resonant zero-current
switching Dc-Dc converter modules (A12U1-U3). There is a converter module
for each power supply voltage (+5V, +12V, and -12V). Both the input and
output ports of each module are heavily filtered. Additional circuitry consists
of overvoltage protection on each output port (any one voltage going too high
shuts down the entire supply) and additional filtering common to all inputs.
LF1 AC-Line Filter/Cable Assembly
The LF1 Assembly provides ac-line noise and spike protection, fuse
protection, and line voltage selection. The assembly mounts to the rear
bulkhead of the instrument chassis and connects directly to the toroidal
power transformer T1.
T1 Toroidal Power Transformer
The toroidal power transformer provides the required ac step-down capability
to supply the A12 module with its specified input voltage (after appropriate
rectification and filtering). The toroidal design reduces radiated magnetic
fields and eddy-current-induced heat and also provides a more compact
transformer component.
B1 Internal-Standby Battery
(Does not apply for Opt. 048). The B1 24-volt Battery consists of two
identical sealed rechargeable 12-volt lead-acid battery packs located in the
rear of the instrument underneath the A11 assembly.
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