power to the CPU, IOA, IOC, and memory
modules
Secondary power converters —Secondary power
converters provide the required dc power to the
CPU, IOA, IOC, memories, remote operator
unit, and display operator unit
OUTPUT
As stated, the rectifier (in some cases) and the
regulators distribute the required power throughout the
computer. The outputs are used for the following:
Logic circuits (includes computer’s master
clock)
System buses
Indicators and switches
Fans (micros)
Peripherals (micros)
The logic convention and voltage levels vary for
each computer type.
Consult your owner/technical
manual; this is very important when performing
maintenance.
COMPUTER POWER SUPPLY
PROTECTION
The computer’s power supply must protect the
computer from the incoming power, the distributed
power, and/or the temperature inside the computer’s
cabinet and/or module(s). Computer protection is the
one area where there is a distinct difference between
mainframe/minicomputers and microcomputers. We
provide general block diagrams to illustrate our point.
Mainframe/Minicomputers
Mainframe and minicomputers are generally
equipped with circuitry that will sense the incoming
power and monitor power while the computer is up and
operating. The incoming power must reach a certain
level before the power controlling device will allow you
to apply power to the computer and light the appropriate
indicators on the power controlling device. The
minimum voltage level will vary; consult your
computer’s technical manual. The regulators of a
power supply will generally shut off the computer in the
event of uncorrectable power variations.
Figure 4-44 is a basic block diagram that illustrates
a power supply for mainframes and minicomputers.
Figure 4-44.—Basic block diagram to illustrate a power supply for mainframes/minicomputers.
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