Tuesday, April 9, 2013

Power units

   The power unit is one of the most unreliable devices of computer system It is the vital component of the personal computer as without power supply any computer system won't be able to work Therefore for the organization of accurate and stable work of system it is necessary to understand well its functions, to have idea of restrictions of its opportunities and their reasons, and also of potential problems which can arise during operation, and ways of their permission.

Appointment and principles of operation of power units
   The main purpose of power units — transformation of the electric energy arriving from the alternating current main, to the energy suitable for a food of knots of the computer the Power unit will transform a mains alternating voltage of 220 V, 50 Hz (120 V, 60 Hz) to the constant tension of +5 and +12 V, and in some systems and to 3,3 V.Kak pravilo, for a food of digital schemes (a system payment, payments of adapters and disk stores) tension of 3,3 or +5 V is used, and for engines (disk drives and various fans) — +12 V.Kompyyuter works reliably only if values of tension in these chains don't leave out of the set limits.
If you glance in the passport of the typical power unit, you will see, what the block develops not only the positive tension of +5 and +12 V, but also negative------5 and-12 V.Poskolku in practice becomes clear, what for a food of all components of system (electronic schemes and engines) there are enough +5 and +12 V, there is a question for what negative supply voltages are used? The answer is simple: in the majority of modern computers they aren't used.
    When the Intel firm started releasing processors for which tension +3,3 B was required, power supplies with such output tension yet weren't. Therefore manufacturers of system payments started building in the converters of tension transforming tension + of 5 V to +3,3 V.Preobrazovateli of tension also generate a lot of warmth which is always undesirable to the personal computer. Now there are power supplies and the system payments calculated on +3,3 B, on such payments the converter which transforms tension + 5 V in + 3,3 B isn't necessary.
    Though tension of-5 and-12 V moves on a system payment via food sockets, for its work only the 5-volt power supply is necessary. A food of-5 V arrives on contact of B5 of the tire ISA, and on the most system payment it isn't used. This tension intended for a food of analog schemes in old controlers of stores on flexible disks therefore it and is brought to the tire. In modern controlers voltage of-5 V isn't used; it remains only as part of the standard of the tire ISA.

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