Characteristics of Original IBM PC UPS Units
A power supply is a device that provides electrical power to an appliance or electronic application. The primary function of such a power supply is simply to convert electrical current from an external source into the appropriate voltage, frequency, and current to power the appliance. The output of the power supply will then be routed to the appropriate destination, such as to an outlet or to the wall outlet in your home. At the same time, the power supply must ensure the safety of all persons in the vicinity of the power supply. For this reason, it must be designed and installed carefully with specific considerations for all types of power and voltage.
AC power supplies come in a variety of configurations. As an example, there are those that work well with low voltage systems and can be used on desktop computers. On the other hand, there are also those that operate better with higher voltage loads. Nevertheless, all portable power supplies must have one common factor: they must be able to deliver the appropriate voltage to any and all of the appliances that they are going to power at any given time.
The form factor is the physical size, layout, and physical design of the power supply unit. For example, most desktop personal computer power supplies are supplied in a 12V form factor. However, the voltage needed may vary depending on the application. Therefore, the form factor is important to consider.
The power supply may also be classified according to how it operates. The first classification is linear. It operates in one complete cycle. Commonly, the ac-dc conversion happens in linear mode with an AC/ DC power supply having two primary wires and a corresponding inverter. The power supply then changes its state from linear to linear via the bridge in the inverter.
Most computer power supplies in the market today come in three different states: standby, bridged, and transient. Standby supply functions just like an uninterruptible power supply. A bridged supply bridges a short circuit either across it or between the bridged wire and the source or sink of power, such as a DVD player or printer. A transient supply behaves similarly to a fuse; however, it does not come into play when an uninterruptible power supply comes into contact with it.
In order for your computer power supplies to give you the best performance, the operating requirements for each are very critical. If the supply needs to run continuously, then it is always better to buy a supply that is capable of running continuously. In cases where the supply has to switch over to standby, the supply’s capability will determine the amount of heat generated during the switchover. It is therefore advisable to purchase a supply that has higher temperatures for standby situations.
The final characteristic to look out for in a laptop UPS unit is its switched-mode power supply. A switched-mode power supply operates in a completely different manner compared to an ordinary battery-powered supply. When the source is turned on, the switching transistors in the power supply fire the battery. However, when the source is turned off, the transistor switch shuts down, thus turning off the battery and turning off the power supply.
There are four common switching frequencies for laptop UPS; the desired frequency depends on the equipment being used. The switching frequency for a battery-powered device will be slightly lower than the desired frequency for a switching power supply, for example, a DC output of 9V will be substituted with a smaller, zero-powered input, such as a 3.5V step down transformer. A high output DC input, however, may lead to overloaded AC power when the AC power input drops below the set limit. For this reason, always choose the switched-mode AC output, over the common non-switched-mode DC input.
