There are some features of the computer power supply which should be consider when buying or replacing your old power supply. Here is a power supply features to be considered:
- The mean time between failure (MTBF) or mean time to first failure (parameter MTBF (Mean Time Between Failures) or MTTF (Mean Time To Failure)). It’s estimated the average time interval in hours, during which the expected that the power supply will operate correctly. MTBF power supplies (such as 100 thousand hours or more) usually is not determined by empirical tests, and otherwise. In fact, manufacturers have used the previously developed standards to calculate the probability of failure of individual components of the power supply. In calculating the MTBF for the power supplies are often used data on the load power supply and ambient temperature, which carried out the tests.
- The range of input voltage (or the operating range) , which can operate the power supply. For the voltage range 110 V input voltage values are typically between 90 and 135, for input voltage of 220 V – 180 to 270 V.
- Peak inrush current . This is the highest value of current provided by power supply at the time of its incorporation, expressed in amperes (A). The smaller the current, the less thermal shock tests the system.
- Time (in milliseconds) to keep the output voltage within a precisely defined voltage ranges after disconnecting the input voltage . Typically, 15-25 ms for the modern power supplies.
- Transient response . The amount of time (in microseconds), which requires a power supply to set output voltage in the well-defined range after a sharp change in current output. In other words, the amount of time required to stabilize the output voltage after switching on or off the system. Power supplies are designed for uniform (to a certain extent) the current consumption of the devices on your computer. When the device does not power consumption (for example, the drive stops the rotation of the disk), power supply may apply too high output voltage for a short time. This is called the ejection, the transient response – this time, which expends power supply to ensure that the voltage had returned to accurately set the level. In recent years, achieved considerable success in solving problems associated with the phenomena of emission sources of supply.
- Surge protection. This value (for each pin) at which the trigger circuit protection and power supply cuts off the voltage to a particular conclusion. Values can be expressed as a percentage (eg 120% to +3.3 and +5 V) or the same as the voltage (eg 4.6 V for +3.3 V output, 7.0 V for withdrawal 5 B).
- The maximum load current. This is the highest value of current (amps), which can be served to a particular conclusion (without prejudice to the system). This parameter indicates the specific value of current for each output voltage. From these data we calculated not only the total power that can give power supply, but the number of devices that can connect to it.
- Minimum load current. The least value of current (amps), which can be served to a particular conclusion (without prejudice to the system). If the current consumption of devices in a specific output, less than the specified value, the power supply may be damaged or can automatically shut down.
- Stabilization of the load (or voltage regulation on load). When the current in a specific output increases or decreases, changes slightly and strain. Stabilization of the load – the change in voltage for a given output at differences from minimum to maximum load current (and vice versa). Values are expressed as a percentage, usually they are within ± 1 to ± 5% for the conclusions of +3.3, +5 and +12 V.
- Stabilization of the line voltage. This is a characteristic that describes the change in output voltage as a function of input voltage (from lowest to highest value). The power supply must operate correctly with any AC voltage in the range of input voltage, and output it can be varied by 1% or less.
- Efficiency (efficiency). The ratio of the power supplied to the power supply to power output, expressed as a percentage. For modern power supply efficiency value is usually equal to 65-85%. The remaining 15-35% of the input power is converted to heat in the conversion from AC to DC. Although the increase in efficiency (efficiency) means a decrease in the amount of heat inside the computer (it is always good), and lower electricity bills, it should not be achieved through stabilization accuracy regardless of load on the power supply and other parameters.
- Ripple (Ripple) (or ripple and noise (Noise and Ripple) , or ripple voltage (AC Ripple) , or PARD (Periodic and Random Deviation – periodic and random deviation) , or noise, the noise level) . The average value of peak (maximum) voltage deviations on the findings of the power supply, measured in millivolts (rms). These power fluctuations can be caused by transients in the power supply frequency vibrations supply voltages, and other random noise.
