(Author: China Computer Newspaper, 2000 at 16:27 on November 17) for the role of the computer power supply, like the heart to the body, and its importance can not be overlooked. The quality of the power supply directly affects the service life of the computer. It has been unable to start the system unstable due to the problem of power quality. So, how do you think of a quality power supply? ■ The power supply classification AT power supply is generally 150W to 220W, a total of four outputs (soil 5V, soil 12V), providing a P.G. signal to the motherboard. The output line is two six-pin socket and several four-core plugs, and the two six-core sockets are powered on the motherboard. The AT power is turned off in a way that cut off the AC grid. Before the ATX power supply has not appeared, from 286 to 586 computers by the AT power supply in the rivers and lakes. With the popularity of ATX power, the AT power is now gradually faded out of the market. ATX Power INTEL L. In February in February, the ATX 2.01 standard. Compared to the AT power supply, its shape is not changed, mainly increasing the 3.3V and 5V Standby two outputs and a PS - ON signal, and the output line is powered on the motherboard. As the CPU operating frequency is increasing, in order to reduce the power consumption of the CPU, it is necessary to reduce the working voltage of the chip, so it is necessary to provide 3.3V output voltage by the power source. 5V Standby is also called auxiliary 5V, as long as it is plugged in 220V AC electricity, there is a voltage output. The PS --ON signal is the level signal provided by the motherboard to the power supply, and the power supply is started at a low level, and the power is turned off. With 5V SB and PS - ON signals, you can implement software switching machines, keyboard boots, network wakeups. The auxiliary 5V is always working, some ATX power supplies add a switch in the output outlet, cut off the AC input, completely shut down. Micro ATX Power Micro ATX is the standard that Intel has been launched after the ATX power supply. The main purpose is to reduce costs. Its significant change with ATX is that volume and power are reduced. The volume of ATX is 150mm × 140mm × 86mm. The volume of Micro ATX is 125mm × 100 mm × 63.51mm; the power of ATX is about 220W, and the power of Micro ATX is 90W to 145W. ■ The basic principle switching power supply of the switching power supply mainly includes input grid filters, input rectifier filters, converters, output rectifier filters, control circuitry, and protection circuits. Their functions are: 1. Enter grid filters: eliminate interference from grid, such as motor, switch, lightning strike, etc., and also prevent high frequency noise generated by the switching power supply to diffuse. 2. Enter the rectifier filter: Replace the grid input voltage to provide a DC voltage for the converter. 3. Converter: It is a key portion of the switching power supply. It transforms the DC voltage to a high frequency AC voltage, and it functions to isolate the output portion from the input grid. 4. Output Removed Filter: The high-frequency AC voltage of the converter is output to the desired DC voltage, and also prevents the interference of high frequency noise to the load. 5. Control circuit: Detect the output DC voltage and compare it to the reference voltage to enlarge. Modulate the pulse width of the oscillator to control the converter to maintain the stability of the output voltage. 6. Protection circuit: When the switching power supply occurs over voltage, the protection circuit causes the switching power supply to protect the load and the power supply itself.
Some readers will generate such questions, first turn the exchange of 220V into DC, then turn the direct flow through the converter to communicate, and finally turn the communication into DC output, and drive such a large circle, do not put 220V The alternating current is directly turned to the DC it needs? In fact, the exchange of electric shifters are transformed by power transformers. After rectifying filters, the unstable DC voltage is obtained. After adjustment, it is adjusted to obtain the desired DC voltage, which is mature, which can achieve high stability, corrugation Small, and no switching power supply has interference and noise. However, its disadvantage is that the volume and weight of the filter capacitance needed is also quite large, and the adjustment tube is working in linear state, and there is a certain voltage drop in the adjustment tube. When operating current, the power consumption of the adjustment tube is too large, the conversion efficiency is low, and a large heat sink is also installed. In short, this power source is not suitable for computer. The switching power supply mainly has the following characteristics: 1. Small size, light weight because there is no power frequency transformer, the volume and weight of only 20 to 30% of the linear power supply. 2. Small power consumption, efficiency high power transistor working in the switch state, so the power consumption on the transistor is small, the conversion efficiency is high, and only 30 to 70% of the linear power supply is only 30 ~ 40%. ■ The technical indicator output voltage of the power supply is too low that the computer cannot work, and the voltage is too high will burn the bad machine. The ripple of output voltage We want clean DC electricity, the smaller the AC ingredient, and the ripple conference has adversely affects the chip. Power Good Signal Power GOOD signal is referred to as P.g. or P.ok signal. This signal is logic of DC output voltage detection signal and AC input voltage detection signal, compatible with TTL signals. When the power is turned on, if the AC input voltage is within the rated operating range, and the DC output voltage has reached their minimum detection level ( 5V output is 4.75V), then the delay of 100 ms ~ 500ms The PG circuit issues a signal (P.ok is high). The power supply is sent out when the power AC input voltage falls below the safe operating range or the 5V voltage is below 4.75V. Power Fail should drop at least 1 ms to less than 0.3V before 5V, and the waveform of the falling edge should be steep, and there is no self-excited oscillation. P.g. Signal is very important, even if the DC output of the power supply is normal, if there is no P.G. signal, the motherboard is still not working. If P.G. The timing of the signal is not correct, it may cause a machine. The power of the power supply of the power supply is not bigger, the better. Tested, a PIM card, network card, sound card, optical drive, and hard disk PII multimedia host actual power is less than 100W, so it cannot blindly pursue high power, the key is the overall performance and quality of the power supply, more than enough for ordinary users, 200W. Entering technical indicators Input technical indicators include input power phase, rated input voltage, voltage variation range, frequency, input current, etc. The rated voltage of the input power is different from country or region, my country is 220V. The voltage range of the switching power supply is relatively wide, typically 180V to 260V. The AC input power is 50 Hz or 60 Hz, which is 47 Hz ~ 63Hz when the frequency change range affects the switching power supply. The maximum input current of the switching power supply means an input current to the lower limit value and the output voltage and the current to be the upper limit value. The rated input current refers to the input current when the input voltage, the output voltage, and the output current are rated. The impact current means that the input current flows through the maximum instantaneous current before the input voltage is turned off at a predetermined time interval.
