What Is a Desktop Power Supply?

The computer power supply is a closed, independent component installed in the main box. Its role is to convert AC power to + 5V, -5V, + 12V, -12V, + 3.3V, -3.3V and other stable and reliable voltages. DC power is supplied to the system board, various adapters and expansion cards, hard disk drive, optical disk drive and other system components in the main box, as well as the keyboard and mouse.

The PC power supply is a four-way switching regulated power supply without a power frequency transformer. Its working principle is: after 220V mains input, it is first filtered by a low-pass filter and bridge rectifier to become a 300V DC peak high voltage. The high voltage is sent to a pulse width modulator, a conversion oscillator (power conversion circuit), and it becomes a rectangular wave or sine wave of 300V, and then it can output + 12V, + 5V DC stability through high-frequency transformation and rectification and filtering. Voltage for system use.

The power supply uses the feedback voltage regulation principle that adjusts the duty ratio of the 300V rectangular wave to adjust the DC output value. It also uses direct rectification, high-frequency conversion and pulse width modulation technology, so it eliminates bulky transformers, has a small size, light weight, Features of high efficiency and over-current and over-voltage protection. In addition, the power supply unit also generates a power signal-Power Good signal, which indicates that the power supply is normal, and provides it to the host to generate a hardware reset RESET signal, so that the system starts normally ^[1]

IPC power supply: The power supply of IPC requires anti-surge protection, over-voltage and over-current protection, and strong anti-interference ability. There are many types of power supply for industrial computer. In order to adapt to the characteristics of large voltage fluctuations on the industrial site, industrial computer power supplies have a relatively wide adjustment range, and the deviations of output voltage and current are relatively small. The MTBF is long, generally 60,000 to 100,000 hours. ^[2]

Mainframe Power: Mainframe computers are sensitive to power distortions or interference called "noise." The noise is mainly caused by disconnecting the inductive circuit. This inductive circuit causes instantaneous peaks, or is caused by the contact between the brush mechanism of the motor and the commutator. These distortions in the power supply can cause computer accidents or computer errors. To avoid this, mainframe networks require a "high quality" power source. Power can be provided to the computer through a ring or radial circuit, and the power source should be placed as close as possible to the power inlet of the building. Reliable grounding can also be obtained from this location. It is usually a core in the cable, not the shield layer of the SWA cable, and is distributed around the terminal wiring circuit ^[3]

(1) Multi-national certification mark

Quality power supply with

From the comprehensive analysis of the status and role of the power supply, it can be considered that the performance of the host is superior or not, and it has a great relationship with the quality of the power supply. A good quality power supply should have the following characteristics:

(1) Protective: With good self-protection function, when the DC current is too large, the voltage is too large, no load or the load is short-circuited, it can automatically cut off the power to maintain the current cut-off state. After the fault disappears, it can automatically resume normal power supply .

(2) Stability: The output DC power is required to be stable and there is basically no fluctuation, that is, + 12V, -12V, + 5V, -5V four sets of power voltage and current are normal, otherwise it will affect the work of the host.

(3) Heat dissipation: The built-in fan of the power supply has a large air volume, which can fully diffuse the large amount of heat released during the power supply's operation, and prolong the service life of the power supply.

(4) Anti-interference: Power of good quality is not affected by the switching on and off of other electrical equipment. When the power supply with low anti-interference ability is turned on, the microcomputer may generate abnormalities such as self-starting when other electrical appliances are turned on.

(5) Low noise: The components are solid, the power supply fan runs stably, and no noise is produced during work. High-noise power sources are mostly caused by component vibration, unbalanced fan blades, eccentric shafts, or poor lubrication. The high-noise power sources are also prone to failure during use.

(6) Compatibility: It should have standard power supply specifications, and must meet various functional parameters of standard switching power supplies (the shell size and the location of the fixing screws are consistent, suitable for various standard chassis), and provide standard stable voltage and current ^{[1 ]}

The computer's power supply has two structural forms, AT and ATX.

(1) AT power supply

From the appearance, the AT power supply is just an iron box with many leads. The two sockets at the rear of the power supply are used to connect external power and provide sockets for the display. Generally, male sockets are power sockets. Some power supplies have a voltage setting switch between the two sockets for switching between 110V and 220V voltage systems. The 220V voltage system is commonly used in China. If it is set incorrectly on the 110V block, it will cause damage to the power supply.

The AT power supply has a total of four outputs (± 5V, ± 12V) and provides a PG signal to the motherboard. The power is generally 150W ~ 220W. The motherboard power cable provided by AT Power is a 12-pin separate plug. Each 6-pin is a plug. There are two, and two black wires must be plugged together, otherwise the motherboard will be burned. The AT power supply is shut down by cutting off the AC grid.

Prior to the emergence of ATX power, computers from 286 to 586 used AT power.

(2) ATX power supply

From the appearance, the ATX power supply is also an iron box with many leads. It removes the monitor socket and installs a power switch in this position, which is a true physical power cut-off switch, which is essentially different from the POWER key on the front of the ATX case.

In addition to making some improvements to the ATX power supply on the line, the most important thing is to add a power management function called Stand-By. It allows the operating system to directly manage power. Through this function, users can directly implement network power management through Windows 95/98. For example, when the computer is off, it can send a signal to the computer's Modem through the network, and then the monitoring circuit will issue a + 5VSB unique to ATX power The activation voltage is used to turn on the power to start the computer, thereby enabling remote power on.

ATX power supplies provide multiple sets of plugs, which are mainly 20-pin motherboard plugs, 4-pin driver plugs, and 4-pin small drive special plugs. The 20-pin motherboard plug is directional, which can effectively prevent mis-insertion. The plug is also equipped with a fixing device that can hook the socket on the motherboard, so that the connector is not loose and the motherboard is suddenly powered off in the working state. The 4-pin drive power plug is most widely used, and it is used by all CD-ROM, DVD-DOM, CD-RW, hard disks and even some fans. The 4-pin plug provides two sets of voltages, + 12V and + 5V. Generally, yellow wires represent + 12V power, red wires represent + 5V power, and black wires represent 0V ground. This 4-pin plug power supply provides the largest number, if the user is not enough, you can use one to two adapter cable. The principle of the 4-pin small drive special plug is the same as the ordinary 4-pin plug, but the interface is different. It is designed for the traditional small drive power supply.

The types of ATX power supplies are ATX1.0, ATX1.1, ATX2.01, ATX2.02, etc. At present, ATX2.01 is the main type. For high-end chassis supporting or single-purchase high-end power supplies, there are ATX2.02 versions of products.

The quality of different types of products is not the same, the latter product is of higher quality. Each of these different types of ATX power supplies has its distinctive features.

· Different in appearance

The power supply fan of the ATX1.01 power supply is above the CPU. This is done to eliminate the CPU fan, but the effect is not good. The 2.01 version of the power supply fan is still in the same position as the original AT power supply.

Different activation current

ATX1.01 power supply activation current is only 100mA, ATX2.01 power supply activation current is 500mA ~ 720mA. Obviously, in some cases, version 1.01 is more allergic, and it is often affected by external influences to start the computer by itself ^[4]

1. Common failure phenomena of computer power supply Common failure phenomena of computer power supply are:

The computer cannot be turned on, and the ATX power supply has no voltage output;

The computer keeps restarting automatically:

The computer freezes when booting;

After the computer is started for 3 seconds, it will automatically shut down;

The output voltage of ATX power supply is low.

2. Reasons for computer power failure The main reasons for computer power failure are:

The output voltage of ATX power supply is low;

The output power of ATX power supply is insufficient;

ATX power supply is damaged;

ATX power fuse is blown;

The switch tube is damaged;