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Hello everyone, today we will learn about ATX power supplies in domestic computers

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In this lesson, we mainly introduce the types of desktop power supplies,

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the definition of power interfaces and the startup process

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There are three main types of desktop power supplies, one is ATX power supply,

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the other is BTX power supply, and the other is 12VO power supply.

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The appearance of the two power supplies, ATX and BTX, is basically the same,

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and its internal structure and working principle are also basically the same.

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Therefore, we will no longer distinguish and introduce it here.

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12VO is the kind of power supply that only outputs 12 volts

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This power supply has two sets of plugs that supply power to the motherboard,

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one set is 4pin or 8pin, and the 12V that supplies power to the CPU

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There is also a group of 20pin or 24pin, which supplies power to the position of the motherboard.

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We can distinguish its output voltage by color

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Black is the ground wire (GND)

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The green one is PS_ON# (power on signal)

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Purple is the 5V standby voltage (5VSB)

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The orange one is 3.3V

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The red one is 5V

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The yellow one is 12V

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The blue one is -12V

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The gray one is PG signal

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It has these voltages in total

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For example, the 4pin interface that supplies power to the CPU,

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the color of this line is yellow, which is the 12V power supply,

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which is specially used to provide power to the upper tube D level of the CPU power supply circuit.

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These supplies are divided into standby voltage and voltage after start-up

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In standby mode only 5VSB is 5V standby voltage

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It mainly provides standby power for the motherboard

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The 5V standby power supply is stepped down by the voltage regulator on the motherboard

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to generate a 3.3V standby voltage

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3.3V standby can be measured at the B10 pin of the PCIE slot

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The green line (PS_ON#) is the switch signal

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In the standby state, this PS_ON# is high level

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When we press the switch, PS_ON# will be pulled down by the IO on the motherboard

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When the mainboard pulls the green line low,

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the ATX power supply will output orange 3.3V, red 5V, yellow 12V, and blue -12V, etc.

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When these power supplies are normal, a gray PG signal will be output at last,

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indicating that the power supply is normal

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There is a startup process here

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When we connect this ATX power supply to the motherboard,

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plug this ATX power supply into 220V AC

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Then the ATX power supply will first output the 5V standby voltage and the high level PS_ON# signal

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When we press the switch, the motherboard will pull down the PS_ON# signal,

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and the power supply will output power from various channels

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This is its interface definition and startup process