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In this lesson, we talk about the maintenance of protection after triggered,

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which we usually call short-circuit after triggered

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We mainly focus on the following four aspects

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The first is the current phenomenon of the protection after triggered

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The second is the understanding of this phenomenon

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The third is what electrical circuits are related to this phenomenon

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Fourth, how do we repair the fault of protection after triggered

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Let's first look at the current phenomenon of protection after triggered

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We power this mainboard with 4.2 volts,

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after pressing the power button

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The current jumps from 0 to 3mA

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We release the power button, it stops immediately and goes back to 0

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Let's take a look again, 0-3 mA,

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in fact, it will return to 0 even if we don't release the power button

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This phenomenon is called protection after triggered

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To sum up,

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the protection after triggered phenomenon of Android phones

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is that when we press the power button,

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it has a current jump, and the jump is very fast

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The common ones are 0-3 mA, 0-9 mA or 0-10 mA

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After we release the power button,

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the current returns to 0,

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even if we keep pressing the power button, it will return to 0

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How do we understand this protection after triggered phenomenon?

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Let's sum it up in words

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We adjust the voltage of the DC power supply to 4.3V,

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use the power cord to supply power to the mainboard battery holder,

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press the power button,

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and there will be a small current jump in the current display position

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What are the characteristics of this current jump?

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It is 0-10 mA, which will return to 0 immediately,

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or 0 to dozen mA, which will return to 0 immediately

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If we don't press the power button,

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it will no longer jump

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This phenomenon is called protection after triggered

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Let's take a look at which circuits are associated with this phenomenon

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We have learned the entire boot process of the boot circuit before

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The battery supplies power to the mainboard,

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the mainboard supplies power to the charging chip,

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the charging chip converts the positive pole of the battery to the main power supply,

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and then provides power to the power chip

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After the power chip works, It will give a voltage to the power button signal

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When we press the power button,

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the power supply chip outputs VBUCK power supply to the CPU,

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temporary storage and hard disk

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In addition, it also outputs LDO type power supply,

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which is also called small current power supply

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It will output these two types of power supply to the CPU,

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temporary storage and hard disk

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And which circuits cause the phenomenon of protection after triggered?

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First of all, we must know that this machine can be triggered

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Since it can be triggered, it has nothing to do with the positive pole of the battery

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It can be triggered

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It proves that the positive line of the battery,

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the main power supply line and the power-on signal line

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from the power-on button to the power chip are all OK

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These two lines are no problem,

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we don't consider them

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So what do we mainly consider?

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It is the power supply circuit of the power output,

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that is, the power supply circuit that is output to the CPU,

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temporary storage, and hard disk after the power chip is triggered

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What does this power supply line contain?

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It is all the components that the power supply leads to,

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either the capacitor on the power supply line is short-circuited,

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or the chip on the power supply line is short-circuited

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Under normal circumstances,

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to repair the fault of protection after triggered,

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we mainly consider the power supply circuits of the CPU,

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temporary storage, and hard disk

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Ok, that's it for this lesson