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This lesson talks about the maintenance of low battery and failure to charge

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When charging, it will prompt that the battery is too low

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This means that the charging responds but cannot be charged, that is, there is no charging current

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Let's take a look at the fault phenomenon that indicates that the battery is too low

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After pressing the power button, plug in the charger, the phone prompts that the battery is too low

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This kind of failure is generally ruled out by replacing the battery first.

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If after replacing the battery, it still prompts that the battery is too low,

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it is necessary to repair the charging circuit.

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The failure of charging is that after plugging in the charging cable,

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there is a charging sign, but there is no charging current

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Where can the charging current be seen?

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There is a special USB current detector, or a charger with a charging current display

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Use these two devices to observe the charging of the mobile phone

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to see if there is a current of more than 1 amp

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Next, let's see which components are related to MTK's non-charging

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This is the MTK machine

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In this circuit, there are tail sockets inside the charging circuit, charging chip and battery interface

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The battery interface here is regarded as this battery

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This is the CPU

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After plugging in and charging, the CC pin detection data changes

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The charging voltage comes from the tail plug

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The CPU will control the charging chip,

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and adjust the charging inductance through the internal step-down circuit through the input 5V voltage

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Step down to a voltage and add it to the main power supply

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Then the main power supply is supplied to the MOS tube inside the charging chip

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After the MOS tube is turned on, it charges the positive pole of the battery

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This is its charging process

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It should be noted here that in maintenance,

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the faults of these signal lines are generally different,

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and the resulting fault phenomena are also different

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In maintenance, the general USB data communication is DP and DM

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If there is an open circuit, it will cause no response when plugging and charging

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Then CC1 and CC2 will cause plug-in charging without charging current but there is a response

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With charging icon, no charging current

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This is when the CC pin is not open, it will lead to this

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In the case of no open circuit, but the ground value is slightly abnormal,

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at this time it will result in a charging icon and no charging current

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If the CC pin measures infinity, it will cause another charging phenomenon:

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no response when plugging in and charging

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That's all for this lesson