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iPhone display circuit repairing

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This video mainly explains the working principle of the iPhone 12 series display power supply

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Step 1, when the battery is buckled or the adjustable power supply is connected,

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the main power supply will be generated

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One way of the main power supply will provide the working voltage for the display power supply,

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and the other way will reach the display power supply through two boost inductor for future work

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Step 2, when the CPU working condition is normal after the trigger is turned on,

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it will detect the display power supply through the I2C bus

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Step 3, when the display circuit is started,

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the main power supply sends a reset signal to the display power supply

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Step 4, after the working condition of the display screen is normal,

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it will send VOUT1 2_EN and VOUT3_EN to the display power supply,

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so that the display power supply can output the positive and negative power supply of the display screen

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Step 5, after the display power supply has a turn-on signal,

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the inside of the chip will convert the positive and negative power supply of the display through the inductor

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Step 6, after the display power supply is converted,

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it will output 4.6V, 7.3V and -7V power supply to the display screen

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Other detection signals of the display power supply

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AMUX is the monitoring signal sent by the display power supply to the main power supply

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When the display power supply is working normally,

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it will send this signal to the main power supply

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If the signal is abnormal, it will result in failure to output the power supply of the display screen

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PANICB is the signal for the main power supply to identify the screen

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In the 12 series, it is sent from the main power supply to the display power supply first,

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and then it is sent to the display screen

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When checking and repairing the display circuit,

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if the power supply of 4.6V, 7.3V, and -7V cannot be detected,

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it means that the working condition of the display power supply is abnormal,

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or there is a problem with the display power supply itself

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We need to measure all the working conditions of the display power supply

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If the working conditions are normal, we need to replace the display power supply

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Ok, that's it for this lesson