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iPhone display circuit repairing
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This video mainly explains the working principle of the display power supply
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iPhone 6 to iPhone 8P, iPhone XR and iPhone 11
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The display power supply models of them are the same
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the working principle is the same, and can be replaced
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The working principle is explained below
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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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The main power supply will provide the working voltage for the display power supply,
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and will also be connected to the boost inductor to provide power for the display power boost
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step 2
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After starting up, the main power supply will generate a reset signal after outputting the power supply,
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and then it will provide a reset signal for the display power supply
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Step 3, after the CPU working condition is normal,
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it will detect the display power supply through the I2C bus
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Step 4
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After the display power supply has power supply, reset signal, and the I2C bus is detected,
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a 6V boost power supply will be generated to provide working voltage for the screen in the future
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Step 5
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After the 6V boost power supply works normally,
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the CP and CN pins inside the chip will be connected to the coupling capacitor
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to convert the positive and negative 5.7V power supply
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CP refers to positive 5.7V,
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CN refers to negative 5.7V
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In the actual measurement, we can only measure 5.7V on the CP,
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and the negative voltage cannot be measured
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Step 6
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When the display circuit is started,
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the display sends a PWR_EN power-on signal to the display power supply
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If you do not buckle the screen, the display will not have the turn on signal
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step 7
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when the display power supply receives the enable signal,
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it will output positive and negative 5.7V power supply
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At this time, the display will have positive and negative 5.7V power supply
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ADCMUX is the signal for the main power supply monitoring the display power supply
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When the display power supply is working normally,
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it will send the ADCMUX signal to the main power supply
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If there is a problem with this signal, it will also cause no display
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The PWR_EN signal for the display is actually the last working condition of the display power supply
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If there is no abnormality on the display connector,
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and the positive and negative 5.7V power supply is still not detected,
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it means that the previous working conditions of the display power supply are abnormal
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During the maintenance,
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it is necessary to measure other working conditions of the display power supply
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Ok, that's all for this video
