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We talk about how to repair the fault of no display in this lesson

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If there is no problem with the bus,

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the ground value of reset and detection,

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including the power supply of 1.8V and 3V,

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we need to detect the 3 power supplies that provide  the display,

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that is, the power supplies of the OLED screen,

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AVDD, ELVDD and ELVSS

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The characteristic of OLED screen power supply is that

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there are usually 3 inductors around the power supply chip

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Let's take a look at the overall structure of its circuit

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This chip is called the screen power supply chip

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It mainly boosts the main power supply and outputs a power supply of 7.6 volts

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Then this one is 4.6 volts,

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ELVSS is a negative voltage, negative 4 volts

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Why do we usually think of it as boost?

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We can see its output voltage,

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it outputs 3 way power supplies to the display

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The input is 4.3 volts, the output is 7.6 volts, 4.6 volts

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The output voltage is higher than the input voltage,

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this is a boost chip

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Well, this is a whole frame of it

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In fact, it still has some detailed circuits

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We can see from the drawing that it has 3 energy storage inductors

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This screen power supply chip is called U1701

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In this drawing, it is called the screen power supply chip,

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which is to supply power to the screen

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The VBAT_SYS on the left is the input power supply

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That is, it takes a power input to come in and outputs 7.6 volts, 4.6 volts and -4 volts

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After this chip adjusts the main power supply voltage,

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it outputs 3 channels of power supply

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Here we should pay attention to several key components,

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L1703, L1701, and this inductor

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Its inductance is actually the circuit of this negative 4 volts

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Then on the left side of this chip, AGND is also a ground wire

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AMOLED_AVDD_EN is an enable signal that turns on this 7.6 volts

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AMOLED is the trun on signal of ELVDD and ELVSS,

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that is, the turn on signal of 4.6 volts and -4 volts

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Okay, that's it for this lesson