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This lesson is about the related circuit of the receiver

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First look at an early low-end model, take Changxiang 9 as an example

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It uses a Qualcomm chip

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Let's see what components are in this circuit

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Look at the right first, ANT 1701 and 1702 written here on the right, they are the two shrapnel of the earpiece

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The circuit diagram generally does not draw the circuit diagram of the earpiece,

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at most it is the position of the shrapnel of the earpiece, or the position of the connecting seat of the earpiece

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Here is the contact position of the earpiece

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The earpiece shrapnel touches this contact to transmit the sound signal

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This power IC is actually a large audio

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The monaural sound written here refers to the traditional early earpiece

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The early earpiece was driven by a large audio frequency to make sound,

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it did not support playing music, so we call it monaural

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The one on the left is the CPU

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The CPU plays a vital role in the earpiece circuit

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The CPU usually transmits the sound signal to the big audio through the bus

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The big audio converts the sound signal to digital and analog, and amplifies it internally

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After the amplification, the sound signal is output and the earpiece is pushed.

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When making a call, the handset will make a sound when the handsfree is not turned on

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This is an early Qualcomm

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Let's take a look at the stereo earpiece of Huawei P40

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What is stereo, that is, the earpiece can act as a speaker for playing music

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The power of the handset is adjusted by the circuit,

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and it is controlled by the small audio to make it sound

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Then when the sound is loud, it plays music,

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and when the sound is low, it is equivalent to an earpiece

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It controls the size of the output power of the power amplifier to control the size of the sound

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There are handset, small audio, main audio and CPU in this circuit

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We see that the stereo earpiece circuit is exactly the same as the speaker circuit we mentioned earlier

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Let me tell you roughly here

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The sound signal of the earpiece comes from the large audio,

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and the sound is transmitted to the small audio through the I2S bus

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The small audio is converted from digital to analog, and then the power is amplified,

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and finally the signal of the earpiece is output to the earpiece

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It is such a working process

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The sound signal is transmitted between the big audio and the main CPU through the Slim bus

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Stereo earpiece and speaker circuits are exactly the same, so we won't say more here

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We can see that the code name of the handset here is RCV

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Another code name for the handset is EAR

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Let's take a look at the Xiaomi 10 Pro model

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Here is the earpiece contact point

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The earpiece and the mainboard are separate

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This is the main audio

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This earpiece does not have stereo, it is only responsible for the earpiece

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This machine is very interesting

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It has a speaker on the top, and the other speaker is driven by a small audio amplifier

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The earpiece is the earpiece, the top speaker is the top speaker, they are separate,

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not the same as Huawei P40

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The earpiece at the top of the Huawei P40 acts as a speaker and also as an earpiece

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This is the main audio, it is only responsible for the fact that

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we can hear the other party's voice when the hands-free is not turned on

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The audio signal is transmitted between the main audio and the CPU through the SWR_TX or SWR_RX bus

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Xiaomi 10 Pro uses Qualcomm's CPU

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The audio that begins with WCD is Qualcomm's solution

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Its working process is that the CPU sends a sound signal to the main audio through the SWR bus

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After the main audio processes it, it outputs a sound signal and sends it to the earpiece contact

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This sound signal makes the earpiece emit sound.

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These are the circuits of the earpieces of these models

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That's all for this lesson