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Hello everyone, today we are going to introduce PWM output voltage adjustment

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First, let's look at the FB pin of a PWM chip

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This pin is called the feedback regulating pin

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It is connected to the back end of the inductor by connecting the resistor and the series partial voltage,

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which is used to detect whether the output voltage of the inductor is normal

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The voltage at the back of the inductor, divided in series through a resistor,

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is sampled and compared to a reference voltage inside the chip

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The reference voltage inside the chip is defined by each chip manufacturer and varies from chip to chip

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If the sampled voltage is less than the internal reference voltage, it will increase the PWM output

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If the sampled voltage exceeds the internal reference voltage,

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the chip considers that the output is overvoltage

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The chip then controls the conduction of the upper and lower tubes, reducing the output voltage

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This is called feedback regulation

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FB pins of some chips can be grounded or connected to power supply,

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which is used to set the fixed voltage of PWM output

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For details, you need to consult the pin definition in the chip data manual

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We have a formula here: Vout=VFB*(1+R1/R2)

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At the same time, we can also adjust the output voltage by changing the resistance value

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Ok, so this is the introduction of the feedback regulation