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Hello everyone, in this lesson we will talk about the waveforms of common pins in PWM circuits

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First of all, let's talk about the explanation of several commonly used words in PWM circuits.

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Upper and lower tubes

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The upper and lower tubes refer to the field tubes in the PWM circuit,

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which are divided into upper tubes and lower tubes.

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The D pole of the upper tube is connected to the input voltage,

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and the S pole is connected to the D pole of the lower tube and the front end of the inductor.

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The D pole of the lower tube is connected to the S pole of the upper tube and the front end of the inductor

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The S pole of the lower tube is directly grounded

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Inductive front end

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Inductors are divided into front-end and back-end

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The front end of the inductor is connected to the S pole of the upper tube,

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the D pole of the lower tube and the phase pin of the chip

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The back end of the inductor is usually connected to a capacitor.

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Base voltage

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The base voltage refers to the basic voltage of the BOOT pin

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Generally, the power supply of PWM chips is 5V, and the power supply of some PWM chips is 12V.

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Its interior will generate a base voltage of 5V through an LDO module

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In PWM circuits, the base voltage is 5V in most cases

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Input voltage

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The input voltage refers to the voltage of the D pole of the upper tube

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Next, let's look at the waveforms of these important pins

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The first is the upper tube drive pin

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The drive pin of the upper tube is a waveform from 0V to the base voltage plus the input voltage

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The drive pin of the lower tube is a waveform from 0V to the base voltage

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The inductor front end is a waveform from 0V to the input voltage

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The BOOT pin is a waveform from the base voltage to the input voltage plus the base voltage

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The back end of the inductor is DC

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Let's apply it directly to this circuit

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First of all, for this circuit diagram, the input voltage is 5V, and the base voltage is also 5V.

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Then the waveform of the upper tube drive pin is the waveform of 0V to 10V

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The waveform at the front end of the inductor is the waveform from 0V to 5V

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The waveform of the drive pin of the lower tube is the waveform from 0V to 5V

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The waveform of the bootstrap presser foot is a waveform from 5V to 10V

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The back end of the inductor is a 1.5V DC