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Hello everyone, today we are going to learn about the PWM circuit working mode

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Most PWM circuit chip in laptop mainboards can work in two different modes

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They are PWM mode and SKIP mode

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SKIP mode is also called SKIP pulse mode, or interval mode

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Most PWM chips work in both modes

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The purpose of these two modes is to adapt to different sleep state output different current

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The standby chip, for example,

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is in standby state until the adapter is plugged in and the switch is not pressed

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The system needs small current,

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at this time, it can work in skip mode, such as 3.3V standby, 5V standby

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In the standby state, it only needs to satisfy the normal work of the standby circuit

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In standby state, CPUs, graphics cards and many other high-power chips have not started to work,

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so the power consumption is very small

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Then 3.3V standby and 5V standby do not need to output large current, they can work in SKIP mode

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The output current is small, but the output voltage is constant

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When we press the switch, after the system runs,

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the high current can meet the CPU, graphics card and other chips normal work

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At this time, 3.3V, 5V will need to work in the PWM mode

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In this mode, its output current increases,

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but the output voltage remains the same

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Through the oscilloscope to observe the inductor front-end waveform,

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we can see it

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In the PWM mode, by observing the pulse waveform of the upper and lower tubes,

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it can be seen that the boot state work in the PWM mode

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The pulse is very close

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In SKIP mode, the pulse is intermittent

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For example, this pulse period and the next pulse period are continuous,

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there is no interval

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And in SKIP mode, SKIP mode refers to the shutdown state, standby time

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There's a dead zone between one of its periods and the other

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In this dead zone state, the upper tube G pole has no high voltage and the lower tube G pole is also low level

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There is an interval between one pulse and the next,

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which we call the interval, and this is called SKIP mode

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It obviously operates in different frequencies in these two modes

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That is, in SKIP mode, it takes a break every cycle,

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and neither the upper tube nor lower tube is working, and that's called the pulse interval

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But in PWM mode, in the boot state, the upper and lower tube G pole is a continuous pulse,

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there is no dead zone in the middle

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When the upper tube G is extremely high, the lower tube G pole is low

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When the lower tube G is extremely high, the upper tube G pole is low

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So continuous, with no gaps, no dead zones

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Therefore, in PWM mode, its operating frequency is relatively high, the output current is relatively large

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In SKIP mode, its operating frequency is relatively low,

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the output current is small, but the output voltage is unchanged

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Ok, so that's the working mode of PWM circuit