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PWM is how to adjust the brightness of LED, many novices are not very clear about this, in order to help you solve this problem, the following editor will explain in detail for you, people with this need can come to learn, I hope you can gain something.

The brightness of light emitting diodes can be controlled by PWM. Light-emitting diodes are current-driven devices, the greater the current flowing through the light-emitting diodes, the higher the brightness, but when driving a small number of light-emitting diodes, it is generally realized by current-limiting resistors, which can not adjust the brightness. If you want to change the brightness, you have to use PWM to achieve, not only that, PWM can also be used to achieve motor speed regulation and other functions. The following figure is a commonly used LED driver circuit.

In the above figure, the GND is connected to the PWM signal and the duty cycle is adjusted to realize the change of different brightness of LED. The duty cycle of PWM represents the average voltage. After the duty cycle changes, the average voltage at both ends of LED and current limiting resistor will change, so the current flowing through LED will change. This is the principle that PWM adjusts brightness. The smaller the duty cycle of PWM, the brighter the LED.

After driving the LED through the transistor, the PWM signal is connected to the base of the transistor, and the LED and the current limiting resistor are connected to the collector. At this time, the duty cycle of PWM is proportional to the brightness of the LED. The greater the duty cycle of PWM, the brighter the LED.

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