Discussion on the understanding of PWM

Discussion on the understanding of PWM

1. What is PWM?

PWM (pulse width modulation) is a simple frequency conversion technology, is to change the pulse width to control the output voltage, by changing the period to control its output frequency. If it's not clear enough, well, let's take a look at the examples in our real life, why do we have to twist the fan, the speed of the fan will change; adjust the sound button on the radio and the size of the sound will change. It's still going to be a while. The buzzer will also emit different frequency calls according to different input values and so on!! These are PWM applications, which are controlled by the frequency signal of the PWM output.

2. Type and operating principle of buzzer

Buzzer is mainly divided into piezoelectric buzzer and electromagnetic buzzer two types.

Piezoelectric buzzer mainly consists of multi-harmonic oscillator, piezoelectric buzzer, impedance matching device and resonance box, shell and so on. Some piezoelectric buzzer housings are also equipped with light-emitting diodes. A multi-harmonic oscillator is composed of transistors or integrated circuits. When the power supply (1.5~15v DC operating voltage), multi-harmonic oscillator, output 1.5~2.5khz audio signal, impedance matching device to promote the sound of piezoelectric buzzer.

The electromagnetic buzzer consists of an oscillator, an electromagnetic coil, a magnet, a vibrating diaphragm and a shell. When the power is switched on, the audio signal current generated by the oscillator passes through the electromagnetic coil, causing the electromagnetic coil to generate a magnetic field. Vibrating diaphragm in the electromagnetic coil and the interaction of magnets, periodic vibration sound.

Active buzzer and passive buzzer difference: This "source" word is not refers to the power supply, but refers to the source of the oscillator, that is, the active buzzer has an oscillating source within the passive buzzer inside no oscillator source. The power of the oscillation source can be audible, without the need for the oscillation source pulse signal driver to be audible.

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Discussion on the understanding of PWM