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What is the difference between PWM output and SPWM output in MP3 IC

News by ninechip | On 2018-12-24 10:51
When most people buy a voice chip, it's very easy to see the chip as a PWM output or SPWM output. What is this PWM and SPWM up to? What is the difference?
PWM is the abbreviation for Pulse-Width Modulation. It is a very useful skill to use the digital output of microprocessor to control the analog circuit. It is widely used in many fields, from measurement and communication to power control and modification.
With the development of the electronic skills, it presents a variety of PWM skills. It involves a voltage control PWM, pulse width PWM, random PWM, SPWM, and a voltage control PWM. And the pulse width PWM method, which is used in the ni-mh battery smart charger, is a pulse that equates every pulse width of every pulse as a PWM waveform, and it changes the period of the pulse train to the frequency and the width of the pulse, or takes the air ratio, and uses the appropriate control to change the voltage and frequency harmoniously. It can adjust the cycle of PWM and duty cycle of PWM to reach the intention of controlling charging current.
PWM is not only economical, space saving, strong anti-noise function, but also a useful skill worth the majority of engineers in many planning applications.
SPWM is to change the modulation pulse method on the basis of PWM. The duty cycle of pulse width is arranged according to the sinusoidal rule, so that the output waveform can be output by sine wave after proper filtering. It is widely use in dc communication inverters, such as some high UPS. The three-phase SPWM is using SPWM to mimic the three phases of the market, and it's widely used in the range of inverters.
The signal of the sinusoidal PWM is sine wave, which is the sine wave equivalent to a series of rectangular pulse waveforms of equal width. The pulse width is generated by the natural intersection of sine wave and triangle wave. There are many ways for sinusoidal waveforms to occur, but there are three typical methods: symmetrical regular sampling method, asymmetrical regular sampling method and uniform symmetrical regular sampling method. In the first method, because the PWM pulse width generated is relatively small, the output voltage of the frequency converter cannot reach twice the dc side voltage. In the second method, sinusoidal waves are sampled twice in a carrier period, and the output voltage is obviously higher than the former. But in terms of microprocessors, it increases the amount of data processing and when the carrier frequency is high, it's higher for the microprocessors. The third approach, which is most widely used, combines the strengths of the first two. Although the three-phase sinusoidal voltage can be obtained by SPWM, the voltage utilization rate on the dc side is low, and the maximum voltage is twice than that on the dc side, which is the biggest disadvantage of this method using to sound chips.
Therefore, the final purpose of both SPWM and PWM is to achieve closed-loop adjustment by adjusting duty cycle, so as to drive mp3 module.
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