How to generate PWM waves with different effective values?

乱世煮酒论天下

How to generate PWM waves with different effective values? [Copy link]

How can a single-phase inverter circuit generate PWM waves with different effective values from a sine wave and a bipolar triangle wave? Which waveform parameter can determine the effective value of the output PWM wave?

The three-phase inverter circuit is generated by three sine waves and bipolar triangle waves with a phase difference of 120 degrees. Similarly, which parameter can be controlled to generate PWM waves with different effective values? Which waveform parameter can determine the effective value of the output PWM wave?

maychang

[Which waveform parameter can determine the effective value of the output PWM wave? ]

Obviously, changing the duty cycle is the simplest, which is also the result of comparing the triangle wave with the sine wave.

maychang

[Which waveform parameter can determine the effective value of the output PWM wave? ]

Use the word "reform" with caution.

乱世煮酒论天下

maychang posted on 2024-6-16 07:15 [Reform which waveform parameter can determine the effective value of the output PWM wave? ] Use the word "reform" with caution.

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qwqwqw2088

Since we are talking about PWM inversion, we must understand the principle of PWM inversion.

The duty cycle of the PWM wave is proportional to the amplitude of the sine wave

so,

Both generate PWM waves with different effective values by adjusting the amplitude of the sine wave.

Single-phase inverter adjusts the amplitude of a single sine wave, and
three-phase inverter adjusts the amplitude of the sine waves in three phases at the same time.

秦天qintian0303

The effective value of the output PWM wave can be changed by changing the duty cycle. Obviously, this is the simplest way.

振动试验仪器

The main circuit structure of the single-phase inverter voltage amplifier is very similar to that of the switch tube amplifier of the vibration table. The AC voltage output by the vibration table amplifier is always changing the frequency and voltage. Therefore, the frequency and voltage conversion method of the vibration table amplifier can be used for your reference.

振动试验仪器

The vibration table amplifier is the same type as the speaker amplifier, but it is mono and belongs to Class D amplifier.

The AC signal to be amplified is compared with a fixed high-frequency triangle wave in the LF311 comparator to generate a square wave. This square wave is used to control the main circuit to generate an amplified sine wave.

Adjusting the amplitude of the AC signal will change the output AC voltage. Changing the frequency of the signal will change the frequency of the output voltage synchronously.

Therefore, the signal control of the vibration table requires a special vibration controller.

振动试验仪器

That is, when the sine signal is converted into a PWM wave, the sine signal is changed from a fixed amount to an adjustable amount, and the size of the inverter voltage can be changed. The voltage can be adjusted from 0 to the maximum.

Increasing the voltage of the input sinusoidal signal means increasing the duty cycle of the square wave.

振动试验仪器

The effective value of the output PWM wave can be changed by changing the duty cycle. How to change the duty cycle? In the process of generating PWM, the high-frequency triangular wave remains unchanged, and changing the voltage of the sinusoidal signal will automatically change the duty cycle of the output PWM.