The yellow channel is Delta-Sigma, blue channel is PWM.

While PWM keeps it's frequency constant when increasing the duty cycle, Delta-Sigma increase the number of it's pulses and keeps the wide of each pulse constant.

This is how Delta-Sigma is avoiding flickering much better then PWM, but with the same computational effort.

Next is an animated picture at different duty factors, for the same computational effort.
At 50% duty cycle, Delta-Sigma have a maximum refresh rate of 1250 Hz, while PWM have only 10 Hz.

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