Switching voltage regulators with hysteretic control for enhanced mode-transition speed and stability

摘要

Switching voltage regulator embodiments are provided with hysteretic control to thereby switch between pulse-width modulation and pulse-frequency modulation operational modes. The switching is in response to different levels of an error voltage Verr in the feedback loop of voltage regulators. The hysteretic control is configured to provide a dc hysteretic response to changes in the error voltage Verr and also an ac hysteretic response to these changes. These two responses can be independently set to thereby enhance operational speed of the voltage regulators and also enhance immunity to transient noise signals that are generated by the mode switching. The voltage regulator embodiments facilitate instant return from the pulse-frequency modulation operational mode to the pulse-width modulation operational mode so that the stability of the feedback control of the regulator is enhanced. This feature is especially useful when the feedback loop is configured to include current-mode control as it minimizes the time duration in which the feedback loop operates in a voltage-mode control. The instant return insures that the feedback loop is immediately returned to the greater stability of the current-mode control.