Control circuit and method for providing a signal for a PWM voltage regulator to convert an input voltage into an output voltage

摘要

A control circuit and method for a PWM voltage regulator combine a high frequency feedback technique with a constant on-time or constant off-time topology to improve the transient performance of the PWM voltage regulator. The PWM voltage regulator generates a constant on-time or constant off-time depending on a current for generating a PWM signal, and dynamically adjusts the current according to the droop-voltage at its output during a transient period. Therefore, the PWM voltage regulator boosts its transient response without any threshold for load step detection.

主权项

1. A control circuit for providing a PWM signal for a PWM voltage regulator to convert an input voltage into an output voltage, the control circuit comprising:
a constant-time generator generating a constant time to determine a constant on-time or a constant off-time of the PWM signal; and a high-frequency feedback controller connected to the constant-time generator, operative to establish a high-frequency feedback loop responsive to transient of the PWM voltage regulator, to adjust the constant time instantly; wherein the high-frequency feedback controller comprises a bypass capacitor parallel connected to a serially connected quick response capacitor and quick response resistor; wherein the constant-time generator comprises: a capacitor; a current-controlling current source connected to the capacitor, for determining a second current according to a first current to charge the capacitor; a switch connected in parallel to the capacitor, for resetting the capacitor; and a comparator connected to the capacitor, for comparing a voltage at the capacitor to a reference voltage to generate the PWM signal.