BUCK DC-DC CONVERTER WITH FIXED FREQUENCY

摘要

A buck switching regulator implements a fixed frequency feedback control circuit including a voltage control loop and a frequency control loop to regulate the switching frequency of the buck switching regulator to a fixed or nearly fixed frequency. The voltage control loop, implementing ripple mode control, is configured to control the power switches in response to the switching regulator output voltage or a signal related to the switching regulator output voltage. The frequency control loop, implementing a phase-locked loop control scheme, is configured to adjust the on-time of the high-side switch so as to regulate the switching frequency to be equal to or be proportional to the reference frequency.

主权项

1. A buck switching regulator being configured to receiving an input voltage and to generate a regulated output voltage, the buck switching regulator controlling a high-side switch and a low-side switch based on a feedback control scheme to drive a switch output node for generating a switching output voltage, the switch output node being coupled to an LC filter to generate the regulated output voltage having a substantially constant magnitude on an output node, the buck switching regulator comprising:
a controller circuit configured to generate a high-side turn-on signal and a low-side turn-on signal, the high-side turn-on signal being asserted to turn on the high-side switch and the low-side turn-on signal being asserted to turn on the low-side switch, the high-side turn-on signal and the low-side turn-on signal being asserted alternately to turn on the high-side switch and the low-side switch alternately to generate the switching output voltage, the switching output voltage having a switching frequency defined by the on-time and the off-time of the high-side switch; a voltage control loop configured to cause the controller circuit to assert the high-side is turn-on signal to turn on the high-side switch in response to a feedback signal being equal to or less than a reference signal, the feedback signal being indicative of the regulated output voltage; and a frequency control loop configured to cause the controller circuit to deassert the high-side turn-on signal to turn off the high-side switch in response to a frequency correction signal related to a phase difference between an input frequency and a reference frequency, the input frequency being related to the switching frequency, wherein the voltage control loop is configured to adjust a duty cycle of the high-side switch to maintain the regulated output voltage at a desired voltage level while the frequency control loop is configured to adjust the on-time of the high-side switch to maintain the switching frequency to within a frequency range of the reference frequency.