Design of COT Control DC-DC Buck Converter with Acoustic Noise Cancellation

With the development of BUCK converters, a wide variety of control methods have been further optimised for better and better performance. However, all of them are currently seldom considering the problem of acoustic noise. This article proposes a DC-DC BUCK converter with acoustic noise cancellation based on constant on-time control, which can be applied to notebook computers and system power supplies. Aiming at the problem that the conventional DC-DC BUCK converter does not take into account the acoustic noise that may be generated by the Discontinuous Conduction Mode under ultra-light load conditions, the proposed design adds acoustic noise cancellation. The acoustic noise cancellation is achieved by monitoring the on-state of the switching MOS, and when the operating frequency of the switching MOS is about to enter the audible frequency range of the human ear, the switching frequency is forcibly raised to keep the switching frequency above 32kHz. Because no loop compensation is required, the transient response is extremely high-speed. The proposed design is realised using a 0.18umBCD process, the input voltage range is 6V to 28V, and the output voltage range is 2V to 5.5V. The transient response time is only 8.49us for a load from 2A to 8A, and the light load efficiency is 95.87% at a load current of 77mA.