Design Of Digital COT Control Circuit For DC-DC Converter

In the upgrading of electronic equipment,the requirements for power supply are getting higher and higher.It is not only to provide a stable voltage and current,but also to realize monitoring,protection,online debugging and upgrading,and intelligently adapt to the needs of different application scenarios.As a result,the advantages of the digital power supply have gradually emerged.The digital power supply can be programmed to flexibly change the parameters of the control loop,making online debugging easier.Compared with analog power supplies,digital programmable power supplies have better compatibility and reliability.Through the communication bus,monitoring and protection functions can be realized more flexibly,and even fault prediction can be realized.At the same time,thanks to the reduced feature size of the CMOS process,the digital power supply can achieve a higher level of integration,which is more conducive to integration in a larger So C.The traditional digital power supply is controlled by a voltage loop,and its control loop bandwidth is limited.The digital quantization of current signals requires high-precision,high-speed ADC converters,which poses higher challenges in integrated circuit design.This paper presents a digital COT control Buck converter circuit.By analyzing the principle of DCR current sampling circuit,a new digital inductor current sampling scheme is proposed.The digital current sampling scheme proposed in this paper is mainly composed of a transconductance amplifier,a Current Controlled Oscillator(CCO)and a digital filter.The time constant of the digital filter matches the time constant of the inductor DCR,and the current signal can be losslessly converted to digital domain to realize digital current mode control.The ADC is not used for analog-to-digital conversion in the sampling path,which avoids the use of high-speed current sampling ADCs and can effectively improve the response speed of the current loop.In addition,adaptive digital slope compensation is added to the voltage outer loop to further improve the transient response speed.The digital COT control scheme proposed in this paper can further improve steady-state accuracy and transient performance compared with traditional control schemes.Through the introduction of analog ripple to assist in enhancing the transient response capability of the digital system,at the same time give full play to the advantages of the digital control circuit to enhance the steady-state accuracy.The key parameters of the compensation unit and timing unit can be flexibly changed through the communication interface,so that it has a larger scope of application.The digital COT-controlled Buck converter proposed in this paper has been simulated at the circuit level.When the input voltage is 5V,the output voltage is 3.3V,and the switching frequency is 1MHz,the load up-step and down-step response times reach 13μs and 19μs,respectively.The overshoot range is within 42 mV,and the output accuracy reaches 7.6mV.