Design Study Of Low-power Current Mode Synchronous Switching Buck Regulator

With the development of information technology, computer-driven electronic information spawned a wide variety of electronic products, power management chip as the heart of electronic products, which are widely used in communications, networking, personal computers, automotive electronics and other fields. Power management chip has become an integral part of electronic products. Switching power management chip are used for all types of electronic circuits due to its advantage such as high efficiency, high output accuracy, high load current driving capability, high speed voltage dynamically adjusting, etc. In this paper, combined with the requirements of today’s wearable device, we focus on research of low power consumption and high efficiency current-mode step-down switching regulator design.The main work and innovation of this thesis lies in:1) The paper has model the circuit system in detail. In order to ensure the accurate modeling, MOSFET turn-on resistance, the DC resistance of inductance, capacitance equivalent series resistance and other non-ideal factor had been introduced in the system modeling.2) In order to reduce the static power switching power supply system, low power design is used in the design of the circuit module. The circuit adopted low power voltage reference without circuit resistors. In Oscillator design process, in order to make the oscillator power consumption as low as possible and small temperature coefficient, this paper had adopted non-resistance type low power current reference in our oscillator and it ensured the oscillator output stable and low temperature coefficient, the switching power supply oscillator frequency stability at 4MHz.3) Besides, the current mode control of switching power supply need to solve sub harmonic oscillation of the system circuit. The paper had proposed adaptive slope compensation circuit to solve the traditional compensation circuit over the issue ofcompensation and broaden the scope of work of the switching power converter.Thesis also analyzed circuit modules of the current mode step-down DC / DC converter in detail. To reduce the power consumption of circuit module in switching power supply system, the voltage reference section uses a new type of low power consumption and non-resistance-type circuit. Besides, current-mode switching power supply system need to solve its sub-harmonic problem in current loop. This paper presented a self-adaption slope compensation circuit to solve the problem of over-compensation and broadens the switching power converter operating range, compared to traditional compensation circuit. In the oscillator section, in order to make the oscillator power consumption and temperature coefficient as low as possible, the paper uses a low-power electric current without resistance-type reference, which also had low temperature coefficient; it made oscillation frequency of oscillator stabilized at 4MHz.Switching power supply circuit modules design was based on tsmc 0.18 um mixed-signal process library. The simulation results showed that switching power supply system worked at frequency of 4MHz. When the input voltage range 3V to 5V the current-mode switching power supply can be achieved and stabilized DC output voltage range from 1.5V to 2V. Compared with the voltage mode switching power supplies, current-mode switching power supply had lower linear adjustment rate, load regulation rate, and fast dynamic voltage regulation rate.