Review of the Adaptive On-time Control Circuits for Buck Converters

Many novel control circuits, such as central processing unit and electronic devices, have been reported for power supplies to meet stringent requirements in recent years. These devices can reduce standby power loss and increase the load transient response to achieve high performance and low loss of system design. Owing to the rapid development of microprocessors, over a billion transistors have been integrated into one processor.The power converter must be able to regulate its output voltage to be near constant as the load current demand varies anywhere from zero to full load, even when the change occurs in a relatively short time. A good performance of load transient response can save on output capacitor size and cost. Meanwhile, settling time and stability can be displayed in the load transient response, so power converter performance must be tested. Based on these requirements, the conventional constant on-time control circuit is widely used in central processing unit applications and other electronic devices with high slew rates because of the advantages of faster load transient response and better light-load efficiency compared with the current-mode control circuit.However, the on-time generator circuit of the conventional constant on-time control circuit can generate the fixed on-time width to control the driver circuit and achieve the voltage regulation if the conventional constant on-time control circuit wants to regulate a high VOUT and an increase in switching loss occurs, so this chapter is showed to compare different types of control circuit for buck converter like conventional constant on-time control circuit for buck converter, adaptive on-time control circuits for buck converter, ripple-based adaptive on-time control circuit with virtual inductor current ripple for buck converter, and current-mode adaptive on-time control circuit for buck converter.