The Design Of A Buck DC-DC Converter With High Efficiency And Wide Output Voltage Range

With the rapid development of IC technology industries,and with the increasingly prevalent in portable electronics. Intelligent devices are also booming, such as notebook computers, smart phones, smart TV, car navigation, vehicle traveling data recorder, etc. This will become the mainstream in the future. Combined with the characteristics of this product,such as the portability of laptop, the stability and durability of smart phone battery. The requirement of battery life becomes more and more high,which results in the greater demand and the higher requirement for switching power supply, such as higher efficiency, lower power consumption, stronger driving skills and the ability to withstand voltage, etc. So this paper designs a high efficiency wide input range type Buck DC-DC converter. Firstly we analyze the basic type of Buck DC-DC, the basic principle of the characteristics of the feedback control model, then explains the key technology in the design of switch power supply, such as reducing power consumption of synchronous rectifier technology, guaranteeing the stability of the loop by using the loop compensation technology, improving the efficiency of the working mode switching technology and so on.Finally,based on the application requirement for the design of DC-DC converter. We adopt a peak current mode control mode DC-DC converter,and then all of the function modules of this whole chip system are presented and analyzed in the following. The function parts include error amplifier and PWM comparator in voltage loop. The current loop includes current amplifier, OSC and bandgap reference and so on. Finally, based on 0.35?m BCD-MOS technology, the buck DC-DC converter is simulated and verified by spectre.The simulation result shows that the input voltage range of this switch power supply is 4.5V¹6V, the output voltage range is 1.8V^Vin-3V, the max load current is 3A, the typical load current is 1A, the frequency of OSC is 1MHz. This system achieves wide output voltage range and high conversion efficiency which can be as high as 94%. The converter works in DCM mode in light-load condition to improve the efficiency. However when the converter is in heavy load,this chip would work in hiccup operation mode. To prevent the case that the large current damaging the circuit system. In order to further improve the conversion efficiency,the dead-time control circuit is adopted to reduce conduction loss. What's more, the power loss induced by reverse current is presented by zero-current comparator. Finally, the over-temperature protection circuit and the over-current protection and under-voltage locked protection module are added in the chip system to ensure the safety of the chip operation.