Research And Design Of Buck Converter With Floating Gate Width And Gate Voltage

Global energy is in a crisis and the human apptite for energy is growing. In order to ease this dilemma, searching for new energy as an alternative and improving the efficiency of energy become today’s two majoy problems. While electricity is the most widely and directly energy form, improve the efficiency of electricity is the most effective way. With the popularity of handheld products in recent years, how to prolong the handheld device life in standby mode catches people’s attention widely. And device will be in light load for a long time when it is in the standby mode. So how to improve efficiency of the handheld products, especially in light load is of great significance.This thesis focuses on the double N-type power MOSFETs Buck DC-DC efficiency promotion technology, proposing a power MOSFETs driver with a floating gate width and gate voltage. Through the theoretical analysis of the loss of Buck converter, the main sources of loss(gate drive loss and conduction loss) has been optimized. The total loss is modeled as a function of power MOSFETs driving voltage Vgs and width W. Under different loads, the combination of Vgs and W corresponding to the minimum loss points is the optimal driving scheme. According to this rule, drive scheme is proposed: with the load decreasing, the conduction segment is decreased, and the gate floating voltage mode is activated when only one segment is activated. The main design concept is: according to preset relationship betweent driving scheme and load, using the load current information from the PCM loop, the corresponding segments is opened and the gate driving voltage is adjusted to reach total loss optimization.This thesis starts with analysis of power consumption and demonstrates the existence of optimal driving scheme. Based on that, the relationship between the load current and drive solution is obtained. And then combining with PCM control mode, current sense, PWM comparator, segment control, and floating gate voltage module are completed and design points and the each module’s simulation results are presented. Finally, the whole system simulation and layout are given. Under the load current of 150 mA, 10% efficiency improvement is achieved, verifing the feasibility of design ideas.