Research On GaN Power Device Based DC-DC Switching Power Supply Control Chip

DC-DC converter is widely used power converter nowadays.With the development of Google's 48 V DC power supply system and new server 48 V to 1 V power supply architecture in electric vehicles,new requirements for high efficiency and high power density have been put forward for traditional DC-DC buck converters.To increase power density,the common solution is to increase the switching frequency.For traditional silicon-based power devices,due to the structural characteristics of the BUCK circuit,there will be large switching losses in highfrequency and high-input voltage applications.Compared with traditional silicon-based power transistors,Ga N power devices have the advantages of low resistor,small parasitic capacitance,and no reverse recovery charge,which are more suitable for highfrequency DC-DC converter applications.In this paper,the application of Ga N devices in DC-DC buck converters is studied,and two DC-DC buck converters are designed.For the new server power supply architecture proposed by Google,a DC-DC step-down circuit with a 5 MHz maximum input frequency,48 V input,5V 90 W output was designed.For the and the 48 V automotive electronic power supply system applications,aiming at the problem of high input voltage and high frequency BUCK circuit with high switching loss,a soft switching BUCK circuit design based on Ga N power devices has been implemented to achieve a low power output of 1 V 5 W with 48 V input.Among them,the design of the first chip adopted an adaptive on-time control method to deal with the short condution time problem caused by high frequency and low duty cycle.A high-precision on-time generator is used to eliminate the on-time error caused by the comparator delay.In addition,based on the problem of high reverse conduction voltage of the Ga N device,an adaptive dead time controller is designed to reduce the dead time loss.Under 2 MHz switching frequency,the converter reaches 90% peak efficiency at full load by simulation,and fast load response due to high switching frequency.The design of the second soft switch BUCK controller realizes the working mode of the soft switch with BUCK structure,and completes the closed-loop control of the entire system.The system uses PWM control and realizes functions such as resonance detection and dead time control.By taking advantage of the low parasitics of Ga N devices,the peak efficiency at a switching frequency of 500 k Hz can reach 93% by simulation.This design has been verified by simulation.The high-power DC-DC converter based on Ga N device can increase the switching frequency of the DC-DC step-down converter to higher than 2MHz on the premise of ensuring operating efficiency,thereby reducing the external inductor volume size by at least 50%.At the same time,at low power levels,Ga N devices can take full advantage of the soft switching BUCK topology,eliminate switching losses,and improve operating efficiency by about 10% compared to hard switching.