Research On LDO With High Transient Response For GaN Driver

GaN power devices with excellent conduction characteristics and switching characteristics are gradually replacing traditional silicon-based devices.However,the power supply module of the driver is required to have better transient response performance and larger current output capability due to the fast switching speed and poor gate breakdown characteristics of Ga N power devices.In addition,the requirement of high integration makes the traditional LDO structure with external capacitors no longer applicable.Therefore,it is of great significance to design an integrated LDO with high load current and high transient response characteristics for Ga N driver.The advantages of GaN and the need for an capless LDO with high load current and high transient response characteristics is firstly analyzed in this thesis.Next,the basic structures and the main characteristics of LDO are described.In this part,the stability mechanism and transient response characteristics are especially mentioned,as long as the common stability compensation methods and transient response promotion methods.In view of the above problems,a capless LDO with high load current and high transient response characteristics is proposed,which consists of a cross-coupled common gate amplifier,a gate driver stage,an adaptive bias current module and a transient response enhancement circuit.The cross-coupled common gate amplifier with wide bandwidth ensures the loop stability in the full load current range.The gate driver stage constructs a low-frequency main pole to improve the loop stability further.The adaptive bias current module adjusts the bias current of the error amplifier adaptively by detecting the change of the load current,which improves the slew rate and bandwidth of the error amplifier when the load current is large.The transient response enhancement circuit dynamically improves the transient response characteristics by detecting the change of the output voltage.Based on 0.18?m 45 V BCD(Bipolar-CMOS-DMOS)process platform and the Cadence tool,a high load current and high transient response LDO circuit is designed and performs post-simulation in this thesis.The results show that when the load current changes between 0m A and 300 m A instantaneously within 100 ns,the maximum overshoot voltage and undershoot voltage of the LDO are 42.87 m V and 66.77 m V,which meets the design requirements.