Abstract: Bootstrap gate drivers are widely used in phase-leg composed converters for their advantages such as less components and low cost. In high current converters, improper parameter design of bootstrap gate driver can lead to start-up gate-source voltage oscillation and phase-leg shoot-through, increasing the risk of devices and drivers failures and driving losses. Due to the lack of sufficient theoretical guidance in the parameters design of bootstrap gate drivers for high current converters, this paper studies and constructs a detailed model of the gate driver. Based on the model, the above fault mechanisms are studied, and the safety boundary for the parameter design of the gate driver is obtained. Then, the relationship between driving loss and the parameters is analyzed, and a universal optimum design method with fault protection and efficiency improvement is proposed. Simulations and experiments verify the accuracy of the theoretical analysis and the feasibility of the proposed approach.