Application and Benefit Analysis of Guard Ring Methods in Reducing the Maximum Electric Field of Half Bridge Power Module

Insulation problems caused by high local electric fields in medium-voltage power modules are one of the key constraints on their development. This paper proposes a novel approach to reduce the maximum electric field of direct bonded copper substrates by adding guard ring with a specific voltage between the high-voltage island, output island with varying potential and grounded island on the top layer. Through finite element simulations, the optimal parameters including geometric parameters and optimal guard ring potential for the guard ring structures are determined. Furthermore, a low-cost integrated voltage divider structure is used to obtain the optimal guard ring voltage. Simulation results show that by using these methods, the maximum electric field can be decreased by up to 21% in a conventional medium voltage power module structure. This approach, due to its operation simplicity and electric field reduction, shows promise as a method to enhance the insulation level of medium voltage power modules.