Integrated Over Voltage Protection Circuits for Power Transistors

Nowadays, MOSFET and IGBT power components are widely used in medium and high power converters. They are subjected to increasing requirements: electrical performances, simple implementation, reliability, integration, smaller volume and price. Moreover, their integration process offers the possibility to reduce or eliminate the need for pick and place, bonding (wafer- and/or ball-bonding) and other assembly processes necessary in hybrid assemblies, and in the same time to add some useful functionality like sensors for protection and control. This paper presents an overview of integrated solutions for active over voltage protection circuits. A short state of the art presents the main integrated topologies and compares them. Technological, electrical and thermal compatibilities and interactions are investigated in order to outline what are the benefits but also the limitations of over voltage protection circuit integration. In particular, this analysis tries to evaluate the thermal impact of the protection circuit, which is a dissipative element, on the integrated die and the power switch. Monolithic and hybrid interconnects are also considered in the paper to outline possible benefits from the integration. Several results from simulations but also practice are available in the paper to validate comments and conclusions