Development of High-Temperature Optocouplers for Gate Drivers Integrated in High-Density Power Modules

In this article, a high-temperature optical galvanic isolator was developed. Details on the packaging layout, LED to emitter configuration, mathematical models, and device integration in the circuit are discussed. Evaluation of other optical isolation techniques is characterized and compared. The designed package for the low-temperature cofired ceramic-based (LTCC-based) optocoupler results in a higher electrical performance showing better signal stability and current transfer ratio. The optocouplers were stressed over a range of temperatures up to 250°C. Due to the new packaging implementation, the isolators exhibit higher output at elevated temperatures. DC characterization, transient characterization, isolation voltage, and the common mode transient immunity characteristics of the isolators were performed at 25°C and up to 250°C. The optocouplers were integrated into a gate driver circuit that utilizes LTCC as a substrate to understand the integration capabilities. The double pulse test results of the gate driver show reliable and consistent switching capabilities from 25°C to 250°C. As a result, an LTCC-based gate driver circuit is achieved to be integrated into a high-density power module.