The concept is ready. Motor, battery, safety system – everything is there. Only the inverter needs to be chosen. That is, where it becomes difficult. You are looking for a MOSFET based AC-inverter that neatly integrates into your plans but you are confronted with a lot of different offers that deliver a completed box with a pre-defined interface and functionality – nice, but not what is needed.
MOSFET based AC-inverters are around for more than 20 years and have evolved gradually together with their lead-applications into the ready to use products they are today. However, new application fields and new requirements for safety lead to a wide range of application-system designs that are not easily aligned with the existing AC-inverter designs in respect to their requirements regarding interface, functionality and safety. At the same time, MOSFET based AC-inverters do not typically lever unique selling points in the end-application, limiting the resources and money that can be spend for system integration and later series prices.
There is a mismatch between the physical interface of the inverter and the hard- and software interfaces that are required by the application-system. Of-the-shelf inverters today have a fixedly installed control-board, often including the software. From application-system design perspective, the controller and software should be preferably part of the control and safety-system design.
What are the options to get a product that meets the requirements? Even if the control-part of the inverter can be designed in-house as a perfect match to the application-system, developing a new customized power-inverter is difficult. The high currents require a dedicated power technology for the switches and an attached bus-capacitance with a very low inductive connection to them.
Alternatively, the design-process can be turned around – choose a freely-available inverter and build the rest of the application-system around it to meet the spec. This will always be a compromise at best. Finally a customer specific design can be requested from a suitable supplier resulting in a customer specific product with significant development cost and invest of resources.
What is missing, are building block concepts that overcome the mismatch of the interfaces. A concept for the power-stage of the inverter, comprising of MOSFET-modules, gate-driver and bus-capacitance and sensors, that is free to be connected to a control-system that is specifically designed to get the best integration of the AC-inverter-system in the overall application-system.
Based on the SKAI2 LV product family SEMIKRON has designed a gate-driver-only (GDO) derivate to meet the demand for flexibility of the control section. GDO delivers a powerful MOSFET-inverter stage with an easy to connect gate-driver, current sensors as well as temperature sensors and reserves sufficient space under the protective cover to mount a customer-specific control-board side-by-side to the gate-driver board. The complete gate-driver requires only a single 12V supply and signals are already scaled for direct connection to the processor.
The SKAI2 LV product family supports battery voltages with a wide range of robust inverters, traditionally rated for 36V/48V and 80V batteries and maximum supply-voltages of up to 72V and 115V respectively. SKAI2 LV inverters have a very low resistance down to 0,3mOhm (typ.) per switch in 48V systems and 0,8mOhm (typ) per switch in 80V systems and excellent thermal resistances combined with low switching losses.