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The loss contribution of a 2.3kW synchronous GaN-HEMT boost converter for an input voltage of 250V and an output voltage of 500V was analyzed. A simulation model which consists of two parts is introduced. First, a physics-based model is used to determine the switching losses. Then, a system simulation is applied to calculate the losses of the specific elements. This approach allows a fast and accurate system evaluation as required for further system optimization.
In this work, a hard- and a zero-voltage turn-on switching converter are compared. Measurements were performed to verify the simulation model, showing a good agreement. A peak efficiency of 99% was achieved for an output power of 1.4kW. Even with an output power above 400W, it was possible to obtain a system efficiency exceeding 98 %.
This paper presents an efficient implementation of a reconfigurable battery stack which allows full exploitation of the capacity of every single cell. Contrary to most other approaches, it is possible to electrically remove one or more cells from the battery stack. Therefore, the overall capacity of the system is not restricted by the weaker cells, and cells with very different states of health can be used, making the system very attractive for refurbished batteries. For the required switches, low-voltage high-current MOSFETs are used. A demonstrator has been built with a total capacity of up to 3.5 kWh, a nominal voltage of 35 V, and currents up 200 A.
This paper presents a compact 3 kW bidirectional GaN-HEMT DC/DC converter for 360V to 400-500 V. A very high efficiency has been reached by applying a zero voltage turn-on in conjunction with a negative gate-source voltage, even though normally-off HEMTs are used. Further improvements were achieved by adapting the switching frequency to the load current and output voltage, as will be explained by means of the loss contribution of the specific elements for a constant and an adaptive switching frequency. Measurements have shown a high converter efficiency exceeding 99% over a wide output power range of up to 3 kW.