Local power supply for efficient high-voltage power electronics modules

In power electronics, the main goal is to be able to produce modules that are as efficient as possible. This field of the electronics aims at converting electrical power from one form to another. Especially when working at high power levels, the thermal dissipation is high and a dedicated cooling system is therefore needed. This means that the overall circuit will take a lot of space and be more expensive. In order to tackle this problematic, it is needed to explore new technologies such as wide bandgap semiconductors which can sustain higher voltages and operate at higher temperatures. By using such components it is possible to design power electronic modules that are more compact and make the conversion in a more efficient way. The focus of this master thesis is the design of a local power supply for power electronic modules. This power supply will work as a rough pre-regulator in order to convert an input voltage which could range up to 1000V into a fixed output voltage of 15V. A second constraint adds up to this first challenge: the circuit must be able to work properly up to 225 °C. For this purpose, a wide bandgap JFET is used as the pass element for a LDO-type structure. The use of such JFET allows to efficiently convert a high voltage input to a low voltage output. Furthermore, due to its wide bandgap, the operation temperature can be very high and the temperature constraints of this work is set by the XI10 technology which will be used. The high value of the gate capacitance of the JFET will induce a low-frequency dominant pole for the open-loop transfer function. In addition to this pole, there is a second one created by the output capacitor. It is therefore necessary to add a zero inside the bandwidth of the regulator. The resulting design yields a phase margin of about 75° which is necessary in order to have a phase margin that is above 45° in all PVT conditions. The addition of the zero inside the bandwidth makes this condition necessary but not sufficient and it is therefore needed to look also at the transient response. The latter indicates an error on the output voltage that is lower than -45dB for all PVT corners with a typical error of -75dB and an overshoot on the output voltage which is lower than 10% of the nominal voltage. By sizing the different components appropriately it is possible to achieve a typical line regulation of 6.2 %/MV and a load regulation of 0.98% which is comparable to similar products already present on the market.