In addition, Qg and input capacitance are reduced significantly, which translates into higher switching frequency and smaller external components. ![]() Switching designĪlternatively, a single SiC mosfet combines high breakdown voltage (1,700V) and 3.7A current rating with RDS(on) ranging from one half to one eighth of that of a comparable 1,500V silicon mosfet. The downside of this design is that it requires an isolated gate driver and power supply to control the high-side switch and, once again, each device has to be equipped with a heatsink. In addition, each mosfet also needs to be equipped with a heatsink, which increases the overall footprint.Īnother solution is to adopt a two‑switch flyback topology. They also tend to have high Qg, which causes high driving losses and leakage current, especially at high temperatures.Īn alternative is to connect two 800V silicon mosfets in series, but this requires a more complex gate driving circuit as well as a voltage balancing circuit. The problem with this approach is that high-voltage transistors manufactured using ordinary silicon come with relatively high RDS(on), which generally translates into unnecessary conduction loss and heat dissipation. One possible solution, for example, is to source a power transistor that has high breakdown voltage of around 1,500V. There are various design approaches that can be considered to ensure that the power transistor is able to withstand worst-case voltage applied across the drain and source terminals.Įach has its pros and cons. The sum of all these voltages can quite easily exceed 1,300V. The main power switch must, therefore, be able to withstand the worst‑case drain‑source voltage due to the reflected voltage deriving from the secondary side, as well as maximum turn‑off overshoot and DC input voltage. This is where a flyback converter is generally deployed. Its main purpose is to supply power to subsystems such as sensor modules, displays, and other control units or drivers. ![]() Equipment such as solar inverters, industrial DC‑DC converters and battery chargers, often feature an auxiliary power unit that runs off the main input. SiC power semiconductors can really make a difference in some typical applications. Figure 1: Mosfet switching waveforms at, from left to right, light, mid and full load
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