Gate Drive / Feedback
The requirement for the Gate Drive – feedback circuit varies widely from converter to converter. While some situations demand optical feedback due to high isolation, optical feedback can prove costly. Ferrite and nanocrystalline are good choices for feedback while maintaining isolation. These transformers often are small toroids usually with O.D. of around 8mm. Power material has typically not been the ferrite of choice due to the large magnetization currents of power materials. So the typically ferrite material is a higher perm ferrite, initial perm in the range of 3K – 6K as long as the ferrite operating temperature meets the converter temperature requirements.The TDK HF90 with it’s 5K perm and 165°C curry temperature meets the usually specifications.