I am using the MP6908 controller in designing a Flyback, which output voltage is 25V.
The maximum voltage across the SR mosfet is 150V. Frequency is around 100kHz. The SR mosfet I am using is a 200V, <40mohm device.
In order to have 9V gate output I am following the datasheet indications of Fig. 6A by connecting the HVC pin to the SR mosfet drain through a 1000ohm resistor.
Despite this, the controller is overheating. If I use a higher value resistor (not reccomended by the datasheet though), the resistor itself dissipates too much. On the other hand, if I go down to the minimum recommended value (300ohm) the controller itself reaches very high temperatures.
Is this excess of heat normal in this application with this voltage level? It is still within the recommended values window. Do I need to select a high power resistor to supply safely the controller or there is any trick you can suggest me?
By the way, using a diode in series with the resistor does not help.