I have a pfc circuit that is being controlled by a ucc28019a PFC contorller. This controller an directly drive the mosfet but I want to use an extra gate driver. I want to use te signal generated by the controller to drive the gate driver. The problem is the controller outputs 12.5 volts and the gate driver can only take 6.5 volts on the logic input. How can this be done?

 

You can use a Zener diode (6.2v to be safe) to limit the voltage like 1N5341BE3/TR8 (5W) or BZX584B6V2-RSG (150mW) depending on your requirements.

 

I have a pfc circuit that is being controlled by a ucc28019a PFC contorller. This controller an directly drive the mosfet but I want to use an extra gate driver. I want to use te signal generated by the controller to drive the gate driver. The problem is the controller outputs 12.5 volts and the gate driver can only take 6.5 volts on the logic input. How can this be done?

If the 12.5V and 6.5V are constant, then a resistive divider will take care of it.
http://sim.okawa-denshi.jp/en/teikokeisan.htm
but you will need to take note of the capacitance on the driver input as it will slow down the pulse if the resistor values are too high.
Alternatively, find a driver that can take a 12.5V input. There are plenty that do.

 

Ian0 might be correct in this case. Using a Zener diode to clamp the voltage may cause excessive driving current at the gate output of the controller, which could potentially trigger the controller's protection fuctions.
A resistive divider might be a safer solution.

 

Thank you all for your answers. After some research I found out that there are gate drivers that can take up to Vcc on their logig inputs which solves my problem without having to step down the signal!