Dear Forum,

I have a problem with the microcontroller 18f4550.
I use its PWM for controlling a driver mosfet, and it goes to the boost converter mosfet. The output of the PIC should be 5Volt DC 150kHz 70% Dutycycle. I tested the output (without connecting it to the driver and the boost converter) and it is running well..

I connect the converter with the microcontroller, it worked well and in a short time it became very hot, the driver did not give any output and offcourse the mosfet waas not switching. I dont know the reason for that.

Anyone knows something about this?

 

Can you post up a schematic?

 

First, did you put a resistor between the gate of the MOS and the output of the PIC with a value of at least 200 ohms?
Second, at such high frequency the current a PIC can provide (25mA max for each I/O) is not enough to turn on the MOS fast. You need to use a BJT at the output of the PIC to drive the MOS. Also, you will need to put a 500 ohm resistor between the gate and the source of the MOS as to turn it off.
I think the PIC is gone, so replace it.

 

10kHz is about the limit for a PIC to directly drive the gate of a logic-level MOSFET, unless the total gate charge is extremely low (as in the case with a 2N7000).

As Mik3 mentions, you must use a 200 Ohm resistor between the gate and the PIC to limit the maximum current to 25mA. However, the 500 Ohms from gate to source is much too low; it should be 5k-10k.

If you really want to drive your MOSFET in the 150kHz range, you should use a MOSFET driver IC. Microchip makes a variety of such driver ICs. Consult the applications notes before ordering.

 

1
If you really want to drive your MOSFET in the 150kHz range, you should use a MOSFET driver IC. Microchip makes a variety of such driver ICs. Consult the applications notes before ordering.

I use IR2301 driver IC. so PWM signal comes from microcontroller, this signal will get into the driver and then the driver controls the mosfet.

 

Can you post a schematic of the circuit? Maybe the PIC is getting hot due a short on the pcb tracks. Check it.