I am using a 75watt power inverter in my car to power a laptop, after 3 min it blows my car fuse.?

I am trying to power my laptop in my car with a 75 watt power inverter, after 3 min it blows my cig lighter fuse. I tried a different brand 100watt one and the same issue, even if the car is running it blows. No clue what the problem is.