My original laptop charger is not working, can i use a new charger ? whose input 100-240v-2.4a (2.4a) 50-60hz and output 20v(20v)== 4.5a(4.5a). My original cahrger input 100-240v~1.7a 50-60hz and output 20v(20v) == 3.24a(3.24a).
Your best bet is always to replace it with an identical device from the original equipment manufacturer.
However, the entire point of the power brick that comes with a laptop is to convert wall power into something the device can use. As long as the output voltage matches, and the amperage is sufficient, it should work fine.
Just make sure to check the connector fit and polarity. You don't want a loose connector (it could spark) and you really don't want to reverse the polarity.