Over loading?

Never ever increase the size of a breaker unless you know the wiring from end to end supports it.

If a 15 A breaker is popping it is doing so for a reason.

It is however sometimes useful to exchange a breaker for the same size.  They don't last forever and a new one may fix your problem.

Look at the wattage on the back of the unit. So long as you don't exceed a combined 1500 watts you are fine.

The watts on the input and output are more or less the same, however because P = Current x Voltage, when you change the voltage (downwards) the Current may go upwards. 

That instant current capacity is not drawn from the outlet but from storage capacitors in the power supply.