Can I use 1000W (220 V down to 110V) voltage converter for my wireless router?
That depends on your converter. The lightweight 1000 watt converters are suitable for heating appliances but not electronic items. This is because the method they use to reduce the voltage doesn’t actually reduce the peak voltage. They work by switching the full voltage on and off quickly so that the average voltage is lower. A converter of that type will burn out your router’s power supply. You need a transformer type of voltage converter. These are commonly available in the 50 watt (or VA) range. A transformer type converter in the 1000 watt size will weigh about 20 lbs.