The bigger dangers are when the power source is at the wrong voltage. When the inverse situation,having a 12V 20A charger and having a device connected to it that only draws 0.6A, the load (device that is charging) will only draw the 0.6A it needs, even if the charger can supply 20A.Īs far as AMPS go, the load draws what it needs, or less if it is not available, and the power source supplies what the load needs by virtue of the laws of physics, unless it CANNOT.
There is potentially more danger is using a charger rated lower than the load requires, but usually only if there is no current limiting circuit or those circuits fail. Bigger Voltages means you can deliver the same wattage at lower currents (which is the most dangerous part of electricity) So when you plug in a PD charger, there is a digital negotiation of rates, once that occurs, the charger will set the voltage to the desired rate and allow current to flow as much as is needed, or as much as it can.įor instance, if you have a 12V 0.6A charger, it can only deliver 0.6A at 12V, usually that means that it is current limited, or that having a load of over 0.6A will cause the voltage to drop below the rated levels. PD simply allows the negotiation of charging voltages, and the charger circuit and the draw of the loads circuit will determine the rest. (the Apple 5 Watt charger that has come is most phones since 2007 is 5V 1A or 5V x 1A = 5W) That's why on many older USB chargers (before PD) they were all 5V N Amps. I can supply that V Volts at a current UP TO I AMPS, or in terms of the POWER, P WATTS (which is a function of voltage and Current). The TL DR is to think of a power adapter (the general sense, putting PD aside for now) as a device that says: I supply power at V Volts. In general, power adapters will only ever deliver the power they need to.
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