What Smite said. The charger and the device in question will initiate the handshake and when there aren't any compatible USB-PD charge rate that's agreeable between them, it'll default down to 5V1.5A, the lowest safe common USB-A charge rate. Bear in mind, the Switch isn't compatible with anything other fast-charge protocol other than USB-PD, but due to some poorly QC-ed chargers that combines these other fast-charge protocols with USB-PD, therein lies the danger: the device keeps querying for more power, the charger kept supplying it, which ultimately results in a brownout (best case scenario) or charger overheats and burns your house down while you left it charging at night while you sleep (worse case scenario). Not exaggerating, the Google testers who tested these out-of-specs cables and chargers have lost ports on their Google Pixel C, and in the case of Nathan.K, blown his entire PC power supply with it. Pretty scary.