Short circuit protection for a portable device powered by a battery pack having undervoltage protection

摘要

A portable device includes set of charger contacts and a set of battery contacts. The battery contacts mate with corresponding contacts of a battery pack used to power the portable device, and the charger contacts allow charging of the battery pack while connected to the portable device. The battery pack includes an undervoltage protection circuit that opens when an undervoltage condition occurs across the battery pack contacts. The portable device further includes short circuit protection element connected between corresponding contacts of the set of battery contacts and the set of charger contacts that, upon a short circuit condition occurring at the charger contacts, prevents the undervoltage protection circuit from tripping and opening.

主权项

1. A portable device, comprising:
a set of battery contacts including a positive battery contact and a negative battery contact; a set of charger contacts including a positive charger contact corresponding to the positive battery contact and defining a first pair of corresponding contacts, a negative charger contact corresponding to the negative battery contact and defining a second pair of corresponding contacts; and a short circuit protection element comprising a transistor switch circuit electrically coupled between a charger contact and a battery contact in at least one pair of the first and second pairs of corresponding contacts, wherein the transistor switch circuit comprises:
a transistor coupled between the at least one pair of the first and second pairs of corresponding contacts;a diode and a resistor each disposed in parallel with the transistor; anda comparator circuit that turns the transistor on when the portable device is coupled to a charger based on voltage applied by the charger across the positive and negative charging contacts and maintains the transistor turned off otherwise.