Patent ID: 8288999

Claim:
A charging circuit, capable of simultaneously charging and balancing serially connected batteries, comprising: a battery pack including a plurality of serially connected batteries, wherein the serially connected batteries are connected to an output end and an input end of a power supply so that a constant charge current source is supplied by the power supply to the battery pack; a plurality of changeover switches, each of the plurality of changeover switches is serially connected to and between two adjacent ones of the serially connected batteries, wherein the plurality of changeover switches are connected to at least one of a positive electrode and a negative electrode of the serially connected batteries without a particular limit; and a plurality of precision voltage detectors, each of the plurality of precision voltage detectors is parallelly connected to one of the serially connected batteries for independently detecting a voltage of the serially connected battery parallelly connected thereto and sending out a detected result to a charging control circuit; wherein the charging control circuit being independently connected to the plurality of changeover switches for controlling the plurality of changeover switches to ON or OFF based on the detected results sent from a plurality of corresponding precision voltage detectors; wherein when the serially connected batteries are charged, the plurality of changeover switches are independently controlled by the charging control circuit connected thereto to ON so that the constant charge current source from the power supply is supplied to the serially connected batteries to charge the serially connected batteries; wherein when any of the serially connected batteries is detected by at least one of the plurality of precision voltage detectors parallelly connected thereto as having been fully charged, a message is sent by at least one of the plurality of precision voltage detector to inform the corresponding charging control circuit of a fully charged battery, causing the charging control circuit to control the corresponding changeover switch to OFF so that the charge current source to the fully charged battery is supplied to a following battery via a by-pass circuit parallelly connected to the fully charged battery, and the fully charged battery is not further charged; wherein a remaining battery that is subsequently fully charged is disconnected from the power supply one by one until a voltage different between the output end and the input end of the power supply is reached to a pre-determined valve to indicate that the charging process is completed.