Design and implementation of a novel Ni-Cd battery charger

A negative ΔV controller with voltage detection, fast charging, timer control, and temperature protection is proposed for the Ni-Cd battery chargers. The battery stops being charged when a negative ΔV (voltage drop) is detected. A constant-current DC-DC buck converter is employed for fast charging. When the battery is fully charged, it is in the trickling mode with small charging current to maintain the battery voltage. A sequential logic circuit is used to control the battery signal and the charging signal (indicating whether the battery is fully charged). Through the state table, it sends the proper output signals for controlling the constant-current charging circuit and the trickling circuit. The complete charging process is monitored and automatically controlled