An Active Charge Balancing Method Based on Chopped Anodic Phase

A new method for safe electrical neural stimulation is proposed. A negative feedback is used to automatically produce short anodic pulses according to the remaining voltage. The period of the short anodic pulses varies according to the remaining voltage. Thanks to the structure of the static comparator, the system produces pulses with high duty-cycle at the beginning of the anodic phase and low duty-cycle at the end of the anodic phase. Hence, the system can accurately balance the charge. In contrast with previous methods based on the chopped anodic phase, this method employs a new structure that reduces the area of charge balancer for integration and increases the accuracy for a safe electrical stimulation. Lowering the power consumption of the charge balancing circuit is another outcome of the proposed method. An integrated circuit implementing the proposed method is designed using a $0.18 \mu \mathrm {m}$ technology. The simulation results prove the accuracy and proper performance of the proposed method in both current and voltage mode stimulation.