| 摘要: | 隨著醫學科學與超大型積體電路的快速發展，應用在植入人體內的醫用電子設備也不斷演進，發展至今已可被應用於調節生理功能、刺激神經、肌肉及治療多種疾病。 本論文的設計為一個應用於植入式視覺輔具的電刺激器。電刺激器必須透過電極作為介面才能對神經或肌肉進行電刺激的動作。然而電極－組織介面阻抗可能會因接觸不良、電極大小與材質的差異，又或者電極本體受刺激電流、環境等因素而產生變化，其變異範圍在10–100KΩ。當介面阻抗值過大時，刺激電流會受到供應電壓的限制，無法在刺激週期內達成有效的電刺激。 為了讓電刺激器能滿足阻抗變異的需求，根據阻抗變異與電刺激參數的設定，論文中提出了一個可產生三倍供應電壓輸出的高電壓輸出級驅動電路作為電壓控制電刺激器的想法，並以台積電0.18μm 互補式金氧半導體的標準製程實現。其好處是不需花費其他昂貴的特殊製程，又可以與其他電路整合於同一晶片。 在進行電刺激之前，使用阻抗量測電路測量介面阻抗，而數位脈波寬度調變電路可針對不同介面阻抗與刺激電荷量的需求，產生出適當的脈波寬度，使得高電壓輸出級驅動電路能有效的調整刺激電荷量，進而使得植入式電刺激器達到最佳的功效。With the rapid development of medical science and very large scale integration circuit, medical electronic devices which are used to implant in the human body have been evolved. Furthermore, some medical electronic devices have already been applied for regulating human’s physiological functions, stimulating nerves, muscles, and treatment of many diseases. This thesis aims to design an electrical stimulator for implanted visual prosthesis. The designed electrical stimulator stimulates nerves or muscles using electrodes as the interface. In general, the electrode-tissue interface impedance may changes in the rage of 10–100 KΩ due to poor contact, the electrode size and material differences, or electrode-self by stimulus current and environmental factors, and so on. Using impedance measurement circuit to measure interface impedance before stimulated, and this thesis proposes the digital pulse width modulator to produce proper pulse widths for different interface impedances, enabling electrical stimulator to adjust the stimulus charge, thus making electrical stimulator to achieve the best effect. However, the stimulus current is limited by the supply voltage, effective stimulating may be unable to be achieved in a stimulus period when the interface impedance is too large. In order for electrical stimulator to satisfy the requirement of impedance variation, this thesis also proposes a high voltage output driver, which can generate three times supply voltage output, for the voltage-controlled electrical stimulator. Moreover, such a high voltage output driver accommodating to impedance variation and stimulus parameter setting is implemented in TSMC 0.18μm standard CMOS technology to demonstrate the feasibility of the proposed electrical stimulator. An advantage of the designed high voltage output driver is that it can be fully integrated within other circuit without extra process costs. |
