電荷補償裝置、電荷補償方法以及包括電荷補償裝置的電刺激產生系統

專利類型

發明

專利國別 (專利申請國家)

中華民國

專利申請案號

109124695

專利證號

I 731756

專利獲證名稱

電荷補償裝置、電荷補償方法以及包括電荷補償裝置的電刺激產生系統

專利所屬機關 (申請機關)

國立臺灣科技大學

獲證日期

2021/06/21

技術說明

本專利所提出之使用AB類主動式電荷補償電路架構，包含一AB類放大器構成負回授系統，放大器之輸出端連接至生物組織；一動態比較器用以構成安全刺激窗口(± 100mV)，比較器之輸出結果將做為電荷補償結束點之指標。在功能性電刺激結束後，此電荷補償機制將被啟動，藉由AB類放大器構成之負回授系統使刺激結束後之組織電壓與輸入之位準電壓(Vref = 1.65V)進行比較並給予電流補償，而補償之電流將隨組織電壓與位準電壓之差值有所變化。 此專利之電荷補償機制採用AB類放大器之原因為此類放大器具備高迴轉率(slew-rate)之優點。當放大器之負迴授形成，AB類放大器電路具備之hype-sine電路特性可在輸出電壓與位準電壓具有較大差值時以較大之電流進行補償，然而在差值變小時，補償電流亦隨之縮小。而此特性非常適用於在功能性電刺激使用情況中會遭遇之殘餘電荷議題。在功能性電刺激結束後，殘留於組織上之電荷數量多，將使組織之電壓與位準電壓差值較大，容易造成較嚴重之組織損傷，而此時本專利所使用之AB類放大器相較於傳統之A類或B類放大器，可提供高補償電流，將組織之電荷快速消除，使其電壓快速回復至接近位準電壓之值，達到高效率之電荷補償；另一方面，在組織電壓與位準電壓差值較小時，補償電流亦隨之變小。一方面可避免在使用定電流進行電荷補償時可能遭遇之解析度問題，另一方面，可變之補償電流亦具備低靜態電流之優點，對於降低功耗具有優勢。 The circuit architecture of the charge compensator is composed of a class-AB OTA which formed a negative feedback makes the output voltage follow the reference voltage (Vref) 1.65V , a dynamic comparator that set a safety window to determine if the compensated voltage is within the defined ±100 mV and the passive recharge to create a long-term charge balancing. The class-AB OTA circuit is an OTA with current mirror based on flipped voltage followers (FVFs). The reason of using class-AB structure is the feature of high slew rate. When the negative feedback is formed, the class-AB structure can provide large current to compensate the output voltage when the voltage difference between the output voltage and the reference voltage is large, however, when the voltage difference is small, the supplied current from the OTA becomes small either. The simulation result of the class-AB OTA is from the value of current subtraction, it can be seen that class-AB OTA has the characteristics of hyper-sine. When the input voltage difference is small, the current difference is small, and when the input voltage difference becomes larger, the current will increase rapidly. This is a feature that highly suitable for the charge compensation mechanism in FES. When the charge accumulation is severe, it means that the voltage on the tissue (the output voltage of the class-AB OTA) is significantly different from the given reference voltage. At this time, the class-AB circuit will provide a large current to quickly compensate and when the tissue voltage is close to the standard voltage, the compensation current will become smaller. The self-adapting compensation current can solve the speed and over-compensation problems that would be encountered when compensating with a fixed current source. Besides, variable compensation current also leads to better compensation efficiency.

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