A primary driver with a fractional capacitance (FC) auto-tuning loop (ATL) for wireless-powered biomedical devices is presented. The proposed ATL maintains the resonance of the primary LC tank against varying inductance over a wide range in real time. The analog ATL has a wide loop bandwidth and achieves phase locking within six cycles. The fractional capacitor is realized with a switch-controlled capacitor. By varying the turn-on time of the switch, the effective capacitance is changed, which tunes the resonant frequency of the primary LC tank. The primary driver is a full-bridge Class-D power amplifier (PA). High-side NMOS power switches are driven by bootstrap circuits. An adaptive offset controller is proposed to compensate for the delays of comparators to enhance tuning accuracy. The chip is fabricated using a 0.18- $\mu $ m bipolar-CMOS-DMOS (BCD) process, and the active area is 0.66 mm2. The system operates at 13.56 MHz and maintains both zero-voltage switching (ZVS) and zero-current switching (ZCS) in a steady state. The maximum PA output power is 200 mW, the measured tuning range is 31.5%, and the tuning error is 1.89 ns.

中文翻译：

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适用于无线供电植入式医疗设备的具有分数电容自动调节环路的 13.56MHz 主驱动器


提出了一种用于无线供电生物医学设备的具有分数电容 (FC) 自动调谐环路 (ATL) 的主驱动器。所提出的 ATL 可实时维持初级 LC​​ 谐振回路的谐振，以应对大范围内变化的电感。模拟ATL具有较宽的环路带宽，并在6个周期内实现锁相。小数电容器是用开关控制电容器来实现的。通过改变开关的导通时间，可以改变有效电容，从而调节初级 LC​​ 谐振电路的谐振频率。主驱动器是全桥 D 类功率放大器 (PA)。高侧 NMOS 电源开关由自举电路驱动。提出了一种自适应偏移控制器来补偿比较器的延迟，以提高调谐精度。该芯片采用 0.18-$\mu$m 双极-CMOS-DMOS (BCD) 工艺制造，有源面积为 0.66 mm2。该系统工作频率为 13.56 MHz，并保持零电压开关 (ZVS) 和零电流开关 (ZCS) 处于稳定状态。 PA最大输出功率为200 mW，实测调谐范围为31.5%，调谐误差为1.89 ns。