A 3-Phase Resonant Current-Mode Wireless Power Receiver with Residual-Free Energy Delivery and Digital-Assisted ZVS Achieving 94.5% Efficiency

Wireless power transfer (WPT) is a non-invasive method for powering bioimplants, where the inductive link is typically loosely coupled (coupling factor <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k < < 1</tex> ). <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">In</tex> such applications, conventional voltage-mode (VM) receivers (RX) hardly maintain reliable power receiving due to their high rectifier threshold [1], [2]. Resonant currentmode (RCM) RXs overcome this limitation by accumulating energy in the LC resonator before rectification [1]–[4]. Figure 1 (top) shows two typical structures of RCM RX: parallel-LC and series-LC. <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">In</tex> the parallel-LC structure, RX accumulates received energy in the LC tank for periods <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(Φ₁)</tex> and then charges the output capacitor since <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IL</tex> peaks, with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CRX</tex> disconnected <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(Φ₂)</tex> . Though it delivers energy without residual in the LC tank, it witnesses a high voltage stress ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">VAC+</tex> V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DC</inf> ) on the charging switch in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Φ₁</tex> , limiting the energy accumulation. The series-LC structure reduces the voltage stress on switches to V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DC</inf> ; however, residual energy remains in C <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RX</inf> after <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Φ₂</tex> , causing high conduction losses. [3] erases the residual energy by entering <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Φ₂</tex> before IL peaks ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IL</tex> -rising charging). Unfortunately, it fails in high-power cases [4]. On the other hand, voltage regulation or battery charging protection is crucial for RXs. To achieve regulation, both parallel-LC and series-LC need to enter <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Φ₁</tex> to save output power; however, this introduces voltage-breakdown risks in the parallel-LC structure and high conduction losses in the series-LC structure. This work proposes a 3-phase RCM RX, simultaneously achieving low switch voltage stress, residual-free energy delivery, and efficient output regulation. Together with a new digital-assisted zero-voltage switching (ZVS) control, the proposed RX achieves a wide operational range (0 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2mA≤</tex> load <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">≤ 64mA;0.03≤ k≤ 0.45)</tex> and a high power conversion efficiency (PCE, peak at 94.5 % ).