Load shift keying (LSK) is commonly used in wireless power transfer (WPT) systems for backscattering information from the receiver back to the transmitter. However, when the coupling coefficient (k) between the coupling coils falls below a threshold value (kDF), the demodulated LSK data can unexpectedly flip from '1' to '0' and '0' to '1'. This phenomenon is referred to as coupling-dependent data flipping (CDDF). This research investigates the factors that lead to CDDF in series-series resonant WPT systems, by taking into account of parasitic parameters of the coupled link and validates the analysis through SPICE simulations. To mitigate CDDF, we propose a carrier-frequency auto-tuning scheme that is also verified by simulation results.

A 13.56-MHz wireless power transfer (WPT) system with fully integrated transmitter (TX) and receiver (RX) chips is presented. The receiver’s output voltage is locally regulated using a linear current-sink-based regulator, while global power regulation is achieved at the transmitter through a hybrid control strategy that combines constant off-time and hysteretic control for a reconfigurable power amplifier. Synchronized load-shift keying at the receiver improves the relative change in the primary current of the transmitter by >15%. The adaptive digitally controlled active rectifier achieves a voltage conversion ratio (VCR) and power conversion efficiency (PCE) of 0.92 and 92.4%, respectively, for a 200 Ω load resistance. The end-to-end efficiency is improved by 25% at heavy load and 14% at light load by enabling TXglobal power regulation. Both TXand RXchips were fabricated in the BCDlite 180 nm process with 1.8 V/5 V devices. This system achieves a greater operating distance, higher output power, and faster load-transient response while significantly reducing circuit and system design complexity.

This paper presents a wireless power transfer (WPT) receiver with an adaptive digitally-controlled on-off delay-compensated active rectifier for high-current biomedical implants. High efficiency is achieved by using adaptive digital techniques to compensate for turn-on and turn-off delays, reduce reverse current, and eliminate multiple pulsing. The adaptive scheme improves voltage conversion ratio (VCR) and power conversion efficiency (PCE) at different PVT corners. The generation of the optimal delay compensation current is 1.5 times faster than published works. The proposed design is implemented with 0.18 μm CMOS process. The measured maximum VCR is 0.978 for a 2 kΩ load resistance, and the maximum PCE is 92.2% for a 200 Ω load resistance.

A systematic design technique of flexible tertiary coil in a wireless power transfer (WPT) system for back telemetry detection is presented. The detection (tertiary) coil is co-planar with the primary coil and receives the backscattered load shift keying (LSK) data from the secondary stage. Tertiary coil parameters such as the number of turns, compensation capacitance, and quality factor are determined to maximize the link gain and the end-to-end (E2E) efficiency. The analysis is validated through SPICE simulations and measurements. A novel area-saving inner-tertiary coil is further proposed and critically compared with traditional outer-tertiary coil. The RF electromagnetic radiation or Specific Absorption Rate (SAR) value of the coils was evaluated for possible health hazards using 3D head models and ANSYS/HFSS finite element software. In comparison to a heuristic outer-tertiary coil design, the primary-secondary (operating) distance is improved by 50%, from 12 mm to 18 mm. At an operating distance of 15 mm, the link gain and E2E efficiency are improved by ~207% and ~18%, respectively.

A 16-bit on-chip embedded encryption system built upon eFUSE, cipher, hash functions, and EDCs for optical nerve stimulation is presented. The foundry-provided eFUSE IP is modified with a one-shot block to support wireless power transfer operation by mitigating the supply voltage drop problem during sensing to avoid subsequent resetting. Novel logic gate-based auxiliary circuit facilitates different sensing and programming modes in eFUSE. A 128-bit cipher is reduced to 16 bits with cascade structure using the proposed divide-and-conquer algorithm, keeping the cipher strength constant. The developed resource sharing technique reduces the area and the power consumption of the ciper circuits by 2.7 times and 5.1 times, respectively. The whole system with the optical nerve simulator is fabricated with 0.18$\mu$m BCDlite process, and measurement results show the correct encryption operation when powered by wirelessly transferred power.

A detection (tertiary) coil co-planar with the transmitter coil receives and decodes backscattered data from the receiver using load shift keying (LSK). Tertiary coil parameters such as the number of turns, compensation capacitance and quality factor are studied for maximizing voltage gain and end-to-end efficiency through novel analytical modelling, SPICE simulations and measurement results. A novel “inside-tertiary coil structure” is suggested to save the overall coil area, and two variations are discussed. Voltage gain and efficiency are improved by ~197% and ~15%, respectively, at a transmitter-receiver distance of15 mm. Design strategy improves the operating distance of implant by 50%, from 12 mm to 18 mm.

Class-D half-bridge power amplifiers (PA) are used to drive the primary coil of a coupled wireless power transfer (WPT) system. We analyze the primary inductor current of cases such as off-resonant operation, overtuned- and undertuned-capacitor operation, and effects due to finite rise and fall times. We also analyze the case with off-resonant Zero Voltage Switching (ZVS) tank. SPICE simulations validate all the analytical calculations with errors smaller than 2%.

Authors describe the circuital aspect of a cheap, multimodal electrochemical potentiostat based on 'off-the-shelf' components. The device can do the commonly available electro-analytical techniques like linear sweep voltammetry (LSV), chronoamperometry (CA), square wave voltammetry (SWV), and cyclic voltammetry (CV). The device has matching results with market available potentiostats. Operating range of current and voltage (±1μA-150 μA, ±1.5V) of the system are reduced than commercial potentiostats, but its functional scope closely relates with most electrochemical analyses in aqueous solutions. The authors used this multimodal device as a biochemical analyzer for simultaneous glucose, lactic acid detection from sweat. It has a compact form factor, portable, integrated with BLE and Wi-Fi feature, and useful for wearable integration.

In an industrial environment, there is always a surging demand for a wearable device to cope up with the increasing degree of automation and reduced manual intervention. The requirement of the wearable is related to the employee's health and well-being. Safety remains a prime concern despite other large-scale availability of the personal protective equipment (PPE) and the adoption of strict safety measures. The wearable can be an essential component of the worker's toolkit, as its application is increasingly demanding. We have developed an integrated cardiorespiratory & sweat monitoring wearable and performed extensive experiments in an operational underground mine in different conditions. The appearance of a wearable platform with biochemical analysis, physiological parameters monitoring along with ambient environment sensors has enabled the observation of critical indicators of performance as well as the stress of mineworkers.

This paper gives the design of IMC and IMC derived biphasic Interleaved Boost Converter (IBC) in voltage mode control technique. Small-signal based modelling of IBC in continuous conduction mode (CCM) of operation shows a right half plane zero (RHPZ) in control to output plant transfer function (TF) of the IBC. IBC produces substantially low output voltage ripple compared to boost converter due to the emergence of multiple power switches in the parallel path. Subsequently, the size and output filter losses of IBC can be substantially reduced in comparison to the Boost Converter (BC). Execution of the converter-controller system is validated by SISO tool-based step response analysis. Developed IMC and IMC dependent PID controllers are performing better than highly cited Type III controller-based IBC in line, load regulation, and reference tracking study. They have comparable performance in parametric uncertainty (variation) study, validated using MATLAB/SIMULINK. IMC derived PID is performing better than the IMC controller in line regulation, load regulation, and parametric variations, but in step response checking, they have nearly equal settling time.

A class-D power amplifier (PA) powering a pair of resonant coils is studied. Time-domain analysis of the primary and the secondary sections inductor current with series-series (SS) and series-parallel (SP) resonance are derived, with either resistor or rectifier loads. Both the ripple and rectified output voltage of the secondary section are analyzed. Results are validated through extensive SPICE simulations. Analytical and simulated results are matched with better than 90% accuracy.

This research studies the effect of a starving resistor in various pre-driver schemes for shoot-through loss reduction in the buffer of an integrated DC-DC converter and explores how the efficiency is affected. The starving resistor (Bidirectional delay element) reduces the short circuit current of an inverter by developing time skewed gate driving signals for the driven stage NMOS and PMOS inside a buffer. The starving resistor scheme enhances the efficiency if it is inside the buffer of a switch, but is not as efficient if it is inside the buffer of an active diode. The efficiency of the buffer can be further enhanced by adding delay generator schemes within a buffer. Results are validated via extensive SPICE simulations.