High Efficiency Power Management Unit for Implantable Optical-Electrical Stimulators

A high‐efficiency power management unit (PMU) with wide dynamic range for radio frequency (RF) energy harvesting system is proposed in this paper. A digital zero current switching (ZCS) and a digital maximum power point tracking (MPPT) circuits are adopted. A sub‐threshold current reference circuit and a subthreshold voltage detection circuit are proposed to reduce the power consumption of always‐on control circuits and improve the conversion efficiency at low input power. A dual‐oscillator is designed to extend the frequency range and widen the input power range with optimized power consumption under low‐end band and high‐end band, respectively. Switch size and on‐time are adjusted according to the input power, which optimizes the conversion efficiency in a wide power range. Proposed PMU is implemented in a standard 180 nm CMOS process. The post‐layout simulation results show that proposed PMU can achieve cold‐start at the input voltage of 280 mV, the power consumption to maintain the PMU is only 9.6 nW. The input power range of the PMU is 11 nW–677 μW. When the input power is 50 nW, a power conversion efficiency (PCE) of 65% is achieved, and the peak PCE can reach 93% at 23.5 μW.

Power dissipation has become a critical design metric in microprocessor-based system design. In a multi-core system, running multiple applications, power and performance can be dynamically traded off using an integrated power management (PM) unit. This PM unit monitors the performance and power of each core and dynamically adjusts the individual voltages and frequencies in order to maximize system performance under a given power budget (usually set by the operating system). This paper presents a performance and power analysis methodology, featuring a simulation model for multi-core systems that can be easily reconfigured for different scenarios and a PM infrastructure for the exploration and analysis of PM algorithms. Two algorithms have been implemented: one for discrete and one for continuous power modes based on non-linear programming. Extensive experiments are reported, illustrating the effect of power management both at the core and the chip level.

Inductive power transfer (IPT) and capacitive power transfer (CPT) are two basic near-filed approaches for efficient wireless power transfer. Although they share similar system configurations, it is the coupler that determines power transfer characteristics and coupling efficiency. Given the same coupling space (i.e., coupler size constrains), this paper would study and compare the coupler characteristics for the inductive and capacitive coupler. The uniform induced voltage source is applied for both couplers, and the influence of the coupler size parameters and resonance frequencies are evaluated and used to optimize the coupler model parameters. The peak efficiency of the different couplers and their corresponding series-series compensated systems are used to judge the coupler performance. Finally, the design constrain is proposed to show the performance boundary of inductive and capacitive coupler.

In present days, wireless power transfer systems are more popular for its application like wireless charging devices such as cell phones, laptops, electric vehicles, underwater vehicles and medical devices. In an inductively coupled battery charging system, for better power transfer capability, a high efficiency and attaining required power level, compensation is required. This paper focused on designing and analysis of series-series (S-S) compensation topologies to minimize impedance and increase efficiency of Inductive wireless power transfer (IWPT) of electric vehicle (EV) battery charging systems. First, the designing formulas are derived for S-S compensated Inductive power transfer (IPT) system from that bifurcation issue, gain, dual side control and maximum efficiency conditions are achieved. Based on formulas, equivalent electrical circuits parameters are calculated for designing a 1.5 kW output power and the resonance frequency 85 kHz. The results convey that the maximum efficiency and zero power angle (ZPA) are achieved. A simulation system is made in the MATLAB/SIMULINK, from which performance of the system results are verified.

Contactless power transfer is expected to be applied to many applications since it is convenience and safety. Inductive power transfer (IPT) is a kind of contactless power transfer schemes uses two coils. These coils are inductively coupled and power is transferred from primary coil to secondary coil when high frequency (a few tens of kHz) AC power supplies to primary coil. In many applications using IPT, received AC power is converted to DC power and then the power is charged to battery. Thus, two functions which are rectification and regulating voltage or current are required on the receiver (secondary) side. In this study, one of two types (buck type and boost type) of DC-DC converter connected to diode rectifier were applied to IPT system, and characteristics of each type were compared by experiments. As a result of the experiments, it was found that both rectifiers have two functions which are rectification and regulating voltage or current. It was also found that boost type is better in terms of regulation capability and of efficiency of resonant circuit.

As the development of implantable biomedical devices, the rechargeable battery is applied to improve the life of implantable devices. Inductive transcutaneous power transfer, as a suitable way of charging the implantable rechargeable batteries, is widely used. During charging period, there are several stages based on the charging rule and the load resistance is varying simultaneously. In this paper, a model of inductive transcutaneous power transfer is set up with a compensative capacitor for primary coil in series and another compensative capacitor for secondary coil in parallel to descript the relationship in coupling coefficient, load resistance and conversion efficiency. Simulations were done and experiments were carried out to verify the model, and some suggestions on wireless power transfer design are given.

This paper presents a novel approach for simultaneous inductive power transfer (IPT) and communication in one system. The communication part is using the coupled pair of coils of the IPT system as transmitting medium. The proposed architecture is applicable to new and existing IPT systems with operating frequencies above 100 kHz. The challenge is to enable robust and reliable communication in the noisy environment of the power transfer. High reliability is necessary as it shall transmit sensor data error free. For example, this data link can be used for closed-loop operation of the IPT system. Through its fully digital implementation it can be quickly adapted for various other applications. It will be shown that a reliable communication system with joint power transfer and continuous data transmission over the same pair of coupling coils can be realised. Even during high power transfers it features a robust communication channel with outstanding signal to noise ratio and advantageous error vector magnitude. For proof of concept the key performance values of the proposed communication architecture are measured in a 20W IPT system.

Inductive power transfer (IPT) systems are transforming railway infrastructure by enabling efficient, wireless energy transmission for electric locomotives equipped with Li-ion batteries. This technology eliminates the need for overhead power lines and third rails, offering financial and operational advantages over conventional electric propulsion systems. Despite its potential, IPT deployment in rail applications faces significant challenges, including the fragility of materials (i.e., ferrite and Litz wires), thermal management during high-power transfers, and electromagnetic interference (EMI) on the transmitter side. This study discusses several factors affecting IPT efficiency and introduces magnetic concrete as a durable and cost-effective material solution for IPT systems. Magnetic concrete combines soft ferrite powder with water and coarse aggregates to enhance magnetic functionality while maintaining structural strength comparable to conventional concrete. Its durability and optimized magnetic properties promote consistent power transfer efficiency, making it a viable alternative to traditional ferrite cores. A comparative study has been performed on non-magnetic and magnetic concrete (with 33% ferrite powder) using both permeability tests and finite element analysis (FEA). The FEA includes both thermal and electromagnetic simulations using Ansys Maxwell (v.16), revealing that magnetic concrete can improve temperature management and EMI mitigation, and the findings underscore its potential to revolutionize IPT technology by overcoming the limitations of traditional materials and enhancing durability, cost-efficiency, and power transfer efficiency. By addressing the challenges of fragility, thermal management, and shielding of the unique coil topology design presented, this study lays the groundwork for improving IPT infrastructure in sustainable and efficient rail transport systems.

We synthesized three semicrystalline polymers (PTTBTBO, PDTBTBO, and P2FDTBTBO) by modulating the intra- and intermolecular noncovalent Coulombic interactions and investigated their photovoltaic characteristics under various light intensities. Low series (Rs) and high shunt (Rsh) resistances are essential prerequisites for good device properties under standard illumination (100 mW cm-2). Considering these factors, among three polymers, PDTBTBO polymer solar cells (PSCs) exhibited the most desirable characteristics, with peak power conversion efficiencies (PCE) of 7.52 and 9.60% by being blended with PC71BM under standard and dim light (2.5 mW cm-2), respectively. P2FDTBTBO PSCs exhibited a low PCE of 3.69% under standard light due to significant charge recombination with high Rs (9.42 Ω cm2). However, the PCE was remarkably improved by 2.3 times (8.33% PCE) under dim light, showing negligible decrease in open-circuit voltage and remarkable increase in fill factor, which is due to an exceptionally high Rsh of over 1000 kΩ cm2. Rs is less significant under dim light because the generated current is too small to cause noticeable Rs-induced voltage losses. Instead, high Rsh becomes more important to avoid leakage currents. This work provides important tips to further optimize PSCs for indoor applications with low-power electronic devices such as Internet of things sensors.

IPT (Inductive Power Transfer) is an approach based on magnetic coupling to realize a wireless power transfer (WPT) system. In applications using IPT as a mean for transferring power, like RFID, it is of great interest to have a free positioning system, meaning with fewer constraints on relative positioning and orientation between the sender and the receiver. One of the problems which face the free positioning WPT by using IPT is the great sensitivity of the system to lateral and orientational misalignment between the sender and the receiver of power. This could hugely reduce the efficiency of the whole system for certain lateral and orientational misalignments, resulting in null points for the coupling coefficient, therefore no power transfer or no detection in case of RFID. In this work, we propose a reconfigurable antenna which changes its structure by turning on and off specific parts of itself. This will guarantee the effective power transfer in the range of interest, regardless of the lateral and orientational misalignments between the sender and the receiver. The same system can be used to increase the RFID read range by steering the magnetic field in certain direction. In general, the steering of the magnetic field could be used to achieve more efficient power transfer.

This article presents a power management integrated circuit for a wireless power receiver unit. A dual-mode high-efficiency active rectifier design is based on alliance for wireless power (A4WP) and wireless power consortium (WPC) standards. A gate charge recycling technique is proposed in the dual-mode active rectifier so that the current generated by the switching of the high side gate driver can be recycled to the rectifier output voltage in order to enhance efficiency. A step-down dc–dc converter with a proposed bootstrap circuit and dynamic pull-up resistor gate driver circuit is designed. The chip is implemented in a 0.18-μm bipolar-CMOS double-diffused metal-oxide-semiconductor process. The total die area, including the pad, is 2.64 mm × 2.6 mm. The measurement results show that the active rectifier achieves peak power conversion efficiency (PCE) of 94.7% and generates an output voltage of 7.68 V in WPC mode and 9.1 V with 93.4% efficiency in A4WPC mode. The input voltage varies from 10 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P-P</sub> –12 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P-P</sub> . Similarly, the step-down dc–dc converter obtains a peak PCE of 93.2% at a load current of 500 mA while producing an output voltage of 5 V. The overall system efficiency at A4WP and WPC mode are 86.7% and 88.2%, respectively.

An inductive power transfer (IPT) system usually consists of four parts: an AC-DC power factor correction (PFC) converter, a high frequency DC-AC inverter, a compensation network comprising a loosely coupled transformer (LCT) and the resonant capacitors, and a rectification output circuit. Due to the relative large air gap, the magnetic coupling coefficient of the IPT system is poor, different from the closely-coupled IPT systems. As a result, the efficiency of the IPT system is always a main concern for different applications. To ensure high power transfer efficiency, these IPT systems should have high tolerance for different gap variation and horizontal misalignment conditions. In this paper, some design considerations to reduce gap and misalignment effects for the IPT system is proposed. By using finite element analysis (FEA) simulation method, the performance of different transmitter and receiver coil dimensions are compared. In order to validate the performance of the proposed design considerations, a hardware prototype is built and the corresponding experiments are carried out. The experimental results shows that the LCT prototype could maintain coupling coefficient between 0.237∼0.212 within 40 mm horizontal misalignment.

Several novel digital assistant power integrated technologies (DAPITs) for power management unit (PMU) to reduce the designing complexity, as well as to keep good performance in scaling CMOS process, are proposed in this paper. The DAPITs include segment power driving with pulse skip modulation/pulse width modulation and loop regulating with digital regulation circuit for dc-dcs in PMU, calibrating digital-to-analog converter (DAC) with resistance compensation network for dynamic voltage scaling (DVS), and separating phase clock for multi-dc-dcs in PMU. With these DAPITs, the efficiencies and output accuracies of dc-dcs are increased, the DVS signal sent by DAC is linear, and current ripples in PMU are reduced. In this paper, a PMU embedded into system-on-a-chip (SoC) is designed based on a 0.13-μm CMOS process. The designed PMU includes four dc-dc buck converters and two LDOs. This paper introduces the top structure of the PMU and the main proposed DAPITs. Simulation and test results show that the output voltages of the dc-dc converters in the PMU can be changed by external resistors and regulated from 0.7 to 1.8 V stepped with 25 mV by SoC load through interface. And the maximum efficiency of the dc-dcs with DVS in the PMU is more than 90%, while, with an external resistor, it can reach to 95%.

Although the demand for high-power inductive power transfer (IPT) systems is on the rise, implementation of such IPT systems using low-cost semiconductor devices has been a challenge. This study presents a new IPT topology that facilitates easy integration of multiple IPT modules, which are made of low cost and freely available semiconductor components, to cater for high-power applications. An intermediate circuit, comprising an inductor-capacitor-inductor resonant network, serves as a contactless interface through which the modules of primary and secondary (pick-up) systems can be either series or parallel integrated. Inductor coils of the intermediate circuit and both primary and pick-up systems are magnetically coupled to allow for contactless power transfer. The proposed topology is parallel compensated to minimise its var requirement, and both the direction and amount of power flow are controlled by phase and/or magnitude modulation of voltages generated by primary and pick-up side converters. Theoretical analysis, together with simulations and experimental evidence of integrating four prototype bi-directional IPT systems to cater for 1.8 kW demand, is presented to show that the proposed new IPT topology is suitable for high-power applications, and flexible for both bi-directional and uni-directional contactless power transfer.

Traditional power supply method for moving electric railway vehicles is based on contact type power collection technology. This sometimes cannot meet the requirements of modern rail transportation. A new wireless power transfer (WPT) technology can offer significant benefits in modern rail transportation particularly in some stringent environments. This paper reviews the status and the development of rail transit power supply technology, and introduces a new challenging technology--inductive power transfer (IPT) technology for rail transit. Tesla established the underpinning of IPT technology and creatively and significantly demonstrated power transfer by using highly resonant tuned coils long time ago. However, only in recent years the IPT technology has been significantly improved including the transfer air-gap length, transfer efficiency, coupling factor, power transfer capability and so on. This is mainly due to innovative semiconductor switches, higher control frequency, better coil designs and high performance material, new track and vehicle construction techniques. Recent advances in IPT for rail transit and major milestones of the developments are summarized in this paper. Some important technical issues such as coupling coil structures, power supply schemes, segmentation switching techniques for long-distance power supply, and bidirectional IPT systems for braking energy feedback are discussed.