Energy-management Integrated Circuit Design for Wireless Power and Data Transfer Applications

This book explores wireless power and data transfer (WPDT) systems, covering applications from nanowatt RFID to kilowatt electric vehicles, with a focus on efficiency and robustness. It reviews inductive and far-field coupling, coupling coefficients, multi-coil configurations, and key circuit components like power amplifiers and rectifiers. Wireless energy management ICs are discussed, including passive/active rectifiers, resonant regulating rectifiers, adaptive converters, and resonant-mode receivers. Data telemetry methods—downlink, uplink, and bidirectional—are examined alongside modulation schemes, design trade-offs, and integration with power delivery. System-level strategies include secure energy backup for authentication tags, energy reuse in medical implants, and adaptive power systems for deep brain stimulation, emphasizing efficiency, reliability, and application-specific optimization.

This chapter provides an understanding of the fundamental principles and circuit modeling of WPT technology. WPT can be classified into near-field techniques utilizing electromagnetic induction and far-field techniques using electromagnetic radiation. Most current wireless charging technologies are based on inductive coupling. This chapter elaborates on the magnetic flux phenomenon in 2-coil inductive links and defines key parameters such as the coupling coefficient (k) and mutual inductance (M). It also covers the equivalent circuit model and efficient design considerations for 2-coil inductive links to optimize PTE and power delivered to load (PDL). Specifically, it emphasizes that the choice between series and parallel configurations for the Rx LC-tank depends on the Rx’s qulity (Q)-factor and the required voltage-current characteristics at the load. Furthermore, multi-coil systems like 3-coil and 4-coil inductive links are introduced, explaining how they can enhance WPT system efficiency and flexibility through improved impedance transformation and higher Q-factors, even under weak coupling conditions. Subsequently, the chapter analyzes the basic principles, design considerations, and common types of DC-AC converters (power amplifiers) essential for generating high-frequency AC current in the Tx coil in WPT systems. Finally, it discusses the role of AC-DC converters (rectifiers) in converting AC signals from the Rx LC-tank into DC power for the load, along with their various configurations.

This chapter delves into a comprehensive range of rectification architectures and adaptive energy reception techniques, offering insight into both fundamental and state-of-the-art solutions. First, this chapter begins with passive rectifiers, introducing conventional diode-bridge and cross-coupled topologies, and progresses toward enhanced efficiency through threshold voltage-reduction and active diode implementations. Building upon this, we explore active rectifiers that leverage high-speed comparators and offset-controlled feedback for precision switching, significantly improving power conversion efficiency (PCE) at high operating frequencies. The concept of active voltage doublers and multipliers further extends voltage conversion capabilities while addressing startup and timing challenges. To support modern system-on-chip (SoC) applications, we present single- and multi-output resonant regulating rectifiers (R³), including dual- and three-output designs that efficiently manage power distribution across varying voltage domains. Adaptive rectifier structures, including reconfigurable and optimal-tracking converters, are also covered, demonstrating real-time adjustment to dynamic load and link conditions. Finally, this chapter introduces resonant-mode energy receivers, including time-interleaved and non-residual designs, which enable efficient long-range power delivery by capturing and transferring maximum energy without losses. Together, this chapter provides a foundation and roadmap for designing next-generation AC-DC converters and energy receivers in WPT systems, emphasizing efficiency, adaptability, and integration.

This chapter focuses on efficient energy management and reliable data telemetry techniques in inductive link-based WPDT systems. Compared to far-field data communication, near-field data telemetry offers lower power consumption and simpler circuit designs, making it suitable for compact wireless applications. This chapter categorizes and explains data telemetry systems based on downlink, uplink, and bidirectional transmission methods. It introduces various modulation techniques such as single-carrier, multi-carrier, pulse-based, and harmonic-based, discussing the characteristics of each. Optimized WPDT systems require a balance of multiple factors, including data transmission rate, communication distance, robustness against link variations, and energy efficiency. Achieving reliable data telemetry in applications with power and size constraints is a significant challenge. To address this, recent WPDT systems focus on integrating a power supply with bidirectional data telemetry through inductive links. These systems efficiently combine power and data transfer to minimize additional components and power consumption while supporting simultaneous downlink and uplink data streams in various wireless applications. Therefore, designers must carefully select the most appropriate data telemetry system, considering the practical limitations of the application and available resources such as power consumption, physical area, data rate, reliability, and communication distance.

As WPT technologies developed, especially for use in biomedical and implantable devices, system-level energy management became a critical aspect of ensuring secure, efficient, and reliable operation. This chapter introduces advanced techniques that extend beyond basic power conversion, focusing on how energy is intelligently managed, reused, and adapted in real-world applications. First, this chapter presents a secure energy backup receiver designed for cryptographic wireless authentication tags. These tags play a vital role in protecting against counterfeiting in supply chains. A novel energy backup unit (EBU), equipped with non-volatile flip-flops and a clock-controlled voltage doubler, ensures secure data retention even during intentional power disruptions like power-glitch attacks. Next, the optimal reuse energy receiver addresses inefficiencies in conventional wireless back telemetry used in medical implants. Instead of dissipating energy during data transmission, the proposed system temporarily stores the telemetry energy and reuses it for device operation. An adaptive dual-input low-dropout (LDO) regulator intelligently selects between direct and stored energy sources, improving energy efficiency during telemetry and enabling simultaneous power reception and data transmission. Lastly, application-specific WPT solutions are explored through an adaptive power system for deep brain stimulation (DBS). Traditional fixed-voltage designs are replaced with a closed-loop adaptive rectifier, which adjusts its output in real time based on the requirements of stimulation sites. A voltage readout channel enables precise feedback, ensuring that only the necessary power is delivered, thereby improving safety and energy efficiency. Together, these system-level strategies mark a significant step forward in the practical deployment of wireless power for secure, efficient, and intelligent device operation.

Chapter 2 establishes the fundamental principles and circuit modeling of wireless power transfer (WPT) systems, particularly those utilizing inductive links. It details magnetic flux phenomena, key parameters like coupling coefficient (k) and mutual inductance (M), and presents equivalent circuit models for 2-coil links, optimizing power transfer efficiency (PTE) and power delivered to load (PDL). The chapter highlights that Rx LC-tank configurations (series/parallel) depend on Q-factor and desired voltage-current characteristics. Furthermore, it introduces multi-coil systems (3-coil, 4-coil) for enhanced efficiency and flexibility in weak coupling conditions. The chapter also analyzes essential DC-AC (power amplifiers) and AC-DC converters (rectifiers), their principles, design considerations, and various configurations. This comprehensive content provides the foundational understanding necessary for WPT system design.