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Replacing the batteries of wearable medical devices is an inconvenience to the user. Wireless power transfer (WPT) could be a solution for this problem. However, the structure should be compact to satisfy the wearable device requirements and the power efficiency should be as high as possible for prolonging the user experience. Besides, as algorithms embedded in these devices become more complex, the device power consumption also increases. Fulfilling these specifications in a compact structure with better efficiency is the aim of this research paper. This paper proposes a power processing module for WPT applications. This module is embedded within the WPT path to convert receiving end ac power to dc power, and to simultaneously provide multiple dc–dc power conversion for wearable medical devices. The ac–dc circuit is specifically designed using a compact topology to convert wireless ac power to stable dc power. The dc power is further regulated by different mode controls either to perform battery charging or to provide independent voltage supplies to dc loads. The integrated circuit occupies an area of 1.9 × 2.3 mm when implemented on a 0.25 μm high voltage CMOS process.

A digitally controlled low-dropout voltage regulator (LDO) that can perform fast-transient and autotuned voltage is introduced in this paper. Because there are still several arguments regarding the digital implementation on the LDOs, pros and cons of the digital control are first discussed in this paper to illustrate its opportunity in the LDO applications. Following that, the architecture and configuration of the digital scheme are demonstrated. The working principles and design flows of the functional algorithms are also illustrated and then verified by the simulation before the circuit implementation. The proposed LDO was implemented by the 0.18-μm manufacturing process for the performance test. Experimental results show that the LDO's output voltage Vout can accurately perform the dynamic voltage scaling function at various Vout levels (1/2, 5/9, 2/3, and 5/6 of the input voltage VDD) from a wide VDD range (from 1.8 to 0.9 V). The transient time is within 2 μs and the voltage spikes are within 50 mV when a 1-μF output capacitor is used. Test of the autotuning algorithm shows that the proposed LDO is able to work at its optimal performance under various uncertain conditions.

Conventional wearable medical devices need batteries to sustain reliable power for the circuits. Battery replacement is usually inconvenient to the user experience. Wireless power transfer (WPT) could be the solution for this problem. However, wearable medical devices have their intrinsic specifications that could be challenges to the WPT. Their structures should be concise for the wearable needs. Power efficiency should be made as high as possible for prolonging the user experience. Besides, more computing based algorithms embedded in these devices would require more power consumption. How to fulfill these specifications is the aim of this research work. This paper proposes a wireless power processing module that integrate AC-DC and multi- DC-DC power circuits together for wearable medical devices. The AC-DC circuit is specifically designed using a concise topology to enhance power conversion efficiency. The DC power is further regulated by different mode controls to facilitate battery charging or to provide multiple voltage outputs. The integrated circuit is implemented by a 0.25 µm high voltage CMOS process with 1.9 µm × 2.3 µm circuit dimensions.

A single-stage buck-type AC-DC converter is proposed for medical implants to achieve high efficiency. The proposed structure combines two traditional stages of the three-stage power path for medical implants and eliminates a MOSFET and a filter capacitor to improve the efficiency. The proposed circuit converts 40 Vpp coil voltage into a DC output voltage of 4.2 V. The stability analysis of the circuit is also presented. Load currents between 1 mA to 100 mA are supported. The efficiency of the proposed circuit is 81.9%.