An Efficiency-Enhanced CMOS Rectifier With Unbalanced-Biased Comparators for Transcutaneous-Powered High-Current Implants

Abstract

This paper presents an efficiency-enhanced integrated full-wave CMOS rectifier for the transcutaneous power transmission in high-current biomedical implants. The comparator-controlled switches are developed to minimize the voltage drop along the conducting path while achieving the unidirectional current flow. The proposed unbalanced-biasing scheme also minimizes the reverse leakage current of the rectifier under different input amplitudes, thereby optimizing the rectifier power efficiency. Moreover, the proposed rectifier is able to self start and operates at low input amplitudes. Implemented in a standard 0.35 m CMOS process with maximum threshold voltages of thp = 0 82 V and thn = 0 69 V, the rectifier can source a maximum output current of 20 mA and operate properly with inputs of different amplitudes and frequencies. With a 1.5 MHz input of 1.2 V amplitude, the proposed rectifier can achieve the peak voltage conversion ratio of 95% and the power efficiency of at least 82%.

Efficiency Evaluation of a MOSFET bridge rectifier for Powering LEDs using Piezo-electric Energy Harvesting Systems

“…A. C. Asis, S. E. Rajan ity of extracting more power from the transducer. MOS-FET Bridge AC to DC converter is one which replaces the passive diodes in the conventional AC to DC converter [8] with an operational amplifier-controlled counterpart and a switch is added across the transducer. The proposed MOSFET Bridge AC to DC converter reduces the conduction drop, so that the maximum power is extracted from the transducer [9].This leads to better conversion capability and power extraction.…”

A unified DLL-controlled active rectifier in 6.78 MHz resonant-coupling wireless power receivers for space-limited portable and wearable applications

“…1, the higher the AC-DC rectifier efficiency ( rectifier ) is, the higher the overall receiver efficiency ( receiver ) that can be achieved [4,5]. The power loss reduction including current consumption by rectifier control circuits is required to enhance the rectifier power efficiency ( rectifier ), which is generally given as a ratio between input power and output power (P IN ;rect =P OUT ;rect ¼ ðV IN Á I IN Þ=ðV RECT Á I RECT Þ), while employing the small rechargeable battery.…”

“…To address this problem, the state-of-the-art resonant WPT receivers employ the active synchronous rectifier that replaced the diodes with the MOS transistors [4,5,6,7]. However, because of the bidirectional characteristic of the MOS transistor, it is crucial to ensure accurate switching without the reverse leakage current.…”

“…However, because of the bidirectional characteristic of the MOS transistor, it is crucial to ensure accurate switching without the reverse leakage current. In [5], the unbalanced-biased comparator with a non-zero finite DC offset is adapted to compensate the turn-off delay and minimize the reverse leakage current. Since the compensated delay is constant with the variable amplitude of the input AC voltage, if the input voltage is sufficiently low, reverse leakage current may occur.…”

“…To solve the problem of the input AC voltage dependency, dynamic compensation with DLLs has been proposed [6,7]. Compared with the PMOS cross-coupled and NMOS controlled active rectifiers [5,6], a fully NMOS transistor-based active rectifier [7] has higher voltage and current efficiency due to the low resistance of NMOS transistors. In addition, the fully NMOS integration of the rectifier still has an advantage in the hardware cost of the die area, which reduces the cost.…”