A High Frequency Active Voltage Doubler in Standard CMOS Using Offset-Controlled Comparators for Inductive Power Transmission

Abstract

In this paper, we present a fully integrated active voltage doubler in CMOS technology using offset-controlled high speed comparators for extending the range of inductive power transmission to implantable microelectronic devices (IMD) and radio-frequency identification (RFID) tags. This active voltage doubler provides considerably higher power conversion efficiency (PCE) and lower dropout voltage compared to its passive counterpart and requires lower input voltage than active rectifiers, leading to reliable and efficient operation with weakly coupled inductive links. The offset-controlled functions in the comparators compensate for turn-on and turn-off delays to not only maximize the forward charging current to the load but also minimize the back current, optimizing PCE in the high frequency (HF) band. We fabricated the active voltage doubler in a 0.5-μm 3M2P std. CMOS process, occupying 0.144 mm2 of chip area. With 1.46 V peak AC input at 13.56 MHz, the active voltage doubler provides 2.4 V DC output across a 1 kΩ load, achieving the highest PCE = 79% ever reported at this frequency. In addition, the built-in start-up circuit ensures a reliable operation at lower voltages.

Optimal Design of a Resonance-Based Voltage Boosting Rectifier for Wireless Power Transmission

“…In an integrated circuit (IC) implementation, there are two choices for implementing D 1 ; a passive Schottky diode or an active diode [18]. The conduction time of D 1 is much smaller than 1/ f p , which indicates a need for rapid on/off operation of the active diode.…”

“…Although several power management integrated circuit (PMIC) solutions have been proposed to achieve higher power conversion efficiency (PCE) [17]–[19] in the WPT, these systems cannot improve the PDL. Boost converters [20], [21], charge pumps [22], [23], and voltage-doubler rectifiers [18] have been implemented in the WPT system to boost the Rx received voltage by reducing the effective load resistance. These techniques can increase the output voltage on the Rx side at the cost of system complexity and large number of off-chip components, resulting in increased Rx size.…”

An On-Chip Multi-Voltage Power Converter With Leakage Current Prevention Using 0.18 um High-Voltage CMOS Process

“…An unbalanced-biased comparator with non-zero turning-off trigger voltage is proposed to shut off the rectifying transistors when the induced voltage is smaller than the rectifier's output voltage [9], but the turn-on delay of the rectifying transistor is not compensated, leading to power loss. High-speed and compensated biasing comparators are also reported to control rectifying switches, but extra current is consumed [24], [26]. More critically, if those circuit techniques were directly applied to the HV rectifier, more power would be dissipated due to the much higher supply voltage used by the rectifier control circuitry.…”

“…2(b) [4], [13]- [16], [23], [25], [26]. and are used as switches controlled by the voltage difference between and DC.…”

“…One previous method includes a power amplifier driving an external coil to transmit power signals to the coil in the implant. An on-chip active rectifier and a low-drop-out (LDO) voltage regulator receive the power signal and produce a stable DC voltage for the implant [9], [11]- [15], [25], [26] (Fig. 1).…”