Wireless power transfer (WPT) based on inductive coupling offers convenient charging for applications such as medical implantable microsystems, portable electronic devices, and electric vehicles. This research focuses on integrated circuit design and testing of wireless power transmitters (TXs) and receivers (RXs) for compact WPT systems with improved performance.

First, a discontinuous-conduction mode (DCM) zero-voltage switching (ZVS) half-bridge class-D power amplifier (PA) for a WPT TX is proposed. The sizes of the ZVS inductor and capacitor are reduced by 7.5× and 5×, respectively, and ZVS is achieved even subject to variations in PA supply voltage and output current. A ZVS loop and a zero-current detection (ZCD) loop are introduced to compensate for process-voltage-temperature (P...[ Read more ]

Wireless power transfer (WPT) based on inductive coupling offers convenient charging for applications such as medical implantable microsystems, portable electronic devices, and electric vehicles. This research focuses on integrated circuit design and testing of wireless power transmitters (TXs) and receivers (RXs) for compact WPT systems with improved performance.

First, a discontinuous-conduction mode (DCM) zero-voltage switching (ZVS) half-bridge class-D power amplifier (PA) for a WPT TX is proposed. The sizes of the ZVS inductor and capacitor are reduced by 7.5× and 5×, respectively, and ZVS is achieved even subject to variations in PA supply voltage and output current. A ZVS loop and a zero-current detection (ZCD) loop are introduced to compensate for process-voltage-temperature (PVT) variations.

Second, a 6.78-MHz single-stage WPT TX using a novel reconfigurable regulating class-D PA is proposed. Based on a 3-mode modulation scheme, the TX achieves power regulation and transmission with only one power stage. By employing the above DCM ZVS scheme, PA switching loss is reduced. The output voltage of the RX is regulated using a digital control loop to control the power of the TX. With dual-loop control using a proportional-integral (PI) compensator, the WPT system achieves tight output regulation and a fast loop response.

Third, a 13.56-MHz WPT RX for implantable medical devices (IMDs) is proposed. It adopts a novel one-stage 0X/1X reconfigurable resonant regulating (R³) rectifier. Based on a synchronized pulse width modulation (PWM) control scheme, the rectifier achieves voltage regulation simultaneously by using only 4 power transistors and 2 gate-driving buffers.

Finally, a lossless on-chip current sensing and estimation scheme for a novel 6.78-MHz single-stage constant-current constant-voltage (CC-CV) wireless charger is proposed, and no lossy sensing resistor is needed. A fully differential adaptive delay-compensation technique is used to improve sensing accuracy by eliminating the reverse current. A constant charging current can be set for the CC loop, which shares the same PWM controller with the CV loop to achieve a smooth transition. Measurements results show the charging current was well regulated at 1 A in the CC mode.