Wireless charging receiver delivers 400mA across a 1.2cm air gap

October 08, 2013 // By Graham Prophet
Linear Technology's LTC4120 marks the company's entry to the wireless battery charging space. The LTC4120 combines a wireless power receiver with a constant-current/constant-voltage battery charger, functioning as the receive circuit component in a complete wireless power transfer system comprised of transmit circuitry, transmit coil, receive coil and receive circuitry.

The LTC4120 works with Linear Technology’s simple discrete resonant transmitter reference design or with advanced off-the-shelf transmitters designed and manufactured by PowerbyProxi, a New Zealand-based wireless power solutions company. PowerbyProxi transmitters offer advanced features, including simultaneous charging of multiple receivers with a single transmitter and foreign object detection to prevent excessive heating during transmit faults.

The LTC4120 accepts a rectified 4.2V to 40V input from the receive coil to power a constant-current/constant-voltage 400mA battery charger that includes programmable charge current, a programmable 3.5V to 11V battery float voltage with ±1% accuracy, battery preconditioning with half-hour timeout, bad battery fault detection, NTC thermal protection,

charge status and a 2-hour safety termination timer.

The LTC4120 features dynamic harmonisation control (DHC), a patented technique that enables optimal wireless power transfer across a variety of conditions while providing thermal management and overvoltage protection. This technique modulates the resonant frequency of the receiver tank to provide lossless adjustment of the power received as well as the power transmitted to enable an efficient and robust solution for wirelessly charging battery-powered devices.

Wireless charging with the LTC4120 enables battery powered devices to be recharged without expensive, failure-prone connectors. Products incorporating the LTC4120 may be contained within sealed enclosures, in moving or rotating equipment or used where cleanliness or sanitation is critical. Applications include handheld instruments, industrial/military sensors and similar devices in harsh environments, portable medical devices, physically small devices and electrically isolated devices. LTC4120-based systems offer solutions that, Linear claims, are much simpler than those implementing the Qi standard, with additional benefits, including greater transmission distance and no software required.

“The LTC4120 is the first result of an ongoing partnership between Linear Technology and PowerbyProxi, a technology company focused on providing real world wireless power solutions to the market.” according to Don Paulus, VP/GM of Linear Technology’s Power Products Group. Fady Mishriki, Executive Vice President & CTO of PowerbyProxi added, “Linear’s LTC4120 and our supporting transmitters will