Infineon Unwraps Wireless Power Transmitter IC for up to 50 W Charging
Released in time for PCIM Europe this week, the new chip's integrated approach is aimed at enabling easier and more-cost-efficient wireless charging designs.
In recent years, a technology that has found its way into mainstream electronics is wireless charging. As more designs look to eliminate the cumbersome and clumsy reliance on wires, wireless charging is now a part of popular devices from smartphones to headphones.
From a design perspective, however, wireless charging is not a simple function to achieve. To help make the design of wireless charging systems easier for the engineer, last week Infineon Technologies announced the WLC1150, its new wireless charging transmitter IC. The deivce has will be showcased this week by Infineon at PCIM Europe 2023, running this week from May 9 to 11 in Nuremberg, Germany.
The WLC1150 transmitter features include flexible thermal management options, low EMI, integrated adaptive foreign object detection (FOD), and more. Image used courtesy of Infineon
In this article, we’ll look at the theory behind inductive charging, some of the circuitry to support it, and the new WLC1150 from Infineon.
Inductive Charging Theory
When people talk about wireless charging, most often they are referring to inductive charging. Inductive charging is a method of wireless power transmission that works on the principles of electromagnetic induction as described by Maxwell’s equations. Essentially, inductive charging exploits two laws of electromagnetism:
An alternating current passing through a wire will produce an alternating magnetic field—in other words, an alternating magnetic flux through a coil.
An alternating magnetic flux—an alternating magnetic field through a coil—will produce an induced EMF.
Inductive charging principle. Image from Rohm Semiconductor
Hence, the idea behind inductive charging is to have a system with two coils, one for a transmitter and one for a receiver. The two coils are placed on top of one another and the transmitting coil is driven by an alternating current, which in turn produces an alternating magnetic field emanating from the transmitting coil.
That alternating magnetic field in turn creates an alternating magnetic flux in the receiving coil, which induces an alternating current in the receiver. In this way, electrical power is transmitted between two devices entirely wirelessly.
From the transmitter end, there are a number of ways to actually create the alternating current required in hardware. One standard approach is to use a full-bridge inverter driven by phase-shifted PWM.
Full bridge inverter schematic. Image from NXP
In this scheme, an alternating current output is produced from a DC input through the use of four MOSFETs in a full-bridge topology. One output is taken from the middle node between Q1 and Q3, and the other is taken between Q2 and Q4, as shown in the image above.
Phase shifted PWM for inverter control. Image from NXP
The gates of each of these FETs are then driven by selectively timed alternating and phase-shifted PWM signals, as shown in the image above. Specifically, the gate-drive signals of Q1 and Q3 are complements of each other and are shifted in phase from the gate-drive signals of Q2 and Q4, which are also complements of each other. The output of this circuit is an AC wave which is then used to drive the transmission coil for inductive charging.
New Infineon IC Addresses Design Challenges
Naturally, designing and controlling the circuitry to support wireless charging transmission is not an easy feat. To help simplify the design, Infineon’s new IC, called the WLC1150, is a highly integrated wireless transmitting controller IC that supports wireless charging applications up to 50W. The device is meant to simplify the design of wireless charging systems by interfacing with PWM logic control circuitry and offering integrated gate drivers for driving an output full-bridge inverter and TX coil.
WLC1150 application block diagram. Image from Infineon. (Click image to enlarge)
The system offers an intelligent solution by being based on a 32-bit Arm Cortex-M0 processor that is supported by 128 KB flash, 16 KB RAM, and 32 KB ROM. The device also has dedicated hardware blocks for improved functionality, such as an ADC, PWMs, and timers.
Additionally, the WLC1150 has a number of “nice-to-have” features, such as a supporting system powered by a USB Type-C PD scheme, integrated buck converters for cooling fan peripherals, and even integrated foreign object detection (FOD) functionality. More information is available on Infineon's Wireless Charging ICs page.
A Smoother Path for Wireless Charger Design
Altogether, Infineon believes that by offering programmable and highly integrated wireless transmitting ICs, they will help enable more performant and less complex wireless charging designs for the future of consumer electronics.
Infineon is showcasing the WLC1150 this week at PCIM Europe 2023 at its booth #412 in hall 7. More information is available on Infineon's PCIM Europe page.