What do e-bikes and laptops have in common? Both can be wirelessly charged by induction.

E-bikes and laptops both use lithium-ion batteries for power, chosen for their light weight, high energy density, and long lifespan. Both systems can be wirelessly recharged via the wireless power transfer (WPT) method that uses electromagnetic induction to transfer energy to the battery without cables.

For e-bikes, there is a wireless charging pad or inductive tile that e-bikes park on to transfer power. For induction charging, one coil is integrated into the static pad or tile (transmitter coil) and the other (the receiver coil) is situated on the bike, often in the kickstand. The charging pad’s coil, fed by AC, creates a magnetic field, which in turn produces current in the bike’s coil. This AC is then converted to DC, to power the bike’s battery.

The principle is the same for laptops, as well as a broad range of consumer and industrial devices, including small robots, drones, power tools, robotic vacuum cleaners, wireless routers, and lawnmowers.

Microchip provides a 300-W electromagnetic inductive wireless electric power transmission reference design that can be incorporated into any type of low-power consumer or industrial system for wireless charging (see block diagram in Figure 1). It consists of a Microchip WP300TX01 power transmitter (PTx) and Microchip WP300RX01 power receiver (PRx). The design operates with efficiency of over 90% at 300-W power and a Z-distance (the distance between pairing coils) of 5−10 mm.

The transmitter (Figure 2) is nominally powered from a 24-V rail and the receiver regulates the output voltage to nominal 24 V.

The design’s operating DC input voltage range is 11 V to 37 V, with input overvoltage and undervoltage protection, as well as overcurrent and thermal protection via a PCB/coil temperature-monitoring functionality. Maximum receiver output current is 8.5 A, and the receiver output voltage is adjustable from 12 V to 36 V.

The design implements a Microchip proprietary protocol, developed after years of research and development and, with patents granted in the U.S., ensuring reliable power transfer with high efficiency. The system also implements foreign object detection (FOD), a safety measure that avoids hazardous situations should a metallic object find its way in the vicinity of the charging field. Once the FOD detects a metallic object near the charging zone, where the magnetic field is generated, it stops the power transfer.

The reference design incorporates this functionality on the main coil, ceasing power from the transmitter until the object is removed. FOD is performed by stopping four PWM drive signals, with four being the maximum to avoid stopping the charging entirely.

This reference design also detects some NFC/RFID cards and tags.

Transmitter and receiver

The WP300TX01 is a fixed-function device designed for wireless power transfer, as is the WP300RX01 chip, designed for receiving wireless power. The two are paired together for a maximum power transfer of 300 W.

The user can configure the input’s under- and overvoltage, as well as the input’s overcurrent and overpower. There are three outputs for general-purpose LEDs and multiple OLED screens, as well as five inputs for interface switches. The design enables OLED display pages to allow viewing and monitoring of live system parameters, and as with the input parameters, the OLED panel’s settings can be configured by the user.

The WP300RX01 device operates from 4.8 V to 5.2 V, in an ambient temperature between −40°C and 85°C. Like with the transmitter controller, this device provides overvoltage, undervoltage, overcurrent, overpower, and overtemperature protection, with added qualification of AEC-Q100 REVG Grade 3 (−40°C to 85°C), which refers to a device’s ability to function reliably within this ambient temperature range.

The reference design simplifies and accelerates WPT system design and eliminates the need to go through the certification process, as it has already been accredited with the CE certification, which signifies that a product meets all the necessary requirements of applicable EU directives and regulations.

Types of wireless charging

There are different types of wireless charging, including resonant, inductive, electric field coupling, and RF. Inductive charging for smartphones and other lower-power electronic devices is guided by the Qi open standard, introduced by the Wireless Power Consortium in 2010, to create a universal, interoperable charging concept for electronic devices.

The Qi open standard promotes interoperability, thus avoiding multiple chargers and cables, as well as market fragmentation into different proprietary solutions. Many manufacturers have adopted this standard in their products, including tech giants like Apple and Samsung.

Since 2023, the Qi 2.0 version brings faster charging to mobile devices to 15 W, certified for interoperability and safety. Qi 2.0 devices feature magnetic attachment technology, which aligns devices and chargers perfectly for improved energy efficiency for faster and safer charging and ease of use. Qi 2.X includes the Magnetic Power Profile (MPP) with an added operating frequency of 360 kHz. With MPP, a magnetic ring ensures the receiver’s coil aligns perfectly with the charger’s coil, thus improving power transfer and reducing heat.

Qi 2.2, released in June 2025, enables 25-W charging, building on the convenience and energy efficiency of Qi while improving the wireless charging time.

Simultaneous charging of two 15-W Qi receivers

In addition to its 300-W electromagnetic inductive wireless electric power transmission reference design reviewed earlier in this article, Microchip also offers the Qi2 dual-pad wireless power transmitter reference design. This dual-pad, multi-coil wireless power transmitter reference design enables simultaneous charging of two 15-W Qi receivers (see Figure 3).

At the heart of the design is a Microchip dsPIC33 digital-signal controller (DSC) that simultaneously controls both charging pads. The dual-pad design is compatible with the Qi 1.3 and Qi 2.x standards, as well as MPP and Extended Power Profile.

The hardware is reconfigurable and supports most transmitter topologies. In addition to MPP, it supports Baseline Power Profile for receivers to 5 W.

The MPP charging pad initiates charge with a 12-kHz inverter switching frequency but will shift to 360 kHz when connected to an MPP PRx. The dsPIC33CK DSC executes two charger instances. To facilitate support for different protocols, real-time decisions based on charging pad and receiver type are required.

The MPP charging pad initiates charge with a 12-kHz inverter switching frequency but will shift to 360 kHz when connected to an MPP PRx. The dsPIC33CK DSC executes two charger instances. To facilitate support for different protocols, real-time decisions based on charging pad and receiver type are required.

The software-based design provides a high level of flexibility to optimize key features of the wireless power system, such as efficiency, charging area, Z-distance, and FOD. To support applications with a wide input voltage range, each PTx includes a front-end four-switch buck-boost (4SWBB) converter for power regulation. The 4SWBB connects to a full-bridge inverter for driving the resonant tank. On the MPP charger, additional resonant capacitor switch networks enable higher resonant frequency. An MP-A13 charger implements a similar coil select circuitry for energizing the coil with the strongest signal possible, enabling a wider area of placement.

This reference design is automotive-grade and includes CryptoAuthentication, hardware-based (on-chip) secure storage for cryptographic keys, to protect communication and data handling. In addition, the design includes a Trust Anchor TA100/TA010 secure storage subsystem. The dsPIC33CK device architecture also allows the integration of additional software stacks, such as automotive CAN stack or NFC stacks for tag detection.

It’s worth noting that the variable-input voltage, fixed-frequency power control topology implemented in the transmitter is ideal for systems that must meet stringent electromagnetic-interference and electromagnetic-compatibility requirements.

In addition to all these features, including FOD through calibrated power loss, the dual-charging reference design also provides measured quality factor/resonant frequency and ping open-air object detection; multiple fast-charge implementations, including for Apple and Samsung; and several receiver modulation types, such as AC capacitive and AC/DC resistive. For added safety, the design includes thermal power foldback and shutdown and overpower protection.

A UART-USB communication interface enables reporting and debugging of data packets, and LEDs indicate system status and coil selection. There is a reset switch and temp sensor inputs for added functionalities.

With the continuously evolving standards for Qi and unique new applications requiring higher-wattage wireless charging, there is plenty of opportunity for innovation and growth in the wireless charging space. Microchip experts can provide you with the right guidance for seamlessly bringing your wireless charging solution to market.

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