Compact 5-V Qi wireless charger offers design freedom
Using the NXP solution, fewer than 10 external components are needed to build a complete low-power 5V Qi A5/A11 wireless charging transmitter, alongside the Qi coil and resonant capacitors. The small footprint of the NXP NXQ1TXA5 system-on-chip means that the whole transmitter sits on a PCB of less than 1.5 cm-square with components on a single side. The tiny footprint opens up the potential of designing innovative wireless charging pads that can fit the transmitter within the center of the Qi coil.
NXP is also demonstrating two ‘smart’ wireless charging reference designs for 12 V and 19 V Qi transmitters, featuring NFC (Near Field Communication) technology. By adding NFC, wireless chargers can offer a wide range of additional functionality. Consumers can configure wireless charging pad settings via any NFC-enabled phone or tablet, and NFC could be used to trigger ‘wake up’ of the wireless charger, thus enabling zero standby current when not in use. Other smart features include automatic Bluetooth pairing, or launching applications and web sites when an NFC-enabled phone is put on the charging pad.
“Our new wireless charging solution for 5V Qi transmitters enables our key customers to build very small Qi transmitters – bringing system costs down dramatically and offering a high degree of freedom in portable wireless charger design. By significantly reducing the size and cost of Qi transmitters, we’re opening the exciting possibility for mobile phone manufacturers to deliver wireless charging pads as a standard feature,” explained Rick Dumont, marketing director, wireless charging solutions, NXP Semiconductors. “The next generation of Qi wireless charging pads with NFC will enable users to stream music to their Bluetooth speakers and deliver useful content to their mobile devices as they are charging – all while economizing on overall power consumption.”
The NXQ1TXA5 system-on-chip integrates a power controller, digital signal processing (DSP), voltage regulation, Foreign Object Detection (FOD), a full-bridge power stage to drive the transmitter coil, and circuits for on-chip current and voltage measurement – leaving few external components to complete the solution. Using the NXP CoolFlux DSP technology, the device is power efficient and achieves standby power of less than 2 mW.
The reference design for the NXQ1TXA5 forms a complete wireless charger designed to meet low-power Qi A5/A11 specifications for 5 V chargers and can be powered by standard USB wall chargers or PC USB ports. NXP’s high-efficiency GreenChip TEA1720 SMPS controller complements this low-power reference design to achieve overall low-power standby operation.
The two other reference designs in the NXP wireless charger transmitter devices family include the NXQ1TXA6, designed to meet the Qi A6 standard for 12 V, as well as the NXQ1TXA1 which is designed to meet Qi A1/A10 standard for 19 V charging transmitters. Both the NXQ1TXA1 and NXQ1TXA6 come in a small package of 7-mm square with only 32 pins spaced 0.5-mm apart for easy PCB design. NXP provides a complete low component count reference design based on NXQ1TXA1 and NXQ1TXA6, with other high-performing components of its portfolio such as the GreenChip NWP2081 half-bridge driver, and NX2020N2 low RDS(on) trench MOSFETs for the coil-driving power bridge.
Availability
NXP’s reference designs for its wireless charger transmitter devices will be made available in Q2 for selected customers, and the parts will be qualified for mass production in Q3.
Related articles and links:
Smart wireless charging with NFC – NXP at Mobile World Congress 2014:
www.nxp.com/applications/power-management/Wireless-charging-solutions/
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