5V Qi wireless charger for A11 Qi coils
Created: Feb 15, 2016
The design is a WPC1.1.2 (Wireless Power Consortium) Qi compliant device for A11 Qi coils. The circuit operates from a 5V USB supply. The NXQ1TXA5 is a controller/driver IC for a 5V Qi-certified low power wireless charger
The technologies today are rapidly advancing, the day that charging your smartphones wirelessly is here. The convenience of charging your phone without plugging a cable into it is one of the advantages of wireless charging technology. The difference between wired and wirelessly charging may be minimal but the comfort, speed, usability of it can matter in situations. The Wireless charging technology works on the principles of electromagnetic induction. The coil in the charging plate or base creates a magnetic field as current passes through. The field created will induce an electromotive force (EMF) that produces electrical current in an adjacent coil of wire without actually touching it.
The design is a WPC1.1.2 (Wireless Power Consortium) Qi compliant device for A11 Qi coils. The circuit operates from a 5V USB supply. The NXQ1TXA5 is a controller/driver IC for a 5V Qi-certified low power wireless charger. The circuit has LED and buzzer for status indicator, so that the user will have visual and audial feedback regarding the operation and status of the application. A 5V USB input power interface options are given. Circuit A for the 5V USB power is only a buffer while circuit B has an additional common mode choke (L3). The choke contributes to the maximizing EMI (ElectroMagnetic Interference) reduction. The blue LED shows that it is powered or not. To prevent oscillations or overtones, the length of the crystal connections must be approximately 1cm and do not connect the crystal to the NXQ1TXA5 using vias. Connect it directly on the top layer of the PCB. If possible, shield the crystal by connecting the casing to ground.
The NXQ1TXA5 requires only a Qi coil, resonant capacitor, and very few external component to build a complete 5V Qi Version 1.1 compliant low power wireless charging transmitter, with a standby power of less than 10mW, for a design that fits on a single side of a PCB area of less than 2cm2. This is applicable for portable devices like wearable devices, smartwatches, remote controls, toys, and smartphones.