power transmitting unit (A4WP) (PTU)
In wireless charging using the magnetic resonance( MR) method specified by the Alliance for Wireless Power( A4WP), the power transmitting unit (PTU) is the power sending unit.
The PTU unit generates the power signal, which it transmits to the receiving unit, the Power Receiving Unit( PRU), using the resonance principle. Both stations are tuned to the same resonant frequency between 1 MHz and 10 MHz.
The transmitting PTU station consists of an oscillator for the resonant frequency, the power amplifier with matching network and the resonant circuit for wireless power transmission. The generated frequency is amplified in the power amplifier and fed into the resonant circuit, from where it is coupled into the receiving resonant circuit of the receiving unit. Depending on the quality of the resonant coils and the distance between the two coils, more efficient or less efficient wireless power transfer occurs via magnetic flux.
In wireless charging of electric vehicles, the PTU unit is installed in the garage floor, while the PRU unit is fixed under the floor panel of the vehicle. To keep the distance between the two coils very small, the PTU unit can be raised electrically.