Electrical – Maximum current to the circuit

inductorpower supplywireless-charging

The schematic of the wireless power transmitter is shown enter image description here, The circuit works good. The inductor connected between circled nodes 1 and 1 is 24uH.

(Note: both the inputs of FET are not shorted, they are turned ON by the driver)
My input voltage and current to my circuit are 5V and 3A , maximum rated values of the adapter. (The driver is powered separately from a microcontroller board). When I observe my input power to the system, current drawn by the system is maximum 1A, when at resonance frequency. My MOSFET can allow upto 51A of current.

How can I feed more current into my system? What affects the current input to the system?
(My inductor coil is the coil used for standard wireless charging device)

Best Answer

How can I feed more current into my system?

First off, why do you want to feed more current into it? Do you really mean that you want to supply more power to the receiving device? Is the 1A current you quote with a load coupled to the inductor (I hope), or without (uh oh)?

What affects the current input to the system? (My inductor coil is the coil used for standard wireless charging device)

Not a simple question. With no coupled load, you'd hope that the supply current is minimal. How the current rises when you couple a load to it depends on the load itself and how tightly it is coupled. It looks like you have the primary side tuned to about 300kHz. Is your input on the PWM pin a 300kHz square wave? If the secondary (load) side is not tuned to the same frequency, the coupling will be poor. If everything is already tuned properly and the coupling is as tight as possible, then you may have to increase the supply voltage to the output stage if you want more power. If you keep the VDD supply at 5V, you could run the supply to the output stage up to 27V according to the TPS28225 spec.

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