Hi,
I'm doing a project to design a contactless battery charger. For an underwater vehicle.
So far, I've got two coils - primary powered by a 12V H-bridge circuit, secondary connected to full bridge rectifier and smoothing capacitor.
The secondary circuit needs to supply a maximum of 1A at 8.4V to charge the battery. To make this possible, I've had to make the primary coil 20 turns and the secondary 150 turns, with a series resonant circuit on the secondary.
This setup works fine for the maximum load, but as the battery charges, the current will drop, and with this transformer, when the current drops, the voltage increases quite steeply, to more than 30 or 40V.
Is there any way I can regulate the output voltage to under 12V in the no-load condition? My thoughts were that I could have a circuit that changes the resonance capacitor, or shorts it, when the voltage gets too high, but I can't work out how to do it.
Does anyone have any ideas?
I'm doing a project to design a contactless battery charger. For an underwater vehicle.
So far, I've got two coils - primary powered by a 12V H-bridge circuit, secondary connected to full bridge rectifier and smoothing capacitor.
The secondary circuit needs to supply a maximum of 1A at 8.4V to charge the battery. To make this possible, I've had to make the primary coil 20 turns and the secondary 150 turns, with a series resonant circuit on the secondary.
This setup works fine for the maximum load, but as the battery charges, the current will drop, and with this transformer, when the current drops, the voltage increases quite steeply, to more than 30 or 40V.
Is there any way I can regulate the output voltage to under 12V in the no-load condition? My thoughts were that I could have a circuit that changes the resonance capacitor, or shorts it, when the voltage gets too high, but I can't work out how to do it.
Does anyone have any ideas?