Tool/software:
Hi,
I've studied the application note SLVAE30 and watched the videos on high-side switches and inductive loads.
My inductive load is mostly unknown but will be in the region of 1500mH with a current of around 1.2A and a supply voltage of 24V. With this in mind, any high-side switch choice I make will require an external clamping device, either a free-wheeling diode or TVS solution, because the energy stored in the inductor is in the region of 1.2J.
Looking through SLVAE30 and also a presentation I found (Driving inductive loads using power switches by Cameron Phillips) there's a general formula for the energy dissipated in a freewheeling diode, namely:
0.8 * L * (Vsup / R) * (Vf / R)
This is taken from slide 12 of the presentation.
Plugging in values for a normal diode (Vf = 1V) and my calculated resistance of 20Ohm would give 0.072J. This is far less than the energy stored in the inductor.
Can you tell me where I am going wrong? Surely energy has to be conserved?
Thanks,
Simon