You might have often wondered the reason behind using ferrite cores in all modern switch mode power supplies or SMPS converters. NI (maximum) = 0.80 x H x le = 62.Why Ferrite Core is used in High Frequency Converters Maximum allowable H = 25 Oersted (from the graph above) Beyond this level, inductance drops rapidly.Įxample: How many ampere-turns can be supported by an 0R42213A315 pot core without a reduction in inductance value? They show the maximum allowable DC bias, in ampere-turns, without a reduction in inductance. The above curves represent the locus of points up to which effective permeability remains constant. Make sure the wire size chosen will support the current and fit into the core set. For the following AL values the number of turns required is:Ī L = 400, N = 16 A L = 300, N = 19 A L = 250, N = 20 Some choices based upon an LI² value of 6.4 millijoules are:

There are many ferrite cores available that will support the energy required.Īny core size that the LI² coordinate intersects can be used at the A L value shown on the chart.ħ. Example: If I MAX = 8 Amps L, inductance required = 100 μHenries

Required inductance L, core size, and core nominal inductance (A L) are known.ĥ. Any core size line that intersects the LI² coordinate represents a workable core for the inductor if the core’s A L value is less than the maximum value obtained on the chart.Ĥ. This represents the smallest core size and maximum A L at which saturation will be avoided.ģ. Read the maximum nominal inductance, A L, on the Y-axis.

Locate the LI² value on the Ferrite Core Selector chart below.įollow this coordinate in the intersection with the first core size curve. I = maximum DC output current + 1/2 AC RippleĢ. L = inductance required with DC bias (millihenries) Only two parameters of the design applications must be known:

One can determine the smallest core size, assuming a winding factor of 50% and wire current carrying capacity of 500 circular mils per ampere. These core selection procedures simplify the design of inductors for switching regulator applications. By adding air gaps to these ferrite shapes, the cores can be used efficiently while avoiding saturation. For switching regulators, power materials are recommended because of their temperature and DC bias characteristics. For other inquiries regarding inductor design with Magnetics ferrite cores, Contact our Applications Engineers or submit a Custom Inductor Design request.įerrite E cores and pot cores offer the advantages of decreased cost and low core losses at high frequencies. The following design guide may also be downloaded as a PDF. Inductor Design with Magnetics Ferrite Cores

Ferrite coil calculator