Core assemblies for magnetic saturation detector without requirement for bias current
Magnetic core assemblies include a skewing feature that introduces transverse components into the power flux density vector are disclosed herein. A magnetic core assembly comprises a lower core having a center section and an upper core having a center section. The center sections are aligned to form a center post. A power winding that receives current is wrapped around the center post. The core assembly further comprises a power flux density vector that has transverse and non-transverse components. The transverse components have a higher magnetic reluctance than the non-transverse components. When the assembly is used with a transverse winding, the transverse components from the magnetic core assembly produce a transverse voltage waveform on the transverse winding. The transverse voltage waveform may be observed to detect a change in the sign of the slope of the transverse voltage waveform. The change in the sign of the slope indicates magnetic saturation.
1 . A magnetic saturation detector comprising:
a magnetic core assembly comprising:
a core assembly comprising,
a lower core piece having a center section, and
an upper core piece having a center section, the center section of the upper core piece aligned to the center section of the lower core piece such that a center post of the core assembly is formed; and
a power winding, wrapped around the center post, wherein when a current is passed through the power winding a power flux density vector is generated, wherein the power flux density vector has a transverse component and a non-transverse component, and wherein the transverse component has a higher magnetic reluctance than the non-transverse component;
a transverse winding, perpendicular to the power winding, wherein transverse components from the magnetic core assembly produce a transverse voltage waveform on the transverse winding; and
a voltage detection circuit, configured to receive the transverse voltage waveform and to detect a change in the sign of the slope of the transverse voltage waveform, wherein the change in the sign of the slope indicates magnetic saturation.
2 . The magnetic core assembly as in claim 1 wherein the lower core piece comprises a lower core member; and the upper core piece comprises an upper core member.
3 . The magnetic core assembly as in claim 2 , wherein each core member has a reference mark, the reference marks are rotationally offset within the core assembly, and the rotational offset introduces the transverse component to the power flux density vector.
4 . The magnetic core assembly as in claim 2 , wherein the lower and upper core members each includes a skewing feature and a reference mark.
5 . The magnetic core assembly as in claim 4 , wherein for each core member, the skewing feature is positioned at the core member perimeter and the reference marks are aligned within the core assembly.
6 . The magnetic core assembly as in claim 1 , wherein at least one of the lower and upper core members has a skewing feature, and the skewing feature introduces the transverse component to the power flux density vector.
7 . The magnetic core assembly as in claim 6 , wherein the skewing feature is a truncated corner.
8 . The magnetic core assembly as in claim 6 , wherein the center post includes the skewing feature.
9 . The magnetic core assembly as in claim 8 , wherein the skewing feature comprises a helix.
10 . The magnetic core assembly as in claim 8 , wherein the skewing feature comprises grooves on the surface of the center post.
11 . The magnetic saturation detector as in claim 1 , wherein the center post has an aperture and the transverse winding is positioned within the aperture.
12 . The magnetic saturation detector as in claim 11 ,
wherein each of the lower core member and the upper core member each comprises a core member having a reference mark,
wherein the reference marks are rotationally offset within the core assembly, and
wherein the rotational offset introduces transverse components to the power flux density vector.
13 . The magnetic saturation detector as in claim 11 , wherein
the lower core member and the upper core member, each comprises a core member having a skewing feature and a reference mark, wherein the reference marks are aligned within the core assembly, and the skewing feature introduces transverse components to the power flux density vector.
14 . The magnetic saturation detector as in claim 13 , wherein the skewing feature is positioned at the center post and is selected from a group consisting of helixes and surface grooves.
15 . The magnetic saturation detector as in claim 13 , wherein for each core member, the skewing feature is positioned at the perimeter of the core member.
16 . The magnetic saturation detector as in claim 15 , wherein the skewing feature is a truncated corner.
17 . A power supply that includes the magnetic saturation detector, as in claim 11 , comprising:
an output-referenced controller, coupled to the magnetic core assembly and configured to sense an output sense signal, compare the output sense signal to a reference value, and generate a switching signal; and
an input-referenced controller, coupled to the magnetic core assembly and configured to produce a drive signal.