Magnetically saturable components and circuits
Embodiments described herein are directed to inrush current limiters having a transformer. In one embodiment, an inrush current limiter includes a transformer including a primary winding, a secondary winding and a saturable magnetic core shared therebetween, a resistor connected in parallel with the secondary winding, wherein an impedance of the resistor is reflected across the transformer when a voltage is applied across the primary winding and the saturable magnetic core is not saturated, and a diode connected between the primary winding and ground.
1. An inrush current limiter, comprising:
a transformer comprising a primary winding, a secondary winding and a saturable magnetic core shared therebetween;
a resistor connected in parallel with the secondary winding, wherein an impedance of the resistor is reflected across the transformer when a voltage is applied across the primary winding and the saturable magnetic core is not saturated; and
a diode connected between the primary winding and ground such that magnetizing current of the saturable magnetic core flows through the diode as a reset path to reset the saturable magnetic core to remanence.
2. The inrush current limiter of claim 1 , wherein the transformer provides a magnetic timer such that after an expiration of the magnetic timer:
the saturable magnetic core is saturated, and
the primary winding and the secondary winding are decoupled, causing the primary winding to become a short such that the impedance of the resistor is not reflected across the transformer.
3. The inrush current limiter of claim 2 , wherein a number of turns of the primary winding affects a duration of the magnetic timer.
4. The inrush current limiter of claim 2 , wherein a saturation limit of the saturable magnetic core increases a duration of the magnetic timer.
5. A radiation hardened (rad-hard) circuit comprising the inrush current limiter of claim 2 .
6. The inrush current limiter of claim 2 , wherein the diode is configured to reset the saturable magnetic core.
7. The inrush current limiter of claim 2 , wherein the expiration of the magnetic timer comprises reaching a voltage-time product of the transformer.
8. A circuit comprising:
the inrush current limiter of claim 1 , connected in series between a power source and a load, wherein the power source is connected to the diode, the diode is connected to a first end of the primary and the load is connected to a second end of the primary.
9. The circuit of claim 8 , wherein
the power source comprises a direct current (DC) voltage source, and
the load comprises a capacitor.
10. The circuit of claim 8 , further comprising a Flyback converter power supply.
11. The circuit of claim 8 , further comprising a capacitor and a second resistor, the second resistor connected between the capacitor and ground.
12. A radiation hardened circuit, comprising:
a transformer;
a diode connected between a first end of the transformer and ground, wherein magnetizing current of the transformer flows through the diode as a reset path to reset the saturable magnetic core to remanence;
a power source connected between the diode and ground; and
a load connected between a second end of the transformer and ground,
wherein:
an impedance is reflected across the transformer, and
the reflected impedance limits an inrush current.
13. The radiation hardened circuit of claim 12 ,
wherein the transformer comprises a primary winding and a secondary winding,
wherein the transformer provides a magnetic timer, and
wherein upon expiration of the magnetic timer:
the transformer is in a saturated state, and
the primary and the secondary are decoupled, causing the impedance to not be reflected across the transformer and causing the primary winding to become a short.
14. The radiation hardened circuit of claim 13 , wherein the diode resets the transformer to an un-saturated state.
15. The radiation hardened circuit of claim 14 , wherein the diode comprises a free-wheeling diode.
16. The radiation hardened circuit of claim 13 , wherein a number of turns of the primary affects a duration of the magnetic timer.
17. The radiation hardened circuit of claim 13 , further comprising a resistor connected in parallel with the secondary winding.
18. The radiation hardened circuit of claim 13 , wherein the expiration of the magnetic timer comprises reaching a specific voltage-time product of the transformer.
19. The radiation hardened circuit of claim 12 , wherein the load is a Flyback converter power supply.
20. An inrush current limiter, comprising:
an inductor comprising a saturable magnetic core;
a resistor connected in parallel with the inductor, wherein a current through the resistor when a voltage is applied across the inductor and the saturable magnetic core is saturated is less than a current through the resistor when the voltage is applied across the inductor and the saturable magnetic core is not saturated; and
a diode connected between the inductor and ground such that magnetizing current of the saturable magnetic core flows through the diode as a reset path to reset the saturable magnetic core to remanence.