# US 2022/0037876 A1 · Magnetically saturable components and circuits

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- Number: US 2022/0037876 A1
- Document ID: US20220037876A1
- Status: Published application
- Kind: A1
- Application number: 16/940,638
- Filed: 2020-07-28
- Published: 2022-02-03
- Earliest claimed: 2020-07-28
- Assignees: L3 Cincinnati Electronics Corporation
- Applicants: L3 Cincinnati Electronics Corporation
- Inventors: Justin Graves
- Web page: https://patentgrep.com/patent/US20220037876A1

## CPC

- H02H 9/001: {limiting speed of change of electric quantities, e.g. soft switching on or off (progressive control of electronic switches for eliminating interferences H03K17/16)}
- H02H 9/02: responsive to excess current {(current limitation for voltage regulators G05F1/573; disconnection after limiting H02H3/025)}
- H02M 1/32: Means for protecting converters other than automatic disconnection
- H02M 3/156: with automatic control of output voltage or current, e.g. switching regulators
- H02M 3/33507: {with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence)}
- H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H)
- H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P)

## Abstract

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.

## Claims

### Claim 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 the diode provides a reset path for magnetizing current of the saturable magnetic core.

### Claim 2 (depends on 1)

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.

### Claim 3 (depends on 2)

The inrush current limiter of claim 2, wherein a number of turns of the primary winding affects a duration of the magnetic timer.

### Claim 4 (depends on 2)

The inrush current limiter of claim 2, wherein a saturation limit of the saturable magnetic core increases a duration of the magnetic timer.

### Claim 5 (depends on 2)

A radiation hardened (rad-hard) circuit comprising the inrush current limiter of claim 2.

### Claim 6 (depends on 2)

The inrush current limiter of claim 2, wherein the diode is configured to reset the saturable magnetic core.

### Claim 7 (depends on 2)

The inrush current limiter of claim 2, wherein the expiration of the magnetic timer comprises reaching a voltage-time product of the transformer.

### Claim 8 (depends on 1)

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.

### Claim 9 (depends on 8)

The circuit of claim 8, wherein
the power source comprises a direct current (DC) voltage source, and
the load comprises a capacitor.

### Claim 10 (depends on 8)

The circuit of claim 8, further comprising a Flyback converter power supply.

### Claim 11 (depends on 8)

The circuit of claim 8, further comprising a capacitor and a second resistor, the second resistor connected between the capacitor and ground.

### Claim 12

A radiation hardened circuit, comprising:
a transformer;
a diode connected between a first end of the transformer and ground, wherein the diode provides a reset path for magnetizing current of the transformer;
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.

### Claim 13 (depends on 12)

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.

### Claim 14 (depends on 13)

The radiation hardened circuit of claim 13, wherein the diode resets the transformer to an un-saturated state.

### Claim 15 (depends on 14)

The radiation hardened circuit of claim 14, wherein the diode comprises a free-wheeling diode.

### Claim 16 (depends on 13)

The radiation hardened circuit of claim 13, wherein a number of turns of the primary affects a duration of the magnetic timer.

### Claim 17 (depends on 13)

The radiation hardened circuit of claim 13, further comprising a resistor connected in parallel with the secondary winding.

### Claim 18 (depends on 13)

The radiation hardened circuit of claim 13, wherein the expiration of the magnetic timer comprises reaching a specific voltage-time product of the transformer.

### Claim 19 (depends on 12)

The radiation hardened circuit of claim 12, wherein the load is a Flyback converter power supply.

### Claim 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 the diode provides a reset path for magnetizing current of the saturable magnetic core.