# US 2017/0256356 A1 · Power supply circuit

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- Number: US 2017/0256356 A1
- Document ID: US20170256356A1
- Status: Published application
- Kind: A1
- Application number: 15/600,835
- Filed: 2017-05-22
- Published: 2017-09-07
- Earliest claimed: 2015-06-29
- Assignees: Murata Manufacturing Co., Ltd.
- Applicants: Murata Manufacturing Co., Ltd.
- Inventors: Hiroyuki TAKATSUJI
- Web page: https://patentgrep.com/patent/US20170256356A1

## CPC

- H01F 17/04: with magnetic core
- H01F 27/06: Mounting, supporting, or suspending transformers, reactors, or choke coils {not being of the signal type}
- H01F 27/292: {Surface mounted devices}
- H01F 27/40: Structural association with built-in electric component, e.g. fuse
- H01F 27/42: Circuits specially adapted for the purpose of modifying, or compensating for, electric characteristics of transformers, reactors, or choke coils (circuits for controlling transformers, reactors or choke coils, for the purpose of obtaining a desired output H02P13/00; impedance networks H03H)
- H02M 1/44: Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
- H02M 3/156: with automatic control of output voltage or current, e.g. switching regulators
- H03H 7/09: Filters comprising mutual inductance
- H01F 27/065: {Mounting on printed circuit boards}
- H01F 38/48: {Common mode inductor for reducing or eliminating common mode noise on parallel lines}
- Y02B 70/10: Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- 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)
- H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P)
- Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS

## Abstract

A power supply circuit includes a DC-DC converter and a choke coil. The choke coil includes a pair of coils wound in mutually opposite directions, and the coils are connected between a DC power source and the DC-DC converter. In the choke coil, a self-resonating frequency in a common mode is higher than a self-resonating frequency in a normal mode. In the choke coil, a normal mode impedance at the highest frequency in an AM band is higher than a common mode impedance at the lowest frequency in an FM band.

## Claims

### Claim 1

A power supply circuit comprising:
a DC-DC converter, including a switching element that switches a DC input voltage inputted from a DC power source, that supplies a DC output voltage according to an on-off duty ratio of the switching element to a load; and
a choke coil, including a pair of coils wound in mutually opposite directions, in which the paired coils are connected between the DC power source and the DC-DC converter,
wherein in the choke coil, a self-resonating frequency in a common mode, in which a current flows in the paired coils in the same direction, is higher than a self-resonating frequency in a normal mode, in which the current flows in the paired coils in mutually opposite directions; and
in the choke coil, a normal mode impedance at the highest frequency in a predetermined low-frequency band is higher than a common mode impedance at the lowest frequency in a high-frequency band that is higher than the low-frequency band.

### Claim 2 (depends on 1)

The power supply circuit according to claim 1,
wherein the self-resonating frequency in the common mode is present within the high-frequency band.

### Claim 3 (depends on 1)

The power supply circuit according to claim 1,
wherein the high-frequency band is an FM band and the low-frequency band is an AM band.

### Claim 4 (depends on 1)

The power supply circuit according to claim 1,
wherein the switching element of the DC-DC converter is driven at a switching frequency that is lower than the low-frequency band.