Composite transformer and insulated switching power source device

• US 7,872,561 B2
• Filed: 06/12/2008
• Issued: 01/18/2011
• Est. Priority Date: 12/16/2005
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Matumoto, Tadahiko
• Primary Examiner(s): NGUYEN, TUYEN T
• Application Number:
  US12/137,966
• Publication Number:
  US 20080253149A1
• Time in Patent Office: 950 Days
• Field of Search: 336/65, 336/83, 336/200, 336/232, 336180-184, 336/170, 336/212
• US Class Current: 336/200
• CPC Class Codes: H01F 17/0013 with stacked layers
• CPC Class Codes: H01F 2027/065 Mounting on printed circuit boards
• CPC Class Codes: H01F 27/2804 Printed windings
• CPC Class Codes: H02M 3/33592 having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
• CPC Class Codes: H05K 1/165 incorporating printed inductors
• CPC Class Codes: 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

Abstract

An E-shaped transformer core has a middle leg and one pair of outer legs and on opposite sides with respect to the middle leg. A first pair of coils including at least two coils are wound around the middle leg so that a power transmission transformer unit is formed. The outer leg is divided into two outer leg portions and with a space therebetween allowing coil wiring therebetween, and a second pair of coils including two coils are respectively wound around the respective two outer leg portions and so as to have mutually opposite winding directions, so that a signal transmission transformer unit is formed.

Claims

1. A composite transformer comprising:

a core having a middle leg and at least one pair of outer legs on opposite sides with respect to the middle leg, the core forming a closed magnetic path;

two outer leg portions being defined by at least one of the outer legs being divided with a space therebetween allowing coil wiring therebetween;

a first pair of coils including at least two coils wound around the middle leg of the core; and

a second pair of coils including at least two coils respectively wound around said two outer leg portions such that a winding direction of a portion of each of the at least two coils that is wound around one of the two leg portions is opposite to a winding direction of a portion of each of the at least two coils that is wound around another of the two leg portions;

wherein

the first pair of coils and the second pair of coils are arranged such that magnetic interference does not substantially occur between the first pair of coils and the second pair of coils.

2. The composite transformer of claim 1, wherein both of the outer legs are divided into two respective outer leg portions with a space therebetween allowing coil wiring therebetween, and the second pair of coils are wound around both of the outer legs.

3. The composite transformer of claim 2, comprising a printed board having penetration holes through which the middle leg and the outer legs or the outer leg portions of the core are respectively inserted, wherein the coils are configured as conductor patterns formed around the penetration holes of the printed board.

4. The composite transformer of claim 3, wherein the core is constituted by two members sandwiching the printed board, and a core fixing metal member is provided, the core fixing metal member fixing the two members while permitting joint surfaces thereof to rub against each other while the two members overlie each other with the printed board therebetween.

5. The composite transformer of claim 1, comprising a printed board having penetration holes through which the middle leg and the outer legs or the outer leg portions of the core are respectively inserted, wherein the coils are configured as conductor patterns formed around the penetration holes of the printed board.

6. The composite transformer of claim 2, wherein the core is constituted by two members sandwiching the printed board, and a core fixing metal member is provided, the core fixing metal member fixing the two members while permitting joint surfaces thereof to rub against each other while the two members overlie each other with the printed board therebetween.

7. An insulated switching power supply device comprising the composite transformer of any one of claims 1 and 2,

wherein an input filter for receiving a direct current and at least one power switch are provided in a primary-side circuit, the power switch converting a direct current into an alternating current by a switching operation, and at least one synchronous rectifier and an output filter for converting an alternating current into a direct current are provided in a secondary-side circuit,

wherein the composite transformer is connected such that a transformer unit comprising the first pair of coils of the composite transformer transmits alternating power from the primary-side circuit to the secondary-side circuit and that a transformer unit comprising the second pair of coils of the composite transformer transmits a first pulse signal from the primary-side circuit to the secondary-side circuit, the first pulse signal indicating a timing immediately before a turn-on of the power switch, and

wherein a synchronous rectifier turn-off control circuit is provided in the secondary-side circuit, the synchronous rectifier turn-off control circuit detecting the first pulse signal and turning off the synchronous rectifier.

8. An insulated switching power supply device comprising the composite transformer of any one of claims 1 and 2,

wherein an input filter for receiving a direct current and at least one power switch are provided in a primary-side circuit, the power switch converting a direct current into an alternating current by a switching operation, and at least one synchronous rectifier and an output filter for converting an alternating current into a direct current are provided in a secondary-side circuit,

wherein an output detecting circuit for detecting an output voltage or an output current is provided in the secondary-side circuit,

wherein the composite transformer is connected such that a transformer unit comprising the first pair of coils of the composite transformer transmits alternating power from the primary-side circuit to the secondary-side circuit and that a transformer unit comprising the second pair of coils of the composite transformer transmits a second pulse signal from the secondary-side circuit to the primary-side circuit, the second pulse signal indicating an off-timing of the power switch, and

wherein a power switch turn-off control circuit is provided in the primary-side circuit, the power switch turn-off control circuit detecting the second pulse signal and turning off the power switch.

9. The composite transformer of claim 1, wherein the at least two coils of the second pair of coils are respectively wound around the two outer leg portions with the same number of turns.