Planar transformer arrangement

• US 7,042,325 B2
• Filed: 05/30/2003
• Issued: 05/09/2006
• Est. Priority Date: 05/31/2002
• Status: Expired due to Term

• Current Assignee: Infineon Technologies Americas Corp. (Infineon Technologies AG)
• Original Assignee: International Rectifier Corporation (Infineon Technologies AG)
• Inventors: Giandalia, Marco, Passoni, Marco, Grasso, Massimo
• Primary Examiner(s): Nguyen, Tuyen T
• Application Number:
  US10/452,679
• Publication Number:
  US 20040027224A1
• Time in Patent Office: 1,075 Days
• Field of Search: 336/65, 336/83, 336199-208, 336/232
• US Class Current: 336/200
• CPC Class Codes: H01F 17/0013 with stacked layers
• CPC Class Codes: H01F 2017/0093 Common mode choke coil
• CPC Class Codes: H01F 2019/085 Transformer for galvanic isolation
• CPC Class Codes: H01F 2027/2819 Planar transformers with printed windings, e.g. surrounded by two cores and to be mounted on printed circuit
• CPC Class Codes: H01F 27/2804 Printed windings
• CPC Class Codes: H01F 27/323 Insulation between winding turns, between winding layers
• CPC Class Codes: H01F 27/345 using auxiliary conductors

Abstract

A planar transformer arrangement and method provide isolation between an input signal and an output signal. The planar transformer arrangement includes a planar medium having a first layer, a second layer, and a dielectric interlayer arranged between the first and second layers; at least one meandering primary winding arranged on the first layer of the planar medium, a current flow being induced within the primary winding in accordance with the input signal; at least one meandering secondary winding arranged on the second layer of the planar medium, the primary and secondary windings forming a planar transformer, whereby a voltage is induced across the secondary winding in accordance with the current flow within the primary winding; and a mode elimination arrangement configured to produce a compensated voltage by compensating for a common mode interference on the voltage induced across the secondary winding, the mode elimination arrangement being further configured to generate the output signal in accordance with the compensated voltage; wherein the dielectric interlayer of the planar medium provides a voltage isolation between the primary and secondary windings.

Claims

1. A planar transformer arrangement to provide isolation between an input signal and an output signal, the planar transformer arrangement comprising:

a planar dielectric medium having a first side and a second side;

a meandering primary winding arranged on the first side of the planar medium, a current flow being induced within the primary winding in accordance with the input signal;

a meandering secondary winding arranged on the second side of the planar medium,

the primary and secondary windings forming a planar transformer, wherein a voltage is induced across the secondary winding in accordance with the current flow within the primary winding; and

a mode elimination arrangement configured to produce a compensated voltage by compensating for a common mode interference on the voltage induced across the secondary winding, the mode elimination arrangement being further configured to generate the output signal in accordance with the compensated voltage; and

wherein the planar medium provides a voltage isolation between the primary and secondary windings.

2. The planar transformer arrangement according to claim 1, wherein:

the mode elimination arrangement includes a mode detect winding arranged on one of the first and second sides of the planar medium; and

the mode elimination arrangement is configured to compensate for the common mode interference in accordance with a voltage induced across the mode detect winding by an externally applied magnetic field.

3. The planar transformer arrangement according to claim 2, wherein:

the mode elimination arrangement further includes a differential amplifier; and

the differential amplifier is configured to compensate for the common mode interference in accordance with the voltage induced across the secondary winding and the voltage induced across the mode detect winding by the externally applied magnetic field.

4. The planar transformer according to claim 1, wherein:

the primary winding includes a first meandering portion and a second meandering portion;

the secondary winding includes a first meandering portion and a second meandering portion;

the first primary winding portion and the first secondary winding portion form a first planar transformer;

the second primary winding portion and the second secondary winding portion form a second planar transformer; and

a voltage is induced across one of the first and second secondary winding portions in accordance with the input signal.

5. The planar transformer according to claim 4, wherein the mode elimination arrangement includes a differential amplifier arrangement configured to compensate for a common mode interference on the voltage induced across the one of the first and second secondary winding portions.

6. The planar transformer according to claim 5, further comprising:

a first magnetic core arranged in a region of the first and second primary windings; and

a second magnetic core arranged in a region of the first and second secondary windings;

wherein the magnetic cores are configured to conduct a magnetic field generated by at least one of the first and second planar transformers.

7. The planar transformer according to claim 6, wherein at least one of the magnetic cores includes ferrite.

8. The planar transformer according to claim 5, further comprising:

a first metallic shield arranged in a region of the first and second primary windings, the first metallic shield being electrically connected to a primary ground voltage; and

a second metallic shield arranged in a region of the first and second secondary windings, the second metallic shield being electrically connected to a secondary ground voltage.

9. The planar transformer according to claim 1, wherein the planar medium is a printed circuit board.

10. The planar transformer according to claim 1, wherein the planar medium is an integrated circuit.

11. The planar transformer according to claim 10, wherein the first and second layers of the planar medium include first and second metal layers of the integrated circuit.

12. The planar transformer arrangement according to claim 1, wherein:

the mode elimination arrangement further includes a differential amplifier having a positive input electrically connected the secondary winding of the transformer, and a negative input electrically connected to the mode detect winding,

whereby the differential amplifier compensates for the common mode interference in accordance with the voltage induced across the secondary winding and the voltage induced across the mode detect winding by an externally applied magnetic field.

13. The planar transformer according to claim 1, further comprising:

a first magnetic core arranged in a region of the primary winding; and

a second magnetic core arranged in a region of the secondary winding;

wherein the magnetic cores are configured to conduct a magnetic field generated by the planar transformer.

14. The planar transformer according to claim 1, further comprising:

a first metallic shield operatively associated with the primary windings, the first metallic shield being electrically connected to a primary ground voltage; and

a second metallic shield operatively associated with the secondary windings, the second metallic shield being electrically connected to a secondary ground voltage.

15. The planar transformer according to claim 1, each of the primary and secondary windings includes respective sub-windings connected in anti-series, the sub-windings being configured to cancel a magnetic common mode interference generated by an externally applied magnetic field.

16. The planar transformer according to claim 15, wherein the at least one meandering primary winding includes a first meandering primary winding and a second meandering primary winding, and the at least one meandering secondary winding includes a first meandering secondary winding and a second meandering secondary winding, the first primary winding and the first secondary winding forming a first planar transformer, the second primary winding and the second secondary winding forming a second planar transformer, a voltage being induced across one of the first and second secondary windings in accordance with the input signal.

17. The planar transformer according to claim 16, further comprising:

a first metallic shield arranged in a region of the first and second primary windings, the first metallic shield being electrically connected to a primary ground voltage; and

a second metallic shield arranged in a region of the first and second secondary windings, the second metallic shield being electrically connected to a secondary ground voltage.

18. The planar transformer according to claim 17, further including a magnetic core associated with each of the primary and secondary windings.

19. The planar transformer according to claim 16, further comprising:

a first metallic shield arranged in a region of the first and second primary windings, the first metallic shield being electrically connected to a primary ground voltage; and

a second metallic shield arranged in a region of the first and second secondary windings, the second metallic shield being electrically connected to a secondary ground voltage.

20. The planar transformer according to claim 15, wherein the planar medium is a printed circuit board.

21. The planar transformer according to claim 15, wherein the planar medium is a integrated circuit.

22. The planar transformer according to claim 21, wherein the first and second layers of the planar medium include first and second metal layers of the integrated circuit.