Core structure and interleaved DC-DC converter topology

• US 20030198067A1
• Filed: 11/21/2002
• Published: 10/23/2003
• Est. Priority Date: 04/18/2002
• Status: Active Grant

• Current Assignee: Flextronics International USA Incorporated (Flex, Ltd.), MyPAQ Holdings Ltd. (Transpacific IP Group Limited)
• Original Assignee: Innovative Technology Licensing LLC
• Inventors: Sun, Jian, Chandrasekaran, Sriram, Mehrotra, Vivek, Jing, Xiukuan
• Granted Patent: US 7,046,523 B2
• Time in Patent Office: Days
• US Class Current: 363/53
• CPC Class Codes: H01F 17/04 with magnetic core
• CPC Class Codes: H01F 3/08 made from powder powder coatings on sheets H01F3/02; on strips or ribbons H01F3/04; on wires H01F3/06
• CPC Class Codes: H01F 30/06 characterised by the structure
• CPC Class Codes: H02M 7/043 using transformers or inductors only

Abstract

There is disclosed a core structure with a very low profile, high power density and lower losses. The disclosed design allows for a larger core area where the DC fluxes are added, thereby reducing the air-gap requirements in the cores derived from low saturation density materials such as ferrites. The cellular nature of the design can be effectively employed in vertically packaged power converters and modules. Also disclosed is a DC-DC converter topology which preferably employs the disclosed core. N AC drive voltages drive N current doubler rectifiers (CDRs) in accordance with the symmetric modulation scheme; each CDR provides two rectified output currents to an output node. Each AC drive voltage has a switching period T_s. The drive voltages are phase-shifted by T_s/(2*N), such that the rectified output currents of the CDRs are interleaved, thereby reducing output voltage ripple.

Claims

1. An AC-DC converter, comprising:

at least two half-bridge CDRs, each of which is driven with a respective AC drive voltage and is arranged to provide two rectified output currents to an output node, said AC drive voltages having a switching period T_s,

a filter capacitor connected between said output node and a common node, and

a load connected between said output node and said common node,

said AC drive voltages arranged such that they are phase-shifted by T_s/(2*N) such that the rectified output currents of said at least two CDRs are interleaved.

2. The AC-DC converter of claim 1, wherein each of said CDRs comprises:

first and second primary windings connected in series,

first and second secondary windings connected together at said output node, said first and second secondary windings magnetically coupled to said first and second primary windings, respectively, said first and second primary windings and first and second secondary windings wound on a common core,

a first switch circuit connected between said common node and the end of said first secondary winding opposite said output node, and

a second switch circuit connected between said common node and the end of said second secondary winding opposite said output node,

said first switch circuit arranged to conduct current only when the voltage across said second switch circuit is positive with respect to said common node and said second switch circuit arranged to conduct current only when the voltage across said first switch circuit is positive with respect to said common node,

said AC drive voltage applied across said series-connected first and second primary windings.

3. The AC-DC converter of claim 2, wherein the primary and secondary windings of each of said at least two CDRs are wound on a common core.

4. The AC-DC converter of claim 3, wherein said common core comprises:

a base having an outer edge and a top region,

a first post disposed on the top region of the base at the outer edge,

a second post disposed on the top region of the base at the outer edge,

a third post disposed on the top region of the base at the outer edge,

a fourth post disposed on the top region of the base at the outer edge,

a shared common center portion disposed on the base, and

a top disposed on the posts and opposite the base,

wherein the first post and the center portion are separated on the base to thereby define a first window, the second post and the center portion are separated on the base to thereby define a second window, the third post and the center portion are separated on the base to thereby define a third window, the fourth post and the center portion are separated on the base to thereby define a fourth window, and the top and center portions are spaced apart to thereby define an air gap.

5. The AC-DC converter of claim 4, wherein said converter comprises first and second CDRs,

the first primary winding and the first secondary winding of said first CDR wound on said first post,

the second primary winding and the second secondary winding of said first CDR wound on said second post,

the first primary winding and the first secondary winding of said second CDR wound on said third post, and

the second primary winding and the second secondary winding of said second CDR wound on said fourth post.

6. The AC-DC converter of claim 2, wherein said converter comprises first and second CDRs which are wound on first and second E-cores, respectively,

the first primary winding and the first secondary winding of said first CDR wound on one of the outer posts of said first E-core,

the second primary winding and the second secondary winding of said first CDR wound on the other of the outer posts of said first E-core,

the first primary winding and the first secondary winding of said second CDR wound on one of the outer posts of said second E-core, and

the second primary winding and the second secondary winding of said second CDR wound on the other of the outer posts of said second E-core.

7. A DC-DC converter, comprising:

a DC-AC converter which converts a DC voltage to N AC drive voltages suitable for driving N half-bridge current doubler rectifiers (CDRs) in accordance with the symmetric modulation scheme, said AC drive voltages having a switching period T_s,

an AC-DC converter comprising at least two half-bridge CDRs, each of which is driven with a respective one of said AC drive voltages and is arranged to provide two rectified output currents to an output node,

a filter capacitor connected between said output node and a common node, and

a load connected between said output node and said common node,

said DC-AC converter arranged such that said AC drive voltages are phase-shifted by T_s/(2*N) such that the rectified output currents of said at least two CDRs are interleaved.

8. The DC-DC converter of claim 7, wherein each of said CDRs comprises:

first and second primary windings connected in series,

first and second secondary windings connected together at said output node, said first and second secondary windings magnetically coupled to said first and second primary windings, respectively, said first and second primary windings and first and second secondary windings wound on a common core,

a first switch circuit connected between said common node and the end of said first secondary winding opposite said output node, and

a second switch circuit connected between said common node and the end of said second secondary winding opposite said output node,

said first switch circuit arranged to conduct current when the voltage across said second switch circuit is positive with respect to said common node and the AC drive voltage applied across said first and second primary windings is positive, and said second switch circuit arranged to conduct current when the voltage across said first switch circuit is positive with respect to said common node and the AC drive voltage applied across said first and second primary windings is negative,

said AC drive voltage applied across said series-connected first and second primary windings.

9. The DC-DC converter of claim 8, further comprising a control circuit which operates said AC-DC converter, wherein each of said first and second switch circuits are first and second field-effect transistors (FETs), respectively, and said control circuit is arranged to:

turn on said first FET and turn off said second FET when the AC drive voltage applied across said first and second primary windings is positive and the voltage across said second FET is positive with respect to said common node, and to;

turn on said second FET and turn off said first FET when the AC drive voltage applied across said first and second primary windings is negative and the voltage across said first FET is positive with respect to said common node.

10. The DC-DC converter of claim 8, wherein said first and second switch circuits are first and second diodes, respectively.

11. The DC-DC converter of claim 8, wherein the primary and secondary windings of each of said at least two CDRs are wound on a common core.

12. The DC-DC converter of claim 11, wherein said common core comprises:

a base having an outer edge and a top region, a first post disposed on the top region of the base at the outer edge,

a second post disposed on the top region of the base at the outer edge,

a third post disposed on the top region of the base at the outer edge,

a fourth post disposed on the top region of the base at the outer edge,

a shared common center portion disposed on the base, and

a top disposed on the posts and opposite the base,

wherein the first post and the center portion are separated on the base to thereby define a first window, the second post and the center portion are separated on the base to thereby define a second window, the third post and the center portion are separated on the base to thereby define a third window, the fourth post and the center portion are separated on the base to thereby define a fourth window, and the top and center portions are spaced apart to thereby define an air gap.

13. The DC-DC converter of claim 12, wherein said base has a square shape, the posts are each disposed at respective corners of said square, and said center portion has plural legs in a plus shape.

14. The DC-DC converter of claim 13, wherein said converter comprises first and second CDRs,

the first primary winding and the first secondary winding of said first CDR wound on said first post,

the second primary winding and the second secondary winding of said first CDR wound on said second post,

the first primary winding and the first secondary winding of said second CDR wound on said third post, and

the second primary winding and the second secondary winding of said second CDR wound on said fourth post.

15. The DC-DC converter of claim 8, wherein said converter comprises first and second CDRs which are wound on first and second E-cores, respectively,

the first primary winding and the first secondary winding of said first CDR wound on one of the outer posts of said first E-core,

the second primary winding and the second secondary winding of said first CDR wound on the other of the outer posts of said first E-core,

the first primary winding and the first secondary winding of said second CDR wound on one of the outer posts of said second E-core, and

the second primary winding and the second secondary winding of said second CDR wound on the other of the outer posts of said second E-core.

16. The DC-DC converter of claim 7, wherein N=2 such that first and second CDRs receive first and second AC drive voltages, respectively, and provide four interleaved rectified currents to said output node in response.

17. The DC-DC converter of claim 16, wherein said DC-AC converter comprises:

positive and negative DC input voltage terminals for receiving a DC input voltage,

first and second switches connected in series between said positive and negative DC input voltage terminals, the junction of said first and second switches being a first node,

third and fourth switches connected in series between said positive and negative DC input voltage terminals, the junction of said third and fourth switches being a second node,

first and second capacitors connected in series between said positive and negative DC input voltage terminals, the junction of said first and second capacitors being a third node,

said first AC drive voltage taken between said first and third nodes and said second AC drive voltage taken between said second and third nodes, and

a control circuit which operates said first, second, third and fourth switches to provide said first and second AC drive voltages such that they are phase-shifted by T_s/4 with respect to each other.

18. A DC-DC converter, comprising:

a DC-AC converter which converts a DC voltage to first and second AC drive voltages suitable for driving respective half-bridge current doubler rectifiers (CDRs) in accordance with the symmetric modulation scheme, said AC drive voltages having a switching period T_s, said DC-AC converter comprising;

positive and negative DC input voltage terminals for receiving a DC input voltage,

first and second switches connected in series between said positive and negative DC input voltage terminals, the junction of said first and second switches being a first node,

third and fourth switches connected in series between said positive and negative DC input voltage terminals, the junction of said third and fourth switches being a second node,

first and second capacitors connected in series between said positive and negative DC input voltage terminals, the junction of said first and second switches being a third node,

a first AC drive voltage taken between said first and third nodes and a second AC drive voltage taken between said second and third nodes, and

a control circuit which operates said first, second, third and fourth switches to provide said first and second AC drive voltages such that they are phase-shifted by T_s/4 with respect to each other,

an AC-DC converter comprising first and second half-bridge CDRs, each of which is driven with a respective one of said AC drive voltages such that said CDRs provide four interleaved rectified output currents to an output node, each of said CDRs comprising;

first and second primary windings connected in series,

first and second secondary windings connected together at said output node, said first and second secondary windings magnetically coupled to said first and second primary windings, respectively, said first and second primary windings and first and second secondary windings wound on a common core,

a first switch circuit connected between said common node and the end of said first secondary winding opposite said output node, and

a second switch circuit connected between said common node and the end of said second secondary winding opposite said output node,

said first switch circuit arranged to conduct current when the voltage across said second switch circuit is positive with respect to said common node and the AC drive voltage applied across said first and second primary windings is positive, and said second switch circuit arranged to conduct current when the voltage across said first switch circuit is positive with respect to said common node and the AC drive voltage applied across said first and second primary windings is negative,

said AC drive voltage applied across said series-connected first and second primary windings,

a filter capacitor connected between said output node and a common node, and

a load connected between said output node and said common node.

19. The DC-DC converter of claim 18, wherein each of said first and second switch circuits are first and second field-effect transistors (FETs), respectively, and said control circuit is further arranged to:

turn on said first FET and turn off said second FET when the AC drive voltage applied across said first and second primary windings is positive and the voltage across said second FET is positive with respect to said common node, and to;

turn on said second FET and turn off said first FET when the AC drive voltage applied across said first and second primary windings is negative and the voltage across said first FET is positive with respect to said common node.

20. The DC-DC converter of claim 18, wherein the primary and secondary windings of said two CDRs are wound on a common core, said common core comprising:

a base having an outer edge and a top region,

a first post disposed on the top region of the base at the outer edge,

a second post disposed on the top region of the base at the outer edge,

a third post disposed on the top region of the base at the outer edge,

a fourth post disposed on the top region of the base at the outer edge,

a shared common center portion disposed on the base, and

a top disposed on the posts and opposite the base,

wherein the first post and the center portion are separated on the base to thereby define a first window, the second post and the center portion are separated on the base to thereby define a second window, the third post and the center portion are separated on the base to thereby define a third window, the fourth post and the center portion are separated on the base to thereby define a fourth window, and the top and center portions are spaced apart to thereby define an air gap,

wherein the first primary winding and the first secondary winding of said first CDR are wound on said first post,

the second primary winding and the second secondary winding of said first CDR are wound on said second post,

the first primary winding and the first secondary winding of said second CDR are wound on said third post, and

the second primary winding and the second secondary winding of said second CDR are wound on said fourth post.

21. The DC-DC converter of claim 18, wherein said first and second CDRs are wound on first and second E-cores, respectively,

the first primary winding and the first secondary winding of said first CDR wound on one of the outer posts of said first E-core,

the second primary winding and the second secondary winding of said first CDR wound on the other of the outer posts of said first E-core,

the first primary winding and the first secondary winding of said second CDR wound on one of the outer posts of said second E-core, and

the second primary winding and the second secondary-winding of said second CDR wound on the other of the outer posts of said second E-core.