Integrated magnetic converter circuit and method with improved filtering

• US 6,549,436 B1
• Filed: 02/21/2002
• Issued: 04/15/2003
• Est. Priority Date: 02/21/2002
• Status: Expired due to Term

• Current Assignee: Flextronics International USA Incorporated (Flex, Ltd.)
• Original Assignee: Innovative Technology Licensing LLC
• Inventors: Sun, Jian
• Primary Examiner(s): Vu, Bao Q.
• Application Number:
  US10/080,142
• Time in Patent Office: 418 Days
• Field of Search: 363/39, 363/44, 363/48, 363/60, 363/61, 363/68, 363/69, 363/126
• US Class Current: 363/44
• CPC Class Codes: H02M 1/0064 Magnetic structures combining different functions, e.g. storage, filtering or transformation
• CPC Class Codes: H02M 3/33571 Half-bridge at primary side of an isolation transformer

Abstract

A converter and rectifier circuit comprises a magnetic core, a first secondary winding, a second secondary winding, a third secondary winding, a first rectifier, a second rectifier and an output capacitor. The first, second and third secondary windings are wound around the magnetic core and are connected to each other. The first rectifier is connected to the first secondary winding and the second rectifier is connected to the second secondary winding. The output capacitor is connected to the first and second rectifiers and is connected in series with the third secondary winding.

Claims

1. A rectifier circuit comprising:

(A) a magnetic core;

(B) a first secondary winding, the first secondary winding being wound around the magnetic core;

(C) a second secondary winding, the second secondary winding being wound around the magnetic core;

(D) a third secondary winding, the third secondary winding being wound around the magnetic core and being connected to the first and second secondary windings;

(E) a first rectifier, the first rectifier being connected to the first secondary winding;

(F) a second rectifier, the second rectifier being connected to the second secondary winding;

(G) an output capacitor, the output capacitor being connected to the first and second rectifiers and being connected in series with the third secondary winding.

2. A circuit according to claim 1,

wherein the transformer comprises a center leg and first and second outer legs which are disposed on opposite sides of the center leg,

wherein the first secondary winding is wound on the first outer leg, the second secondary winding is wound on the second outer leg, and the third secondary winding is wound on the center leg.

3. A circuit according to claim 2, further comprising a primary winding, the primary winding further comprising

(1) a first primary subwinding, the first primary subwinding being wound around the first outer leg of the magnetic core, and

(2) a second primary subwinding, the second primary subwinding being wound around the second outer leg of the magnetic core, the second primary subwinding being connected in series with the first primary subwinding.

4. A circuit according to claim 1,

wherein the transformer is mounted on a multi-layer circuit board, with the first and second outer legs and the center leg of the transformer extending through holes formed in the circuit board;

wherein the first secondary winding, the second secondary winding, and the third secondary winding are at least partially formed by traces on the circuit board.

5. A circuit according to claim 1,

wherein the transformer comprises a center leg and first and second outer leg which are disposed on opposite sides of the center leg,

wherein the first secondary winding is wound on the first outer leg, the second secondary winding is wound on the second outer leg, and the third secondary winding is wound on the first and second outer legs.

6. A circuit according to claim 1, wherein the output capacitor produces a DC output voltage that is less than about ten volts and produces a DC output current that is more than about ten amps.

7. A circuit according to claim 1, wherein the output capacitor produces a DC output voltage that is less than about five volts and produces a DC output current that is more than about thirty amps.

8. A circuit according to claim 1, wherein the first and second secondary windings have less than five turns.

9. A circuit according to claim 1, wherein the first and second secondary windings have a single turn.

10. A circuit according to claim 1, wherein the first secondary winding, the second secondary winding, and the third secondary winding cooperate to give the circuit an effective filtering inductance having the form $L=\frac{{(N_s+2}^{}}{}$

Nc)22

ℜ

c+ℜ

o,

where N_s is the number of turns of the first secondary winding an the second secondary winding, N_c is the number of turns of the third secondary winding, _c

is a reluctance of the center leg of the magnetic core, and _c

is a reluctance of the first and second outer legs of the magnetic core.

11. A dc/dc conversion method comprising:

providing a voltage to a primary winding of a transformer, the voltage causing a first current to flow in a first secondary winding, a second current to flow in a second secondary winding, and a third current to flow in a third secondary winding, the third current being a summation of the first and second currents;

rectifying the first current using a first rectifier;

rectifying the second current using a second rectifier;

filtering the third current using inductance of the third secondary winding, the third winding being connected in series with an output capacitor;

charging the output capacitor using the third current;

providing dc power to a power-consuming device using the output capacitor.

12. A method according to claim 11,

wherein the providing step is performed by a drive circuit; and

wherein the method further comprises controlling the drive circuit using a drive control circuit, the drive control circuit controlling the drive circuit such that a pulse-width modulated voltage is applied to the primary winding.

13. A method according to claim 12,

wherein the drive control circuit receives measurement of an output voltage of the output capacitor from a voltage measurement circuit;

and

wherein the drive control circuit controls a duty cycle of the pulse width modulated voltage so as to minimize deviation of the output voltage from a predetermined setpoint level.

14. A method according to claim 13, wherein the predetermined setpoint level is less than about five volts.

15. A method according to claim 14, wherein the output capacitor provides an output current to the power consuming device that is greater than about thirty amps.

16. A method according to claim 11, wherein the output capacitor provides in excess of one-hundred watts of power to the power-consuming device.

17. A dc/dc converter circuit comprising:

(A) a magnetic core, the magnetic core having a center leg, a first outer leg, and a second outer leg, the first and second outer legs being disposed on opposite sides of the center leg;

(B) a primary winding;

(C) an output capacitor, the output capacitor having first and second terminals which respectively form first and second output terminals of the dc/dc converter circuit;

(D) a first secondary winding, the first secondary winding being wound around the first outer leg of the magnetic core,

(E) a second secondary winding, the second secondary winding being wound around the second outer leg of the magnetic core, and

(F) a third secondary winding, the third secondary winding implementing a filtering inductor and being connected in series with the output capacitor;

(G) a first rectifier, the first rectifier being connected between the output capacitor and the first secondary winding;

(H) a second rectifier, the second rectifier being connected between the output capacitor and the second secondary winding;

(I) a circuit board, the circuit board having the magnetic core mounted thereto, with the first and second outer legs and the center leg of the transformer extending through holes formed in the circuit board, and the circuit board having traces which at least partially form the primary winding, the first secondary winding, the second secondary winding, and the third secondary winding;

(J) an drive circuit, the drive circuit being connected to receive power from an input voltage source and being connected across the primary winding to provide a pulse width modulated voltage to the primary winding; and

(K) a feedback control circuit, the feedback control circuit including a voltage measurement circuit, the voltage measurement circuit being connected to the output capacitor to measure an output voltage across the first and second output terminals, and the feedback control circuit controlling the drive circuit to vary a duty cycle of a pulse width modulated voltage applied by the drive circuit to the primary winding, the duty cycle being controlled based on the measured output voltage to minimize deviation from of the output voltage from a setpoint level.

18. A circuit according to claim 17, wherein the third secondary winding is wound around the center leg of the magnetic core.

19. A circuit according to claim 17, wherein the third secondary winding comprises a first subwinding which is wound around the first outer leg and a second subwinding which is wound around the second outer leg.

20. A circuit according to claim 17, wherein the output capacitor produces a DC output voltage that is less than about ten volts and produces a DC output current that is more than about ten amps.

21. A circuit according to claim 20, wherein the output capacitor produces a DC output voltage that is less than about five volts and produces a DC output current that is more than about thirty amps.

22. A circuit according to claim 17, wherein the first secondary winding, the second secondary winding, and the third secondary winding cooperate to give the circuit an effective filtering inductance having the form $L=\frac{{(N_s+2}^{}}{}$

Nc)22

ℜ

c+ℜ

o,

where N_s is a number of turns of the first secondary winding an the second secondary winding, N_c is the number of turns of the third secondary winding, _c

is a reluctance of the center leg of the magnetic core, and _o

is a reluctance of the first and second outer legs of the magnetic core.