Voltage converter with coupled inductive windings, and associated methods

• US 6,362,986 B1
• Filed: 03/22/2001
• Issued: 03/26/2002
• Est. Priority Date: 03/22/2001
• Status: Expired due to Term

• Current Assignee: Volterra Semiconductor LLC (Analog Devices, Inc.)
• Original Assignee: Volterra, Inc. (F5 Incorporated)
• Inventors: Sullivan, Charles R., Schultz, Aaron M.
• Primary Examiner(s): NGUYEN, MATTHEW VAN
• Application Number:
  US09/814,555
• Time in Patent Office: 369 Days
• Field of Search: 363/16, 363/17, 363/56.01, 363/56.02, 363/97, 363/98, 363/131, 363/132
• US Class Current: 363/132
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02M 3/1586 switched with a phase shift, i.e. interleaved

Abstract

A DC-to-DC converter generates an output voltage from an input voltage. The converter includes first and second inductive windings and a magnetic core. One end of the first winding is switched at about 180 degrees out of phase with one end of the second winding, between ground and the input voltage. The first winding is wound about the core in a first orientation, and the second winding is also wound about the core in the first orientation so as to increase coupling between windings and to reduce ripple current in the windings and other parts of the circuit. This version is a buck converter—versions that form boost, buck-boost and other converters are also provided. The invention also provides a multi-phase DC-to-DC converter for providing an output voltage from an input voltage. The converter has N (N≧2) inductive windings alternatively switched, again in the buck-converter version, between ground and the input voltage. Again, boost, buck-boost, or other versions are also provided. Each of the N windings has a turn-on switching transition separated in switching phase by at least about 360/N degrees from any other of the windings. Each of the windings also has a turn-off switching transition separated in phase by at least about 360/N degrees from any other of the windings. Each of the N windings is wound about the core in like orientation to increase coupling between windings and to reduce ripple current in the windings and other parts of the circuit. The invention also provides suitable core structures.

Claims

1. A DC-to-DC converter for providing an output voltage from an input voltage, comprising first and second inductive windings and a magnetic core cooperatively forming a magnetizing inductance, a first voltage across the first winding being switched at about 180 degrees out of phase with a second voltage across the second winding, to regulate magnitude of the output voltage, the first and second voltages being formed from one or a combination of the input and output voltages, each of the first and second windings having a leakage inductance and being coupled to the magnetic core wherein magnetizing inductance is at least three times greater than the leakage inductance of either winding, the first winding being wound about the core in a first orientation, the second winding being wound about the core in the first orientation.

2. A converter according to claim 1, wherein the input voltage comprises first and second input voltages.

3. A converter according to claim 2, wherein the second input voltage comprises ground, wherein the converter operates as a buck converter.

4. A converter according to claim 1, further comprising one or more transistors for switching the windings out of phase wherein a current per time slope during the time intervals in which current is increasing through the windings is approximately defined by the output voltage divided by the leakage inductance subtracted from one half the input voltage divided by the leakage inductance.

5. A converter according to claim 1, wherein the windings and core are constructed and arranged to substantially maximize coupling between windings by maintaining the leakage inductance at a substantially constant level while increasing the magnetizing inductance.

6. A converter according to claim 1, wherein the core comprises first and second substantially parallel core elements, the first winding being wound about the first core element the first orientation, the second winding being wound about the second core element in the first orientation.

7. A converter according to claim 6, further comprising one or more connecting elements rigidly coupling the first and second parallel core elements together.

8. A converter according to claim 1, wherein the core comprises one of a gapped high-permeability element and a low-permeability element, to serve as a leakage path structure to carry at least part of a leakage flux, the leakage flux being defined as a flux present when each of the windings has an equal DC current.

9. A converter according to claim 8, wherein the leakage path structure comprises a core leg or shunt.

10. A converter according to claim 1, further comprising circuitry to activate one or more of the windings at a selected duty cycle.

11. A converter according to claim 10, wherein the duty cycle comprises a duty cycle between about 5% and 90%.

12. A converter according to claim 10, wherein the duty cycle is about 50%.

13. A converter according to claim 1, further comprising circuitry to alternatively activate each of the windings at about 50% duty cycle.

14. A converter according to claim 1, wherein one end of each of the windings is switched between the input voltage and ground.

15. A converter according to claim 1, wherein the first and second windings have an equal number of turns in the windings.

16. A converter according to claim 1, wherein the first winding has a first number of turns and the second winding has a second number of turns, the first number being different from the second number, and wherein a NI product for each of the first and second windings is substantially equal.

17. A method for reducing ripple in a DC-to-DC converter of the type producing an output voltage from an input voltage, comprising the steps of:

orienting, in like direction, first and second windings about a common core to increase coupling between the windings; and

alternatively activating each winding about 180 degrees out of phase with the second winding, to regulate magnitude of the output voltage.

18. A method of claim 17, further comprising switching the voltages across the windings by connecting one end of each winding to a common output voltage, and individually switching the other end of each winding between ground and an input voltage.

19. The method of claim 17, further comprising the step of forming the core with two substantially parallel core elements, wherein the step of orienting comprises orienting each of the windings on a separate core element.

20. The method of claim 17, further comprising the step of activating one or more of the windings at a selected duty cycle.

21. The method of claim 20, wherein the step of activating comprises activating the windings at a duty cycle between about 5% and 90%.

22. The method of claim 20, wherein the step of activating comprises activating the windings at a duty cycle at about 50%.

23. The method of claim 17, further comprising the steps of forming a first number of turns in the first winding and a second number of turns in the second winding.

24. The method of claim 23, wherein the first number is different from the second number, and further comprising the steps of applying a first current through the first winding and applying a second current through the second winding, the first current being different from the second current, wherein a NI product for each of the first and second windings is substantially equal.

25. A DC to DC converter for providing an output voltage from one or more input voltages, comprising (a) a common magnetic core and (b) N inductive windings alternatively switched, at one end, to regulate magnitude of the output voltage, each of the windings having a turn-on switching transition separated in switching phase by at least about 360/N degrees from any other of the windings, each of the windings having a turn-off switching transition separated in phase by at least about 360/N degrees from any other of the windings, each of the N windings being wound about the core in like orientation, N being an integer greater than or equal to three.

26. A converter of claim 25, wherein each of the windings comprises a leakage inductance, each of the windings being coupled the common magnetic core wherein magnetizing inductance defined by magnetic interaction between the windings is greater than about three times the leakage inductance of any one of the windings.

27. A converter according to claim 26, further comprising one or more transistors for switching the windings out of phase wherein a current per time slope during the time intervals in which current is increasing through the windings is approximately defined by the output voltage divided by the leakage inductance subtracted from the input voltage divided by the leakage inductance divided by N.

28. A converter according to claim 26, wherein the windings and core are constructed and arranged to substantially maximize coupling between windings by maintaining the leakage inductance at a substantially constant level while increasing the magnetizing inductance.

29. A converter according to claim 26, wherein one or more of the windings comprise a gapped high permeability element to carry at least part of a leakage flux, the leakage flux being defined as a flux present when each of the windings has an equal DC current.

30. A converter of claim 25, wherein the core comprises a wheel and spoke configuration, and wherein each of the windings are wound about separate spokes of the configuration.

31. A converter of claim 25, wherein the core structure comprises a two-plate and multiple column configuration, and wherein each of the windings are wound about separate columns of the configuration.

32. A converter of claim 25, wherein the core structure comprises a two-ring and multiple column configuration, and wherein each of the windings are wound about separate columns of the configuration.

33. A converter according to claim 25, wherein the input voltages comprise first and second input voltages, the second input voltage comprising ground, wherein the converter operates as a buck converter.

34. A converter according to claim 25, wherein the core comprises N substantially parallel core elements, the N winding being wound about the N core elements in a same orientation.

35. A converter according to claim 34, further comprising one or more connecting elements rigidly coupling adjacent N parallel core elements together.

36. A converter according to claim 25, further comprising circuitry to activate one or more of the windings at a selected duty cycle.

37. A converter according to claim 36, wherein the duty cycle comprises a duty cycle between about 5% and 90%.

38. A converter according to claim 37, wherein the duty cycle is about 50%.

39. A converter according to claim 25, wherein each of the N inductive windings comprises an equal number of turns.

40. A converter according to claim 25, wherein at least one of the N inductive windings comprises a different number of turns from at least one other of the N windings.