USRE37510EExpiredUtilityPatentIndex 91
Self-synchronized drive circuit for a synchronized rectifier in a clamped-mode power converter
Est. expiryMay 25, 2015(expired)· nominal 20-yr term from priority
Y02B70/10Y02E10/50H02M 3/33592
91
PatentIndex Score
28
Cited by
65
References
76
Claims
Abstract
A power converter with a self synchronized synchronous rectifier includes one or two drive windings to provide positive drive to the control electrodes of the controlled switches (FETs) of a self synchronized synchronous rectifier. The polarities of these windings am selected so that the switched devices are driven appropriately to rectify the periodic signal output of the secondary winding of the power transformer of the converter. In some arrangements one or two drive windings are included as extra windings in the power transformer and connected to provide the proper polarity drive signals. The turn ratios of the drive windings to the other windings are selected to provide the proper gate drive signal levels. In an alternative arrangement a separate drive transformer may be provided to supply the gate drive signals.
Claims
exact text as granted — not AI-modifiedThe invention claimed is:
1. A DC to DC power converter comprising:
a power transformer having a primary winding and a secondary winding;
a primary circuit for connecting an input DC voltage to the primary winding and including a power switch periodically biased conducting for connecting the input DC voltage to the primary winding and drawing power from the input DC voltage during its conduction and a clamping circuit connected to the primary winding and including energy storage means for sustaining a voltage across the primary winding during an interval when the power switch is biased non-conducting;
a separate drive winding magnetically coupled to receive energy from a primary side of the DC to DC power converter;
a secondary circuit connected to receive electrical energy from the secondary winding and for coupling the energy to an output;
the secondary circuit including;
a low pass output filter connected to the output and a synchronous rectifier circuit connecting the secondary winding to the low pass output filter;
wherein the synchronous rectifier circuit comprises:
first and second synchronous rectifier switches each controlled by a signal applied to an included control electrode of the switch;
first and second voltage limiting switches connected in series with the included control electrodes of the first and second synchronous rectifier switches such that the voltage limiting switches limit the amount of voltage supplied from the drive winding to the included control electrodes of the first and second synchronous rectifier switches;
means for establishing a DC potential on gate electrodes of the first and second gate switches; and
the drive winding being connected to power path electrodes of the first and second gate switches and connected to alternatively energize the included gates of the first and second synchronous rectifier switches through the first and second gate switches.
2. A DC to DC power converter, comprising:
a power transformer having a primary winding and a secondary winding;
a primary circuit for connecting an input DC voltage to the primary winding and including, a power switch and a clamping circuit for sustaining a voltage in the secondary winding during non-conduction of the power switch;
a secondary circuit for coupling energy transfer from the secondary winding to an output and including, a low pass output filter connected to the output and a synchronous rectifier connecting the secondary winding to the low pass output filter; and
the synchronous rectifier including;
first and second synchronous rectifier switches each controlled by a signal applied to an included control electrode, first and second voltage limit switch devices connected to limit a voltage of drive signals applied to the first and second synchronous rectifier switches and an a separate drive winding connected to alternatively energize the first and second synchronous rectifier switches.
3. A DC to DC power converter, comprising:
a power transformer having a primary winding and a secondary winding;
a primary circuit for connecting an input DC voltage to the primary winding and including, a power switch and a circuit that reverses the polarity of the secondary voltage during a portion of the period of non-conduction of the power switch sufficient to ensure the reset of the transformer magnetic core;
a secondary circuit for coupling energy transfer from the secondary winding to an output and including, a low pass output filter connected to the output and a synchronous rectifier connecting the secondary winding to the low pass output filter;
the synchronous rectifier including;
first and second synchronous rectifier switches each controlled by a signal applied to an included control electrode, first and second voltage limit switch devices connected to limit a voltage of drive signals applied to the first and second synchronous rectifier switches and a separate drive winding connected to alternately energize the first and second synchronous rectifier switches.
4. A DC to DC power converter as claimed in claim 1 , 2 or 3 comprising:
the primary and secondary circuits being magnetically coupled and including power circuitry to operate as a forward converter; and the drive winding being wound on the power transformer.
5. A DC to DC power converter as claimed in claim 1 , 2 or 3 comprising:
the primary and secondary circuits being magnetically coupled and including power circuitry to operate as a flyback converter;
and the drive winding being wound on the power transformer.
6. A DC to DC power converter as claimed in claim 1 , 2 or 3 comprising:
the power transformer includes a tapped secondary winding; and
the drive winding is wound on a core of the power transformer.
7. A DC to DC power converter as claimed in claim 1 , 2 or 3 comprising:
the primary and secondary circuits being magnetically coupled and including power circuitry to operate as a forward converter;
a second transformer magnetically coupling the primary circuit and the secondary circuit and
the drive winding being wound on the second transformer.
8. A DC to DC power converter as claimed in claim 1 , 2 or 3 comprising:
the primary and secondary circuits being magnetically coupled and including power circuitry to operate as a flyback converter;
a second transformer magnetically coupling the primary circuit and the secondary circuit and
the drive winding being wound on the second transformer.
9. A DC to DC power converter as claimed in claim 1 , 2 , or 3 comprising:
the power transformer includes a tapped secondary winding; and
a second transformer Magnetically coupling the primary circuit and the secondary circuit and the drive winding being wound on the second transformer.
10. A DC to DC power converter as claimed in claim 1 , 2 or 3 comprising:
a second drive transformer is included for accepting the drive winding and is connected in a circuit in parallel with the power switch; and
the primary and secondary circuits being magnetically coupled and including power circuitry to operate as a forward converter.
11. A DC to DC power converter as claimed in claim 1 , 2 or 3 comprising:
a second drive transformer is included for accepting the drive winding and is connected in parallel with the power switch; and
the primary and secondary circuits being magnetically coupled and including power circuitry to operate as a flyback converter.
12. A DC to DC power converter as claimed in claim 1 , 2 or 3 comprising:
the low pass output filter including a filter inductor in series with the output and the power transformer having a tapped secondary winding connected to the low pass output filter; and
a second transformer including a primary winding connected in parallel with the power switch and the secondary winding connected to drive the first and second voltage limit switches, exclusively electromagnetically coupled to the primary winding.
13. A DC to DC power converter as claimed in claim 1 , 2 or 3 comprising:
a second drive transformer is included for accepting the drive winding and is connected in a circuit connected in parallel with the power transformer; and
the primary and secondary circuits being magnetically coupled and including power circuitry to operate as a forward converter.
14. A DC to DC power converter as claimed in claim 1 , 2 or 3 comprising:
a second drive transformer is included for accepting the drive winding and is connected in a circuit connected in parallel with the power transformer; and
the primary and secondary circuits being magnetically coupled and including power circuitry to operate as a flyback converter.
15. A DC to DC power converter as claimed in claim 1 , 2 or 3 comprising:
a second drive transformer is included for accepting the drive winding and is connected in a circuit connected in parallel with the power transformer; and
the power transformer includes a tapped secondary winding.
16. A DC to DC power converter as claimed in claim 1 , 2 or 3 comprising:
the primary and secondary circuits being magnetically coupled, and
further including circuitry to operate as a forward converter.
17. A DC to DC power converter as claimed in claim 1 , 2 or 3 comprising:
the primary and secondary circuits being magnetically coupled, and
including circuitry to operate as a flyback converter.
18. A DC to DC power converter as claimed in claim 1 , 2 or 3 comprising:
the power transformer having a tapped secondary winding connected to the low pass output filter.
19. A DC to DC power converter as claimed in claim 1 , 2 or 3 comprising:
the drive winding being wound on the power transformer.
20. A DC to DC power converter as claimed in claim 1 , 2 or 3 comprising:
a second transformer including a primary winding connected in parallel with the power switch and the drive winding connected to drive the first and second voltage-limit voltage limit switches, and the drive winding exclusively electromagnetically coupled to the second transformer.
21. A DC to DC power converter as claimed in claim 1 , 2 or 3 comprising:
a second transformer having a primary winding connected in parallel with the power switch and a drive winding connected to drive the first and second voltage-limit voltage limit switches.
22. A DC to DC power converter as claimed in claim 1 , 2 or 3 comprising:
a second transformer having a primary winding connected in parallel with the primary winding of the power transformer and a drive winding connected to drive the first and second voltage-limit voltage limit switches.
23. A DC to DC power converter as claimed in claim 1 , 2 or 3 comprising:
at least one of the rectifier switches being a diode.
24. A DC to DC power converter comprising:
a power transformer having a primary winding and a secondary winding;
a primary circuit for connecting an input DC voltage to the primary winding and including, a power switch and a clamping circuit for sustaining a voltage in the secondary winding during non-conduction of the power switch;
a secondary circuit for coupling energy transfer from the secondary winding to an output and including, a low pass output filter connected to the output and a synchronous rectifier connecting the secondary winding to the low pass output filter;
the secondary winding having a tap to define a drive portion of the secondary winding; and
the synchronous rectifier including:
first and second synchronous rectifier switches each controlled by a signal applied to an included control electrode, first and second voltage-limit positive and negative voltage limit switch devices connected to limit a positive and negative voltage, respectively, of drive signals applied to the first and second synchronous rectifier switches and the drive portion of the secondary winding connected to periodically energize at least one of the first and second synchronous rectifier switches, and another one of the first and second synchronous rectifiers being connected to be energized by an output of the secondary winding.
25. A DC to DC power converter comprising:
a power transformer having a primary winding and a secondary winding;
a primary circuit for connecting an input DC voltage to the primary winding and including, a power switch and a clamping circuit for sustaining a voltage in the secondary winding during non-conduction of the power switch;
a secondary circuit for coupling energy transfer from the secondary winding to an output and including, a low pass output filter connected to the output and a synchronous rectifier connecting the secondary winding to the low pass output filter,
the secondary winding having at least a first and second tap to define first and second drive portions of the secondary winding; and
the synchronous rectifier including:
first and second synchronous rectifier switches, each controlled by a signal applied to an included control electrode, first and second positive and negative voltage limit switch devices connected to limit a positive and negative voltage, respectively, of drive signals applied to the first and second synchronous rectifier switches, and the first drive portion of the secondary winding connected to periodically energize the first synchronous rectifier and the second drive portion of the secondary winding connected to periodically energize the second synchronous rectifier.
26. A DC to DC power converter, comprising:
a power transformer having a primary winding and a secondary winding;
a primary circuit for connecting an input DC voltage to the primary winding and including, a power switch;
a secondary circuit for coupling energy transfer from the secondary winding to an output and including, a low pass output filter connected to the output and a synchronous rectifier connecting the secondary winding to the low pass output filter, and
the synchronous rectifier including;
first and second synchronous rectifier switches each controlled by a signal applied to an included control electrode, first and second voltage limit switch devices connected to limit a voltage of drive signals applied to the first and second synchronous rectifier switches;
first and second diodes connected to limit a positive voltage applied to the gate electrodes of the first and second synchronous rectifier switches; and
a separate drive winding connected to alternatively energize the first and second synchronous rectifier switches.
27. A DC to DC power converter comprising:
a power transformer having a primary winding and a secondary winding;
a primary circuit for connecting an input DC voltage to the primary winding and including, a power switch;
a secondary circuit for coupling energy transfer from the secondary winding to an output and including, a low pass output filter connected to the output and a synchronous rectifier connecting the secondary winding to the low pass output filter;
the secondary winding having a tap to define a drive portion of the secondary winding; and
the synchronous rectifier including:
first and second synchronous rectifier switches each controlled by a signal applied to an included control electrode, first and second voltage-limit positive and negative voltage limit switch devices connected to limit a positive and negative voltage, respectively, of drive signals applied to the first and second synchronous rectifier switches and the drive portion of the secondary winding connected to periodically energize at least one of the first and second synchronous rectifier switches, and another one of the first and second synchronous rectifiers being connected to be energized by an output of the secondary winding.
28. A DC to DC power converter comprising:
a power transformer having a primary winding and a secondary winding;
a primary circuit for connecting an input DC voltage to the primary winding and including, a power switch;
a secondary circuit for coupling energy transfer from the secondary winding to an output and including, a low pass output filter connected to the output and a synchronous rectifier connecting the secondary winding to the low pass output filter,
the secondary winding having at least a first and second tap to define first and second drive portions of the secondary winding; and
the synchronous rectifier including:
first and second synchronous rectifier switches, each controlled by a signal applied to an included control electrode, first and second positive and negative voltage limit switch devices connected to limit a positive and negative voltage, respectively, of drive signals applied to the first and second synchronous rectifier switches, and the first drive portion of the secondary winding connected to periodically energize the first synchronous rectifier and the second drive portion of the secondary winding connected to periodically energize the second synchronous rectifier.
29. A power converter having an input and output, comprising:
a power transformer having, primary and secondary windings;
a power switch coupled to the input and configured to impress an input voltage across the primary winding;
a synchronous rectifier coupled to the secondary winding and including first and second synchronous rectifier switches; and
a separate drive winding wound on the power transformer and coupled between the first and second synchronous rectifier switches, the separate drive winding configured to alternately energize the first and second synchronous rectifier switches.
30. The power converter as claimed in claim 29 further comprising a low pass filter coupled between the secondary winding and the output.
31. The power converter as claimed in claim 29 further comprising first and second voltage limit switches that limit a voltage level of a signal applied to the first and second synchronous rectifier switches, respectively.
32. The power converter as claimed in claim 29 further comprising a voltage source that supplies a bias voltage to first and second voltage limit switches coupled to the first and second synchronous rectifier switches, respectively.
33. The power converter as claimed in claim 29 further comprising a clamp circuit coupled to the power transformer.
34. The power converter as claimed in claim 29 wherein the secondary winding has a center tap.
35. The power converter as claimed in claim 29 wherein at least one of the first and second synchronous rectifier switches is a diode.
36. The power converter as claimed in claim 29 further comprising first and second diodes that limit a voltage of a signal applied to the first and second synchronous rectifier switches, respectively.
37. The power converter as claimed in claim 29 further comprising first and second voltage limit switches and a voltage source that limit a negative voltage of a signal applied to the first and second synchronous rectifier switches, respectively.
38. The power converter as claimed in claim 29 further comprising a regulation control circuit and a drive circuit coupled between the output and the power switch.
39. The power converter as claimed in claim 29 wherein the separate drive winding is directly coupled to the first and second synchronous rectifier switches.
40. The power converter as claimed in claim 29 wherein the power converter is selected from the up consisting of:
a forward power converter,
a flyback power converter,
a buck power converter, and
a power converter with a tapped secondary winding.
41. A method of operating a power converter having an input output, comprising:
providing a power transformer having primary and secondary windings;
impressing an input voltage across the primary winding with a power switch coupled to the input;
alternately energizing first and second synchronous rectifier switches with a separate drive winding wound on the power transformer and coupled between the first and second synchronous rectifier switches.
42. The method as claimed in claim 41 further comprising filtering an output voltage of the power converter.
43. The method as claimed in claim 41 further comprising limiting a voltage level of a signal applied to the first and second synchronous rectifier switches.
44. The method as claimed in claim 41 further comprising supplying a bias voltage to first and second voltage limit switches coupled to the first and second synchronous rectifier switches respectively.
45. The method as claimed in claim 41 further comprising clamping a voltage level across the power transformer.
46. The method as claimed in claim 41 further comprising forming a center in the secondary winding.
47. The method as claimed in claim 41 wherein at least one of the first and second synchronous rectifier switches is a diode.
48. The method as claimed in claim 41 further comprising limiting a positive voltage of a signal applied to the first and second synchronous rectifier switches, respectively.
49. The method as claimed in claim 41 further comprising limiting a negative voltage of a signal applied to the first and second synchronous rectifier switches, respectively.
50. The method as claimed in claim 41 further comprising regulating an output voltage of the power converter.
51. The method as claimed in claim 41 wherein the separate drive winding is directly coupled to the first and second synchronous rectifier switches.
52. The method as claimed in claim 41 wherein the power converter is selected from the group consisting of:
a forward power converter,
a flyback power converter,
a buck power converter, and
a power converter with a tapped secondary winding.
53. A power converter having an input and output, comprising:
a power transformer having primary and secondary windings;
an auxiliary transformer coupled to the power transformer;
a power switch, coupled to the input that impresses an input voltage across the primary winding;
a synchronous rectifier coupled to the secondary winding and including first and second synchronous rectifier switches; and
a separate drive winding wound on the auxiliary transformer and coupled between the first and second synchronous rectifier switches, the separate drive winding configured to alternately energize the first and second synchronous rectifier switches.
54. The power converter as claimed in claim 53 further comprising a low pass filter coupled between the secondary winding and the output.
55. The power converter as claimed in claim 53 further comprising first and second voltage limit switches that limit a voltage level of a signal applied to the first and second synchronous rectifier switches, respectively.
56. The power converter as claimed in claim 53 further comprising a voltage source that supplies a bias voltage to first and second voltage limit switches coupled to the first and second synchronous rectifier switches, respectively.
57. The power converter as claimed in claim 53 further comprising a clamp circuit coupled to the power transformer.
58. The power converter as claimed in claim 53 wherein the secondary winding has a center tap.
59. The power converter as claimed in claim 53 wherein at least one of the first and second synchronous rectifier switches is a diode.
60. The power converter as claimed in claim 53 further comprising first and second diodes that limit a voltage of a signal applied to the first and second synchronous rectifier switches, respectively.
61. The power converter as claimed in claim 53 further comprising first and second voltage limit switches and a voltage source that limit a negative voltage of a signal applied to the first and second synchronous rectifier switches, respectively.
62. The power converter as claimed in claim 53 further comprising a regulation control circuit and a drive circuit coupled between the output and the power switch.
63. The power converter as claimed in claim 53 wherein the separate drive winding is directly coupled to the first and second synchronous rectifier switches.
64. The power converter as claimed in claim 53 wherein the power converter is selected from the a group consisting of:
a forward power converter,
a flyback power converter,
a buck power converter, and
a power converter with a tapped secondary winding.
65. A method of operating a power converter having an input and output, comprising:
providing a power transformer having primary and secondary winding;
coupling an auxiliary transformer to the power transformer;
impressing an input voltage across the primary winding with a power switch coupled to the input;
alternately energizing first and second synchronous rectifier switches with a separate drive winding wound on the auxiliary transformer and coupled between the first and second synchronous rectifier switches.
66. The method as claimed in claim 65 further comprising filtering an output voltage of the power converter.
67. The method as claimed in claim 65 further comprising limiting a voltage level of a signal applied to the first and second synchronous rectifier switches.
68. The method as claimed in claim 65 further comprising supplying a bias voltage to first and second voltage limit switches coupled to the first and second synchronous rectifier switches, respectively.
69. The method as claimed in claim 65 further comprising clamping a voltage level across the power transformer.
70. The method as claimed in claim 65 further comprising forming a center tap in the secondary winding.
71. The method as claimed in claim 65 wherein at least one of the first and second synchronous rectifier switches is a diode.
72. The method as claimed in claim 65 further comprising limiting a positive voltage of a signal applied to the first and second synchronous rectifier switches, respectively.
73. The method as claimed in claim 65 further comprising limiting a negative voltage of a signal applied to the first and second synchronous rectifier switches, respectively.
74. The method as claimed in claim 65 further comprising regulating an output voltage of the power converter.
75. The method as claimed in claim 65 wherein the separate drive winding is directly coupled to the first and second synchronous rectifier switches.
76. The method as claimed in claim 65 wherein the power converter is selected from the group consisting of:
a forward power converter,
a flyback power converter,
a buck power converter, and
a power converter with a tapped secondary winding.Cited by (0)
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