US4903189A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Low noise, high frequency synchronous rectifier
Assignee: Fairchild Semiconductor Corp
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Filing: 1988-04-27
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Granted: 1990-02-20
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Expires: 2008-04-27
Abstract
Abstract A synchronous rectifier is able to operate at higher frequencies and provides an output having lower noise than prior art FET synchronous rectifier system by using field effect switching devices which contain only one conductivity type of semiconductor material and connecting a high speed, low charge storage diode in parallel. Schottky diodes are preferred whereby there is no junction diode in the structure. Conventional FETs may be used when paralleled with a Schottky diode which prevents the FET's parasitic internal diode from becoming conductive.
Inventors
- 👤 Khai D. T. Ngo
- 👤 Robert L. Steigerwald
- 👤 John P. Walden
- 👤 Bantval J. Baliga
- 👤 Charles S. Korman
- 👤 Hsueh-Rong Chang
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 15:12
CPC Classifications
H; H10; H10D; H10D30/00; H10D30/202; H02; H02M; H02M7/00; H02M7/02; H02M7/04; H02M7/12; H02M7/21; H02M7/217; H10D30/60; H10D30/63; H10D30/635
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
130 words
In a high efficiency synchronous rectifier circuit of the type including switching devices whose conductive state is controlled by an external control signal, a transformer for supplying an AC voltage to said switching devices for rectification and an output terminal, the improvement comprising: each of said switching devices comprising: an insulated gate field effect transistor in which all of the semiconductor material is of a single conductivity type, and a diode connected in parallel with said field effect transistor in an orientation to conduct transient currents in its forward direction when said field effect transistor is non-conductive; and said switching devices, said transformer and said output terminal being interconnected so that a current path from said transformer to said output terminal is free of series connections of said switching devices.
Claim 2
Dependent Claim
130 words
In a high efficiency synchronous rectifier circuit of the type including switching devices whose conductive state is controlled by an external control signal, a transformer for supplying an AC voltage to said switching devices for rectification and an output terminal, the improvement comprising: each of said switching devices comprising: an insulated gate field effect transistor in which all of the semiconductor material is of a single conductivity type, and a diode connected in parallel with said field effect transistor in an orientation to conduct transient currents in its forward direction when said field effect transistor is non-conductive; and said switching devices, said transformer and said output terminal being interconnected so that a current path from said transformer to said output terminal is free of series connections of said switching devices.
Claim 3
Dependent Claim
30 words
The synchronous rectifier circuit recited in claim 1 wherein: each of said switching devices consists of a single chip in which said field effect transistor and said diode are integrated.
Claim 4
Dependent Claim
42 words
The synchronous rectifier circuit recited in claim 2 wherein: said integrated switching device is a three terminal device having said diode connected between source and drain electrodes of said field effect transistor with the three terminals being source, drain and gate terminals.
Claim 5
Dependent Claim
14 words
The synchronous rectifier circuit recited in claim 3 wherein: said diodes are Schottky diodes.
Claim 6
Dependent Claim
73 words
The synchronous rectifier recited in claim 4 wherein: said insulated gate field effect transistor is an accumulation mode device having heavily doped source and drain regions spaced apart by a lightly doped drift region, said drift region having an insulated gate electrode adjacent thereto, said device being rendered conductive by application of a gate voltage to said gate electrode which induces an accumulation layer within said drift region adjacent to said gate electrode.
Claim 7
Dependent Claim
14 words
The synchronous rectifier circuit recited in claim 1 wherein: said diodes are Schottky diodes.
Claim 8
Dependent Claim
35 words
The synchronous rectifier circuit recited in claim 1 wherein: said transformer is designed to operate at frequencies in excess of 2 MHz; and said diodes have a reverse recovery time of less than 100 nanoseconds.
Claim 9
Dependent Claim
73 words
The synchronous rectifier recited in claim 1 wherein: said insulated gate field effect transistor is an accumulation mode device having heavily doped source and drain regions spaced apart by a lightly doped drift region, said drift region having an insulated gate electrode adjacent thereto, said device being rendered conductive by application of a gate voltage to said gate electrode which induces an accumulation layer within said drift region adjacent to said gate electrode.
Claim 10
Dependent Claim
106 words
The synchronous rectifier circuit recited in claim 1 wherein said transformer includes a secondary winding including first and second portions connected in common to a center tap and having first and second outer terminals, respectively and said circuit further comprises: an output filter providing its output at said output terminal and having an input terminal and a reference terminal, said input terminal being connected to said center tap of said transformer; a first one of said switching devices connected between said first outer terminal and said reference terminal; and a second one of said switching devices connected between said second outer terminal and said reference terminal.
Claim 11
Dependent Claim
38 words
The synchronous rectifier circuit recited in claim 9 wherein: said switching devices are oriented with the anode of said diode connected to said reference terminal for positive DC voltages at said output terminal relative to said reference terminal.
Claim 12
Dependent Claim
35 words
The synchronous rectifier circuit recited in claim 9 wherein: said transformer is designed to operate at frequencies in excess of 2 MHz; and said diodes have a reverse recovery time of less than 100 nanoseconds.
Claim 13
Dependent Claim
131 words
In a high efficiency synchronous rectifier circuit of the type including switching devices whose conductive state is controlled by an external control signal, a transformer for applying an AC voltage to said switching devices for rectification and an output terminal, the improvement comprising: each of said switching devices comprising: an insulated gate field effect transistor in which all of the semiconductor material is of a single conductivity type, and a Schottky diode connected in parallel with said field effect transistor in an orientation to conduct transient current in its forward direction when said field effect transistor is non-conductive; and said switching devices, said transformer and said output terminal being interconnected so that a current path from said transformer to said output terminals is free of series connections of said switching devices.
Claim 14
Dependent Claim
131 words
In a high efficiency synchronous rectifier circuit of the type including switching devices whose conductive state is controlled by an external control signal, a transformer for applying an AC voltage to said switching devices for rectification and an output terminal, the improvement comprising: each of said switching devices comprising: an insulated gate field effect transistor in which all of the semiconductor material is of a single conductivity type, and a Schottky diode connected in parallel with said field effect transistor in an orientation to conduct transient current in its forward direction when said field effect transistor is non-conductive; and said switching devices, said transformer and said output terminal being interconnected so that a current path from said transformer to said output terminals is free of series connections of said switching devices.
Claim 15
Dependent Claim
30 words
The synchronous rectifier circuit recited in claim 12 wherein: each of said switching devices consists of a single chip in which said field effect transistor and said diode are integrated.
Claim 16
Dependent Claim
43 words
The synchronous rectifier circuit recited in claim 13 wherein: said integrated switching device is a three terminal device having said Schottky diode connected between source and drain electrodes of said field effect transistor with the three terminals being source, drain and gate terminals.
Claim 17
Dependent Claim
73 words
The synchronous rectifier recited in claim 14 wherein: said insulated gate field effect transistor is an accumulation mode device having heavily doped source and drain regions spaced apart by a lightly doped drift region, said drift region having an insulated gate electrode adjacent thereto, said device being rendered conductive by application of a gate voltage to said gate electrode which induces an accumulation layer within said drift region adjacent to said gate electrode.
Claim 18
Dependent Claim
93 words
The synchronous rectifier circuit recited in claim 12 wherein said transformer includes a secondary winding including first and second portions connected in common to a center tap and having first and second outer terminals, respectively, further comprising: an output filter having input, output and reference terminals, said input terminal being connected to said center tap of said transformer; a first one of said switching devices connected between said first outer terminal and said reference terminal; and a second one of said switching devices connected between said second outer terminal and said reference terminal.
Claim 19
Dependent Claim
39 words
The synchronous rectifier circuit recited in claim 16 wherein: said switching devices are oriented with the anode of said Schottky diode connected to said reference terminal for positive DC voltages at said output terminal relative to said reference terminal.
Claim 20
Dependent Claim
35 words
The synchronous rectifier circuit recited in claim 16 wherein: said transformer is designed to operate at frequencies in excess of 2 MHz; and said diodes have a reverse recovery time of less than 100 nanoseconds.
Claim 21
Dependent Claim
35 words
The synchronous rectifier circuit recited in claim 12 wherein: said transformer is designed to operate at frequencies in excess of 2 MHz; and said diodes have a reverse recovery time of less than 100 nanoseconds.
Claim 22
Dependent Claim
74 words
The synchronous rectifier recited in claim 12 wherein: said insulated gate field effect transistor is an accumulation mode device having heavily doped source and drain regions spaced apart by a lightly doped drift region, said drift region having an insulated gate electrode adjacent thereto, said device being rendered conductive by application of a gate voltage to said gate electrode which induces an accumulation layer within said drift region adjacent to said gate electrode. S
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-02-19 | 1993-08-21 | 1994-02-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-02-19 | 1997-08-21 | 1998-02-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-02-19 | 2001-08-21 | 2002-02-20 | $7700.00 | Window Closed / Lapsed |