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US5744994A
Expired / Lapsed
US
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Three-terminal power mosfet switch for use as synchronous rectifier or voltage clamp
Assignee: Vishay Siliconix Inc
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Filing: 1996-05-15
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Granted: 1998-04-28
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Expires: 2016-05-15
Abstract
Abstract An N-channel power MOSFET is fabricated with its source and body connected together and biased at a positive voltage with respect to its drain. The gate is controlled by a switch which alternately connects the gate to the source or to a voltage which turns the channel of the MOSFET fully on. When the gate is connected to the source, the device functions as a "pseudo-Schottky" diode which turns on at a lower voltage and provides a lower-resistance path than a conventional PN diode. When the gate is connected to the positive voltage the channel of the MOSFET is turned fully on. This MOSFET switch is particularly suitable for use as a synchronous rectifier in a power converter where it reduces the power loss and stored charge in the "break before make" interval (i.e., the interval between the turn-off of the shunt switch and the turn-on of the synchronous rectifier).
Inventors
- 👤 Richard K. Williams
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 15:28
CPC Classifications
H; H10; H10D; H10D48/00; H10D48/30; H10D48/32; H10D48/36; H10D30/00; H10D30/60; H10D30/64; H10D30/66; H10D30/668; H02; H02M; H02M3/00; H02M3/02; H02M3/04; H02M3/10; H02M3/145; H02M3/155; H02M3/156; H02M3/158; H02M3/1588; H02M7/00; H02M7/02; H02M7/04; H02M7/12; H02M7/21; H02M7/217; H10D62/00; H10D62/10; H10D62/17; H10D62/351; H10D62/357; H10D62/364; H10D62/378; H10D64/00; H10D64/20; H10D64/27; H10D64/529; H10D8/00; H10D89/00; H10D89/60; Y; Y02; Y02B; Y02B70/00; Y02B70/10
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
135 words
A semiconductor device comprising: a source region of a first conductivity type; a body region of a second conductivity type opposite to said first conductivity type adjacent said source region; a drain region of said first conductivity type adjacent said body region, wherein said source region and said body region are connected together and biased at a first voltage and said drain region is biased at a second voltage, said first and second voltages being established such that a junction between said body region and said drain region is forward-biased; a gate separated by an insulating layer from a channel region of said body region; and a first switch for alternately connecting said gate to said source region or to a third voltage, said third voltage being sufficient to turn said semiconductor device fully on.
Claim 2
Dependent Claim
135 words
A semiconductor device comprising: a source region of a first conductivity type; a body region of a second conductivity type opposite to said first conductivity type adjacent said source region; a drain region of said first conductivity type adjacent said body region, wherein said source region and said body region are connected together and biased at a first voltage and said drain region is biased at a second voltage, said first and second voltages being established such that a junction between said body region and said drain region is forward-biased; a gate separated by an insulating layer from a channel region of said body region; and a first switch for alternately connecting said gate to said source region or to a third voltage, said third voltage being sufficient to turn said semiconductor device fully on.
Claim 3
Dependent Claim
24 words
The semiconductor device of claim 1 wherein an absolute value of said third voltage is greater than an absolute value of said first voltage.
Claim 4
Dependent Claim
173 words
A power converter comprising: a semiconductor device comprising: a source region of a first conductivity type; a body region of a second conductivity type opposite to said first conductivity type adjacent said source region; a drain region of said first conductivity type adjacent said body region, wherein said source region and said body region are connected together and biased at a first voltage and said drain region is biased at a second voltage, said first and second voltages being established such that a junction between said body region and said drain region is forward-biased; a gate separated by an insulating layer from a channel region of said body region; and a first switch for alternately connecting said gate to said source region or to a third voltage, said third voltage being sufficient to turn said semiconductor device fully on; said power converter further comprising: an inductor; and a second switch connected in series with said inductor; wherein said semiconductor device is connected to a common node between said inductor and said second switch.
Claim 5
Dependent Claim
173 words
A power converter comprising: a semiconductor device comprising: a source region of a first conductivity type; a body region of a second conductivity type opposite to said first conductivity type adjacent said source region; a drain region of said first conductivity type adjacent said body region, wherein said source region and said body region are connected together and biased at a first voltage and said drain region is biased at a second voltage, said first and second voltages being established such that a junction between said body region and said drain region is forward-biased; a gate separated by an insulating layer from a channel region of said body region; and a first switch for alternately connecting said gate to said source region or to a third voltage, said third voltage being sufficient to turn said semiconductor device fully on; said power converter further comprising: an inductor; and a second switch connected in series with said inductor; wherein said semiconductor device is connected to a common node between said inductor and said second switch.
Claim 6
Dependent Claim
16 words
The power converter of claim 3 further comprising a charge pump for supplying said third voltage.
Claim 7
Dependent Claim
29 words
The power converter of claim 3 wherein said first switch connects said gate to said source region during a break-before-make interval immediately after an opening of said second switch.
Claim 8
Dependent Claim
24 words
The power converter of claim 5 wherein said first switch connects said gate to said third voltage at a termination of said break-before-make interval.
Claim 9
Dependent Claim
73 words
A method of operating the power converter of claim 3 comprising the following sequence of steps: maintaining said second switch in a closed condition while maintaining said first switch in a first position which connects said gate to said source region; opening said second switch while maintaining said first switch in said first position; and moving said first switch to a second position so as to connect said gate to said third voltage.
Claim 10
Dependent Claim
19 words
The method of claim 7 further comprising the step of using a charge pump to supply said third voltage.
References Cited (Backward Citations)
US4667144A
Cited
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 2001-04-27 | 2001-10-27 | 2002-04-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-04-27 | 2005-10-27 | 2006-04-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-04-27 | 2009-10-27 | 2010-04-28 | $7700.00 | Window Closed / Lapsed |