US6031702A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Short circuit protected DC-DC converter using disconnect switching and method of protecting load against short circuits
Assignee: Vishay Siliconix Inc
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Filing: 1997-10-22
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Granted: 2000-02-29
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Expires: 2017-10-22
Abstract
Abstract A four-terminal MOSFET, in which no combination of the source, drain, body and gate terminals are permanently connected together, is used as a synchronous rectifier capable of blocking an excessive current in a switching mode DC--DC converter resulting from a short-circuited load. In an N-channel version of the synchronous rectifier, the MOSFET body terminal is normally connected to the inductor in the DC--DC converter and is grounded when an overcurrent condition is detected. In a P-channel version of the synchronous rectifier, the MOSFET body terminal is normally connected to the converter output and is connected to the inductor when an overcurrent condition is detected. In addition, the voltage output by the inductor may be clamped using a zener diode or a snubber capacitor. A MOSFET body bias switching circuit is driven by overcurrent detection circuitry that may also be used to turn off the synchronous rectifier MOSFET gate.
Inventors
- 👤 Richard K. Williams
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 09:54
CPC Classifications
H; H02; H02H; H02H7/00; H02H7/10; H02H7/12; H02H7/1213; H02M; H02M3/00; H02M3/02; H02M3/04; H02M3/10; H02M3/145; H02M3/155; H02M3/156; H02M3/158; H02M3/1588; H02M1/00; H02M1/32; Y; Y02; Y02B; Y02B70/00; Y02B70/10
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
121 words
A DC--DC converter comprising: an inductor and a MOSFET switch connected in series between a supply voltage and ground; and a disconnect MOSFET connected to a common node between said inductor and said MOSFET switch, said disconnect MOSFET comprising: a first parasitic diode between a body and a first terminal of said disconnect MOSFET and a second parasitic diode between said body and a second terminal of said disconnect MOSFET; a first switch connected in parallel with said first parasitic diode; and an overcurrent sensing circuit coupled to a current path through said disconnect MOSFET and responsive to an excessive current through said disconnect MOSFET, said first switch being opened in response to an output signal from said overcurrent sensing circuit.
Claim 2
Dependent Claim
121 words
A DC--DC converter comprising: an inductor and a MOSFET switch connected in series between a supply voltage and ground; and a disconnect MOSFET connected to a common node between said inductor and said MOSFET switch, said disconnect MOSFET comprising: a first parasitic diode between a body and a first terminal of said disconnect MOSFET and a second parasitic diode between said body and a second terminal of said disconnect MOSFET; a first switch connected in parallel with said first parasitic diode; and an overcurrent sensing circuit coupled to a current path through said disconnect MOSFET and responsive to an excessive current through said disconnect MOSFET, said first switch being opened in response to an output signal from said overcurrent sensing circuit.
Claim 3
Dependent Claim
28 words
The DC--DC converter of claim 1 further comprising a second switch connected between said body and ground, said first switch being open when said second switch is closed.
Claim 4
Dependent Claim
52 words
The DC--DC converter of claim 2 further comprising a third switch connected to a gate of said disconnect MOSFET, said third switch being for connecting said gate to a first voltage so as to turn said disconnect MOSFET on or to a second voltage so as to turn said disconnect MOSFET off.
Claim 5
Dependent Claim
20 words
The DC--DC converter of claim 3 wherein said third switch is responsive to an output of said overcurrent sensing circuit.
Claim 6
Dependent Claim
31 words
The DC--DC converter of claim 4 wherein a signal indicating an overcurrent condition at an output of said overcurrent sensing circuit causes said third switch to turn said disconnect MOSFET off.
Claim 7
Dependent Claim
22 words
The DC--DC converter of claim 2 wherein said first switch comprises a first MOSFET and said second switch comprises a second MOSFET.
Claim 8
Dependent Claim
44 words
The DC--DC converter of claim 6 wherein one of said first and second MOSFETs is a P-channel MOSFET and the other of said first and second MOSFETs is an N-channel MOSFET and the respective gates of said first and second MOSFETs are coupled together.
Claim 9
Dependent Claim
29 words
The DC--DC converter of claim 7 wherein a voltage at said gates of said first and second MOSFETs is responsive to an output signal from said overcurrent sensing circuit.
Claim 10
Dependent Claim
25 words
The DC--DC converter of claim 1 further comprising a conductive path containing a zener diode, said conductive path being connected in parallel with said inductor.
Claim 11
Dependent Claim
20 words
The DC--DC converter of claim 9 wherein said conductive path comprises a second diode in series with said zener diode.
Claim 12
Dependent Claim
26 words
The DC--DC converter of claim 1 wherein said disconnect MOSFET is an N-channel MOSFET, said first switch being connected between said common node and said body.
Claim 13
Dependent Claim
30 words
The DC--DC converter of claim 1 wherein said disconnect MOSFET is a P-channel MOSFET, said first switch being connected between an output terminal of said DC--DC converter and said body.
Claim 14
Dependent Claim
35 words
The DC--DC converter of claim 12 further comprising a second switch connected in parallel with said second parasitic diode, said second switch being open except when an excessive current is flowing through said disconnect MOSFET.
Claim 15
Dependent Claim
18 words
The DC--DC converter of claim 1 further comprising a zener diode connected between said common node and ground.
Claim 16
Dependent Claim
19 words
The DC--DC converter of claim 14 further comprising a snubber capacitor connected between said common node and said body.
Claim 17
Dependent Claim
30 words
The DC--DC converter of claim 1 further comprising a current sense resistor connected in a current flow path through said disconnect MOSFET for detecting the presence of said excessive current.
Claim 18
Dependent Claim
36 words
The DC--DC converter of claim 16 further comprising a comparator having an input terminal coupled to said current sense resistor, an output of said comparator being coupled to an input terminal of said overcurrent sensing circuit.
Claim 19
Dependent Claim
24 words
The DC--DC converter of claim 1 wherein said overcurrent sensing circuit comprises a sensing resistor connected in said current path through said disconnect MOSFET.
Claim 20
Dependent Claim
20 words
The DC--DC converter of claim 18 wherein said overcurrent sensing circuit further comprises a comparator coupled to said sensing resistor.
Claim 21
Dependent Claim
21 words
The DC--DC converter of claim 19 wherein said first switch is responsive to a signal at an output of said comparator.
Claim 22
Dependent Claim
21 words
The DC--DC converter of claim 20 wherein said second switch is responsive to said signal at said output of said comparator.
Claim 23
Independent Claim
113 words
A method of protecting a load against an excessive current when said load becomes short-circuited, said method comprising the steps of: connecting said load to a four-terminal MOSFET, said MOSFET comprising a first parasitic diode between a body and a first terminal of said MOSFET and a second parasitic diode between said body and a second terminal of said MOSFET, said first diode being directed in opposition to a normal direction of current through said load; connecting a switch in parallel with said first diode; closing said switch when said load is drawing a normal current; sensing an overcurrent condition in said load; and opening said switch in response to said overcurrent condition.
Claim 24
Independent Claim
113 words
A method of protecting a load against an excessive current when said load becomes short-circuited, said method comprising the steps of: connecting said load to a four-terminal MOSFET, said MOSFET comprising a first parasitic diode between a body and a first terminal of said MOSFET and a second parasitic diode between said body and a second terminal of said MOSFET, said first diode being directed in opposition to a normal direction of current through said load; connecting a switch in parallel with said first diode; closing said switch when said load is drawing a normal current; sensing an overcurrent condition in said load; and opening said switch in response to said overcurrent condition.
Claim 25
Dependent Claim
32 words
The method of claim 22 comprising the further step of biasing a gate of said MOSFET so as to turn a channel of said MOSFET off in response to said overcurrent condition.
Claim 26
Dependent Claim
24 words
The method of claim 22 comprising the further step of connecting said body of said MOSFET to ground in response to said overcurrent condition.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2003-02-28 | 2003-08-30 | 2004-02-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2007-02-28 | 2007-08-30 | 2008-02-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2011-02-28 | 2011-08-30 | 2012-02-29 | $7700.00 | Window Closed / Lapsed |