EP0647026A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Over current protection device for transistor
Assignee: Fuji Electric Co Ltd
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Filing: 1994-09-30
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Granted: —
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Expires: 2014-09-30
Abstract
Abstract To prevent the oscillation which often occurs in an over current protection device for an insulated gate controlled transistor, an over current protection device is provided which improves the response in current detection to prevent the oscillation and improves protection speed against over current by separating the gates of a main transistor (10) and a current detector transistor (20); setting the time constant for the gate circuit of the detector transistor (20) shorter than that of the gate circuit of the main transistor (10); feeding a detection signal (Vd), obtained with current detecting means (Rd) which detects the current (i) of the detector transistor (20) proportional to the current (l) flowing through the main transistor (10), to control means (50); and controlling the transistors (10, 20) to protect the transistor (10) from the over current by feeding the comparison output Sd from a comparator circuit (30), which compares the voltage of the detection signal (Vd) with a reference voltage (Vr), to the control circuit (40).
Inventors
- 👤 Tatsuhiko C/O Fuji Electric Co. Ltd. Fujihara
- 👤 Shin C/O Fuji Electric Co. Ltd. Kiuchi
- 👤 Kazuhiko C/O Fuji Electric Co. Ltd. Yoshida
- 👤 Yukio C/O Fuji Electric Co. Ltd. Yano
- 👤 Kazunori C/O Fuji Electric Co. Ltd. Oyabe
- 👤 Shoichi C/O Fuji Electric Co. Ltd. Furuhata
- 👤 Tetsuhiro C/O Fuji Electric Co. Ltd. Morimoto
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 13:44
CPC Classifications
H; H03; H03K; H03K17/00; H03K17/08; H03K17/082; H03K17/0822; H03F; H03F1/00; H03F1/52; H03K17/0828; H10; H10D; H10D89/00; H10D89/60
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
209 words
An over current protection device for protecting a main transistor (10; 11) having an insulated gate from an over current, comprsising; a current detector transistor (20; 21), connected in parallel with said main transistor (10; 11), having substantially the same structure as said main transistor (10; 11) and having its gate separated from the gate of said main transistor (10; 11); a current detecting means (Rd) for detecting the value of a current flowing through said current detector transistor (20; 21) and for outputting a detection signal indicative of said value; a gate control means (50) for controlling the gate potential of said main transistor (10; 11) and that of said current detector transistor (20; 21) when said detection signal exceeds a predetermined limit value such as to protect said main transistor (10; 11) from an over current; a main transistor gate circuit including means (Rg) for connecting said gate control means (50) with the gate of said main transistor (10; 11); and a detector transistor gate circuit including means for connecting said gate control means (50) with the gate of said current detector transistor (20; 21), the time constant of said detector transistor gate circuit being set shorter than the time constant of said main transistor gate circuit.
Claim 2
Dependent Claim
34 words
The device as claimed in claim 1, wherein said time constant of said detector transistor gate circuit is set to less than one tenth of the time constant of said main transistor gate circuit.
Claim 3
Dependent Claim
101 words
The device as claimed in claim 1 or 2, wherein said gate control means (50) comprises a comparator circuit (30) for comparing the value of said detection signal with a predetermined reference value and for outputting an output signal when the value of said detection signal exceeds said reference value, and a control circuit (40) for outputting, in response to said output signal, a control signal for controlling the gate potential of said main transistor (10; 11) and the gate potential of said current detector transistor (20; 21) such as to protect said main transistor (10; 11) from an over current.
Claim 4
Dependent Claim
62 words
The device as claimed in claim 1 or 2, wherein said gate control means (50) comprises a control transistor (51) having a predetermined operation threshold which is operated when a voltage value of said detection signal exceeds said threshold, thereby to control the gate potential of said main transistor (10; 11) and the gate potential of said current detector transistor (20; 21).
Claim 5
Dependent Claim
46 words
The device as claimed in claim 4, further comprising a circuit element (53), incorporated with said control transistor (51), for setting minimum gate control voltage values for said main transistor (10; 11) and said current detector transistor (20; 21) when said control transistor is in operation.
Claim 6
Independent Claim
94 words
The device as claimed in any one of the preceding claims, further comprising: a semiconductor base plate (60) into which said main transistor (10) and said current detector transistor (20) are built in side by side each having a channel portion in a surface portion of said base plate (60); and an insulation film (65) covering surface portions between said main transistor (10) and said current detector transistor (20); wherein at least one of the gates of said main transistor (10) and said current detector transistor (20) is extended to cover said insulation film.
Claim 7
Independent Claim
97 words
The device as claimed in in any one of the preceding claims, further comprising: a semiconductor base plate (60) into which said main transistor (10) and said current detector transistor (20; 21) are built in side by side each having a channel portion in a surface portion of said semiconductor base plate; and a stopper layer (64) of a conductivity type opposite to that of said semiconductor base plate, formed by in-diffusion from the surface of said semiconductor base plate between said channel portions of said main transistor (10; 11) and said current detector transistor (20; 21).
References Cited (Backward Citations)
No citation records indexed.
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