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EP0602708A2 Expired / Lapsed EP ⏱️ 0.0 years remaining

Control electrode disable circuit for power transistor

Assignee: Koninklijke Philips NV
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Filing: 1993-12-03
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Granted: —
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Expires: 2013-12-03
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Abstract

Abstract Power transistors used as high-side power switches are typically subjected to a variety of potentially destructive conditions, such as loss of bias current or loss of a ground connection in associated control circuitry. In order to protect the power transistor upon occurrence of such a potentially destructive condition, a control electrode disable circuit (12) is provided to ensure that the power transistor will be turned off upon the occurrence of such a condition, or when the control circuits are deliberately turned off or placed in a standby mode. Turn-off of the power transistor is ensured by shunting a disable transistor (112) across the input of the power transistor, and providing a disable circuit (114) for activating the disable transistor (112) in the event of loss of bias or loss of ground in the control circuitry. Reliable activation of the disable transistor (112) is ensured by a bootstrap capacitor circuit (140) in the disable circuit.

Inventors

  • 👤 Stephen C/O Int. Octrooibureau B.V. Wong

Bibliographic Details

Application Number —
Jurisdiction EP
Data Source google_patents
Last Synchronized 2026-11-06 08:52
CPC Classifications
H; H03; H03K; H03K19/00; H03K17/00; H03K17/08; H03K17/081; H03K17/0812; H03K17/08122; H03K17/06; H03K17/063

Claims Analysis

Total Claims: 4
Claim 1
Independent Claim 209 words
A control electrode disable circuit (12) for a power transistor (100) having a first main electrode coupled to a first power supply line (Vcc), a second main electrode coupled to a first terminal (104) of a load (102) which has a second terminal coupled to a second power supply line, and a control electrode (106), said control electrode disable circuit comprising: - a disable transistor (112) having a first main electrode coupled to said control electrode (106) of the power transistor (100), a second main electrode coupled to said first terminal (104) of the load (102), and a control electrode (D); and - circuit means (114) coupled to said second power supply line and responsive to at least one of a disable signal characterized in that the circuit means (114) is further responsive to an open circuit between said second power supply line and said disable circuit (12) for turning on said disable transistor (112), said circuit means (114) comprising a capacitor (140) having a first terminal (B) coupled to the control electrode (D) of said disable transistor (112) for generating a voltage at the control electrode (D) of said disable transistor (112) which is at least temporarily higher than a voltage on said first power supply line (Vcc).
Claim 2
Dependent Claim 24 words
A control electrode disable circuit as in Claim 1, wherein said capacitor (140) is connected in said circuit means (114) as a bootstrap capacitor.
Claim 3
Dependent Claim 111 words
A control electrode disable circuit as in Claim 2, further comprising first (124) and second (126) control transistors, a main electrode of said first control transistor (124) being coupled to a second terminal (A) of said bootstrap capacitor (140) for controlling a voltage on said second terminal (A) of the capacitor (140), a main electrode of said second control transistor (126) being coupled to the control electrode (D) of said disable transistor (112), and said first terminal (B) of the bootstrap capacitor (140) being coupled to said first power supply line (Vcc), said control electrode (D) of the disable transistor (112), and said main electrode of the second control transistor (126).
Claim 4
Dependent Claim 87 words
A control electrode disable circuit as in Claim 3, wherein said first terminal (B) of the bootstrap capacitor (140) is coupled to said first power supply line (Vcc) by a diode (138) connected with a polarity such that a voltage on said first terminal (B) of the bootstrap capacitor (140) can rise above said voltage on the first power supply line (Vcc), and said first terminal (B) of the bootstrap capacitor (140) is coupled to said main electrode of the second transistor (126) by a resistor (136).

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