Driver protection circuit for preventing damage due to line contact with ground or supply voltage
First Claim
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1. A protection circuit comprising:
- a supply terminal, an earth terminal, an input terminal which receives a voltage signal and an output terminal;
a first series transistor, a current-receiving electrode of which is linked to a node which receives a voltage substantially equal to the voltage of the input terminal;
a current-delivery electrode of the first series transistor coupled to the output terminal, and a second transistor for controlling the first series transistor;
wherein the second transistor is an amplifier, with a current-receiving electrode loaded by a top load element linked to the supply terminal, a current-delivery electrode loaded by a bottom load element linked to the earth terminal, and a control electrode receiving a voltage that is substantially equal to the voltage of the input terminal; and
a control electrode of the first series transistor linked to the second transistor on the top load element side, wherein the first series transistor conducts current between its current delivery electrode and current receiving electrode unless the voltage from its control electrode drops from excessive current from the output terminal.
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Abstract
This circuit is inserted between a terminal (RGB) and a line (LI). The signal of the input terminal (RGB) is applied to the base of a bipolar amplifier transistor (T2) mounted with a top load (LR1) and a bottom load (LR2). A series transistor (T1) mounted in series in the main signal path has its collector wired up as an electrode for receiving the input signal, its emitter feeds a line (LI), and its base is linked by a resistor to the collector of the second transistor.
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Citations
7 Claims
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1. A protection circuit comprising:
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a supply terminal, an earth terminal, an input terminal which receives a voltage signal and an output terminal;
a first series transistor, a current-receiving electrode of which is linked to a node which receives a voltage substantially equal to the voltage of the input terminal;
a current-delivery electrode of the first series transistor coupled to the output terminal, and a second transistor for controlling the first series transistor;
wherein the second transistor is an amplifier, with a current-receiving electrode loaded by a top load element linked to the supply terminal, a current-delivery electrode loaded by a bottom load element linked to the earth terminal, and a control electrode receiving a voltage that is substantially equal to the voltage of the input terminal; and
a control electrode of the first series transistor linked to the second transistor on the top load element side, wherein the first series transistor conducts current between its current delivery electrode and current receiving electrode unless the voltage from its control electrode drops from excessive current from the output terminal. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A protection circuit comprising:
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a supply terminal, an earth terminal, an input terminal which receives a voltage signal and an output terminal;
a first series transistor, a current-receiving electrode coupled to the input terminal;
a current-delivery electrode of the first series transistor coupled to the output terminal, and a second transistor for controlling the first series transistor;
wherein the second transistor is an amplifier, with a current-receiving electrode loaded by a top load element linked to the supply terminal, a current-delivery electrode, and a control electrode receiving a voltage that is substantially equal to the voltage of the input terminal; and
a control electrode of the first series transistor linked to the second transistor on the top load element side, wherein the first series transistor conducts current between its current delivery electrode and current receiving electrode unless the voltage from its control electrode drops from excessive current from the output terminal.
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Specification