Fultec Semiconductor, Inc.

Bourns Incorporated

Other

Richard A Harris

Francois Hebert

David J Perreault

Handoko Linewih

Arun K Chaudhuri

Roy Wallace White

Stephen S Coates

An electrical surge protection device () confers protection to an output node () from electrical surges on a data or power line () incident on an input node (). A transistorized surge protection device () is located in a current path between the input node () and the output node () and is configured to assume an isolating state in response to an over-current therethrough. A voltage-triggered protective circuit comprising a diac () in series with a bi-directional zener diode () is connected between the output side of the transistorized surge protection device () and a surge sinking node (). The voltage-triggered circuit assumes a low-impedance state in response to an electrical surge at output terminal. Consequently a surge current is passed through zener diode () and surge diac () to the surge sinking node. In response to the surge current the transistorized surge protection device () assumes a high impedance configuration thereby isolating output node () from input node (). Since neither the zener diode and diac combination, nor the transistorized surge protection device () are subject to sustained surge associated currents, embodiments of the invention can be compactly packaged.

Surge protection device

An apparatus and method for high-voltage transient blocking employing a transient blocking unit (TBU) that has at least one depletion mode n-channel device interconnected with at least one depletion mode p-channel device such that a transient alters a bias voltage Vof the p-channel device and a bias voltage Vof the n-channel device in concert. Specifically, the bias voltages are altered such that the p-channel device and n-channel device mutually switch off to block the transient. The depletion mode n-channel device employs a set of cascaded low-voltage depletion mode field effect transistors (FETs) such as metal-oxide-silicon field effect transistors (MOSFETs) connected source-to-drain to achieve the desired high-voltage operation of the TBU.

Apparatus and method for high-voltage transient blocking using low voltage elements

A method and apparatus for transient blocking relying on a transient blocking device and a sampling circuit. The transient blocking device has at least one depletion mode n-channel device interconnected with at least one depletion mode p-channel device such that a transient alters a bias voltage Vof the depletion mode p-channel device and a bias voltage Vof the depletion mode n-channel device in such a manner that the depletion mode devices mutually switch off to block the transient. The sampling circuit is interconnected with the depletion mode p-channel device and the depletion mode n-channel device to determine whether the transient persists. In the event of a persistent transient, the sampling circuit uses a disconnect element for permanently blocking the transient blocking device. Various types of voltage pinching and disconnect elements, including depletion mode devices of the n-channel and p-channel type can be employed in the sampling circuit to sample the transient and permanently block the transient blocking device.

Transient blocking apparatus with reset

A transient blocking unit (TBU) having reduced series impedance is provided. A TBU includes two or more depletion mode transistors arranged to provide a low series impedance in normal operation and a high series impedance when the input current exceeds a predetermined threshold. A nonlinear impedance element is included in the TBU that acts as a current limiter having a substantially constant saturation current over a range of applied voltages. This saturation current is selected to be the threshold current of the TBU. When the threshold is exceeded, the voltage developed across the nonlinear impedance element tends to drive the TBU into its high impedance state. When the operating current is below threshold, the TBU series resistance is relatively low because the nonlinear impedance element is in its low-resistance state. The nonlinear impedance element can be a separate circuit element, or it can be integrated with one or more of the TBU transistors.

Low resistance transient blocking unit

A protection apparatus () is provided which in addition to protecting electronic equipment () from overvoltage transients is also able to provide an indication of whether or not said transients are due to impedances associated with poor earthing. In one embodiment the protection apparatus () includes an input terminal (), an output terminal () and a ground reference terminal () with a transient blocking unit () arranged to isolate the output terminal () in response to the destructive transient voltages. A gas discharge tube () is provided to conduct transient currents associated with the destructive transient voltages to the earth reference connection point (); and an indicator (), such as a fuse or circuit breaker is placed in series with the transient blocking unit () to indicate the presence of a voltage resulting from an interaction of the transient currents with an earthing impedance.

Protection and indication apparatus

A protection system in which a shunt protection device at the interface terminals is optically triggered by sensor components within the circuit. This permits a variety of appropriate overvoltage detection thresholds to be defined at different nodes within the circuit. Preferably the shunt protection device is combined with one or more series protection devices which interrupt overcurrent.

Flexible secondary overcurrent protection

A differential mode surge protection apparatus includes first and second solid state protection devices in series between respective input and output connection points. The apparatus may be provided in conjunction with a common mode protection apparatus such as an isolation transformer. Alternatively, the apparatus may be provided integrated into a single miniaturized protection package. In a preferred embodiment, the apparatus includes a surge arrestor arranged to supplement protection conferred by the first and second solid state protection devices. The surge arrestor is capable of being triggered prior to breakdown of either the first or second solid state protection devices. The apparatus may be incorporated into digital processing cards such as LAN cards and also into cables to conveniently provide differential mode protection.

Protection devices and methods for preventing the flow of undesirable differential mode transients

An apparatus and method for temperature-dependent transient blocking employing a transient blocking unit (TBU) that uses at least one depletion mode n-channel device interconnected with at least one depletion mode p-channel device. The interconnection is performed such that a transient alters a bias voltage Vof the p-channel device and a bias voltage Vof the n-channel device in concert to effectuate their mutual switch off to block the transient. The apparatus has a temperature control unit that is in communication with the TBU and adjusts at least one of the bias voltages V, Vin response to a sensed temperature T, thereby enabling the apparatus to also respond to over-temperature. In some embodiments the p-channel device is replaced with a positive temperature coefficient thermistor (PTC). The temperature control unit can use any suitable circuit element, including, among other a PTC, resistor, negative temperature coefficient element, positive temperature coefficient element, transistor, diode.

Apparatus and method for temperature-dependent transient blocking

An apparatus and method for enhanced transient blocking employing a transient blocking unit (TBU) that uses at least one depletion mode n-channel device interconnected with at least one depletion mode p-channel device. The interconnection is performed such that a transient alters a bias voltage Vof the p-channel device and a bias voltage Vof the n-channel device such that the p- and n-channel devices mutually switch off to block the transient. The apparatus has an enhancer circuit for applying an enhancement bias to a gate terminal of at least one of the depletion mode n-channel devices of the TBU to reduce a total resistance Rof the apparatus. Alternatively, the apparatus has an enhancement mode NMOS transistor and a TBU connected thereto to help provide an enhancement bias to a gate terminal of the enhancement mode NMOS.

Apparatus and method for enhanced transient blocking

Merged devices for transient blocking. A pass transistor is placed so that its body potential drives the gate of a depletion-mode JFET-type blocking transistor. Thus a transient which appears on an external terminal is very rapidly propagated to shut off the blocking transistor, before large numbers of carriers can be injected. Preferably a shunt device is also used to drop high potentials which may appear at the same time. This connection can be particularly useful in power or data input terminals.

Integrated electronic disconnecting circuits, methods, and systems

A wire guide for EDM machining apparatus comprises a vacuum hot pressed titanium diboride block having a groove on a curved side of the block for positioning EDM wire. The block has a mounting hole therethrough lined with an electrically insulating sleeve.

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Palo Alto, CA, United States of America

Richard A Harris