Overload protection for D.C. circuits
First Claim
1. In a D.C. electrical distribution system comprising a D.C. power supply and a branch connected across said power supply, said branch comprising an electrical load, a switch, conductors, and an overload protector all serially connected, said switch being selectively operable to selectively control the current flow through the branch, said overload protector serving to sense overload associated with the flow of current in the branch and interrupt the current flow upon sensing overload to thereby protect the branch against overload, the improvement which comprises said switch and said overload protector being embodied in a solid state unit which comprises terminals via which it connects in the system, said unit comprising semiconductor structure which comprises a main controlled conduction path through the unit having a certain current/temperature rating and an associated overload protector for said main controlled conduction path responsive to incipient current or temperature exceeding said rating to protect said main controlled conduction path from potential damage, two of said terminals constituting external termination points for said main controlled conduction path via which said main controlled conduction path connects into the branch, at least one other of said terminals constituting an external termination point for connection to an input for selectively controlling the conductivity of said main controlled conduction path in accordance with said input thereby selectively controlling the conductivity of said main controlled conduction path to perform the switch function, said branch being free of separate overload protection devices external to said unit such that the current overload protection function within the branch is performed entirely by the protection of said main controlled conduction path within said unit by the associated overload protector.
3 Assignments
0 Petitions
Accused Products
Abstract
Protection for D.C. electrical circuit branches against incipient overloads comprises the use of semiconductor devices known as intelligent switches. An intelligent switch comprises a main controlled conduction path whose conductivity is controlled by an external control input. The semiconductor architecture is configured to possess internal self-protection for the main controlled conduction path against incipient current and/or temperature rises exceeding the device'"'"'s rating by rendering the main controlled conduction path non-conductive when such incipient conditions are sensed. The invention, recognizing that this internal self-protection attribute can be used also to provide protection for external circuit components connected to the switch in the branch, further comprises the elimination of external protective devices from the branch such that the intelligent switch itself provides the entire overload protection within the branch. The invention is especially beneficial in automotive electrical application, imparting improvements to particular specific circuits of automotive electrical systems.
75 Citations
24 Claims
- 1. In a D.C. electrical distribution system comprising a D.C. power supply and a branch connected across said power supply, said branch comprising an electrical load, a switch, conductors, and an overload protector all serially connected, said switch being selectively operable to selectively control the current flow through the branch, said overload protector serving to sense overload associated with the flow of current in the branch and interrupt the current flow upon sensing overload to thereby protect the branch against overload, the improvement which comprises said switch and said overload protector being embodied in a solid state unit which comprises terminals via which it connects in the system, said unit comprising semiconductor structure which comprises a main controlled conduction path through the unit having a certain current/temperature rating and an associated overload protector for said main controlled conduction path responsive to incipient current or temperature exceeding said rating to protect said main controlled conduction path from potential damage, two of said terminals constituting external termination points for said main controlled conduction path via which said main controlled conduction path connects into the branch, at least one other of said terminals constituting an external termination point for connection to an input for selectively controlling the conductivity of said main controlled conduction path in accordance with said input thereby selectively controlling the conductivity of said main controlled conduction path to perform the switch function, said branch being free of separate overload protection devices external to said unit such that the current overload protection function within the branch is performed entirely by the protection of said main controlled conduction path within said unit by the associated overload protector.
- 13. In a plural blower motor circuit which has a D.C. power supply, plural D.C. variable speed blower motors, and a control circuit for setting motor operation at plural speeds, the improvement which comprises each motor being in its own branch circuit across the power supply and in series with a corresponding semiconductor switch in its branch, each said semiconductor switch comprising a main controlled conduction path which has a certain current/temperature rating and through which current is conducted from said power supply to the corresponding motor and a control input which receives a control signal for controlling the conductivity of said main controlled conduction path between conductive and non-conductive conditions, each said semiconductor switch further comprising an associated internal overload protection means for protecting said main controlled conduction path against incipient current and thermal overloads exceeding the rating of said main controlled conduction path, each said branch being free of separate overload protection devices external to the corresponding switch such that the current overload protection function within each branch is performed entirely by the corresponding switch, said control circuit comprising a pulse width modulator circuit and a selectable control device coacting to provide said control signal to said control inputs as a pulse width modulated signal thereby imposing a duty cycle operation on said switches in accordance with the selection of said selectable control device and provide for motor speed operation at a speed less than full motor speed.
-
16. In an automotive vehicle stop lamp circuit in which a stop lamp performs stop, turn, and hazard warning signaling functions, said circuit being powered from a D.C. power supply of the vehicle, and a stop, turn and hazard warning switch means operates the stop lamp, the improvement which comprises a semiconductor switch connecting the stop lamp in a branch across the power supply, said semiconductor switch comprising a main controlled conduction path which has a certain current/temperature rating and through which current is conducted from said power supply to the stop lamp and a control input which receives a control signal for controlling the conductivity of said main controlled conduction path between conductive and non-conductive conditions, said semiconductor switch further comprising an associated internal overload protection means for protecting said main controlled conduction path against incipient current and thermal overloads exceeding the rating of said main controlled conduction path, said branch being free of separate overload protection devices external to the semiconductor switch such that the current overload protection function within the branch is performed entirely by the protection of said main controlled conduction path within said semiconductor switch by the associated internal overload protection means, said switch means comprises the combination of a combined turn signal/hazard warning switch and a stop lamp switch coacting to produce said control signal for causing a stop signal to be given by the stop lamp by rendering said semiconductor switch continuously conductive when the stop lamp switch is operated, for causing the stop lamp to give a turn signal by rendering said semiconductor switch intermittently conductive when said combined turn signal/hazard warning switch is operated for a turn signal, and for causing the stop lamp to give a hazard warning signal by rendering said semiconductor switch intermittently conductive when said combined turn signal/hazard switch is operated for a hazard warning signal.
- 17. In an automotive vehicle headlamp circuit comprising a headlamp load operable to high and low beam modes of operation, said circuit being powered from a D.C. power supply of the vehicle, and switch means for operating the headlamp load, the improvement which comprises plural semiconductor switches connecting the headlamp load in respective high and low beam branches across the power supply, one such switch in the high beam branch for operating the headlamp load to the high beam mode, another such switch in the low beam branch for operating the headlamp load to the low beam mode, each said semiconductor switch comprising a main controlled conduction path which has a certain current/temperature rating and through which current is conducted from said power supply to the headlamp load and a control input which receives a control signal for controlling the conductivity of said main controlled conduction path between conductive and non-conductive conditions, each said semiconductor switch further comprising an associated internal overload protection means for protecting its main controlled conduction path against incipient current and thermal overloads exceeding the rating of its main controlled conduction path, the path for current flow in each branch through the corresponding switch to the headlamp load being free of separate overload protection devices external to the corresponding switch such that the current overload protection function within the corresponding branch is performed entirely by the protection of the main controlled conduction path within the corresponding including the combination of a main headlight switch and a dimmer switch coacting to produce said control signal and selectively apply same to the control inputs of said semiconductor switches as selected by said dimmer switch to selectively produce high and low beam modes of operation for the headlamp load.
-
22. In an automotive vehicle headlamp circuit comprising a headlamp load operable to high and low beam modes of operation, said circuit being powered from a D.C. power supply of the vehicle, and switching means for operating the headlamp load, the improvement which comprises said switching means comprising plural switch means connecting the headlamp load in respective high and low beam branches across the power supply, one such switch means in the high beam branch for operating the headlamp load to the high beam mode, another such switch means in the low beam branch for operating the headlamp load to the low beam mode, each said switch means comprising a main controlled conduction path through which current is conducted from said power supply to the headlamp load and a control input which receives a control signal for controlling the conductivity of the switch means'"'"'main controlled conduction path, and including the combination of a main headlight switch and a dimmer switch coacting to produce said control signal and selectively apply same to the control inputs of said switch means as selected by said dimmer switch to selectively produce high and low beam modes of operation for the headlamp load, further including a further such switch means having a marker lamp laod to form a further branch across the power supply, said control input of said further such switch means being connected through a light interrupter switch to said headlight switch such that said marker lamp load is energized through said further switch means when said headlight switch is operated to cause the headlamp load to be illuminated and said interrupter switch remains closed, said interrupter switch being operable to cause the energization of the marker lamp load to be interrupted while the headlamp load remains illuminated.
-
23. In an automotive vehicle headlamp circuit comprising a headlamp load operable to high and low beam modes of operation, said circuit being powered from a D.C. power supply of the vehicle, and switching means for operating the headlamp load, the improvement which comprises said switching means comprising plural switch means connecting the headlamp load in respective high and low beam branches across the power supply, one such switch means in the high beam branch for operating the headlamp load to the high beam mode, another such switch means in the low beam branch for operating the headlamp load to the low beam mode, each said switch means comprising a main controlled conduction path through which current is conducted from said power supply to the headlamp load and a control input which receives a control signal for controlling the conductivity of the switch means'"'"'main controlled conduction path, and including the combination of a main headlight switch and a dimmer switch coacting to produce said control signal and selectively apply same to the control inputs of said switch means as selected by said dimmer switch to selectively produce high and low beam modes of operation for the headlamp load, including a taillamp load coupled via a further such switch means across the power supply to form a further branch, said headlight switch being coupled to the control input of said further switch means, said headlight switch comprising two output terminals coupled together through a diode, said two output terminals of said headlight switch being selectively connected to the power supply by the selective operation of said headlight switch to respective head and tail positions, said headlamp and said taillamp loads both being energized by operation of the associated switch means when the headlight switch is operated to the head position, and only said taillamp load, and not said headlamp load, being energized by operation of only said further switch means when the headlight switch is operated to the tail position.
-
24. In an automotive vehicle headlamp circuit comprising a headlamp load operable to high and low beam modes of operation, said circuit being powered from a D.C. power supply of the vehicle, and switching means for operating the headlamp load, the improvement which comprises said switching means comprising plural switch means connecting the headlamp load in respective high and low beam branches across the power supply, one such switch means in the high beam branch for operating the headlamp load to the high beam mode, another such switch means in the low beam branch for operating the headlamp load to the low beam mode, each said switch means comprising a main controlled conduction path through which current is conducted from said power supply to the headlamp load and a control input which receives a control signal for controlling the conductivity of the switch means'"'"'main controlled conduction path, and including the combination of a main headlight switch and a dimmer switch coacting to produce said control signal and selectively apply same to the control inputs of said switch means as selected by said dimmer switch to selectively produce high and low beam modes of operation for the headlamp load, including an instrument panel lamp load coupled via a further such switch means across the power supply to form a further branch, said headlight switch being coupled to the control input of said further switch means by a variable duty cycle timer circuit connected between the headlight switch and the control input of the further switch means including means for selecting the duty cycle of operation to be imposed by the variable duty cycle timer circuit on said further switch means to cause the intensity of illumination of the instrument panel lamp load to be selected to a level less than full intensity.
Specification