Field of invention
The present invention relates to protection of mechanical switch, particularly, the present invention relates to electronic circuit arrangement for protecting mechanical switch, more particularly, the present invention relates to electronic circuit arrangement which has load short, open and overload detection mechanism for protecting mechanical switch.
Background of the invention
Figure 1 shows a conventional circuit arrangement for driving a load utilizing high current switch. As shown in figure 1, in conventional circuit arrangement mechanical high current switches (SW) are protected by fuses (2). In situations of short to ground or overload, fuse (2) blows off and disconnects the power supply and the complete system fails. Till the replacement of the fuse (2) and fault correction, all corresponding loads (L) cannot be turned on. Further, in case of high current switches (SW), a spark is produced during contact-making which deteriorates performance of switches and other electronic components leading to reduced life and early failure of components and switches.
Figure 2 shows a circuit arrangement for driving a load utilizing low current switches (LSW). As shown in Figure 2, low current switches (LSW) are used with relay to drive the load (L). The relay is also protected by a fuse (2). In a situation of short to ground or overload, the fuse (2) blows off or relay may also fail which results in turning off of all corresponding loads (L) till replacement of fuse (2) or relay and fault correction.
Now-a-days micro-controller based electronic circuits are popular because by the incorporation of this circuit various functions/applications can be achieved. Figure 3 shows a conventional micro-controller (5) based electronic circuit for driving one or more loads with protective mechanism. Referring to figure 3, the protective mechanism of this conventional circuit utilizes one solid state switch (pSS) with detection mechanism (also known as PROFET) (pSS) per load. As shown in figure 3, the switching signal is given to the micro-controller (5) by low current switches (LSW1 and LSW2). The micro-
controller (5) then provides output signal to turn ON or OFF respective driver Solid State Switch depending on the switch inputs (LSW1, LSW2) and pre-defined logic. The detection mechanism of the Solid State Switch then provides a feedback about the state at the load side (i.e. short, open or overload condition). If there is some fault at load side i.e. load open condition or load short condition or over load condition, a feedback signal (analog or digital) is given to the micro-controller (5) by Solid State Switch using feedback pin and necessary action is performed by the micro-controller which may include shutting down the channel or power supply till correction of fault condition. In case of short/overload condition the controller shuts off the power supply to the load through the Solid State Switch thereby protecting the wire harness and load connecting thereto. Thus, the electronic circuit (as shown in figure 3) protects the system in case of short or overload condition.
Further, in the electronic circuit as shown figure 3, low current switches are used. The low current switches (LSW) are required to be made of special contact material for contact type switches or non-contact switching elements capable of carrying low current are required to be used. Therefore, the low current switches (LSW) are costly and require sealed coupler to give correct input to signal conditioning circuit (4) of controller. Also, as can be noticed from figure 3, in this conventional system one Solid State Switch is provided for each load. Therefore, even if two loads are connected at output which are to be driven alternatively (as in case of high beam and low beam function of head light module of automobile), two separate Solid State Switches must be used. Also, in the conventional system shown in figure 3, inputs from low current switches must be passed through signal conditioning circuit (4) so that it can be accepted by controller. Hence, the overall cost of this conventional system increases.
Objects of the Present Invention
The main object of the present invention is to provide a protected mechanical switch (1). Another object of the present invention is to provide an electronic circuit arrangement for protection of mechanical switches.
Still another object of the present invention is to provide an electronic circuit
arrangement having short load and/or open and/or overload detection mechanism for
protection of mechanical switches.
Yet another object of present invention is to provide an electronic circuit arrangement
with multiplexed input or feedback mechanism by eliminating input components, fuses,
relay and including intelligent control to mechanical switches.
A further object of present invention is to provide an electronic circuit arrangement for
protection of high current mechanical switches (SW) which increases contact life of high
current mechanical switches (SW) by avoiding spark caused during contact
making/breaking of mechanical contacts.
Another object of the present invention is to provide an electronic circuit arrangement for
protection of mechanical switches (SW) which is a cost effective intelligent protective
switching mechanism.
Summary of the invention:
The present invention provides an intelligent protective switch (1). An electronic circuit arrangement in series with high current mechanical switch (SW) arrangement and a load (L) which is connected to mechanical switch (SW), all together forms an intelligent protective switch (IPS). The whole arrangement of IPS is provided with multiplexed input/feedback mechanism by eliminating input components, fuses, relay and adding intelligent control to mechanical switches. A single Input/Feedback pin (I/Fb) used to sense switch activation /deactivation and load faults.
When mechanical switch (SW) is activated, presence of load (L) at the output is taken as input. Input/feedback pin (I/Fb) senses the mechanical switch (SW) activation. Corresponding input is used by controller chip (6) to switch respective solid state switch 'ON'.
If mechanical switch (SW) is deactivated by user, open load is sensed by IPS arrangement and similar input is given to controller chip (6) which turns solid state switch (SS) OFF till reactivation of mechanical switch (SW).
If mechanical switch (SW) is shorted to ground/vehicle chassis short circuit feedback is given to controller chip through Input/feedback pin (I/Fb). Input/feedback pin (I/Fb) senses the over load/short circuit reducing over of pin count of controller chip (6).
Brief description of drawings
Figure 1 shows a conventional circuit arrangement for driving a load utilizing high
current switch with conventional protective mechanism.
Figure 2 shows a circuit arrangement for driving a load utilizing low current switches
with conventional protective mechanism.
Figure 3 shows a conventional micro-controller based electronic circuit for driving one or
more loads with conventional protective mechanism.
Figure 4 shows an electronic circuit arrangement for the intelligent protected switch
system according to an embodiment of the present invention.
Figure 5 shows a flow chart for the intelligent protected switch system according to an
embodiment of the present invention.
Figure 6 shows an electronic circuit arrangement having one solid state switch and two
high current mechanical switches for two loads according to an embodiment of the
present invention.
Figure 7 illustrates an electronic circuit arrangement having one solid state switch and
one high current mechanical switch for two loads according to an embodiment of the
present invention.
Figure 8 shows an electronic circuit arrangement having number of solid state switch,
high current mechanical switches, and loads which are limited by application only
according to an embodiment of the present invention.
Referring number list:
1-Intelligent protected switch;
2-Fuse;
3-Battery;
4-Input signal conditioning circuit;
5-Microcontroller;
6-Controller chip;
ISW- Ignition switch;
SW- high current switch;
LSW- low current switch;
R- Relay;
I/P- input;
Fb- feedback;
pSS- solid state switch (PROFET)
SS- solid state switch (MOSFET);
ISS- input to solid state switch;
I/Fb- input feedback pin;
L- load.
Description of the present invention
Accordingly, the present invention provides an electrical system, comprising a power source; one or more switches for providing electrical connection between one or more electrical loads (L); a protection unit connected in series with the one or more switches (SW); wherein the protection unit is configured to detect the condition at the load (L) upon activation of the said one or more switches (SW); and to energize or de-energize the said one or more loads (L) based on the condition detected at the load (L).
In an embodiment of the present invention the said one or more switches (SW) are high current switches.
In another embodiment of the present invention the said one or more switches (SW) are contact type high current switches.
In still another embodiment of the present invention the protection unit comprises of a protective circuit and a control module coupled with the said one or more switches (SW).
In yet another embodiment of the present invention the protective circuit comprises of a controller (6) and a solid state switch (SS).
In a further embodiment of the present invention the control module is configured with controller (6).
In a further more embodiment of the present invention the protective circuit comprises low current path and high current path which consists signal conditioning circuit to sense switch and load condition.
In another embodiment of the present invention the control module comprises of low current detection path, high current activation path, which has unique sequence and detection means with precise timing.
In still another embodiment of the present invention the precise timing and sequence comprises of human realization about percentile on switch activation and deactivation wherein; at least 20% for switch debouncing/arching, and balance time for feedback and activation.
In yet another embodiment of the present invention the said control module is configured to provide a feedback signal to the controller (6) indicative of the condition at the load (L).
In a further embodiment of the present invention the controller (6) is configured to provide an output signal to the solid state switch (SS) for controlling the activation or de¬activation of the power circuit thereby energizing or de-energizing the load (L).
In a further more embodiment of the present invention the solid state switch (SS) is configured to resume the power supply from power source to the one or more loads via one or more switches (SW) upon activation of the power circuit.
In another embodiment of the present invention the solid state switch (SS) is configured to stop the power supply from power source to the one or more loads (L) via one or more switches (SW) upon de-activation of the power circuit.
Accordingly, the present invention provides a switch system which is intelligently protected and having load short/load open/overload detection mechanism. The intelligent protected switch (IPS) comprises a protection unit and a high current switch (SW) with unsealed coupler to which load (L) is connected in a series. The protection unit comprises a protective circuit and a control module. The protective circuit consist connection of controller CHIP (6) with solid state switch (SS) in series. The solid state switch (SW) comprises load short/open/overload detection mechanism via high current mechanical switch (SW). The said solid state switch (SW) being connected with the controller (6) to provide a feedback-input to the said controller (6) about the switch activation or switch de-activation and state of the load (L). The said controller (6) being configured to provide an input signal to the solid state switch (SS) to switch 'ON' or 'OFF' the said solid state switch (SS) based on predefined interlock/logic which in turn energize/de-energize load (L).
According to an embodiment of the present invention the solid state switch (SS) is a MOSFET.
Figure 4 shows an electronic circuit arrangement for the intelligent protected switch system according to an embodiment of the present invention. Referring to figure 4, controller (6) is connected in series with solid state switch (SS) and high current switch (SW). An input pin (ISS) and a feedback-input pin (I/Fb) are provided to transmit the input-signal and feedback-input signal between controller (6) and solid state switch (SSS). The controller (6) provides input to the solid state switch (SS) to turn the said solid state switch ON or OFF with predefined interlock/logic which in turn energize or de-energize load (L).
As can be observed from figure 4, the electronic circuit arrangement for the intelligent protected switch system is in series connection with high current switch (SW), with load (L) connected to high current switch (SW) to form an intelligent protected switch (IPS).
Figure 5 shows flow chart describing function of the intelligent protected switch system of the present invention.
Referring to figure 4 and 5, when the high current switch (SW) is activated presence of load (L) at the output is taken as input for the switch system. The feedback-input pin (I/Fb) acts as input pin for the switch system which senses the high current switch (SW) activation. Based upon the feedback input signal, an input signal is transmitted by the controller (6) to switch 'ON'/'OFF' the respective solid state switch (SS) with predefined interlocks / logic which in turn energize load (L).
If high current switch (SW) is deactivated by the user, open load is sensed by the feedback/input pin and similar input is given to controller (6) which turns OFF the solid state switch (SS) till reactivation of high current switch (SW).
In case, the high current switch (SW) is shorted to ground or vehicle chassis, a short-circuit feedback/input is given to the controller (6) through feedback-input pin (I/Fb) which senses over load/short circuit reducing overall pin count of controller chip (6).
In an embodiment of the present invention, the high current switch (SW) is protected against short circuit to ground i.e. in case high current switch (SW) is active and a short circuit happens, it is sensed by protection unit and the energy supply to corresponding load (L) is cutoff. After some interval 't', an auto retry is made to restore power supply/energy to load (L) in case of failure the cycle is repeated 'N' number of times after which load (L) is permanently de-energized till next reset cycle. Thus, battery is protected from deep discharges avoiding early failures and also wiring harness is protected from burning and which increases user safety.
In case of head lamp application of automobile, if head lamp switch is active, decision to turn ON the head lamp can be taken considering engine ON/OFF condition. In other words, if engine is 'ON', the head lamp can be activated and if engine turns 'OFF', the head lamp is turned 'OFF'. This spares battery for few more cranks.
If in any case high current switch (SW) is overloaded or shorted, it is sensed by corresponding feedback-input pin (I/Fb) of the controller (6) which turns OFF the solid state switch (SS) thereby protecting wiring harness and increasing safety for the user.
As can be clearly understood, in the present invention a single feedback-input pin (I/Fb) is used to sense/detect switch activation or deactivation and to detect load faults. Therefore, pin count on the controller chip (6) can be reduced. Also, the present invention eliminates the need of signal conditioning circuitry at the input of the controller thereby reducing overall system cost.
It can be clearly observed in the present invention, the solid state switch (SS) turn ON only after proper/complete switch contact is made and load (L) is sensed. Therefore, no arcs can be produced when the high current switch/ mechanical switch is turned ON. In the electronic circuit arrangement of the present invention thereby increase in life of mechanical switches (SW) can be achieved.
In case switching of blinkers (i.e. application as flasher), protection unit only turns ON after sensing switch Activation which reduces current consumption. Also, a predetermined time-out can be set using controller to provide features of Self cancellation. Further, double flashing can be provided in case of one of rare or front load failure and independent of battery voltage variations thus adding into users' safety. In an embodiment of the present invention, any suitable logic can be provided to the controller and not limited to any particular application. The same may vary from application to application.
In an embodiment of the present invention, more than one switch (SW) can be coupled with the single solid state switch (SS) driving more than one load. Referring to figure 6, the solid state switch (SS) connected to single high current switch (SW1) may be one or more than one and are only limited by solid state switch current. In the same arrangement, electronic circuit can be separate or miniaturized and integrated within high current mechanical switch to form the intelligent protected switch of the present invention.
Referring to figure 7, according to an embodiment of the present invention the electronic circuit arrangement can also have more than one loads connected to high current mechanical switch (SW) which can be driven alternately or parallel thus saving one additional solid state switch (SS) and high current mechanical switch (SW) arrangement pair.
Referring to figure 8, the electronic circuit arrangement of the present invention can have number of solid state switches (SS), high current mechanical switches (SW), and loads (L) which are limited by application only according to an embodiment of the invention. Mechanical switches (SW), electronic circuit may be integrated together or may be separate from each other. Also 'N' Number of solid state switches, high current switches (SW) can be clubbed together to form an intelligent controller module which derives its input from activation of high current/mechanical switches connected at output and in between load and intelligent electronic circuit. If none of the switch inputs are active in the output, condition can be sensed/detected and whole module can be put to sleep mode reducing power consumption. Thus, module formed with electronic circuit arrangement can be provided with supply from battery; thus, providing intelligent functions such as follow-me using mechanical switches. The electronic circuit arrangement of the present invention is not limited to high side drive and loads are not limited to resistive, capacitive or inductive loads also Input/Feedback pins are not limited to parallel interfaced and these pins can be multiplexed or can be used as one or more than one wire digital communication interface with controller chip (6).
Some of the features and advantages of the present invention are mentioned here below:
• The electronic circuit arrangement of the present invention includes multiplexed input/feedback-input mechanism to achieve intelligent switching with cost effective mechanism by eliminating input components, fuses, relay and adding intelligent control to mechanical switches.
• The electronic circuit arrangement of the present invention includes efficient/ multiplexed use of mechanical switches to drive loads thus reducing overall system cost.
• The electronic circuit arrangement of the present invention uses high current mechanical switches (with low cost unsealed coupler) instead of low Current special switches with sealed couplers to provide intelligent switching of loads.
• In the electronic circuit arrangement of the present invention, a single Input/feedback-input pin can be used to sense switch activation /deactivation and load faults.
• The electronic circuit arrangement of the present invention includes a mechanism to increase contact life of mechanical switches by avoiding spark caused during make of mechanical contact.
• If in any case mechanical switch is overloaded or shorted it is sensed by corresponding input/feedback input pin and Solid State Switch is turned OFF protecting wiring harness and increasing safety for the user.
• In case the electronic circuit arrangement of the present invention is used to drive Blinkers (Application as flasher) - the electronic circuit arrangement only turns ON after sensing switch activation thereby reducing current consumption. Also, a predetermined time out can be set using controller chip to provide Self cancellation function. Further, functions such as double flashing can be provided in case of one of rare or front load failure independent of battery voltage variations thus adding for users' safety. The logic of the controller chip is not limited with mechanical switch and can vary from application to application. This is not the case with conventional mechanical switches and flasher.
The present invention is described with reference to the figures and specific embodiments; this description is not meant to be construed in a limiting sense. Various alternate embodiments of the invention will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such alternative embodiments form part of the present invention.

We Claim:
1. A switch system (1), comprising:
a power source;
one or more switches (SW) for providing electrical connection between one or more
electrical loads (L);
a protection unit connected in series with the one or more switches (SW);
wherein the protection unit is configured
to detect the condition at the load (L) upon activation of the said one or more switches (SW); and
to energize or de-energize the said one or more loads (L) based on the condition detected at the load (L).
2. The switch system (1) as claimed in claim 1, wherein the said one or more switches (SW) are high current switches.
3. The switch system (1) as claimed in claim 1, wherein the said one or more switches (SW) are contact type high current switches.
4. The switch system (1) as claimed in claim 1, wherein the protection unit comprises a protective circuit and a control module coupled with the said one or more switches (SW).
5. The switch system (1) as claimed in claim 1, wherein the protective circuit comprises of a controller (6) and a solid state switch (SS).
6. The switch system (1) as claimed in claim 1, wherein the control module is configured with controller (6).
7. The switch system (1) as claimed in claim 4, wherein the protective circuit comprises low current path and high current path which consists signal conditioning circuit to sense switch and load condition.
8. The switch system (1) as claimed in claim 4, wherein the control module comprises of:
low current detection path, high current activation path which has unique sequence and detection means with precise timing.
9. The switch system (1) as claimed in claim 8, wherein the precise timing and sequence as
comprises of:
human realization about percentile on switch activation and deactivation wherein; at least 20% for switch debouncing/arching; and balance time for feedback and activation.
10. The switch system (1) as claimed in claim 5, wherein the solid state switch (SS)
comprises:
a power circuit
a control circuit for detecting the condition at the load upon activation of the
switch.
11. The switch system (1) as claimed in claim 10, wherein the said control circuit is configured to provide a feedback signal to the controller indicative of the condition at the load.
12. The switch system (1) as claimed in claim 11, wherein the controller is configured to provide an output signal to the solid state switch (SS) for controlling the activation or de¬activation of the power circuit thereby energizing or de-energizing the load.
13. The switch system (1) as claimed in claim 5, wherein the solid state switch (SS) is configured to resume the power supply from power source to the one or more loads (L) via one or more switches (SW) upon activation of the power circuit.
14. The switch system (1) as claimed in claim 5, wherein the solid state switch (SS) is configured to stop the power supply from power source to the one or more loads via one or more switches (SW) upon de-activation of the power circuit.