Patent Publication Number: US-2023155365-A1

Title: Over-current protection system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is filed under 35 U.S.C. §371 U.S. National Phase of International Application No. PCT/CN2021/085642 filed Apr. 6, 2021 (published as WO2021204110), which claims priority benefit to Chinese Application No. 202010268082.3 filed on Apr. 8, 2020, the disclosures of which are herein incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present invention generally relates to an over-current protection system for an electrical device connected in a circuit, more particularly, to an over-current protection system that connects and disconnects the electrical devices to and from the circuit during any abnormal conditions in the circuit. 
     BACKGROUND OF THE INVENTION 
     Generally, electrical devices are connected to a power source through a switching device to have controlled environment of the circuit. Sometimes, the circuit can experience with over-current flow due to short circuit or any other fault, which can damage the electrical devices and switching devices. To avoid such scenario, an over-current protection device is introduced to the circuit. The over-current protection device can disconnect the electrical devices from the circuit to avoid damages of the electrical devices while the circuit is experiencing over-current flow conditions thereon. The over-current protection device can include switching devices such as transistors to disconnect the electrical devices from the circuit experiencing over current. However, such over-current protection devices may not be efficient, since the switching devices in the device may not be stable. The switching devices may be unstable due to the electromagnetic interference of ground in the switching devices, which may affect the performance of the over-current protection devices. Therefore, such over-current protection devices may not efficiently disconnect the electrical devices from the circuit, so it may tend to damage the electrical devices. 
     Further, such over-current protection devices do not provide reset function, which reconnects the electrical devices to the circuit, once the over-current situation is restored without any external intervention. For example, the conventional over-current protection devices may disconnect the electrical devices from the circuit, when any over-current flows in the circuit due to any fault or short circuit, however, such devices do not reconnect the electrical devices back to the circuit, when the current flows in the circuit becomes normal again. Although the current flowing in the circuit reduces below a threshold level, the over-current protection devices do not reconnect the electrical devices back to the circuit. It requires an external intervention to reconnect the electrical devices back to the circuit, hence the conventional cover-current protection devices are not efficient to optimally operate the circuit. 
     Accordingly, there remains a need for an over-current protection device that effectively connects and disconnects any electrical devices to/from a circuit during normal and faulty conditions. Further, there remains a need for a device that can withstand any electromagnetic interferences. Further, there remains another need for a protection system that reset the circuit without any external intervention. 
     An object of the present invention is to provide a device connected in a circuit to have controlled environment in the circuit when the circuit is unstable. 
     Another object of the present invention is to provide an over-current protection device that disconnects an electrical device from a circuit when the current flowing in the circuit is more than of a threshold value, and reconnects the electrical device to the circuit when the current flowing in the circuit is less than of the threshold value. 
     Yet another object of the present invention is to provide an over-current protection system that protects electrical devices connected in a circuit when any abnormalities occurred in the circuit. 
     BRIEF SUMMARY OF THE INVENTION 
     In view of the foregoing, an embodiment of the invention herein provides an over-current protection system. The over-current protection system includes a sensing device, at least one comparator, at least one first transistor, and at least one second transistor. The sensing device is adapted to sense current flowing to an electrical device. The at least one comparator adapted to compare a signal received from the sensing device and a reference signal to generate any one of high signal and low signal, wherein the output of the at least one comparator is connected to a control device through. The at least one first transistor connected to the output signal of the at least one comparator to control the at least one first transistor, wherein the at least one first transistor is in a conductive state when the output signal of the at least one comparator is high signal. The at least one second transistor connected to and controlled by the at least one first transistor, wherein the at least one second transistor is in a conductive state when the at least one first transistor is in the conductive state. Further, the output of the comparator is grounded through the at least one second transistor when the at least one second transistor is in the conductive state. In one embodiment, the output of the at least one comparator is connected to the control device through the first resistor to reduce the current/voltage flowing to the control device, in order to protect the control device from high voltage/current than of operating voltage/current of the control device. The grounded output of the comparator can be a low signal. 
     Further, the over-current protection system includes a third transistor connected to the at least one first transistor and adapted to control the at least one first transistor, when the output signal of the at least one comparator is a low signal. 
     In one embodiment, a base terminal of the at least one first transistor is connected to both of the output of the at least one comparator through a second resistor and the collector terminal of the third transistor to control the at least one first transistor. 
     In another embodiment, a base terminal of the at least one second transistor is connected to a collector terminal of the at least one first transistor to control the at least one second transistor. 
     In one example, the first transistor and the third transistor are PNP type transistors and the second transistor is a NPN type transistor. 
     In one embodiment, the at least one comparator generates the high signal when the detected signal is less than of the reference signal, and the at least one comparator generates low signal when the detected signal is more than of the reference signal. 
     Further, the over-current protection system includes a voltage regulator connected to the third transistor to control the third transistor. 
     According to another aspect of the invention, a method for operating an over-current protection system is provided. The method in following steps. First, current flowing to an electrical device is detected and a signal is provided to an at least one comparator. The detected signal is compared with a reference signal by a comparator. Further, any one of high signal and low signal is generated based on the comparison between the detected signal and the reference signal, wherein the comparator generates low signal when the detected signal is more than of the reference signal. Thereafter, a first transistor and a second transistor is turned into a conductive state when the first transistor receives the low signal from the at least one comparator. Further, the output signal of the at least one comparator is grounded through the second transistor that restricts the output signal flow to a control device and turns the control device into a non-conductive state. Further, the electrical device is disconnected from a power source. 
     In one embodiment, a third transistor is turned into the first transistor and second transistor into a non-conductive state when the at least one comparator generates a high signal. Further, the high signal of the at least one comparator is provided to the control device to turn the control device in a conductive state, thereby connecting the electrical device to the power source. In one embodiment, the third transistor is controlled by a voltage regulator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other characteristics, details and advantages of the invention can be inferred from the description of the invention hereunder. A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying figures, wherein: 
         FIG.  1 A  illustrates a block diagram of an over-current protection system electrically connected in an electrical circuit, in accordance with an embodiment of the present invention; 
         FIG.  1 B  is a circuit diagram of the over-current protection system of  FIG.  1 A ; 
         FIG.  2    is a first flow diagram illustrating a method of operating the over-current protection system, in accordance with an embodiment of the present invention; and 
         FIG.  3    is a second flow diagram illustrating a method of operating the over-current protection system, in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     It must be noted that the figures disclose the invention in a detailed enough way to be implemented, the figures helping to better define the invention if needs be. The invention should however not be limited to the embodiment disclosed in the description. 
     The present invention relates to an over-current protection system provided in a circuit to control electrical devices connected in the circuit. For example, the circuit can connected to an electrical heater, and the over-current protection system is connected to the circuit to control the electrical heater. Forthcoming description of the over-current protection system in this document is explained with respect to the electrical heater, however, such over-current protection system can used to control any other electrical devices connected in a circuit. The over-current protection system can act as a switch to disconnect the electrical heater from the circuit, when the circuit is experiencing a current flow value above a threshold value, and reconnect the electrical heater back to the circuit, when the current flow in the circuit is restored to a value under the threshold value. Thereby, the over-current protection system provides protection to the electrical heater when the over-current flows in the circuit and increases safety of the circuit. Further, the over-current protection system provides a hassle-free controlling of the electrical heater during the circuit experiencing unstable conditions, such as over-current or short circuit. Further, the construction of the over-current protection system is simple and stable. 
       FIGS.  1 A and  1 B  illustrate different schematics of an over-current protection system  100 , in accordance with an embodiment of the present invention. The over-current protection system  100  can also be referred to as a protection device. The over-current protection system  100  is connected in a circuit  100 A to which an electrical heater  102  is electrically connected. The over-current protection system  100  can act as a controller that effectively controls a control device  110  to connect/disconnect the electrical heater  102  to/from the circuit  100 A. In one example,  FIG.  1 A  illustrates a block diagram of the over-current protection system  100  electrically connected in the electrical circuit  100 A having the electrical heater  102 , and  FIG.  1 B  is a circuit diagram of the over-current protection system  100 . The over-current protection system  100  can include at least one comparator  104 , a sensing device  106 , a plurality of first transistors  108 A, a plurality of second transistors  108 B, and a plurality of third transistors  108 C. In one example, the electrical circuit  100 A can include the over-current protection system  100 , the electrical heater  102 , and the control device  110 . In another example, the control device  110  can be a part of the over-current protection system  100 . Further, the electrical heater  102  is energized by a power source  112 . Ideally, the power source  112  can be a battery pack; however, it does not restrict to use any other power source with the electrical circuit  100 A. 
     Generally, the power source  112  is connected to the electrical heater  102  through the control device  110 . The control device  110  is to energize and de-energize the electrical heater  102 . In one embodiment, the control device  110  can be any control device, such as Metal Oxide Semiconductor Field Effect Transistor (MOSFET), Integrated Gate Bipolar Transistor (IGBT) etc. The control device  110  can be controlled by the over-current protection system  100  during any abnormality occurring in the electrical circuit  100 A. In one embodiment, a gate signal of the control device  110  is generated by the over-current protection system  100 , thereby effectively controlling the control device  110 . Further, the sensing device  106  can be a shunt or any other sensing device that can sense current flowing in the circuit  100 A. The sensing device  106  is provided in between the power source  112  and the electrical heater  102  and is adapted to measure current flowing in the circuit  100 A. Further, the sensing device  106  provides a signal to the comparator  104 , corresponding to the measured current in the circuit  100 A. The signal can indicate current level flowing in the circuit  100 A. The comparator  104  is adapted to compare the received signal from the sensing device  106  with a reference signal and accordingly generates a high or low signal. In one example, the comparator  104  generates the high output signal when the signal received from the sensing device  106  is less than of a reference threshold value. In other words, when the received signal from the sensing device  106  is less than of the reference value, the current flowing in the circuit  100 A is within the threshold value. 
     As mentioned above, the over-current protection system  100 , hereinafter referred to as protection system, includes at least three set of switches, such as the plurality of first transistors  108 A, the plurality of second transistors  108 B, and the plurality of third transistors  108 C. For the sake of brevity and clarity, forthcoming description in the document is explained with one first transistor, one second transistor and one third transistor. However, it does not restrict the invention to use more than one transistor. In one embodiment, the first transistor  108 A and the third transistor  108 C are PNP type transistor and the second transistor  108 B is a NPN type transistor. The output of the comparator  104  is connected to both the first transistor  108 A and the second transistor  108 B. In addition, the output of the comparator  104  can be connected to the gate terminal of the control device  110  through a first resistor  202 , to control the control device  110 . Generally, the output of the comparator  104  provides the gate signal to the control device  110  and causes the control device  110  to be in a conductive state, thereby energizing the electrical heater  102  by the power source  112 . Further, the control device  110  receives the gate signal when the comparator  104  generates the high signal, i.e., current flowing in the circuit  100 A is within the threshold value; otherwise, the output signal of the comparator  104  is grounded through the first transistor  108 A and the second transistor  108 B. In case the current flowing in the circuit  100 A is more than of the threshold value, the comparator  104  generates the low output signal and the second transistor  108 B grounds the low output signal, thereby disconnecting flow of the gate signal to the control device  110  in a locked manner. Hence, the electrical heater  102  stays disconnected from the circuit  100 A thereby avoiding damages to the electrical heater  102 . Generally, a low signal is a signal having zero voltage/current, and a high signal is a signal having the same voltage/current as the supply voltage/current. 
     Further, the first transistor  108 A is connected with both the third transistor  108 C and comparator  104 , in such a way that the comparator  104  or the third transistor  108 C can control the first transistor  108 A. In one embodiment, a base terminal of the first transistor  108 A is connected to both of the output of the comparator  104  through a second resistor  204  and a collector terminal of the third transistor  108 C. Hence, the first transistor  108 A can be controlled of either output of the comparator  104  or the third transistor  108 C. In one example, the first transistor  108 A is in a conductive state when the output signal of the comparator  104  is the low signal and the third transistor  108 C is in the non-conductive state. In another example, the first transistor  108 A is in a non-conductive state when the output signal of the comparator  104  is the high signal. Further, the first transistor  108 A is connected to the second transistor  108 B in such a way that the second transistor  108 B can be controlled by the first transistor  108 A. In one embodiment, the base terminal of the second transistor  108 B is connected to a collector terminal of the first transistor  108 A, so that the first transistor  108 A controls the second transistor  108 B. In one embodiment, the second transistor  108 B conducts when the first transistor  108 A is in the conductive state, since the base terminal of the second transistor  108 B is connected to the collector terminal of the first transistor  108 B. Further, the third transistor  108 C is connected to a reset module  114  to control the third transistor  108 C. In one embodiment, the reset module  114  is a low voltage controller that is connected to a base terminal of the third transistor  108 C, thereby controlling the third transistor  108 C. The protection system  100  further includes a pair of capacitors  116 A,  116 B, coupled respectively to the first transistor  108 A and the second transistor  108 B to improve electromagnetic compatibility to the ground. In one embodiment, the capacitor  116 A is connected in parallel to the emitter and base terminals of the first transistor  108 A and the capacitor  116 B is connected in parallel to the emitter and base terminals of the second transistor  108 B. 
     Referring to  FIG.  1 B , when current flowing in the circuit  100 A is within the threshold value, the comparator  104  receives low signal from the sensing device, generates the high output signal by comparing it with the reference signal. As the first transistor  108 A is PNP type transistor, the first transistor  108 A is in non-conductive state and the second transistor  108 B receives low or nil base signal. As the second transistor  108 B is a NPN type transistor, the second transistor  108 B is not conducting due to low base signal, thereby the output signal of the comparator  104  is provided to the control device  110  through the second resistor  204 . Hence, the circuit  100 A operates normally and the electrical heater  102  is energized by the power source  112 . 
     In case the current flowing in the circuit  100 A is more than of the threshold voltage, the comparator  104  receives the high signal from the sensing device  106 . The comparator  104  generates the low signal after comparing the high signal received from the sensing device  106  and the reference threshold signal. The low signal of the comparator  104  is provided to both the base terminal of the first transistor  108 A through the resistors  202 ,  206  and the collector terminal of the second transistor  108 B. As the first transistor  108 A is PNP type transistor, the low signal received at the base terminal of the first transistor  108 A enables the first transistor  108 A to be in the conductive state, so the reference signal flows to the second transistor  108 B through the first transistor  108 A. Further, a third resistor  210  is connected between the collector and base terminals of the first resistor  108 A and having more resistance value than of the second resistor  204 . Hence, the low signal from the comparator  104  flows through the second resistor  202  and reaches the base terminal of the first transistor  108 A, thereby the base of the first transistor  108 A is low, and in conductive state. Further, the reference signal is provided to the base terminal of the second transistor  108 B through the fourth resistor  208  to enable the second transistor  108 B. As the second transistor  108 B is in the conductive state, the output signal of the comparator  104  provided at the collector terminal of the second transistor  108 B is grounded through the second transistor  108 B. The grounded output signal of the comparator  104  can be a low signal. Further, a fifth resistor  212  is connected between the base terminal of the second transistor  108 B and the ground. The fifth transistor  212  has bigger resistance value than the fourth resistor  208 , therefore the base terminal of the second transistor  108 B receives the high reference signal flowing from the first transistor  108 A. The high base signal enables the second transistor  108 B to be in conductive state, thereby grounding the output signal of the comparator  104  received at the collector terminal of the second transistor  108 A. In one embodiment, the second transistor  108 B is in conductive mode and has lower resistance path than of the first resistor  202 . Hence, the output signal of the comparator  104  does not reach the gate terminal of the control device  110 , thereby causing the control device  110  to be in the non-conductive state. Therefore, the electrical heater  102  is disconnected from the power source  112  and avoids any damage to the circuit  100 A and the electrical heater  102  due to the over-current. 
     Once the current flowing in the circuit  100 A is restored to the level, which is within the threshold value, the protection system  100  reconnects the electrical heater  102  back to the circuit  100 A without any external physical intervention. To restore the circuit  100 A, the third transistor  108 C is provided in the protection system  100 . Although the current flowing in the circuit is less than of the threshold value, the comparator  104  still has the low output signal for some time, thereby maintaining the first transistor  108 A and the second transistor  108 B in the conductive state. To turn the first transistor  108 A and the second transistor  108 B, the third transistor  108 C is turned into the conducting state by the reset module  114 . In one embodiment, the reset module  114  includes a voltage regulator  117 . The voltage regulator  117  provides a low base signal to the base terminal of the third transistor  108 C, and maintains the third transistor  108 C in the conductive state. The third resistor  210  is short circuited, so the reference signal flows to the base terminal of the first transistor  108 A through the third transistor  108 C. Further, the base terminal of the first transistor  108 A is high, which turn the first transistor  108 A into the non-conductive state. As the first transistor  108 A is in non-conductive state, the base signal flow to the second transistor  108 B is disconnected, thereby turning the second transistor  108 B to the non-conductive state. Therefore, the output of the comparator  104  is not grounded anymore. Simultaneously, the output of the comparator  104  is changed to the high signal from the low signal, and provided to the high signal to the control device  110 . The control device  110  reconnects the electrical heater  102  back to the power source  112 , thereby ensuring that the circuit  110 A functions normally. In one embodiment, the third transistor  108 C can be NPN type transistor. In such case, the voltage regulator  114  generates a high signal to turn the third transistor  108 C into conductive state. 
       FIGS.  2  and  3    illustrate a method  300  of operating an over-current protection system  100 , in accordance with an embodiment of the present invention. Furthermore, the method  300  can be employed in any suitable hardware, switching devices, sensing devices or any combination thereof. For example, the method  300  can perform following steps to protect any electrical devices while over-current flows to the electrical devices. The method  300  is to be understood with reference to the details described along with  FIGS.  1 A and  1 B . 
     Method  300  begins at block  302 . At block  302 , the current flowing to the electrical device  102  is detected and a corresponding signal is provided to the comparator  104 . The sensing device  106  can determine the current flowing in the circuit  100 A. At block  304 , the signal received from the sensing device  106  is compared with a reference signal by the comparator  104 . At block  306 , any one of high or low signal is generated by the comparator  104  based on the comparison between the detected signal and the reference signal, the reference signal being a threshold value. The comparator  104  generates the low signal when the current flowing to the electrical device  102  is more than of the threshold value. As mentioned above, the threshold value is same value as of the reference signal. At block  308 , the first transistor  108 A and the second transistor  108 B are turned into conductive state when the first transistor  108 A receives the low signal from the comparator  104 . As the low signal is provided to the first transistor  108 A, the first transistor  108 A turns into the conductive state, thereby enabling the second transistor  108 B into the conductive state. At block  310 , the output low signal of the comparator  104  is grounded through the second transistor  108 B that restricts flow of output signal to a control device  110  and turns of the control device  110  into non-conductive state. As the control device  110  is in non-conductive state, the electrical device  102  is disconnected from the power source  112 , at block  312 , thereby protecting the electrical device  102  from damage when the over-current flowing to the electrical device  102 . 
     Referring to  FIG.  3   , the over-current protection system  100  reconnects or resets the electrical device  102  back to the power source  112 . Following blocks explain the method  300  for reconnecting the electrical device  102  to the power source  112 . At block  314 , the third transistor  108 C is turned into conductive state by a voltage regulator to turn the first transistor  108 A and the second transistor  108 B into the non-conductive state. Further, the third transistor  108 C is in conductive state when the output of the comparator  104  is the high signal. At block  316 , the high signal of the comparator  104  to the control device  110  to turn the control device  110  into the conductive state, thereby reconnecting the electrical device into the power source  112 , at block  318 . 
     Therefore, the over-current protection system  100  protects the electrical devices  102  connected in the circuit  100 A when the circuit  100 A is experiencing over-current conditions and resets the circuit  100 A when the circuit  100 A is restored with stable current, without any external intervention. 
     In any case, the invention cannot and should not be limited to the embodiments specifically described in this document, as other embodiments might exist. The invention shall spread to any equivalent means and any technically operating combination of means.