Patent Publication Number: US-2023133107-A1

Title: Switch identification circuit and electric device

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of International Application No. PCT/CN2020/103039, filed on Jul. 20, 2020, which claims priority to Chinese Patent Application No. 202010605067.3, filed on Jun. 29, 2020, and claims priority to Chinese Patent Application No. 202021246478.X, filed on Jun. 29, 2020 the disclosures of which are hereby incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to the field of circuits, and particularly to a switch identification circuit and an electric device. 
     BACKGROUND 
     When a car is started, a power-supply device of the car outputs a power signal to a starter motor of the car, so that the starter motor can complete ignition to start the car. In this process, a switch identification circuit is required to identify a connection state of a load to ensure that a car engine can start stably and safely. 
     At present, most of the existing switch identification circuits determine whether the connection state of the load meets a starting requirement of the car by identifying an electrical signal of the load by means of a triode or an optocoupler identification detection circuit. However, the triode or the optocoupler identification detection circuit can pass charges when a minimum turn-on voltage is reached, which makes the switch identification circuit unable to identify a short-circuited state, resulting in relatively low car safety during car starting. 
     SUMMARY 
     Implementations of the disclosure provide a switch identification circuit. The switch identification circuit includes a detecting unit, a control unit, a connection unit, a first connection terminal, and a second connection terminal. The detecting unit is electrically coupled with the first connection terminal and the second connection terminal, and is configured to detect a voltage at the first connection terminal and a voltage at the second connection terminal to output a detection signal. The control unit is electrically coupled with the detecting unit and the connection unit, and is configured to receive the detection signal and determine whether the first connection terminal and the second connection terminal are short-circuited according to the detection signal, where a power-supply device is configured to supply a driving voltage to the first connection terminal and the second connection terminal. The control unit is configured to output a connection-enabling signal to the connection unit on condition that the first connection terminal and the second connection terminal are short-circuited, to make the connection unit control the power-supply device to stop supplying the driving voltage. 
     Implementations of the disclosure provide an electric device. The electric device includes a power-supply device, a load, and the above switch identification circuit. The power-supply device is electrically coupled with the load and configured to drive the load to start when the power-supply device and the load form a conductive loop. The switch identification circuit is electrically coupled with the power-supply device, and the switch identification circuit is configured to form a conductive loop comprising the power-supply device and the load when under action of the connection-enabling signal, the connection unit of the switch identification circuit controls the power-supply device to supply the driving voltage to the first connection terminal and the second connection terminal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to describe technical solutions of implementations of the disclosure more clearly, the following will give a brief description of accompanying drawings used for describing the implementations. Apparently, accompanying drawings described below are merely some implementations. Those of ordinary skill in the art can also obtain other accompanying drawings based on the accompanying drawings described below without creative efforts. 
         FIG.  1    is a schematic structural diagram illustrating a switch identification circuit according to implementations. 
         FIG.  2    is a schematic structural diagram illustrating a detailed circuit of an identification unit of the switch identification circuit illustrated in  FIG.  1    according to implementations. 
         FIG.  3    is a schematic structural diagram illustrating a detailed circuit of a second detecting unit of the switch identification circuit illustrated in  FIG.  1    according to implementations. 
         FIG.  4    is a schematic structural diagram illustrating a detailed circuit of a connection unit of the switch identification circuit illustrated in  FIG.  1    according to implementations. 
         FIG.  5    is a schematic structural diagram illustrating an electronic device according to implementations. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, technical solutions of implementations of the disclosure will be described in a clear and comprehensive manner with reference to accompanying drawings intended for the implementations. It is evident that the implementations described herein constitute merely some rather than all implementations of the disclosure, and that those of ordinary skill in the art will be able to derive other implementations based on these implementations without making creative efforts, which all such derived implementations shall all fall in the protection scope of the disclosure. 
     When a car is started, a battery of the car outputs a power signal to a starter motor of the car, so that the starter motor can complete ignition to start according to the power signal. If a battery failure or a failure of a connection between the battery and the starter motor occur, normal starting of the starter motor will be affected, which reduces safety of car starting. 
     To this end, it is necessary to detect the battery and the connection between the battery and the starter motor before the car is started, to improve the safety of the car during starting. 
     In implementations of the disclosure, a switch identification circuit is provided, which can detect the operation of a power-supply device (equipped with a battery) and a connection manner between the power-supply device and a load (equipped with a starter motor) before the car is started. As such, the load can be activated when the operation of the power-supply device and the connection between the power-supply device and the load meet a starting requirement. 
     In implementations of the disclosure, a switch identification circuit is provided. The switch identification circuit includes a detecting unit, a control unit, a connection unit, a first connection terminal, and a second connection terminal. The detecting unit is electrically coupled with the first connection terminal and the second connection terminal, and is configured to detect a voltage at the first connection terminal and a voltage at the second connection terminal to output a detection signal. The control unit is electrically coupled with the detecting unit and the connection unit, and is configured to receive the detection signal and determine whether the first connection terminal and the second connection terminal are short-circuited according to the detection signal, wherein a power-supply device is configured to supply a driving voltage to the first connection terminal and the second connection terminal. The control unit is configured to output a connection-enabling signal to the connection unit on condition that the first connection terminal and the second connection terminal are short-circuited, to make the connection unit control the power-supply device to stop supplying the driving voltage. 
     In implementations of the disclosure, an electric device is provided. The electric device includes a power-supply device, a load, and the above switch identification circuit. The power-supply device is electrically coupled with the load and configured to drive the load to start when the power-supply device and the load form a conductive loop. The switch identification circuit is electrically coupled with the power-supply device, and the switch identification circuit is configured to form a conductive loop comprising the power-supply device and the load when under action of the connection-enabling signal, the connection unit of the switch identification circuit controls the power-supply device to supply the driving voltage to the first connection terminal and the second connection terminal. 
     Compared to the related art, the switch identification circuit of the implementations of the disclosure can control the power-supply device to stop supplying the driving voltage to load when the first identification terminal and the second identification terminal are short-circuited directly or indirectly by detecting the voltage at the first connection terminal and the voltage at the second connection terminal. It can be seen that, compared to a detection method by means of a triode or an optocoupler identification detection circuit, the switch identification circuit of the disclosure can accurately identify whether the first connection terminal and the second connection terminal are short-circuited (i.e., a dangerous state). In this way, safety of the load coupled between the first connection terminal and the second connection terminal during starting of the load can be improved. 
       FIG.  1    is a schematic structural diagram illustrating a switch identification circuit according to implementations. As illustrated in  FIG.  1   , a switch identification circuit  100  includes a control unit  101 , an identification unit  102 , a battery unit  103 , a detecting unit  104 , and a connection unit  105 . 
     The control unit  101  is electrically coupled with the identification unit  102 . The control unit  101  is configured to output an identification-enabling signal to the identification unit  102 , to make the identification unit  102  enter an identification state under control of a first level of the identification-enabling signal, and to make the identification unit  102  exit the identification state under control of a second level of the identification-enabling signal. 
     The identification unit  102  is electrically coupled with a first connection terminal N 1  and a second connection terminal N 2 . The identification unit  102  is configured to receive a voltage at the first connection terminal N 1  as a first identification signal to transmit the first identification signal to the detecting unit  104 , and receive a voltage at the second connection terminal N 2  as a second identification signal to transmit the second identification signal to the detecting unit  104 . The first connection terminal N 1  is electrically coupled with positive poles of a power-supply device  200  and a load  300 , and the second connection terminal N 2  is electrically coupled with negative poles of the power-supply device  200  and the load  300 , where the power-supply device  200  is configured to drive the load  300  to start and operate. 
     The detecting unit  104  includes a first detecting unit  1041  and a second detecting unit  1042 . The first detecting unit  1041  is electrically coupled with the control unit  101 . The first detecting unit  1041  is configured to receive the first identification signal outputted by the identification unit  102 , and perform voltage division processing on the first identification signal to output a first detection signal to the control unit  101 . The voltage division process referred to herein means that the first identification signal is converted into the first detection signal that satisfies a voltage division relationship of the first detecting unit  1041 , where the voltage division relationship is determined by resistance values and a connection relationship of specified resistors of the first detecting unit  1041 . The second detecting unit  1042  is electrically coupled with the control unit  101 . The second detecting unit  1042  is configured to receive the second identification signal outputted by the identification unit  102 , and perform voltage division processing on the second identification signal to output a second detection signal to the control unit  101 . 
     The control unit  101  is configured to receive the first detection signal and the second detection signal, obtain a detection difference by performing a difference operation on the first detection signal and the second detection signal, and output a connection-enabling signal to the second detecting unit  1042  and the connection unit  105  after comparing the detection difference with a detection threshold. 
     In some implementations, the control unit  101  is further configured to calculate a value of the first identification signal according to a voltage division relationship between the first detection signal and the first identification signal. Similarly, a value of the second identification signal can be obtained. The control unit  101  is configured to perform a difference operation on the obtained first identification signal and the obtained second identification signal, assign a result of the difference operation as an identification difference, and output the connection-enabling signal to the second detecting unit  1042  and the connection unit  105  after comparing the identification difference with an identification threshold. 
     In implementations of the disclosure, if the detection difference is greater than the detection threshold, the control unit  101  is configured to output a second level of the identification-enabling signal, to make the identification unit  102  exit an identification state, and output a first level of the connection-enabling signal to the second detecting unit  1042  and the connection unit  105 , to make the second detecting unit  1042  enter a current detection state and make the connection unit  105  enter a turned-on state. 
     In implementations of the disclosure, if the detection difference is less than the detection threshold, the control unit  101  is configured to continue to output a first level of the identification-enabling signal, to make the identification unit  102  remain in the identification state, and output a second level of the connection-enabling signal to the second detecting unit  1042  and the connection unit  105 , to make the second detecting unit  1042  remain in a voltage detection state and make the connection unit  105  enter a turned-off state. 
     Specifically, if the detection difference is zero, a voltage at a first identification terminal S 1  is the same as a voltage at a second identification terminal S 2 , which means that the first identification terminal S 1  and the second identification terminal S 2  are short-circuited. In this case, the control unit  101  outputs the second level of the connection-enabling signal to the connection unit  105 , to make the connection unit  105  be in the turned-off state. If the detection difference is a negative value, the voltage at the first identification terminal S 1  is less than the voltage at the second identification terminal S 2 , which indicates that the first identification terminal S 1  is coupled with the second connection terminal N 2  and the second identification terminal S 2  is coupled with the first connection terminal N 1 . In this case, the control unit  101  outputs the second level of the connection-enabling signal to the connection unit  105 , to make the connection unit  105  be in the turned-off state. If the detection difference is a positive value and less than the detection threshold, which indicates that the power-supply device  200  is in a low-voltage state. In this case, the control unit  101  outputs the second level of the connection-enabling signal to the connection unit  105 , to make the connection unit  105  be in the turned-off state. 
     The connection unit  105  is electrically coupled with the control unit  101 . The connection unit  105  is configured to receive the connection-enabling signal outputted by the control unit  101 , and enter the turned-on state under action of the first level of the connection-enabling signal and enter the turned-off state under action of the second level of the connection-enabling signal. 
     The connection unit  105  is further electrically coupled with the power-supply device  200 . The connection unit  105  is configured to form a conductive loop including the power-supply device  200 , the load  300 , and the connection unit  105  when the connection unit  105  is in the turned-on state. In this case, the power-supply device  200  can output a power signal to the load  300  to realize starting of the load  300 . The connection unit  105  is further configured to disconnect the conductive loop including the power-supply device  200 , the load  300 , and the connection unit  105  when the connection unit  105  is in the turned-off state. In this way, the load  300  cannot be started. 
     The battery unit  103  is electrically coupled with the first connection terminal N 1 . The battery unit  103  is configured to maintain the voltage at the first connection terminal N 1 , such that a voltage difference between the first connection terminal N 1  and the second connection terminal N 2  is maintained when no power-supply device  200  is connected, to cooperate with the identification unit  102  to complete identification of the voltage at the first connection terminal N 1  and the voltage at the second connection terminal N 2  when the identification unit  102  in the identification state. 
     The connection unit  105  is further electrically coupled with the battery unit  103 . The connection unit  105  is configured to form a conductive loop including the battery unit  103 , the load  300 , and the connection unit  105  when the connection unit  105  is in the turned-on state and no power-supply device  200  is connected. In this case, the battery unit  103  can output a battery power to load  300  to start the load  300 . 
     The connection unit  105  is further electrically coupled with the second detecting unit  1042 . The connection unit  105  is configured to form a conductive loop including the power-supply device  200 , the load  300 , and the connection unit  105  to output a current signal to the second detecting unit  1042  in the case that the second detecting unit  1042  enters the current detection state and the connection unit  105  enters the turned-on state when the control unit  101  outputs the first level of the connection-enabling signal, and the second detecting unit  1042  is configured to output the current signal to the control unit  101 . 
     The control unit  101  is further configured to receive the current signal outputted by the second detecting unit  1042 , and adjust the connection-enabling signal (outputted to the second detecting unit  1042  and the connection unit  105 ) to the second level of the connection-enabling signal from the first level the connection-enabling signal after the current signal exceeds a current threshold. In this case, the connection unit  105  enters the turned-off state. As a result, the conductive loop including the power-supply device  200 , the load  300 , and the connection unit  105  is disconnected, and so the load  300  stops operating. 
     In implementations of the disclosure, the switch identification circuit  100  is configured to identify a state of the power-supply device  200  and a state of a connection between the power-supply device  200  and the load  300  (hereinafter, a connection state for short) through cooperation of the identification unit  102  and the battery unit  103 . When the state of the power-supply device  200  and the connection state meet a starting requirement, the control unit  101  is configured to output the first level of the connection-enabling signal to the connection unit  105  to make the connection unit  105  enter the turned-on state. In this case, the power-supply device  200  electrically coupled with the connection unit  105  can form a conductive loop with the load  300  and output a power signal to the load  300 , so as to start the load  300 . 
     In implementations of the disclosure, the state of the power-supply device  200  includes a standard-voltage state, a low-voltage state, and a missing state (i.e., a state where no power-supply device is connected). The connection state includes a positive-connection state, a reverse-connection state, and a short-circuited state. The starting requirement refers to that the connection state is the positive-connection state and the power-supply device  200  is in the standard-voltage state or the missing state. 
     In implementations of the disclosure, the control unit  101  may be a microcontroller unit (MCU), a field programmable gate array (FPGA), or other integrated circuits capable of controlling subsequent units, which is not limited in the disclosure. 
       FIG.  2    is a schematic structural diagram illustrating a detailed circuit of an identification unit of the switch identification circuit illustrated in  FIG.  1    according to implementations. As illustrated in  FIG.  2   , the identification unit  102  includes a first identification terminal S 1 , a second identification terminal S 2 , and a first transistor Q 1 . 
     The first identification terminal S 1  is electrically coupled with the first connection terminal N 1 . The second identification terminal S 2  is electrically coupled with the second connection terminal N 2 . The power-supply device  200  and the load  300  are coupled between the first connection terminal N 1  and the second connection terminal N 2 , where the power-supply device  200  is connected in parallel across the load  300 . p The first detecting unit  1041  is electrically coupled with the first identification terminal S 1 , and is configured to receive a voltage (signal) at the first identification terminal S 1  as the first identification signal. The second detecting unit  1042  is electrically coupled with the second identification terminal S 2 , and is configured to receive a voltage (signal) at the second identification terminal S 2  as the second identification signal. 
     The first identification terminal S 1  is further electrically coupled with the battery unit  103 , and is configured to receive an identification voltage signal outputted by the battery unit  103 , which allows existence of a level difference (also called as a voltage difference) between the first identification terminal S 1  and the second identification terminal S 2  when no power-supply device  200  is connected. 
     A first resistor R 1  is electrically coupled between the first identification terminal S 1  and the second identification terminal S 2 . The first resistor R 1  has a resistance value in a range of 100 and 200 kiloohms, and in this case, a current flowing through the first resistor R 1  is so small to be negligible, that is, regarded as an open circuit. 
     A drain of the first transistor Q 1  is electrically coupled with the second identification terminal S 2  via a second resistor R 2 , a source of the first transistor Q 1  is electrically coupled with the ground terminal GND, a gate of the first transistor Q 1  is electrically coupled with an identification-enabling signal output terminal of the control unit  101  (not illustrated) via a third resistor R 3 , and the gate of the first transistor Q 1  is further electrically coupled with the ground terminal GND via a fourth resistor R 4 . 
     A voltage value of the first level of the identification-enabling signal outputted by the control unit  101  is 5V for example, since the third resistor R 3  has a resistance value much smaller than a resistance value of the fourth resistor R 4 , a voltage value inputted to the gate of the first transistor Q 1  after being divided by the fourth resistor R 4  is slightly less than 5V, and accordingly, turning on of the first transistor Q 1  is not affected. In addition, since the gate of the first transistor Q 1  is electrically coupled with the ground terminal GND via the fourth resistor R 4 , residual charges at the gate of the first transistor Q 1  can be pulled down when the identification-enabling signal is switched to the second level of the identification-enabling signal from the first level the identification-enabling signal, which can increase the speed at which the first transistor Q 1  enters the turned-off state compared to natural depletion of the residual charges. 
     In implementations of the disclosure, the first transistor Q 1  is turned on under action of the first level of the identification-enabling signal outputted by the control unit  101 , and accordingly, the identification unit  102  enters the identification state. That is, after the first transistor Q 1  is turned on, a conductive loop including the first identification terminal S 1 , the second identification terminal S 2 , the second resistor R 2 , the turned-on first transistor Q 1 , and the ground terminal GND is formed, and accordingly, the first detecting unit  1041  and the second detecting unit  1042  can receive potential signals at the first identification terminal S 1  and the second identification terminal S 2 . Then the control unit  101  can determine, according to the potential signals, the state of the power-supply device  200  and a state of a connection between two identification terminals and two connection terminals. 
     In implementations of the disclosure, the state of the power-supply device  200  includes a standard-voltage state, a low-voltage state, and a missing state. The state of the connection between the two identification terminals and the two connection terminals includes a positive-connection state, a reverse-connection state, and a short-circuited state. 
     The positive-connection state herein refers to that the first identification terminal S 1  is coupled with the first connection terminal N 1 , and the second identification terminal S 2  is coupled with the second connection terminal N 2 . Furthermore, in the case that the power-supply device  200  is connected, whether a voltage value in the power-supply device  200  is a standard voltage or a low voltage can be determined according to a voltage difference between a voltage at the first identification terminal S 1  and a voltage at the second identification terminal S 2 . Specifically, if the voltage difference is lower than a voltage threshold, which indicates a positive-connection and low-voltage state. If the voltage difference is higher than the voltage threshold, which indicates a positive-connection and standard-voltage state. In the case that no power-supply device  200  is connected, the load  300  is equivalent to a resistor connected between the first identification terminal S 1  and the second identification terminal S 2 , and is used as a voltage dividing resistor together with the second resistor R 2 , which indicates a positive-connection state with power supply. In this case, under action of an identification voltage outputted by the battery unit  103 , the voltage difference between the voltage at the first identification terminal S 1  and the voltage at the second identification terminal S 2  can still meet a requirement of the control unit  101 , and so the connection unit  105  enters the turned-on state. 
     The reverse-connection state herein refers to that the first identification terminal S 1  is coupled with the second connection terminal N 2 , and the second identification terminal S 2  is coupled with the first connection terminal N 1 . In the case that the power-supply device  200  is connected, no matter if the power-supply device is in the standard-voltage state or the low-voltage state, the voltage at the second identification terminal S 2  is significantly greater than the voltage at the first identification terminal S 1 . In the case that no power-supply device  200  is connected, the load  300  is equivalent to a resistor connected between the first identification terminal S 1  and the second identification terminal S 2 , so that the voltage at the first identification terminal S 1  is the same as the voltage at the second identification terminal S 2 , which indicates a short-circuited state. 
     The short-circuited state herein refers to that the first identification terminal S 1  is directly connected to the second identification terminal S 2 , so that the voltage at the first identification terminal S 1  is the same as the voltage at the second identification terminal S 2 , which indicates another short-circuited state. 
     Based on the states of the power-supply device  200  and the states of the connection of the two identification terminals and the two connection terminals, the switch identification circuit  100  can detect, with the first detecting unit  1041 , the voltage at the first identification terminal S 1  and detect, with the second detecting unit  1042 , the voltage at the second identification terminal S 2 , to identify a short circuited state including a reverse-connection state without power supply and a short-circuited state, a failure state including a reverse-connection state with power supply and a positive-connection and low-voltage state, and a standard state including the positive-connection and standard-voltage state and a positive-connection state without power supply. In a case of the standard state, the control unit  101  controls the connection unit  105  to enter the turned-on state. 
       FIG.  3    is a schematic structural diagram illustrating a detailed circuit of a second detecting unit of the switch identification circuit illustrated in  FIG.  1    according to implementations. As illustrated in  FIG.  3   , the second detecting unit  1042  includes a first input terminal IN 1 , a first output terminal OUT 1 , a Zener diode D 1 , a capacitor Cl, and a second transistor Q 2 . 
     An anode of the zener diode D 1  is electrically coupled with the ground terminal GND. A cathode of the zener diode D 1  is electrically coupled with the first output terminal OUT 1 . The first output terminal OUT 1  is electrically coupled with a signal receiving terminal of the control unit  101 . The first output terminal OUT 1  is configured to output a first detection signal when the second detecting unit  1042  does not enter a current detection state, and is further configured to output a current signal when the second detecting unit  1042  enters the current detection state. 
     A fifth resistor R 5  is electrically coupled between a voltage dividing node A and the first output terminal OUT 1 . A sixth resistor R 6  is electrically coupled between the voltage dividing node A and the ground terminal GND. A seventh resistor R 7  is electrically coupled between the voltage dividing node A and the first input terminal IN 1 . The first input terminal IN 1  is electrically coupled with the identification unit  102  and the connection unit  105 , and is configured to receive a second identification signal and a current signal. 
     The capacitor C 1  is electrically coupled between the ground terminal GND and the first output terminal OUT 1 . 
     A source of the second transistor Q 2  is electrically coupled with the first input terminal IN 1 . A drain of the second transistor Q 2  is electrically coupled with the voltage dividing node A. A gate of the second transistor Q 2  is electrically coupled with a connection-enabling signal output terminal of the control unit  101  (not illustrated) via an eighth resistor R 8 . The gate of the second transistor Q 2  is further electrically coupled with the ground terminal GND via a ninth resistor R 9 . 
     In implementations of the disclosure, when the identification unit  102  is in the identification state under action of the first level of the identification-enabling signal outputted by the control unit  101 , the second transistor Q 2  is in the turned-off state due to receiving the second level of the connection-enabling signal outputted by the control unit  101 , that is, the second detecting unit  1042  is in the voltage detection state in this case. The first input terminal IN 1  receives the first identification signal outputted by the identification unit  102 , and the second detecting unit  1042  performs voltage division processing on the first identification signal to output the first detection signal to the control unit  101  via the first output terminal OUT 1 , where the voltage division relationship between the first identification signal and the first detection signal is determined based on the resistance values and the connection relationship of the fifth resistor R 5 , the sixth resistor R 6 , and the seventh resistor R 7 . Then the control unit  101  obtains the detection difference by performing the difference operation on the received first detection signal and the received second detection signal, and compares the detection difference with the detection threshold. In the case that the detection difference is greater than the detection threshold, the control unit  101  adjusts the connection-enabling signal (outputted to the gate of the second transistor Q 2  and the connection unit  105 ) to the first level from the second level, to make the connection unit  105  and the second transistor Q 2  of the second detecting unit  1042  be turned on. At this time, the identification unit  102  exits the identification state under action of the identification-enabling signal outputted by the control unit  101 , to stop outputting the first identification signal, and at this time, the first input terminal IN 1  receives the current signal outputted by the connection unit  105 . 
     In implementations of the disclosure, the first detecting unit  1041  has a circuit structure similar to the second detecting unit  1042 . Compared to the second detecting unit  1042 , the first detecting unit  1041  has no transistor with a same function as the second transistor Q 2  in the second detecting unit  1042  which is configured to switch between the voltage detection state and the current detection state, and accordingly, the first detecting unit  1041  can only output the second detection signal to the control unit  101  after performing voltage dividing processing on the received second identification signal. 
       FIG.  4    is a schematic structural diagram illustrating a detailed circuit of a connection unit of the switch identification circuit illustrated in  FIG.  1    according to implementations. As illustrated in  FIG.  4   , the connection unit  105  includes a first loop terminal J 1 , a second loop terminal J 2 , a second input terminal IN 2 , and multiple connection subunits. 
     The second input terminal IN 2  is electrically coupled with the control unit  101 . The second input terminal IN 2  is configured to receive a connection-enabling signal outputted by the control unit  101 , where the connection-enabling signal allows to control the multiple connection subunits of the connection unit  105  to be turned on or turned off. In the disclosure, the connection unit  105  is turned on when the multiple connection subunits are turned on, and the connection unit  105  is turned off when the multiple connection subunits are turned off. 
     The first loop terminal J 1  is electrically coupled with the battery unit  103 . The first loop terminal J 1  allows the battery unit  103  and the load  300  to form a conductive loop when the multiple connection subunits are in the turned-on state, so that the load  300  can receive a battery signal outputted by the battery unit  103  to start. 
     The second loop terminal J 2  is electrically coupled with the power-supply device  200 . The second loop terminal J 2  allows the power-supply device  200  and the load  300  to form a conductive loop when the multiple connection subunits are in the turned-on state, so that the load  300  can receive a power signal outputted by the power-supply device  200  to start. 
     Each of the multiple connection subunits is electrically coupled between the first loop terminal J 1  and the second loop terminal J 2 . 
     The multiple connection subunits have similar structures. Hereinafter, the structure of each connection subunit is described in detail, in which one of the connection subunits of the disclosure is taken as an example. 
     The connection subunit includes a third transistor Q 3  and a fourth transistor Q 4 . A gate of the third transistor Q 3  is electrically coupled with the second input terminal IN 2  via a twelfth resistor R 12 . A source of the third transistor Q 3  is electrically coupled with the first loop terminal J 1 . A drain of the third transistor Q 3  is electrically coupled with the ground terminal GND. A gate of the fourth transistor Q 4  is electrically coupled with the second input terminal IN 2  via a thirteenth resistor R 13 . A source of the fourth transistor Q 4  is electrically coupled with the second loop terminal J 2 . A drain of the fourth transistor Q 4  is electrically coupled with the ground terminal GND. 
     In implementations of the disclosure, the connection unit  105  includes three connection subunits. The three connection subunits operate in parallel, that is, if one of the three connection subunits is damaged, the other connection subunits can still operate. Moreover, the three connection subunits operating in parallel can improve a current transmission capability of the connection unit  105 . The number of the connection subunits of the connection unit  105  can be increased or decreased according to actual needs, which is not limited in the disclosure. 
     In implementations of the disclosure, both the battery unit  103  coupled with the first loop terminal J 1  and the power-supply device  200  coupled with the second loop terminal can be configured to start the load  300  when a conductive loop including the load  300  is formed. That is, in the disclosure, even if no power-supply device  200  including a battery device is connected in the car, the load  300  can be successfully started under action of the battery unit  103  of the switch identification circuit  100 . 
     In implementations of the disclosure, the connection unit  105  is switched between the turned-on state and the turned-off state under action of the connection-enabling signal inputted via the second input terminal IN 2 . Specifically, if the connection unit  105  receives the first level of the connection-enabling signal, transistors of the connection unit  105  are turned on, that is, the multiple connection subunits enter the turned-on state. Accordingly, a conductive loop is formed between the battery unit  103  electrically coupled with the first loop terminal J 1  and the load  300  and a conductive loop is formed between the power-supply device  200  electrically coupled with the second loop terminal J 2  and the load  300 , to start the load  300 . If the connection unit  105  receives the second level of the connection-enabling signal, the transistors of the connection unit  105  are turned off, that is, the multiple connection subunits enter the turned-off state. Accordingly, no conductive loop is formed between the battery unit  103  electrically coupled with the first loop terminal J 1  and the load  300 , and no conductive loop is formed between the power-supply device  200  electrically coupled with the second loop terminal J 2  and the load  300 . As a result, the load  300  stops operating. 
     Compared to the related art, the switch identification circuit  100  of the implementations of the disclosure can control the power-supply device  200  to stop supplying the driving voltage to load  300  when the first identification terminal S 1  and the second identification terminal S 2  are short-circuited directly or indirectly, by detecting the voltage at the first connection terminal N 1  and the voltage at the second connection terminal N 2 . It can be seen that, compared to a detection method by means of a triode or an optocoupler identification detection circuit, the switch identification circuit  100  of the disclosure can accurately identify whether the first connection terminal and the second connection terminal are short-circuited (i.e., a dangerous state). In this way, safety of the load  300  coupled between the first connection terminal and the second connection terminal during starting of the load can be improved. 
     In implementations of the disclosure, an electric device  1000  is provided. As illustrated in  FIG.  5   , the electric device  1000  includes a power-supply device  200 , a load  300 , and the foregoing switch identification circuit  100 . The power-supply device is electrically coupled with the load and configured to drive the load to start when the power-supply device and the load form a conductive loop. The switch identification circuit is electrically coupled with the power-supply device, and the switch identification circuit is configured to form a conductive loop comprising the power-supply device and the load when under action of the connection-enabling signal, the connection unit of the switch identification circuit controls the power-supply device to supply the driving voltage to the first connection terminal and the second connection terminal. 
     The switch identification circuit and the electric device of the implementations of the disclosure have been described in detail above. While the principles and implementations of the disclosure have been described in connection with illustrative implementations, it is to be understood that foregoing implementations are only used to help understand the method and core idea of the disclosure. As will occur to those skilled in the art, the disclosure is susceptible to various modifications and changes without departing from the spirit and principle of the disclosure. Therefore, the disclosure is not limited to the disclosed implementations.