Patent Publication Number: US-2018040444-A1

Title: Smart switch system and controlling method for switch box

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a switch system and a controlling method, and especially relates to a smart switch system and a controlling method for a switch box. 
     Description of the Related Art 
     In the related art solar power generation system, usually the related art photovoltaic panel is connected to the related art inverter through the related art switch box, and then the related art inverter is connected to the power grid. The related art switch box is called the direct-current (DC) box as well. Engineers can perform the layout in the DC box. 
     In the normal condition, the related art switch box is turned on, so that the related art photovoltaic panel sends a direct-current voltage to the related art inverter through the related art switch box. But, in the abnormal condition (for examples, the arc is generated, the direct-current voltage is abnormal or the voltage of the power grid is abnormal), or in the condition that requires to cut off power (for example, other machines need to be installed), the related art switch box has to be turned off, so that the related art photovoltaic panel cannot send the direct-current voltage to the related art inverter. 
     For the related art switch box, the user has to turn off the switch in the related art switch box by hands to stop the related art photovoltaic panel sending the direct-current voltage to the related art inverter. It is very inconvenient. Although some of the related art switch boxes can turn on or turn off automatically, signal lines (for examples, RS-485, RS-232 and CANbus and so on) have to be arranged between the related art switch box and the related art inverter to transmit communication signals, so that the related art switch box is aware of the condition of the voltage of the power grid through the related art inverter, or the related art switch box is aware of the condition of the related art inverter to determine whether the related art switch box should be turned on or turned off. It is very inconvenient and wastes wires. 
     SUMMARY OF THE INVENTION 
     In order to solve the above-mentioned problems, an object of the present invention is to provide a smart switch system. 
     In order to solve the above-mentioned problems, another object of the present invention is to provide a controlling method for a switch box. 
     In order to achieve the object of the present invention mentioned above, the smart switch system is electrically connected to a direct-current voltage generation apparatus. The smart switch system includes a smart switch box. The smart switch box includes a switch box output side, an output-side voltage detection unit, a switch control unit, a switch unit and a switch box input side. The output-side voltage detection unit is electrically connected to the switch box output side. The switch control unit is electrically connected to the output-side voltage detection unit. The switch unit is electrically connected to the switch box output side, the output-side voltage detection unit and the switch control unit. The switch box input side is electrically connected to the switch unit. The output-side voltage detection unit detects a voltage of the switch box output side and informs the switch control unit of the voltage of the switch box output side. According to the voltage of the switch box output side, the switch control unit turns on or off the switch unit. When the switch control unit turns on the switch unit, an input voltage sent from the direct-current voltage generation apparatus is sent to the switch box output side through the switch box input side and the switch unit. 
     Moreover, in an embodiment of the smart switch system mentioned above, the switch box further comprises an input voltage detection unit electrically connected to the switch control unit, the switch box input side and the switch unit. The input voltage detection unit detects the input voltage and informs the switch control unit of the input voltage. 
     Moreover, in an embodiment of the smart switch system mentioned above, the switch control unit comprises an AND gate subunit electrically connected to the switch unit and the input voltage detection unit. 
     Moreover, in an embodiment of the smart switch system mentioned above, the switch control unit further comprises an OR gate subunit electrically connected to the AND gate subunit and the output-side voltage detection unit. 
     Moreover, in an embodiment of the smart switch system mentioned above, the smart switch system is electrically connected to a power grid. The smart switch system further comprises an electronic apparatus electrically connected to the smart switch box and the power grid. 
     Moreover, in an embodiment of the smart switch system mentioned above, the electronic apparatus comprises a power grid voltage detection unit electrically connected to the power grid. 
     Moreover, in an embodiment of the smart switch system mentioned above, the electronic apparatus further comprises a converter control unit electrically connected to the power grid voltage detection unit. 
     Moreover, in an embodiment of the smart switch system mentioned above, the electronic apparatus further comprises a direct-current-to-direct-current conversion unit electrically connected to the converter control unit and the smart switch box. 
     Moreover, in an embodiment of the smart switch system mentioned above, the direct-current-to-direct-current conversion unit comprises a pulse width modulation signal controller electrically connected to the converter control unit. 
     Moreover, in an embodiment of the smart switch system mentioned above, the direct-current-to-direct-current conversion unit further comprises a transistor switch electrically connected to the pulse width modulation signal controller. When the power grid voltage detection unit detects no voltage of the power grid, the power grid voltage detection unit informs the converter control unit, so that the converter control unit controls the pulse width modulation signal controller to control the transistor switch to be turned on (namely, to keep turning on), so that the voltage of the switch box output side approaches zero, so that the switch control unit turns off the switch unit. 
     Moreover, in an embodiment of the smart switch system mentioned above, the electronic apparatus comprises an auxiliary power unit and a diode. The auxiliary power unit is electrically connected to the power grid. The diode is electrically connected to the auxiliary power unit and the smart switch box. The auxiliary power unit receives a voltage of the power grid to generate a direct-current auxiliary voltage and then outputs the direct-current auxiliary voltage through the diode, so that the direct-current auxiliary voltage is detected by the output-side voltage detection unit, so that if the input voltage detection unit detects the input voltage (namely, the input voltage exists), the switch control unit turns on the switch unit. 
     Moreover, in an embodiment of the smart switch system mentioned above, the electronic apparatus comprises an auxiliary power unit, a first controllable disconnecting subunit and a second controllable disconnecting subunit. The auxiliary power unit is electrically connected to the power grid. The first controllable disconnecting subunit is electrically connected to the auxiliary power unit and the smart switch box. The second controllable disconnecting subunit is electrically connected to the auxiliary power unit and the smart switch box. The auxiliary power unit receives a voltage of the power grid to output a direct-current auxiliary voltage, so that the direct-current auxiliary voltage is detected by the output-side voltage detection unit, so that if the input voltage detection unit detects the input voltage (namely, the input voltage exists), the switch control unit turns on the switch unit. 
     Moreover, in an embodiment of the smart switch system mentioned above, the electronic apparatus comprises an alternating-current-to-direct-current conversion unit electrically connected to the smart switch box and the power grid. The alternating-current-to-direct-current conversion unit receives a voltage of the power grid to generate a direct-current voltage, so that the direct-current voltage is detected by the output-side voltage detection unit, so that if the input voltage detection unit detects the input voltage (namely, the input voltage exists), the switch control unit turns on the switch unit. 
     Moreover, in an embodiment of the smart switch system mentioned above, when the switch control unit receives a standalone mode signal and the input voltage detection unit detects the input voltage (namely, the input voltage exists), the switch control unit turns on the switch unit. 
     In order to achieve the other object of the present invention mentioned above, the controlling method is applied to the switch box. The switch box includes a switch box output side, an output-side voltage detection unit, a switch control unit, a switch unit and a switch box input side. The controlling method comprises following steps: The output-side voltage detection unit detects a voltage of the switch box output side and informs the switch control unit of the voltage of the switch box output side. According to the voltage of the switch box output side, the switch control unit turns on or off the switch unit. When the switch control unit turns on the switch unit, an input voltage sent from a direct-current voltage generation apparatus is sent to the switch box output side through the switch box input side and the switch unit. 
     Moreover, in an embodiment of the controlling method mentioned above, the switch box further comprises an input voltage detection unit. The input voltage detection unit detects the input voltage and informs the switch control unit of the input voltage. 
     Moreover, in an embodiment of the controlling method mentioned above, when the input voltage detection unit detects no the input voltage (namely, the input voltage does not exist), the switch control unit turns off the switch unit. 
     Moreover, in an embodiment of the controlling method mentioned above, the controlling method is applied to an electronic apparatus and a power grid. When the electronic apparatus detects a voltage of the power grid (namely, the voltage of the power grid exists), the electronic apparatus generates a voltage, so that the voltage generated by the electronic apparatus is detected by the output-side voltage detection unit. 
     Moreover, in an embodiment of the controlling method mentioned above, when the output-side voltage detection unit detects the voltage generated by the electronic apparatus (namely, the voltage generated by the electronic apparatus exists) and the input voltage detection unit detects the input voltage (namely, the input voltage exists), the switch control unit turns on the switch unit. 
     Moreover, in an embodiment of the controlling method mentioned above, when the switch control unit receives a standalone mode signal and the input voltage detection unit detects the input voltage (namely, the input voltage exists), the switch control unit turns on the switch unit. 
     The advantage of the present invention is that no signal wire is required between the switch box and the electronic apparatus. 
    
    
     
       BRIEF DESCRIPTION OF DRAWING 
         FIG. 1  shows a block diagram of an embodiment of the smart switch system of the present invention. 
         FIG. 2  shows a partial block diagram of an embodiment of the smart switch box of the present invention. 
         FIG. 3  shows a partial block diagram of an embodiment of the internal logic determination circuit of the switch control unit of the present invention. 
         FIG. 4  shows a partial block diagram of the first embodiment of the electronic apparatus of the present invention. 
         FIG. 5  shows a partial block diagram of the second embodiment of the electronic apparatus of the present invention. 
         FIG. 6  shows a partial block diagram of the third embodiment of the electronic apparatus of the present invention. 
         FIG. 7  shows a partial block diagram of the fourth embodiment of the electronic apparatus of the present invention. 
         FIG. 8  shows a block diagram of another embodiment of the smart switch system of the present invention. 
         FIG. 9  shows a block diagram of still another embodiment of the smart switch system of the present invention. 
         FIG. 10  shows a block diagram of still another embodiment of the smart switch system of the present invention. 
         FIG. 11  shows a block diagram of still another embodiment of the smart switch system of the present invention. 
         FIG. 12  shows a flow chart of the controlling method for a switch box of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Please refer to following detailed description and figures for the technical content of the present invention. The following detailed description and figures are referred for the present invention, but the present invention is not limited to it. 
       FIG. 1  shows a block diagram of an embodiment of the smart switch system of the present invention. A smart switch system  20  is electrically connected to a direct-current voltage generation apparatus  50  and a power grid  40 . The smart switch system  20  includes a smart switch box  10  and an electronic apparatus  30 . The electronic apparatus  30  is electrically connected to the smart switch box  10  and the power grid  40 . The direct-current voltage generation apparatus  50  is electrically connected to the smart switch box  10 . 
     The direct-current voltage generation apparatus  50  is, for example but not limited to, a photovoltaic panel. The electronic apparatus  30  is, for example but not limited to, a solar inverter. The power grid  40  is, for example but not limited to, one-phase, three-phase, isolated or non-isolated. Besides being applied to the solar power generation system, the present invention can be applied to the wind power generation system as well. 
     In the normal condition, the switch box  10  is turned on, so that the direct-current voltage generation apparatus  50  sends an input voltage  112  (for example, a direct-current voltage) to the electronic apparatus  30  through the switch box  10 . But in the abnormal condition (for examples, the arc is generated, the input voltage  112  is abnormal or a voltage of the power grid  40  is abnormal), the switch box  10  has to be turned off, so that the direct-current voltage generation apparatus  50  cannot send the input voltage  112  to the electronic apparatus  30 . The voltage of the power grid  40  is an alternating-current voltage. 
     For the related art switch box, the user has to turn off the switch in the related art switch box by hands to stop the direct-current voltage generation apparatus  50  sending the input voltage  112  to the electronic apparatus  30 . Some of the related art switch boxes can turn on or turn off automatically, but signal lines (for examples, RS-485, RS-232 and CANbus and so on) have to be arranged between the related art switch box and the electronic apparatus  30  to transmit communication signals. One of the technical features of the present invention is to change a voltage of a power line between the smart switch box  10  and the electronic apparatus  30  to control a switch in the smart switch box  10 , so that no signal wire is required. The content will be described in details as following: 
       FIG. 2  shows a partial block diagram of an embodiment of the smart switch box of the present invention. The smart switch box  10  includes a switch box output side  102 , an output-side voltage detection unit  104 , a switch control unit  106 , a switch unit  108 , a switch box input side  110 , an input voltage detection unit  114 , a power line  124  and a driving voltage supply unit  126 . The switch control unit  106  is, for example but not limited to, a microprocessor. The output-side voltage detection unit  104  and the input voltage detection unit  114  are, for example but not limited to, voltage-dividing resistor circuits or any voltage detection circuits which are known in the field. 
     The switch box output side  102  is electrically connected to the electronic apparatus  30 . The output-side voltage detection unit  104  is electrically connected to the switch box output side  102 . The switch control unit  106  is electrically connected to the output-side voltage detection unit  104 . The switch unit  108  is electrically connected to the switch box output side  102 , the output-side voltage detection unit  104  and the switch control unit  106 . The switch box input side  110  is electrically connected to the switch unit  108 . The input voltage detection unit  114  is electrically connected to the switch control unit  106 , the switch box input side  110  and the switch unit  108 . The power line  124  is electrically connected to the switch box output side  102 , the output-side voltage detection unit  104 , the switch unit  108  and the electronic apparatus  30 . The driving voltage supply unit  126  is electrically connected to the output-side voltage detection unit  104 , the switch control unit  106 , the switch unit  108 , the switch box input side  110 , the input voltage detection unit  114  and the direct-current voltage generation apparatus  50 . The driving voltage supply unit  126  utilizes the input voltage  112  to supply power to all of the internal components of the smart switch box  10 , such as the output-side voltage detection unit  104 , the switch control unit  106  and the input voltage detection unit  114 . 
     The output-side voltage detection unit  104  detects a voltage of the switch box output side  102  and informs the switch control unit  106  of the voltage of the switch box output side  102 . According to the voltage of the switch box output side  102  (and according to the status of the input voltage  112 , and other statuses, which will be described in details later), the switch control unit  106  turns on or off the switch unit  108  (will be described in details later). When the switch control unit  106  turns on the switch unit  108 , the input voltage  112  sent from the direct-current voltage generation apparatus  50  is sent to the switch box output side  102  through the switch box input side  110 , the switch unit  108  and the power line  124 , and then is sent to the electronic apparatus  30 . The input voltage detection unit  114  detects the input voltage  112  and informs the switch control unit  106  of the input voltage  112 . 
       FIG. 3  shows a partial block diagram of an embodiment of the internal logic determination circuit of the switch control unit of the present invention. The switch control unit  106  comprises an AND gate subunit  120  and an OR gate subunit  122 . The AND gate subunit  120  is electrically connected to the switch unit  108  and the input voltage detection unit  114 . The OR gate subunit  122  is electrically connected to the AND gate subunit  120  and the output-side voltage detection unit  104 . When the electronic apparatus  30  detects the voltage of the power grid  40  (namely, the voltage of the power grid  40  exists), the electronic apparatus  30  generates a voltage (will be described in details later), so that the output-side voltage detection unit  104  detects the voltage generated by the electronic apparatus  30 . People having ordinary skills in the field should be able to understand that the logic determination circuit can be achieved by any other circuits, such as the microcontroller unit (MCU), the complex programmable logic device (CPLD), the field-programmable gate array (FPGA) and so on. 
     According to  FIG. 3 , when the input voltage detection unit  114  detects no the input voltage  112  (namely, the input voltage  112  does not exist), the switch control unit  106  turns off the switch unit  108  (because of the AND gate subunit  120 ). When the output-side voltage detection unit  104  detects the voltage generated by the electronic apparatus  30  (namely, the voltage generated by the electronic apparatus  30  exists) and the input voltage detection unit  114  detects the input voltage  112  (namely, the input voltage  112  exists), the switch control unit  106  turns on the switch unit  108 . When the OR gate subunit  122  of the switch control unit  106  receives a standalone mode signal  116  (indicating that the system is in the standalone mode) and the input voltage detection unit  114  detects the input voltage  112  (namely, the input voltage  112  exists), the switch control unit  106  turns on the switch unit  108 . 
       FIG. 4  shows a partial block diagram of the first embodiment of the electronic apparatus of the present invention. The electronic apparatus  30  comprises a power grid voltage detection unit  302 , a converter control unit  304 , a direct-current-to-direct-current conversion unit  306  and a direct-current-to-alternating-current conversion unit  328 . The direct-current-to-direct-current conversion unit  306  comprises a pulse width modulation signal controller  308 , a transistor switch  310 , an inductor  324 , a first diode  314  and a capacitor  326 . The direct-current-to-direct-current conversion unit  306  is, for example but not limited to, a boost converter. 
     The power grid voltage detection unit  302  is electrically connected to the power grid  40 . The converter control unit  304  is electrically connected to the power grid voltage detection unit  302 . The direct-current-to-direct-current conversion unit  306  is electrically connected to the converter control unit  304  and the smart switch box  10 . The direct-current-to-alternating-current conversion unit  328  is electrically connected to the direct-current-to-direct-current conversion unit  306 , the power grid voltage detection unit  302  and the power grid  40 . The pulse width modulation signal controller  308  is electrically connected to the converter control unit  304 . The transistor switch  310  is electrically connected to the pulse width modulation signal controller  308 . The inductor  324  is electrically connected to the transistor switch  310  and the smart switch box  10 . The first diode  314  is electrically connected to the transistor switch  310  and the inductor  324 . The capacitor  326  is electrically connected to the first diode  314 . 
     When the power grid voltage detection unit  302  detects no voltage of the power grid  40  (namely, the voltage of the power grid  40  does not exist), the power grid voltage detection unit  302  informs the converter control unit  304 , so that the converter control unit  304  controls the pulse width modulation signal controller  308  to control the transistor switch  310  to be turned on (namely, to keep turning on), so that the voltage of the switch box output side  102  approaches zero (namely, the voltage of the switch box output side  102  is less than a predetermined voltage, wherein the predetermined voltage is equal to 0.1 voltage or 0.01 voltage but the present invention is not limited to it), so that the switch control unit  106  turns off the switch unit  108 . 
     If the direct-current voltage generation apparatus  50  is a solar panel, the voltage of the switch box output side  102  can approach zero by increasing a duty cycle of the transistor switch  310 , so that the switch control unit  106  turns off the switch unit  108 . This is the character of the voltage versus the current of the solar panel. The slope of the current is very even. Increasing the current will cause that the output voltage of the solar panel approaches zero. 
       FIG. 5  shows a partial block diagram of the second embodiment of the electronic apparatus of the present invention. The electronic apparatus  30  comprises an auxiliary power unit  312 , a third diode  31402 , a second diode  316 , a direct-current-to-direct-current conversion unit  306  and a direct-current-to-alternating-current conversion unit  328 . 
     The auxiliary power unit  312  is electrically connected to the power grid  40 . The third diode  31402  is electrically connected to the auxiliary power unit  312  and the smart switch box  10 . The second diode  316  is electrically connected to the auxiliary power unit  312  and the smart switch box  10 . The direct-current-to-direct-current conversion unit  306  is electrically connected to the third diode  31402 , the second diode  316  and the smart switch box  10 . The direct-current-to-alternating-current conversion unit  328  is electrically connected to the direct-current-to-direct-current conversion unit  306 , the auxiliary power unit  312  and the power grid  40 . The auxiliary power unit  312  can be one of the power supply circuits for the internal components of the electronic apparatus  30 . The auxiliary power unit  312  is, for example but not limited to, a bridge rectifier circuit or a flyback converter. 
     The auxiliary power unit  312  receives the voltage of the power grid  40  to generate a direct-current auxiliary voltage to supply to some internal components (for examples, the direct-current-to-direct-current conversion unit  306  and the direct-current-to-alternating-current conversion unit  328 ) of the electronic apparatus  30 , and outputs the direct-current auxiliary voltage through the diode  31402  and the second diode  316 , so that the direct-current auxiliary voltage is detected by the output-side voltage detection unit  104 , so that if the input voltage detection unit  114  detects the input voltage  112  (namely, input voltage  112  exists), the switch control unit  106  turns on the switch unit  108 . 
     Because the bias electrical characteristic of the diode, when the switch unit  108  is turned on, the input voltage  112  sent by the direct-current voltage generation apparatus  50  will not influence the direct-current auxiliary voltage of the auxiliary power unit  312 , so that the auxiliary power unit  312  can keep supplying the direct-current auxiliary voltage to the internal components of the electronic apparatus  30 . People having ordinary skills in the field should be able to understand that isolating the input voltage  112  and the direct-current auxiliary voltage can be achieved by using only one diode as well. 
       FIG. 6  shows a partial block diagram of the third embodiment of the electronic apparatus of the present invention. The electronic apparatus  30  comprises an auxiliary power unit  312 , a first controllable disconnecting subunit  318 , a second controllable disconnecting subunit  320 , a direct-current-to-direct-current conversion unit  306  and a direct-current-to-alternating-current conversion unit  328 . 
     The auxiliary power unit  312  is electrically connected to the power grid  40 . The first controllable disconnecting subunit  318  is electrically connected to the auxiliary power unit  312  and the smart switch box  10 . The second controllable disconnecting subunit  320  is electrically connected to the auxiliary power unit  312  and the smart switch box  10 . The direct-current-to-direct-current conversion unit  306  is electrically connected to the first controllable disconnecting subunit  318 , the second controllable disconnecting subunit  320  and the smart switch box  10 . The direct-current-to-alternating-current conversion unit  328  is electrically connected to the direct-current-to-direct-current conversion unit  306 , the auxiliary power unit  312  and the power grid  40 . The first controllable disconnecting subunit  318  is, for example but not limited to, an insulated gate bipolar transistor (IGBT) or a relay. The second controllable disconnecting subunit  320  is, for example but not limited to, an insulated gate bipolar transistor (IGBT) or a relay. The auxiliary power unit  312  can be one of the power supply circuits for the internal components of the electronic apparatus  30 . The auxiliary power unit  312  is, for example but not limited to, a bridge rectifier circuit or a flyback converter. 
     The auxiliary power unit  312  receives the voltage of the power grid  40  to turn on the first controllable disconnecting subunit  318  and the second controllable disconnecting subunit  320  to output a direct-current auxiliary voltage, so that the direct-current auxiliary voltage is detected by the output-side voltage detection unit  104 , so that the smart switch box  10  is aware of the existence of the voltage of the power grid  40 , so that if the input voltage detection unit  114  detects the input voltage  112  (namely, the input voltage  112  exists), the switch control unit  106  turns on the switch unit  108 . In this embodiment, before the switch control unit  106  turns on the switch unit  108 , the first controllable disconnecting subunit  318  and the second controllable disconnecting subunit  320  are turned off to avoid influencing the output voltage of the auxiliary power unit  312 . This is because the auxiliary power unit  312  supplies power to the internal components as well. 
       FIG. 7  shows a partial block diagram of the fourth embodiment of the electronic apparatus of the present invention. The electronic apparatus  30  comprises an alternating-current-to-direct-current conversion unit  322 , a direct-current-to-direct-current conversion unit  306  and a direct-current-to-alternating-current conversion unit  328 . 
     The alternating-current-to-direct-current conversion unit  322  is electrically connected to the smart switch box  10  and the power grid  40 . The direct-current-to-direct-current conversion unit  306  is electrically connected to the smart switch box  10  and the alternating-current-to-direct-current conversion unit  322 . The direct-current-to-alternating-current conversion unit  328  is electrically connected to the direct-current-to-direct-current conversion unit  306 , the alternating-current-to-direct-current conversion unit  322  and the power grid  40 . In this embodiment, the alternating-current-to-direct-current conversion unit  322  is an independent power converter which converts the alternating-current voltage of the power grid  40  into a direct-current voltage. 
     The alternating-current-to-direct-current conversion unit  322  receives the voltage of the power grid  40  to generate a direct-current voltage, so that the direct-current voltage is detected by the output-side voltage detection unit  104 . At this time, the direct-current voltage is on the power line  124 , so that the smart switch box  10  is aware of the existence of the voltage of the power grid  40 , so that if the input voltage detection unit  114  detects the input voltage  112  (namely, the input voltage  112  exists), the switch control unit  106  turns on the switch unit  108 . 
     In conclusion, if the standalone mode is not considered (discussed) first, the present invention can be divided into two parts: 
     The first part is that when the switch unit  108  is turned off: The output-side voltage detection unit  104  detects the voltage of the switch box output side  102 . At this time, because the switch unit  108  is turned off, the voltage of the switch box output side  102  is generated by  FIGS. 5, 6 and 7 . Each of the  FIGS. 5, 6 and 7  is to generate a voltage to inform the smart switch box  10  that the voltage of the power grid  40  is normal. 
     The second part is that when the switch unit  108  is turned on: Subsequently if the power grid  40  is abnormal, the switch unit  108  has to be turned off. At this time, the switch box output side  102  has the input voltage  112 , so that the transistor switch  310  keeps turning on to cause that the switch box output side  102  is short-circuited. The output-side voltage detection unit  104  can detect and inform the switch control unit  106  to turn off the switch unit  108 . 
     Moreover, for  FIG. 5 , if the third diode  31402  and the second diode  316  are removed from the electronic apparatus  30 , the remaining components of the electronic apparatus  30  form an inverter. In another word, in an embodiment, the smart switch box  10  and the electronic apparatus  30  do not require extra communication circuits. The smart switch box  10  can indirectly detect the voltage of the power grid  40  by the auxiliary power unit  312 , the third diode  31402  and the second diode  316 . 
     For  FIG. 6 , if the first controllable disconnecting subunit  318  and the second controllable disconnecting subunit  320  are removed from the electronic apparatus  30 , the remaining components of the electronic apparatus  30  form an inverter. In another word, the smart switch box  10  and the electronic apparatus  30  do not require extra communication circuits. The smart switch box  10  can indirectly detect the voltage of the power grid  40  by the auxiliary power unit  312 , the first controllable disconnecting subunit  318  and the second controllable disconnecting subunit  320 . 
     For  FIG. 7 , if the alternating-current-to-direct-current conversion unit  322  is removed from the electronic apparatus  30 , the remaining components of the electronic apparatus  30  form an inverter. In another word, the smart switch box  10  and the electronic apparatus  30  do not require extra communication circuits. The smart switch box  10  can indirectly detect the voltage of the power grid  40  by the alternating-current-to-direct-current conversion unit  322 . 
       FIG. 8  shows a block diagram of another embodiment of the smart switch system of the present invention. The description for the elements shown in  FIG. 8 , which are similar to those shown in  FIGS. 1 ˜ 7 , is not repeated here for brevity. Moreover, when the system is in the standalone mode (namely, receiving the standalone mode signal  116  mentioned above), even if there is no alternating-current voltage from the power grid  40 , if there is the direct-current voltage generated by the direct-current voltage generation apparatus  50 , a load apparatus  60  should be supplied power normally. 
       FIG. 9  shows a block diagram of still another embodiment of the smart switch system of the present invention. The description for the elements shown in  FIG. 9 , which are similar to those shown in  FIGS. 1 ˜ 8 , is not repeated here for brevity. Moreover, the positions of the smart switch box  10  and the electronic apparatus  30  can be exchanged. Namely, the smart switch box  10  can be applied to the alternating-current side for smart controlling, which is similar with the content mentioned above and is not repeated here for brevity. The present invention can be applied to both the direct-current side and the alternating-current side, which is similar with the content mentioned above and is not repeated here for brevity. 
       FIG. 10  shows a block diagram of still another embodiment of the smart switch system of the present invention. The description for the elements shown in  FIG. 10 , which are similar to those shown in  FIGS. 1 ˜ 9 , is not repeated here for brevity. Moreover, the smart switch system  20  further comprises a force interrupt unit  70  electrically connected to the smart switch box  10 . The force interrupt unit  70  is, for example but not limited to, a button used to turn off the smart switch box  10  forcedly, so that the direct-current voltage generation apparatus  50  cannot send the input voltage  112  to the electronic apparatus  30 . 
       FIG. 11  shows a block diagram of still another embodiment of the smart switch system of the present invention. The description for the elements shown in  FIG. 11 , which are similar to those shown in  FIGS. 1 ˜ 10 , is not repeated here for brevity. Moreover, the smart switch box  10  further comprises a high frequency signal receiving unit  804 . The electronic apparatus  30  further comprises a high frequency signal generating unit  806 . The high frequency signal receiving unit  804  comprises a frequency domain analysis subunit  810 . The high frequency signal generating unit  806  comprises a self-test circuit  812 . 
     The high frequency signal receiving unit  804  is electrically connected to the output-side voltage detection unit  104  and the switch unit  108  shown in  FIG. 2 . The high frequency signal generating unit  806  is electrically connected to the high frequency signal receiving unit  804 . The self-test circuit  812  is, for example but not limited to, an arc detection circuit. When an arc happens, a high frequency signal can be transmitted to turn off the switch unit  108 . 
     The electronic apparatus  30  determines whether the voltage of the power grid  40  exists or not. If the voltage of the power grid  40  exists, the electronic apparatus  30  utilizes the high frequency signal generating unit  806  to generate and transmit the high frequency signal to the high frequency signal receiving unit  804 . After the high frequency signal receiving unit  804  receives the high frequency signal, the high frequency signal receiving unit  804  sends a command to the logic determination circuit (shown in  FIG. 3 ) of the smart switch box  10 . Namely, as shown in  FIG. 2 , the output-side voltage detection unit  104  detects the voltage of the switch box output side  102  to inform the switch control unit  106 . 
       FIG. 12  shows a flow chart of the controlling method for a switch box of the present invention. A controlling method is applied to a switch box, an electronic apparatus and a power grid. The switch box includes a switch box output side, an output-side voltage detection unit, a switch control unit, a switch unit, a switch box input side and an input voltage detection unit. The controlling method comprises following steps: 
     S 02 : The output-side voltage detection unit detects a voltage of the switch box output side and informs the switch control unit of the voltage of the switch box output side. 
     S 04 : According to the voltage of the switch box output side, the switch control unit turns on or off the switch unit. 
     S 06 : When the switch control unit turns on the switch unit, an input voltage sent from a direct-current voltage generation apparatus is sent to the switch box output side through the switch box input side and the switch unit. 
     The input voltage detection unit detects the input voltage and informs the switch control unit of the input voltage. When the input voltage detection unit detects that there is no the input voltage (namely, the input voltage does not exist), the switch control unit turns off the switch unit. When the electronic apparatus detects a voltage of the power grid (namely, the voltage of the power grid exists), the electronic apparatus generates a voltage, so that the voltage generated by the electronic apparatus is detected by the output-side voltage detection unit. When the output-side voltage detection unit detects the voltage generated by the electronic apparatus (namely, the voltage generated by the electronic apparatus exists) and the input voltage detection unit detects the input voltage (namely, the input voltage exists), the switch control unit turns on the switch unit. When the switch control unit receives a standalone mode signal and the input voltage detection unit detects the input voltage (namely, the input voltage exists), the switch control unit turns on the switch unit. 
     The advantage of the present invention is that no signal wire is required between the switch box and the electronic apparatus. 
     Although the present invention has been described with reference to the preferred embodiment thereof, it will be understood that the invention is not limited to the details thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.