Patent Publication Number: US-11043837-B2

Title: Input power supply selection circuit

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to Chinese Patent Application No. 201810735303.6, filed on Jul. 5, 2018, the entire disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure relates to an integrated circuit field, and more particularly, to an input power supply selection circuit. 
     2. Description of the Related Art 
     A certain power supply system is provided with more than one input power supply for redundancy. An input power supply selection circuit coupled to the power supply system usually includes a plurality of relay switches, and selects one of input power supplies for the operation of the power supply system. When a selected input power supply is determined to be problematic, the sensing and control module switches the problematic input power supply to a normal one to maintain operation of the power supply system. 
     If the power supply selection circuit includes a capacitive load and the source voltages of input power supplies before and after switching are at different phases, an electric arc is usually generated with the switch being operated with power on. Overheating of the switch and a contact sticking may be caused, which may result in a malfunction of the switch. Therefore, it is necessary to set a relay switch in the input power supply selection circuit, however, this increases a size and cost of the input power supply selection circuit and a design complexity of the related circuit. 
     SUMMARY OF THE INVENTION 
     Preferred embodiments of the present disclosure ensure zero current switching of the input selection switches and prevent malfunction of switches due to over-rating the switch contacts during switching actions, which is caused by the switch being operated with power on in an input power supply selection circuit. 
     A preferred embodiment of the present disclosure provides an input power supply selection circuit including a load, at least one input power supply to provide an operation power supply for the load, the operation power supply being a DC (direct current) power supply or an AC (alternating current) power supply, an input selection circuit to select the at least one input power supply as the operation power supply for the load, and a sensing and control module to control the input selection circuit to switch the operation power supply for the load, the input power supply selection circuit further including a load switch branch to control the load to be connected or disconnected, and including a first end and a second end, wherein the first end is connected with the load, the second end is connected with an output end of the input selection circuit. The sensing and control module controls the load switch branch to be connected or disconnected, and when the load switch branch is disconnected, the load and the at least one input power supply are not electrically coupled. 
     In some preferred embodiments, the sensing and control module determines whether the operation power supply malfunctions by comparing the output voltage of the input selection circuit with a first voltage range. 
     In some preferred embodiments, if the output voltage of the input selection circuit does not fall within the first voltage range, the sensing and control module determines that the operation power supply for the load malfunctions, and controls the input selection circuit to conduct a power supply switching. 
     In some preferred embodiments, prior to controlling the faulty operation power supply to be disconnected, the sensing and control module controls the load switch branch to be disconnected, the sensing and control module controls the load switch branch to be disconnected prior to controlling the input selection circuit to couple with a new operation power supply, and the sensing and control module controls the load switch branch to be connected after controlling the input selection circuit coupled with the new operation power supply. 
     In some preferred embodiments, the sensing and control module determines whether the input selection circuit malfunctions by comparing a voltage of the operation power supply with the output voltage of the input selection circuit. 
     In some preferred embodiments, if a voltage difference between the voltage of the operation power supply and the output voltage of the input selection circuit is greater than a first threshold, the sensing and control module controls the load switch branch to be disconnected. 
     In some preferred embodiments, the load switch branch includes a load switch to control the load to be connected or disconnected. 
     In some preferred embodiments, the load switch branch includes a semiconductor switch branch connected in parallel with the load switch. 
     In some preferred embodiments, the semiconductor switch branch includes a first semiconductor switch and a second resistor connected in series, and a second semiconductor switch connected in parallel with the first semiconductor switch and the second resistor. 
     In some preferred embodiments, after switching the operation power supply, the sensing and control module controls the first semiconductor switch to be connected, when detecting that the difference between the output voltage of the input selecting circuit and the load voltage is less than a second threshold, the sensing and control module controls the second semiconductor switch and the load switch to be connected, and the first semiconductor switch and the second semiconductor switch to be disconnected sequentially. 
     In some preferred embodiments, the input selection circuit includes at least one set of input selection switches connected with the at least one input power supply and the load correspondingly, wherein each set of input selection switches includes at least one input selection switch. 
     In some preferred embodiments, the input selection circuit includes at least one single-pole double-throw switch, connected with the at least one input power supply and the load correspondingly. 
     In some preferred embodiments, the input selection circuit further includes at least one isolation switch connected with the at least one input power supply and the at least one single-pole double-throw switch correspondingly. 
     In some preferred embodiments, the load switch, each input selection switch, each single-pole double-throw switch, and each isolation switch are relay switches. 
     In some preferred embodiments, the input power supply selection circuit further includes a switching converter to perform a voltage conversion on an operation power supply, and including an input end and an output end, wherein the input end is connected with the sensing and control module, the load switch branch and the output end of the input selection circuit, and the output end is connected with both ends of the load, and an energy storage module to supply power to the load, prior to the switching action of the load switch branch, the sensing and control module controls the switching converter to change switching frequency and/or a duty ratio in the switching converter to reduce the operating power. 
     In some preferred embodiments, the load switch branch further includes an RC branch connected in parallel with the load switch, wherein the RC branch includes a first resistor and a first capacitor. 
     Each of the preferred embodiments of the present disclosure provide at least one of the following benefits. 
     In preferred embodiments of the present disclosure, the input power supply selection circuit includes a load switch branch to control the load to be connected or disconnected at an appropriate opportunity. According to the voltage of the at least one input power, the output voltage of the input selection circuit, and the load voltage, the sensing and control module controls the input selection circuit to switch the operation power supply for the load and controls the load switch branch to be connected or disconnected. Therefore, the input selection switches in the input selection circuit maintain a zero current state during the power switching, thus simplifying a contact protection design and reducing the switching capacity requirements. The hybrid design including semiconductors and mechanical relays in the load switch branch also greatly reduces the switching capacity requirements of the load switch. 
     Further, the sensing and control module determines whether the input selection circuit functions normally by comparing a voltage of the operation power supply with the output voltage of the input selection circuit to protect against electrical hazards. 
     The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1 - FIG. 12  schematically illustrate structural diagrams of an input power supply selection circuit according to preferred embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  schematically illustrates a structural diagram of an input power supply selection circuit according to a preferred embodiment of the present disclosure. The input power supply selection circuit includes a load  11 , at least one input power supply (P 11 -P 1 N), an input selection circuit  12 , a sensing and control module  13 , and a load switch branch  14 . 
     In some preferred embodiments, the at least one input power supply (P 11 -P 1 N) is configured to provide an operation power supply for the load  11  and the sensing and control module  13 , the input selection circuit  12  is configured to select one of the at least one input power supply (P 11 -P 1 N) as the operation power supply for the load, wherein the operation power supply is a DC (direct current) power supply or a AC (alternating current) power supply. The sensing and control module  13  is configured to control the input selection circuit  12  to switch the operation power for the load  11  according to voltages (VS 11 -VS 1 N) of the at least one input power supply, an output voltage V 12  of the input selection circuit, and a load voltage V 11 . The load switch branch  14  includes a first end and a second end, wherein the first end is connected with the load  11  and the second end is connected with an output end of the input selection circuit  12 . The load switch branch  14  is configured to control the load  11  to be connected or disconnected, the sensing and control module  13  is further configured to control the load switch branch  14  to be connected or disconnected, and when the load switch branch  14  is disconnected, the load  11  and the at least one input power supply (P 11 -P 1 N) are not electrically connected. 
     In some preferred embodiments, the input selection circuit  12  includes at least one set of input selection switches (S 11   a , S 11   b , . . . , S 1 Na, S 1 Nb) coupled with the at least one input power supply (P 11 -P 1 N) and the load  11  correspondingly, wherein each set of input selection switches includes at least one input selection switch. In  FIG. 1 , each set of input selection switches includes two input selection switches, wherein the input selection switches S 11   a , S 11   b  are connected with the input power supply P 11  correspondingly, the input selection switches S 12   a , S 12   b  are connected with the input power supply P 12  correspondingly, the input selection switches S 1 Na, S 1 Nb are connected with the input power supply P 1 N correspondingly. 
     In some preferred embodiments, the output end of input selection circuit  12  is connected with the load  11  through the load switch branch  14 . That is to say, one switch in each set of input select switches is connected with a first end of load  11  through the load switch branch  14 , and the other switch is connected with a second end of the load  11 . For example, the input selection switch S 11   a  is connected with the first end of the load switch branch  14 , and the input selection switch S 11   b  is connected with the second end of the load  11 . 
     In some preferred embodiments, the sensing and control module  13  receives at least one voltage (VS 11 -VS 1 N) of the at least one input power supply, the output voltage V 12  of the input selection circuit, and the load voltage V 11 , and send a control signal to the input selection circuit  12  and the load switch branch  14  to control the input selection circuit  12  to switch the operation power of the load  11  and to control the load switch branch  14  to be connected and disconnected. 
     In some preferred embodiments, the load switch branch  14  includes a load switch SL 1  that is configured to control the load  11  to be connected or disconnected. 
     In some preferred embodiments, the sensing and control module  13  determines whether the at least one input power supply (P 11 -P 1 N) malfunctions by receiving the output voltage V 12 . Specifically, the sensing and control module  13  determines whether the at least one input power supply (P 11 -P 1 N) is functions normally by comparing the output voltage V 12  of the input selection circuit  12  with a first voltage range. The first voltage range may be set according to actual conditions. In some preferred embodiments, the first voltage range may be about 100V to about 250V, for example. 
     In some preferred embodiments, if the output voltage V 12  of the input selection circuit  12  does not fall within the first voltage range, the sensing and control module  13  determines that the operation power supply of the load  11  malfunctions, and controls the input selection circuit  12  to conduct a power supply switching. Specifically, prior to controlling the faulty operation power supply to be disconnected, the sensing and control module  13  controls the load switch branch  14  to be disconnected, the sensing and control module  13  keeps the load switch branch  14  to be disconnected prior to controlling the input selection circuit  12  to couple with a new operation power supply prior to controlling the load switch branch  14  to be disconnected. And the sensing and control module  13  controls the load switch branch  14  to be connected after confirming the input selection circuit  12  to couple with the new operation power supply. 
     In some preferred embodiments, it is assumed that an input power supply P 1 K in the at least one input power supply is selected as the operation power supply of the load  11 , when the sensing and control module  13  determines that the input power P 1 K malfunctions, for example, when a voltage VS 1 K of the operation power supply exceeds the first voltage range, the sensing and control module  13  checks whether there is other faultless input power supply. If there are more than one faultless input power supplies, the sensing and control module  13  selects a faultless input power supply based on a predetermined rule to replace the faulty input power supply as a new operation power supply of the load  11 , for example, based on the predetermined rule, selects a faultless input power supply P 1 L to replace the faulty input power supply P 1 K as the operation power supply of the load  11 . 
     When a power supply switching is to be carried out, the sensing and control module  13  first turns off the load switch SL 1  in the load switch branch  14  to ensure that each input selection switch in the input selection circuit  12  is in a zero current state, and then detects the voltage difference between V 12  and V 11 ) at both sides of the load switch SL 1  to ensure whether the load switch SL 1  is completely disconnected. After the load switch SL 1  is completely disconnected, the sensing and control module  13  turns off the input selection switches S 1 Ka and S 1 Kb, to cut off the corresponding faulty input power supply P 1 K under a state of zero current, and compares a voltage difference (V 12 , VS 1 K) between both sides of the input selection switch S 1 Ka to ensure whether the input selection switches S 1 Ka and S 1 Kb are completely disconnected. Thereafter, the sensing and control module  13  turns on the input selection switches S 1 La and S 1 Lb such that a faultless input power supply P 1 L functions as the operation power of the load  11 , and compares a voltage difference between V 12  and VS 1 L to ensure that the input power P 1 L is connected properly with the circuit through the input selection switches S 1 La and S 1 Lb. Thereafter, the sensing and control module  13  turns on the load switch SL 11  to complete the power supply switching process. In the whole power supply switching process, the sensing and control module  13  continuously detects the voltages (VS 11 -VS 1 N) of the at least one input power supply, the output voltage V 12  of the input selection circuit, and the load voltage V 11  to ensure the power switching correctly. 
     The input selection switches maintain zero current state during the power supply switching, thus simplifying a contact protection design and switching capacity requirements of all the switches in the input selection circuit  12 . 
     In some preferred embodiments, the sensing and control module  13  determines whether the input selection circuit is functioning normally by comparing the voltage VS 1 K of the operation power supply with the output voltage V 12  of the input selection circuit. The sensing and control module  13  controls the load switch branch  14  to be disconnected if the difference between the voltage VS 1 K of the operation power supply and the output voltage V 12  of the input selection circuit is greater than a first threshold. In some preferred embodiments, the first threshold may be about 5V, for example. In some preferred embodiments, if some switches in the input selection circuit  12  are malfunctioning, causing two live wires of different power supplies to be connected with the load  11  at a same time, a large voltage is generated, which may lead to a serious consequence. In the present preferred embodiment, when a malfunction occurs (i.e., the difference between the operation power supply voltage VS 1 K and the output voltage V 12  of the input selection circuit is greater than the first threshold), the load switch branch  14  is first disconnected to avoid damage to the circuit. 
       FIG. 2  schematically illustrates a structural diagram of an input power supply selection circuit according to a preferred embodiment of the present disclosure. The input power supply selection circuit includes a load  21 , at least one input power supply (P 21 , P 22 , . . . , or P 2 N), an input selection circuit  22 , a sensing and control module  23 , and a load switch branch  24 . 
     In some preferred embodiments, the input selection circuit  22  includes at least one set of input selection switches (S 21   a , S 21   b , . . . , S 1 Na, S 1 Nb) that are correspondingly connected with the at least one input power supply (P 21 -P 2 N) and the load  21 . The load switch branch  24  includes a load switch SL 2 . 
     Compared with  FIG. 1 , the input power supply selection circuit shown in  FIG. 2  differs mainly in that the load switch branch  24  further includes a semiconductor switch branch, which is connected in parallel with the load switch SL 2  to further reduce a switching stress of the load switch SL 2 . The semiconductor switch branch includes a first semiconductor switch ss 21  and a second resistor R 22  connected in series, and a second semiconductor switch ss 22  connected in parallel with the first semiconductor switch ss 21  and the second resistor R 22  in series. In some preferred embodiments, the semiconductor switch can be a Triode AC semiconductor switch (TRIAC), a MOS transistor, a transistor, a thyristor, an insulated gate bipolar transistor or a combination thereof. The remaining devices in the input power supply selection circuit shown in  FIG. 2  are similar to the corresponding devices in the input power supply selection circuit shown in  FIG. 1 , which are not described in detail herein. 
     In some preferred embodiments, a process that the sensing and control module  23  conducting the power supply switching is similar to the process that the sensing and control module  13  conducting the power supply switching in  FIG. 1 , except for the connection step of the first semiconductor switch ss 21 . After the input selection switches in the input selection circuit  22  completes the corresponding switching operation (i.e., a faulty power supply is disconnected and a new faultless power supply is connected) in the zero current state, if the load switch SL 2  is directly turned on, the circuit may generate high surge current when the load  21  is a capacitive device and V 22  and V 21  are at a high voltage difference, which may affect the circuit safety and reliability. Therefore, in some preferred embodiments, after the input selection switch completes the corresponding switching operation, the sensing and control module  23  turns on the first semiconductor switch ss 21 , so that the faultless input power supply P 2 L can apply a voltage to the load  21 . The second resistor R 22  in series with the first semiconductor switch ss 21  can limit the current generated when the first semiconductor switch ss 21  turns on to an acceptable range. 
     After the first semiconductor switch ss 21  is turned on, if it is detected that a difference between the output voltage V 22  of the input selection circuit and a load voltage V 21  is less than a second threshold, the sensing and control module  23  turns on the second semiconductor switch ss 22  and the load switch SL 2 . In some preferred embodiments, the second threshold may be about 5V, for example. In some preferred embodiments, a connection speed of the second semiconductor switch ss 22  is faster than a connection speed of the load switch SL 2 , so that the second semiconductor switch ss 22  is turned on before the load switch SL 2  is turned on, and a voltage drop of load switch SL 2  is kept at a low level. When the load  21  is a capacitive device, a switching stress of the load switch SL 2  is able to be greatly reduced. After that, the sensing and control module  23  turns off the first semiconductor switch ss 21  and the second semiconductor switch ss 22  sequentially. 
       FIG. 3  schematically illustrates a structural diagram of an input power supply selection circuit according to a preferred embodiment of the present disclosure. The input power supply selection circuit includes a load  31 , two input power supplies P 31 , P 32 , an input selection circuit  32 , a sensing and control module  33 , and a load switch branch  34 . The load switch branch  34  includes a load switch SL 3 . 
     In some preferred embodiments, the input selection circuit  32  can include a first single-pole double-throw switch S 31  and a second single-pole double-throw switch S 32 . The first single-pole double-throw switch S 31  includes a first moving end connected with the input power supply P 31 , a second moving end connected with the input power supply P 32 , and a fixed end connected with the load switch SL 3 . The second single-pole double-throw switch S 32  includes a first moving end connected with the input power supply P 31 , a second moving end connected with the input power supply P 32 , and a fixed end connected with the load  31 . The remaining devices in the input power supply selection circuit shown in  FIG. 3  are similar to the corresponding devices in the input power supply selection circuit shown in  FIG. 1 , which are not described in detail herein. 
     The adoption of the single-pole double-throw switch in the input selection circuit  32  instead of the input selection switch shown in  FIG. 1  has the following advantages reduces the number of switches in the circuit. In the case where the number of input power supplies is 2, the input power supply selection circuit shown in  FIG. 1  requires 4 input selection switches, while the input power supply selection circuit shown in  FIG. 3  requires only 2 single-pole double-throw switches. Also, the single-pole double-throw switch structure avoids a short connection of the input power supply when the circuit is malfunctions, thus improving safety of the circuit. Furthermore, the single-pole double-throw switch structure accomplishes switching the power supply in one step by pulling a blade only, while the input selection switch structure requires two steps. 
       FIG. 4  schematically illustrates a structural diagram of an input power supply selection circuit according to a preferred embodiment of the present disclosure. The input power supply selection circuit includes a load  41 , two input power supplies P 41 , P 42 , an input selection circuit  42 , a sensing and control module  43 , and a load switch branch  44 . The input selection circuit  42  includes a first single-pole double-throw switch S 41  and a second single-pole double-throw switch S 42 . The load switch branch  44  includes a load switch SL 4 . Other devices are similar to the corresponding devices shown in  FIG. 2  and are not be described again here. Compared with  FIG. 3 , the load switch branch  44  in the input power supply selection circuit shown in  FIG. 4  further includes a semiconductor switch branch including a first semiconductor switch ss 41 , a second resistor R 42 , and a second semiconductor switch ss 42 . An operating principle of the semiconductor switch branch is similar to the semiconductor switch branch shown in  FIG. 2 , and details are not described herein. 
       FIG. 5  schematically illustrates a structural diagram of an input power supply selection circuit according to a preferred embodiment of the present disclosure. The input power supply selection circuit includes a load  51 , two input power supplies P 51 , P 52 , an input selection circuit  52 , a sensing and control module  53 , and a load switch branch  54 . The input selection circuit  52  includes a first single-pole double-throw switch S 51  and a second single-pole double-throw switch S 52 . The load switch branch  54  includes a load switch SL 5 . 
     In some preferred embodiments, the input selection circuit  52  further includes a first isolation switch S 51   a , a second isolation switch S 51   b , a third isolation switch S 52   a , and a fourth isolation switch S 52   b . The first isolation switch S 51   a  includes a first end of connected with the input power supply P 51 , and a second end connected with a first moving end of the first single-pole double-throw switch S 51 , the second isolation switch S 51   b  includes a first end connected with the input power supply P 51 , a second end connected with a first moving end of the second single-pole double-throw switch S 52 , the third isolation switch S 52   a  includes a first end connected with the input power supply P 52 , and a second end connected with the a second moving end of the first single-pole double-throw switch S 52 , and the fourth isolation switch S 52   b  includes a first end connected with the input power supply P 52 , and a second end connected with a second end of the second single-pole double-throw switch S 52 . 
     In some preferred embodiments, when the input power supply P 51  is used as the operation power supply, the first isolation switch S 51   a  and the second isolation switch S 51   b  are turned on, and when the input power supply P 52  is used as the operation power supply, the third isolation switch S 52   a  and the fourth isolation switch S 52   b  are turned on. 
     In some preferred embodiments, the load switch, each input selection switch, each single-pole double-throw switch, and each isolation switch herein may be relay switches. 
     In some preferred embodiments, the input power supply selection circuit has a safety isolation requirement, which requires a certain gap distance between the input power supplies, and the gap distance is affected by the contact gap distance of the relay switches. In  FIG. 3 , the contact gap distance between the input power supply P 31  and the input power supply P 32  is 1 due to the presence of the first single-pole double-throw switch S 31  and the second single-pole double-throw switch S 32 . If there is a higher safety isolation requirement, the contact gap distance is able to be increased by connecting more relay switches in series. 
     Still referring to  FIG. 5 , the input selection circuit  52  adds 4 isolation switches to increase the contact gap distance between the input power supply P 51  and the input power supply P 52  to 2, which improves safety of the input power supply selection circuit. The remaining devices in the input power supply selection circuit shown in  FIG. 5  are similar to the corresponding devices in the input power supply selection circuit shown in  FIG. 3 , and details are not described herein again. 
       FIG. 6  schematically illustrates a structural diagram of an input power supply selection circuit according to a preferred embodiment of the present disclosure. The input power supply selection circuit includes a load  61 , two input power supplies P 61 , P 62 , an input selection circuit  62 , a sensing and control module  63 , and a load switch branch  64 . The input selection circuit  62  includes a first single-pole double-throw switch S 61 , a second single-pole double-throw switch S 62 , a first isolation switch S 61   a , a second isolation switch S 61   b , a third isolation switch S 62   a , and a fourth isolation switch S 62   b . The load switch branch  64  includes a load switch SL 6 . 
     Compared with  FIG. 5 , the load switch branch  64  of the input power supply selection circuit shown in  FIG. 6  further includes a semiconductor switch branch including a first semiconductor switch ss 61 , a second resistor R 62 , and a second semiconductor switch ss 62 . The operating principle of the semiconductor switch branch is similar to that of the semiconductor switch branch shown in  FIG. 2 , and details are not described herein again. The remaining devices in the input power supply selection circuit shown in  FIG. 6  are similar to the corresponding devices in the input power supply selection circuit shown in  FIG. 5 , and are details not described herein again. 
       FIG. 7  schematically illustrates a structural diagram of an input power supply selection circuit according to a preferred embodiment of the present disclosure. The input power supply selection circuit includes a load  71 , at least one input power supply (P 71 -P 7 N), an input selection circuit  72 , a sensing and control module  73 , and a load switch branch  74 . The input selection circuit  72  includes at least one set of input selection switches (S 71   a , S 71   b , . . . , S 7 Na, S 7 Nb). The load switch branch  14  includes a load switch SL 7 . 
     In some preferred embodiments, the input power supply selection circuit further includes a switching converter  75  configured to perform a voltage conversion on the operation power supply. The switching converter  75  includes an input end connected with the sensing and control module  73 , the load switch branch  74  and the output end of the input selection circuit  72 , and an output end connected with both ends of the load  71 . 
     Generally, an output of the at least one input power supply (P 71 -P 7 N) is unregulated, and some operations on the load  71  require some regulation of the output of the at least one input power supply (P 71 -P 7 N). In some preferred embodiments, the sensing and control module  73  may control the switching converter  75  to control and regulate the voltage and current on the load  71 , such as performing AC to DC or DC to AC conversions. Further, the sensing and control module  73  can control the switching converter  75  to boost the output of one input power supply (P 71 -P 7 N). Furthermore, the switching converter  75  further includes an energy storage module  76  that supplies power to the load  71 . In some preferred embodiments, the energy storage module  76  may be a capacitor that provides a power hold-up time for the load  71 . When the time required for switching among the input power supply (P 71 -P 7 N) is less than the power hold-up time provided by module  76 , the load  71  is able to operate continuously without being affected by the failure of the input power supply. 
     In some preferred embodiments, prior to the switching action of the load switch branch  74  requested to be turned on or off, the sensing and control module  73  controls the switch converter  75  to disable operation or change the switch frequency and/or the duty ratio in order to reduce the operating power, thus reducing the requirement for the breaking capacity of the load switch branch  74 . 
     In some preferred embodiments, the load switch branch  74  further includes an RC branch, when an inductance of the load  71  is high, configured to prevent a spike current generated when the switch SL 7  is turned on or turned off. The RC branch is connected in parallel with the load switch SL 7 , and includes a first resistor R 71  and a first capacitor C 71 . The first resistor R 71  and the first capacitor C 71  are connected in series. In some preferred embodiments, a resistance of the first resistor R 71  and a capacitance of the first capacitor C 71  may be determined according to characteristics of the load  71 . For example, the resistance of the first resistor R 71  may range from about 1 ohm to about 1000 ohms, for example, and the capacitance value of the first capacitor C 71  may range from about 1 nanofarad to about 1 microfarad, for example. In one preferred embodiment, the resistance of the resistor R 71  may be about 10Ω, and the capacitance of the first capacitor C 71  can be about 4.7 nanofarads, for example. In some preferred embodiments, if the operation power supply is an AC power supply with about 220V, the capacitance of the first capacitor C 71  may be small, therefore, the reactance of the RC branch is high, which is close to the open circuit for the DC current. If the voltage of the operation power supply is other values (e.g., about 110V AC), the capacitance of the first capacitor C 71  may be adjusted accordingly. 
       FIG. 8  schematically illustrates a structural diagram of an input power supply selection circuit according to a preferred embodiment of the present disclosure. The input power supply selection circuit includes a load  81 , at least one input power supply (P 81 -P 8 N), an input selection circuit  82 , a sensing and control module  83 , and a load switch branch  84 . The input selection circuit  82  includes at least one set of input selection switches (S 81   a , S 81   b , . . . , S 8 Na, S 8 Nb). The load switch branch  84  includes a load switch SL 8 , a first semiconductor switch ss 81 , a second semiconductor switch ss 82 , and a second resistor R 82 . The above-mentioned devices are similar to the corresponding devices shown in  FIG. 2  and details are not described herein again. Compared with  FIG. 2 , the input power supply selection circuit shown in  FIG. 8  further includes a switching converter  85  and an energy storage module  86 , the operating principle is similar to that described above, and details are not described herein again. 
       FIG. 9  schematically illustrates a structural diagram of an input power supply selection circuit according to a preferred embodiment of the present disclosure. The input power supply selection circuit includes a load  91 , at least one input power supply (P 91 -P 9 N), an input selection circuit  92 , a sensing and control module  93 , and a load switch branch  94 . The input selection circuit  92  includes a first single-pole double-throw switch S 91  and a second single-pole double-throw switch S 92 . The load switch branch  94  includes a load switch SL 9 . The above-mentioned devices are similar to the corresponding devices shown in  FIG. 3 , and details are not described herein again. Compared with  FIG. 3 , the input power supply selection circuit shown in  FIG. 9  further includes a switching converter  95  and an energy storage module  96 , the operating principle thereof is similar to that described above, and details are not described herein again. 
       FIG. 10  schematically illustrates a structural diagram of an input power supply selection circuit according to a preferred embodiment of the present disclosure. The input power supply selection circuit includes a load  101 , at least one input power supply (P 101 -P 10 N), an input selection circuit  102 , a sensing and control module  103 , and a load switch branch  104 . The input selection circuit  102  includes a first single-pole double-throw switch S 101  and a second single-pole double-throw switch S 102 . The load switch branch  104  includes a load switch SL 10 , a first semiconductor switch ss 101 , a second semiconductor switch ss 102 , and a second resistor R 102 . The above-mentioned devices are similar to the corresponding devices shown in  FIG. 4 , and details are not described herein again. Compared with  FIG. 4 , the input power supply selection circuit shown in  FIG. 10  further includes a switching converter  105  and an energy storage module  106 , the operating principle is similar to that described above, and details are not described herein again. 
       FIG. 11  schematically illustrates a structural diagram of an input power supply selection circuit according to a preferred embodiment of the present disclosure. The input power supply selection circuit includes a load  111 , at least one input power (P 111 -P 11 N), an input selection circuit  112 , a sensing and control module  113 , and a load switch branch  114 . The input selection circuit  112  includes a first single-pole double-throw switch S 111 , a second single-pole double-throw switch S 112 , and isolation switches (S 111   a , S 111   b , S 112   a , and S 112   b ). The load switch branch  114  includes a load switch SL 11 . The above-mentioned devices are similar to the corresponding devices shown in  FIG. 5 , and details are not described herein again. Compared with  FIG. 5 , the input power supply selection circuit shown in  FIG. 11  further includes a switching converter  115  and an energy storage module  116 , the operating principle is similar to that described above, and details are not described herein again. 
       FIG. 12  schematically illustrates a structural diagram of an input power supply selection circuit according to a preferred embodiment of the present disclosure. The input power supply selection circuit includes a load  121 , at least one input power supply (P 121 -P 12 N), an input selection circuit  122 , a sensing and control module  123 , and a load switch branch  124 . The input selection circuit  122  includes a first single-pole double-throw switch S 121 , a second single-pole double-throw switch S 122 , and isolation switches (S 121   a , S 121   b , S 122   a , and S 122   b ). The load switch branch  124  includes a load switch SL 12 , a first semiconductor switch ss 121 , a second semiconductor switch ss 122 , and a second resistor R 122 . The above-mentioned devices are similar to the corresponding devices shown in  FIG. 6 , and details are not described herein again. Compared with  FIG. 6 , the input power supply selection circuit shown in FIG.  12  further includes a switching converter  125  and an energy storage module  126 , the operating principle is similar to that described above, and details are not described herein. 
     Although the present disclosure has been disclosed above with reference to preferred embodiments thereof, it should be understood that the present disclosure is presented by way of example only, and not limitation. Those skilled in the art may modify and vary the preferred embodiments without departing from the spirit and scope of the present disclosure. 
     While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.