Patent Publication Number: US-2023155488-A1

Title: Conversion circuit and related electronic device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/CN2020/105423, filed on Jul. 29, 2020, the disclosure of which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The embodiments relate to the circuit field, a conversion circuit, and a related electronic device. 
     BACKGROUND 
     With development of an artificial intelligence (AI) technology, a computing capability and a capacity of a chip supporting AI continuously increase, resulting in increased power consumption. Therefore, a power supply solution of such a chip is particularly important. 
     In a conventional technology, a conversion circuit in which capacitors are in an equivalent serial connection relationship is generally used in a resonant switched capacitor solution in the power supply solution of such a chip. After running for a long time, the conversion circuit has a high risk of voltage imbalance. 
     SUMMARY 
     The embodiments may provide a conversion circuit and a related electronic device, to balance voltages at both ends of capacitors, and implement different voltage transformation ratios by adjusting a quantity of capacitor modules. 
     A first aspect of the embodiments may provide a conversion circuit, including: a capacitor module, a balancing module, and a startup module. The capacitor module includes at least a first capacitor and a second capacitor. The balancing module includes at least a first resonant circuit. The startup module includes a direct current-direct current converter and a target capacitor. The first resonant circuit includes at least two groups of switches connected in parallel to each other and a first resonant cavity connected between the two groups of switches. The first capacitor is connected in series to the second capacitor, and the first capacitor is connected in parallel to the target capacitor. The first resonant circuit is separately connected to both ends of the first capacitor and the second capacitor by using the startup module. The balancing module balances voltages at both ends of the first capacitor and the second capacitor by controlling the switches in the first resonant circuit in conjunction with influence of the first resonant cavity on a current. The startup module is configured to start the balancing module and the capacitor module. 
     In this embodiment, the balancing module balances the voltages at both ends of the first capacitor and the second capacitor by controlling the switches in the first resonant circuit in conjunction with the influence of the first resonant cavity on the current. Further, different transformation ratios are obtained based on a quantity of capacitors of the capacitor module and a series voltage division principle. In addition, the startup module is used to implement a closed loop and a stable output voltage, to ensure slow startup of the conversion circuit. 
     Optionally, in a possible implementation of the first aspect, in the foregoing structure, one group of switches in the two groups of switches in the first resonant circuit includes at least a first switch and a third switch, and the other group of switches in the two groups of switches in the first resonant circuit includes at least a second switch and a fourth switch. The first switch and the third switch are not simultaneously turned on, and the second switch and the fourth switch are not simultaneously turned on. 
     In this possible implementation, a conduction status of each switch in the first resonant circuit is controlled, so that the first capacitor may perform energy transmission with the second capacitor by using the first resonant circuit, thereby balancing voltages at both ends of capacitors. Further, a twofold transformation ratio is obtained based on a quantity 2 of capacitors of the capacitor module and the series voltage division principle. In addition, the startup module is used to implement the closed loop and the stable output voltage, to ensure slow startup of the conversion circuit. 
     Optionally, in a possible implementation of the first aspect, in the foregoing structure, the first resonant cavity includes at least a first resonant capacitor and a first resonant inductor. One end of the first resonant cavity is separately connected to a second end of the first switch and a first end of the third switch, and the other end of the first resonant cavity is separately connected to a second end of the second switch and a first end of the fourth switch. 
     In this possible implementation, the first resonant cavity is connected to the switches in the first resonant circuit, and a conduction status of each switch in the first resonant circuit may be controlled, so that the first capacitor may perform energy transmission with the second capacitor by using the first resonant circuit, thereby balancing voltages at both ends of capacitors. 
     Optionally, in a possible implementation of the first aspect, in the foregoing structure, the first switch is connected in series to the third switch, and the second switch is connected in series to the fourth switch. One end of the second capacitor is connected to a first end of the second switch, and the other end of the second capacitor is separately connected to a first end of the first switch, a first end of the direct current-direct current converter, and one end of the first capacitor. A second end of the direct current-direct current converter is separately connected to one end of the target capacitor and a second end of the fourth switch. The other end of the first capacitor is connected to a third end of the direct current-direct current converter, and a fourth end of the direct current-direct current converter is separately connected to a second end of the third switch and the other end of the target capacitor. 
     In this possible implementation, the direct current-direct current converter is connected to the switches and the capacitors, to implement the closed loop and the stable output voltage, and ensure slow startup of the conversion circuit. Further, a conduction status of each switch in the first resonant circuit may be controlled, so that the first capacitor may perform energy transmission with the second capacitor by using the first resonant circuit, thereby balancing voltages at both ends of capacitors. Further, a twofold transformation ratio is obtained based on a quantity 2 of capacitors of the capacitor module and the series voltage division principle. 
     Optionally, in a possible implementation of the first aspect, in the foregoing structure, the capacitor module further includes a third capacitor, the balancing module further includes a second resonant circuit, and the second resonant circuit includes at least two groups of switches connected in parallel to each other and a second resonant cavity connected between the two groups of switches. One group of switches in the two groups of switches in the second resonant circuit includes at least a fifth switch and a seventh switch, and the other group of switches in the two groups of switches in the second resonant circuit includes at least a sixth switch and an eighth switch. The second resonant cavity includes at least a second resonant capacitor and a second resonant inductor. The second resonant circuit is separately connected to both ends of the first capacitor and the third capacitor by using the startup module. The balancing module balances voltages at both ends of the first capacitor and the third capacitor by controlling the switches in the second resonant circuit in conjunction with influence of the second resonant cavity on a current. The fifth switch and the seventh switch are not simultaneously turned on, and the sixth switch and the eighth switch are not simultaneously turned on. 
     In this possible implementation, a conversion circuit that may implement a threefold transformation ratio and may be slowly started is provided. 
     Optionally, in a possible implementation of the first aspect, in the foregoing structure, the balancing module further includes a second resonant circuit, and the second resonant circuit includes at least two groups of switches connected in parallel to each other and a second resonant cavity connected between the two groups of switches. One group of switches in the two groups of switches in the second resonant circuit includes at least a fifth switch and a seventh switch, and the other group of switches in the two groups of switches in the second resonant circuit includes at least a sixth switch and an eighth switch. The second resonant cavity includes at least a second resonant capacitor and a second resonant inductor. The balancing module balances voltages at both ends of the first capacitor and the second resonant capacitor by controlling the switches in the second resonant circuit in conjunction with influence of the second resonant cavity on a current. The fifth switch and the seventh switch are not simultaneously turned on, and the sixth switch and the eighth switch are not simultaneously turned on. 
     In this possible implementation, a conversion circuit that may implement a threefold transformation ratio and may be slowly started is provided. 
     Optionally, in a possible implementation of the first aspect, in the foregoing structure, the first resonant capacitor is connected in series to the first resonant inductor, and the second resonant capacitor is connected in series to the second resonant inductor. The first capacitor, the second capacitor, and the third capacitor are sequentially connected in series. One end of the third capacitor is connected to a first end of the sixth switch, and the other end of the third capacitor is separately connected to a first end of the fifth switch, the first end of the second switch, and one end of the second capacitor. The other end of the second capacitor is separately connected to the first end of the first switch, one end of the first capacitor, and the first end of the direct current-direct current converter, and the second end of the direct current-direct current converter is separately connected to one end of the target capacitor, the second end of the fourth switch, and a second end of the eighth switch. The other end of the first capacitor is connected to the third end of the direct current-direct current converter, and the fourth end of the direct current-direct current converter is separately connected to the other end of the target capacitor, the second end of the third switch, and a second end of the seventh switch. The first switch is connected in series to the third switch, the second switch is connected in series to the fourth switch, one end of the first resonant cavity is separately connected to the second end of the first switch and the first end of the third switch, and the other end of the first resonant cavity is separately connected to the second end of the second switch and the first end of the fourth switch. The fifth switch is connected in series to the seventh switch, the sixth switch is connected in series to the eighth switch, one end of the second resonant cavity is separately connected to a second end of the fifth switch and a first end of the seventh switch, and the other end of the second resonant cavity is separately connected to a second end of the sixth switch and a first end of the eighth switch. 
     In this possible implementation, the first capacitor, the second capacitor, and the third capacitor are sequentially connected in series, and a conduction status of each switch in the first resonant circuit and the second resonant circuit is controlled, so that the first capacitor may perform energy transmission with the second capacitor by using the first resonant circuit and perform energy transmission with the third capacitor by using the second resonant circuit, thereby balancing voltages at both ends of capacitors. Each resonant circuit may convert partial power and power conversion efficiency may be high. Further, a threefold transformation ratio is obtained based on a quantity 3 of capacitors of the capacitor module and the series voltage division principle. That is, a voltage gain is 3:1 or 1:3. In addition, the startup module is used to implement the closed loop and the stable output voltage, to ensure slow startup of the conversion circuit. 
     Optionally, in a possible implementation of the first aspect, in the foregoing structure, the capacitor module further includes a third capacitor, the first resonant capacitor is connected in series to the first resonant inductor, and the second resonant capacitor is connected in series to the second resonant inductor. A first end of the sixth switch is connected to one end of the third capacitor, and the fifth switch is separately connected to one end of the second capacitor and the first end of the second switch. The other end of the second capacitor is separately connected to the first end of the first switch, one end of the first capacitor, and the first end of the direct current-direct current converter, and the second end of the direct current-direct current converter is separately connected to one end of the target capacitor, the second end of the fourth switch, and a second end of the eighth switch. The other end of the first capacitor is separately connected to the other end of the third capacitor and the third end of the direct current-direct current converter, and the fourth end of the direct current-direct current converter is separately connected to the other end of the target capacitor, the second end of the third switch, and a second end of the seventh switch. The first switch is connected in series to the third switch, the second switch is connected in series to the fourth switch, one end of the first resonant cavity is separately connected to the second end of the first switch and the first end of the third switch, and the other end of the first resonant cavity is separately connected to the second end of the second switch and the first end of the fourth switch. The fifth switch is connected in series to the seventh switch, the sixth switch is connected in series to the eighth switch, one end of the second resonant cavity is separately connected to a second end of the fifth switch and a first end of the seventh switch, and the other end of the second resonant cavity is separately connected to a second end of the sixth switch and a first end of the eighth switch. 
     In this possible implementation, the first capacitor, the second capacitor, and the second resonant capacitor are sequentially connected in series, and a conduction status of each switch in the first resonant circuit and the second resonant circuit is controlled, so that the first capacitor may perform energy transmission with the second capacitor by using the first resonant circuit and perform energy transmission with the second resonant capacitor by using the second resonant circuit, thereby balancing voltages at both ends of capacitors. Each resonant circuit may convert partial power and power conversion efficiency may be high. Further, a threefold transformation ratio is obtained based on a quantity 2 of capacitors of the capacitor module, a quantity 1 of second resonant capacitors, and the series voltage division principle. That is, a voltage gain is 3:1 or 1:3. In addition, the startup module is used to implement the closed loop and the stable output voltage, to ensure slow startup of the conversion circuit. 
     Optionally, in a possible implementation of the first aspect, in the foregoing structure, the conversion circuit further includes a direct current power supply, the first resonant capacitor is connected in series to the first resonant inductor, and the second resonant capacitor is connected in series to the second resonant inductor. A first end of the sixth switch is connected to one end of the direct current power supply, and the fifth switch is separately connected to one end of the second capacitor and the first end of the second switch. The other end of the second capacitor is separately connected to the first end of the first switch, one end of the first capacitor, and the first end of the direct current-direct current converter, and the second end of the direct current-direct current converter is separately connected to one end of the target capacitor, the second end of the fourth switch, and a second end of the eighth switch. The other end of the first capacitor is separately connected to the other end of the direct current power supply and the third end of the direct current-direct current converter, and the fourth end of the direct current-direct current converter is separately connected to the other end of the target capacitor, the second end of the third switch, and a second end of the seventh switch. The first switch is connected in series to the third switch, the second switch is connected in series to the fourth switch, one end of the first resonant cavity is separately connected to the second end of the first switch and the first end of the third switch, and the other end of the first resonant cavity is separately connected to the second end of the second switch and the first end of the fourth switch. The fifth switch is connected in series to the seventh switch, the sixth switch is connected in series to the eighth switch, one end of the second resonant cavity is separately connected to a second end of the fifth switch and a first end of the seventh switch, and the other end of the second resonant cavity is separately connected to a second end of the sixth switch and a first end of the eighth switch. 
     In this possible implementation, a conversion circuit that may implement a threefold transformation ratio and may be slowly started is provided. 
     Optionally, in a possible implementation of the first aspect, in the foregoing structure, the capacitor module further includes a fourth capacitor, the balancing module further includes a third resonant circuit, and the third resonant circuit includes at least two groups of switches connected in parallel to each other and a third resonant cavity connected between the two groups of switches. One group of switches in the two groups of switches in the third resonant circuit includes at least a ninth switch and an eleventh switch, and the other group of switches in the two groups of switches in the third resonant circuit includes at least a tenth switch and a twelfth switch. The third resonant cavity includes at least a third resonant capacitor and a third resonant inductor. The third resonant circuit is separately connected to both ends of the first capacitor and the fourth capacitor by using the startup module. The balancing module balances voltages at both ends of the first capacitor and the fourth capacitor by controlling the switches in the third resonant circuit in conjunction with influence of the third resonant cavity on a current. The ninth switch and the eleventh switch are not simultaneously turned on, and the tenth switch and the twelfth switch are not simultaneously turned on. 
     In this possible implementation, a conversion circuit that may implement a fourfold transformation ratio and may be slowly started is provided. 
     Optionally, in a possible implementation of the first aspect, in the foregoing structure, the balancing module further includes a third resonant circuit, and the third resonant circuit includes at least two groups of switches connected in parallel to each other and a third resonant cavity connected between the two groups of switches. One group of switches in the two groups of switches in the third resonant circuit includes at least a ninth switch and an eleventh switch, and the other group of switches in the two groups of switches in the third resonant circuit includes at least a tenth switch and a twelfth switch. The third resonant cavity includes at least a third resonant capacitor and a third resonant inductor. The balancing module balances voltages at both ends of the first capacitor and the third resonant capacitor by controlling the switches in the third resonant circuit in conjunction with influence of the third resonant cavity on a current. The ninth switch and the eleventh switch are not simultaneously turned on, and the tenth switch and the twelfth switch are not simultaneously turned on. 
     In this possible implementation, a conversion circuit that may implement a fourfold transformation ratio and may be slowly started is provided. 
     Optionally, in a possible implementation of the first aspect, in the foregoing structure, the third resonant capacitor is connected in series to the third resonant inductor, and the first capacitor, the second capacitor, the third capacitor, and the fourth capacitor are sequentially connected in series. One end of the fourth capacitor is connected to a first end of the tenth switch, the other end of the fourth capacitor is separately connected to a first end of the ninth switch, the first end of the sixth switch, and one end of the third capacitor, and the other end of the third capacitor is separately connected to the first end of the fifth switch, the first end of the second switch, and one end of the second capacitor. The other end of the second capacitor is separately connected to the first end of the first switch, one end of the first capacitor, and the first end of the direct current-direct current converter, and the second end of the direct current-direct current converter is separately connected to one end of the target capacitor, the second end of the fourth switch, the second end of the eighth switch, and a second end of the twelfth switch. The other end of the first capacitor is connected to the third end of the direct current-direct current converter, and the fourth end of the direct current-direct current converter is separately connected to the other end of the target capacitor, the second end of the third switch, the second end of the seventh switch, and a second end of the eleventh switch. The ninth switch is connected in series to the eleventh switch, the tenth switch is connected in series to the twelfth switch, one end of the third resonant cavity is separately connected to a second end of the ninth switch and a first end of the eleventh switch, and the other end of the third resonant cavity is separately connected to a second end of the tenth switch and a first end of the twelfth switch. 
     In this possible implementation, the first capacitor, the second capacitor, the third capacitor, and the fourth capacitor are sequentially connected in series, and a conduction status of each switch in the first resonant circuit and the second resonant circuit is controlled, so that the first capacitor may perform energy transmission with the second capacitor by using the first resonant circuit, perform energy transmission with the third capacitor by using the second resonant circuit, and perform energy transmission with the fourth capacitor by using the third resonant circuit, thereby balancing voltages at both ends of capacitors. Each resonant circuit may convert partial power and power conversion efficiency may be high. Further, a fourfold transformation ratio is obtained based on a quantity 4 of capacitors of the capacitor module and the series voltage division principle. That is, a voltage gain is 4:1 or 1:4. In addition, the startup module is used to implement the closed loop and the stable output voltage, to ensure slow startup of the conversion circuit. 
     Optionally, in a possible implementation of the first aspect, in the foregoing structure, the capacitor module further includes a fourth capacitor, and the third resonant capacitor is connected in series to the third resonant inductor. A first end of the tenth switch is connected to one end of the fourth capacitor, the ninth switch is separately connected to the first end of the sixth switch and one end of the third capacitor, and the other end of the third capacitor is separately connected to the first end of the fifth switch, the first end of the second switch, and one end of the second capacitor. The other end of the second capacitor is separately connected to the first end of the first switch, one end of the first capacitor, and the first end of the direct current-direct current converter, and the second end of the direct current-direct current converter is separately connected to one end of the target capacitor, the second end of the fourth switch, the second end of the eighth switch, and a second end of the twelfth switch. The other end of the first capacitor is separately connected to the other end of the fourth capacitor and the third end of the direct current-direct current converter, and the fourth end of the direct current-direct current converter is separately connected to the other end of the target capacitor, the second end of the third switch, the second end of the seventh switch, and a second end of the eleventh switch. The ninth switch is connected in series to the eleventh switch, the tenth switch is connected in series to the twelfth switch, one end of the third resonant cavity is separately connected to a second end of the ninth switch and a first end of the eleventh switch, and the other end of the third resonant cavity is separately connected to a second end of the tenth switch and a first end of the twelfth switch. 
     In this possible implementation, a conversion circuit that may implement a fourfold transformation ratio and may be slowly started is provided. 
     Optionally, in a possible implementation of the first aspect, in the foregoing structure, the conversion circuit further includes a direct current power supply, and the third resonant capacitor is connected in series to the third resonant inductor. A first end of the tenth switch is connected to one end of the direct current power supply, the ninth switch is separately connected to the first end of the sixth switch and one end of the third capacitor, and the other end of the third capacitor is separately connected to the first end of the fifth switch, the first end of the second switch, and one end of the second capacitor. The other end of the second capacitor is separately connected to the first end of the first switch, one end of the first capacitor, and the first end of the direct current-direct current converter, and the second end of the direct current-direct current converter is separately connected to one end of the target capacitor, the second end of the fourth switch, the second end of the eighth switch, and a second end of the twelfth switch. The other end of the first capacitor is separately connected to the other end of the direct current power supply and the third end of the direct current-direct current converter, and the fourth end of the direct current-direct current converter is separately connected to the other end of the target capacitor, the second end of the third switch, the second end of the seventh switch, and a second end of the eleventh switch. The ninth switch is connected in series to the eleventh switch, the tenth switch is connected in series to the twelfth switch, one end of the third resonant cavity is separately connected to a second end of the ninth switch and a first end of the eleventh switch, and the other end of the third resonant cavity is separately connected to a second end of the tenth switch and a first end of the twelfth switch. 
     In this possible implementation, a conversion circuit that may implement a fourfold transformation ratio and may be slowly started is provided. 
     Optionally, in a possible implementation of the first aspect, in the foregoing structure, a voltage at both ends of the target capacitor is an output voltage, and a voltage at both ends of the capacitor module is an input voltage. 
     In this possible implementation, the voltage at both ends of the target capacitor is the output voltage, and the voltage at both ends of the capacitor module is the input voltage, so that the conversion circuit may implement voltage step-down. 
     Optionally, in a possible implementation of the first aspect, in the foregoing structure, a voltage at both ends of the target capacitor is an input voltage, and a voltage at both ends of the capacitor module is an output voltage. 
     In this possible implementation, the voltage at both ends of the target capacitor is the input voltage, and the voltage at both ends of the capacitor module is the output voltage, so that the conversion circuit may implement voltage step-up. 
     Optionally, in a possible implementation of the first aspect, in the foregoing structure, the switch is an insulated gate bipolar transistor IGBT. 
     In this possible implementation, a feasible solution of the conversion circuit is provided. 
     Optionally, in a possible implementation of the first aspect, in the foregoing structure, the switch is an N-channel enhanced insulated gate field-effect transistor NMOS. 
     In this possible implementation, a feasible solution of the conversion circuit is provided. 
     Optionally, in a possible implementation of the first aspect, in the foregoing structure, the first switch and the third switch are diodes, and the second switch and the fourth switch are N-channel enhanced insulated gate field-effect transistors NMOSs. 
     In this possible implementation, a feasible solution of the conversion circuit is provided. 
     Optionally, in a possible implementation of the first aspect, in the foregoing structure, the first switch, the third switch, the fifth switch, and the seventh switch are diodes, and the second switch, the fourth switch, the sixth switch, and the eighth switch are N-channel enhanced insulated gate field-effect transistors NMOSs. 
     In this possible implementation, a feasible solution of the conversion circuit is provided. 
     Optionally, in a possible implementation of the first aspect, in the foregoing structure, the direct current-direct current converter includes a first startup switch, a second startup switch, and a startup inductor. 
     In this possible implementation, a feasible solution of the conversion circuit is provided. A second aspect of embodiments provides an electronic device, including the conversion circuit according to any one of the first aspect or the possible implementations of the first aspect. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of an architecture of a power supply module according to an embodiment; 
         FIG.  2    is a schematic diagram of a first embodiment of a conversion circuit according to an embodiment; 
         FIG.  3    is an equivalent diagram of a resonant circuit according to an embodiment; 
         FIG.  4    is a schematic diagram of a first structure of a DC/DC converter according to an embodiment; 
         FIG.  5    is a schematic diagram of a second structure of a DC/DC converter according to an embodiment; 
         FIG.  6    is a schematic diagram of a third structure of a DC/DC converter according to an embodiment; 
         FIG.  7    is a schematic diagram of a fourth structure of a DC/DC converter according to an embodiment; 
         FIG.  8    is a schematic diagram of a fifth structure of a DC/DC converter according to an embodiment; 
         FIG.  9    is a schematic diagram of a sixth structure of a DC/DC converter according to an embodiment; 
         FIG.  10    is a schematic diagram of a seventh structure of a DC/DC converter according to an embodiment; 
         FIG.  11    is an equivalent diagram of a conversion circuit in a first cycle in a first embodiment according to an embodiment; 
         FIG.  12    is an equivalent diagram of a conversion circuit in a second cycle in a first embodiment according to an embodiment; 
         FIG.  13    is a schematic diagram of a second embodiment of a conversion circuit according to an embodiment; 
         FIG.  14    is a schematic diagram of a third embodiment of a conversion circuit according to an embodiment; 
         FIG.  15    is a schematic diagram of a fourth embodiment of a conversion circuit according to an embodiment; 
         FIG.  16    is a schematic diagram of a fifth embodiment of a conversion circuit according to an embodiment; 
         FIG.  17    is a schematic diagram in which a first structure of a DC/DC converter is used in a fifth embodiment of a conversion circuit according to an embodiment; 
         FIG.  18    is a schematic diagram of in-phase switches according to an embodiment; 
         FIG.  19    is a schematic diagram of out-of-phase switches according to an embodiment; 
         FIG.  20    is an equivalent diagram of a conversion circuit in a first cycle in a fifth embodiment according to an embodiment; 
         FIG.  21    is an equivalent diagram of a conversion circuit in a second cycle in a fifth embodiment according to an embodiment; 
         FIG.  22    is a schematic diagram of a sixth embodiment of a conversion circuit according to an embodiment; 
         FIG.  23    is an equivalent diagram of a conversion circuit in a first cycle in a sixth embodiment according to an embodiment; 
         FIG.  24    is an equivalent diagram of a conversion circuit in a second cycle in a sixth embodiment according to an embodiment; 
         FIG.  25    is a schematic diagram of a seventh embodiment of a conversion circuit according to an embodiment; 
         FIG.  26    is another equivalent circuit diagram of a first resonant circuit according to an embodiment; 
         FIG.  27    is another equivalent circuit diagram of a first resonant circuit according to an embodiment; 
         FIG.  28    is a schematic diagram of an eighth embodiment of a conversion circuit according to an embodiment; 
         FIG.  29    is an equivalent diagram of a conversion circuit in a first cycle in an eighth embodiment according to an embodiment; 
         FIG.  30    is an equivalent diagram of a conversion circuit in a second cycle in an eighth embodiment according to an embodiment; 
         FIG.  31    is a simulation waveform diagram of an eighth embodiment of a conversion circuit according to an embodiment; 
         FIG.  32    is a schematic diagram of a ninth embodiment of a conversion circuit according to an embodiment; 
         FIG.  33    is a schematic diagram of a tenth embodiment of a conversion circuit according to an embodiment; 
         FIG.  34    is a schematic diagram of an eleventh embodiment of a conversion circuit according to an embodiment; 
         FIG.  35    is a schematic diagram of a twelfth embodiment of a conversion circuit according to an embodiment; 
         FIG.  36    is a schematic diagram of a thirteenth embodiment of a conversion circuit according to an embodiment; 
         FIG.  37    is an equivalent diagram of a conversion circuit in a first cycle in a thirteenth embodiment according to an embodiment; 
         FIG.  38    is an equivalent diagram of a conversion circuit in a second cycle in a thirteenth embodiment according to an embodiment; 
         FIG.  39    is a schematic diagram of a fourteenth embodiment of a conversion circuit according to an embodiment; 
         FIG.  40    is a schematic diagram of a fifteenth embodiment of a conversion circuit according to an embodiment; 
         FIG.  41    is a schematic diagram of a sixteenth embodiment of a conversion circuit according to an embodiment; and 
         FIG.  42    is a schematic diagram of a structure of an electronic device in which a power supply module is located according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The embodiments may provide a conversion circuit to balance voltages at both ends of capacitors and implement different transformation ratios. 
     It should be understood that the conversion circuit in the embodiments may be applied to any direct current conversion scenario, and may be applied to a power supply module.  FIG.  1    is a schematic diagram of an architecture of a power supply module according to an embodiment. As shown in  FIG.  1   , the power supply module  1090  includes a direct current-direct current conversion circuit  1091 , a point of load (POL)  1092 , and the like. 
     A main function of the direct current-direct current conversion circuit  1091  is to convert an input voltage 40 V to 60 V into 3.2 V to 12 V, and transmit the input voltage to the POL by using a bus. 
     A main function of the POL  1092  is to convert 3.2 V to 12 V into 0.7 V to 1.8 V, and supply power to a processor  1080 . 
     The conversion circuit in embodiments may include two types: buck and boost, which are separately described below. 
     I. Buck (a voltage at both ends of a first capacitor is an output voltage, and a voltage at both ends of a capacitor module is an input voltage) 
     As shown in  FIG.  2   , a conversion circuit provided in an embodiment may include a capacitor module, a balancing module, and a startup module. 
     The capacitor module includes a first capacitor C 1  and a second capacitor C 2 . The balancing module includes a first resonant circuit. The startup module includes a direct current-direct current converter (that is, a DC/DC converter, referred to as a converter) and a target capacitor C 0 . The first resonant circuit includes at least two groups of switches connected in parallel to each other and a first resonant cavity connected between the two groups of switches. One group of switches in the two groups of switches in the first resonant circuit includes a first switch Q1-1 and a third switch Q1-3, and the other group of switches in the two groups of switches in the first resonant circuit includes a second switch Q1-2 and a fourth switch Q1-4. The first resonant cavity includes at least a first resonant capacitor Cr 1  and a first resonant inductor Lr 1 . The first capacitor C 1  is connected in series to the second capacitor C 2 , and the first capacitor C 1  is connected in parallel to the target capacitor C 0 . The first switch Q1-1 is connected in series to the third switch Q1-3, and the second switch Q1-2 is connected in series to the fourth switch Q1-4. One end of the second capacitor C 2  is connected to a first end of the second switch Q1-2, and the other end of the second capacitor C 2  is separately connected to a first end of the first switch Q1-1, a first end of the converter, and one end of the first capacitor C 1 . A second end of the converter is separately connected to one end of the target capacitor C 0  and a second end of the fourth switch Q1-4. The other end of the first capacitor C 1  is connected to a third end of the direct current-direct current converter, and a fourth end of the converter is separately connected to a second end of the third switch Q1-3 and the other end of the target capacitor C 0 . One end of the first resonant cavity is separately connected to a second end of the first switch Q1-1 and a first end of the third switch Q1-3, and the other end of the first resonant cavity is separately connected to a second end of the second switch Q1-2 and a first end of the fourth switch Q1-4. The balancing module balances voltages at both ends of the first capacitor C 1  and the second capacitor C 2  by controlling turn-on or turn-off of the switches. 
     In this embodiment, the first resonant cavity may include the first resonant capacitor Cr 1  and the first resonant inductor Lr 1  that are connected in series; or may include the first resonant capacitor Cr 1  and the first resonant inductor Lr 1  that are connected in series, and another capacitor connected to both ends of the first resonant inductor Lr 1  as a whole. There are other types of equivalent forms. This is not limited herein. 
     In this embodiment, an example in which the switch is an N-channel enhanced insulated gate field-effect transistor with a N-channel metal oxide semiconductor (NMOS) may be used for illustration. It may be understood that the switch may alternatively be a controllable component such as an insulated gate bipolar transistor (IGBT), a gallium nitride (GaN) power switch, or a silicon carbide (SiC) switch. For example, as shown in  FIG.  3   , the first switch and the third switch may alternatively be replaced with diodes. This is not limited herein. 
     The direct current-direct current converter in the startup module in this embodiment may have a plurality of forms, which are separately described below. 
     1. Buck Converter 
       FIG.  4    is a schematic diagram of a structure of the direct current-direct current converter in the startup module. 
     A first end of a switch  1  is a first end of the startup module, a second end of a switch  1  is separately connected to one end of an inductor L and a first end of a switch  2 , and the other end of the inductor L is connected to a second end of the startup module. A second end of the switch  2  is separately connected to a third end and a fourth end of the startup module. As shown in  FIG.  5   , the switch  2  may be replaced with a diode D. This is not limited herein. 
     A closed loop in this embodiment may refer to detecting feedback on an output voltage Vo and adjusting a duty cycle of the DC/DC converter. This is equivalent to changing an input voltage of the DC/DC converter, so that the output voltage may be controlled. That BUCK is a DC/DC converter is used as an example. A duty cycle of BUCK is D, and in this case, Vo=(Vin−N*Vo)*D. N is a quantity of resonant cavities. 
     2. Boost Converter 
       FIG.  6    is a schematic diagram of another structure of the direct current-direct current converter in the startup module. 
     One end of an inductor L is a first end of the startup module, the other end of the inductor L is separately connected to a first end of a switch  1  and a first end of a switch  2 , and a second end of the switch  1  is connected to a second end of the startup module. A second end of the switch  2  is separately connected to a third end and a fourth end of the startup module. As shown in  FIG.  7   , the switch  1  may be replaced with a diode D. This is not limited herein. 
     3. Buck-Boost Converter 
       FIG.  8    is a schematic diagram of another structure of the direct current-direct current converter in the startup module. 
     A first end of a switch  1  is a first end of the startup module, a second end of the switch  1  is separately connected to a first end of a switch  2  and one end of an inductor, and the switch  2  is connected to a second end of the startup module. The other end of the inductor is separately connected to a third end and a fourth end of the startup module. As shown in  FIG.  9   , the switch  2  may be replaced with a diode D. This is not limited herein. 
     The direct current-direct current converter in the startup module in this embodiment may have a plurality of forms. The foregoing several forms are merely examples. In actual application, the direct current-direct current converter in the startup module may alternatively be in another form. For example, a circuit shown in  FIG.  10    is also another form of the direct current-direct current converter in the startup module. This is not limited herein. 
     A complete cycle of the switches in the balancing module in this embodiment may include a first cycle and a second cycle, and the first cycle and the second cycle may account for half of the complete cycle of the switches. In actual application, the complete cycle may include the first cycle, a dead time, and the second cycle. This is not limited herein. 
     The following describes in detail a working principle of the conversion circuit shown in  FIG.  2   . 
     First Cycle: 
       FIG.  2    may be equivalent to  FIG.  11   , when the first switch Q1-1 and the second switch Q1-2 are turned on (a high level is input), and the third switch Q1-3 and the fourth switch Q1-4 are turned off (a low level is input). The second capacitor C 2  transmits energy to the first resonant inductor Lr 1  and the first resonant capacitor Cr 1 . 
     Second Cycle: 
       FIG.  2    may be equivalent to  FIG.  12   , when the third switch Q1-3 and the fourth switch Q1-4 are turned on (a high level is input), and the first switch Q1-1 and the second switch Q1-2 are turned off (a low level is input). The first resonant inductor Lr 1  and the first resonant capacitor Cr 1  charge the target capacitor C 0  (that is, C 0  is an output capacitor). In this case, the target capacitor C 0  is the output capacitor. Because a duty cycle of a drive signal is close to 50%, a voltage of the target capacitor C 0  (that is, the output capacitor C 0 ) is equal to a voltage of the second capacitor C 2 . Based on a principle of series capacitor voltages, a voltage at both ends of the first capacitor C 1  is input voltage Vin−Vo. In addition, the DC/DC converter works in a closed-loop manner, and when the input voltage Vin changes, a gain of the conversion circuit is controlled, that is, the input voltage of the DC/DC converter is equivalently controlled, to ensure that the output voltage of the conversion circuit remains stable (that is, equal to Vo). 
     In this embodiment, the balancing module may balance the voltages at both ends of the first capacitor and the second capacitor by controlling the switches in the first resonant circuit in conjunction with influence of the first resonant cavity on a current. Further, different transformation ratios are obtained based on a quantity of capacitors of the capacitor module and a series voltage division principle. In addition, on the one hand, because there is the converter, during power-on, the conversion circuit in this embodiment can normally implement slow startup (that is, the output voltage Vo can be controlled; actually, a power-on waveform and a voltage rising speed of Vo can be controlled). This effectively resolves a problem that a conventional resonant switched capacitor circuit cannot be controlled in a closed-loop manner and is not easy to implement slow startup. On the other hand, in case of overcurrent, the converter may be used to implement detection and protection. 
     For ease of understanding, different transformation ratios are separately described below. 
     1. A ratio of the input voltage to the output voltage is N:1. 
     The capacitor module of the conversion circuit in this embodiment may have a plurality of forms, which are separately described below. 
     1.1. The first capacitor C 1 , the second capacitor C 2 , and an N th  capacitor Cn are sequentially connected in series. 
       FIG.  13    is a schematic diagram of a second embodiment of a conversion circuit according to an embodiment. An embodiment may provide a second embodiment of a conversion circuit, including a capacitor module, a balancing module, and a startup module. 
     The balancing module includes a first resonant circuit and an (N−1) th  resonant circuit. The capacitor module includes a first capacitor C 1 , a second capacitor C 2 , and an N th  capacitor Cn, where N is an integer greater than or equal to 3. The first resonant circuit includes at least four switches and a first resonant cavity. The four switches are respectively a first switch Q1-1, a second switch Q1-2, a third switch Q1-3, and a fourth switch Q1-4. The first resonant cavity includes a first resonant capacitor Cr 1  and a first resonant inductor Lr 1 . The (N−1) th  resonant circuit includes at least four switches and an (N−1) th  resonant cavity. The four switches are respectively a fifth switch Qn-1, a sixth switch Qn-2, a seventh switch Qn-3, and an eighth switch Qn-4. The (N−1) th  resonant cavity includes an (N−1) th  resonant capacitor Crn and an (N−1) th  resonant inductor Lrn. The startup module includes a converter and a target capacitor. 
     The first capacitor C 1 , the second capacitor C 2 , and the N th  capacitor Cn are sequentially connected in series. The first switch Q1-1 is connected in series to the third switch Q1-3, and the second switch Q1-2 is connected in series to the fourth switch Q1-4. The fifth switch Qn-1 is connected in series to the seventh switch Qn-3, and the sixth switch Qn-2 is connected in series to the eighth switch Qn-4. One end of the N th  capacitor Cn is connected to a first end of the sixth switch Qn-2, the other end of the N th  capacitor Cn is connected to a first end of the fifth switch Qn-1, and the other end of the N th  capacitor Cn is separately connected to one end of the second capacitor C 2  and a first end of the second switch Q1-2. A plurality of capacitors and a plurality of resonant circuits may be included between the N th  capacitor Cn and the second capacitor C 2 . The other end of the second capacitor C 2  is separately connected to one end of the first capacitor C 1 , a first end of the first switch Q1-1, and a first end of the converter. A second end of the converter is separately connected to one end of the target capacitor C 0 , a second end of the fourth switch Q1-4, and a second end of the eighth switch Qn-4. The other end of the first capacitor C 1  is connected to a third end of the converter, and a fourth end of the converter is separately connected to the other end of the target capacitor C 0 , a second end of the third switch Q1-3, and a second end of the seventh switch Qn-3. 
     One end of the first resonant cavity is separately connected to a second end of the first switch Q1-1 and a first end of the third switch Q1-3, and the other end of the first resonant cavity is separately connected to a second end of the second switch Q1-2 and a first end of the fourth switch Q1-4. One end of the (N−1) th  resonant cavity is separately connected to a second end of the fifth switch Qn-1 and a first end of the seventh switch Qn-3, and the other end of the (N−1) th  resonant cavity is separately connected to a second end of the sixth switch Qn-2 and a first end of the eighth switch Qn-4. 
     In this embodiment, the first resonant cavity may include the first resonant capacitor Cr 1  and the first resonant inductor Lr 1  that are connected in series; or may include the first resonant capacitor Cr 1  and the first resonant inductor Lr 1  that are connected in series, and another capacitor connected to both ends of the first resonant inductor Lr 1  as a whole. There are other types of equivalent forms. This is not limited herein. The (N−1) th  resonant cavity may include the (N−1) th  resonant capacitor Crn and the (N−1) th  resonant inductor Lrn that are connected in series; or may include the (N−1) th  resonant capacitor Crn and the (N−1) th  resonant inductor Lrn that are connected in series, and another capacitor connected to both ends of the (N−1) th  resonant inductor Lrn as a whole. There are other types of equivalent forms. This is not limited herein. 
     In this embodiment, when the switch is an NMOS, a first end of the switch is a drain electrode of the NMOS, a second end of the switch is a source electrode of the NMOS, a third end of the switch is a gate electrode of the NMOS, and the gate electrode is connected to a drive signal. The drive signal may be a pulse width modulation (PWM) signal. This is not limited herein. 
     In this embodiment, a duty cycle of driving of each switch is close to 50%, that is, a turn-on time of each switch is approximately half of one cycle, and the switch works at a resonance frequency of the resonant cavity or near the resonance frequency. It may be understood that, in actual application, a dead time needs to be reserved for an actual circuit, and therefore the duty cycle may be approximately 50%. 
     For ease of understanding, Table 1 is shown: 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Switch 
                 Q1-1 
                 Q1-2 
                 Q1-3 
                 Q1-4 
                 Qn-1 
                 Qn-2 
                 Qn-3 
                 Qn-4 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 State 1 
                 1 
                 1 
                 0 
                 0 
                 1 
                 1 
                 0 
                 0 
               
               
                 State 2 
                 1 
                 1 
                 0 
                 0 
                 0 
                 0 
                 1 
                 1 
               
               
                 State 3 
                 0 
                 0 
                 1 
                 1 
                 0 
                 0 
                 1 
                 1 
               
               
                 State 4 
                 0 
                 0 
                 1 
                 1 
                 1 
                 1 
                 0 
                 0 
               
               
                   
               
            
           
         
       
     
     Turn-on is 1, and turn-off is 0. The state 1 and the state 3 indicate that driving of each resonant circuit is in-phase (synchronous turn-on and turn-off), and the state 2 and the state 4 indicate that driving of each resonant circuit is out-of-phase (staggered turn-on and turn-off). 
     It may be understood that Table 1 is merely an example to illustrate turn-on and turn-off states of the switches. In actual application, when the first switch Q1-1 is turned on, the fifth switch Qn-1 may also be turned on. The four states described in Table 1 are not all states. The first switch Q1-1 and the third switch Q1-3 cannot be simultaneously turned on, the second switch Q1-2 and the fourth switch Q1-4 cannot be simultaneously turned on, the fifth switch Qn-1 and the seventh switch Qn-3 cannot be simultaneously turned on, and the sixth switch Qn-2 and the eighth switch Qn-4 cannot be simultaneously turned on. Other states are acceptable. Table 1 is merely an example and cannot be used as a limitation. 
     In this embodiment, when the input voltage Vin is connected to both ends of the capacitor module, and the output voltage Vo is the voltage at both ends of the first capacitor C 1 , a conduction status of each switch is controlled, so that the first capacitor C 1  may separately perform energy transmission with the second capacitor and the N th  capacitor Cn by using each resonant circuit, thereby balancing voltages at both ends of capacitors. Each resonant circuit may convert partial power and power conversion efficiency may be high. Further, a voltage gain N:1 is obtained based on a series voltage division principle of N capacitors of the capacitor module. In addition, on the one hand, because there is the converter, during power-on, the conversion circuit in this embodiment can normally implement slow startup. This effectively resolves a problem that a conventional resonant switched capacitor circuit cannot be controlled in a closed-loop manner and is not easy to implement slow startup. On the other hand, in case of overcurrent, the converter may be used to implement detection and protection. 
     1.2. The first capacitor C 1  and the second capacitor C 2  are connected in series and then connected in parallel to the N th  capacitor Cn. 
       FIG.  14    is a schematic diagram of a third embodiment of a conversion circuit according to an embodiment. An embodiment may provide a third embodiment of a conversion circuit. Components in this embodiment are similar to the components corresponding to  FIG.  13   , and details are not described herein. A difference lies in a connection manner of the N th  capacitor Cn. The following describes a structure. 
     The first capacitor C 1  and an (N−1) th  capacitor Cn- 1  are sequentially connected in series. One end of the N th  capacitor Cn is connected to a first end of the sixth switch Qn-2, and the other end of the N th  capacitor Cn is connected to the other end of the first capacitor C 1 . One end of the (N−1) th  capacitor Cn- 1  is connected to a first end of the fifth switch Qn-1, and a plurality of capacitors and a plurality of resonant circuits may be included between the first end of the fifth switch Qn-1 and the one end of the (N−1) th  capacitor Cn- 1 . The one end of the (N−1) th  capacitor Cn- 1  is further connected to a first end of the second switch Q1-2, and the other end of the (N−1) th  capacitor Cn- 1  is separately connected to a first end of the first switch Q1-1, one end of the first capacitor C 1 , and a first end of the converter. A second end of the converter is separately connected to one end of the target capacitor C 0 , a second end of the fourth switch Q1-4, and a second end of the eighth switch Qn-4. The other end of the first capacitor C 1  is separately connected to the other end of the N th  capacitor Cn and a third end of the converter, and a fourth end of the converter is separately connected to the other end of the target capacitor C 0 , a second end of the third switch Q1-3, and a second end of the seventh switch Qn-3. 
     In this embodiment, when the input voltage Vin is connected to both ends of the capacitor module, and the output voltage Vo is the voltage at both ends of the first capacitor C 1 , the circuit is a buck circuit, and a conduction status of each switch is controlled, so that the first capacitor C 1  may separately perform energy transmission with the (N−1) th  capacitor Cn- 1  and the (N−1) th  resonant capacitor Crn by using each resonant circuit, thereby balancing voltages at both ends of capacitors. Each resonant circuit may convert partial power and power conversion efficiency may be high. Further, a voltage gain N:1 is obtained based on a series voltage division principle of N−1 capacitors of the capacitor module and the N th  resonant capacitor Crn. In addition, on the one hand, because there is the converter, during power-on, the conversion circuit in this embodiment can normally implement slow startup. This effectively resolves a problem that a conventional resonant switched capacitor circuit cannot be controlled in a closed-loop manner and is not easy to implement slow startup. On the other hand, in case of overcurrent, the converter may be used to implement detection and protection. 
     1.3. The first capacitor C 1  and the (N−1) th  capacitor Cn- 1  are connected in series and then connected in parallel to a direct current power supply V_dc. 
       FIG.  15    is a schematic diagram of a fourth embodiment of a conversion circuit according to an embodiment. Components in this embodiment are similar to the components corresponding to  FIG.  14   , and details are not described herein. A difference lies in that the N th  capacitor Cn is replaced with the direct current power supply V_dc (as shown in  FIG.  15   ). 
     In this embodiment, when the input voltage Vin is connected to both ends of the capacitor module, and the output voltage Vo is the voltage at both ends of the first capacitor C 1 , the circuit is a buck circuit, and a conduction status of each switch is controlled, so that the first capacitor C 1  may separately perform energy transmission with the (N−1) th  capacitor Cn- 1  and the N th  resonant capacitor Crn by using each resonant circuit, thereby balancing voltages at both ends of capacitors. Further, a voltage gain N:1 is obtained based on a series voltage division principle of N−1 capacitors of the capacitor module and the N th  resonant capacitor Crn. In addition, on the one hand, because there is the converter, during power-on, the conversion circuit in this embodiment can normally implement slow startup. This effectively resolves a problem that a conventional resonant switched capacitor circuit cannot be controlled in a closed-loop manner and is not easy to implement slow startup. On the other hand, in case of overcurrent, the converter may be used to implement detection and protection. 
     For ease of understanding, the following uses N=3 as an example for detailed description. 
     2. A ratio of the input voltage to the output voltage is 3:1. 
     The capacitor module of the conversion circuit in this embodiment may have a plurality of forms, which are separately described below. 
     2.1. The first capacitor C 1 , the second capacitor C 2 , and a third capacitor C 3  are sequentially connected in series. 
       FIG.  16    is a schematic diagram of a fifth embodiment of a conversion circuit according to an embodiment. An embodiment may provide a fifth embodiment of a conversion circuit, including a capacitor module, a balancing module, and a startup module. The capacitor module includes a first capacitor C 1 , a second capacitor C 2 , and a third capacitor C 3 . The balancing module includes a first resonant circuit and a second resonant circuit. The startup module includes a converter and a target capacitor. 
     The first resonant circuit is separately connected to both ends of the first capacitor and the second capacitor, and the second resonant circuit is separately connected to both ends of the first capacitor and the third capacitor. 
     The first capacitor C 1 , the second capacitor C 2 , and the third capacitor C 3  are sequentially connected in series. A first switch Q1-1 is connected in series to a third switch Q1-3, and a second switch Q1-2 is connected in series to a fourth switch Q1-4. A fifth switch Q2-1 is connected in series to a seventh switch Q2-3, and a sixth switch Q2-2 is connected in series to an eighth switch Q2-4. One end of the third capacitor C 3  is connected to a first end of the sixth switch Q2-2, and the other end of the third capacitor C 3  is separately connected to a first end of the fifth switch Q2-1, one end of the second capacitor C 2 , and a first end of the second switch Q1-2. The other end of the second capacitor C 2  is separately connected to one end of the first capacitor C 1 , a first end of the first switch Q1-1, and a first end of the converter. A second end of the converter is separately connected to one end of the target capacitor C 0 , a second end of the fourth switch Q1-4, and a second end of the eighth switch Q2-4. The other end of the first capacitor C 1  is connected to a third end of the converter, and a fourth end of the converter is separately connected to the other end of the target capacitor C 0 , a second end of the third switch Q1-3, and a second end of the seventh switch Q2-3. 
     One end of a first resonant cavity is separately connected to a second end of the first switch Q1-1 and a first end of the third switch Q1-3, and the other end of the first resonant cavity is separately connected to a second end of the second switch Q1-2 and a first end of the fourth switch Q1-4. One end of a second resonant cavity is separately connected to a second end of the fifth switch Q2-1 and a first end of the seventh switch Q2-3, and the other end of the (N−1) th  resonant cavity is separately connected to a second end of the sixth switch Q2-2 and a first end of the eighth switch Q2-4. 
     In this embodiment, the first resonant cavity in which a first resonant capacitor Cr 1  and a first resonant inductor Lr 1  are connected in series is merely used as an example for illustration. It may be understood that, in actual application, the first resonant cavity may alternatively include the first resonant capacitor Cr 1  and the first resonant inductor Lr 1  that are connected in series, and another capacitor connected to both ends of the first resonant inductor Lr 1  as a whole. There are other types of equivalent forms. This is not limited herein. The second resonant cavity is similar to the first resonant cavity. There are other types of equivalent forms. This is not limited herein. 
     In this embodiment, a duty cycle of driving of each switch is close to 50%, that is, a turn-on time of each switch is approximately half of one cycle, and the switch works at a resonance frequency of the resonant cavity or near the resonance frequency. 
       FIG.  17    shows an embodiment in which the converter in the startup module in the embodiment shown in  FIG.  16    uses the structure of  FIG.  4   . 
     Some turn-on and turn-off states of the switches are shown in Table 1. For ease of understanding, a schematic diagram of in-phase driving of the switches in the first resonant circuit and the second resonant circuit is shown in  FIG.  18   , and a schematic diagram of out-of-phase driving of the switches in the first resonant circuit and the second resonant circuit is shown in  FIG.  19   . It may be understood that there may be any phase shifting angle, which is not limited herein. 
     A circuit working principle in this embodiment is as follows: 
     A complete cycle of the switches in this embodiment may include a first cycle and a second cycle. As shown in  FIG.  18    and  FIG.  19   , a complete cycle T includes a first cycle and a second cycle, and the first cycle and the second cycle account for approximately half of the complete cycle of the switches. In actual application, the complete cycle may include the first cycle, a dead time, and the second cycle. This is not limited herein. 
     The following describes in detail the working principle in this embodiment by using in-phase driving shown in  FIG.  18    and the converter using the structure of  FIG.  4    as an example. 
     2.1.1. First Cycle: 
       FIG.  17    may be equivalent to  FIG.  20   , when the first switch Q1-1, the second switch Q1-2, the fifth switch Q2-1, and the sixth switch Q2-2 are turned on (a high level is input), and the third switch Q1-3, the fourth switch Q1-4, the seventh switch Q2-3, and the eighth switch Q2-4 are turned off (a low level is input). The second capacitor C 2  performs energy transmission with the first resonant capacitor Cr 1 , and the third capacitor C 3  performs energy transmission with a second resonant capacitor Cr 2 . 
     2.1.2. Second Cycle: 
       FIG.  17    may be equivalent to  FIG.  21   , when the third switch Q1-3, the fourth switch Q1-4, the seventh switch Q2-3, and the eighth switch Q2-4 are turned on (a high level is input), and the first switch Q1-1, the second switch Q1-2, the fifth switch Q2-1, and the sixth switch Q2-2 are turned off (a low level is input). The first resonant capacitor Cr 1  and the second resonant capacitor Cr 2  perform energy transmission with the first capacitor C 1 . In this case, the first capacitor C 1  is an output capacitor. Because a duty cycle of a drive signal is close to 50%, a voltage at both ends of the first resonant capacitor Cr 1  is equal to a voltage at both ends of the second resonant capacitor Cr 2 . That is, a voltage at both ends of the first capacitor C 1  is equal to a voltage at both ends of the second capacitor C 2 , and the voltage at both ends of the first capacitor C 1  is equal to a voltage of the third capacitor C 3 . Further, because the first capacitor C 1 , the second capacitor C 2 , and the third capacitor C 3  are sequentially connected in series, and a total voltage is Vin, it may be understood, based on a series voltage division principle, that the voltage (output voltage Vo) at both ends of the first capacitor C 1  is one third of the input voltage Vin, that is, a ratio of the input voltage Vin to the output voltage Vo is 3:1. 
     In this embodiment, the input voltage Vin charges the first capacitor C 1  by using the first resonant cavity and the second resonant cavity. The balancing module balances the voltages at both ends of the first capacitor and the second capacitor by controlling the switches in the first resonant circuit in conjunction with influence of the first resonant cavity on a current. The balancing module balances the voltages at both ends of the first capacitor and the third capacitor by controlling the switches in the second resonant circuit in conjunction with influence of the second resonant cavity on a current. Further, a voltage gain 3:1 is obtained based on a series voltage division principle of the three capacitors of the capacitor module. In addition, on the one hand, because there is the converter (a buck circuit in  FIG.  17   ,  FIG.  20   , and  FIG.  21   ), during power-on, the conversion circuit in this embodiment can normally implement slow startup. This effectively resolves a problem that a conventional resonant switched capacitor circuit cannot be controlled in a closed-loop manner and is not easy to implement slow startup. On the other hand, in case of overcurrent, the converter may be used to implement detection and protection. 
     2.2. The first capacitor C 1  and the second capacitor C 2  are connected in series and then connected in parallel to the third capacitor C 3 . 
       FIG.  22    is a schematic diagram of a sixth embodiment of a conversion circuit according to an embodiment. An embodiment may provide a sixth embodiment of a conversion circuit. Components in this embodiment are similar to the components corresponding to  FIG.  16   , and details are not described herein. A difference lies in a connection manner of the third capacitor C 3 . The following describes a structure. 
     The first capacitor C 1  is connected in series to the second capacitor C 2 . One end of the third capacitor C 3  is connected to a first end of the sixth switch Q2-2, and the other end of the third capacitor C 3  is connected to the other end of the first capacitor C 1 . One end of the second capacitor C 2  is separately connected to a first end of the fifth switch Q2-1 and a first end of the second switch Q1-2, and the other end of the second capacitor C 2  is separately connected to a first end of the first switch Q1-1, one end of the first capacitor C 1 , and a first end of the converter. A second end of the converter is separately connected to one end of the target capacitor C 0 , a second end of the fourth switch Q1-4, and a second end of the eighth switch Q2-4. The other end of the first capacitor C 1  is separately connected to the other end of the third capacitor C 3  and a third end of the converter, and a fourth end of the converter is separately connected to the other end of the target capacitor C 0 , a second end of the third switch Q1-3, and a second end of the seventh switch Q2-3. 
     The following describes in detail the working principle in this embodiment by using in-phase driving shown in  FIG.  18    as an example. 
     2.2.1. First Cycle: 
       FIG.  22    may be equivalent to  FIG.  23   , when the first switch Q1-1, the second switch Q1-2, the fifth switch Q2-1, and the sixth switch Q2-2 are turned on (a high level is input), and the third switch Q1-3, the fourth switch Q1-4, the seventh switch Q2-3, and the eighth switch Q2-4 are turned off (a low level is input). The second capacitor C 2  transmits energy to the first resonant capacitor Cr 1 , Vin transmits energy to the second resonant capacitor Cr 2 , and the input voltage Vin charges the first capacitor C 1  by using the first resonant cavity and the second resonant cavity. 
     2.2.2. Second Cycle: 
       FIG.  22    may be equivalent to  FIG.  24   , when the third switch Q1-3, the fourth switch Q1-4, the seventh switch Q2-3, and the eighth switch Q2-4 are turned on (a high level is input), and the first switch Q1-1, the second switch Q1-2, the fifth switch Q2-1, and the sixth switch Q2-2 are turned off (a low level is input). The first resonant capacitor Cr 1  and the second resonant capacitor Cr 2  charge the first capacitor C 1 . In this case, the first capacitor C 1  is an output capacitor. Because a duty cycle of a drive signal is close to 50%, a voltage at both ends of the first resonant capacitor Cr 1 , a voltage at both ends of the second resonant capacitor Cr 2 , a voltage at both ends of the first capacitor C 1 , and a voltage at both ends of the second capacitor C 2  are equal. Further, because the first capacitor C 1 , the second capacitor C 2 , and the second resonant capacitor Cr 2  are sequentially connected in series, and a total voltage is Vin, it may be understood, based on a series voltage division principle, that the voltage (output voltage Vo) at both ends of the first capacitor C 1  is one third of the input voltage Vin, that is, a ratio of the input voltage Vin to the output voltage Vo is 3:1. In addition, on the one hand, because there is the converter, during power-on, the conversion circuit in this embodiment can normally implement slow startup. This effectively resolves a problem that a conventional resonant switched capacitor circuit cannot be controlled in a closed-loop manner and is not easy to implement slow startup. On the other hand, in case of overcurrent, the converter may be used to implement detection and protection. 
     2.3. The first capacitor C 1  and the second capacitor C 2  are connected in series and then connected in parallel to a direct current power supply V_dc. 
       FIG.  25    is a schematic diagram of a seventh embodiment of a conversion circuit according to an embodiment. An embodiment may provide a seventh embodiment of a conversion circuit. Components in this embodiment are similar to the components corresponding to  FIG.  22   , and details are not described herein. A difference lies in that the third capacitor C 3  is replaced with the direct current power supply V_dc (as shown in  FIG.  25   ). 
     In this embodiment, after the first switch Q1-1 and the second switch Q1-2 are turned on, the second capacitor C 2  performs energy transmission with the first resonant circuit; after the third switch Q1-3 and the fourth switch Q1-4 are turned on, the first resonant circuit performs energy transmission with the first capacitor C 1 ; after the fifth switch Q2-1 and the sixth switch Q2-2 are turned on, the direct current power supply V_dc performs energy transmission with the second resonant circuit; and after the seventh switch Q2-3 and the eighth switch Q2-4 are turned on, the second resonant circuit performs energy transmission with the first capacitor C 1 , so that a voltage gain is 3:1 (for a detailed principle, refer to the principle corresponding to  FIG.  23    and  FIG.  24   ). In addition, on the one hand, because there is the converter, during power-on, the conversion circuit in this embodiment can normally implement slow startup. This effectively resolves a problem that a conventional resonant switched capacitor circuit cannot be controlled in a closed-loop manner and is not easy to implement slow startup. On the other hand, in case of overcurrent, the converter may be used to implement detection and protection. 
     In addition to the form shown in  FIG.  3   , the first resonant circuit in this embodiment may have a plurality of structural forms, which are separately described below with reference to a connection between the first resonant circuit and a capacitor. 
     As shown in  FIG.  26   , a connection between a first resonant circuit in a structural form and a capacitor may include a first capacitor C 1 , a second capacitor C 2 , a first switch Q1-1, a second switch Q1-2, a third switch Q1-3, a fourth switch Q1-4, a first resonant capacitor Cr 1 , and a first resonant inductor Lr 1 . 
     The first switch Q1-1, the second switch Q1-2, the third switch Q1-3, and the fourth switch Q1-4 are sequentially connected in series. One end of the first resonant capacitor Cr 1  is separately connected to a second end of the first switch Q1-1 and a first end of the third switch Q1-3, and the other end of the first resonant capacitor Cr 1  is separately connected to a second end of the second switch Q1-2 and a first end of the fourth switch Q1-4. The first capacitor C 1  is connected in series to the second capacitor C 2 , and one end of the second capacitor C 2  is connected to a first end of the first switch Q1-1. One end of the first resonant inductor Lr 1  is separately connected to a second end of the third switch Q1-3 and a first end of the second switch Q1-2, and the other end of the first resonant inductor Lr 1  is separately connected to the other end of the second capacitor C 2  and one end of the first capacitor C 1 . The other end of the first capacitor C 1  is connected to a second end of the fourth switch Q1-4. 
     A working principle of the circuit shown in  FIG.  26    is similar to the descriptions corresponding to  FIG.  23    and  FIG.  24    in this embodiment. Details are not described herein. 
     As shown in  FIG.  27   , a connection between a first resonant circuit in another structural form and a capacitor may include a first capacitor C 1 , a second capacitor C 2 , a first switch Q1-1, a second switch Q1-2, a third switch Q1-3, a fourth switch Q1-4, a first resonant capacitor Cr 1 , and a first resonant inductor Lr 1 . 
     The first switch Q1-1, the second switch Q1-2, the third switch Q1-3, and the fourth switch Q1-4 are sequentially connected in series. The first capacitor C 1  is connected in series to the second capacitor C 2 , and the first resonant capacitor Cr 1  is connected in series to the first resonant inductor Lr 1 . One end of the second capacitor C 2  is connected to a first end of the first switch Q1-1, and the other end of the second capacitor C 2  is separately connected to a second end of the third switch Q1-3, a first end of the second switch Q1-2, and one end of the first capacitor C 1 . The other end of the first capacitor C 1  is connected to a second end of the fourth switch Q1-4. One end of the first resonant inductor Lr 1  is separately connected to a second end of the first switch Q1-1 and a first end of the third switch Q1-3, and the other end of the first resonant inductor Lr 1  is connected to one end of the first resonant capacitor Cr 1 . The other end of the first resonant capacitor Cr 1  is separately connected to a second end of the second switch Q1-2 and a first end of the fourth switch Q1-4. 
     A working principle of the circuit shown in  FIG.  27    is similar to the descriptions corresponding to  FIG.  23    and  FIG.  24    in this embodiment. Details are not described herein. 
     It may be understood that the first resonant circuit has a plurality of structures. The foregoing two structures are merely examples for description. A structure of the first resonant circuit is not limited herein. 
     As shown in  FIG.  28   , a schematic diagram of an eighth embodiment of a conversion circuit according to an embodiment may include a capacitor module and a balancing module. The balancing module includes a first resonant circuit and a second resonant circuit. The capacitor module includes a first capacitor C 1 , a second capacitor C 2 , and a third capacitor C 3 . 
     The first resonant circuit is separately connected to both ends of the first capacitor and the second capacitor, and the second resonant circuit is separately connected to both ends of the first capacitor and the third capacitor. 
     The first resonant circuit includes at least four switches and a first resonant cavity. The four switches are respectively a first switch Q1-1, a second switch Q1-2, a third switch Q1-3, and a fourth switch Q1-4. The first resonant cavity includes a first resonant capacitor Cr 1  and a first resonant inductor Lr 1 . The second resonant circuit includes at least four switches and a second resonant cavity. The four switches are respectively a fifth switch Q2-1, a sixth switch Q2-2, a seventh switch Q2-3, and an eighth switch Q2-4. The second resonant cavity includes a second resonant capacitor Cr 2  and a second resonant inductor Lr 2 . 
     The first capacitor C 1 , the second capacitor C 2 , and the third capacitor C 3  are sequentially connected in series. The first switch Q1-1 is connected in series to the third switch Q1-3, the second switch Q1-2 is connected in series to the fourth switch Q1-4, the fifth switch Q2-1 is connected in series to the seventh switch Q2-3, and the sixth switch Q2-2 is connected in series to the eighth switch Q2-4. One end of the third capacitor C 3  is connected to a first end of the fifth switch Q2-1, and the other end of the third capacitor C 3  is separately connected to a first end of the sixth switch Q2-2, a first end of the first switch Q1-1, and one end of the second capacitor C 2 . The other end of the second capacitor C 2  is separately connected to a first end of the second switch Q1-2, one end of the first capacitor C 1 , a second end of the third switch Q1-3, and a second end of the seventh switch Q2-3. The other end of the first capacitor C 1  is separately connected to a second end of the fourth switch Q1-4 and a second end of the eighth switch Q2-4. One end of the first resonant cavity is separately connected to a second end of the first switch Q1-1 and a first end of the third switch Q1-3, and the other end of the first resonant cavity is separately connected to a second end of the second switch Q1-2 and a first end of the fourth switch Q1-4. One end of the second resonant cavity is separately connected to a second end of the fifth switch Q2-1 and a first end of the seventh switch Q2-3, and the other end of the second resonant cavity is separately connected to a second end of the sixth switch Q2-2 and a first end of the eighth switch Q2-4. 
     In this embodiment, the first resonant cavity in which the first resonant capacitor Cr 1  and the first resonant inductor Lr 1  are connected in series may be used as an example for illustration. It may be understood that, in actual application, the first resonant cavity may alternatively include the first resonant capacitor Cr 1  and the first resonant inductor Lr 1  that are connected in series, and another capacitor connected to both ends of the first resonant inductor Lr 1  as a whole. There are other types of equivalent forms. This is not limited herein. The second resonant cavity is similar to the first resonant cavity. There are other types of equivalent forms. This is not limited herein. 
     In this embodiment, a duty cycle of driving of each switch may be close to 50%, that is, a turn-on time of each switch is approximately half of one cycle, and the switch works at a resonance frequency of the resonant cavity or near the resonance frequency. 
     Conduction statuses of the eight switches in this embodiment are similar to the conduction statuses of the eight switches shown in  FIG.  18    and  FIG.  19   . Details are not described herein. 
     The following provides a detailed description by using in-phase driving shown in  FIG.  18    as an example. 
     A circuit working principle in this embodiment is as follows: 
     First Cycle: 
       FIG.  28    may be equivalent to  FIG.  29   , when the first switch Q1-1, the second switch Q1-2, the fifth switch Q2-1, and the sixth switch Q2-2 are turned on (a high level is input), and the third switch Q1-3, the fourth switch Q1-4, the seventh switch Q2-3, and the eighth switch Q2-4 are turned off (a low level is input). The second capacitor C 2  performs energy transmission with the first resonant capacitor Cr 1 , the third capacitor C 3  performs energy transmission with the second resonant capacitor Cr 2 , and an input voltage Vin charges the first capacitor C 1  by using the first resonant cavity and the second resonant cavity. 
     Second Cycle: 
       FIG.  28    may be equivalent to  FIG.  30   , when the third switch Q1-3, the fourth switch Q1-4, the seventh switch Q2-3, and the eighth switch Q2-4 are turned on (a high level is input), and the first switch Q1-1, the second switch Q1-2, the fifth switch Q2-1, and the sixth switch Q2-2 are turned off (a low level is input). The first resonant capacitor Cr 1  and the second resonant capacitor Cr 2  charge the first capacitor C 1 . In this case, the first capacitor C 1  is an output capacitor. Because a duty cycle of a drive signal is close to 50%, a voltage at both ends of the first resonant capacitor Cr 1  is equal to a voltage at both ends of the second resonant capacitor Cr 2 . That is, a voltage at both ends of the first capacitor C 1  is equal to a voltage at both ends of the second capacitor C 2 , and the voltage at both ends of the first capacitor C 1  is equal to a voltage of the third capacitor C 3 . Further, because the first capacitor C 1 , the second capacitor C 2 , and the third capacitor C 3  are sequentially connected in series, and a total voltage is Vin, it may be understood, based on a series voltage division principle, that the voltage (output voltage Vo) at both ends of the first capacitor C 1  is one third of the input voltage Vin, that is, a ratio of the input voltage Vin to the output voltage Vo is 3:1. 
     In this embodiment, the balancing module balances the voltages at both ends of the first capacitor and the second capacitor by controlling the switches in the first resonant circuit in conjunction with influence of the first resonant cavity on a current. The balancing module balances the voltages at both ends of the first capacitor and the third capacitor by controlling the switches in the second resonant circuit in conjunction with influence of the second resonant cavity on a current. Further, a voltage gain 3:1 is obtained based on a series voltage division principle of the three capacitors of the capacitor module. 
     It may be understood from  FIG.  31    that all current waveforms are half sine waves, and all currents start from zero, then resonate, and end at zero. Therefore, the currents of the switches are all zero when the switches are turned on and turned off. That is, the switches work in a zero-current switch ZCS state. 
     For ease of understanding, the following uses N=4 as an example for description. 
     3. A ratio of the input voltage to the output voltage is 4:1. 
     The capacitor module of the conversion circuit in this embodiment may have a plurality of forms, which are separately described below. 
     3.1. The first capacitor C 1 , the second capacitor C 2 , the third capacitor C 3 , and a fourth capacitor C 4  are sequentially connected in series. 
       FIG.  32    is a schematic diagram of a ninth embodiment of a conversion circuit according to an embodiment. An embodiment may provide a ninth embodiment of a conversion circuit, including a capacitor module and a balancing module. 
     The balancing module includes a first resonant circuit, a second resonant circuit, and a third resonant circuit. The capacitor module includes a first capacitor C 1 , a second capacitor C 2 , a third capacitor C 3 , and a fourth capacitor C 4 . The first resonant circuit includes at least four switches and a first resonant cavity. The four switches are respectively a first switch Q1-1, a second switch Q1-2, a third switch Q1-3, and a fourth switch Q1-4. The first resonant cavity includes a first resonant capacitor Cr 1  and a first resonant inductor Lr 1 . The second resonant circuit includes at least four switches and a second resonant cavity. The four switches are respectively a fifth switch Q2-1, a sixth switch Q2-2, a seventh switch Q2-3, and an eighth switch Q2-4. The second resonant cavity includes a second resonant capacitor Cr 2  and a second resonant inductor Lr 2 . The third resonant circuit includes at least four switches and a third resonant cavity. The four switches are respectively a ninth switch Q3-1, a tenth switch Q3-2, an eleventh switch Q3-3, and a twelfth switch Q3-4. The third resonant cavity includes a third resonant capacitor Cr 3  and a third resonant inductor Lr 3 . 
     The first capacitor C 1 , the second capacitor C 2 , the third capacitor C 3 , and the fourth capacitor C 4  are sequentially connected in series. The first switch Q1-1 is connected in series to the third switch Q1-3, and the second switch Q1-2 is connected in series to the fourth switch Q1-4. The fifth switch Q2-1 is connected in series to the seventh switch Q2-3, and the sixth switch Q2-2 is connected in series to the eighth switch Q2-4. The ninth switch Q3-1 is connected in series to the eleventh switch Q3-3, and the tenth switch Q3-2 is connected in series to the twelfth switch Q3-4. 
     A first end of the ninth switch Q3-1 is connected to one end of the fourth capacitor C 4 , and a first end of the tenth switch Q3-2 is connected to the other end of the fourth capacitor C 4 . A first end of the fifth switch Q2-1 is connected to one end of the third capacitor C 3 , and a first end of the sixth switch Q2-2 is connected to the other end of the third capacitor C 3 . A first end of the first switch Q1-1 is connected to one end of the second capacitor C 2 , and a first end of the second switch Q1-2 is connected to the other end of the second capacitor C 2 . 
     One end of the first capacitor C 1  is separately connected to a second end of the eleventh switch Q3-3, a second end of the seventh switch Q2-3, and a second end of the third switch Q1-3. The other end of the first capacitor C 1  is separately connected to a second end of the twelfth switch Q3-4, a second end of the eighth switch Q2-4, and a second end of the fourth switch Q1-4. 
     One end of the first resonant cavity is separately connected to a second end of the first switch Q1-1 and a first end of the third switch Q1-3, and the other end of the first resonant cavity is separately connected to a second end of the second switch Q1-2 and the first end of the fourth switch Q1-4. One end of the second resonant cavity is separately connected to a second end of the fifth switch Q2-1 and a first end of the seventh switch Q2-3, and the other end of the second resonant cavity is separately connected to a second end of the sixth switch Q2-2 and the second end of the eighth switch Q2-4. One end of the third resonant cavity is separately connected to a second end of the ninth switch Q3-1 and a first end of the eleventh switch Q3-3, and the other end of the third resonant cavity is separately connected to a second end of the tenth switch Q3-2 and the second end of the twelfth switch Q3-4. 
     Similar to  FIG.  3   , the ninth switch Q3-1 and the eleventh switch Q3-3 in this embodiment may be replaced with diodes. 
     A working principle in this embodiment is similar to the principle in the embodiments shown in  FIG.  23    and  FIG.  24   . Details are not described herein. 
     3.2. The first capacitor C 1 , the second capacitor C 2 , and the third capacitor C 3  are connected in series and then connected in parallel to the fourth capacitor C 4 . 
       FIG.  33    is a schematic diagram of a tenth embodiment of a conversion circuit according to an embodiment. An embodiment may provide a tenth embodiment of a conversion circuit. Components in this embodiment are similar to the components corresponding to  FIG.  32   , and details are not described herein. A difference lies in a connection manner of the fourth capacitor C 4 . The following describes a structure. 
     The first capacitor C 1 , the second capacitor C 2 , and the third capacitor C 3  are connected in series and then connected in parallel to the fourth capacitor C 4 . The first switch Q1-1 is connected in series to the third switch Q1-3, and the second switch Q1-2 is connected in series to the fourth switch Q1-4. The fifth switch Q2-1 is connected in series to the seventh switch Q2-3, and the sixth switch Q2-2 is connected in series to the eighth switch Q2-4. The ninth switch Q3-1 is connected in series to the eleventh switch Q3-3, and the tenth switch Q3-2 is connected in series to the twelfth switch Q3-4. 
     A first end of the ninth switch Q3-1 is connected to one end of the fourth capacitor C 4 , and a first end of the tenth switch Q3-2 is separately connected to one end of the third capacitor C 3  and a first end of the fifth switch Q2-1. A first end of the sixth switch Q2-2 is connected to the other end of the third capacitor C 3 . A first end of the first switch Q1-1 is connected to one end of the second capacitor C 2 , and a first end of the second switch Q1-2 is connected to the other end of the second capacitor C 2 . 
     One end of the first capacitor C 1  is separately connected to a second end of the eleventh switch Q3-3, a second end of the seventh switch Q2-3, and a second end of the third switch Q1-3. The other end of the first capacitor C 1  is separately connected to a second end of the twelfth switch Q3-4, a second end of the eighth switch Q2-4, and a second end of the fourth switch Q1-4. 
     One end of the first resonant cavity is separately connected to a second end of the first switch Q1-1 and a first end of the third switch Q1-3, and the other end of the first resonant cavity is separately connected to a second end of the second switch Q1-2 and the second end of the fourth switch Q1-4. One end of the second resonant cavity is separately connected to a second end of the fifth switch Q2-1 and a first end of the seventh switch Q2-3, and the other end of the second resonant cavity is separately connected to a second end of the sixth switch Q2-2 and the second end of the eighth switch Q2-4. One end of the third resonant cavity is separately connected to a second end of the ninth switch Q3-1 and a first end of the eleventh switch Q3-3, and the other end of the third resonant cavity is separately connected to a second end of the tenth switch Q3-2 and the second end of the twelfth switch Q3-4. 
     A working principle in this embodiment is similar to the principle in the embodiments shown in  FIG.  23    and  FIG.  24   . Details are not described herein. A voltage gain may be 4:1. 
     3.3. The first capacitor C 1 , the second capacitor C 2 , and the third capacitor C 3  are connected in series and then connected in parallel to a direct current power supply V_dc. 
       FIG.  34    is a schematic diagram of an eleventh embodiment of a conversion circuit according to an embodiment. An embodiment may provide an eleventh embodiment of a conversion circuit. Components in this embodiment are similar to the components corresponding to  FIG.  33   , and details are not described herein. A difference lies in that the fourth capacitor C 4  is replaced with the direct current power supply V_dc (as shown in  FIG.  34   ). 
     A working principle in this embodiment is similar to the principle in the embodiments shown in  FIG.  23    and  FIG.  24   . Details are not described herein. A voltage gain may be 4:1. 
     The foregoing describes the buck conversion circuit. The following describes a boost conversion circuit. 
     II. Boost (a Voltage at Both Ends of a First Capacitor is an Input Voltage, and a Voltage at Both Ends of a Capacitor Module is an Output Voltage) 
     Components and connection relationships between the components in the boost conversion circuit are similar to the components and the connection relationships between the components in the buck conversion circuit. The components and the connection relationships between the components are not described in detail below. For boost and buck, Vin and Vo may be interchanged. The following describes a boost principle. 
     For ease of understanding, different transformation ratios are separately described below. 
     1. A ratio of the input voltage to the output voltage is 1:N. 
       FIG.  35    is a schematic diagram of a twelfth embodiment of a conversion circuit according to an embodiment. An embodiment may provide a twelfth embodiment of a conversion circuit. Components and connection relationships between the components in this embodiment are similar to the components and the connection relationships between the components corresponding to N:1, and details are not described herein. A difference lies in that Vin and Vo are interchanged (as shown in  FIG.  35   ). The following describes a boost conversion circuit that may correspond to the buck conversion circuit shown in  FIG.  13   , and boost conversion circuits corresponding to  FIG.  14    and  FIG.  15    are not described herein. 
     In this embodiment, when the input voltage Vin is connected to both ends of the first capacitor C 1 , and the output voltage Vo is a voltage at both ends of the capacitors C 1  to Cn that are connected in series, the circuit is a boost circuit. 
     In this embodiment, after the third switch Q1-3 and the fourth switch Q1-4 are turned on, the first capacitor C 1  charges the first resonant circuit; after the seventh switch Qn-3 and the eighth switch Qn-4 are turned on, the first capacitor C 1  charges the (N−1) th  resonant circuit; after the first switch Q1-1 and the second switch Q1-2 are turned on, the first resonant circuit charges the second capacitor C 2 ; and after the fifth switch Qn-1 and the sixth switch Qn-2 are turned on, the (N−1) th  resonant circuit charges the N th  capacitor Cn, so that a voltage at both ends of the N th  capacitor Cn is equal to a voltage at both ends of the first capacitor C 1 , and a voltage at both ends of the second capacitor C 2  is equal to the voltage at both ends of the first capacitor C 1 . Further, because the first capacitor C 1 , the second capacitor C 2 , and the N th  capacitor Cn are sequentially connected in series, the voltage at both ends of the first capacitor C 1  to the N th  capacitor Cn is N times the voltage at both ends of the first capacitor C 1 , so that the output voltage Vo is N times the input voltage Vin. That is, a voltage gain is N:1 (Vin:Vo=1:N). 
     For ease of understanding, the following also uses N=3 as an example for detailed description. 
     2. A ratio of the input voltage to the output voltage is 1:3. 
       FIG.  36    is a schematic diagram of a thirteenth embodiment of a conversion circuit according to an embodiment. An embodiment may provide a thirteenth embodiment of a conversion circuit. Components and connection relationships between the components in this embodiment are similar to the components and the connection relationships between the components corresponding to  FIG.  16   , and details are not described herein. A difference lies in that Vin and Vo are interchanged (as shown in  FIG.  36   ). The following describes a boost conversion circuit that may correspond to the buck conversion circuit shown in  FIG.  5   , and boost conversion circuits corresponding to  FIG.  22    and  FIG.  25    are not described herein. 
     The following describes in detail the working principle in this embodiment by using in-phase driving of the switches as an example. 
     2.1. First Cycle: 
       FIG.  36    may be equivalent to  FIG.  37   , when the third switch Q1-3, the fourth switch Q1-4, the seventh switch Q2-3, and the eighth switch Q2-4 are turned on (a high level is input), and the first switch Q1-1, the second switch Q1-2, the fifth switch Q2-1, and the sixth switch Q2-2 are turned off (a low level is input). The first capacitor C 1  charges the first resonant capacitor Cr 1 , and the first capacitor C 1  charges the second resonant capacitor Cr 2 . 
     2.2. Second Cycle: 
       FIG.  36    may be equivalent to  FIG.  38   , when the first switch Q1-1, the second switch Q1-2, the fifth switch Q2-1, and the sixth switch Q2-2 are turned on (a high level is input), and the third switch Q1-3, the fourth switch Q1-4, the seventh switch Q2-3, and the eighth switch Q2-4 are turned off (a low level is input). The first resonant capacitor Cr 1  charges the second capacitor C 2 , and the second resonant capacitor Cr 2  charges the third capacitor C 3 . In this case, the first capacitor C 1  is an input capacitor. Because a voltage at both ends of the first resonant capacitor Cr 1  is equal to a voltage at both ends of the first capacitor C 1 , and the first resonant capacitor Cr 1  charges the second capacitor C 2 , a voltage at both ends of the second capacitor C 2  is equal to the voltage at both ends of the first capacitor C 1 . Similarly, a voltage at both ends of the third capacitor C 3  is equal to the voltage at both ends of the first capacitor C 1 . That is, the voltage at both ends of the first capacitor C 1 , the voltage at both ends of the second capacitor C 2 , and the voltage at both ends of the third capacitor C 3  are equal. Therefore, a voltage at both ends of the first capacitor C 1  to the third capacitor C 3  is three times the voltage at both ends of the first capacitor C 1 , so that the output voltage Vo is three times the input voltage Vin. That is, a voltage gain is 1:3 (Vin:Vo=1:3). 
     For ease of understanding, the following also uses N=4 as an example for detailed description. 
     3. A ratio of the input voltage to the output voltage is 1:4. 
       FIG.  39    is a schematic diagram of a fourteenth embodiment of a conversion circuit according to an embodiment. An embodiment may provide a fourteenth embodiment of a conversion circuit. Components and connection relationships between the components in this embodiment are similar to the components and the connection relationships between the components corresponding to  FIG.  32   , and details are not described herein. A difference lies in that Vin and Vo are interchanged (as shown in  FIG.  39   ). The following describes a boost conversion circuit that may correspond to the buck conversion circuit shown in  FIG.  32   , and a boost conversion circuit (a schematic diagram of a fifteenth embodiment of a conversion circuit according to an embodiment, as shown in  FIG.  40   ) corresponding to  FIG.  33    and a boost conversion circuit (a schematic diagram of a sixteenth embodiment of a conversion circuit according to an embodiment, as shown in  FIG.  41   ) corresponding to  FIG.  34    are not described herein. 
     A principle is similar to the principle of 1:3, and details are not described herein. Similarly, a voltage at both ends of the third capacitor C 3  is equal to a voltage at both ends of the first capacitor C 1 , and a voltage at both ends of the fourth capacitor C 4  is equal to the voltage at both ends of the first capacitor C 1 . That is, the voltage at both ends of the first capacitor C 1 , the voltage at both ends of the second capacitor C 2 , the voltage at both ends of the third capacitor C 3 , and the voltage at both ends of the fourth capacitor C 4  are equal. Therefore, a voltage at both ends of the first capacitor C 1  to the fourth capacitor C 4  is four times the voltage at both ends of the first capacitor C 1 , so that the output voltage Vo is four times the input voltage Vin. That is, a voltage gain is 1:4 (Vin:Vo=1:4). 
     In the embodiments, energy transfer may be performed between the first capacitor C 1  and each resonant circuit, energy transfer is performed between each resonant circuit and another capacitor, and the duty cycle of each switch is approximately 50%, so that the voltage at both ends of the first capacitor C 1  is equal to a voltage at both ends of the another capacitor. In this way, a balanced voltage gain is obtained. Further, Vin and Vo are interchanged, so that the boost and buck principles are implemented. 
     In addition to the foregoing form, the conversion circuit in the embodiments may alternatively use a form in which quantities of components are increased, or another form, to implement the effect achieved in the embodiments. This is not limited herein. 
     In the embodiments, the second switch, the fourth switch, the sixth switch, the eighth switch, the tenth switch, and the twelfth switch may be NMOSs or IGBTs, and the first switch, the third switch, the fifth switch, the seventh switch, the ninth switch, and the eleventh switch may be diodes. 
     The conversion circuit in the embodiments may be applied to various electronic devices. For example, the power supply module shown in  FIG.  1    may be applied to an electronic device shown in  FIG.  42   . 
     As shown in  FIG.  42   , the electronic device may be any electronic device that includes a power supply module, such as a mobile phone, a tablet computer, a personal digital assistant (PDA), a point of sales (POS), or a vehicle-mounted computer. An example in which the electronic device is a mobile phone is used. 
       FIG.  42    shows a block diagram of a partial structure of a mobile phone related to the electronic device provided in the embodiments. As shown in  FIG.  42   , the mobile phone may include components such as a radio frequency (RF) circuit  1010 , a memory  1020 , an input unit  1030 , a display unit  1040 , a sensor  1050 , an audio circuit  1060 , a wireless fidelity (Wi-Fi) module  1070 , a processor  1080 , and a power supply module  1090 . Persons skilled in the art may understand that the structure of the mobile phone shown in  FIG.  42    does not constitute a limitation on the mobile phone, and the mobile phone may include more or fewer components than those shown in the figure, or combine some components, or have different component arrangements. 
     The following describes each component of the mobile phone with reference to  FIG.  42   . 
     The RF circuit  1010  may be configured to receive and send a signal in an information receiving and sending process or a call process. After receiving downlink information of a base station, the RF circuit  1010  sends the downlink information to the processor  1080  for processing. In addition, the RF circuit  1010  sends related uplink data to the base station. The RF circuit  1010  may include, but is not limited to, an antenna, at least one amplifier, a transceiver, a coupler, a low noise amplifier (LNA), a duplexer, and the like. In addition, the RF circuit  1010  may further communicate with a network and another device through wireless communication. The wireless communication may use any communication standard or protocol, including, but not limited to, the Global System for Mobile communications (GSM), a general packet radio service (GPRS), code division multiple access (CDMA), wideband code division multiple access (WCDMA), Long Term Evolution (LTE), an email, a short message service (SMS), and the like. 
     The memory  1020  may be configured to store a software program and a module. The processor  1080  performs various functional applications of the mobile phone and data processing by running the software program and the module that are stored in the memory  1020 . The memory  1020  may include a program storage area and a data storage area. The program storage area may store an operating system, an application required by at least one function (for example, a sound playing function or an image playing function), and the like. The data storage area may store data (for example, audio data or an address book) created based on use of the mobile phone, and the like. In addition, the memory  1020  may include a high-speed random access memory, or may include a nonvolatile memory, such as at least one magnetic disk storage device, a flash device, or another volatile solid-state storage device. 
     The input unit  1030  may be configured to receive input digital or character information and to generate key signal input related to user setting and function control of the mobile phone. The input unit  1030  may include a touch panel  1031  and another input device  1032 . The touch panel  1031 , also referred to as a touchscreen, may collect a touch operation of a user on or near the touch panel  1031  (for example, an operation performed by the user on or near the touch panel  1031  by using any suitable object or accessory such as a finger or a stylus) and drive a corresponding connecting apparatus based on a preset program. Optionally, the touch panel  1031  may include two parts: a touch detection apparatus and a touch controller. The touch detection apparatus detects a touch position of the user, detects a signal brought by the touch operation, and transmits the signal to the touch controller. The touch controller receives touch information from the touch detection apparatus, converts the touch information into contact coordinates, and sends the touch coordinates to the processor  1080 , and can receive and execute a command sent by the processor  1080 . In addition, the touch panel  1031  may be implemented by using a plurality of types, such as a resistive type, a capacitive type, an infrared ray type, and a surface acoustic wave type. In addition to the touch panel  1031 , the input unit  1030  may include the another input device  1032 . The another input device  1032  may include, but be not limited to, one or more of a physical keyboard, a functional key (such as a volume control key or an on/off key), a trackball, a mouse, or a joystick. 
     The display unit  1040  may be configured to display information entered by the user or information provided for the user and various menus of the mobile phone. The display unit  1040  may include a display panel  1041 . Optionally, the display panel  1041  may be configured in a form of a liquid crystal display (LCD), an organic light-emitting diode (OLED), or the like. Further, the touch panel  1031  may cover the display panel  1041 . After detecting a touch operation on or near the touch panel  1031 , the touch panel  1031  transmits the touch operation to the processor  1080  to determine a type of a touch event. Then, the processor  1080  provides corresponding visual output on the display panel  1041  based on the type of touch event. Although in  FIG.  42   , the touch panel  1031  and the display panel  1041  are used as two independent components to implement input and output functions of the mobile phone, in some embodiments, the touch panel  1031  and the display panel  1041  may be integrated to implement the input and output functions of the mobile phone. 
     The mobile phone may further include at least one type of sensor  1050 , for example, a light sensor, a motion sensor, and another sensor. The light sensor may include an ambient light sensor and a proximity sensor. The ambient light sensor may adjust brightness of the display panel  1041  based on intensity of ambient light. The proximity sensor may turn off the display panel  1041  and/or backlight when the mobile phone moves to an ear. As a type of movement sensor, an accelerometer sensor may detect a value of acceleration in each direction, such as on three axes, may detect a value and a direction of gravity in a stationary state, and may be used in an application for identifying a mobile phone posture (such as screen switching between a landscape mode and a portrait mode, a related game, or magnetometer posture calibration), a function related to vibration identification (such as a pedometer or a knock), or the like. Other sensors such as a gyroscope, a barometer, a hygrometer, a thermometer, or an infrared sensor may be further configured in the mobile phone. Details are not described herein. 
     The audio circuit  1060 , a speaker  1061 , and a microphone  1062  may provide an audio interface between the user and the mobile phone. The audio circuit  1060  may transmit an electrical signal converted from received audio data to the speaker  1061 , and the speaker  1061  converts the electrical signal into a sound signal for output. On the other hand, the microphone  1062  converts a collected sound signal into an electrical signal, and the audio circuit  1060  receives the electrical signal, converts the electrical signal into audio data, and then outputs the audio data to the processor  1080  for processing. Then, the processor  1080  sends the audio data to, for example, another mobile phone by using the RF circuit  1010 , or outputs the audio data to the memory  1020  for further processing. 
     Wi-Fi belongs to a short-range wireless transmission technology. The mobile phone may use the Wi-Fi module  1070  to help the user receive and send an email, browse a web page, access streaming media, and so on. The Wi-Fi module  1070  provides wireless broadband Internet access for the user. Although  FIG.  42    shows the Wi-Fi module  1070 , it may be understood that the Wi-Fi module  1070  is not a mandatory component of the mobile phone. 
     The processor  1080  is a control center of the mobile phone, is connected to various parts of the entire mobile phone by using various interfaces and lines, and performs various functions of the mobile phone and processes data by running or executing the software program and/or the module stored in the memory  1020  and invoking the data stored in the memory  1020 , to monitor the mobile phone as a whole. Optionally, the processor  1080  may include one or more processing units. The processor  1080  may integrate an application processor and a modem processor. The application processor may process an operating system, a user interface, an application, and the like. The modem processor may process wireless communication. It may be understood that the foregoing modem processor may be not integrated into the processor  1080 . 
     The mobile phone further includes a power supply  1090  (for example, a battery) that supplies power to each component. The power supply may be logically connected to the processor  1080  by using a power management system, to implement functions such as charging management, discharging management, and power consumption management by using the power management system. 
     Although not shown, the mobile phone may further include a camera, a Bluetooth module, and the like. Details are not described herein. 
     The conversion circuit provided in the embodiments is described in detail above. The principle and implementation are described herein through examples. The description of the embodiments is merely provided to help understand the method and ideas. In addition, persons of ordinary skill in the art can make variations and modifications. Therefore, the content of the embodiments shall not be construed as limiting.