Buck circuit and buck circuit control method

Abstract

The present application provides a buck circuit and a buck circuit control method. The buck circuit comprises a voltage input end, a voltage output end, a resonance unit, a first switch unit, and a second switch unit; the voltage input end is used for inputting a power supply voltage; the resonance unit comprises a resonant inductor and a resonant capacitor which are connected in series; the resonance unit is connected between the voltage input end and the voltage output end; the buck circuit has a charging stage and a buck output stage; in the charging stage, the first switch unit is turned on, the second switch unit is turned off, and the voltage input end charges the resonance unit and outputs the voltage output end; when the current in the buck circuit is zero, the buck circuit enters the buck output stage; and in the buck output stage, the first switch unit is turned off, the second switch unit is turned on, and the resonance unit outputs the voltage output end. According to the present application, the switching loss can be effectively reduced while the output voltage value is reduced.

Description

Buck circuit and buck circuit control method

[0001] This application claims priority to the Chinese patent application filed with the Patent Office of China on September 5, 2023, with application number 202311134471.7 and application name “Buck Circuit and Control Method of Buck Circuit”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of power electronic conversion, and in particular to a step-down circuit and a control method for the step-down circuit. Background Art

[0003] Currently, various converters are widely used in various fields to convert power at an input voltage into power at a desired output voltage. Based on their topology, they can be categorized as buck (step-down) circuits, boost (step-up) circuits, and buck-boost (step-down-boost) circuits. Buck circuits often adjust the output voltage by adjusting the duty cycle, thereby lowering the output voltage. However, adjusting the duty cycle to adjust the output voltage often results in significant switching losses. Therefore, how to reduce the output voltage while minimizing switching losses has become a critical issue.

[0004] Summary of the Invention

[0005] The present application provides a step-down circuit and a control method for the step-down circuit, which can effectively reduce switching losses while reducing the output voltage value.

[0006] In a first aspect, a buck circuit is provided, which includes a voltage input terminal, a voltage output terminal, a resonance unit, a first switch unit, and a second switch unit. The voltage input terminal is used to input a power supply voltage. The resonance unit includes a resonant inductor and a resonant capacitor connected in series. The resonance unit is connected between the voltage input terminal and the voltage output terminal. The buck circuit includes a charging stage and a buck output stage. In the charging stage, the first switch unit is turned on and the second switch unit is turned off. The power supply voltage input from the voltage input terminal charges the resonant unit and outputs to the voltage output terminal at the same time. When the current in the buck circuit is zero, the buck output stage is entered. In the buck output stage, the first switch unit is turned off and the second switch unit is turned on, and the resonance unit outputs to the voltage output terminal.

[0007] In a possible embodiment, the voltage input end includes an input positive pole and an input negative pole, the voltage output end includes an output positive pole and an output negative pole, the first switch unit includes a first switch and a second switch, and the second switch unit includes a third switch and a fourth switch, wherein the first switch is connected between the input positive pole and the first end of the resonance unit, the second switch is connected between the second end of the resonance unit and the output positive pole, the third switch is connected between the first end of the resonance unit and the output positive pole, one end of the fourth switch is connected to the second end of the resonance unit, and the other end of the fourth switch is connected to the output negative pole and the input negative pole.

[0008] In a possible implementation, in the charging stage, the first switch and the second switch are both turned on, and the third switch and the fourth switch are both turned off. The power supply voltage input to the input positive electrode charges the resonant unit through the turned-on first switch, and at the same time outputs the output positive electrode through the turned-on second switch, and the output negative electrode is connected to the input negative electrode, thereby forming a current loop in the charging stage; in the step-down output stage, the first switch and the second switch are both turned off, and the third switch and the fourth switch are both turned on. The first end of the resonant unit outputs the output positive electrode through the turned-on third switch, and the second end of the resonant unit is connected to the output negative electrode through the turned-on fourth switch, thereby forming a current loop in the step-down output stage.

[0009] In a possible embodiment, the buck circuit further includes a first diode, a second diode, a third diode and a fourth diode, wherein the first diode is connected in parallel with the first switch between the input positive electrode and the first end of the resonant unit, the second diode is connected in parallel with the second switch between the second end of the resonant unit and the output positive electrode, the third diode is connected in parallel with the third switch between the first end of the resonant unit and the output positive electrode, and the fourth diode is connected in parallel with the fourth switch between the second end of the resonant unit, the output negative electrode and the input negative electrode, wherein the conduction direction of the first diode is opposite to the current flow direction in the charging stage, the conduction direction of the second diode is the same as the current flow direction in the charging stage, the conduction direction of the third diode is opposite to the current flow direction in the buck output stage, and the conduction direction of the fourth diode is the same as the current flow direction in the buck output stage.

[0010] In a possible embodiment, the step-down circuit further includes a first voltage-stabilizing capacitor and a second voltage-stabilizing capacitor, the first voltage-stabilizing capacitor is connected to the input positive electrode and the input negative electrode, and the second voltage-stabilizing capacitor is connected to the output positive electrode and the output negative electrode. When the step-down circuit does not need to step down the voltage, the first switch, the second switch, the third switch and the fourth switch are all disconnected, and the first voltage-stabilizing capacitor and the second voltage-stabilizing capacitor output the voltage to the voltage output end. When the step-down circuit needs to step down the voltage, the step-down circuit performs a step-down operation through the charging stage and the step-down output stage.

[0011] In a possible implementation manner, the voltage input end is a DC voltage input end, and the voltage output end is a DC voltage output end.

[0012] In a second aspect, a control method for a buck circuit is further provided, which is applied to the buck circuit. The buck circuit includes a voltage input terminal, a voltage output terminal, a resonant unit, a first switch unit, and a second switch unit. The voltage input terminal is used to input a power supply voltage. The control method for the buck circuit includes:

[0013] Controlling the first switch unit to be turned on and controlling the second switch unit to be turned off, so that the buck circuit enters a charging phase, charging the resonant unit with the power supply voltage input through the voltage input terminal, and outputting the voltage to the voltage output terminal at the same time;

[0014] When the current in the buck circuit is zero, the first switch unit is controlled to be disconnected, and the second switch unit is controlled to be turned on, so that the buck circuit enters the buck output stage to output the voltage to the voltage output terminal through the resonant unit.

[0015] In a possible implementation, the voltage input end includes an input positive electrode and an input negative electrode, the voltage output end includes an output positive electrode and an output negative electrode, the first switch unit includes a first switch and a second switch, and the second switch unit includes a third switch and a fourth switch, wherein the first switch is connected between the input positive electrode and the first end A of the resonance unit, the second switch is connected between the second end of the resonance unit and the output positive electrode, the third switch is connected between the first end of the resonance unit and the output positive electrode, one end of the fourth switch is connected to the second end of the resonance unit, and the other end of the fourth switch is connected to the output negative electrode and the input negative electrode; controlling the first switch unit to be turned on and controlling the second switch unit to be turned off so that the buck circuit enters a charging stage, so as to charge the resonance unit through the power supply voltage input from the voltage input end and output to the voltage output end at the same time, comprises:

[0016] The first switch and the second switch are controlled to be turned on, and the third switch and the fourth switch are controlled to be turned off, so that the buck circuit enters the charging stage, and the resonant inductor and the resonant capacitor are charged with the power supply voltage input through the voltage input terminal, and the voltage output terminal is output at the same time.

[0017] In a possible implementation, when the current in the buck circuit is zero, controlling the first switch unit to be disconnected and controlling the second switch unit to be turned on, so that the buck circuit enters a buck output stage and outputs the voltage to the voltage output end through the resonant unit, includes:

[0018] When the resonant capacitor is fully charged, the current in the buck circuit is zero, the first switch and the third switch are controlled to be disconnected, and the second switch and the fourth switch are controlled to be turned on, so that the buck circuit enters the buck output stage to output the voltage to the output end through the resonant capacitor.

[0019] In one possible implementation, the step-down circuit further includes a first stabilizing capacitor and a second stabilizing capacitor, the first stabilizing capacitor being connected to the input positive electrode and the input negative electrode, and the second stabilizing capacitor being connected to the output positive electrode and the output negative electrode; and the step-down circuit control method further includes:

[0020] When the step-down circuit does not need to step down the voltage, the first switch, the second switch, the third switch and the fourth switch are all controlled to be disconnected, so as to output the voltage to the output terminal through the first stabilizing capacitor and the second stabilizing capacitor.

[0021] The buck circuit and control method of the buck circuit of the present application are provided with a voltage input terminal, a voltage output terminal, a resonant unit, a first switch unit, and a second switch unit. The voltage input terminal is used to input a power supply voltage. The resonant unit includes a resonant inductor and a resonant capacitor connected in series. The resonant unit is connected between the voltage input terminal and the voltage output terminal. The buck circuit has a charging stage and a buck output stage. In the charging stage, the first switch unit is turned on and the second switch unit is turned off. The voltage input terminal charges the resonant unit and outputs to the voltage output terminal. In the buck output stage, when the current in the buck circuit is zero, the buck output stage is entered. In the buck output stage, the first switch unit is turned off and the second switch unit is turned on. The resonant unit outputs to the voltage output terminal. While achieving a reduction in the output voltage value, each switch unit can be turned on or off when the current in the buck circuit is zero, effectively reducing switching losses. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the background technology, the drawings required for use in the embodiments of the present application or the background technology will be described below.

[0023] FIG1 is a schematic structural diagram of a step-down circuit in an embodiment of the present application.

[0024] FIG2 is a schematic structural diagram of the step-down circuit shown in FIG1 .

[0025] FIG3 is a circuit diagram of the step-down circuit shown in FIG2 .

[0026] FIG4 is a circuit diagram of the step-down circuit shown in FIG3 in a charging state.

[0027] FIG5 is a circuit diagram of the buck circuit shown in FIG3 in a buck output state.

[0028] FIG6 is a schematic structural diagram of a step-down circuit in another embodiment of the present application.

[0029] FIG7 is a schematic structural diagram of a step-down circuit in yet another embodiment of the present application.

[0030] FIG8 is a schematic structural diagram of the step-down circuit shown in FIG6 , which further includes a detection unit, a comparison unit, and a control unit.

[0031] FIG9 is a schematic structural diagram of the step-down circuit shown in FIG7 , which further includes a detection unit, a comparison unit, and a control unit.

[0032] FIG10 is a flow chart of a driving method of a buck circuit in an embodiment of the present application.

[0033] FIG11 is a flow chart of a driving method of a buck circuit in another embodiment of the present application.

[0034] FIG12 is a flow chart of a driving method of a buck circuit in yet another embodiment of the present application.

[0035] Explanation of the accompanying symbols: step-down circuit-1, voltage input terminal-10, input positive pole-VIN+, input negative pole-VIN-, voltage output terminal-20, output positive pole-VOUT+, output negative pole-VOUT-, resonant unit-30, resonant inductor-L1, resonant capacitor-C1, first terminal-A, second terminal-B, first switch unit-40, first switch-S1, second switch-S2, second switch unit-50, third switch-S3, fourth switch-S4, first diode-D1, second diode-D2, third diode-D3, fourth diode-D4, first voltage-stabilizing capacitor-C2, second voltage-stabilizing capacitor-C3, direct output path-60, third switch unit-70, detection unit-80, comparison unit-90, control unit-100. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0037] In the description of the embodiments of the present application, it should be noted that the terms "upper", "lower", "front", "back", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present application and simplifying the description, and do not imply or indicate that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present application.

[0038] In the description of the embodiments of this application, it should be noted that, unless otherwise specified or limited, the term "connection" should be understood in a broad sense. For example, it can mean a fixed connection, a detachable connection, or an integral connection; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0039] In the description of the embodiments of the present application, it should be noted that the terms "first", "second", "third", and "fourth" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", "third", and "fourth" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, unless otherwise specified, "multiple" means two or more.

[0040] Please refer to FIG1 , which is a schematic diagram of the structure of a buck circuit in an embodiment of the present application. As shown in FIG1 , the present application provides a buck circuit 1, which includes a voltage input terminal 10, a voltage output terminal 20, a resonant unit 30, a first switch unit 40, and a second switch unit 50. The voltage input terminal 10 is used to input a power supply voltage. The resonant unit 30 includes a resonant inductor L1 and a resonant capacitor C1 connected in series. The resonant unit 30 is connected between the voltage input terminal 10 and the voltage output terminal 20. The buck circuit 1 has a charging phase and a buck output phase. In the charging phase, the first switch unit 40 is turned on and the second switch unit 50 is turned off. The voltage input terminal 10 charges the resonant unit 30 and outputs power to the voltage output terminal 20. When the current in the buck circuit 1 is zero, the buck output phase is entered. In the buck output phase, the first switch unit 40 is turned off and the second switch unit 50 is turned on. The resonant unit 30 outputs power to the voltage output terminal 20.

[0041] Therefore, the above-mentioned buck circuit 1 in the present application can turn on or off each switching unit under the condition of zero current (Zero Current Switch, ZVS) while reducing the output voltage value, and realize the soft switching function through a simple circuit structure, thereby effectively reducing the switching loss.

[0042] In one or more embodiments, as shown in FIG1 , in the charging stage, the first switch unit 40 is turned on and the second switch unit 50 is turned off, connecting the current path from the voltage input terminal 10 through the resonance unit 30 to the voltage output terminal 20, and the power supply voltage input through the voltage input terminal 10 charges the resonant inductor L1 and the resonant capacitor C1 connected in series in the resonant unit 30, while the voltage input terminal 10 outputs the voltage to the voltage output terminal 20 through the resonant inductor L1 and the resonant capacitor C1; in the step-down output stage, when the current in the step-down circuit 1 is zero, the first switch unit 40 is turned off and the second switch unit 50 is turned on, connecting the current path from the resonant unit 30 to the voltage output terminal 20, and the electric energy charged in the charging stage through the resonant capacitor C1 in the resonant unit 30 is output to the voltage output terminal 20, thereby reducing the output voltage value.

[0043] Specifically, when entering the charging phase, no current flows through the buck circuit 1. For example, the buck circuit 1 may be in an initial state, having not yet entered the charging phase and the step-down output phase, or in an initial state after switching from the step-down output phase of the previous cycle to the charging phase of the current cycle. At this point, during the charging phase, the first switch unit 40 is turned on and the second switch unit 50 is turned off, both achieving soft switching under zero current conditions. This effectively reduces switching losses in the first and second switch units 40, 50, and the voltage input terminal 10 charges the resonant inductor L1 and the resonant capacitor C1. As charging progresses, all the electric energy in the resonant inductor L1 is transferred to the resonant capacitor C1, so that there is no electric energy stored in the resonant inductor L1, and the electric energy stored in the resonant capacitor C1 reaches its maximum value. That is, the voltage of the resonant capacitor C1 also reaches its maximum value, and the current in the buck circuit 1 drops to zero. At this time, the buck output stage is entered. In the buck output stage, the first switch unit 40 is disconnected and the second switch unit 50 is turned on, both of which can achieve soft switching function under zero current conditions, effectively reducing the switching losses of the first switch unit 40 and the second switch unit 50.

[0044] The resonant inductor L1 may be a winding inductor, a thin film inductor, a laminated inductor or other types of inductors, and the resonant capacitor C1 may be an electrolytic capacitor, a ceramic capacitor, a super capacitor or other types of capacitors.

[0045] Please refer to Figures 2 and 3 . Figure 2 is a schematic diagram of the structure of the buck circuit shown in Figure 1 , and Figure 3 is a schematic diagram of the circuit of the buck circuit shown in Figure 2 . As shown in Figures 2 and 3 , the voltage input terminal 10 includes a positive input electrode VIN+ and a negative input electrode VIN-, the voltage output terminal 20 includes a positive output electrode VOUT+ and a negative output electrode VOUT-, the first switch unit 40 includes a first switch S1 and a second switch S2, and the second switch unit 50 includes a third switch S3 and a fourth switch S4. The first switch S1 is connected between the positive input electrode VIN+ and the first terminal A of the resonance unit 30 , the second switch S2 is connected between the second terminal B of the resonance unit 30 and the positive output electrode VOUT+, the third switch S3 is connected between the first terminal A of the resonance unit 30 and the positive output electrode VOUT+, and the fourth switch S4 has one end connected to the second terminal B of the resonance unit 30 and the other end connected to the negative output electrode VOUT- and the negative input electrode VIN-.

[0046] Thus, the current path from the input positive electrode VIN+, the first switch S1, the resonance unit 30, the second switch S2, the output positive electrode VOUT+, the output negative electrode VOUT- to the input negative electrode VIN- is controllably connected, and the current path from the first end A of the resonance unit 30, the third switch S3, the output positive electrode VOUT+, the output negative electrode VOUT-, the fourth switch S4 to the second end B of the resonance unit 30 is controllably connected.

[0047] In one or more embodiments, the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 may be a metal oxide semiconductor FET (MOSFET), an insulated-gate bipolar transistor (IGBT), or other controllable switching devices, as long as the on and off functions of the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 can be realized.

[0048] Please refer to Figures 4 and 5 together. Figure 4 is a schematic diagram of the buck circuit shown in Figure 3 in the charging state, and Figure 5 is a schematic diagram of the buck circuit shown in Figure 3 in the buck output state. As shown in Figure 4, during the charging phase, the first switch S1 and the second switch S2 are both turned on, and the third switch S3 and the fourth switch S4 are both turned off. The power supply voltage input to the positive input terminal VIN+ charges the resonant unit 30 through the turned-on first switch S1, and the positive output terminal VOUT+ is output through the turned-on second switch S2, and the negative output terminal VOUT- is connected to the negative input terminal VIN-, thereby forming a current loop in the charging phase. As shown in Figure 5, during the buck output phase, the first switch S1 and the second switch S2 are both turned off, and the third switch S3 and the fourth switch S4 are both turned on. The first terminal A of the resonant unit 30 outputs the positive output terminal VOUT+ through the turned-on third switch S3, and the second terminal B of the resonant unit 30 is connected to the negative output terminal VOUT- through the turned-on fourth switch S4, thereby forming a current loop in the buck output phase.

[0049] Thus, in the charging phase, a current loop is connected from the input positive electrode VIN+, the first switch S1, the resonant unit 30, the second switch S2, the output positive electrode VOUT+, the output negative electrode VOUT- to the input negative electrode VIN-; and in the step-down output phase, a current loop is connected from the first end A of the resonant unit 30, the third switch S3, the output positive electrode VOUT+, the output negative electrode VOUT-, the fourth switch S4 to the second end B of the resonant unit 30.

[0050] As shown in FIG4 , the resonant inductor L1 can be closer to the first end A of the resonant unit 30 than the resonant capacitor C1, so that in the charging stage, the first switch S1 and the second switch S2 are both turned on, and the third switch S3 and the fourth switch S4 are both turned off. The power supply voltage input to the positive input electrode VIN+ can charge the resonant inductor L1 and the resonant capacitor C1 connected in series in the resonant unit 30 through the turned-on first switch S1, and at the same time output the positive output electrode VOUT+ through the turned-on second switch S2.

[0051] As shown in FIG5 , the resonant inductor L1 can be closer to the first end A of the resonant unit 30 than the resonant capacitor C1, so that in the step-down output stage, the first switch S1 and the second switch S2 are both disconnected, and the third switch S3 and the fourth switch S4 are both turned on. The resonant capacitor C1 in the resonant unit 30 can output to the positive output electrode VOUT+ through the first end A of the resonant unit 30 and the turned-on third switch S3 in sequence.

[0052] In one or more embodiments, the resonant inductor L1 may also be further away from the first end A of the resonant unit 30 than the resonant capacitor C1 .

[0053] As shown in Figures 3, 4 and 5, the buck circuit 1 further includes a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4. The first diode D1 is connected in parallel with the first switch S1 between the input positive electrode VIN+ and the first end A of the resonance unit 30. The second diode D2 is connected in parallel with the second switch S2 between the second end B of the resonance unit 30 and the output positive electrode VOUT+. The third diode D3 is connected in parallel with the third switch S3 between the first end A of the resonance unit 30 and the output positive electrode VOUT+. The fourth diode D4 is connected in parallel with the fourth switch S4 between the second end B of the resonance unit 30, the output negative electrode VOUT- and the input negative electrode VIN-. The conduction direction of the first diode D1 is opposite to the current flow direction in the charging stage, the conduction direction of the second diode D2 is the same as the current flow direction in the charging stage, the conduction direction of the third diode D3 is opposite to the current flow direction in the buck output stage, and the conduction direction of the fourth diode D4 is the same as the current flow direction in the buck output stage.

[0054] Thus, by providing the first diode D1, the second diode D2, the third diode D3, and the fourth diode D4, at least some of the diodes can prevent the buck circuit 1 from conducting in the reverse direction during the charging stage or the step-down output stage. By connecting the first diode D1, the second diode D2, the third diode D3, and the fourth diode D4 in parallel with the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4, respectively, the effect of reducing the output voltage value can be achieved with fewer switching devices and current branches. At the same time, by setting the conduction direction of the first diode D1, the second diode D2, the third diode D3, and the fourth diode D4, when the switches connected in parallel with these diodes are disconnected, the current loop corresponding to the buck circuit 1 during the charging stage or the step-down output stage can be connected as needed.

[0055] The conduction direction of the first diode D1 , the second diode D2 , the third diode D3 and the fourth diode D4 is a unidirectional conduction direction from the anode to the cathode of each diode D1 , the second diode D2 , the third diode D3 and the fourth diode D4 .

[0056] In one or more embodiments, the first diode D1, the second diode D2, the third diode D3 and the fourth diode D4 can be various types of ordinary diodes that are only used to achieve a unidirectional conduction function, or they can be various types of Zener diodes (ZD), Schottky diodes (SBD), fast recovery diodes (FRD), unidirectional transient voltage suppressors (TVS) or other semiconductor devices with unidirectional conduction characteristics.

[0057] As shown in FIG3 , FIG4 and FIG5 , the first diode D1 , the second diode D2 , the third diode D3 and the fourth diode D4 may be ordinary diodes used only for achieving a unidirectional conduction function.

[0058] Please refer to Figures 3, 4 and 5 again. The buck circuit 1 also includes a first stabilizing capacitor C2 and a second stabilizing capacitor C3. The first stabilizing capacitor C2 is connected to the input positive electrode VIN+ and the input negative electrode VIN-, and the second stabilizing capacitor C3 is connected to the output positive electrode VOUT+ and the output negative electrode VOUT-. When the buck circuit 1 does not need to step down the voltage, the first switch S1, the second switch S2, the third switch S3 and the fourth switch S4 are all disconnected, and the first stabilizing capacitor C2 and the second stabilizing capacitor C3 output the voltage to the voltage output terminal 20. When the buck circuit 1 needs to step down the voltage, the buck circuit 1 performs the step-down operation through a charging stage and a step-down output stage.

[0059] Thus, while the step-down circuit 1 reduces the output voltage value, by setting the first voltage-stabilizing capacitor C2 and the second voltage-stabilizing capacitor C3 in the step-down circuit 1, the voltage output terminal 20 is output through the first voltage-stabilizing capacitor C2 and the second voltage-stabilizing capacitor C3 when the step-down circuit 1 does not need to perform voltage reduction. The first voltage-stabilizing capacitor C2 and the second voltage-stabilizing capacitor C3 can also reduce the ripple current, making the input and output more stable.

[0060] Please refer to Figures 6 and 7. Figure 6 is a schematic diagram of the structure of a step-down circuit in another embodiment of the present application, and Figure 7 is a schematic diagram of the structure of a step-down circuit in yet another embodiment of the present application. As shown in Figures 6 and 7, the step-down circuit 1 may further include a direct output path 60 connected between the voltage input terminal 10 and the voltage output terminal 20. When the step-down circuit 1 does not need to step down the voltage, the direct output path 60 is turned on to directly output the power supply voltage input from the voltage input terminal 10 to the voltage output terminal 20. When the step-down circuit 1 needs to step down the voltage, the direct output path 60 is turned off, and the step-down circuit 1 performs the step-down operation through the charging phase and the step-down output phase.

[0061] Thus, while the step-down circuit 1 reduces the output voltage value, by setting a direct output path 60 in the step-down circuit 1, the power supply voltage input from the voltage input terminal 10 in the step-down circuit 1 can be directly output to the voltage output terminal 20. When the step-down circuit 1 does not need to reduce the voltage, there is no need to set an additional output path outside the step-down circuit 1.

[0062] In one or more embodiments, the direct output path 60 may connect a current path from the voltage input terminal 10 to the voltage output terminal 20 through the third switch unit 70 .

[0063] As shown in FIG6 , the third switch unit 70 can be connected to the voltage input terminal 10, the first switch unit 40, and the voltage output terminal 20. The third switch unit 70 can be a switch device such as a single-pole double-throw switch that can be controlled to select a path. Specifically, when the buck circuit 1 does not need to step down the voltage, the first switch unit 40 and the second switch unit 50 are both disconnected, and the voltage input terminal 10 is selected and connected to the current path of the voltage output terminal 20 through the third switch unit 70, that is, the direct output path 60 is turned on to directly output the power supply voltage input from the voltage input terminal 10 to the voltage output terminal 20; and when the buck circuit 1 needs to step down the voltage, it enters the charging stage, the first switch unit 40 is turned on, the second switch unit 50 is disconnected, and the voltage input terminal 10 is selected and connected to the first switch unit 40, the resonance unit 30, and the voltage output terminal 20 through the third switch unit 70. The current path of the output terminal 20 is disconnected, that is, the direct output path 60 is disconnected, and the resonant inductor L1 and the resonant capacitor C1 connected in series in the resonant unit 30 are charged through the power supply voltage input from the voltage input terminal 10, and output is performed to the voltage output terminal 20 at the same time; then, when the current in the buck circuit 1 is zero, the buck output stage is entered, the first switch unit 40 is disconnected, the second switch unit 50 is turned on, and the third switch unit 70 is disconnected, that is, the direct output path 60 is disconnected, and the resonant unit 30 is connected to the current path of the voltage output terminal 20 through the turned-on second switch unit 50, and output is performed to the voltage output terminal 20.

[0064] As shown in FIG7 , the third switch unit 70 can also be connected to the voltage input terminal 10 and the voltage output terminal 20. The third switch unit 70 can be a switch device of the same type as the first switch unit 40 and the second switch unit 50. For example, the third switch unit 70 can be a controllable switch device such as a MOS (Metal Oxide Semiconductor) transistor or a BJT (Bipolar junction transistor). Specifically, when the buck circuit 1 does not need to step down the voltage, the first switch unit 40 and the second switch unit 50 are both disconnected, the third switch unit 70 is turned on, and the voltage input terminal 10 is connected to the current path of the voltage output terminal 20 through the turned-on third switch unit 70, that is, the direct output path 60 is turned on to directly output the power supply voltage input from the voltage input terminal 10 to the voltage output terminal 20; and when the buck circuit 1 needs to step down the voltage and enters the charging stage, the first switch unit 40 is turned on, the second switch unit 50 is disconnected, and the third switch unit 70 is disconnected, that is, the direct output path 60 is disconnected, and the voltage input terminal 10 is connected to the current path of the voltage output terminal 20 through the turned-on third switch unit 70. A switch unit 40 is connected to the current path of the resonant unit 30 and the voltage output terminal 20, and the power supply voltage input from the voltage input terminal 10 is used to charge the resonant inductor L1 and the resonant capacitor C1 connected in series in the resonant unit 30, and output to the voltage output terminal 20 at the same time; then, when the current in the buck circuit 1 is zero, it enters the buck output stage, the first switch unit 40 is disconnected, the second switch unit 50 is turned on, and the third switch unit 70 is disconnected, that is, the direct output path 60 is disconnected, and the resonant unit 30 is connected to the current path of the voltage output terminal 20 through the turned-on second switch unit 50, and outputs to the voltage output terminal 20.

[0065] Please refer to Figures 8 and 9 together. Figure 8 is a schematic diagram of the structure of the step-down circuit shown in Figure 6, which further includes a detection unit, a comparison unit, and a control unit. Figure 9 is a schematic diagram of the structure of the step-down circuit shown in Figure 7, which further includes a detection unit, a comparison unit, and a control unit. As shown in Figures 8 and 9, the step-down circuit 1 may further include a detection unit 80, a comparison unit 90, and a control unit 100. The detection unit 80 is connected to the voltage output terminal 20 and is used to detect the average output voltage value over a period of time. The comparison unit 90 is connected to the detection unit 80 and is used to compare the average output voltage value with a preset voltage value to determine whether the step-down circuit 1 needs to step down. The control unit 100 is connected to the comparison unit 90 and is connected to each switch unit to control the conduction or disconnection of each switch unit in the step-down circuit 1.

[0066] Therefore, the control unit 100 can be used to control the on / off of each switch unit, and the on / off of each switch unit in the buck circuit 1 can be flexibly controlled.

[0067] In one or more embodiments, the detection unit 80 can be a voltmeter, or other voltage detection devices such as a voltage sensor, or a voltage detection circuit composed of components such as resistors, capacitors, and diodes, as long as it can detect the average output voltage value over a period of time.

[0068] In one or more embodiments, the comparison unit 90 can be a voltage comparator or other device capable of comparing voltage values, as long as it can receive the average output voltage value detected by the detection unit 80 over a period of time and compare it with the preset voltage value to determine whether the buck circuit 1 needs to step down.

[0069] When the average output voltage value over a period of time is higher than the preset voltage value, it is determined that the step-down circuit 1 needs to step down the voltage, and when the average output voltage value over a period of time is not higher than the preset voltage value, it is determined that the step-down circuit 1 does not need to step down the voltage.

[0070] Among them, the preset voltage value can be set according to the usage scenario and specific needs, the length of a period of time can be set according to the usage scenario and specific needs, and can also be the length of time that the buck circuit 1 is in the buck output stage.

[0071] In one or more embodiments, the buck circuit 1 may further include a current monitoring unit, which is arranged in the current loop of the buck circuit 1 in the charging stage and the buck output stage, and is used to monitor the zero current moment and generate a zero current signal. The control unit 100 receives the zero current signal of the current detection unit, determines that the conditions for switching the switch unit are currently met, and controls each switch unit to switch to the on or off state.

[0072] In one or more embodiments, the buck circuit 1 may further include a timing trigger unit, which is arranged in the current loop of the buck circuit 1 in the charging stage and the buck output stage, and is used to generate a trigger signal after a preset time. The control unit 100 receives the trigger signal of the timing trigger unit, determines whether the conditions for switching the switch unit are currently met, and controls the switching of each switch unit to the on or off state.

[0073] In one or more embodiments, as shown in FIG8 , the third switch unit 70 can be connected to the voltage input terminal 10, the first switch unit 40, and the voltage output terminal 20. The third switch unit 70 can be a selection switch, and the first switch unit 40 and the second switch unit 50 can be N-type MOS transistors. The control unit 100 is connected to the first switch unit 40, the second switch unit 50, and the third switch unit 70. After receiving the signal that the buck circuit 1 does not need to step down, it outputs a low level to control the first switch unit 40 and the second switch unit 50 to be disconnected. The control unit 100 controls the third switch unit 70 to select and connect the current path from the voltage input terminal 10 to the voltage output terminal 20, that is, to turn on the direct output path 60. After receiving the signal that the buck circuit 1 needs to step down, it enters the charging stage, outputs a high level to control the first switch unit 40 to be turned on, and outputs a low level to control The second switch unit 50 is disconnected, and the control unit 100 controls the third switch unit 70 to select and connect the current path from the voltage input terminal 10, the first switch unit 40, the resonance unit 30 to the voltage output terminal 20; when the current in the buck circuit 1 is zero, it enters the buck output stage. In the buck output stage, the output low level controls the first switch unit 40 to be disconnected, and the output high level controls the second switch unit 50 to be turned on. The control unit 100 controls the third switch unit 70 to be disconnected, and connects the current path from the resonance unit 30, the second switch unit 50 to the voltage output terminal 20.

[0074] In one or more embodiments, as shown in FIG9 , the third switch unit 70 may also be connected to the voltage input terminal 10 and the voltage output terminal 20 , and the first switch unit 40 , the second switch unit 50 and the third switch unit 70 may all be N-type MOS transistors. The control unit 100 is connected to the first switch unit 40, the second switch unit 50, and the third switch unit 70. At this time, after receiving a signal that the buck circuit 1 does not need to step down, the control unit 100 outputs a low level to control the first switch unit 40 and the second switch unit 50 to be disconnected, and outputs a high level to control the third switch unit 70 to be turned on, that is, to turn on the direct output path 60. After receiving a signal that the buck circuit 1 needs to step down, it enters the charging phase, outputs a high level to control the first switch unit 40 to be turned on, and outputs a low level to control the second switch unit 50 to be turned off, and outputs a low level to control the third switch unit 70 to be turned off, thereby connecting the current path from the voltage input terminal 10, the first switch unit 40, the resonant unit 30 to the voltage output terminal 20. When the current in the buck circuit 1 is zero, it enters the buck output phase. In the buck output phase, the control unit 100 outputs a low level to control the first switch unit 40 to be turned off, outputs a high level to control the second switch unit 50 to be turned on, and outputs a low level to control the third switch unit 70 to be turned off, thereby connecting the current path from the resonant unit 30, the second switch unit 50 to the voltage output terminal 20.

[0075] In one or more embodiments, the first switch unit 40, the second switch unit 50 and the third switch unit 70 may also be P-type MOS transistors. In this case, the control unit 100 outputs a low level to control each switch unit to be turned on, and outputs a high level to control each switch unit to be turned off.

[0076] In one or more embodiments, the first switch unit 40 may include a first switch S1 and a second switch S2, and the second switch unit 50 may include a third switch S3 and a fourth switch S4. The first switch S1, the second switch S2, the third switch S3 and the fourth switch S4 may be N-type MOS transistors or P-type MOS transistors.

[0077] Among them, the control unit 100 can be a general-purpose processor such as a central processing unit (CPU), or it can be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic devices, discrete gate logic devices, transistor logic devices and other logic control devices, or it can be a microprocessor such as a micro control unit 100 (MCU), as long as it can receive a signal indicating whether the buck circuit 1 needs to step down and / or a zero current signal and / or a timing trigger signal and control the conduction or disconnection of each switching unit.

[0078] In one or more embodiments, the voltage input terminal 10 is a DC voltage input terminal, and the voltage output terminal 20 is a DC voltage output terminal.

[0079] Therefore, the step-down circuit 1 is a DC / DC converter, which can convert a higher DC voltage into a lower DC voltage, thereby reducing the output voltage value.

[0080] The step-down circuit 1 of the present application can use fewer switching devices and current branches to controllably convert a higher DC voltage into a lower DC voltage through the above-mentioned structure, thereby reducing the output voltage value and allowing direct output. The circuit structure is simple and the cost is low. At the same time, each switching unit is turned on or off under zero current conditions, realizing a soft switching function, thereby effectively reducing switching losses.

[0081] The present application also provides a driving method of a buck circuit 1, which is applied to the buck circuit 1. As shown in Figure 1, the buck circuit 1 includes a voltage input terminal 10, a voltage output terminal 20, a resonant unit 30, a first switching unit 40 and a second switching unit 50, and the voltage input terminal 10 is used to input a power supply voltage.

[0082] Please refer to FIG10, which is a flow chart of a driving method of a buck circuit in an embodiment of the present application. As shown in FIG10, the control method of the buck circuit 1 includes:

[0083] Step S10, controlling the first switch unit to be turned on and the second switch unit to be turned off, so that the buck circuit enters a charging phase, charging the resonant unit with the power supply voltage input through the voltage input terminal, and outputting the voltage to the voltage output terminal at the same time;

[0084] Step S20, when the current in the buck circuit is zero, controlling the first switch unit to be disconnected, and controlling the second switch unit to be turned on, so that the buck circuit enters the buck output stage, and outputs to the voltage output end through the resonant unit.

[0085] Thus, in the charging stage, the current path from the voltage input terminal 10 through the resonance unit 30 to the voltage output terminal 20 is connected, so that the resonance unit 30 is charged through the voltage input terminal 10 and the voltage output terminal 20 is output at the same time; and in the step-down output stage, the current path from the resonance unit 30 to the voltage output terminal 20 is connected, so that the electric energy charged by the resonant capacitor C1 in the resonance unit 30 in the charging stage is output to the voltage output terminal 20, thereby reducing the output voltage value.

[0086] As shown in Figures 2 and 3, the voltage input terminal 10 of the buck circuit 1 includes an input positive electrode VIN+ and an input negative electrode VIN-, the voltage output terminal 20 includes an output positive electrode VOUT+ and an output negative electrode VOUT-, the first switch unit 40 includes a first switch S1 and a second switch S2, and the second switch unit 50 includes a third switch S3 and a fourth switch S4, wherein the first switch S1 is connected between the input positive electrode VIN+ and the first end A of the resonance unit 30, the second switch S2 is connected between the second end B of the resonance unit 30 and the output positive electrode VOUT+, the third switch S3 is connected between the first end A of the resonance unit 30 and the output positive electrode VOUT+, one end of the fourth switch S4 is connected to the second end B of the resonance unit 30, and the other end of the fourth switch S4 is connected to the output negative electrode VOUT- and the input negative electrode VIN-.

[0087] Please also refer to FIG11, which is a flow chart of a driving method of a buck circuit in another embodiment of the present application. As shown in FIG11, compared to FIG10, step S10 controls the first switch unit to be turned on and the second switch unit to be turned off, so that the buck circuit enters a charging phase, charging the resonant unit through the power supply voltage inputted from the voltage input terminal, and outputting the voltage to the voltage output terminal at the same time, including:

[0088] S100, controlling the first switch and the second switch to be turned on, and controlling the third switch and the fourth switch to be turned off, so that the buck circuit enters a charging stage, charging the resonant inductor and the resonant capacitor with the power supply voltage input through the voltage input terminal, and outputting to the voltage output terminal at the same time.

[0089] As shown in FIG4 , taking the case where the resonant inductor L1 is closer to the first end A of the resonant unit 30 than the resonant capacitor C1 as an example, during the charging phase, a current loop is connected from the input positive electrode VIN+, the first switch S1, the resonant inductor L1, the resonant capacitor C1, the second switch S2, the output positive electrode VOUT+, the output negative electrode VOUT- to the input negative electrode VIN-, so as to charge the resonant inductor L1 and the resonant capacitor C1 connected in series in the resonant unit 30 through the voltage input terminal 10, and output the voltage to the voltage output terminal 20 at the same time.

[0090] As shown in FIG11 , compared to FIG10 , step S20, when the current in the buck circuit is zero, controls the first switch unit to be disconnected, and controls the second switch unit to be turned on, so that the buck circuit enters the buck output stage, and outputs the voltage to the voltage output terminal through the resonant unit, including:

[0091] S200, when the resonant capacitor is fully charged, the current in the buck circuit is zero, the first switch and the third switch are controlled to be disconnected, and the second switch and the fourth switch are controlled to be turned on, so that the buck circuit enters the buck output stage to output the voltage to the voltage output end through the resonant capacitor.

[0092] 3 , the step-down circuit 1 further includes a first voltage-stabilizing capacitor C2 and a second voltage-stabilizing capacitor C3 . The first voltage-stabilizing capacitor C2 is connected to the input positive electrode VIN+ and the input negative electrode VIN-, and the second voltage-stabilizing capacitor C3 is connected to the output positive electrode VOUT+ and the output negative electrode VOUT-.

[0093] As shown in FIG11 , compared with FIG10 , the control method of the step-down circuit 1 further includes:

[0094] S300 , when the step-down circuit does not need to step down the voltage, controlling the first switch, the second switch, the third switch and the fourth switch to be disconnected, so as to output the voltage to the voltage output terminal through the first stabilizing capacitor and the second stabilizing capacitor.

[0095] Therefore, when the step-down circuit 1 does not need to step down the voltage, the voltage output terminal 20 can be output through the first stabilizing capacitor C2 and the second stabilizing capacitor C3. The first stabilizing capacitor C2 and the second stabilizing capacitor C3 can also reduce the ripple current, making the input and output more stable.

[0096] In one or more embodiments, step S300 may be performed after step S200 or before step S100. For example, as shown in FIG11 , when step S300 is performed after step S200, after the step-down output phase, it is detected that the average output voltage value of the step-down circuit 1 is not higher than the preset voltage value, and it is determined that the step-down circuit 1 does not need to step down, and the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 are all controlled to be disconnected, so that the voltage output terminal 20 outputs the voltage through the first stabilizing capacitor C2 and the second stabilizing capacitor C3; whereas, when step S300 is performed before step S100, it is detected that the average output voltage value of the step-down circuit 1 is higher than the preset voltage value, and it is determined that the step-down circuit 1 needs to step down, and the charging phase is entered.

[0097] As shown in FIG5 , taking the case where the resonant inductor L1 is closer to the first end A of the resonant unit 30 than the resonant capacitor C1 as an example, in the step-down output stage, a current loop is connected from one end of the resonant capacitor C1, the resonant inductor L1, the third switch S3, the output positive electrode VOUT+, the output negative electrode VOUT-, the fourth switch S4 to the other end of the resonant capacitor C1. The electric energy charged into the resonant capacitor C1 in the resonant unit 30 during the charging stage is output to the voltage output end 20, thereby reducing the output voltage value.

[0098] Furthermore, as shown in FIG. 6 and FIG. 7 , the step-down circuit 1 may further include a direct output path 60 connected between the voltage input terminal 10 and the voltage output terminal 20 .

[0099] Please refer to FIG12, which is a flow chart of a driving method of a buck circuit in another embodiment of the present application. As shown in FIG12, compared with FIG10, the control method of the buck circuit 1 further includes:

[0100] In step S30 , when the step-down circuit does not need to step down the voltage, the direct output path is turned on to directly output the power supply voltage inputted from the voltage input terminal to the voltage output terminal.

[0101] Therefore, the direct output path 60 can be turned on when the step-down circuit 1 does not need to step down the voltage.

[0102] In one or more embodiments, step S30 may be performed after step S20 or before step S10. For example, as shown in FIG12 , when step S30 is performed after step S20, after the step-down output phase, it is detected that the average output voltage of the step-down circuit 1 is not higher than the preset voltage value, and it is determined that the step-down circuit 1 does not need to step down, and the direct output path 60 is opened. However, when step S30 is performed before step S10, it is detected that the average output voltage of the step-down circuit 1 is higher than the preset voltage value, and it is determined that the step-down circuit 1 needs to step down, and the charging phase is entered.

[0103] In one or more embodiments, before step S10 in the driving method of the buck circuit 1 in any of the above embodiments, the method may further include: disconnecting the direct output path when the buck circuit needs to step down the voltage.

[0104] Therefore, when the buck circuit 1 needs to step down the voltage, the direct output path 60 is disconnected to execute the charging stage and the buck output stage.

[0105] The buck circuit 1 and the control method of the buck circuit 1 of the present application can use fewer switching devices and current branches to controllably convert a higher DC voltage into a lower DC voltage through the above-mentioned structure and steps, thereby reducing the output voltage value and directly outputting the voltage. The circuit structure is simple and the cost is low. At the same time, each switching unit is turned on or off under zero current conditions, realizing a soft switching function, thereby effectively reducing switching losses. In addition, the charging stage and the buck output stage can be started when the output voltage value needs to be reduced, and the buck output stage can be ended when the output voltage value does not need to be further reduced, and the operation is flexible.

[0106] The above description is only a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by any person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application; the embodiments of this application and the features of the embodiments can be combined with each other unless there is a conflict. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A step-down circuit, comprising: A voltage input terminal, used for inputting a power supply voltage; Voltage output terminal; A resonance unit, the resonance unit comprising a resonance inductor and a resonance capacitor connected in series, the resonance unit being connected between the voltage input terminal and the voltage output terminal; A first switch unit and a second switch unit, wherein the buck circuit includes a charging stage and a buck output stage. In the charging stage, the first switch unit is turned on and the second switch unit is turned off. The power supply voltage input from the voltage input end charges the resonance unit and outputs to the voltage output end at the same time. When the current in the buck circuit is zero, the buck output stage is entered. In the buck output stage, the first switch unit is turned off and the second switch unit is turned on. The resonance unit outputs to the voltage output end.

2. The step-down circuit according to claim 1, wherein: The voltage input end includes an input positive electrode and an input negative electrode, the voltage output end includes an output positive electrode and an output negative electrode, the first switch unit includes a first switch and a second switch, and the second switch unit includes a third switch and a fourth switch, wherein the first switch is connected between the input positive electrode and the first end of the resonance unit, the second switch is connected between the second end of the resonance unit and the output positive electrode, the third switch is connected between the first end of the resonance unit and the output positive electrode, one end of the fourth switch is connected to the second end of the resonance unit, and the other end of the fourth switch is connected to the output negative electrode and the input negative electrode.

3. The step-down circuit according to claim 2, wherein: In the charging stage, the first switch and the second switch are both turned on, the third switch and the fourth switch are both turned off, the power supply voltage input to the input positive electrode charges the resonant unit through the turned-on first switch, and the output positive electrode is output through the turned-on second switch, and the output negative electrode is connected to the input negative electrode, thereby forming a current loop in the charging stage; In the step-down output stage, the first switch and the second switch are both disconnected, the third switch and the fourth switch are both turned on, the first end of the resonance unit outputs the output positive electrode through the turned-on third switch, and the second end of the resonance unit is connected to the output negative electrode through the turned-on fourth switch, thereby forming a current loop in the step-down output stage.

4. The step-down circuit according to claim 2, wherein: The buck circuit also includes a first diode, a second diode, a third diode and a fourth diode, wherein the first diode is connected in parallel with the first switch between the input positive electrode and the first end of the resonance unit, the second diode is connected in parallel with the second switch between the second end of the resonance unit and the output positive electrode, the third diode is connected in parallel with the third switch between the first end of the resonance unit and the output positive electrode, and the fourth diode is connected in parallel with the fourth switch between the second end of the resonance unit, the output negative electrode and the input negative electrode, wherein the conduction direction of the first diode is opposite to the current flow direction in the charging stage, the conduction direction of the second diode is the same as the current flow direction in the charging stage, the conduction direction of the third diode is opposite to the current flow direction in the buck output stage, and the conduction direction of the fourth diode is the same as the current flow direction in the buck output stage.

5. The step-down circuit according to claim 2, wherein: The step-down circuit also includes a first voltage-stabilizing capacitor and a second voltage-stabilizing capacitor, the first voltage-stabilizing capacitor is connected to the input positive electrode and the input negative electrode, the second voltage-stabilizing capacitor is connected to the output positive electrode and the output negative electrode, when the step-down circuit does not need to step down the voltage, the first switch, the second switch, the third switch and the fourth switch are all disconnected, the first voltage-stabilizing capacitor and the second voltage-stabilizing capacitor output the voltage to the voltage output end, and when the step-down circuit needs to step down the voltage, the step-down circuit performs a step-down operation through the charging stage and the step-down output stage.

6. The step-down circuit according to any one of claims 1 to 5, wherein: The voltage input end is a DC voltage input end, and the voltage output end is a DC voltage output end.

7. A control method for a step-down circuit, applied to a step-down circuit, wherein: The step-down circuit comprises a voltage input terminal, a voltage output terminal, a resonance unit, a first switch unit and a second switch unit, wherein the voltage input terminal is used to input a power supply voltage; The control method of the step-down circuit comprises: Controlling the first switch unit to be turned on, and controlling the second switch unit to be turned off, so that the buck circuit enters a charging stage, charging the resonance unit through the power supply voltage inputted from the voltage input terminal, and outputting to the voltage output terminal at the same time; When the current in the buck circuit is zero, the first switch unit is controlled to be disconnected, and the second switch unit is controlled to be turned on, so that the buck circuit enters the buck output stage to output the voltage to the voltage output terminal through the resonance unit.

8. The control method of the step-down circuit according to claim 7, wherein: The voltage input end includes an input positive electrode and an input negative electrode, the voltage output end includes an output positive electrode and an output negative electrode, the first switch unit includes a first switch and a second switch, and the second switch unit includes a third switch and a fourth switch, wherein the first switch is connected between the input positive electrode and the first end of the resonance unit, the second switch is connected between the second end of the resonance unit and the output positive electrode, the third switch is connected between the first end of the resonance unit and the output positive electrode, one end of the fourth switch is connected to the second end of the resonance unit, and the other end of the fourth switch is connected to the output negative electrode and the input negative electrode; The controlling the first switch unit to be turned on and the controlling the second switch unit to be turned off so that the buck circuit enters a charging stage, charges the resonance unit through the power supply voltage inputted from the voltage input terminal, and outputs to the voltage output terminal at the same time comprises: The first switch and the second switch are controlled to be turned on, and the third switch and the fourth switch are controlled to be turned off, so that the buck circuit enters the charging stage, and the resonant inductor and the resonant capacitor are charged by the power supply voltage input through the voltage input terminal, and the voltage output terminal is output at the same time.

9. The control method of the step-down circuit according to claim 8, wherein: When the current in the buck circuit is zero, controlling the first switch unit to be disconnected and controlling the second switch unit to be turned on, so that the buck circuit enters the buck output stage, and outputs the voltage to the voltage output end through the resonance unit, comprises: When the resonant capacitor is fully charged, the current in the buck circuit is zero, the first switch and the third switch are controlled to be disconnected, and the second switch and the fourth switch are controlled to be turned on, so that the buck circuit enters the buck output stage to output the voltage to the output end through the resonant capacitor.

10. The control method of the step-down circuit according to claim 9, wherein: The step-down circuit further includes a first voltage-stabilizing capacitor and a second voltage-stabilizing capacitor, wherein the first voltage-stabilizing capacitor is connected to the input positive electrode and the input negative electrode, and the second voltage-stabilizing capacitor is connected to the output positive electrode and the output negative electrode; The control method of the step-down circuit further includes: When the step-down circuit does not need to step down the voltage, the first switch, the second switch, the third switch and the fourth switch are all controlled to be disconnected. The voltage output terminal is outputted through the first voltage stabilizing capacitor and the second voltage stabilizing capacitor.

Images