Control method and DC-DC converter using same

Abstract

The invention discloses a control method and a DC-DC converter using the same. According to the control circuit disclosed by the embodiment of the invention, the switched capacitor converter and the multiphase switching converter are cascaded, and the frequency of the switch in the switched capacitor converter is adjusted according to the voltage difference between the output voltage of the switched capacitor converter and the open-circuit output voltage of the switched capacitor converter, so that the efficiency of the direct current-direct current converter can be improved in a wide load range; and the application range is expanded. Meanwhile, the DC-DC converter based on the embodiment of the invention can reduce the size of a circuit device and generate less heat, thereby improving the integration level.

Description

Technical Field

[0001] The invention relates to power electronic technology, and in particular to a DC-DC converter and a control method thereof. Background Art

[0002] The switched capacitor converter controls the charging and discharging of the capacitor by switches to achieve voltage or current conversion. However, the switched capacitor converter can only achieve fixed input-output voltage conversion. In the prior art, in order to change the input-output voltage ratio conversion and smooth the output voltage, a traditional switching converter is connected in series at the front or back stage of the switched capacitor converter, such as Figure 1 As shown, the input stage is a switched capacitor converter 1, and the output stage is a switched converter 2 using a buck topology. At the same time, in order to reduce ripple and improve load transient response, the switching converter connects multi-phase power stage circuits in parallel to form a multi-phase switching converter to provide a high-precision stable output voltage under a wide range of load conditions. However, the switched capacitor converter and the multi-phase switching converter operate independently at a fixed operating frequency. This control method is difficult to ensure that the switched capacitor converter and the multi-phase switching converter achieve the best system performance in different application scenarios. Summary of the invention

[0003] In view of the above problems, an object of the present invention is to provide a DC-DC converter to achieve optimal system performance.

[0004] According to one aspect of the present invention, there is provided a DC-DC converter, comprising: a switched capacitor converter configured to divide an input voltage in response to a switch control signal to generate a first output voltage;

[0005] A multi-phase switching converter, comprising an N-phase power stage circuit, configured to receive the first output voltage and generate a second output voltage to provide to a load; and

[0006] A control circuit is configured to control the N-phase power stage circuit to adjust the second output voltage according to the output signal of the multi-phase switching converter, and to adjust the frequency of the switching control signal according to the voltage difference between the first output voltage and the open-circuit output voltage of the switching capacitor converter.

[0007] Preferably, the frequency of the switch control signal is positively correlated with the voltage difference between the first output voltage and the open-circuit output voltage.

[0008] Preferably, the frequency of the switch control signal is positively correlated with the pressure difference at least within a partial value range of the pressure difference.

[0009] Preferably, when the voltage difference between the first output voltage and the open-circuit output voltage is less than a lower limit value, the frequency of the switch control signal is a minimum operating frequency; when the voltage difference between the first output voltage and the open-circuit output voltage is greater than an upper limit value, the frequency of the switch control signal is a maximum operating frequency.

[0010] Preferably, the control circuit comprises:

[0011] an amplifier having a first input terminal receiving the open-circuit output voltage, a second input terminal receiving the first output voltage, and an output terminal generating an error signal representing a voltage difference between the first output voltage and the open-circuit output voltage; and

[0012] The clock circuit receives the error signal and generates the switch control signal according to the error signal.

[0013] Preferably, the control circuit comprises:

[0014] The voltage divider circuit is coupled to the input terminal of the switch capacitor converter and is configured to divide the input voltage to generate the open circuit output voltage, wherein the voltage divider ratio of the voltage divider circuit is consistent with the voltage conversion ratio of the switch capacitor converter.

[0015] Preferably, the control circuit comprises:

[0016] The PWM signal generating circuit is used for comparing the output signal of the multi-phase switching converter with a reference signal to generate an error feedback signal, and generating N PWM signals according to the error feedback signal to drive the N-phase power stage circuits respectively.

[0017] Preferably, the control circuit controls the number of power stage circuits entering power operation according to the size of the load current, and controls the switches in the corresponding power stage circuits to be turned on and off according to the number of operating power stage circuits and the output signal of the multi-phase switching converter.

[0018] Preferably, the multi-phase switching converter is a BUCK topology.

[0019] Preferably, the switched capacitor converter comprises at least one switch group and at least one capacitor, each of the switch groups comprises two switches connected in series, and at least part of the capacitor is connected in parallel with the corresponding switch group.

[0020] According to another aspect of the present invention, a control method is provided for controlling a DC-DC converter, the DC-DC converter comprising a switched capacitor converter and a multi-phase switching converter. The control method comprises:

[0021] The switched capacitor converter divides the input voltage in response to the switch control signal to generate a first output voltage;

[0022] The multi-phase switching converter receives the first output voltage and generates a second output voltage to provide to a load;

[0023] Controlling an N-phase power stage circuit in the multi-phase switching converter according to an output signal of the multi-phase switching converter to adjust the second output voltage; and

[0024] The frequency of the switch control signal is adjusted according to a voltage difference between the first output voltage and an open-circuit output voltage of the switched capacitor converter.

[0025] Preferably, the frequency of the switch control signal is positively correlated with the voltage difference between the first output voltage and the open-circuit output voltage.

[0026] Preferably, the frequency of the switch control signal is positively correlated with the pressure difference at least within a partial value range of the pressure difference.

[0027] Preferably, when the voltage difference between the first output voltage and the open-circuit output voltage is less than a lower limit value, the frequency of the switch control signal is a minimum operating frequency; when the voltage difference between the first output voltage and the open-circuit output voltage is greater than an upper limit value, the frequency of the switch control signal is a maximum operating frequency.

[0028] Preferably, the control method includes

[0029] Acquire the voltage difference between the first output voltage and the open-circuit output voltage through an amplifier and generate an error signal; and

[0030] The switch control signal is generated according to the error signal.

[0031] Preferably, the control method includes

[0032] The input voltage is divided to generate the open circuit output voltage, wherein the voltage division ratio is the voltage conversion ratio of the switched capacitor converter.

[0033] The technical solution of the embodiment of the present invention can improve the efficiency of the DC-DC converter in a wide load range by cascading a switched capacitor converter and a multi-phase switched converter, and adjusting the frequency of the switch in the switched capacitor converter according to the voltage difference between the output voltage of the switched capacitor converter and its open-circuit output voltage, thereby expanding the scope of application. At the same time, the DC-DC converter based on the embodiment of the present invention can reduce the size of circuit components and generate less heat, thereby improving integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0035] Figure 1 is a circuit diagram of an exemplary DC-DC converter;

[0036] Figure 2 is a circuit diagram of a DC-DC converter according to an embodiment of the present invention;

[0037] Figure 3 is a circuit diagram of a control circuit according to an embodiment of the present invention;

[0038] Figure 4 is a curve diagram of changes between the operating frequency and the voltage difference of the switched capacitor converter according to an embodiment of the present invention;

[0039] Figure 5 is a curve diagram showing changes in efficiency, operating frequency and output current of a switched capacitor converter according to an embodiment of the present invention;

[0040] Figure 6 is a schematic diagram of the relationship between the number of phases and the output current of the power stage circuit in the multi-phase power converter according to an embodiment of the present invention;

[0041] Figure 7 It is a flow chart of a control method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The present invention is described below based on embodiments, but the present invention is not limited to these embodiments. In the detailed description of the present invention below, some specific details are described in detail. It is possible for a person skilled in the art to fully understand the present invention without the description of these details. In order to avoid confusing the essence of the present invention, known methods, processes, flows, components and circuits are not described in detail.

[0043] In addition, persons of ordinary skill in the art will appreciate that the drawings provided herein are for illustration purposes and are not necessarily drawn to scale.

[0044] At the same time, it should be understood that in the following description, "circuit" refers to a conductive loop composed of at least one element or subcircuit through electrical connection or electromagnetic connection. When an element or circuit is said to be "connected to" another element or an element / circuit is said to be "connected between" two nodes, it can be directly coupled or connected to another element or there can be an intermediate element, and the connection between the elements can be physical, logical, or a combination thereof. On the contrary, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there is no intermediate element between the two.

[0045] Unless the context clearly requires otherwise, throughout the specification and claims, the words "include", "comprising" and similar words should be interpreted in an inclusive sense rather than an exclusive or exhaustive sense; that is, in the sense of "including but not limited to".

[0046] In the description of the present invention, it should be understood that the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0047] Figure 2 is a circuit diagram of a DC-DC converter according to an embodiment of the present invention. Figure 2 As shown, the DC-DC converter of this embodiment includes a switched capacitor converter 10, a multi-phase switching converter 11 and a control circuit 12. The switched capacitor converter 10 receives an input voltage Vin to perform a first-stage power conversion and generates a first output voltage Vmid at the output terminal, and the multi-phase switching converter 11 receives the first output voltage Vmid to perform a second-stage power conversion and generates a second output voltage Vo at the output terminal. The control circuit 12 controls the power stage circuit in the multi-phase switching converter 11 by a closed-loop feedback control method to adjust the second output voltage Vo to meet the load demand. The switched capacitor converter 10 includes at least one switch group and at least one capacitor and divides the input voltage Vin by a fixed voltage division ratio to generate a first output voltage Vmid, wherein each switch group includes two switches connected in series. The control circuit 12 generates switch control signals GH and GL to control the switches in the switched capacitor converter 10 to turn on and off, thereby dividing the input voltage Vin.

[0048] like Figure 2As shown, the multi-phase switching converter 11 includes N-phase power stage circuits P1-PN driven by pulse width modulation (PWM) signals PWM1-PWMN, respectively. Each power stage circuit includes a group of power switches and an inductor, and the power switches are controlled to be turned on and off by corresponding switch control signals to adjust the second output voltage Vo. The power switches and the corresponding inductors are coupled between the input and output ends of the multi-phase power converter, where 1≤i≤N. For example, in the power stage circuit P1, the power switches S11 and S21 are connected in series between the input end and the reference ground of the multi-phase switching converter 11, and the inductor L1 is connected between the common node of the power switches S11 and S21 and the output end of the multi-phase switching converter 11. The output capacitor Co is coupled to the output end of the multi-phase power converter to filter the output current to maintain the second output voltage Vo constant. The second output voltage Vo is used to drive the load Ro. The control circuit controls the N-phase power stage circuits P1-PN according to the output signal of the multi-phase switching converter 11 to adjust the second output voltage Vo. In this embodiment, the multi-phase power converter 11 uses closed-loop control to control the interleaved operation of the power stage circuits of each phase, and adaptively increases or decreases the number of phases of the power stage circuits participating in the power operation according to the output current to achieve current sharing, thereby improving efficiency.

[0049] In order to improve the efficiency of the two-stage DC-DC converter, the control circuit controls the frequencies of the switch control signals GH and GL according to the voltage difference between the first output voltage Vmid and the open-circuit output voltage Vop of the switch capacitor converter 10, that is, controls the operating frequency of the switch in the switch capacitor converter 10. Among them, the open-circuit output voltage refers to the output voltage of the switch capacitor converter 10 under no-load conditions. In one embodiment, the frequency of the switch control signal is positively correlated with the voltage difference at least within a partial numerical range of the voltage difference, and the frequency of the switch control signal increases with the increase of the voltage difference, for example, it can be a linear relationship or a nonlinear relationship, so as to ensure that the switch capacitor converter and the multi-phase switch converter can achieve the best system performance in different application scenarios.

[0050] In this embodiment, the control circuit indirectly obtains the change of the input current or output current of the multi-phase power converter 11 by detecting the voltage difference between the first output voltage Vmid and the open-circuit output voltage Vop, and adaptively adjusts the operating frequency of the switch capacitor converter 10 based on the change of the input current or output current of the multi-phase power converter 11. Compared with the control method of directly sampling the input current or output current of the multi-phase power converter, the embodiment of the present application uses a non-destructive detection method to adjust the frequency of the switch capacitor converter to improve efficiency, and can ensure that the switch capacitor converter and the multi-phase switch converter can achieve optimal system performance in different application scenarios, so that the DC-DC converter can achieve high efficiency in the entire load range.

[0051] In the present embodiment, the switch capacitor converter 10 includes two switch groups, which are respectively a switch group consisting of switches Q1 and Q2 connected in series and a switch group consisting of switches Q3 and Q4 connected in series. In each switch group, two switches are connected in series. In the present embodiment, switches Q1-Q4 use metal oxide semiconductor transistors (MOSFET). However, other types of electronically controlled switch devices, such as bipolar junction transistors (BJT) and insulated gate transistors (IGBT) can also be used as switches of the present embodiment. The switch capacitor converter 10 also includes capacitors C1 and C2. Capacitor C2 is connected in parallel with the switch group consisting of switches Q3 and Q4. One end of capacitor C1 is connected to the common node of switches Q1 and Q2, and one end is connected to the common node of switches Q3 and Q4. For the switch capacitor converter 10, switches Q1 and Q4 are controlled by switch control signals GH, and switches Q2 and Q3 are controlled by switch control signals GL. In this embodiment, the switch control signal GH and the switch control signal GL are complementary signals for explanation, that is, when the signal GH is at a high level, the signal GL is at a low level, and vice versa. The switch control signals GH and GL are continuously switched by controlling the state of the switch group, so that the capacitors C1 and C2 can be repeatedly charged and discharged, thereby maintaining a substantially constant output. In this embodiment, the voltage on each capacitor is 1 / 2 of the input port voltage Vin. Thus, the voltage conversion ratio of the switch capacitor converter 10 is 1 / 2.

[0052] According to the above analysis, the ratio of the output voltage to the input voltage of the switched capacitor converter 10 is a fixed value and has nothing to do with the duty cycle of the switch control signal GH or GL. At the same time, the output voltage Vo of the multi-phase switching converter 11 is determined by the voltage Vmid at the input end and the duty cycle of the PWM signals PWM1-PWMN of the switches in the power stage circuit.

[0053] In this embodiment, the voltage gain of the switched capacitor converter 10 is 1 / 2, and the power stage circuit of the multi-phase switching converter 11 is a buck topology with a gain less than 1. The control circuit can adjust the duty cycle of the PWM signals PWM1-PWMN based on various methods to adjust the state of the multi-phase switching converter 11. The control method can include a pulse width modulation method (PWM control), a pulse frequency modulation method (PFM control), and a combination of the above methods. In one control method, the control circuit generates an error feedback signal by comparing the output signal of the multi-phase switching converter with a reference signal, and generates N PWM signals according to the error feedback signal to drive the N-phase power stage circuits respectively.

[0054] Figure 3is a circuit diagram of a control circuit of an embodiment of the present invention. The control circuit adjusts the switching frequency of the switched capacitor converter according to the voltage difference between the first output voltage Vmid and the open-circuit output voltage, and the voltage difference between the first output voltage Vmid and the open-circuit output voltage is positively correlated with the switching frequency.

[0055] In this embodiment, the control circuit obtains the open-circuit output voltage by sampling the input voltage of the switched capacitor converter. Specifically, the control circuit includes a voltage divider circuit (not shown), whose voltage divider ratio is the same as the voltage conversion ratio of the switched capacitor converter, and the voltage divider circuit is coupled to the input end of the switched capacitor converter to receive the input voltage Vin and generate an open-circuit output voltage. For example Figure 2 The voltage conversion ratio of the switched capacitor converter is 1 / 2, so the voltage division ratio of the voltage divider circuit is also 1 / 2, and the open circuit output voltage is 1 / 2Vin.

[0056] The control circuit includes an amplifier 30, which controls the frequency of a switch control signal by detecting the voltage difference between the first output voltage Vmid and the open-circuit output voltage, wherein the switch control signal is used to drive the switch in the switched capacitor converter. The first input terminal (e.g., the inverting input terminal) of the amplifier 30 receives the first output voltage Vmid, and the second input terminal (e.g., the non-inverting input terminal) receives the open-circuit output voltage Vop, and the output terminal thereof generates an error signal. The control circuit adjusts the frequency of the switch control signal according to the error signal, thereby changing the operating frequency of the switch in the switched capacitor converter to improve efficiency.

[0057] The control circuit further includes a clock circuit 31, which generates a switch control signal GH or GL according to a voltage difference between the first output voltage Vmid and the open-circuit output voltage. For example, the clock circuit can be configured as a phase-locked loop.

[0058] In one embodiment, the control circuit further includes a PWM signal generating circuit (not shown in the figure). The PWM signal generating circuit controls the N-phase power stage circuit to adjust the second output voltage according to the output signal of the multi-phase switching converter. Specifically, the PWM signal generating circuit generates an error feedback signal by comparing the output signal of the multi-phase switching converter with a reference signal, and generates N PWM signals according to the error feedback signal to drive the N-phase power stage circuits respectively.

[0059] Figure 4It is a curve diagram of the change between the operating frequency and the voltage differential of the switching capacitor converter of the embodiment of the present invention. When the voltage differential Vdiff between the first output voltage Vmid and the open-circuit output voltage is less than the lower limit value Vd1, the frequency of the switch control signal is the minimum operating frequency Fmin. When the voltage differential Vdiff between the first output voltage Vmid and the open-circuit output voltage is greater than the upper limit value Vd2, the frequency of the switch control signal is the maximum operating frequency Fmax. When the voltage differential Vdiff between the first output voltage Vmid and the open-circuit output voltage is between the lower limit value Vd1 and the upper limit value Vd2, the frequency F of the switch control signal is positively correlated with the voltage differential Vdiff, and the frequency of the switch control signal increases with the increase of the voltage differential Vdiff. Figure 4 As described, when the voltage difference Vdiff is between the lower limit Vd1 and the upper limit Vd2, the frequency F of the switch control signal is linearly related to the voltage difference between the first output voltage Vmid and the open-circuit output voltage. It should be understood that the frequency of the switch control signal in this embodiment may also be nonlinearly related to the voltage difference, and the present invention is not limited to this. Among them, the minimum operating frequency Fmin can ensure that the switched capacitor converter works normally and keeps the first output voltage Vmid constant, and the maximum operating frequency Fmax can be set according to the on-resistance of the capacitor and the switch in the switched capacitor converter, and is not limited here.

[0060] Figure 5 1 is a curve diagram showing the change between the efficiency, the operating frequency and the output current of the switched capacitor converter according to the embodiment of the present invention. The solid line is the curve showing the change between the efficiency and the output current of the switched capacitor converter according to the embodiment of the present invention, and the dotted line is the curve showing the change between the operating frequency and the output current of the switched capacitor converter according to the embodiment of the present invention.

[0061] like Figure 5 As shown, the operating frequency of the switched capacitor converter changes adaptively with the output current Iload, thereby improving efficiency. The efficiency curve of the switched capacitor converter of the embodiment of the present invention remains basically constant over the entire load range. When the output current Iload is lower than 1A, the efficiency of the switched capacitor converter of the embodiment of the present invention remains above 94%. In the traditional control method, the efficiency of the switched capacitor converter in the two-stage DC-DC converter drops to nearly 20% under the same load conditions, which limits the scope of application. The efficiency of the switched capacitor converter of the embodiment of the present application is high over the entire load range and can be applied to a variety of applications. ,

[0062] In order to further improve the efficiency of the DC-DC converter, the multi-phase power converter can use current balancing technology to improve its own efficiency, thereby improving the overall efficiency of the DC-DC converter. In this embodiment, the multi-phase power converter uses closed-loop control to control the interleaving of the power stage circuits of each phase, and adaptively increases or decreases the number of phases of the power stage circuits involved in the work according to the output current, such as Figure 6 It should be understood that the multi-phase power converter in the embodiment of the present application can also sample other current sharing technologies to improve efficiency, such as slope compensation, average current sampling, etc.

[0063] Figure 6 Schematic diagram of the relationship between the number of phases and output current of the power stage circuit in the multi-phase power converter of the embodiment of the present invention. In this embodiment, the power stage circuit in the multi-phase power converter is described by taking 4 phases as an example. In the embodiment of the present invention, the control circuit controls the number of power stage circuits entering the power operation according to the magnitude of the output current, and controls the switches in the corresponding power stage circuits to turn on and off according to the number of operating power stage circuits and the output signal. Figure 6 As shown, as the output current Iload increases, the number of phases of the power stage circuits involved in the power operation in the multi-phase power converter also increases, for example, the number of phases of the power stage circuits involved in the power operation increases from 1 phase to 4 phases; as the output current Iload decreases, the number of phases of the power stage circuits involved in the power operation in the multi-phase power converter also decreases, for example, the number of phases of the power stage circuits involved in the power operation decreases from 4 phases to 1 phase. It should be understood that Figure 6 The relationship diagram shown is to facilitate understanding of the relationship between the output current and the number of phases of the power stage circuit involved in power operation. In actual work, since the magnitude of the output current is relative, the number of phases of the power stage circuit involved in power operation is not completely consistent with Figure 6 In the schematic diagram, as long as the output current of each phase remains consistent, the multi-phase power converter in the embodiment of the present invention further improves the efficiency through the current sharing technology, thereby improving the efficiency of the entire DC-DC converter.

[0064] Figure 7 FIG. 1 is a flow chart of a control method according to an embodiment of the present invention. Figure 7 As shown, the control method is used to control a DC-DC converter, which includes a cascaded switched capacitor converter and a multi-phase switching converter. The control method includes the following steps:

[0065] Step S100 : The switched capacitor converter divides an input voltage in response to a switch control signal to generate a first output voltage.

[0066] Step S200: The multi-phase switching converter receives a first output voltage and generates a second output voltage to provide to a load.

[0067] Step S300: controlling the N-phase power stage circuit in the multi-phase switching converter according to the output signal of the multi-phase switching converter to adjust the second output voltage.

[0068] Step S400: adjusting the frequency of the switch control signal according to the voltage difference between the first output voltage and the open-circuit output voltage of the switched capacitor converter.

[0069] Preferably, the frequency of the switch control signal is in direct proportion to the voltage difference between the first output voltage and the open-circuit output voltage.

[0070] Preferably, the frequency of the switch control signal is directly proportional to the pressure difference at least within a partial value range of the pressure difference.

[0071] Preferably, when the voltage difference between the first output voltage and the open-circuit output voltage is less than a lower limit value, the frequency of the switch control signal is the minimum operating frequency; when the voltage difference between the first output voltage and the open-circuit output voltage is greater than an upper limit value, the frequency of the switch control signal is the maximum operating frequency.

[0072] Preferably, the voltage difference between the first output voltage and the open-circuit output voltage is obtained by an amplifier and an error signal is generated; and the switch control signal is generated according to the error signal.

[0073] Preferably, the open-circuit output voltage is generated by dividing the input voltage, wherein the voltage division ratio is the voltage conversion ratio of the switched capacitor converter.

[0074] In the embodiment of the present invention, the DC-DC converter obtains the change of the input current or output current of the multi-phase power converter by detecting the voltage difference between the first output voltage and the open-circuit output voltage, and adaptively adjusts the operating frequency based on the change of the input current or output current of the multi-phase power converter. This control method can ensure that the switched capacitor converter and the multi-phase switching converter achieve the best system performance in different application scenarios, so that the DC-DC converter achieves high efficiency in the entire load range.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A DC-DC converter, comprising: a switched capacitor converter configured to divide an input voltage in response to a switch control signal to generate a first output voltage; A multi-phase switching converter, comprising an N-phase power stage circuit, configured to receive the first output voltage and generate a second output voltage to provide to a load; as well as A control circuit is configured to control the N-phase power stage circuit to adjust the second output voltage according to the output signal of the multi-phase switching converter, and to adjust the frequency of the switching control signal according to the voltage difference between the first output voltage and the open-circuit output voltage of the switching capacitor converter.

2. The DC-DC converter according to claim 1, characterized in that: The frequency of the switch control signal is positively correlated with the voltage difference between the first output voltage and the open-circuit output voltage.

3. The DC-DC converter according to claim 1, characterized in that: The frequency of the switch control signal is positively correlated with the pressure difference at least within a partial value range of the pressure difference.

4. The DC-DC converter according to claim 3, characterized in that: When the voltage difference between the first output voltage and the open-circuit output voltage is less than a lower limit value, the frequency of the switch control signal is a minimum operating frequency; when the voltage difference between the first output voltage and the open-circuit output voltage is greater than an upper limit value, the frequency of the switch control signal is a maximum operating frequency.

5. The DC-DC converter according to claim 1, characterized in that: The control circuit comprises: an amplifier having a first input terminal receiving the open-circuit output voltage, a second input terminal receiving the first output voltage, and an output terminal generating an error signal representing a voltage difference between the first output voltage and the open-circuit output voltage; and The clock circuit receives the error signal and generates the switch control signal according to the error signal.

6. The DC-DC converter according to claim 5, characterized in that: The control circuit comprises: The voltage divider circuit is coupled to the input terminal of the switch capacitor converter and is configured to divide the input voltage to generate the open circuit output voltage, wherein the voltage divider ratio of the voltage divider circuit is consistent with the voltage conversion ratio of the switch capacitor converter.

7. The DC-DC converter according to claim 5, characterized in that: The control circuit comprises: The PWM signal generating circuit is used for comparing the output signal of the multi-phase switching converter with a reference signal to generate an error feedback signal, and generating N PWM signals according to the error feedback signal to drive the N-phase power stage circuits respectively.

8. The DC-DC converter according to claim 1, characterized in that: The control circuit controls the number of power stage circuits entering power operation according to the magnitude of the output current, and controls the switches in the corresponding power stage circuits to turn on and off according to the number of operating power stage circuits and the output signal of the multi-phase switching converter.

9. The DC-DC converter according to claim 1, characterized in that: The multi-phase switching converter is a BUCK topology.

10. The DC-DC converter according to claim 1, characterized in that: The switched capacitor converter includes at least one switch group and at least one capacitor, each of the switch groups includes two switches connected in series, and at least part of the capacitors are connected in parallel with the corresponding switch groups.

11. A control method for controlling a DC-DC converter, wherein the DC-DC converter comprises a switched capacitor converter and a multi-phase switching converter, the control method comprising: The switched capacitor converter divides the input voltage in response to the switch control signal to generate a first output voltage; The multi-phase switching converter receives the first output voltage and generates a second output voltage to provide to a load; Controlling an N-phase power stage circuit in the multi-phase switching converter according to an output signal of the multi-phase switching converter to adjust the second output voltage; as well as The frequency of the switch control signal is adjusted according to a voltage difference between the first output voltage and an open-circuit output voltage of the switched capacitor converter.

12. The control method according to claim 11, characterized in that: The frequency of the switch control signal is positively correlated with the voltage difference between the first output voltage and the open-circuit output voltage.

13. The control method according to claim 11, characterized in that: The frequency of the switch control signal is positively correlated with the pressure difference at least within a partial value range of the pressure difference.

14. The control method according to claim 13, characterized in that: When the voltage difference between the first output voltage and the open-circuit output voltage is less than a lower limit value, the frequency of the switch control signal is a minimum operating frequency; when the voltage difference between the first output voltage and the open-circuit output voltage is greater than an upper limit value, the frequency of the switch control signal is a maximum operating frequency.

15. The control method according to claim 11, characterized in that: include Acquire the voltage difference between the first output voltage and the open-circuit output voltage through an amplifier and generate an error signal; as well as The switch control signal is generated according to the error signal.

16. The control method according to claim 11, characterized in that: include The input voltage is divided to generate the open circuit output voltage, wherein the voltage division ratio is the voltage conversion ratio of the switched capacitor converter.

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