Cascaded dc-dc converter, design method thereof and load point power supply

Abstract

The application provides a cascaded DC-DC converter and a design method and a load point power supply thereof, wherein the design method comprises the following steps: obtaining an indirect resonant switched capacitor converter with a preset voltage conversion ratio based on a Dickson switched capacitor converter, and obtaining a target resonant converter; and connecting the target resonant converter with a BUCK converter in cascade to obtain the cascaded DC-DC converter. The application solves the problems that the traditional indirect resonant switched capacitor converter is not conducive to realizing a large voltage conversion ratio because the voltage conversion ratio is strictly related to the number of power devices, and the output voltage regulation capacity is poor.

Description

Technical Field

[0001] This invention relates to the field of DC-DC converters, and in particular to a cascaded DC-DC converter and its design method, as well as a point-of-load power supply. Background Technology

[0002] Due to the huge demand for storage and processing of high-definition images and videos from cloud computing and big data, high-frequency and high-efficiency power supplies for data center applications are emerging. With the continuous development of integrated circuit chip technology, higher requirements are being placed on the performance of buck DC-DC converters used in applications with high voltage conversion ratios and high current.

[0003] Currently, the most commonly used non-isolated power converters basically adopt a BUCK topology, such as... Figure 1 As shown, its advantage lies in its good output voltage regulation capability, but when the voltage conversion ratio is large and the output current is large, its disadvantages of low efficiency and low power density become more obvious.

[0004] The presence of a power inductor is a key factor limiting converter efficiency and power density; therefore, inductorless switched-capacitor converters have become a popular choice for designing high-efficiency, high-power-density converters. However, due to differences in flying capacitor values, significant transient currents and capacitor charging losses are generated during circuit mode switching, and the capacitors are also relatively large.

[0005] To address these issues, a hybrid resonant switched-capacitor converter can be constructed using one or more small inductors to achieve soft switching of power devices and soft charging of flying capacitors, thereby significantly improving converter efficiency. Since the small inductors are not used as filters, they have minimal impact on the efficiency and power density of traditional switched-capacitor converters.

[0006] Due to the different positions of the resonant inductor, hybrid resonant switched-capacitor converters can be divided into direct resonant switched-capacitor converters and indirect resonant switched-capacitor converters. Indirect resonant switched-capacitor converters simply require connecting the resonant capacitor and resonant inductor in series to form a series resonant cavity, resulting in a simpler control method and making them more suitable for practical engineering applications. However, the voltage conversion ratio of indirect resonant switched-capacitor converters is strictly related to the number of power devices. When the voltage conversion ratio is large, the number of power devices will be very large, and the output voltage regulation capability will be very poor.

[0007] It should be noted that the above description of the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of the present invention and facilitating understanding by those skilled in the art. It should not be assumed that the above technical solutions are known to those skilled in the art simply because they have been described in the background section of this invention. Summary of the Invention

[0008] In view of the above-mentioned disadvantages of the prior art, the purpose of the present application is to provide a cascaded DC-DC converter, a design method thereof and a load point power supply, which are used to solve the problem that the voltage conversion ratio of a conventional indirect resonant switched capacitor converter is strictly related to the number of power devices, which is not conducive to realizing a large voltage conversion ratio, and the problem that the output voltage regulation capability is poor.

[0009] To achieve the above-mentioned purpose and other related purposes, the present application provides a design method of a cascaded DC-DC converter, which comprises the following steps:

[0010] obtaining an indirect resonant switched capacitor converter with a preset voltage conversion ratio based on a Dickson switched capacitor converter, and obtaining a target resonant converter therefrom;

[0011] cascading the target resonant converter with a BUCK converter to obtain a cascaded DC-DC converter.

[0012] Optionally, the method for obtaining the target resonant converter comprises:

[0013] obtaining an indirect resonant switched capacitor converter with a preset voltage conversion ratio based on a Dickson switched capacitor converter, and taking the indirect resonant switched capacitor converter as the target resonant converter.

[0014] Optionally, the method for obtaining the target resonant converter comprises:

[0015] obtaining an indirect resonant switched capacitor converter with a preset voltage conversion ratio based on a Dickson switched capacitor converter, and performing inductance simplification on the indirect resonant switched capacitor converter to obtain the target resonant converter.

[0016] Optionally, the method for obtaining the target resonant converter by performing inductance simplification on the indirect resonant switched capacitor converter comprises:

[0017] determining the circuit topology of the indirect resonant switched capacitor converter in different switching states, and establishing state space equations in different switching states;

[0018] performing weighted calculation on the state space equations in different switching states based on the duty cycles of different switching states to obtain state space average equations;

[0019] obtaining inductance simplification information based on the state space average equations, and performing inductance simplification on the indirect resonant switched capacitor converter to obtain the target resonant converter.

[0020] Optionally, the method for obtaining the inductance simplification information comprises:

[0021] sequentially making each resonant inductance in the indirect resonant switched-capacitor converter equal to zero, and observing whether the composition of the state-space average equation changes;

[0022] obtaining information that all resonant inductances equal to zero when the composition of the state-space average equation does not change, and obtaining inductance simplification information based on the information.

[0023] Optionally, the method for obtaining the target resonant converter comprises:

[0024] based on a Dickson switched-capacitor converter, obtaining an indirect resonant switched-capacitor converter with a preset voltage conversion ratio;

[0025] obtaining inductance simplification information corresponding to the preset voltage conversion ratio from an inductance simplification rule, and simplifying inductance of the indirect resonant switched-capacitor converter to obtain the target resonant converter.

[0026] Optionally, the method for obtaining the inductance simplification rule comprises:

[0027] based on a Dickson switched-capacitor converter, obtaining a plurality of first indirect resonant switched-capacitor converters with even voltage conversion ratios and a plurality of second indirect resonant switched-capacitor converters with odd voltage conversion ratios;

[0028] obtaining a first state-space average equation corresponding to each of the first indirect resonant switched-capacitor converters, and obtaining a first inductance simplification rule corresponding to even voltage conversion ratios based on the first state-space average equation;

[0029] obtaining a second state-space average equation corresponding to each of the second indirect resonant switched-capacitor converters, and obtaining a second inductance simplification rule corresponding to odd voltage conversion ratios based on the second state-space average equation;

[0030] composing the inductance simplification rule based on the first inductance simplification rule and the second inductance simplification rule.

[0031] Optionally, the method for obtaining the corresponding state-space average equation comprises:

[0032] determining a circuit topology of a corresponding indirect resonant switched-capacitor converter under different switching states, and establishing state-space equations under the different switching states;

[0033] based on a duty cycle of each of the different switching states, performing weighted calculation on the state-space equations under the different switching states to obtain the corresponding state-space average equation.

[0034] Optionally, the method for obtaining the first inductor simplification rule comprises: obtaining first inductor simplification information corresponding to each first indirect resonant switched-capacitor converter based on each first state-space averaging equation, and extracting rules from the first inductor simplification information to obtain the first inductor simplification rule.

[0035] The method for obtaining the second inductor simplification rule comprises: obtaining second inductor simplification information corresponding to each second indirect resonant switched-capacitor converter based on each second state-space averaging equation, and extracting rules from the second inductor simplification information to obtain the second inductor simplification rule.

[0036] Optionally, the method for obtaining the corresponding inductor simplification information comprises:

[0037] In sequence, each resonant inductor in the corresponding indirect resonant switched-capacitor converter is set to zero, and whether the composition of the corresponding state-space averaging equation is changed is observed.

[0038] When the composition of the corresponding state-space averaging equation is not changed, information that all resonant inductors are set to zero is obtained, and the corresponding inductor simplification information is obtained based on the information.

[0039] Optionally, the preset voltage conversion ratio is denoted as M:1, where M is a natural number greater than 2; when M is an even number greater than 2, the first inductor simplification rule comprises that the kth resonant inductor is set to zero, where k is an even number greater than 1 and less than (M-1); when M is an odd number greater than 2, the second inductor simplification rule comprises that the kth resonant inductor is set to zero, where k is an even number greater than 1 and less than (M-1).

[0040] Optionally, the target resonant converter and the BUCK converter are cascaded by parallel intermediate capacitors, where the target resonant converter is a front-stage converter, and the BUCK converter is a rear-stage converter, or the BUCK converter is a front-stage converter, and the target resonant converter is a rear-stage converter.

[0041] The application further provides a cascaded DC-DC converter, which is designed by the design method according to any one of the above.

[0042] The application further provides a load point power supply, which comprises the cascaded DC-DC converter according to the above.

[0043] As described above, the cascaded DC-DC converter and its design method, along with the point-of-load power supply of this invention, propose a novel converter architecture through the cascaded design of a target resonant converter and a BUCK converter. This architecture combines the advantages of both converters, possessing both strong voltage regulation capability and high efficiency, thus meeting the needs of applications requiring high voltage conversion ratios and large output currents. For applications with large voltage conversion ratios and large output currents, this invention can achieve this with fewer switching transistors, significantly reducing the voltage stress on the transistors and effectively reducing their size, which is beneficial for chip miniaturization. Furthermore, it also has a significant advantage in improving the full-load efficiency of high-current output converters. Moreover, the target resonant converter and the BUCK converter are controlled separately, making control relatively simple and the control circuit design easier, thus making it more suitable for practical engineering applications. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of a traditional BUCK converter.

[0045] Figure 2 This is a flowchart of the design method in an embodiment of the present invention.

[0046] Figure 3 This is a schematic diagram of the Dixon switched capacitor converter in an embodiment of the present invention.

[0047] Figure 4 This is a schematic diagram of the structure of an indirect resonant switched capacitor converter with a voltage conversion ratio of 4:1 in an embodiment of the present invention.

[0048] Figure 5 for Figure 4 The circuit topology of the converter shown is part of the circuit in the first switching state.

[0049] Figure 6 for Figure 4 The circuit topology of the converter shown is another part of the circuit in the first switching state.

[0050] Figure 7 for Figure 4 The circuit topology of the converter shown is part of the circuit in the second switching state.

[0051] Figure 8 for Figure 4 The circuit topology of the converter in the second switching state is shown in another part.

[0052] Figure 9 for Figure 4 The diagram shows the simplified inductor structure of the converter.

[0053] Figure 10A structure diagram of an indirect resonant switched capacitor converter with a voltage conversion ratio of 5:1 in an embodiment of the present application.

[0054] Figure 11 A part of the circuit topology of the converter shown in FIG. 1 in a first switch state. Figure 10

[0055] Figure 12 Another part of the circuit topology of the converter shown in FIG. 1 in the first switch state. Figure 10

[0056] Still another part of the circuit topology of the converter shown in FIG. 1 in the first switch state. Figure 13 Figure 10 A part of the circuit topology of the converter shown in FIG. 1 in a second switch state.

[0057] Figure 14 Figure 10 Another part of the circuit topology of the converter shown in FIG. 1 in the second switch state.

[0058] Figure 15 Still another part of the circuit topology of the converter shown in FIG. 1 in the second switch state. Figure 10

[0059] A structure diagram of the converter shown in FIG. 1 after simplifying the inductors. Figure 16 Figure 10 A structure diagram of a cascaded DC-DC converter in an embodiment of the present application.

[0060] Figure 17 Another structure diagram of the cascaded DC-DC converter in an embodiment of the present application.

[0061] Figure 18 A specific example of the cascaded DC-DC converter in an embodiment of the present application.

[0062] Figure 19 A simulation waveform diagram of the relevant signals in the converter shown in FIG. 1.

[0063] Figure 20 Figure 19 A prototype of the cascaded DC-DC converter in an embodiment of the present application.

[0064] Figure 21 A waveform diagram of the input voltage and the output voltage in the converter shown in FIG. 1.

[0065] Figure 22 A voltage waveform diagram of the first switch, the second switch and the fourth switch in the converter shown in FIG. 1. Figure 21

[0066] Figure 23 Figure 21 ​​​​​​​​

[0067] Figure 24 for Figure 21 The current waveforms of the first and second resonant inductors in the converter shown are illustrated.

[0068] Figure 25 for Figure 21 The diagram shows the dynamic response of the converter. Detailed Implementation

[0069] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0070] Please see Figures 2 to 25 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the shape, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0071] like Figure 2 As shown, this embodiment provides a design method for a cascaded DC-DC converter, including the following steps, such as step S1 and step S2.

[0072] Step S1: Based on the Dickson switched capacitor converter, obtain an indirect resonant switched capacitor converter with a preset voltage conversion ratio, and thereby obtain the target resonant converter.

[0073] In one example, the method for obtaining the target resonant converter includes: obtaining an indirect resonant switched capacitor converter with a preset voltage conversion ratio based on a Dickson switched capacitor converter, and using it as the target resonant converter.

[0074] The Dixon switched capacitor converter has a voltage conversion ratio of 4:1. By adjusting the circuit topology of the Dixon switched capacitor converter, indirect resonant switched capacitor converters with different voltage conversion ratios (e.g., even voltage conversion ratios greater than 2 or odd voltage conversion ratios greater than 2) can be obtained.

[0075] like Figure 3 As shown, the Dickson switched capacitor converter includes an input power supply v in, a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a fifth switch S5, a sixth switch S6, a seventh switch S7, an eighth switch S8, a first resonant capacitor C1, a second resonant capacitor C2, a third resonant capacitor C3 and an output capacitor C out . Wherein: the first switch S1 to the fourth switch S4 are connected in series between the positive terminal of the input power supply v in and the first terminal of the output capacitor C out and sequentially form the first node J1 to the third node J3, the negative terminal of the input power supply v in and the second terminal of the output capacitor C out are connected to the reference ground, the fifth switch S5 and the sixth switch S6 are connected in series between the first terminal of the output capacitor C out and the reference ground and form the fourth node J4, the seventh switch S7 and the eighth switch S8 are connected in series between the first terminal of the output capacitor C out and the reference ground and form the fifth node J5, the first resonant capacitor C1 is connected between the first node J1 and the fourth node J4, the second resonant capacitor C2 is connected between the second node J2 and the fifth node J5, and the third resonant capacitor C3 is connected between the third node J3 and the fourth node J4; wherein the first switch S1, the third switch S3, the fifth switch S5 and the seventh switch S7 are controlled by the first control signal, the second switch S2, the fourth switch S4, the sixth switch S6 and the eighth switch S8 are controlled by the second control signal, and the first control signal and the second control signal are a group of complementary control signals with a duty cycle close to 50%.

[0076] Regarding the above Dickson switched capacitor converter, taking the output capacitor C out as the reference, the switch located on the left side thereof is recorded as the front-end switch, and the switch located on the right side thereof is recorded as the rear-end switch; when the circuit topology of the Dickson switched capacitor converter is adjusted, mainly the number of switches in series of the front-end switch, the number of parallel branches of the rear-end switch, the number of resonant capacitors, the number of resonant inductors, etc. are adjusted; taking the preset voltage conversion ratio M:1 as an example, M is a natural number greater than 2, then in the indirect resonant switched capacitor converter obtained after adjustment, the number of front-end switches is M, the number of parallel branches of rear-end switches is (M-1), the number of resonant capacitors is (M-1), and the number of resonant inductors is (M-1); of course, it also needs to be matched with the corresponding electrical connection, usually M front-end switches are connected in series to form (M-1) front-end nodes, and each parallel branch forms a rear-end node, wherein (M-1) front-end nodes and (M-1) rear-end nodes correspond one by one and form (M-1) node groups, and (M-1) resonant capacitors and (M-1) resonant inductors correspond one by one and are connected in series between (M-1) node groups.

[0077] Taking an indirect resonant switched-capacitor converter with a preset voltage conversion ratio of 4:1 as an example, based on the original components of the Dickson switched-capacitor converter, a ninth switch S9 and a tenth switch S are added. 10 The first resonant inductor L1, the second resonant inductor L2, and the third resonant inductor L3, as follows: Figure 4 As shown. Wherein: the first switch S1 to the fourth switch S4 are connected in series with the input power supply v. in The positive terminal and the output capacitor C out The first end is connected to form the first node J1 to the third node J3 in sequence, and the input power supply v in The negative terminal and output capacitor C out The second terminal is connected to the reference ground, and the fifth switch S5 and the sixth switch S6 are connected in series with the output capacitor C. out The first terminal and the reference ground form the fourth node J4, and the seventh switch S7 and the eighth switch S8 are connected in series with the output capacitor C. out The first terminal and the reference ground form the fifth node J5, the ninth switch S9 and the tenth switch S 10 Series connected to output capacitor C out The first terminal and the reference ground form a sixth node J6. The first resonant capacitor C1 and the first resonant inductor L1 are connected in series between the first node J1 and the sixth node J6. The second resonant capacitor C2 and the second resonant inductor L2 are connected in series between the second node J2 and the fifth node J5. The third resonant capacitor C3 and the third resonant inductor L3 are connected in series between the third node J3 and the fourth node J4. The first switch S1, the third switch S3, the fifth switch S5, the seventh switch S7 and the ninth switch S9 are controlled by the first control signal. The second switch S2, the fourth switch S4, the sixth switch S6, the eighth switch S8 and the tenth switch S9 are controlled by the first control signal. 10 Controlled by the second control signal, and the first control signal and the second control signal are a set of complementary control signals with a duty cycle close to 50%; of course, it is also feasible to connect the first resonant capacitor C1 and the first resonant inductor L1 in series between the first node J1 and the fourth node J4, and to connect the third resonant capacitor C3 and the third resonant inductor L3 in series between the third node J3 and the sixth node J6.

[0078] Taking an indirect resonant switched-capacitor converter with a preset voltage conversion ratio of 5:1 as an example, based on the original components of the Dickson switched-capacitor converter, a ninth switch S9 and a tenth switch S are added. 10 Eleventh switch S 11 12th switch S 12 13th switch S 13, fourth resonance capacitor C4, first resonance inductor L1, second resonance inductor L2, third resonance inductor L3 and fourth resonance inductor L4, as shown in Figure 10 Fig. 1. Wherein: the first switch S1 to the fifth switch S5 are connected in series between the positive terminal of the input power supply v in and the first terminal of the output capacitor C out and form the first node J1 to the fourth node J4 in turn, the negative terminal of the input power supply v in and the second terminal of the output capacitor C out are connected to the reference ground, the sixth switch S6 and the seventh switch S7 are connected in series between the first terminal of the output capacitor C out and the reference ground and form the fifth node J5, the eighth switch S8 and the ninth switch S9 are connected in series between the first terminal of the output capacitor C out and the reference ground and form the sixth node J6, the tenth switch S 10 and the eleventh switch S 11 are connected in series between the first terminal of the output capacitor C out and the reference ground and form the seventh node J7, the twelfth switch S 12 and the thirteenth switch S 13 are connected in series between the first terminal of the output capacitor C out and the reference ground and form the eighth node J8, the first resonance capacitor C1 and the first resonance inductor L1 are connected in series between the first node J1 and the fifth node J5, the second resonance capacitor C2 and the second resonance inductor L2 are connected in series between the second node J2 and the sixth node J6, the third resonance capacitor C3 and the third resonance inductor L3 are connected in series between the third node J3 and the seventh node J7, and the fourth resonance capacitor C4 and the fourth resonance inductor L4 are connected in series between the fourth node J4 and the eighth node J8; wherein the first switch S1, the third switch S3, the fifth switch S5, the sixth switch S6, the eighth switch S8, the tenth switch S 10 and the twelfth switch S 12 are controlled by the first control signal, the second switch S2, the fourth switch S4, the seventh switch S7, the ninth switch S9, the eleventh switch S 11 and the thirteenth switch S 13 are controlled by the second control signal, and the first control signal and the second control signal are a group of complementary control signals with a duty cycle close to 50%.

[0079] Of course, the circuit topology of the Dickson switched capacitor converter is adjusted according to the above adjustment mode, and other indirect resonant switched capacitor converters with preset voltage conversion ratios can also be obtained, which will not be enumerated one by one in this example; it should be clear to those skilled in the art that the circuit topology of the Dickson switched capacitor converter can be adjusted according to the above adjustment mode to obtain an indirect resonant switched capacitor converter with any preset voltage conversion ratio greater than 2.

[0080] In another example, the method for obtaining a target resonant converter includes: obtaining an indirect resonant switched-capacitor converter with a preset voltage conversion ratio based on a Dickson switched-capacitor converter; and simplifying inductance of the obtained indirect resonant switched-capacitor converter to obtain the target resonant converter. Compared with the previous example, this example is conducive to miniaturization by simplifying inductance.

[0081] The way of obtaining an indirect resonant switched-capacitor converter with a preset voltage conversion ratio based on a Dickson switched-capacitor converter is the same as the previous example, and the related content can be found in the foregoing, which will not be described here. The method for obtaining a target resonant converter by simplifying inductance of the indirect resonant switched-capacitor converter includes the following steps, for example, steps S11a-S13a.

[0082] In step S11a, circuit topologies of the indirect resonant switched-capacitor converter in different switching states are determined, and state space equations in different switching states are established; wherein the state space equations satisfy formula one: , is the state space equation, x(t) is the state variable, and u(t) is the input variable, A i is the state matrix in the i th switching state, B i is the input matrix in the i th switching state, and i is 1 or 2.

[0083] The indirect resonant switched-capacitor converter includes two switching states, each corresponding to a different circuit topology; wherein in the first switching state, the first control signal is effective and the second control signal is ineffective, and in the second switching state, the first control signal is ineffective and the second control signal is effective.

[0084] In actual application, there is usually a dead time t d between the first control signal and the second control signal, at this time, the resonant frequency of the series resonant cavity in the indirect resonant switched-capacitor converter satisfies formula two: , wherein f0 is the resonant frequency, L r and C r are the values of the resonant inductance and the resonant capacitance in the series resonant cavity; when the switching frequency f s is equal to the resonant frequency f0, the resonant cavity current becomes a sinusoidal curve, all the switching tubes achieve zero-current turn-off, and energy transmission has extremely high efficiency.

[0085] In step S12a, the state space equations in different switching states are weighted and calculated based on the duty cycles of different switching states to obtain a state space average equation; wherein the state space average equation satisfies formula three: , is the state space average equation, Di Let be the duty cycle corresponding to the i-th switch state.

[0086] Step S13a: Obtain simplified inductance information based on the state-space average equation, and simplify the inductance of the indirect resonant switched-capacitor converter to obtain the target resonant converter. In one specific embodiment, the method for obtaining simplified inductance information includes: sequentially setting each resonant inductor in the indirect resonant switched-capacitor converter to zero, and observing whether the composition of the state-space average equation changes; obtaining information that all resonant inductors are equal to zero when the composition of the state-space average equation remains unchanged, and obtaining simplified inductance information accordingly. For example, setting the j-th resonant inductor to zero, and observing whether the composition of the state-space average equation changes; if it changes, it indicates that setting the j-th resonant inductor to zero is not feasible; if it does not change, it indicates that setting the j-th resonant inductor to zero is feasible; by performing the step of setting each resonant inductor to zero, information on whether each resonant inductor can be equal to zero is obtained, thereby obtaining simplified inductance information; where j is 1, ..., (M-1).

[0087] by Figure 4 Taking an indirect resonant switched-capacitor converter with a preset voltage conversion ratio of 4:1 as an example, the circuit topology in the first switching state is as follows: Figure 5 and Figure 6 As shown, the circuit topology in the second switching state is as follows: Figure 7 and Figure 8 As shown in the figure, the positive reference direction of the state variables is indicated in the diagram. To better understand the formulas discussed below, the variables that may be involved in each formula are explained first; specifically as follows: S1~S 10 For the first to tenth switching transistors, R S1 ~R S10 C1~C3 are the on-resistances of the first to tenth switching transistors, and C1~C3 are the values ​​of the first to third resonant capacitors. ESR C1 ~ESR C3 L1 represents the equivalent resistance of the first to third resonant capacitors, L1~L3 represents the values ​​of the first to third resonant inductors, and DCR represents the capacitance of the capacitors. L1 ~DCR L3 C represents the DC resistance of the first to third resonant inductors. out R is the value of the output capacitor. load The value of the load resistance, v in (t) represents the voltage of the input power supply, i in (t) represents the input power supply current, v1(t)~v3(t) represent the voltages across the first to third resonant capacitors, and i1(t)~i3(t) represent the currents flowing through the first to third resonant inductors. out (t) represents the voltage across the output capacitor, i.e., the output voltage. Where:

[0088] The state variable satisfies formula four: The input variable satisfies formula five: Formula six can be obtained: In addition, according to formula seven: Formula eight can be obtained: Therefore, the independent state variable satisfies formula nine: .

[0089] For the first switch state, formula ten to formula twelve can be obtained from Figure 5 Formula thirteen to formula fifteen can be obtained from Figure 6 Among them:

[0090] Formula ten: Formula eleven: Formula twelve: Formula thirteen: Formula fourteen: Formula fifteen: .

[0091] For the second switch state, formula sixteen can be obtained from Figure 7 Formula seventeen and formula eighteen can be obtained from Figure 8 Among them:

[0092] Formula sixteen: Formula seventeen: Formula eighteen: .

[0093] In the indirect resonant switched capacitor converter, there is only a very short dead time when the two switch states are switched, which can be ignored. At this time, the duty cycle D1 of the first switch state and the duty cycle D2 of the second switch state can be considered as D1=D2=0.5; according to the duty cycle of each switch state, the state space average equation calculated by formula ten to formula eighteen satisfies formula nineteen: In addition, the first coefficient matrix satisfies formula twenty: The second coefficient matrix satisfies formula twenty-one: Among them, is the first coefficient matrix, is the second coefficient matrix, A1 is the state matrix under the first switch state, A2 is the state matrix under the second switch state, B1 is the input matrix under the first switch state, and B2 is the input matrix under the second switch state.

[0094] From Equations 20 and 21, it can be seen that when the second resonant inductor L2 = 0, the composition of the state-space average equation remains unchanged, indicating that setting the second resonant inductor L2 = 0 is feasible. In other words, the second resonant inductor L2 can be simplified (i.e., omitted). Based on this, inductor simplification is performed on the indirect resonant switched-capacitor converter with a preset voltage conversion ratio of 4:1, resulting in the target resonant converter as follows: Figure 9 As shown.

[0095] by Figure 10 Taking an indirect resonant switched-capacitor converter with a preset voltage conversion ratio of 5:1 as an example, the circuit topology in the first switching state is as follows: Figures 11 to 13 As shown, the circuit topology in the second switching state is as follows: Figure 14 and Figure 15 As shown in the figure, the positive reference direction of the state variables is indicated in the diagram. To better understand the formulas discussed below, the variables that may be involved in each formula will be explained first; specifically as follows: S1~S 13 For the first to thirteenth switching transistors, R S1 ~R S13 C1 to C4 are the on-resistances of the first to thirteenth switching transistors, and C1 to C4 are the values ​​of the first to fourth resonant capacitors. ESR C1 ~ESR C4 L1 represents the equivalent resistance of the first to fourth resonant capacitors, L1~L4 represents the values ​​of the first to fourth resonant inductors, and DCR represents the capacitance of the capacitors. L1 ~DCR L4 C represents the DC resistance of the first to fourth resonant inductors. out R is the value of the output capacitor. load The value of the load resistance, v in (t) represents the voltage of the input power supply, i in (t) represents the input power supply current, v1(t)~v4(t) represent the voltages across the first to fourth resonant capacitors, and i1(t)~i4(t) represent the currents flowing through the first to fourth resonant inductors. out (t) represents the voltage across the output capacitor, i.e., the output voltage. Where:

[0096] because and We can obtain independent state variables that satisfy Formula 22: .

[0097] For the first switch state, from Figure 11 From this, we can derive formulas 23 to 25, from... Figure 12 From this, we can derive formulas 26 to 28. Figure 13 From this, we can derive formulas 29 to 31. Where:

[0098] Formula twenty-three: , Formula twenty-four: , Formula twenty-five: . Formula twenty-six: , Formula twenty-seven: , Formula twenty-eight: . Formula twenty-nine: , Formula thirty: , Formula thirty-one: .

[0099] For the second switching state, formula thirty-two can be derived from formula twenty-four, and formula thirty-three and formula thirty-four can be derived from formula twenty-five. Wherein: Figure 14 Figure 15 Formula thirty-two: . Formula thirty-three:

[0100] , Formula thirty-four: . The duty cycle D1 of the first switching state and the duty cycle D2 of the second switching state can be considered as D1 = D2 = 0.5, and according to the duty cycle of each switching state, the state space average equation is calculated by formula twenty-three to formula thirty-four, wherein the first coefficient matrix of the state space average equation satisfies formula thirty-five: , and the second coefficient matrix satisfies formula thirty-six:

[0101] . It can be seen from formula thirty-five and formula thirty-six that when the second resonant inductance L2 = 0, the composition of the state space average equation does not change, which indicates that it is feasible to make the second resonant inductance L2 = 0, that is, the second resonant inductance L2 can be simplified (i.e., omitted); based on this, the inductance is simplified for the indirect resonant switched capacitor converter with a preset voltage conversion ratio of 5:1, and the target resonant converter obtained is as shown in .

[0102] Figure 16 In another example, the method for obtaining a target resonant converter includes: based on a Dickson switched capacitor converter, obtaining an indirect resonant switched capacitor converter with a preset voltage conversion ratio; obtaining inductance simplification information corresponding to the preset voltage conversion ratio from an inductance simplification rule, and simplifying the inductance of the indirect resonant switched capacitor converter to obtain the target resonant converter. Compared with the first example, the inductance is simplified in this example, which is beneficial to miniaturization; compared with the second example, the inductance is simplified by the pre-established inductance simplification rule in this example, which is beneficial to simplify the calculation and is more suitable for engineering application.

[0103] In another example, the method for obtaining a target resonant converter includes: based on a Dickson switched capacitor converter, obtaining an indirect resonant switched capacitor converter with a preset voltage conversion ratio; obtaining inductance simplification information corresponding to the preset voltage conversion ratio from an inductance simplification rule, and simplifying the inductance of the indirect resonant switched capacitor converter to obtain the target resonant converter. Compared with the first example, the inductance is simplified in this example, which is beneficial to miniaturization; compared with the second example, the inductance is simplified by the pre-established inductance simplification rule in this example, which is beneficial to simplify the calculation and is more suitable for engineering application.

[0104] ​The way of obtaining the indirect resonant switched-capacitor converter with preset voltage conversion ratio based on the Dickson switched-capacitor converter is the same as the previous example, and the related content can be found in the foregoing, which will not be described here. The method of obtaining the inductance simplification rule includes the following steps, for example, steps S11b-S14b.

[0105] In step S11b, a plurality of first indirect resonant switched-capacitor converters with even voltage conversion ratios and a plurality of second indirect resonant switched-capacitor converters with odd voltage conversion ratios are obtained based on the Dickson switched-capacitor converter; wherein the voltage conversion ratios of the first indirect resonant switched-capacitor converters are different, and the voltage conversion ratios of the second indirect resonant switched-capacitor converters are different. The number of the first indirect resonant switched-capacitor converters obtained in this step is denoted as X, and the number of the second indirect resonant switched-capacitor converters obtained in this step is denoted as Y. In actual application, in order to more accurately obtain the inductance simplification rule, the values of X and Y cannot be too small, of course, in order to balance the calculation amount, the values of X and Y cannot be too large, and should be designed in combination with specific conditions. It should be noted that the way of obtaining the first and second indirect resonant switched-capacitor converters based on the Dickson switched-capacitor converter is the same as the previous example, and the related content can be found in the foregoing, which will not be described here. In addition, the even number in the even voltage conversion ratio is usually greater than 2, and the odd number in the odd voltage conversion ratio is usually greater than 2.

[0106] In step S12b, each first state space average equation corresponding to each first indirect resonant switched-capacitor converter is obtained, and a first inductance simplification rule corresponding to the even voltage conversion ratio is obtained. In one specific embodiment, the method of obtaining each first state space average equation includes: determining the circuit topology of each first indirect resonant switched-capacitor converter in different switching states, and establishing the state space equation in different switching states; based on the duty cycle of different switching states, the state space equation in different switching states is calculated to obtain each first state space average equation. The method of obtaining the first inductance simplification rule includes: based on each first state space average equation, each first inductance simplification information corresponding to each first indirect resonant switched-capacitor converter is obtained, and the rule is extracted from each first inductance simplification information to obtain the first inductance simplification rule. Specifically, the method of obtaining the first inductance simplification information includes: sequentially setting each resonant inductance in the corresponding first indirect resonant switched-capacitor converter to zero, and observing whether the composition of the corresponding first state space average equation changes; obtaining the information that all resonant inductances are equal to zero when the composition of the corresponding first state space average equation does not change, and obtaining the corresponding first inductance simplification information. Wherein, the first inductance simplification rule includes that the kth resonant inductance is equal to zero, k is an even number greater than 1 and less than (M-1), at this time, the preset voltage conversion ratio M is an even number greater than 2.

[0107] Step S13b: Obtain the average equation of each second state space corresponding to each second indirect resonant switched capacitor converter, and use it to obtain the second inductor simplification rule corresponding to the odd voltage conversion ratio. In one specific embodiment, the method for obtaining the average equation of each second state space includes: determining the circuit topology of each second indirect resonant switched capacitor converter under different switching states, and establishing the state space equation under different switching states; based on the duty cycle of different switching states, performing weighted calculation on the state space equation under different switching states to obtain the average equation of each second state space. The method for obtaining the second inductor simplification rule includes: based on each second state space average equation, obtaining the second inductor simplification information corresponding to each second indirect resonant switched capacitor converter, and extracting rules from each second inductor simplification information to obtain the second inductor simplification rule. Specifically, the method for obtaining the second inductor simplification information includes: sequentially setting each resonant inductor in the corresponding second indirect resonant switched capacitor converter to zero, and observing whether the composition of the corresponding second state space average equation changes; obtaining information that all resonant inductors are equal to zero when the composition of the corresponding second state space average equation does not change, and using this to obtain the corresponding second inductor simplification information. The second inductor simplification rule includes that the kth resonant inductor is equal to zero, where k is an even number greater than 1 and less than (M-1), and the preset voltage conversion ratio M is an odd number greater than 2.

[0108] Step S14b: An inductor simplification rule is formed by combining the first inductor simplification rule and the second inductor simplification rule. In practical applications, if the preset voltage conversion ratio is even, the inductor is simplified based on the first inductor simplification rule; if the preset voltage conversion ratio is odd, the inductor is simplified based on the second inductor simplification rule.

[0109] Step S2: Cascade the target resonant converter and the BUCK converter to obtain a cascaded DC-DC converter. In one specific embodiment, the target resonant converter and the BUCK converter are cascaded by connecting an intermediate capacitor in parallel; wherein the target resonant converter is used as the pre-stage converter and the BUCK converter is used as the post-stage converter, such as... Figure 17 As shown; of course, it is also feasible to use the BUCK converter as the pre-stage converter and the target resonant converter as the post-stage converter, as shown. Figure 18 As shown; in practical applications, the design of the front and rear stage positions of the two converters usually needs to consider factors such as volume, power density, and filtering effect. The design should be based on the specific situation and no excessive restrictions are imposed on it.

[0110] When the cascade DC-DC converter is designed by the above method, it should be clear to those skilled in the art that the preset voltage conversion ratio is not the final voltage conversion ratio, and it is usually smaller than the final voltage conversion ratio, so as to reduce the number of switching tubes and realize miniaturization. For example, the final voltage conversion ratio is 100:1, and the preset voltage conversion ratio can be 50:1, that is, the voltage conversion ratio of the target resonant converter is 50:1, at this time, the voltage conversion ratio of the BUCK converter can be 2:1, so that the voltage conversion of 100:1 can be realized by cascade design; of course, the preset voltage conversion ratio can also be 25:1, that is, the voltage conversion ratio of the target resonant converter is 25:1, at this time, the voltage conversion ratio of the BUCK converter can be 4:1, so that the voltage conversion of 100:1 can be realized by cascade design; wherein the final voltage conversion ratio refers to the voltage conversion ratio that the cascade DC-DC converter finally wants to realize. It can be seen that for the same final voltage conversion ratio, the cascade DC-DC converter has multiple implementation manners; in actual application, the implementation manner should be selected in combination with the specific situation to achieve the optimal effect.

[0111] As shown in Figure 17 and Figure 18 , the embodiment also provides a cascade DC-DC converter, wherein the cascade DC-DC converter is designed by the design method described above.

[0112] According to the cascade mode shown in Figure 18 , taking the preset voltage conversion ratio of 4:1 as an example, the cascade DC-DC converter finally designed by inductance simplification is shown in Figure 19 , wherein the left dashed box in the figure is a BUCK converter, and the right dashed box in the figure is a target resonant converter; the circuit is built and simulated in the circuit simulation software, wherein the input voltage is 12V, and the output voltage is 1V, and the simulation waveforms of the related signals are shown in Figure 20 ; it can be seen from the figure that the cascade DC-DC converter of the embodiment can effectively realize the voltage conversion of 12V-1V.

[0113] At the same time, a physical prototype is also developed, and the circuit shown in Figure 19 is taken as the basis, and the physical prototype of 12V to 1V full load current 30A is shown in Figure 21 , and the related experimental waveforms are shown in Figures 22 to 25 , wherein: Figure 22 shows that the input voltage is 12V, and the output voltage is 1V; Figure 23 shows the voltage waveforms of the three GaN switching tubes S1, S2 and S4, wherein the maximum voltage value of the switching tube S2 is 2V, which is consistent with the simulation waveform result; Figure 24 shows the current on the resonant inductors L1 and L2;Figure 25 It is shown that the dynamic response capability of the cascaded DC-DC converter is reduced from 30A to 15A.

[0114] The simulation and actual circuit test verify the feasibility of the design scheme. In addition, when the input voltage is 12V, the output voltage is 1V, and the output power is 30W, the full load efficiency of the traditional BUCK type DC-DC step-down converter and the cascaded DC-DC converter of the embodiment is compared, and the results are shown in the following table. It can be seen that the cascaded DC-DC converter of the embodiment can significantly improve the full load efficiency.

[0115]

[0116] Correspondingly, the embodiment also provides a load point power supply, which comprises the cascaded DC-DC converter, and of course, can also comprise other device structures, which are not limited too much.

[0117] In summary, the cascaded DC-DC converter, the design method thereof and the load point power supply can combine the advantages of the two converters by cascading the target resonant converter and the BUCK converter, and have the advantages of strong voltage regulation capability and high efficiency, so as to meet the application scenarios of high voltage conversion ratio and large current output. For the application scenarios of large voltage conversion ratio and large current output, the application can be realized by fewer switching tubes, which can significantly reduce the voltage stress of the switching tube, thereby effectively reducing the size of the switching tube, which is beneficial to chip miniaturization. In addition, the application also has obvious advantages for improving the full load efficiency of the large current output converter. Furthermore, the target resonant converter and the BUCK converter are controlled separately, the control is relatively simple, the control circuit design is easy, and it is more suitable for actual engineering application. Therefore, the application effectively overcomes the various shortcomings in the prior art and has high industrial utilization value.

[0118] The above embodiments only exemplarily illustrate the principles and effects of the application, and are not used to limit the application. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical idea disclosed by the application should be covered by the claims of the application.

Claims

1. A design method for a cascaded DC-DC converter, characterized in that, The design method includes: Based on the Dickson switched capacitor converter, an indirect resonant switched capacitor converter with a preset voltage conversion ratio is obtained. The inductance of the indirect resonant switched capacitor converter is simplified to obtain the target resonant converter. The target resonant converter is cascaded with the BUCK converter to obtain a cascaded DC-DC converter. The method for obtaining the target resonant converter by simplifying the inductance of the indirect resonant switched capacitor converter includes: The circuit topology of the indirect resonant switched capacitor converter under different switching states is determined, and the state space equations under different switching states are established. Based on the duty cycle of different switching states, the state space equations under different switching states are weighted and calculated to obtain the average state space equation. Based on the state-space average equation, the inductance simplification information is obtained, and the inductance of the indirect resonant switched capacitor converter is simplified to obtain the target resonant converter. The method for obtaining the simplified inductance information includes: The resonant inductors in the indirect resonant switched capacitor converter are sequentially made equal to zero, and the composition of the state-space average equation is observed to see if it changes. Information is obtained that all resonant inductances are zero when the composition of the state-space average equation remains unchanged, and simplified inductance information is obtained accordingly.

2. The design method of the cascaded DC-DC converter according to claim 1, characterized in that, The simplified inductance information satisfies the inductance simplification rules, which include a first inductance simplification rule and a second inductance simplification rule; the preset voltage conversion ratio is denoted as M:1, where M is a natural number greater than 2; When M is an even number greater than 2, the first inductor simplification rule includes that the kth resonant inductance is equal to zero, where k is an even number greater than 1 and less than (M-1); When M is an odd number greater than 2, the second inductance simplification rule includes that the k-th resonant inductance is equal to zero, where k is an even number greater than 1 and less than (M-1).

3. The design method of the cascaded DC-DC converter according to claim 1, characterized in that, The target resonant converter and the BUCK converter are cascaded by connecting an intermediate capacitor in parallel, wherein the target resonant converter is the pre-stage converter and the BUCK converter is the post-stage converter, or the BUCK converter is the pre-stage converter and the target resonant converter is the post-stage converter.

4. A design method for a cascaded DC-DC converter, characterized in that, The design method includes: Based on the Dickson switched capacitor converter, an indirect resonant switched capacitor converter with a preset voltage conversion ratio is obtained. The inductance simplification information corresponding to the preset voltage conversion ratio is obtained from the inductance simplification rules, and the inductance simplification is performed on the indirect resonant switched capacitor converter to obtain the target resonant converter. The target resonant converter is cascaded with the BUCK converter to obtain a cascaded DC-DC converter. The method for obtaining the inductance simplification rule includes: Based on the Dickson switched capacitor converter, several first indirect resonant switched capacitor converters with even voltage conversion ratios and several second indirect resonant switched capacitor converters with odd voltage conversion ratios are obtained. Obtain the first state-space average equation corresponding to each of the first indirect resonant switched capacitor converters, and use it to obtain the first inductor simplification rule corresponding to the even voltage conversion ratio. The average equations of the second state space corresponding to each of the second indirect resonant switched capacitor converters are obtained, and the simplified rules of the second inductor corresponding to the odd voltage conversion ratio are obtained accordingly. The inductance simplification rule is formed by the first inductance simplification rule and the second inductance simplification rule; Methods for obtaining the corresponding state-space average equations include: Determine the circuit topology of the corresponding indirect resonant switched capacitor converter under different switching states, and establish the state-space equations under different switching states. Based on the duty cycle of different switching states, the state space equations under different switching states are weighted and calculated to obtain the corresponding average state space equation. Methods for obtaining simplified information about the corresponding inductance include: In turn, make each resonant inductor in the corresponding indirect resonant switched capacitor converter equal to zero, and observe whether the composition of the corresponding state-space average equation changes. Obtain information that all resonant inductances are zero when the composition of the corresponding state-space average equation remains unchanged, and use this information to obtain the corresponding simplified inductance information.

5. The design method of the cascaded DC-DC converter according to claim 4, characterized in that, The method for obtaining the first inductor simplification rule includes: extracting rules from each first inductor simplification information to obtain the first inductor simplification rule; The method for obtaining the second inductance simplification rule includes: extracting rules from each second inductance simplification information to obtain the second inductance simplification rule.

6. The design method of the cascaded DC-DC converter according to claim 4 or 5, characterized in that, The preset voltage conversion ratio is denoted as M:1, where M is a natural number greater than 2; When M is an even number greater than 2, the first inductor simplification rule includes that the kth resonant inductance is equal to zero, where k is an even number greater than 1 and less than (M-1); When M is an odd number greater than 2, the second inductance simplification rule includes that the k-th resonant inductance is equal to zero, where k is an even number greater than 1 and less than (M-1).

7. The design method of the cascaded DC-DC converter according to claim 4, characterized in that, The target resonant converter and the BUCK converter are cascaded by connecting an intermediate capacitor in parallel, wherein the target resonant converter is the pre-stage converter and the BUCK converter is the post-stage converter, or the BUCK converter is the pre-stage converter and the target resonant converter is the post-stage converter.

8. A cascaded DC-DC converter, characterized in that, The cascaded DC-DC converter is designed using the design method described in any one of claims 1 to 7.

9. A point-of-load power supply, characterized in that, The point-of-load power supply includes the cascaded DC-DC converter as described in claim 8.

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