A cascaded dc / dc converter for device multiplexing

Abstract

The application discloses a kind of cascaded DC / DC converters of device multiplexing, belong to the field of power electronics, converter includes: cascaded Buck-Boost converter and CLLLC resonant converter, and closed-loop controller, current ripple optimization controller and driver;Closed-loop controller is used to calculate the duty cycle d of switch tube in Buck-Boost converter not multiplexed according to the output voltage and input voltage of DC / DC converter;Current ripple optimization controller is used to solve the phase shift angle δ between the multiplexed bridge arm and the non-multiplexed bridge arm in Buck-Boost converter according to the functional relationship between the inductance current ripple and the duty cycle d and the phase shift angle δ of DC / DC converter, with the minimum inductance current ripple as the target;Driver is used to control the on-off of switch tube in DC / DC converter according to the duty cycle d and the phase shift angle δ. When the input voltage changes in a wide range, the output voltage control is realized, the current ripple is optimized, and the performance of the converter is improved comprehensively.

Description

Technical Field

[0001] This invention belongs to the field of power electronics, and more specifically, relates to a cascaded DC / DC converter with device multiplexing. Background Technology

[0002] With the rapid development of new energy technologies, electric vehicles, DC microgrids, and rail transportation have attracted widespread attention due to their promising application prospects. DC / DC converters play a crucial role in energy transfer and voltage conversion in these applications. Constructing high-power, high-density DC / DC converters is of great significance and practical value for promoting the development of new energy technologies and alleviating the energy crisis. In these applications, it is necessary to ensure that the output voltage remains constant when the input voltage of the DC / DC converter varies within a wide range; that is, the DC / DC converter needs to have a wide voltage operating range.

[0003] Existing solutions cascade a four-switch Buck-Boost circuit with a CLLLC resonant converter to form a bidirectional DC / DC converter, combining the advantages of both to improve power density. This makes it suitable for applications requiring wide input voltage ranges and high efficiency, such as DC microgrids and electric vehicles. However, in high-voltage applications, the voltage and current stress on the switching devices in this topology is excessive, leading to low converter efficiency and poor performance. Achieving stable operation of the cascaded converter and maintaining high efficiency during output voltage regulation is a problem that needs to be solved. Summary of the Invention

[0004] To address the shortcomings and improvement needs of existing technologies, this invention provides a cascaded DC / DC converter with device reuse, which aims to solve the output voltage control problem when the input voltage varies over a wide range, while optimizing current ripple and comprehensively improving the converter's performance.

[0005] To achieve the above objectives, the present invention provides a cascaded DC / DC converter with device reuse, comprising: a cascaded Buck-Boost converter and a CLLLC resonant converter, a closed-loop controller, a current ripple optimization controller, and a driver; the Buck-Boost converter includes two bridge arms, and one of the bridge arms is reused with the CLLLC resonant converter; the closed-loop controller is used to: calculate the duty cycle of the switching transistors in the unreused bridge arm of the Buck-Boost converter based on the output voltage and input voltage of the DC / DC converter. d The current ripple optimization controller is used to: adjust the inductor current ripple of the DC / DC converter based on the duty cycle. dThe functional relationship between the phase shift angle δ and the inductor current ripple is used to solve for the phase shift angle δ, where the phase shift angle δ is the phase shift angle between the switching transistors of the unreused bridge arm and the multiplexed bridge arm in the Buck-Boost converter; the driver is used to: determine the phase shift angle based on the duty cycle. d The phase shift angle δ controls the on / off state of the switching transistors in the DC / DC converter.

[0006] Furthermore, the Buck-Boost converter is a six-switch Buck-Boost converter; the six-switch Buck-Boost converter includes: switching transistors S1, S2, S3, S4, Q1, and Q2 with anti-parallel diodes, and a flying capacitor C. fly and inductor L b S1, S2, S3, and S4 are connected in series as unreused bridge arms; Q1 and Q2 are connected in series as multiplexed bridge arms; S1 is connected to the positive terminal of the primary power supply; S4 and Q2 are both connected to the negative terminal of the primary power supply; flying capacitor C fly One end of the inductor is connected to the connection point of S1 and S2, and the other end is connected to the connection point of S3 and S4; Inductor L b One end is connected to the connection point of S2 and S3, and the other end is connected to the connection point of Q1 and Q2.

[0007] Furthermore, the CLLLC resonant converter includes: a transformer, a primary-side full-bridge LLC circuit connected to the primary side of the transformer, and a secondary-side full-bridge LC circuit connected to the secondary side of the transformer; the primary-side full-bridge LLC circuit and the six-switch Buck-Boost converter share a bridge arm, including a primary-side H-bridge circuit composed of switches Q1, Q2, Q3 and Q4.

[0008] Furthermore, the driver is used to control the on / off states of S1, S2, S3, S4, Q1, Q2, Q3, and Q4; wherein the on-time of S1 and S2 is determined by the duty cycle. d It is determined that the conduction time of Q1 lagging behind S1 is determined by the phase shift angle δ; Q1 and Q4 are synchronously turned on or off, Q2 and Q3 are synchronously turned on or off, and Q1 and Q2 are complementary in conduction; the driving signals of Q1, Q2, Q3 and Q4 are square wave signals with a frequency equal to the resonant frequency of the DC / DC converter and a duty cycle of 50%.

[0009] Furthermore, the Buck-Boost converter is a six-switch Buck-Boost converter, 0 < d When ≤0.5, the six-switch Buck-Boost converter operates in Buck mode; when 0.5 < d When ≤1, the six-switch Buck-Boost converter operates in Boost mode.

[0010] Furthermore, 0 < d The per-unit value of inductor current ripple when ≤0.25 Duty cycle d The functional relationship between the phase shift angle δ and the phase shift angle δ is:

[0011]

[0012] Furthermore, 0.25 < d When ≤0.5, the per-unit value of inductor current ripple Duty cycle d The functional relationship between the phase shift angle δ and the phase shift angle δ is:

[0013]

[0014] Furthermore, 0.5 < d The per-unit value of inductor current ripple when ≤0.75 Duty cycle d The functional relationship between the phase shift angle δ and the phase shift angle δ is:

[0015]

[0016] Furthermore, 0.75 < d When ≤1, the per-unit value of inductor current ripple Duty cycle d The functional relationship between the phase shift angle δ and the phase shift angle δ is:

[0017]

[0018] Furthermore, duty cycle d satisfy:

[0019]

[0020] in, The output voltage of the DC / DC converter. The input voltage of the DC / DC converter. This represents the transformer's turns ratio in a CLLLC resonant converter.

[0021] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0022] (1) A cascaded DC-DC converter with device multiplexing is provided, which cascades a six-switch Buck-Boost converter and a CLLLC resonant converter. Compared with the cascaded four-switch Buck-Boost converter and CLLLC resonant converter, the voltage stress on the switching transistors is halved, which can effectively expand the input voltage range of the converter, reduce the voltage level of the switching transistors, improve the performance of the converter, and reduce electromagnetic interference. It is suitable for high voltage applications with a wide input voltage range.

[0023] (2) Design the control strategy for the proposed cascaded DC-DC converter with device reuse, form a phase-shift-based dual closed-loop control strategy, and design the duty cycle. d To ensure stable output voltage, this duty cycle is designed. d The phase shift angle δ is adjusted to ensure that the current ripple is minimized. This allows the output voltage to be stabilized when the input voltage varies over a wide range. At the same time, the current ripple is minimized, which enables the cascaded converter to operate stably and comprehensively improves the converter's performance.

[0024] (3) The design allows the CLLLC resonant converter and the six-switch Buck-Boost converter to share a bridge arm, and the on / off control of this bridge arm can simultaneously realize the functions of the CLLLC resonant converter and the six-switch Buck-Boost converter. Thus, while ensuring the dynamic performance of the converter, the hardware cost is reduced, hardware resources are saved, and the power density of the converter is increased. Attached Figure Description

[0025] Figure 1 A structural diagram of a cascaded DC / DC converter with device reuse provided in an embodiment of the present invention;

[0026] Figure 2 A topology diagram of a cascaded DC / DC converter with device reuse provided in an embodiment of the present invention;

[0027] Figure 3A , Figure 3B The following are modulation waveforms of the Buck mode and Boost mode of the cascaded DC / DC converter with device reuse provided in the embodiments of the present invention;

[0028] Figure 4 A control block diagram of dual closed-loop control based on phase-shift control provided in an embodiment of the present invention;

[0029] Figure 5 The input voltage switching experimental waveform provided in the embodiment of the present invention;

[0030] Figure 6 The load switching experimental waveform provided in the embodiment of the present invention;

[0031] Figure 7A, Figure 7B The waveforms shown are comparative experimental waveforms of dual closed-loop systems provided in the embodiments of the present invention, one without phase-shift control and the other with phase-shift control. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0033] In this invention, the terms "first," "second," etc. (if present) in the invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0034] Figure 1 A structural diagram of a cascaded DC / DC converter with device multiplexing provided in an embodiment of the present invention. See also... Figure 1 , combined Figures 2-7B The cascaded DC / DC converter with device reuse in this embodiment will be described in detail.

[0035] Cascaded DC / DC converters with device reuse include: cascaded Buck-Boost converters and CLLLC resonant converters, as well as closed-loop controllers, current ripple optimization controllers, and drivers, such as... Figure 1 As shown.

[0036] The Buck-Boost converter comprises two bridge arms, with one arm reused with a CLLLC resonant converter. The closed-loop controller is used to calculate the duty cycle of the switching transistors in the unreused bridge arm of the Buck-Boost converter, based on the output and input voltages of the DC / DC converter. d The current ripple optimization controller is used to: adjust the inductor current ripple and duty cycle of the DC / DC converter. d The functional relationship between the phase shift angle δ and the inductor current ripple is determined by solving for the phase shift angle δ, which is the phase shift angle between the switches of the unmultiplexed and multiplexed bridge arms in the Buck-Boost converter. The driver is used to determine the phase shift angle based on the duty cycle. d The phase shift angle δ controls the on / off state of the switching transistors in the DC / DC converter.

[0037] The Buck-Boost converter can be either a four-switch Buck-Boost converter or a six-switch Buck-Boost converter, and the dual closed-loop control strategy in the closed-loop controller and the current ripple optimization controller is applicable.

[0038] The following example uses a six-switch Buck-Boost converter to illustrate the cascaded DC / DC converter with device multiplexing in this embodiment.

[0039] The DC side of a six-switch buck-boost (SSBB) converter is connected to the primary power supply, which is, for example, a voltage source V. in The six-switch Buck-Boost converter includes: switches S1, S2, S3, S4, Q1, and Q2 with anti-parallel diodes, and a flying capacitor C. fly and inductor L b ,like Figure 2 As shown. S1, S2, S3, and S4 are connected in series to form a bridge arm, which is an unreused bridge arm; Q1 and Q2 are connected in series to form another bridge arm, which is a multiplexed bridge arm between the six-switch Buck-Boost converter and the CLLLC resonant converter. The drain of S1 is connected to the positive terminal of the primary power supply (the positive terminal of the DC bus), and the sources of S4 and Q2 are both connected to the negative terminal of the primary power supply (the negative terminal of the DC bus). Flying capacitor C fly One end of the inductor is connected to the connection point of S1 and S2, and the other end is connected to the connection point of S3 and S4; Inductor L b One end is connected to the connection point of S2 and S3, and the other end is connected to the connection point of Q1 and Q2.

[0040] The CLLLC resonant converter and the six-switch Buck-Boost converter share the bridge arm formed by Q1 and Q2. The CLLLC resonant converter includes: transformer T r Connecting transformer T r The primary side full-bridge LLC circuit on the original side, and the connecting transformer T r Secondary-side full-bridge LC circuit. Transformer T r For example, a high-frequency isolation transformer with a turns ratio of n:1.

[0041] The primary-side full-bridge LLC circuit and the six-switch Buck-Boost converter share the bridge arm formed by Q1 and Q2, including the primary-side H-bridge circuit composed of switches Q1, Q2, Q3 and Q4, and also includes the primary-side resonant inductor L. r1 Primary resonant capacitor C r1 Magnetizing inductance L m The bridge arm is formed by connecting transistors Q3 and Q4 in series. The source of Q4 is connected to the negative terminal of the primary power supply, and the drain of Q3 is connected to the drain of Q1. The secondary-side full-bridge LC circuit includes a secondary-side H-bridge circuit composed of transistors Q5, Q6, Q7, and Q8, and also includes a secondary-side resonant inductor L. r2 and secondary resonant capacitor Cr2 Primary resonant inductance L r1 Primary resonant capacitor C r1 Magnetizing inductance L m Transformer, secondary resonant inductor L r2 and secondary resonant capacitor C r2 The CLLLC resonant circuit is composed of, such as Figure 2 As shown. The bridge arm formed by Q1 and Q2, the bridge arm formed by Q3 and Q4, and the bus capacitor C. bus Parallel connection. Bus capacitor C bus Bus voltage v bus Controlled by a six-switch Buck-Boost converter, v bus This voltage then serves as the input voltage for the CLLLC resonant converter.

[0042] The DC side of the six-switch Buck-Boost converter is connected to the primary voltage source, and an input voltage regulator capacitor C1 is connected in parallel to the DC voltage source V. in The DC side of the secondary full-bridge LC circuit has an output voltage regulator capacitor C2 connected in parallel. The DC side of the secondary full-bridge LC circuit serves as the output terminal of the converter and is connected to the secondary load R. L connect.

[0043] According to an embodiment of the present invention, the switching transistors (Q5, Q6, Q7 and Q8) in the secondary-side full-bridge LC circuit are equipped with anti-parallel diodes; each switching transistor in the secondary-side full-bridge LC circuit is in a state without a driving signal or in a synchronous rectification state.

[0044] In this embodiment, S1, S2, S3, S4 and their anti-parallel diodes, input voltage regulator capacitor C1, and flying capacitor C fly This configuration, forming a three-level half-bridge, ensures that the voltage stress on all switching devices is half the input voltage (V). in / 2, and has redundant switching states that can achieve voltage balancing of the flying capacitor through modulation. During normal operation, the flying capacitor voltage remains at half the input voltage, and the terminal voltages of switches S3 and S4 are... v m .

[0045] The switching state sequence of the switching transistor modulation mode is O1-N-O2 or O1-P-O2, where the duration of states O1 and O2 is the same. According to the self-balancing characteristic of the flying capacitor, if the DC component of the inductor current has equal charge and discharge charge on the flying capacitor, then the flying capacitor voltage is balanced. By alternating redundant switching states O1 and O2, the switching state is changed alternately within two switching cycles; that is, if the first switching cycle is O1-N-O2 or O1-P-O2, then the second switching cycle is O2-N-O1 or O2-P-O1. In state P, S1 and S2 are turned on, and S3 and S4 are turned off. The voltage stress on S3 and S4 is V. in / 2; In state O1, S1 and S3 are on, and S2 and S4 are off. The voltage stress on S2 and S4 is V. in / 2; In state O2, S2 and S4 are on, and S1 and S3 are off. The voltage stress on S1 and S3 is V. in / 2; In state N, S3 and S4 are on, and S1 and S2 are off. The voltage stress on S1 and S2 is V. in / 2. Therefore, a three-level half-bridge converter can use switching devices with lower voltage ratings and better performance to achieve a wide input voltage range, effectively improving the converter's performance. Since the inductor is a passive device, its inductor voltage has an equal average value over one switching cycle. Under this modulation, the gain range of the six-switch Buck-Boost converter is 0-2. All switches have the same switching frequency, and the drive waveforms for all switching devices can be generated based on the switching state sequence and phase shift angle δ.

[0046] For a six-switch Buck-Boost converter, 0 < d When ≤0.5, the six-switch Buck-Boost converter operates in Buck mode; when 0.5 < d When the value is ≤1, the six-switch Buck-Boost converter operates in Boost mode.

[0047] When the capacitor voltage jumps v cfly For V in When / 2, the voltage stress on switching transistors S1-S4 is only half of the input voltage stress. v cfly Deviation from V in When the voltage is / 2, the voltage stress distribution of switching transistors S1-S4 becomes uneven, affecting the stability and safety of the converter. According to the self-balancing characteristic of the flying capacitor, if the DC component of the inductor current has equal charge and discharge charge on the flying capacitor, then the voltage across the flying capacitor is balanced. When the switching state is P or N, the current flowing through the flying capacitor C... fly The current is 0; when the switch state is O1 or O2, the current flowing through the flying capacitor is iLb When the inductor current i Lb When the current is greater than 0, the flying capacitor charges in state O1 and discharges in state O2; when the inductor current... i Lb When the current is less than 0, the flying capacitor discharges in state O1 and charges in state O2, with the same inductor current in the same direction and magnitude. i Lb The flying capacitor C under O1 and O2 states fly Their charging and discharging behaviors are opposite. Redundant switching states O1 and O2 are used alternately, changing the switching state in two switching cycles. That is, if the first switching cycle is O1-N-O2, then the second switching cycle is O2-N-O1; if the first switching cycle is O1-P-O2, then the second switching cycle is O2-P-O1. Flying capacitor C fly The charge / discharge amount in the first switching cycle O1 is equal to the charge / discharge amount in the second switching cycle O2, and the flying capacitor C fly The charging and discharging amount of O2 in the first switching cycle is equal to the charging and discharging amount of O1 in the second switching cycle. (Flying capacitor voltage) v cfly The change is zero within every two switching cycles, as shown in the following expression, thus achieving... v cfly Balance:

[0048]

[0049] The driving waveforms of all switching devices are generated based on the switching state sequence and phase shift angle δ, such as... Figure 3A and Figure 3B As shown. Using the above modulation method, since the average value of the inductor voltage is equal over one switching cycle, the gain of the input and output voltages of the six-switch Buck-Boost converter is 2. d The voltage gain of the CLLLC resonant converter is 1 / n Therefore, the voltage gain of the ISSBB-CLLLC converter G It can be represented by the following expression:

[0050]

[0051] This expression shows that the voltage gain of the converter depends only on the duty cycles of switches S1 and S2. d and transformer turns ratio n Related. Therefore, duty cycle d satisfy:

[0052]

[0053] in, The output voltage of the DC / DC converter. The input voltage of the DC / DC converter. This represents the transformer's turns ratio in a CLLLC resonant converter.

[0054] According to an embodiment of the present invention, 0 < d The per-unit value of inductor current ripple when ≤0.25 Duty cycle d The functional relationship between the phase shift angle δ and the phase shift angle δ is:

[0055]

[0056] According to an embodiment of the present invention, 0.25 < d When ≤0.5, the per-unit value of inductor current ripple Duty cycle d The functional relationship between the phase shift angle δ and the phase shift angle δ is:

[0057]

[0058] According to an embodiment of the present invention, 0.5 < d The per-unit value of inductor current ripple when ≤0.75 Duty cycle d The functional relationship between the phase shift angle δ and the phase shift angle δ is:

[0059]

[0060] According to an embodiment of the present invention, 0.75 < d When ≤1, the per-unit value of inductor current ripple Duty cycle d The functional relationship between the phase shift angle δ and the phase shift angle δ is:

[0061]

[0062] per-unit value of inductor current ripple With inductor current ripple Δ I max The relationship between them is:

[0063]

[0064] in, This is the DC bus voltage, i.e., the input voltage of the DC / DC converter; For the switching cycle, For inductor L b The inductance value.

[0065] The driver is specifically used to control the on / off states of S1, S2, S3, S4, Q1, Q2, Q3, Q4, Q5, Q6, Q7, and Q8. The on-time of S1 and S2 is determined by their duty cycles. d It is determined that the conduction time of Q1 lagging behind S1 is determined by the phase shift angle δ, that is, the phase shift angle between S1 and Q1 is equal to δ; Q1 and Q4 are synchronously turned on or off, Q2 and Q3 are synchronously turned on or off, and Q1 and Q2 are complementary in conduction; the driving signals of Q1, Q2, Q3 and Q4 are square wave signals with a frequency equal to the resonant frequency of the DC / DC converter and a duty cycle of 50%; Q5, Q6, Q7 and Q8 are in a state without driving signals (rectified by the anti-parallel diodes of Q5-Q8), or in a state of synchronous rectification of Q1, Q2, Q3 and Q4 (that is, the driving signals of Q5-Q8 correspond to the same driving signals of Q1-Q4 respectively). In the DC / DC converter, the switching frequency of the switching transistors is equal to the resonant frequency, which makes the efficiency of the CLLLC resonant converter the highest.

[0066] In this embodiment, to achieve output voltage control and current ripple optimization, a phase-shift-based dual closed-loop control strategy is proposed, such as... Figure 4 As shown. Due to the advantages of dual-loop control, such as good steady-state performance, fast dynamic response, and strong anti-interference capability, dual-loop control is used to stabilize the output voltage. The proportional-integral controller (PIC) has advantages such as fast response, simple structure, and zero steady-state error, and controls the output voltage separately. v out Outer loop and inductor current i Lb Inner loop. Under the dual closed-loop control strategy, the output voltage remains stable even when the input voltage varies widely, and the inner current loop provides overcurrent protection for the converter.

[0067] Dual closed-loop control enables rapid adjustment of the DC / DC converter's output voltage. As current ripple increases, inductor core and coil losses also increase. The six-switch Buck-Boost converter provides an excellent approach to optimizing current ripple. According to... v m , v n , d The relationship with δ i Lb The current ripple can be divided into 24 modes, as shown in Table 1.

[0068] Table 1

[0069]

[0070] Among them, A1-A6, B1-B6, C1-C6, and D1-D6 are d The boundary range of δ, This is the standardized current ripple (i.e., the per-unit value of the current ripple). As shown in Table 1, and d It is related to δ. The closed-loop controller obtains the duty cycle of switches S1 and S2 based on the output reference voltage value. d The modulation strategy of the three-level half-bridge circuit is determined. Therefore, by determining δ, the minimum [modulation strategy] can be achieved. It can immediately optimize current ripple, known as phase-shift based dual closed-loop control, and its control block diagram is as follows: Figure 4 As shown, the relevant transfer function expressions are shown in Table 2.

[0071] Table 2

[0072]

[0073] As can be seen from Table 1, under modes A5, B5, C2, and D2, It can be minimized. Therefore, the current ripple optimization controller is based on the duty cycle. d By obtaining the optimal phase shift angle δ between switches S1 and Q1 within a certain range, the drive signals for switches Q1-Q8 in the CLLLC resonant converter can be obtained. When controlling the DC / DC converter, prioritizing these modes can minimize current ripple, thereby reducing inductance L. b Reduce core losses and coil losses to improve inductance L b This improves working efficiency. On the other hand, the maximum inductor current is also reduced, which helps to reduce the size of the inductor.

[0074] To verify the effectiveness of the phase-shift-based dual-closed-loop control strategy in this embodiment, the converter parameters were set as follows based on a hardware-in-the-loop simulation platform: V in The range is 150-600V. v bus =300V v out =600V, C fly =100μH, L m =240μH, switching frequency f s =20kHz, C1=255μF, C2=255μF, n=1:2, L b =300μH, L r1 =48μH, C r1 =1.32μF, L r2 =192μH, C r2 =0.33μF, C bus =255μF, P=2kW.

[0075] like Figure 5The diagram shows the experimental waveforms for input voltage switching. When the input voltage switches from 400V to 300V, the voltage across the flying capacitor changes from 200V to 150V, stabilizing at half the input voltage. The output voltage remains stable at 600V without significant fluctuations. Figure 6 The waveform shown is from an experiment demonstrating load switching. The input voltage is 400V, and the load switches from 180Ω to 360Ω; the output voltage remains stable. Figure 7A The waveform shown is the experimental waveform without phase-shift control, as follows: Figure 7B The figure shows the experimental waveform using dual closed-loop phase-shift control, with an input voltage of 500V. Without phase-shift control, there is no phase shift angle between switching transistors S1 and Q1, and the inductor current... i Lb The current ripple is 13.3A. When phase-shift control is used, the given phase shift angle between switching transistors S1 and Q1 is (1- d )T s Inductor current i Lb The current ripple is 5.8A. This shows that the current ripple decreased from 13.3A to 5.8A, a reduction of 56.4%. The experimental waveforms above demonstrate that the phase-shifting dual-loop control in this embodiment optimizes the inductor current while ensuring stable output voltage regulation.

[0076] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A cascaded DC / DC converter with multiplexed components, characterized in that, include: Cascaded Buck-Boost converters and CLLLC resonant converters, along with closed-loop controllers, current ripple optimization controllers, and drivers; The Buck-Boost converter includes two bridge arms, and one of the bridge arms is multiplexed with the CLLLC resonant converter. The closed-loop controller is used to: calculate the duty cycle of the switching transistors in the unreused bridge arms of the Buck-Boost converter based on the output voltage and input voltage of the DC / DC converter. d ; The current ripple optimization controller is used to: adjust the inductor current ripple of the DC / DC converter based on the duty cycle. d The functional relationship between the phase shift angle δ and the inductor current ripple is determined by solving the phase shift angle δ, where the phase shift angle δ is the phase shift angle between the switch of the unreused bridge arm and the switch of the multiplexed bridge arm in the Buck-Boost converter. The driver is configured to: according to the duty cycle d The phase shift angle δ controls the on / off state of the switching transistors in the DC / DC converter; The Buck-Boost converter is characterized in that it is a six-switch Buck-Boost converter. The six-switch Buck-Boost converter includes: switches S1, S2, S3, S4, Q1, and Q2 with anti-parallel diodes, and a flying capacitor C. fly and inductor L b ; S1, S2, S3 and S4 are connected in series and serve as unreused bridge arms. Q1 and Q2 are connected in series and serve as reused bridge arms. S1 is connected to the positive terminal of the primary power supply, and S4 and Q2 are both connected to the negative terminal of the primary power supply. Flying capacitor C fly One end of the inductor is connected to the connection point of S1 and S2, and the other end is connected to the connection point of S3 and S4; Inductor L b One end is connected to the connection point of S2 and S3, and the other end is connected to the connection point of Q1 and Q2; The driver is used to control the on / off state of S1, S2, S3, S4, Q1, Q2, Q3 and Q4; The conduction time of S1 and S2 is determined by the duty cycle. d It is determined that the conduction time of Q1 lagging behind S1 is determined by the phase shift angle δ; Q1 and Q4 are synchronously turned on or off, Q2 and Q3 are synchronously turned on or off, and Q1 and Q2 are complementary in conduction; the driving signals of Q1, Q2, Q3 and Q4 are square wave signals with a frequency equal to the resonant frequency of the DC / DC converter and a duty cycle of 50%; 0 < d When ≤0.25, the inductor current ripple and duty cycle d The functional relationship between the phase shift angle δ and the phase shift angle δ is: 0.25 < d When ≤0.5, the inductor current ripple and duty cycle d The functional relationship between the phase shift angle δ and the phase shift angle δ is: 0.5 < d When ≤0.75, the inductor current ripple and duty cycle d The functional relationship between the phase shift angle δ and the phase shift angle δ is: 0.75 < d When ≤1, the inductor current ripple and duty cycle d The functional relationship between the phase shift angle δ and the phase shift angle δ is: in, This represents the per-unit value of the inductor current ripple.

2. The cascaded DC / DC converter with device multiplexing as described in claim 1, characterized in that, The CLLLC resonant converter includes: a transformer, a primary-side full-bridge LLC circuit connected to the primary side of the transformer, and a secondary-side full-bridge LC circuit connected to the secondary side of the transformer. The primary-side full-bridge LLC circuit and the six-switch Buck-Boost converter multiplexed bridge arm include a primary-side H-bridge circuit composed of switches Q1, Q2, Q3 and Q4.

3. The cascaded DC / DC converter with device multiplexing as described in claim 2, characterized in that, The Buck-Boost converter is a six-switch Buck-Boost converter, 0 < d When ≤0.5, the six-switch Buck-Boost converter operates in Buck mode; when 0.5 < d When ≤1, the six-switch Buck-Boost converter operates in Boost mode.

4. The cascaded DC / DC converter with device multiplexing as described in claim 1, characterized in that, Duty cycle d satisfy: in, The output voltage of the DC / DC converter. The input voltage of the DC / DC converter. This represents the transformer's turns ratio in a CLLLC resonant converter.

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