A Quasi-Z Source DC-DC Converter Based on Switched Capacitor Structure

Abstract

The present invention discloses a quasi-Z source DC-DC converter based on a switched capacitor structure, belonging to the field of power electronics technology. The converter comprises an n-phase switched inductor quasi-Z source structure, wherein the first-phase switched inductor quasi-Z source structure constitutes a first-stage switched inductor quasi-Z source unit, and the second to n-phase switched inductor quasi-Z source structures constitute a second-stage unit. The converter also comprises an input voltage source #imgabs0#, n-1 main switching tubes #imgabs1#, n-1 auxiliary switching tubes #imgabs2#, capacitors #imgabs3#, #imgabs4#, and #imgabs5#, and n-1 diodes #imgabs6#. The converter uses a quasi-Z source to replace the inductors in an interleaved parallel topology, where two inductors exist in each phase. The inductors in each phase are then replaced with a switched inductor topology to further improve the voltage gain. A switched inductor quasi-Z source structure is added to the first stage of the interleaved parallel structure so that its output voltage serves as the input voltage of the interleaved parallel structure, thereby significantly improving the voltage gain. When in an environment with high boost requirements, the number of phases can be expanded to achieve higher gain.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and in particular relates to a quasi-Z source DC-DC converter based on a switched capacitor structure. Background Art

[0002] DC-DC converters are primarily used in step-up and step-down systems with high power quality requirements. They convert DC power from one voltage level to another and are currently widely used in new energy vehicles, photovoltaic power generation, and other fields. Non-isolated DC-DC converters control the average conversion efficiency between input and output voltages by adjusting the on and off times of the switch. This is achieved through the use of pulse-width modulation, which adjusts the output voltage by varying the on and off times of the switch.

[0003] The quasi-Z source network is the core component of a quasi-Z source DC-DC converter, consisting of an inductor, capacitors, and switching devices. Unlike traditional DC-DC converters, the quasi-Z source network can achieve a wider range of input voltage conversion and has a strong boost capability. Its voltage gain is: .

[0004] An interleaved parallel DC-DC converter is a type of DC-DC converter used in high-power applications. It achieves higher power conversion efficiency and lower output voltage ripple by connecting multiple independent DC-DC converters in parallel.

[0005] However, interleaved parallel DC-DC converters have a significant problem: low voltage gain, making it difficult to achieve boost requirements at extreme duty cycles. Quasi-Z-source DC-DC converters offer good voltage gain, but suffer from a topology that cannot be expanded, leading to large errors at extreme duty cycles. Therefore, the topology proposed in this invention addresses these issues with both topologies. Summary of the Invention

[0006] In response to the problems existing in the existing interleaved parallel converters and quasi-Z-source converters, the present invention proposes a quasi-Z-source DC-DC converter based on a switched capacitor structure, which improves the voltage gain under the extreme positive duty cycle, and also enables the topology to be expanded to reduce the error under the extreme duty cycle, thereby solving the shortcomings of the existing technology.

[0007] A quasi-Z source DC-DC converter based on a switched capacitor structure includes an n-phase switched inductor quasi-Z source structure, wherein the first-phase switched inductor quasi-Z source structure constitutes a first-stage switched inductor quasi-Z source unit, and the second to n-phase switched inductor quasi-Z source structures constitute a second-stage switched inductor quasi-Z source unit, and further includes an input voltage source. , n-1 main switch tubes , n-1 auxiliary switch tubes ,capacitance 、 and and n-1 diodes ,in ;

[0008] The input terminal of the first switch inductor quasi-Z source structure is connected The positive terminal of the The positive electrode of the 2nd to nth switching inductor quasi-Z source structures are connected in parallel, and the output terminals of the 2nd switching inductor quasi-Z source structure to the n-1th switching inductor quasi-Z source structure are connected to arrive The drain, arrive The source and arrive The negative pole of the nth switch inductor quasi-Z source structure is connected to the output terminal The drain and The first end, arrive The drain and The second end of the connection The source, Drain connection The first end, The second end of the connection The source, The first end and The negative electrode, The second end of the connection and the negative electrode of the second switching inductor quasi-Z source structure to the input end of the n-1th switching inductor quasi-Z source structure.

[0009] Further, let , No. A switch inductor quasi-Z source structure includes capacitor 、 ,diode 、 、 、 、 、 、 and inductors 、 、 、 ;

[0010] No. In a switch inductor quasi-Z source structure, Positive connection The first end, The first end of the The negative electrode and The first end, The second end of the connection The negative electrode, The positive electrode and The first end, Positive connection The positive electrode and The second end of Negative connection The second end, The positive electrode and The first end, The second end of the connection The first end and The negative electrode, Positive connection The second end and The positive electrode, Negative connection The negative electrode and The second end.

[0011] Furthermore, the second switch inductor quasi-Z source structure is connected to the n-1th switch inductor quasi-Z source structure. The second end, The first end and Connect the negative pole of arrive The drain and arrive The source of

[0012] In the nth switch inductor quasi-Z source structure, The second end, The first end and The negative terminals are connected to The drain and The first end of

[0013] The positive electrode is connected to the first switch inductor in the quasi-Z source structure The positive electrode, The first end and The first end.

[0014] Furthermore, the inductor 、 、 、 The inductance value is the same as the capacitance 、 、 、 、 The capacitance value is the same.

[0015] Furthermore, the voltage gain ratio of the converter is:

[0016] ;(1)

[0017] in, is the duty cycle.

[0018] Furthermore, the switch tube and It is a MOSFET power switch tube and adopts a 360° / (n-1) alternating conduction control method.

[0019] Furthermore, it also includes a controller, respectively The control mode is unipolar PWM control.

[0020] Furthermore, the controller is a TMS320F28335DSP control chip.

[0021] Beneficial technical effects brought about by the present invention:

[0022] This invention uses a quasi-Z source to replace the inductors in the interleaved parallel topology, with two inductors per phase. This is then replaced with a switched inductor topology, further improving voltage gain. A switched inductor quasi-Z source is added to the preceding stage of the interleaved parallel structure, allowing its output voltage to serve as the input voltage for the interleaved parallel structure, significantly boosting voltage gain. In environments with high voltage boost requirements, the number of phases can be expanded to achieve even higher gain.

[0023] The present invention controls the main switches S1, S2 and the auxiliary switch tube S Q1 、S Q2 The alternating conduction makes the topology in the boost state. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a circuit diagram of a quasi-Z-source DC-DC converter based on a switched capacitor structure in the present invention.

[0025] Figure 2 The voltage and current waveforms of the two-stage DC-DC converter in the working range.

[0026] Figure 3 This is the equivalent circuit diagram of the two-stage DC-DC converter operating mode 1.

[0027] Figure 4 This is the equivalent circuit diagram of the two-stage DC-DC converter operating mode 2.

[0028] Figure 5 This is the equivalent circuit diagram of the two-stage DC-DC converter operating mode 3.

[0029] Figure 6 The figure shows the voltage gain comparison between the converter of the present invention and the traditional converter.

[0030] Figure 7 This is a simulation model of the converter of the present invention built in the PSIM platform.

[0031] Figure 8 This is the simulation waveform of the converter of the present invention in the PSIM platform. DETAILED DESCRIPTION

[0032] The specific implementation of the present invention will be further described below with reference to specific embodiments:

[0033] like Figure 1 As shown, a quasi-Z source DC-DC converter based on a switched capacitor structure includes n-phase switched inductor quasi-Z source structures, wherein the first-phase switched inductor quasi-Z source structure constitutes a first-stage switched inductor quasi-Z source unit, and the second to n-phase switched inductor quasi-Z source structures constitute a second-stage switched inductor quasi-Z source unit, and further includes an input voltage source , n-1 main switch tubes , n-1 auxiliary switch tubes ,capacitance 、 and and n-1 diodes ,in ;

[0034] The input terminal of the first switch inductor quasi-Z source structure is connected The positive terminal of the The positive electrode of the 2nd to nth switching inductor quasi-Z source structures are connected in parallel, and the output terminals of the 2nd switching inductor quasi-Z source structure to the n-1th switching inductor quasi-Z source structure are connected to arrive The drain, arrive The source and arrive The negative pole of the nth switch inductor quasi-Z source structure is connected to the output terminal The drain and The first end, arrive The drain and The second end of the connection The source, Drain connection The first end, The second end of the connection The source, The first end and The negative electrode, The second end of the connection and the negative electrode of the second switching inductor quasi-Z source structure to the input end of the n-1th switching inductor quasi-Z source structure.

[0035] make , No. A switch inductor quasi-Z source structure includes capacitor 、 ,diode 、 、 、 、 、 、 and inductors 、 、 、 ;

[0036] No. In a switch inductor quasi-Z source structure, Positive connection The first end, The first end of the The negative electrode and The first end, The second end of the connection The negative electrode, The positive electrode and The first end, Positive connection The positive electrode and The second end of Negative connection The second end, The positive electrode and The first end, The second end of the connection The first end and The negative electrode, Positive connection The second end and The positive electrode, Negative connection The negative electrode and The second end.

[0037] The second switch inductor quasi-Z source structure is connected to the n-1th switch inductor quasi-Z source structure. The second end, The first end and Connect the negative pole of arrive The drain and arrive The source of

[0038] In the nth switch inductor quasi-Z source structure, The second end, The first end and The negative terminals are connected to The drain and The first end of

[0039] The positive electrode is connected to the first switch inductor in the quasi-Z source structure The positive electrode, The first end and The first end.

[0040] inductance 、 、 、 The inductance value is the same as the capacitance 、 、 、 、 The capacitance value is the same;

[0041] The voltage gain ratio of the converter is:

[0042] ;(1)

[0043] in, is the duty cycle;

[0044] Switching tube and It is a MOSFET power switch tube and adopts 360° / (n-1) alternating conduction control mode;

[0045] The converter also includes a controller, The control mode is unipolar PWM control, and the controller is TMS320F28335DSP control chip.

[0046] Taking a two-stage interleaved parallel DC-DC converter based on a quasi-Z source structure, in which the second-stage switching inductor quasi-Z source unit includes a two-phase switching inductor quasi-Z source structure as an example;

[0047] The traditional interleaved parallel control method (360° / N) uses a 180° phase shift strategy for interleaved parallel high-gain DC-DC converters, that is, the phase difference between each two adjacent phases is 180°. Therefore, within one switching cycle, the circuit will have four operating ranges and three operating modes depending on the conduction status of the switch tube.

[0048] For working interval 1, if Figure 2 middle - Time period and Figure 3 As shown, the circuit is in working mode 1, the switch tube conduction, The auxiliary switch is in the off state. Shutdown, The diode in the first switch inductor quasi-Z source structure is in the on state. 、 、 、 are in the on state, and the diode 、 、 Inductor 、 、 、 is in a charged state, and the capacitor 、 The energy is released. The intermediate diode between the two stages In the on state, The first phase of the second-stage interleaved parallel structure and the first-stage switching inductor quasi-Z source structure are in the same conduction state, and the diode 、 、 、 are in the on state, and 、 、 It is in the off state, the inductor 、 、 、 is in a charged state, and the capacitor 、 The energy is released. The switching inductance of the second phase in the staggered parallel structure of the second stage and the diode in the quasi-Z source structure 、 、 、 are in the off state, and 、 、 It is in the on state, the inductor 、 、 、 is in a discharged state and charges the capacitor 、 Replenish energy. At this time, the interstage capacitor In the discharge state, the phase capacitance In discharge state, the load is supplied by the output capacitor Supply power to it.

[0049] For working intervals 2 and 4, if Figure 2 middle - 、 - Time period and Figure 4 As shown, the circuit is in working mode 2. In this mode, the main switch of the converter 、 are in the off state, the auxiliary switch tube Shutdown, The diode in the first stage is in the on state. 、 、 、 are in the off state, and 、 、 It is in the on state, the inductor 、 、 、 In the discharge state, the capacitor 、 Supplement energy. The intermediate diode between the two stages In the off state, The first and second phases in the staggered parallel structure of the second stage are in the same conduction state as the switching inductor quasi-Z source structure of the first stage. 、 、 、 、 、 、 、 are in the off state, and 、 、 、 、 、 It is in the on state, the inductor 、 、 、 、 、 、 、 are in the discharge state, 、 、 、 Replenish energy. At this time, the interstage capacitor In charging state, phase capacitance In discharge state, the load is supplied by the output capacitor Supply power to it.

[0050] For working interval 3, if Figure 2 middle - Time period and Figure 5 As shown, the circuit is in working mode 3, the main switch tube of the converter Shutdown, The auxiliary switch is in the on state. conduction, The diode in the first stage is in the off state. 、 、 、 are in the off state, and 、 、 It is in the on state, the inductor 、 、 、 In the discharge state, the capacitor 、 Supplement energy. The intermediate diode between the two stages 、 The first phase of the second-stage interleaved parallel structure and the first-stage switching inductor quasi-Z source structure are in the same conduction state, and the diode 、 、 、 are in the off state, and 、 、 It is in the on state, the inductor 、 、 、 In the discharge state, the capacitor 、 Replenish energy. The second-phase switching inductor in the second-stage interleaved parallel structure and the diode in the quasi-Z source structure 、 、 、 are in the on state, and 、 、 It is in the off state, the inductor 、 、 、 In the charging state, the capacitor 、 It is in the discharge state. At this time, the interstage capacitor In the discharge state, the phase capacitance In charging state, the load is supplied by the output capacitor Supply power to it.

[0051] In the case of a fixed phase shift (2π / n-1), the multiphase converter can be divided into different regions according to different duty cycle ranges. The regions are defined as follows:

[0052] ;(2)

[0053] Actual converter circuits often have various parasitic parameters. To reduce the difficulty of theoretical analysis, the following assumptions are made for the operating conditions of the proposed converter in current continuous mode (CCM):

[0054] Ignore the influence of the equivalent resistance of all power switches and other circuit components of the converter on the circuit;

[0055] The capacitance of all capacitors is large enough;

[0056] The inductor values ​​and capacitor values ​​in the topology are exactly the same;

[0057] The circuit operates in continuous conduction mode (CCM).

[0058] The traditional interleaved parallel control method (360° / N) uses a 180° phase shift strategy for DC-DC converters, meaning that the phase difference between adjacent phases is 180°. Therefore, within a switching cycle, the circuit has three operating modes depending on the conduction status of the switches. To more vividly illustrate the changes in inductor current and capacitor voltage, current and voltage waveforms using the traditional 180° interleaved parallel control method are shown.

[0059] Based on the above analysis of the working principle of the interleaved parallel topology, the working performance of the two-stage quasi-Z-source interleaved parallel DC / DC converter in three working ranges is analyzed below.

[0060] The duration of the first working mode is , according to Kirchhoff's voltage formula:

[0061] ;(3)

[0062] The duration of the second working mode is , according to Kirchhoff's voltage formula:

[0063] ;(4)

[0064] The duration of the third working mode is , according to Kirchhoff's voltage formula:

[0065] ;(5)

[0066] Combine equations (3), (4), and (5) to obtain 、 The voltage is:

[0067] ;(6)

[0068] capacitance is the output capacitor, and its voltage is consistent with the load voltage, so the voltage gain of the topology is:

[0069] ;(7)

[0070] The voltage gain in the above formula is the gain of the two-stage three-phase interleaved parallel DC-DC converter based on the quasi-Z source structure.

[0071] From this we can get the voltage gain when it is n phase:

[0072] ;(8)

[0073] The current is analyzed below:

[0074] The relationship between the output current and input current can be obtained from the relationship between the boost ratio, load and power supply as follows:

[0075] ;(9)

[0076] Among them, the duration of the first working mode is , according to Kirchhoff's current formula:

[0077] ;(10)

[0078] For working mode 2, its duration is , according to Kirchhoff's current formula:

[0079] ;(11)

[0080] For working mode 3, its duration is , according to Kirchhoff's current formula:

[0081] ;(12)

[0082] From formulas (10), (11), and (12), we can obtain:

[0083] (13).

[0084] Figure 6 Comparing the voltage gain of the present invention with that of other inventions, it can be seen that due to the use of a switched inductor quasi-Z-source structure, the present invention requires a duty cycle range of 0 to 1 / 3 in pass-through mode, thereby ensuring that the converter can achieve a higher voltage gain at a low duty cycle. The duty cycle of the converter proposed in invention CN116707306 A, on the other hand, ranges from 0 to 1. Therefore, in situations with high gain requirements, its duty cycle is close to 1. A high duty cycle means that the signal is at a high level most of the time, which causes the system to be continuously in an operating or conducting state, potentially leading to a significant increase in power consumption. Especially in high-frequency applications, switching losses and conduction losses can increase significantly, reducing overall efficiency. Figure 7 This is a simulation model built on the PSIM simulation platform for the present invention. Figure 8 From the simulation results of the simulation model built for the present invention, it can be seen that the relationship between the input voltage and the output voltage is exactly the same as the theoretical result of formula (6).

[0085] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the scope of protection of the present invention.

Claims

1. A quasi-Z source DC-DC converter based on a switched capacitor structure, characterized in that: The invention comprises an n-phase switching inductor quasi-Z source structure, wherein the first-phase switching inductor quasi-Z source structure constitutes a first-stage switching inductor quasi-Z source unit, and the second to n-phase switching inductor quasi-Z source structures constitute a second-stage switching inductor quasi-Z source unit, and further comprises an input voltage source. , n-1 main switch tubes , n-1 auxiliary switch tubes ,capacitance 、 and and n-1 diodes ,in ; The input terminal of the first switch inductor quasi-Z source structure is connected The positive terminal of the The positive electrode of the 2nd to nth switching inductor quasi-Z source structures are connected in parallel, and the output terminals of the 2nd switching inductor quasi-Z source structure to the n-1th switching inductor quasi-Z source structure are connected to arrive The drain, arrive The source and arrive The negative pole of the nth switch inductor quasi-Z source structure is connected to the output terminal The drain and The first end, arrive The drain and The second end of the connection The source, Drain connection The first end, The second end of the connection The source, The first end and The negative electrode, The second end of the connection and the negative electrode of the second switching inductor quasi-Z source structure to the input end of the n-1th switching inductor quasi-Z source structure.

2. The quasi-Z source DC-DC converter based on a switched capacitor structure according to claim 1, characterized in that: make , No. A switch inductor quasi-Z source structure includes capacitor 、 ,diode 、 、 、 、 、 、 and inductors 、 、 、 ; No. In a switch inductor quasi-Z source structure, Positive connection The first end, The first end of the The negative electrode and The first end, The second end of the connection The negative electrode, The positive electrode and The first end, Positive connection The positive electrode and The second end of Negative connection The second end, The positive electrode and The first end, The second end of the connection The first end and The negative electrode, Positive connection The second end and The positive electrode, Negative connection The negative electrode and The second end.

3. The quasi-Z source DC-DC converter based on a switched capacitor structure according to claim 2, characterized in that: The second switch inductor quasi-Z source structure is connected to the n-1th switch inductor quasi-Z source structure. The second end, The first end and Connect the negative pole of arrive The drain and arrive The source of In the nth switch inductor quasi-Z source structure, The second end, The first end and The negative terminals are connected to The drain and The first end of The positive electrode is connected to the first switch inductor in the quasi-Z source structure The positive electrode, The first end and The first end.

4. The quasi-Z source DC-DC converter based on a switched capacitor structure according to claim 3, characterized in that: The inductor 、 、 、 The inductance value is the same as the capacitance 、 、 、 、 The capacitance value is the same.

5. The quasi-Z source DC-DC converter based on a switched capacitor structure according to claim 4, characterized in that: The voltage gain ratio of the converter is: ；(1) in, is the duty cycle.

6. The quasi-Z source DC-DC converter based on a switched capacitor structure according to claim 5, characterized in that: The switch tube and It is a MOSFET power switch tube and adopts a 360° / (n-1) alternating conduction control method.

7. The quasi-Z source DC-DC converter based on a switched capacitor structure according to claim 6, characterized in that: Also includes a controller, respectively The control mode is unipolar PWM control.

8. The quasi-Z source DC-DC converter based on a switched capacitor structure according to claim 7, characterized in that: The controller is TMS320F28335DSP control chip.

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