A DC-DC high voltage gain converter integrating switched capacitor and Y source network

Abstract

The present invention belongs to the technical field of DC-DC conversion equipment, and relates to a DC-DC high voltage gain converter integrating a switch capacitor and a Y source network. The high voltage gain is achieved by controlling the switch conduction duty cycle D to realize energy exchange between an input DC power supply and an output. The switch capacitor unit is obtained by deforming a traditional switch capacitor structure, and is integrated with a Y source network. The Y source unit is composed of a three-winding coupled inductor. By changing the turns ratio of the coupled winding, the output voltage is boosted to the DC power supply voltage. The overall result is reasonable in design, safe in use, simple in operation, and has great application potential. In addition, fewer devices are used, the design cost is low, the device loss is reduced, the working efficiency of the circuit is improved, and the ideal effect required by the design is achieved.

Description

Technical field:

[0001] The invention belongs to the technical field of DC-DC conversion equipment and relates to a DC-DC high voltage gain converter integrating a switch capacitor and a Y source network. Background technology:

[0002] At present, the increasing energy crisis and environmental pollution problems have promoted the rapid development of clean energy and green energy. Clean energy conversion technologies such as photovoltaic systems, fuel cells and tidal power generation have great development prospects. In practical applications, these power conversion circuit structures need to have higher efficiency and boost gain, but because the boost capacity of a single module in the energy conversion process is too low, a higher output voltage cannot be obtained. For example, solar power generation is currently a very widely used clean energy, but the output of a solar panel is very low. Many photovoltaic panels must be combined in series-parallel mode to achieve the voltage value actually required by the power market. However, this approach will increase the failure rate of the entire power supply system, make the whole machine too large and inefficient. Therefore, studying how to use an independent module to obtain a stable high output voltage has become an urgent problem to be solved. The Z-source inverter proposed in the document "FZ Peng, "Z-Source Inverter," IEEE Trans. Ind. Applicat., vol. 39, no. 2, pp. 504-510, Mar / Apr. 2003." realizes the boost and grid-connected functions at the same time, and has the advantages of simple circuit structure and high safety. Its application in DC / DC converters has also been proven, but the topological structure of the Z-source network itself reflects its limited boost capability. The premise of obtaining high boost is a high direct duty cycle. With the deepening of research, some topologies that introduce switching inductors, coupled inductors and other unit modules to achieve high voltage gain have emerged, but due to leakage inductance, there will be problems such as high circuit voltage stress and low boost efficiency. In addition, multi-stage circuits can be cascaded to obtain a higher voltage gain under a smaller direct duty cycle, but this increases the number of components in the circuit, increases the complexity of the circuit and the design cost, and reduces the efficiency of the converter. On this basis, the document "YPSiwakoti, PCLoh, F.Blaabjerg, SJAndreasen and GETown,"Y-Source Boost DC / DC Converter for Distributed Generation," in IEEE Transactions on Industrial Electronics, vol.62, no.2, pp.1059-1069, Feb.2015." proposed a Y-source network, which uses a three-winding coupled inductor, can flexibly change its gain, uses a small number of devices, and has high working efficiency. Therefore, finding a DC-DC conversion circuit that can obtain a higher voltage gain at a lower direct-pass duty cycle and has a simple structure and high working efficiency has become a research hotspot in this field. Summary of the invention:

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and to provide a high-gain DC-DC converter integrating a switched capacitor and a Y source network. Under the condition of a small duty cycle, a higher voltage gain is obtained, and its voltage gain adjustment has a large degree of freedom. In addition, fewer devices are used in the circuit structure, the working efficiency is high, and the failure rate is low. At the same time, the clamping structure can absorb the leakage inductance energy of the transformer and clamp the voltage spike generated on the switch tube S.

[0004] In order to achieve the above-mentioned purpose, the main structure of the high-gain DC-DC converter integrating the switching capacitor and the Y-source network of the present invention includes a DC power supply, an input energy storage inductor, a first energy storage capacitor, a first diode, a power switch tube, a second energy storage capacitor, a second diode, a first winding, a second winding, a third winding, an output capacitor and a load; one end of the input energy storage inductor is connected to the DC power supply, and the other end is respectively connected to the negative electrode of the second energy storage capacitor, the anode of the first diode and the power switch tube; the cathode of the first diode is connected to the positive electrode of the first energy storage capacitor, the negative electrode of the first energy storage capacitor and the power switch tube are grounded, and the first diode, the first energy storage capacitor and the power switch tube are grounded. The power switch tube together constitutes a clamping circuit for clamping the voltage spike generated on the power switch tube; the three mutually coupled windings, the first winding, the second winding, and the third winding, are connected in a Y type to form a Y source unit, the turns ratio of the second winding to the first winding is n1, the turns ratio of the third winding to the first winding is n2, the same-name ends of the first winding are respectively connected to the cathode of the first diode and the positive electrode of the first energy storage capacitor, and the opposite-name ends are respectively connected to the same-name ends of the second winding and the opposite-name ends of the third winding, the same-name end of the third winding is connected to the positive electrode of the second energy storage capacitor, the opposite-name end of the second winding is connected to the anode of the second diode, and the cathode of the second diode is respectively connected to the positive electrode of the output capacitor and the load.

[0005] The high-gain DC-DC converter of the present invention realizes energy exchange between input DC power supply and output by controlling the switch conduction duty cycle D, thereby achieving high voltage gain. The switch capacitor unit is obtained by deforming the traditional switch capacitor structure and is integrated with the Y source network; the Y source unit is composed of three-winding coupled inductors, and the output voltage is converted into the DC power supply voltage by changing the turns ratio of the coupled winding.

[0006] The power switch tube S of the present invention is turned on or off by using a unipolar SPWM control method, which is used to improve the working efficiency of the switch module and reduce the switching loss.

[0007] Compared with the existing DC-DC boost converter circuit topology, the present invention integrates a switch capacitor and a Y source network, and achieves the purpose of obtaining a high boost gain under a small duty cycle condition by adjusting the turns ratio of the coupled inductor winding. The designed connection method of the coupled inductor winding is utilized to reduce the voltage stress of the circuit, reduce electromagnetic interference, and increase the reliability of the circuit structure. The overall result is reasonable in design, safe in use, simple in operation, and has great application potential. In addition, fewer devices are used, the design cost is low, the device loss is reduced, the working efficiency of the circuit is improved, and the ideal effect required by the design is achieved. Description of the drawings:

[0008] Figure 1 It is a schematic diagram of the main structural principle of the present invention.

[0009] Figure 2 Schematic diagram of the working state (state 1) of the present invention when the power switch tube S is turned on and the first diode D1 and the second diode D2 are reversely cut off in the CCM mode.

[0010] Figure 3 It is a schematic diagram of the working state (state 2) of the present invention when the power switch tube S is turned on, the first diode D1 is turned on, and the second diode D2 is reversely cut off in the CCM mode.

[0011] Figure 4 It is a schematic diagram of the working state (state 3) of the present invention when the power switch tube S is turned off and the first diode D1 and the second diode D2 are turned on in the CCM mode.

[0012] Figure 5 It is a schematic diagram of the working state (state 4) of the present invention when the power switch tube S is turned off, the first diode D1 is reversely cut off, and the second diode D2 is turned on in the CCM mode. Specific implementation method:

[0013] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0014] Embodiment 1:

[0015] The main structure circuit diagram of the high-gain DC-DC converter with integrated switched capacitors and Y-source network in this embodiment is shown in FIG. Figure 1 As shown, including DC power supply V g , input energy storage inductor L1, first energy storage capacitor C1, first diode D1, power switch tube S, second energy storage capacitor C2, second diode D2, first winding N1, second winding N2, third winding N3, output capacitor C0 and load R1;, one end of input energy storage inductor L1 is connected to DC power supply V gThe first end of the first diode D1 is connected to the cathode of the second energy storage capacitor C2, the anode of the first diode D1 and the power switch tube S; the cathode of the first diode D1 is connected to the anode of the first energy storage capacitor C1, the cathode of the first energy storage capacitor C1 and the power switch tube S are grounded together, the first diode D1, the first energy storage capacitor C1 and the power switch tube S together constitute a clamping circuit for clamping the voltage spike generated on the power switch tube S; the three mutually coupled windings, the first winding N1, the second winding N2 and the third winding N3, are connected by a Y-type connection. The first winding N1 is connected to form a Y source unit, and the turns ratio between the windings is n1=N2:N1, n2=N3:N1. The like-name ends of the first winding N1 are respectively connected to the cathode of the first diode D1 and the positive electrode of the first energy storage capacitor C1, and the different-name ends are respectively connected to the like-name ends of the second winding N2 and the different-name ends of the third winding N3. The like-name end of the third winding N3 is connected to the positive electrode of the second energy storage capacitor C2, the different-name end of the second winding N2 is connected to the anode of the second diode D2, and the cathode of the second diode D2 is respectively connected to the positive electrode of the output capacitor C0 and the load R1.

[0016] The high-gain DC-DC converter described in this embodiment realizes energy exchange between the input DC power supply and the output by controlling the switch conduction duty cycle D, thereby achieving high voltage gain. The switch capacitor unit is a deformation of the traditional switch capacitor structure and is integrated with the Y source network; the Y source unit is composed of three winding coupled inductors, and the output voltage is converted into a boost voltage of the DC power supply voltage by changing the turns ratio of the coupled winding.

[0017] In this embodiment, the first diode D1 and the second diode D2 are fast recovery diodes. The fast recovery diodes have the characteristics of good switching characteristics and short reverse recovery time. The internal structure of the fast recovery diode is different from that of the ordinary PN junction diode. It belongs to a PIN junction diode, that is, a base region I is added between the P-type silicon material and the N-type silicon material to form a PIN silicon wafer. Because the base region is very thin and the reverse recovery charge is very small, the fast recovery diode is applied in the present invention to achieve the effects of short reverse recovery time, low forward voltage drop and high reverse withstand voltage value.

[0018] The power switch tube S described in this embodiment adopts an SPWM control method, and the SPWM control method includes a bipolar SPWM control method and a unipolar control method. Compared with the unipolar mode, the bipolar SPWM mode control circuit and the main circuit are relatively simple, but the high-order harmonic components in the output voltage of the unipolar SPWM mode are much smaller than those of the bipolar SPWM mode. Therefore, this embodiment adopts a unipolar SPWM control method to realize the conduction or cutoff of the switch module, which can improve the working efficiency of the switch module and reduce the switching loss.

[0019] Embodiment 2:

[0020] In this embodiment, based on the first embodiment, a magnetizing inductor L is connected in parallel to the first winding N1.m , series leakage inductance L k , in the case of continuous working mode, the high gain DC-DC converter has a total of four working states:

[0021] State 1( Figure 2 ): The power switch tube S is turned on, the first diode D1 and the second diode D2 are reversely cut off, and the current loop is as follows Figure 2 As shown, the DC power supply V g The energy on the power switch tube S is transferred to the input energy storage inductor L1, so the current i L1 Linear increase, V C1 Discharge through the power switch tube S and transfer energy to the excitation inductor L m , leakage inductance L k and the third winding N3, while the second energy storage capacitor C2 is charged. o It is large enough, so the voltage on the load R1 remains basically unchanged at this time.

[0022] State 2( Figure 3 ): At this time, the shutdown trigger pulse of the power switch tube S has arrived, but due to the influence of the junction capacitance at both ends of the power switch tube S, the power switch tube S will not be turned off immediately. The current at both ends of the power switch tube S drops rapidly and the voltage rises rapidly. When the anode voltage of the first diode D1 is higher than the cathode voltage, the first diode D1 is turned on and continues to be turned on. At this time, the current i L1 , magnetizing inductor current I m Basically remain unchanged, leakage inductance L k The energy on the capacitor C2 is transferred to the second energy storage capacitor C2, and this state ends when the current of the power switch tube S decreases to 0.

[0023] State 3( Figure 4 ): The power switch tube S is turned off, the first diode D1 and the second diode D2 are forward-conducted, and the input energy storage inductor L1 releases energy to the first energy storage capacitor C1 through the first diode D1. Therefore, the current i on the input energy storage inductor L1 is L1 Linearly decreases and is stored in the excitation inductance L m , leakage inductance L k The energy in the second winding N2, the third winding N3 and the second energy storage capacitor C2 is released to the output capacitor C o and load R l At the same time, since the leakage inductance energy is absorbed, the voltage stress of the switch tube is clamped at V C1 , when i D1 =0, the state ends.

[0024] State 4 ( Figure 5): The power switch tube S continues to be turned off, the first diode D1 is reversely cut off, and the second diode D2 continues to be forward-conducted. At this time, the DC power supply V g , input energy storage inductor L1, second energy storage capacitor C2 and third winding N3 are connected in series to output energy. On the one hand, leakage inductance L k Energy storage, excitation inductance L m The energy storage continues to release energy to charge the first energy storage capacitor C1; on the other hand, combined with the second winding N2, the output capacitor C o Charging and Loading R l Provide energy.

[0025] The working state diagram of this embodiment is as follows: Figure 2 to Figure 5 As shown in the figure, there are four working states in one working cycle. To simplify the analysis, the leakage inductance of the coupled inductor is ignored in the steady-state analysis. The transformer is an ideal transformer, and the turns ratio between the windings is n1=N2:N1, n2=N3:N1. At the same time, the loss of the power device is not considered. Only modes 1 and 3 under the CCM operating state are considered, because the time interval between modes 2 and 4 in one cycle is very short. In the first mode, the power switch tube S is turned on, and the input energy storage inductor L1 is connected through the DC power supply V g Energy storage, excitation inductance L m and the third winding N3 through V C1 -V C2 Energy storage, from Figure 2 The following equation can be obtained:

[0026]

[0027] In mode 3, the main power switch S is turned off, the input energy storage inductor L1 and the excitation inductor L m The voltage across the inductor and the magnetizing inductor can be expressed as:

[0028]

[0029] Using the voltage volt-second balance principle for the inductor and the excitation inductor, the gain of the proposed high-gain DC-DC converter with integrated switched capacitor and Y-source network in CCM is obtained:

[0030]

[0031] Embodiment 3:

[0032] In this embodiment, when the design requires the output voltage to be converted to more than 10 times the input voltage, according to the expression of the conventional boost circuit boost gain V o =V g / (1-D) is used to calculate. When the design requirement of 10 times boost gain is reached, the required duty cycle D must reach 0.9. It is well known that the switch tube of the circuit will be in a limit state at this time, which will easily affect the working efficiency of the entire circuit, increase the probability of device damage, and ultimately affect the boost conversion efficiency of the entire circuit. In this embodiment, according to the analysis of the circuit voltage relationship, the output and input voltage relationship of the high-gain DC-DC converter topology of the integrated switch capacitor and Y source network involved in the invention is:

[0033]

[0034] If the design requires the circuit structure to obtain a 10-fold boost gain, when the direct-through duty cycle is 0.4, the number of coupled winding turns only needs to satisfy n1=2, n2=0.76 to meet the output requirements. Therefore, when the design requires a very high boost multiple, the occurrence of extreme duty cycles is avoided, the switching loss of the device is reduced, the probability of device damage is reduced, and the safety and reliability of the converter topology are further improved, thereby improving the overall working efficiency of the circuit.

[0035] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A DC-DC high voltage gain converter integrating switched capacitor and Y source network, characterized in that The main structure includes a DC power supply, an input energy storage inductor, a first energy storage capacitor, a first diode, a power switch tube, a second energy storage capacitor, a second diode, a first winding, a second winding, a third winding, an output capacitor and a load; one end of the input energy storage inductor is connected to the DC power supply, and the other end is respectively connected to the negative electrode of the second energy storage capacitor, the anode of the first diode and the power switch tube; the cathode of the first diode is connected to the positive electrode of the first energy storage capacitor, the negative electrode of the first energy storage capacitor and the power switch tube are grounded, and the first diode, the first energy storage capacitor and the power switch tube together constitute a clamping circuit for clamping the voltage spike generated on the power switch tube; three mutually coupled windings, the first winding, the second winding and the third winding, are connected in a Y-type to form a Y source unit, the turns ratio of the second winding to the first winding is n1, and the turns ratio of the third winding to the first winding is n2, The same-name ends of the first winding are respectively connected to the cathode of the first diode and the positive electrode of the first energy storage capacitor, and the opposite-name ends are respectively connected to the same-name ends of the second winding and the opposite-name ends of the third winding, the same-name end of the third winding is connected to the positive electrode of the second energy storage capacitor, the opposite-name end of the second winding is connected to the anode of the second diode, and the cathode of the second diode is respectively connected to the positive electrode of the output capacitor and the load; the DC-DC high voltage gain converter realizes energy exchange between the input DC power supply and the output by controlling the switch conduction duty cycle D to complete the high voltage gain; the switch capacitor unit is a deformation of the traditional switch capacitor structure and is integrated with the Y source network. The Y source unit is composed of three winding coupled inductors. By changing the turns ratio of the coupled winding, the output voltage is boosted to the DC power supply voltage. The conduction or cutoff of the power switch tube S adopts a unipolar SPWM control method.

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