A high step-up ratio dc / dc converter and a control method thereof
Patent Information
- Application Number
- CN202210860164.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-07-21
- Publication Date
- 2026-10-20
- Estimated Expiration
- 2042-07-21
AI Technical Summary
[0009]鉴于上述的分析，本发明实施例旨在提供一种高升压比DC/DC变换器及其控制方法，用以解决现有开关电容型高升压比变换器要实现很高升压比，其结构也比较复杂，有较多开关管会带来控制上的复杂以及更大的开关损耗的问题
[0038]1、通过耦合电感器降低输入电流波纹，从而在不增加额外输入滤波器条件下，保证输入端脉动电流不对电池的工作性能和工作寿命造成恶劣影响。通过耦合电感器的副边绕组与所述开关电容单元集成，能够防止开关管在关断期间出现高压尖峰，从而提升变换器的安全性和可靠性。
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Figure CN117477942B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of switching power supply technology, and in particular to a high boost ratio DC / DC converter and its control method. Background Technology
[0002] In fields such as new energy, lasers, X-rays, and radar, the demand for high-boost DC / DC converters is growing. Their input voltage is typically low for devices such as photovoltaic cells and fuel cells. When connected to a microgrid, a significant voltage boost is usually required to meet the needs of downstream devices.
[0003] When designing this high-boost DC / DC converter, reducing the converter's input current ripple is crucial. If the converter input is a photovoltaic cell, high current ripple will lead to poor maximum power point tracking performance of the photovoltaic cell, thereby reducing the efficiency of the photovoltaic system. If the converter input is a fuel cell, current ripple will accelerate battery degradation. Adding input filtering components can effectively suppress the pulsed input current generated by the converter; however, this will significantly increase the system size and cost.
[0004] Because parasitic losses in traditional boost converters at high duty cycles reduce output voltage and efficiency, and the switching transistors and diodes must withstand extremely high voltage stress, increasing component usage risk and cost, they are generally unsuitable for high boost ratio applications. Therefore, researchers typically employ cascaded converters or quasi-resonant converters to provide high voltage gain at lower duty cycles. However, their control is complex, and the second stage of a cascaded converter experiences high voltage stress, while a quasi-resonant converter suffers from high current stress. Consequently, both result in low power density and efficiency.
[0005] High voltage gain can also be achieved using switched-capacitor (SC) units, which reduces voltage stress on the switching transistors and diodes, thus improving system safety. However, a large number of SC units need to be connected in series to achieve high voltage gain, which increases the system cost and size. More importantly, due to the inherent characteristics of the basic circuit structure of SC converters, there is a large ripple current at the input, and since SC converters typically use only one inductor core, this ripple current is further increased. Therefore, these converters are not suitable for applications where the input is a photovoltaic cell or fuel cell.
[0006] There is a cascaded high boost ratio converter, such as Figure 1As shown, the first stage experiences relatively low voltage stress, allowing it to operate at very high switching frequencies, thus increasing power density. The second stage operates at a relatively low switching frequency, thereby reducing losses. However, the cascaded system requires two sets of power devices, magnetic cores, and control circuits, making its implementation complex and expensive. Furthermore, the power devices in the second stage face extremely high voltage stress, increasing the risk to the system's safe operation.
[0007] There is a switched capacitor type high boost ratio converter, such as Figure 2 As shown, each switched capacitor unit consists of a capacitor, a diode, and a switching transistor, as follows: Figure 2 As shown in the dashed box, theoretically, an infinite boost ratio can be achieved by increasing the number of switched capacitor units. However, in reality, the boost effect decreases significantly when the number of switched capacitor units exceeds a certain value. To achieve a very high boost ratio, this type of converter has a relatively complex structure with many switching transistors, which undoubtedly leads to control complexity and greater switching losses.
[0008] In response to this situation, the development of a high-efficiency boost converter with low input current ripple, low component count, low cost, and high efficiency has become increasingly urgent. Compared with other similar converters, the improved converter should be able to reduce input current ripple, thereby reducing the size of the input filter or even eliminating the need for a filter altogether, thus maximizing the power density of the entire system. Summary of the Invention
[0009] Based on the above analysis, the present invention aims to provide a high boost ratio DC / DC converter and its control method to solve the problems of existing switched capacitor type high boost ratio converters having a relatively complex structure and a large number of switching transistors, which lead to control complexity and greater switching losses in order to achieve a very high boost ratio.
[0010] On one hand, embodiments of the present invention provide a high boost ratio DC / DC converter, comprising: a switching transistor, a coupling inductor, a switched capacitor unit, and a series clamping unit, wherein the switching transistor is used to switch the charging and discharging states of the energy storage element in the DC / DC converter according to the on and off states; the primary winding of the coupling inductor serves as the input inductor of the high boost ratio DC / DC converter, and its secondary winding is integrated with the switched capacitor unit to prevent high voltage spikes from occurring during the off period of the switching transistor; and the series clamping unit is connected between the source and drain of the switching transistor, wherein when the switching transistor is off, it absorbs energy from the primary leakage inductance of the coupling inductor, and when the switching transistor is on, it outputs the energy to the switched capacitor unit.
[0011] The beneficial effects of the above technical solution are as follows: By reducing input current ripple through the coupling inductor, the input pulsating current is prevented from adversely affecting the battery's performance and lifespan without the need for an additional input filter. Furthermore, by integrating the secondary winding of the coupling inductor with the switched capacitor unit, high-voltage spikes during the turn-off period of the switching transistor can be prevented, thereby improving the safety and reliability of the converter.
[0012] Based on further improvements to the above-mentioned device, the coupling inductor further includes a magnetizing inductor and a primary leakage inductance located on the primary side, wherein the magnetizing inductor is connected in parallel across the two ends of the primary winding to reduce input current ripple; the primary leakage inductance is connected in series between the positive voltage terminal of the input power supply and the opposite terminal of the primary winding to suppress input current pulsation; and the secondary winding is connected between the series clamping unit and the switched capacitor unit.
[0013] Based on a further improvement of the above device, the drain of the switching transistor is connected to the same terminal of the primary winding, and the source of the switching transistor is connected to the negative voltage terminal of the input power supply.
[0014] Based on a further improvement of the above device, the series clamping unit includes a first diode, a third capacitor, and a fourth capacitor, wherein the anode of the first diode is connected to the same-name terminal of the primary winding and the drain of the switching transistor; the cathode of the first diode is connected to the first plate terminal of the third capacitor; the second plate terminal of the third capacitor is connected to the first plate terminal of the fourth capacitor and the same-name terminal of the secondary winding; and the second plate terminal of the fourth capacitor is connected to the source of the switching transistor.
[0015] Based on a further improvement of the above device, the switched capacitor unit includes: a second diode, a third diode, a fourth diode, a first capacitor, and a second capacitor, wherein the anode of the second diode is connected to the cathode of the first diode; the cathode of the second diode is connected to the anode of the third diode at a first node; the cathode of the third diode is connected to the anode of the fourth diode and the opposite-named terminal wound on the secondary side at a second node; the cathode of the fourth diode is connected to the first plate terminal of the second capacitor; the second plate terminal of the second capacitor is connected to the first plate terminal of the first capacitor and the first node; and the second plate terminal of the first capacitor is connected to the drain of the switching transistor.
[0016] Based on further improvements to the above-mentioned device, the high boost ratio DC / DC converter also includes a rectifier diode and an output capacitor and a load resistor connected in parallel, wherein the anode of the rectifier diode is connected to the first plate of the second capacitor and the cathode of the fourth diode; the cathode of the rectifier diode is connected to the first plate of the output capacitor; and the second plate of the output capacitor is connected to the source of the switching transistor.
[0017] On the other hand, embodiments of the present invention provide a control method for the high boost ratio DC / DC converter described in the above embodiments, comprising: when the switch is turned on, charging the primary leakage inductance and magnetizing inductance of the coupling inductor through the input voltage, and charging the third capacitor in the series clamping unit and the first and second capacitors in the switched capacitor unit through the secondary winding of the coupling inductor and the fourth capacitor in the series clamping unit, and supplying power to the load resistor through the output capacitor; when the switch is turned off, the first capacitor, the second capacitor and the primary side of the coupling inductor discharge to supply power to the load resistor, and increasing the output voltage value with a high boost ratio through the pump-up voltage on the first capacitor and the second capacitor, the discharge effect of the coupling inductor and the effect of the input voltage.
[0018] Based on a further improvement of the above method, the boost ratio of the DC / DC converter is determined by the following formula:
[0019]
[0020] Where D is the duty cycle of the switching transistor, n is the turns ratio of the coupling inductor, and n = N p / N s N p N is the number of turns of the primary winding. s V is the number of turns of the secondary winding. in V is the input voltage. O This is the output voltage.
[0021] Based on a further improvement of the above method, before the switching transistor is turned on, the magnetizing inductance and primary leakage inductance of the coupling inductor are determined, and the capacitance values of the output capacitor, the first capacitor, the second capacitor, the third capacitor, and the fourth capacitor are determined. The magnetizing inductance L of the coupling inductor is determined using the following formula. m :
[0022]
[0023] Among them, I O(min) The minimum load current is given by V, where fsw is the operating frequency of the DC / DC converter.in Where is the input voltage, D is the duty cycle of the switching transistor, and k is the coupling coefficient of the coupling inductor, with a value of 1.
[0024]
[0025] The primary leakage inductance L of the coupled inductor is determined by the following formula. lk :
[0026]
[0027] Where, ΔI in The input current ripple value allowed by the DC / DC converter, the input current ripple value ΔI in The smaller the value, the lower the original leakage inductance L. lk The larger the value, and the more the original leakage inductance L is. lk The larger the value, the better the effect of suppressing the pulsation of the input current.
[0028] Based on a further improvement of the above method, the capacitance value C of the output capacitor is determined by the following formula. O :
[0029]
[0030] The capacitance values of the first capacitor, the second capacitor, the third capacitor, and the fourth capacitor are determined using the following formula:
[0031]
[0032]
[0033]
[0034]
[0035]
[0036] Among them, I out(max) ΔV represents the maximum output current of the DC / DC converter. O P is the maximum allowable output voltage ripple of the DC / DC converter, ESR is the equivalent series resistance of the output capacitor, and P is the maximum allowable output voltage ripple of the DC / DC converter. out(max) R represents the maximum output power of the DC / DC converter. L The resistance value of the load resistor is given.
[0037] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:
[0038] 1. By using a coupling inductor to reduce input current ripple, the input pulsating current is prevented from adversely affecting battery performance and lifespan without the need for an additional input filter. Integrating the secondary winding of the coupling inductor with the switched capacitor unit prevents high-voltage spikes during switch-off, thereby improving the converter's safety and reliability.
[0039] 2. The presence of the series clamping unit allows the energy on the primary leakage inductance of the coupled inductor to be absorbed by the fourth capacitor of the unit when the switch is turned off, and this energy is output to the switching capacitor unit during the turn-on phase of the switch, thereby realizing the effective utilization of energy and thus improving the working efficiency of the converter.
[0040] 3. The presence of primary leakage inductance of the coupling inductor can reduce the reverse recovery loss of the diode and ensure that the diode achieves zero-current turn-on and turn-off. Therefore, the converter has the characteristics of high operating efficiency.
[0041] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description
[0042] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.
[0043] Figure 1 The circuit diagram is for an existing cascaded high boost ratio DC / DC converter;
[0044] Figure 2 The circuit diagram is for an existing switched-capacitor type high boost ratio DC / DC converter;
[0045] Figure 3 This is a circuit diagram of a high boost ratio DC / DC converter according to an embodiment of the present invention;
[0046] Figure 4 This describes the converter's operating mode when the switching transistor of the high boost ratio DC / DC converter is turned on, according to an embodiment of the present invention.
[0047] Figure 5 This describes the converter's operating mode when the switching transistor of the high boost ratio DC / DC converter is turned off, according to an embodiment of the present invention.
[0048] Figure 6 This is a flowchart of a control method for a high boost ratio DC / DC converter according to an embodiment of the present invention. Detailed Implementation
[0049] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.
[0050] A specific embodiment of the present invention discloses a high boost ratio DC / DC converter, such as... Figure 3 As shown, the high boost ratio DC / DC converter includes: a switching transistor S1, a coupling inductor 302, a switched capacitor unit 304, and a series clamping unit 306. The switching transistor S1 is used to switch the charging and discharging states of the energy storage element in the DC / DC converter according to the on and off states. The primary winding of the coupling inductor 302 serves as the input inductor of the high boost ratio DC / DC converter, and its secondary winding is integrated with the switched capacitor unit 304 to prevent high-voltage spikes during the switching transistor's off period. The series clamping unit 306 is connected between the source and drain of the switching transistor, wherein when the switching transistor is off, it absorbs energy from the primary leakage inductance of the coupling inductor, and when the switching transistor is on, it outputs energy to the switched capacitor unit 304.
[0051] Compared with existing technologies, the high boost ratio DC / DC converter provided in this embodiment reduces input current ripple through a coupling inductor, thereby ensuring that the input pulsating current does not adversely affect the battery's performance and lifespan without adding an additional input filter. By integrating the secondary winding of the coupling inductor with the switched capacitor unit, high-voltage spikes during switch-off can be prevented, thus improving the converter's safety and reliability.
[0052] The following text will refer to Figures 3 to 5 A high boost ratio DC / DC converter according to embodiments of the present invention will be described in detail. (See reference...) Figure 3 The high boost ratio DC / DC converter includes: a switching transistor S1, a coupling inductor 302, a switched capacitor unit 304, a series clamping unit 306, and a rectifier diode D. O Output capacitor C O and load resistor R L .
[0053] Switch S1 is used to switch the charging and discharging states of the energy storage element in the DC / DC converter according to the on and off states. For example, switch S1 is a metal-oxide-semiconductor field-effect transistor (MOSFET). Specifically, the drain of switch S1 is connected to the same terminal of the primary winding, and the source of switch S1 is connected to the input power supply V. in The negative voltage terminal.
[0054] The coupling inductor 302 has its primary winding used as the input inductor of a high boost ratio DC / DC converter, and its secondary winding integrated with the switched capacitor unit 304 to prevent high voltage spikes during the turn-off period of the switching transistor. The coupling inductor 302 also includes a magnetizing inductor L located on the primary side. m and the original edge leakage L lk Among them, the magnetizing inductance L m It is connected in parallel across the two ends of the primary winding to reduce input current ripple; primary leakage inductance L lk A secondary winding is connected in series between the positive voltage terminal of the input power supply and the opposite terminal of the primary winding to suppress input current pulsation; and a secondary winding is connected between the series clamping unit 306 and the switched capacitor unit 304.
[0055] The switched capacitor unit 304 includes: a second diode D2, a third diode D3, a fourth diode D4, a first capacitor C1, and a second capacitor C2. The anode of the second diode D2 is connected to the cathode of the first diode D1; the cathode of the second diode D2 is connected to the anode of the third diode D3 at a first node; the cathode of the third diode D3 is connected to the anode of the fourth diode D4 and the opposite-name terminal wound on the secondary side at a second node; the cathode of the fourth diode D4 is connected to the first plate terminal of the second capacitor C2; the second plate terminal of the second capacitor C2 is connected to the first plate terminal of the first capacitor C1 and the first node; and the second plate terminal of the first capacitor C1 is connected to the drain of the switching transistor S1.
[0056] A series clamping unit 306 is connected between the source and drain of the switching transistor S1. When the switching transistor S1 is off, it absorbs energy from the primary leakage inductance of the coupling inductor 302, and when the switching transistor S1 is on, it outputs energy to the switching capacitor unit 304. Specifically, the series clamping unit 306 includes a first diode D1, a third capacitor C3, and a fourth capacitor C4. The anode of the first diode D1 is connected to the same-name terminal of the primary winding and the drain of the switching transistor; the cathode of the first diode D1 is connected to the first plate terminal of the third capacitor C3; the second plate terminal of the third capacitor C3 is connected to the first plate terminal of the fourth capacitor C4 and the same-name terminal of the secondary winding; and the second plate terminal of the fourth capacitor C4 is connected to the source of the switching transistor S1.
[0057] Rectifier diode D O The anode of the rectifier diode is connected to the first plate of the second capacitor C2 and the cathode of the fourth diode D4; the rectifier diode D... O The cathode is connected to the output capacitor C. O The first plate terminal; and the output capacitor C O The second plate is connected to the source of the switching transistor. Load resistor R L With output capacitor C O Parallel connection.
[0058] Another specific embodiment of the present invention discloses a control method for a high boost ratio DC / DC converter, referring to... Figure 6 The control method for a high boost ratio DC / DC converter includes: in step S602, referring to Figure 4 When the switching transistor S1 is turned on, the input voltage V... in The primary leakage inductance L of the coupled inductor lk And excitation inductance L m Charging is performed, and the third capacitor C3 in the series clamping unit and the first capacitor C1 and the second capacitor C2 in the switched capacitor unit are charged together through the secondary winding of the coupling inductor and the fourth capacitor C4 in the series clamping unit, and the output capacitor C is charged. O To the load resistor R L Power supply; in step S604, refer to Figure 5 When the switch S1 is turned off, the first capacitor C1, the second capacitor C2 and the primary side of the coupling inductor discharge to supply power to the load resistor C1. Through the pump-up voltage on the first capacitor C1 and the second capacitor C2, the discharge effect of the coupling inductor and the effect of the input voltage, the output voltage value is increased with a high boost ratio.
[0059] The boost ratio of a DC / DC converter is determined using the following formula:
[0060]
[0061] Where D is the duty cycle of the switching transistor, and n is the turns ratio of the coupling inductor, n = N p / N s N p N is the number of turns in the primary winding. s V is the number of turns in the secondary winding. in V is the input voltage. O This is the output voltage.
[0062] Before switching transistor S1 is turned on, determine the magnetizing inductance and primary leakage inductance of the coupling inductor, and determine the capacitance values of the output capacitor, the first capacitor, the second capacitor, the third capacitor, and the fourth capacitor. The magnetizing inductance L of the coupling inductor is determined using the following formula. m :
[0063]
[0064] Among them, I O(min) f is the minimum value of the load current. sw V is the operating frequency of the DC / DC converter. in Where is the input voltage, D is the duty cycle of the switching transistor, and k is the coupling coefficient of the coupling inductor, with a value of 1.
[0065]
[0066] The primary leakage inductance L of the coupling inductor is determined by the following formula. lk :
[0067]
[0068] Where, ΔI in The allowable input current ripple value for the DC / DC converter, ΔI. in The smaller the value, the lower the leakage inductance L. lk The larger it is, and the more the original leakage inductance L is... lk The larger the value, the better the effect of suppressing input current ripple.
[0069] The capacitance value C of the output capacitor is determined by the following formula. o :
[0070]
[0071] The capacitance values of the first capacitor, second capacitor, third capacitor, and fourth capacitor are determined using the following formula:
[0072]
[0073]
[0074]
[0075]
[0076]
[0077] Among them, I out(max) ΔV represents the maximum output current of the DC / DC converter. O P is the maximum allowable output voltage ripple of the DC / DC converter, ESR is the equivalent series resistance of the output capacitor, and P is the maximum allowable output voltage ripple of the DC / DC converter. out(max) R is the maximum output power of the DC / DC converter. L This is the resistance value of the load resistor.
[0078] In the following text, refer to Figures 3 to 5 This document provides a detailed description of a high boost ratio DC / DC converter according to embodiments of the present invention, using specific examples. The high boost ratio DC / DC converter according to embodiments of the present invention is a CISC high boost ratio converter with low input current ripple.
[0079] High boost ratio DC / DC converter according to embodiments of the present invention, such as Figure 3 As shown, where V in The input voltage is R, and the input source is a photovoltaic cell or a fuel cell. L The output load is a DC microgrid or electric vehicle battery. This converter consists of a coupled inductor L. in Switch S1, series clamping unit, SC unit, rectifier diode D O Output capacitor C O Composition, in which the coupling inductor L in The magnetizing inductance is L m The original leakage inductance is L. lk The primary winding of the coupled inductor serves as the input inductor in the boost circuit structure, while the secondary winding of the coupled inductor is integrated with the SC unit to prevent high voltage spikes from occurring during the turn-off period of the switching transistor.
[0080] When switch S1 is turned on, the circuit's operating mode is as follows: Figure 4 As shown, the input voltage V in For the coupled inductor L in Leakage inductance L on the original side lk And excitation inductance L m Charging is performed; N on the secondary side of the coupled inductor s The winding and capacitor C4 together charge capacitors C1, C2, and C3; at this time, the load R L The required energy is supplied by the output capacitor C. O Provides and ensures stable output voltage.
[0081] When switch S1 is turned off, the circuit's operating mode is as follows: Figure 5 As shown, C1 and C2 release their energy, along with the energy on the primary side of the coupled inductor, to the load. Through the pump-up voltage on C1 and C2, the discharge effect of the coupled inductor, and the effect of the input voltage, the output voltage can be greatly increased, thereby achieving the goal of a high boost ratio. At the same time, during this turn-off period, the energy stored in the leakage inductance is transferred to C4 through D1.
[0082] In this converter, the input current is equal to the primary current of the coupling inductor. Therefore, by increasing the magnetizing inductance L of the coupling inductor... m This effectively reduces input current ripple. Furthermore, due to the leakage inductance of the primary winding of the coupled inductor, input current pulsation is further suppressed. Therefore, this CISC converter exhibits low input current ripple. In addition, the secondary winding N of the coupled inductor... s When integrated with the SC unit, it can prevent high voltage spikes from occurring during the turn-off period of the switching transistor, thereby improving the safety and reliability of the system.
[0083] The presence of the series clamping unit can reduce the leakage inductance L on the primary side of the coupled inductor. lk The energy in the converter is absorbed by C4 of this unit when S1 is turned off, and this energy is output to the SC unit during the S1 turn-on phase, thus achieving efficient energy utilization and improving the converter's operating efficiency. Furthermore, the leakage inductance L... lk The presence of this feature reduces the reverse recovery loss of the diode and ensures that the diode achieves zero-current turn-on and turn-off, thus giving the CISC converter a high operating efficiency.
[0084] Step 1: Calculate the boost ratio M of the converter.
[0085] Based on the working principle of this converter and according to relevant electromagnetic principles, the boost ratio of the converter can be derived as follows:
[0086]
[0087] Where D is the duty cycle of switch S1, and n is the coupling inductance L. in The turns ratio, n = N p / N s N p N represents the number of turns in the primary winding. s This represents the number of turns in the secondary winding.
[0088] Step 2: Select the coupling inductor L in Turns ratio n
[0089] Photovoltaic cells or fuel cells are used as inputs, with a typical input voltage V. inThe output voltage is 36–50V, and the output load is a DC microgrid or an electric vehicle battery. The typical output voltage is V. O The voltage is 400V, so the boost ratio M needs to be 8 to 11. The duty cycle D of the switching transistor S1 ranges from 0.2 to 0.8. Generally, when the boost ratio M is at its minimum, the corresponding duty cycle D of the switching transistor S1 is 0.5, from which the turns ratio of the coupling inductor can be calculated to be 1. Substituting n = 1 into the above equation (1), we can calculate that when the boost ratio M = 8 to 11, D = 0.5 to 0.64.
[0090] That is, when the coupling inductor turns ratio n=1 is selected, the duty cycle of the control switch S1 can be varied in the range of 0.5 to 0.64 to achieve a boost conversion of 8 to 11 times.
[0091] Step 3: Calculate the magnetizing inductance L of the coupled inductor. m
[0092] CISC converters can be divided into two operating modes, CCM (Continuous Mode) and DCM (Discontinuous Mode), depending on whether the coupled inductor current is discontinuous. In DCM mode, the input current ripple is very large, which will lead to reduced system efficiency, deterioration of battery MPPT performance, and higher requirements for input filtering. Therefore, it is necessary to avoid the system from entering DCM mode, that is, to ensure that the CISC converter operates in CCM mode, which is beneficial to reduce input current ripple.
[0093] Through derivation, it is found that, to ensure the converter operates in CCM mode, the magnetizing inductance L of the coupling inductor... m The following formula must be satisfied:
[0094]
[0095] Where I O(min) f is the minimum load current (determined according to user requirements). sw I is the operating frequency of the converter. O(min) and f sw All are user-defined. k is the coupling coefficient of the coupled inductor, expressed as shown in (3). In calculating L... m At that time, leakage inductance L can be ignored. lk The influence of k=1, i.e., calculating L m That's all.
[0096]
[0097] Step 4: Calculate the primary leakage inductance L of the coupled inductor. lk
[0098] Primary leakage inductance L of the coupled inductor lk The presence of L can effectively suppress the ripple of the input current, therefore, L needs to be designed reasonably. lkThe parameter value of L can be derived based on relevant electromagnetic principles. lk The formula for calculation is:
[0099]
[0100] Where ΔI in The allowable input current ripple value for the system is given by formula (4), ΔI in The smaller L lk The larger, i.e. L lk The larger the value, the better the effect of suppressing input current ripple. ΔI in The user determines L based on actual usage needs, and L is calculated by substituting it into equation (4). lk .
[0101] Step 5: Selection of Semiconductor Power Devices
[0102] In this converter, the semiconductor power devices include switch S1 and switches Do and D1 to D4. When selecting switch S1, the voltage stress needs to be considered. According to the analysis, the voltage stress of S1 is Vo / (3+n). In actual selection, the rated voltage of the selected switch should be 1.5 to 2 times this value.
[0103] When selecting diodes, it is necessary to consider both the voltage stress and current conditions of the diodes. Table 1 summarizes the voltage and current conditions of all diode devices in this converter. When selecting diodes, it should be ensured that the rated current and rated voltage of the diodes are at least 1.5 to 2 times the results in the table.
[0104] The d2 parameter in the table is determined by the following formula: intermediate variable
[0105]
[0106] Table 1. Correspondence of Electrical Parameters for Diode Devices
[0107]
[0108] Step 6: Selecting the Capacitor
[0109] This converter uses a total of 5 capacitors, including the output capacitor Co and capacitors C1 to C4 of the SC unit and the series clamping unit. The capacitance of the output capacitor mainly affects the output voltage ripple, and its parameters are determined by the following formula:
[0110]
[0111] In the formula I out(max) ΔV represents the maximum output current of the converter. OThe maximum allowable output voltage ripple is given by ESR, which is the equivalent series resistance of the output capacitor. These values are determined by the user based on the actual usage conditions.
[0112] For C1 to C4, based on the period of energy release to the load, the parameter values of each capacitor can be calculated as follows:
[0113]
[0114] In the formula P out(max) This is the maximum output power of the converter, which is determined by the user based on actual usage conditions.
[0115] Following steps 1-6 above, the user should reasonably determine the converter's operating frequency f based on their actual usage requirements. sw Input current ripple ΔI in Output voltage ripple ΔV O Maximum output current I out(max) Maximum output power P out(max) By using the relevant formulas, all parameters of the converter can be calculated, thus completing the design of the converter.
[0116] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware, and the program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.
[0117] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.
Claims
1. A high boost ratio DC / DC converter, characterized in that, include: The circuit consists of a switching transistor, a coupling inductor, a switched capacitor unit, a series clamping unit, a rectifier diode, and a parallel-connected output capacitor and load resistor. The switching transistor is used to switch the charging and discharging states of the energy storage element in the DC / DC converter according to the on and off states. The drain of the switching transistor is connected to the same-name terminal of the primary winding of the coupling inductor, and the source of the switching transistor is connected to the negative voltage terminal of the input power supply. The coupling inductor has its primary winding used as the input inductor of the high boost ratio DC / DC converter, and its secondary winding integrated with the switched capacitor unit to prevent high voltage spikes during the turn-off period of the switching transistor. The coupling inductor also includes a magnetizing inductor and a primary leakage inductance on the primary side. The magnetizing inductor is connected in parallel across the primary winding to reduce input current ripple. The primary leakage inductance is connected in series between the positive voltage terminal of the input power supply and the opposite terminal of the primary winding to suppress input current pulsation. The secondary winding is connected between the series clamping unit and the switched capacitor unit. The series clamping unit is connected between the source and drain of the switching transistor. When the switching transistor is off, it absorbs energy from the primary leakage inductance of the coupling inductor, and when the switching transistor is on, it outputs the energy to the switching capacitor unit. The series clamping unit includes a first diode, a third capacitor, and a fourth capacitor. The anode of the first diode is connected to the same-name terminal of the primary winding and the drain of the switching transistor; the cathode of the first diode is connected to the first plate of the third capacitor; the second plate of the third capacitor is connected to the first plate of the fourth capacitor and the same-name terminal of the secondary winding; and the second plate of the fourth capacitor is connected to the source of the switching transistor. The switched capacitor unit includes: a second diode, a third diode, a fourth diode, a first capacitor, and a second capacitor, wherein the anode of the second diode is connected to the cathode of the first diode; the cathode of the second diode is connected to the anode of the third diode at a first node; the cathode of the third diode is connected to the anode of the fourth diode and the opposite terminal of the secondary winding at a second node; the cathode of the fourth diode is connected to the first plate terminal of the second capacitor; the second plate terminal of the second capacitor is connected to the first plate terminal of the first capacitor and the first node; and the second plate terminal of the first capacitor is connected to the drain of the switching transistor; the anode of the rectifier diode is connected to the first plate terminal of the second capacitor and the cathode of the fourth diode; the cathode of the rectifier diode is connected to the first plate terminal of the output capacitor; and the second plate terminal of the output capacitor is connected to the source of the switching transistor.
2. A control method for a high boost ratio DC / DC converter as described in claim 1, characterized in that, include: When the switching transistor is turned on, the primary leakage inductance and magnetizing inductance of the coupling inductor are charged by the input voltage, and the third capacitor in the series clamping unit and the first and second capacitors in the switching capacitor unit are charged by the secondary winding of the coupling inductor and the fourth capacitor in the series clamping unit, and the load resistor is powered by the output capacitor. When the switch is turned off, the first capacitor, the second capacitor, and the primary side of the coupling inductor discharge to supply power to the load resistor. Through the pump-up voltage on the first capacitor and the second capacitor, the discharge effect of the coupling inductor, and the effect of the input voltage, the output voltage value is increased with a high boost ratio.
3. The control method for a high boost ratio DC / DC converter according to claim 2, characterized in that, The boost ratio of a DC / DC converter is determined using the following formula: ， Where D is the duty cycle of the switching transistor. n The turns ratio of the coupled inductor. n =N p / N s , N p The number of turns of the primary winding. N s The number of turns of the secondary winding. V in Input voltage, V O This is the output voltage.
4. The control method for a high boost ratio DC / DC converter according to claim 3, characterized in that, Before the switching transistor is turned on, the magnetizing inductance and primary leakage inductance of the coupling inductor are determined, and the capacitance values of the output capacitor, the first capacitor, the second capacitor, the third capacitor, and the fourth capacitor are determined, wherein... The magnetizing inductance of the coupling inductor is determined by the following formula. L m : in, I O(min) This is the minimum value of the load current. fsw The operating frequency of the DC / DC converter. V in Where is the input voltage, and D is the duty cycle of the switching transistor. k The coupling coefficient of the coupled inductor is given. k The value of is 1. ； The primary leakage inductance of the coupled inductor is determined by the following formula. L lk : ， Where, Δ I in The input current ripple value allowed by the DC / DC converter, the input current ripple value Δ I in The smaller the value, the lower the leakage inductance of the primary edge. L lk The larger the value, and the more likely the original edge leakage inductance is to be. L lk The larger the value, the better the effect of suppressing the pulsation of the input current.
5. The control method for a high boost ratio DC / DC converter according to claim 4, characterized in that, The capacitance value of the output capacitor is determined by the following formula. C O : , The capacitance values of the first capacitor, the second capacitor, the third capacitor, and the fourth capacitor are determined using the following formula: , , in, I out(max) Δ represents the maximum output current of the DC / DC converter. V O The maximum allowable output voltage ripple of the DC / DC converter is given by , and ESR is the equivalent series resistance of the output capacitor. P out(max) This represents the maximum output power of the DC / DC converter. R L The resistance value of the load resistor is given.