CN108768178B - LLC resonance half-bridge circuit with wide voltage input - Google Patents
LLC resonance half-bridge circuit with wide voltage input Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of DC power input into DC power output
- H02M3/22—Conversion of DC power input into DC power output with intermediate conversion into AC
- H02M3/24—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters
- H02M3/28—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC
- H02M3/325—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33569—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of DC power input into DC power output
- H02M3/22—Conversion of DC power input into DC power output with intermediate conversion into AC
- H02M3/24—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters
- H02M3/28—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC
- H02M3/325—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33507—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
- H02M3/33523—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0048—Circuits or arrangements for reducing losses
- H02M1/0054—Transistor switching losses
- H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
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- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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Abstract
本发明公开了一种宽电压输入的LLC谐振半桥电路，包括第一芯片U1、第一MOS管Q1、第一二极管D1、第二二极管D2、第三二极管D3、第四二极管D4、第五二极管D5、第一电容C1、第二电容C2、第三电容C3、第四电容C4、第一电阻R1、第二电阻R2、第三电阻R3、第四电阻R4、第五电阻R5、LLC变压器T1、信号控制电路和LLC反馈电路，其中，所述LLC变压器T1的次级输出端至少设置4个绕组分别形成第一输出回路和第二输出回路。本发明通过改变LLC变压器的匝比，并且在一定频率范围内，通过改变匝比实现电压的稳定输出；通过增加变压器的输出，提高输入电压的范围。
The invention discloses a wide-voltage input LLC resonant half-bridge circuit, comprising a first chip U1, a first MOS transistor Q1, a first diode D1, a second diode D2, a third diode D3, a Four diodes D4, fifth diode D5, first capacitor C1, second capacitor C2, third capacitor C3, fourth capacitor C4, first resistor R1, second resistor R2, third resistor R3, fourth Resistor R4, fifth resistor R5, LLC transformer T1, signal control circuit and LLC feedback circuit, wherein at least 4 windings are set at the secondary output end of the LLC transformer T1 to form a first output loop and a second output loop respectively. The invention realizes the stable output of voltage by changing the turns ratio of the LLC transformer and within a certain frequency range by changing the turns ratio; and increases the range of the input voltage by increasing the output of the transformer.
Description
技术领域technical field
本发明涉及电源技术领域，尤其涉及一种宽电压输入的LLC谐振半桥电路。The invention relates to the technical field of power supplies, in particular to an LLC resonant half-bridge circuit with wide voltage input.
背景技术Background technique
在光伏电池、光伏电池、燃料电池和电动汽车锂电池等各类电源设备应用中，由于其输入电压范围变化大，需要宽输入范围的LLC谐振变换电路，LLC变换电路作为电源拓扑具有零电压导通和零电流关断等功能，可以实现非常高的效率。但其输入电压的范围具有一定的限制。In the application of various power equipment such as photovoltaic cells, photovoltaic cells, fuel cells and lithium batteries for electric vehicles, due to the large variation of the input voltage range, LLC resonant conversion circuits with a wide input range are required. LLC conversion circuits as a power topology have zero voltage conduction. Features such as turn-on and zero-current turn-off allow for very high efficiency. However, the range of its input voltage has certain limitations.
为了实现LLC的宽电压输入，传统方法有如下三种：In order to realize the wide voltage input of LLC, there are three traditional methods as follows:
(1)LLC谐振变换器的频率的变化范围变的更大。(1) The variation range of the frequency of the LLC resonant converter becomes larger.
(2)减小LLC谐振变换器的k值，k值越小变压器的增益变化范围就越大。(2) Reduce the k value of the LLC resonant converter. The smaller the k value is, the greater the gain variation range of the transformer.
(3)在LLC输入端增加一个升压转换器，当输入电压低于某个范围时使输入的电压升高的LLC的输入范围内。(3) A boost converter is added at the input end of the LLC, and when the input voltage is lower than a certain range, the input voltage is raised within the input range of the LLC.
上述的方法都存在着一定的缺陷：当LLC的频率具有很大的变化范围时，如果工作频率向下远离谐振频率时，就会导致更大的循环电流、磁化器件的体积和更低的效率；为了减小k值，则会导致更大的谐振电感LR或更小的激励电感Lm，却大大降低了LLC谐振变换器的效率；在LLC输入端增加一个升压转换器将会导致电源的体积和成本都很高。The above methods all have certain drawbacks: when the frequency of the LLC has a large range of variation, if the operating frequency is downward away from the resonant frequency, it will lead to a larger circulating current, the size of the magnetized device, and a lower efficiency. ; In order to reduce the value of k, it will lead to a larger resonant inductance LR or a smaller excitation inductance Lm, but greatly reduce the efficiency of the LLC resonant converter; adding a boost converter to the LLC input will cause the power The size and cost are high.
故，针对现有技术的缺陷，实有必要提出一种技术方案以解决现有技术存在的技术问题。Therefore, in view of the defects of the prior art, it is necessary to propose a technical solution to solve the technical problems existing in the prior art.
发明内容SUMMARY OF THE INVENTION
有鉴于此，本发明提出了一种宽电压输入的LLC谐振半桥电路，利用MOS管和具有两端输出的变压器，从而将输入电压低的匝比变大，有效改善了LLC的性能，同时减小LLC变换器的体积和重量。In view of this, the present invention proposes a wide-voltage input LLC resonant half-bridge circuit, which utilizes a MOS tube and a transformer with outputs at both ends, thereby increasing the turns ratio of a low input voltage, effectively improving the LLC performance, and at the same time. Reduce the size and weight of LLC converters.
为了解决现有技术存在的技术问题，本发明的技术方案如下：In order to solve the technical problems existing in the prior art, the technical scheme of the present invention is as follows:
一种宽电压输入的LLC谐振半桥电路，包括第一芯片U1、第一MOS管Q1、第一二极管D1、第二二极管D2、第三二极管D3、第四二极管D4、第五二极管D5、第一电容C1、第二电容C2、第三电容C3、第四电容C4、第一电阻R1、第二电阻R2、第三电阻R3、第四电阻R4、第五电阻R5、LLC变压器T1、信号控制电路和LLC反馈电路，其中，所述LLC变压器T1的次级输出端至少设置4个绕组分别形成第一输出回路和第二输出回路，所述信号控制电路与第一MOS管Q1的栅极相连接，用于根据前级功率因数校正电路输出的电压VOPFC控制所述第一MOS管Q1接通第一输出回路或者第二输出回路至输出端；所述LLC反馈电路用于反馈输出端电压信号至第一芯片U1；A wide-voltage input LLC resonant half-bridge circuit includes a first chip U1, a first MOS transistor Q1, a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4, fifth diode D5, first capacitor C1, second capacitor C2, third capacitor C3, fourth capacitor C4, first resistor R1, second resistor R2, third resistor R3, fourth resistor R4, Five resistors R5, LLC transformer T1, signal control circuit and LLC feedback circuit, wherein at least 4 windings are set at the secondary output end of the LLC transformer T1 to form a first output loop and a second output loop respectively, the signal control circuit It is connected to the gate of the first MOS transistor Q1, and is used to control the first MOS transistor Q1 to connect the first output loop or the second output loop to the output terminal according to the voltage VOPFC output by the power factor correction circuit of the previous stage; The LLC feedback circuit is used for feeding back the output terminal voltage signal to the first chip U1;
所述第一输出回路工作时中，LLC变压器T1的第四脚与第一二极管D1的正端相连，LLC变压器T1的第六脚与第二二极管D2的正端相连，所述第一二极管D1的负端、第二二极管D2的负端、第三电容C3的一端相连共同作为输出正端，所述第三电容C3的另一端与LLC变压器T1的第五脚相连接作为输出负端；During the operation of the first output loop, the fourth pin of the LLC transformer T1 is connected to the positive end of the first diode D1, and the sixth pin of the LLC transformer T1 is connected to the positive end of the second diode D2. The negative end of the first diode D1, the negative end of the second diode D2, and one end of the third capacitor C3 are connected together as an output positive end, and the other end of the third capacitor C3 is connected to the fifth pin of the LLC transformer T1. connected as the output negative terminal;
所述第二输出回路工作时中，LLC变压器T1的第三脚与第四二极管D4的正端相连，LLC变压器T1的第七脚与第五二极管D5的正端相连，所述第四二极管D4的负端、第五二极管D5的负端、第一MOS管Q1的漏极相连接，第一MOS管Q1的源极与第三电容C3的一端相连共同作为输出正端，所述第三电容C3的另一端与LLC变压器T1的第五脚相连接作为输出负端；During the operation of the second output loop, the third pin of the LLC transformer T1 is connected to the positive end of the fourth diode D4, and the seventh pin of the LLC transformer T1 is connected to the positive end of the fifth diode D5. The negative terminal of the fourth diode D4, the negative terminal of the fifth diode D5, and the drain of the first MOS transistor Q1 are connected, and the source of the first MOS transistor Q1 is connected to one end of the third capacitor C3 as an output. Positive end, the other end of the third capacitor C3 is connected with the fifth pin of the LLC transformer T1 as the output negative end;
第一芯片U1的第一引脚与第一二极管D1的正端、12V电压端相连接，所述第一二极管D1的负端与第一芯片U1的第十四引脚、第一电容C1的一端相连接，所述第一电容C1的另一端与第一芯片U1的第十三引脚、第二电容C2的一端相连接，所述第二电容C2的另一端与LLC变压器T1初级绕组的第一脚相连接，第一芯片U1的第八引脚与LLC变压器T1初级绕组的第二脚、第五电阻R5的一端相连接，所述第五电阻R5的另一端与第一芯片U1的第十引脚相连共同与输入负端相连接；第一芯片U1的第十六引脚与第一电阻R1的一端相连共同与输入正端相连接，所述第一电阻R1的另一端与第三电阻R3的一端、第一芯片U1的第五引脚相连接，所述第三电阻R3的另一端与第一芯片U1的第四引脚、第四电容C4的一端相连接，所述第四电容C4的另一端与、第一芯片U1的第六引脚、LLC反馈电路的输出端相连接；The first pin of the first chip U1 is connected to the positive end and the 12V voltage end of the first diode D1, and the negative end of the first diode D1 is connected to the fourteenth pin and the fourth pin of the first chip U1. One end of a capacitor C1 is connected, the other end of the first capacitor C1 is connected to the thirteenth pin of the first chip U1, and one end of the second capacitor C2 is connected, and the other end of the second capacitor C2 is connected to the LLC transformer The first pin of the primary winding of T1 is connected, the eighth pin of the first chip U1 is connected with the second pin of the primary winding of the LLC transformer T1, and one end of the fifth resistor R5, and the other end of the fifth resistor R5 is connected with the first pin of the LLC transformer T1. The tenth pin of a chip U1 is connected to the negative terminal of the input; the sixteenth pin of the first chip U1 is connected to one end of the first resistor R1 and is connected to the positive terminal of the input. The other end is connected to one end of the third resistor R3 and the fifth pin of the first chip U1, and the other end of the third resistor R3 is connected to the fourth pin of the first chip U1 and one end of the fourth capacitor C4 , the other end of the fourth capacitor C4 is connected to the sixth pin of the first chip U1 and the output end of the LLC feedback circuit;
所述第一芯片U1采用LCS702芯片。The first chip U1 adopts an LCS702 chip.
作为优选的技术方案，所述信号控制电路进一步包括第六电阻R6、第七电阻R7、第八电阻R8、第九电阻R9、第十电阻R10、第二芯片U2、第三芯片U3和基准源VREF；其中，所述第二芯片U2为比较器，所述第三芯片U3为光耦芯片。As a preferred technical solution, the signal control circuit further includes a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, a second chip U2, a third chip U3 and a reference source VREF; wherein, the second chip U2 is a comparator, and the third chip U3 is an optocoupler chip.
作为优选的技术方案，所述第一MOS管Q1采用A类P沟道MOS场效应晶体管。As a preferred technical solution, the first MOS transistor Q1 adopts a type A P-channel MOS field effect transistor.
作为优选的技术方案，所述LLC反馈电路采用光耦芯片实现。As a preferred technical solution, the LLC feedback circuit is implemented with an optocoupler chip.
与现有技术相比，本发明具有如下技术效果：Compared with the prior art, the present invention has the following technical effects:
1、提高宽输入电压范围以及输出效率；1. Improve wide input voltage range and output efficiency;
2、降低成本和电路的复杂程度；2. Reduce cost and circuit complexity;
3、减小LLC变换器的体积。3. Reduce the volume of LLC converter.
附图说明Description of drawings
图1为本发明宽电压输入的LLC谐振半桥电路的电路原理图。FIG. 1 is a circuit schematic diagram of an LLC resonant half-bridge circuit with wide voltage input according to the present invention.
图2为本发明中信号控制电路的原理图。FIG. 2 is a schematic diagram of a signal control circuit in the present invention.
图3为本发明中LLC反馈电路的原理示意图。FIG. 3 is a schematic diagram of the principle of the LLC feedback circuit in the present invention.
如下具体实施例将结合上述附图进一步说明本发明。The following specific embodiments will further illustrate the present invention in conjunction with the above drawings.
具体实施方式Detailed ways
以下将结合附图对本发明提供的技术方案作进一步说明。The technical solutions provided by the present invention will be further described below with reference to the accompanying drawings.
自从LLC谐振技术问世以来，一直应用于计算机、通信供电、LED照明、光伏电池、燃料电池和电动汽车锂电池等各类需要高效、稳定输出的电源设备中。然而对于传统的LLC谐振电路，当输入电压范围增大时，开关频率调节范围需随之增大，此时可能出现的高压输入会引起过高的开关频率，激化电路寄生参数等对系统带来的影响。同时，为适应较宽范围的输入电压，励磁电感往往需要设计得较小，从而引起变换器谐振电流增加，以致系统导通损耗和磁滞损耗随之增加，大大降低变换器效率。Since the advent of LLC resonance technology, it has been used in various power supply equipment that requires high efficiency and stable output, such as computers, communication power supplies, LED lighting, photovoltaic cells, fuel cells, and lithium batteries for electric vehicles. However, for the traditional LLC resonant circuit, when the input voltage range increases, the switching frequency adjustment range needs to increase accordingly. The possible high voltage input at this time will cause an excessively high switching frequency, and the parasitic parameters of the excitation circuit will bring about the system. Impact. At the same time, in order to adapt to a wide range of input voltage, the excitation inductance often needs to be designed to be small, which will cause the resonant current of the converter to increase, so that the system conduction loss and hysteresis loss will increase, which greatly reduces the efficiency of the converter.
为了解决上述技术问题，参见图1，所示为本发明提供一种宽电压输入的LLC谐振半桥电路的电路原理图，包括第一芯片U1、第一MOS管Q1、第一二极管D1、第二二极管D2、第三二极管D3、第四二极管D4、第五二极管D5、第一电容C1、第二电容C2、第三电容C3、第四电容C4、第一电阻R1、第二电阻R2、第三电阻R3、第四电阻R4、第五电阻R5、LLC变压器T1、信号控制电路和LLC反馈电路，其中，所述LLC变压器T1的次级输出端至少设置4个绕组分别形成第一输出回路和第二输出回路，所述信号控制电路与第一MOS管Q1的栅极相连接，用于根据前级功率因数校正电路输出的电压VOPFC控制所述第一MOS管Q1接通第一输出回路或者第二输出回路至输出端；所述LLC反馈电路用于反馈输出端电压信号至第一芯片U1；In order to solve the above technical problems, referring to FIG. 1 , it is a circuit schematic diagram of a wide-voltage input LLC resonant half-bridge circuit provided by the present invention, including a first chip U1 , a first MOS transistor Q1 , and a first diode D1 , the second diode D2, the third diode D3, the fourth diode D4, the fifth diode D5, the first capacitor C1, the second capacitor C2, the third capacitor C3, the fourth capacitor C4, the A resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, an LLC transformer T1, a signal control circuit and an LLC feedback circuit, wherein the secondary output end of the LLC transformer T1 is set at least The four windings form a first output loop and a second output loop respectively, and the signal control circuit is connected to the gate of the first MOS transistor Q1, and is used to control the first output circuit according to the voltage V OPFC output by the power factor correction circuit of the previous stage. A MOS transistor Q1 connects the first output loop or the second output loop to the output end; the LLC feedback circuit is used to feed back the voltage signal of the output end to the first chip U1;
所述第一输出回路工作时中，LLC变压器T1的第四脚与第一二极管D1的正端相连，LLC变压器T1的第六脚与第二二极管D2的正端相连，所述第一二极管D1的负端、第二二极管D2的负端、第三电容C3的一端相连共同作为输出正端，所述第三电容C3的另一端与LLC变压器T1的第五脚相连接作为输出负端；During the operation of the first output loop, the fourth pin of the LLC transformer T1 is connected to the positive end of the first diode D1, and the sixth pin of the LLC transformer T1 is connected to the positive end of the second diode D2. The negative end of the first diode D1, the negative end of the second diode D2, and one end of the third capacitor C3 are connected together as an output positive end, and the other end of the third capacitor C3 is connected to the fifth pin of the LLC transformer T1. connected as the output negative terminal;
所述第二输出回路工作时中，LLC变压器T1的第三脚与第四二极管D4的正端相连，LLC变压器T1的第七脚与第五二极管D5的正端相连，所述第四二极管D4的负端、第五二极管D5的负端、第一MOS管Q1的漏极相连接，第一MOS管Q1的源极与第三电容C3的一端相连共同作为输出正端，所述第三电容C3的另一端与LLC变压器T1的第五脚相连接作为输出负端；During the operation of the second output loop, the third pin of the LLC transformer T1 is connected to the positive end of the fourth diode D4, and the seventh pin of the LLC transformer T1 is connected to the positive end of the fifth diode D5. The negative terminal of the fourth diode D4, the negative terminal of the fifth diode D5, and the drain of the first MOS transistor Q1 are connected, and the source of the first MOS transistor Q1 is connected to one end of the third capacitor C3 as an output. Positive end, the other end of the third capacitor C3 is connected with the fifth pin of the LLC transformer T1 as the output negative end;
第一芯片U1的第一引脚与第一二极管D1的正端、12V电压端相连接，所述第一二极管D1的负端与第一芯片U1的第十四引脚、第一电容C1的一端相连接，所述第一电容C1的另一端与第一芯片U1的第十三引脚、第二电容C2的一端相连接，所述第二电容C2的另一端与LLC变压器T1初级绕组的第一脚相连接，第一芯片U1的第八引脚与LLC变压器T1初级绕组的第二脚、第五电阻R5的一端相连接，所述第五电阻R5的另一端与第一芯片U1的第十引脚相连共同与输入负端相连接；第一芯片U1的第十六引脚与第一电阻R1的一端相连共同与输入正端相连接，所述第一电阻R1的另一端与第三电阻R3的一端、第一芯片U1的第五引脚相连接，所述第三电阻R3的另一端与第一芯片U1的第四引脚、第四电容C4的一端相连接，所述第四电容C4的另一端与、第一芯片U1的第六引脚、LLC反馈电路的输出端相连接；The first pin of the first chip U1 is connected to the positive end and the 12V voltage end of the first diode D1, and the negative end of the first diode D1 is connected to the fourteenth pin and the fourth pin of the first chip U1. One end of a capacitor C1 is connected, the other end of the first capacitor C1 is connected to the thirteenth pin of the first chip U1, and one end of the second capacitor C2 is connected, and the other end of the second capacitor C2 is connected to the LLC transformer The first pin of the primary winding of T1 is connected, the eighth pin of the first chip U1 is connected with the second pin of the primary winding of the LLC transformer T1, and one end of the fifth resistor R5, and the other end of the fifth resistor R5 is connected with the first pin of the LLC transformer T1. The tenth pin of a chip U1 is connected to the negative terminal of the input; the sixteenth pin of the first chip U1 is connected to one end of the first resistor R1 and is connected to the positive terminal of the input. The other end is connected to one end of the third resistor R3 and the fifth pin of the first chip U1, and the other end of the third resistor R3 is connected to the fourth pin of the first chip U1 and one end of the fourth capacitor C4 , the other end of the fourth capacitor C4 is connected to the sixth pin of the first chip U1 and the output end of the LLC feedback circuit;
所述第一芯片U1采用LCS702芯片。The first chip U1 adopts an LCS702 chip.
在上述技术方案中，本发明采用内置两个MOSFET的LCS702作为控制IC。DT/BF引脚上的电阻分压器R2和R4是用来设置死区时间、启动时的最大频率和突发阈值频率。反馈引脚(FB)是用来控制IC的输出频率。输出的频率与输入反馈引脚的电流成正比。In the above technical solution, the present invention adopts the LCS702 with two built-in MOSFETs as the control IC. Resistor dividers R2 and R4 on the DT/BF pin are used to set the dead time, maximum frequency at start-up and burst threshold frequency. The feedback pin (FB) is used to control the output frequency of the IC. The frequency of the output is proportional to the current input to the FEEDBACK pin.
上述技术方案中，12V电压端由前级辅助电源提供。In the above technical solution, the 12V voltage terminal is provided by the auxiliary power supply of the previous stage.
采用上述技术方案，本发明通过改变LLC变压器T1的匝比，并且在一定频率范围内，通过改变匝比实现电压的稳定输出。比传统LLC变压器增加了一组输出，通过增加变压器的输出，可以改变输出电压的大小。当输入电压为额定标准输入范围时，第一输出回路接通工作，由于Q1为截止状态，第二输出回路断开。当LLC变压器的输入电压线性下降到低压输入范围时，Q1为了满足保持时间要求开始导通，此时，第二输出回路接通工作，第一输出回路断开。当Q1导通时，次级二极管(D1，D2)由于反向偏置而关断，并且供电电流仅流过辅助二极管(D4和D5)，此时原副边的匝比减小，输出电压增大开关频率增高。根据模式变化的结果，变压器的有效匝数比在不同的条件下发生变化，变换器可以通过改变匝数比来获得更高的直流增益。当输入电压低于LLC输入电压的范围的时候，通过LLC变压器T1的副边绕组增大提高LLC的输出的电压。By adopting the above technical scheme, the present invention realizes the stable output of the voltage by changing the turns ratio of the LLC transformer T1, and within a certain frequency range, by changing the turns ratio. Compared with the traditional LLC transformer, a set of outputs is added. By increasing the output of the transformer, the size of the output voltage can be changed. When the input voltage is within the rated standard input range, the first output loop is connected to work, and since Q1 is in an off state, the second output loop is disconnected. When the input voltage of the LLC transformer drops linearly to the low-voltage input range, Q1 starts to conduct in order to meet the holding time requirement. At this time, the second output loop is turned on and the first output loop is turned off. When Q1 is turned on, the secondary diodes (D1, D2) are turned off due to reverse bias, and the supply current only flows through the auxiliary diodes (D4 and D5), at this time, the turns ratio of the primary and secondary sides is reduced, and the output voltage Increasing the switching frequency increases. According to the result of the mode change, the effective turns ratio of the transformer changes under different conditions, and the converter can obtain higher DC gain by changing the turns ratio. When the input voltage is lower than the range of the LLC input voltage, the voltage of the output of the LLC is increased by increasing the secondary winding of the LLC transformer T1.
以下再详细介绍本发明的设计过程，在一种优选的实施方式中，将输入电压的范围设置在250～380VDC的范围内，将此输入范围分成标准输入范围(310～380VDC)和低压输入范围(250～310VDC)。The design process of the present invention will be described in detail below. In a preferred embodiment, the input voltage range is set within the range of 250-380V DC , and the input range is divided into standard input range (310-380V DC ) and low voltage Input range (250 to 310V DC ).
确定了输入范围就可以确定输入范围内的k值和Q值，所确定的k值和Q值要满足够的增益。把变换器最大输入电压情况下的工作频率与谐振频率相等，这样在确保在运行时工作频率fs小于等于谐振频率fr1，实现MOSFET的ZVS和次级整流二极管的ZCS模式。由于fs＝fr1，增益M可表示：After the input range is determined, the k value and Q value in the input range can be determined, and the determined k value and Q value should be full enough gain. The working frequency of the converter under the condition of the maximum input voltage is equal to the resonant frequency, so as to ensure that the working frequency fs is less than or equal to the resonant frequency fr1 during operation, and realize the ZVS mode of the MOSFET and the ZCS mode of the secondary rectifier diode. Since fs=fr1, the gain M can be expressed as:
一般在设计的时候将k值取在5～10之间，这里将k值取值为7，所以在标称输入范围时的最小和最大增益如公式(2)和(3)所示：Generally, the value of k is set to be between 5 and 10 during the design. Here, the value of k is set to be 7, so the minimum and maximum gains in the nominal input range are shown in formulas (2) and (3):
一般在最大增益上再取10～15％的预留空间，此时将增益M取为1.5，可以得出此时的Q值为0.41。再将低压输入范围260～310VDC的最大和最小值代入上面的公式，可以分别求出Mmin和Mmax的值为1.14和1.35，与标称输入的直流增益还要小，所以取值的增益M也取为1.5。Generally, a reserved space of 10-15% is taken on the maximum gain. At this time, the gain M is taken as 1.5, and the Q value at this time can be obtained as 0.41. Substitute the maximum and minimum values of the low-voltage input range of 260-310V DC into the above formula, and the values of M min and M max can be calculated to be 1.14 and 1.35, respectively, which are smaller than the DC gain of the nominal input, so the value of The gain M is also taken as 1.5.
假设设计一个输出电压为48V的150W的驱动器，因此，变压器的匝数比n为4.9。Suppose you design a 150W driver with an output voltage of 48V. Therefore, the transformer turns ratio n is 4.9.
由公式(5)，可以得出变压器的初级等效负载阻抗Rac。From formula (5), the primary equivalent load impedance R ac of the transformer can be obtained.
其中，RO为输出电阻也就是输出的负载，所以计算的出Rac在满载时的等效阻抗为246Ω。Among them, R O is the output resistance, that is, the output load, so the calculated equivalent impedance of R ac at full load is 246Ω.
谐振网络中的参数CR、LR和LP是根据k值和Q值来设计的，根据上面步骤所取的k值和Q值要确保足够的峰值增益，通过选取的k和Q值来确定谐振网络参数的值如下所示：The parameters CR , LR and LP in the resonant network are designed according to the k value and Q value. According to the k value and Q value taken in the above steps, it is necessary to ensure sufficient peak gain. Determine the values of the resonant network parameters as follows:
在低压输入范围(250～300)时:通过上面的公式，此时最大的输入电压变为300V。通过公式(4)可知此时变压器匝数比n变小了，匝比(n)的改变导致等效阻抗Rac也随之改变，此时的n和Rac分别为3.63和178Ω。由于在260～310VDC的输入范围时，谐振网络的元器件是固定不变，所以Rac值的减小导致了Q值的增大，由公式(9)得出Q值为0.55，此时的增益为1.40。In the low voltage input range (250～300): Through the above formula, the maximum input voltage becomes 300V at this time. According to formula (4), it can be known that the transformer turns ratio n becomes smaller at this time, and the change of the turns ratio (n) causes the equivalent impedance Rac to change. At this time, n and Rac are 3.63 and 178Ω, respectively. Since in the input range of 260 ~ 310V DC , the components of the resonant network are fixed, so the reduction of the Rac value leads to the increase of the Q value. The Q value is 0.55 from the formula (9). At this time, the The gain is 1.40.
因此，当输入电压VOPFC在标准范围(310～380V)时，Q1开关管此时关断，此时输出的电压由次级绕组的NS提供。当输入电压在低压范围(260～310V)之内，则Q1导通，此时输出的电压由次级绕组NA提供。Therefore, when the input voltage V OPFC is in the standard range (310-380V), the Q1 switch is turned off at this time, and the output voltage is provided by the NS of the secondary winding. When the input voltage is within the low-voltage range (260-310V), Q1 is turned on, and the output voltage is provided by the secondary winding NA.
参见图2，所示为本发明信号控制电路的原理框图，进一步包括第六电阻R6、第七电阻R7、第八电阻R8、第九电阻R9、第十电阻R10、第二芯片U2、第三芯片U3和基准源VREF；其中，所述第二芯片U2为比较器，所述第三芯片U3为光耦芯片。Referring to FIG. 2, it is a schematic block diagram of the signal control circuit of the present invention, which further includes a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, a second chip U2, a third A chip U3 and a reference source VREF; wherein, the second chip U2 is a comparator, and the third chip U3 is an optocoupler chip.
当输入电压VOPFC大于310V时，输入比较器负端电压比基准电压高，比较器输出低电平，使开关管关断，输出的给负载RL的电压为第一输出回路VO1的电压；当输入电压VOPFC小于于310V时，输入负端比较器的电压比基准电压低，比较器输出高电平，使开关管导通，此时VO1被二极管方向截止，所以给负载RL的电压为VO2的电压。When the input voltage V OPFC is greater than 310V, the negative terminal voltage of the input comparator is higher than the reference voltage, the comparator outputs a low level, the switch is turned off, and the output voltage to the load RL is the voltage of the first output loop V O1 ; When the input voltage V OPFC is less than 310V, the voltage of the input negative comparator is lower than the reference voltage, the comparator outputs a high level, and the switch is turned on. At this time, V O1 is cut off by the diode direction, so the load R L The voltage is the voltage of V O2 .
在一种优选实施方式中，所述第一MOS管Q1采用A类P沟道MOS场效应晶体管。In a preferred embodiment, the first MOS transistor Q1 is a type A P-channel MOS field effect transistor.
在一种优选实施方式中，所述LLC反馈电路采用光耦芯片实现。参见图3，所示为本发明LLC反馈电路的原理示意图，光耦芯片通过ROPTO电阻来驱动LCS702的反馈引脚，ROPTO可以限制流入FB引脚的最大光耦电流，一般ROPTO选择1.2kΩ的电阻。电容器C4可以对FB引脚进行滤波，本方案选择工作频率为250kHz的电容器C4的值为4.7nF。电阻器RLOAD可以加载光耦器的输出，以强制它以相对较高的静态电流进行工作，从而提高其增益，电阻器RLOAD一般取值为4.7kΩ。二极管D在电路中的作用是将ROPTO从软启动网络隔离出来。In a preferred embodiment, the LLC feedback circuit is implemented with an optocoupler chip. Referring to Figure 3, the schematic diagram of the LLC feedback circuit of the present invention is shown. The optocoupler chip drives the feedback pin of the LCS702 through the R OPTO resistor. The R OPTO can limit the maximum optocoupler current flowing into the FB pin. Generally, the R OPTO selects 1.2 resistance in kΩ. Capacitor C4 can filter the FB pin. In this scheme, the value of capacitor C4 with an operating frequency of 250kHz is selected to be 4.7nF. Resistor R LOAD can load the output of the optocoupler to force it to operate at a relatively high quiescent current, thereby increasing its gain. Resistor R LOAD is typically 4.7kΩ. The role of diode D in the circuit is to isolate R OPTO from the soft-start network.
以上实施例的说明只是用于帮助理解本发明的方法及其核心思想。应当指出，对于本技术领域的普通技术人员来说，在不脱离本发明原理的前提下，还可以对本发明进行若干改进和修饰，这些改进和修饰也落入本发明权利要求的保护范围内。The descriptions of the above embodiments are only used to help understand the method and the core idea of the present invention. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can also be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.
对所公开的实施例的上述说明，使本领域专业技术人员能够实现或使用本发明。对这些实施例的多种修改对本领域的专业技术人员来说将是显而易见的，本文中所定义的一般原理可以在不脱离本发明的精神或范围的情况下，在其它实施例中实现。因此，本发明将不会被限制于本文所示的这些实施例，而是要符合与本文所公开的原理和新颖特点相一致的最宽的范围。The above description of the disclosed embodiments enables any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
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