LLC power converter
By using a three-transistor LLC converter, two power levels can be switched by combining the switching on of MOSFETs, which solves the problem that existing LLC power converters cannot change power levels, thus improving efficiency and reducing heat generation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- GREE ELECTRIC APPLIANCE INC OF ZHUHAI
- Filing Date
- 2025-02-07
- Publication Date
- 2026-04-28
AI Technical Summary
Existing LLC power converters cannot achieve gear shifting, resulting in poor efficiency.
The LLC converter, which adopts a three-transistor structure, achieves switching between two speeds by controlling the combined turn-on of three types of MOSFETs, and optimizes parameters to improve efficiency.
This achieves maximum efficiency of the LLC power converter under different loads, reduces heat generation, and improves overall efficiency.
Smart Images
Figure CN224178084U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of LLC power technology, and more specifically to an LLC power converter. Background Technology
[0002] With changes in global energy and environmental factors, electric vehicles are gradually replacing gasoline vehicles, and technologies for improving power efficiency have also seen significant development. Among these, LLC resonant power supply technology has been widely used. However, in this technology, LLC resonant power supplies can only operate at one speed, not two speeds. Utility Model Content
[0003] The purpose of this application is to provide an LLC power converter that solves the problem in related technologies that LLC power converters cannot change power levels.
[0004] A first aspect of this application provides an LLC power converter, comprising:
[0005] The first MOSFET has its drain connected to the first terminal of the first capacitor, the second terminal of the first capacitor connected to the first terminal of the first inductor, and the second terminal of the first inductor connected to the first input terminal of the primary winding of the transformer.
[0006] The drain of the second MOSFET is connected to the first terminal of the first capacitor and the drain of the first MOSFET, respectively.
[0007] The source of the second MOS transistor is connected to the second input terminal of the primary winding of the transformer;
[0008] The third MOS transistor, the drain of which is connected to the drain of the second MOS transistor and the first input terminal of the primary winding of the transformer;
[0009] The source of the third MOS transistor is connected to the first terminal of the second capacitor, the second terminal of the second capacitor is connected to the first terminal of the second inductor, and the second terminal of the second inductor is connected to the second input terminal of the primary winding of the transformer.
[0010] The beneficial effects of this invention compared to existing technologies are as follows: It proposes an LLC converter with a first MOSFET S1, a second MOSFET S2, and a third MOSFET S3, enabling two power levels. When the first MOSFET S1 and the second MOSFET S2 are connected, the first power level is achieved; when the third MOSFET S3 is connected, the second power level is achieved. Compared to a traditional half-bridge (two switching transistors), this half-bridge structure has three switching transistors, which are turned on according to a control combination. The resonant cavity consists of two sets of parameters connected in series, allowing for power level switching according to the rated operating power, achieving parameter optimization and maximizing efficiency. Attached Figure Description
[0011] Figure 1 An LLC power converter is provided as an embodiment of this application. Detailed Implementation
[0012] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0013] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” used in the embodiments of this invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. “Multiple” generally includes at least two, but does not exclude the inclusion of at least one.
[0014] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, D and / or B can represent: D alone, D and B simultaneously, or B alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.
[0015] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in a product or system that includes the aforementioned element.
[0016] Figure 1 An LLC power converter according to an embodiment of this application is shown. For ease of explanation, only the parts relevant to this embodiment are shown, and are described in detail below:
[0017] An LLC power converter, comprising:
[0018] The first MOSFET S1 has its drain connected to the first terminal of the first capacitor cr1, the second terminal of the first capacitor cr1 is connected to the first terminal of the first inductor, and the second terminal of the first inductor is connected to the first input terminal of the primary winding Lm1 of the transformer.
[0019] The drain of the second MOSFET S2 is connected to the first terminal of the first capacitor cr1 and the drain of the first MOSFET S1, respectively.
[0020] The source of the second MOS transistor S2 is connected to the second input terminal of the primary winding Lm1 of the transformer.
[0021] The drain of the third MOSFET S3 is connected to the drain of the second MOSFET S2 and the first input terminal of the primary winding Lm2 of the transformer.
[0022] The source of the third MOSFET S3 is connected to the first terminal of the second capacitor cr2, the second terminal of the second capacitor cr2 is connected to the first terminal of the second inductor Lr2, and the second terminal of the second inductor Lr2 is connected to the second input terminal of the primary winding Lm2 of the transformer.
[0023] The above-mentioned technical solution of this application proposes an LLC converter, which is equipped with a first MOSFET S1, a second MOSFET S2, and a third MOSFET S3, and can realize two access levels. When the first MOSFET S1 and the second MOSFET S2 are connected, the first access level is realized, and when the third MOSFET S3 is connected, the second access level is realized.
[0024] In some embodiments, the device further includes a first diode D1, the cathode of which is connected to the drain of the first MOSFET S1. The anode of the first diode D1 is connected to the source of the first MOSFET S1.
[0025] In this embodiment, the first diode D1 serves to prevent the drain current of the first MOSFET S1 from flowing back to the source.
[0026] In some embodiments, a second diode D2 is further included, wherein the cathode of the second diode D2 is connected to the drain of the second MOS transistor S2, and the anode of the second diode D2 is connected to the source of the second MOS transistor S2.
[0027] In this embodiment, the second diode D2 serves to prevent the drain current of the second MOSFET S2 from flowing back to the source.
[0028] In some embodiments, a third diode D3 is further included, the cathode of which is connected to the drain of the third MOSFET S3. The anode of the third diode D3 is connected to the source of the third MOSFET S3.
[0029] In this embodiment, the third diode D3 serves to prevent the drain current of the third MOSFET S3 from flowing back to the source.
[0030] In some embodiments, the transformer is provided with a first secondary winding W1' corresponding to the first primary winding.
[0031] A fourth diode is also provided, the anode of which is connected to the first output terminal of the first secondary winding W1'.
[0032] In some embodiments, a fifth diode D5 is also provided, the anode of which is connected to the second output terminal of the first secondary winding W1'.
[0033] In some embodiments, the transformer is provided with a second secondary winding W2 corresponding to the second primary winding. 、 .
[0034] In some embodiments, a sixth diode D6 is also provided, the anode of which is connected to the second output terminal of the second secondary winding W2'.
[0035] In some embodiments, the first secondary winding W1' includes a first portion W1-1 and a second portion W1-2 connected in series.
[0036] The first terminal of the load resistor r0 is connected between the first part W1-1 and the second part W1-2. The second terminal of the load resistor r0 is connected to the cathode of the fourth diode D4 and the cathode of the fifth diode D5, respectively.
[0037] In some embodiments, the second secondary winding includes a third and a fourth portion connected in series.
[0038] The first end of the load capacitor C2 is connected between the third and fourth parts mentioned above.
[0039] The second end of the load capacitor c2 is connected to the cathode of the fourth diode D4, the cathode of the fifth diode D5, and the second end of the load resistor r0.
[0040] A sixth diode D6 is also provided, the anode of which is connected to the first output terminal of the second secondary winding.
[0041] A seventh diode D7 is also provided, the anode of which is connected to the second output terminal of the second secondary winding.
[0042] In some embodiments, the following examples illustrate:
[0043] Assume that the load of this converter is divided into two levels, 1500W and 3000W.
[0044] Operating principle when working at 1500W and with the switching frequency equal to the resonant frequency: Resonant frequency formula at this time:
[0045]
[0046] First, after the third switch S3 is turned on, the first switch S1 is driven and the zero-voltage switch (ZVS) is turned on. The resonant chain current is greater than the current of the magnetizing inductor, and the seventh diode D7 is turned on. The voltage reflected onto the primary magnetizing inductor causes the magnetizing current to increase linearly. The difference between the input voltage and the output voltage reflected onto the primary side is applied to the resonant chain, generating a sinusoidal resonant current. At time 10, the first switch S1 is turned off. Because the switching frequency is equal to the resonant frequency, the resonant current at this moment is equal to the magnetizing current, and the current of the seventh diode D7 on the secondary side is turned off at zero.
[0047] In the second stage, the seventh diode D7 is cut off, and the first switch S1 is also cut off. There is a time interval during which neither the first switch S1 nor the second switch S2 is conducting. This time interval is also a resonant interval. However, due to the participation of the magnetizing inductor, the resonant frequency is greatly reduced. Since this interval is very short, the resonant current can be considered constant within this interval. Therefore, the junction capacitance of the first switch S1 is charged, and the junction capacitance of the second switch S2 is discharged. When the voltage of the second switch S2 drops to zero, the resonant current will cause the body diode of the second switch S2 to conduct first, so as to ensure that the second switch S2 achieves ZVS turn-on when it is driven. In order to achieve ZVS turn-on of the second switch S2, the dead time must be set to be greater than the time required for the junction capacitance voltage of the second switch S2 to drop to zero.
[0048] In the third stage, the second switch S2 is driven and ZVS is turned on. The resonant chain current is less than the current of the magnetizing inductor, and the fifth diode D5 is turned on. The voltage reflected onto the primary magnetizing inductor causes the magnetizing current to decrease linearly. The output voltage reflected onto the primary side is applied to the resonant chain, generating a sinusoidal resonant current. At time 10, the second switch S2 is turned off. Because the switching frequency is equal to the resonant frequency, the resonant current at this moment is equal to the magnetizing current, and the current of the fifth diode D5 on the secondary side is turned off at zero crossing.
[0049] At the fourth moment, the fifth diode D5 is cut off, and the second switch S2 is also cut off. This interval is also a resonant interval. However, due to the participation of the magnetizing inductor, the resonant frequency is greatly reduced. Since the interval is very short, the resonant current can be considered constant within this interval. Therefore, the junction capacitance of the second switch S2 is charged, and the junction capacitance of the first switch S1 is discharged. When the voltage of the first switch S1 drops to zero, the resonant current will cause the body diode of the first switch S1 to conduct first, so as to ensure that the first switch S1 achieves ZVS turn-on when it is driven. In order to achieve ZVS turn-on of the first switch S1, the dead time must be set to be greater than the time required for the junction capacitance voltage of the first switch S1 to drop to zero.
[0050] The formula for calculating the resonant frequency in a 3000W operating state is:
[0051] First, the first switch S1 is activated and ZVS is turned on. The resonant chain current is greater than the current of the magnetizing inductor, causing the seventh diode D7 and the sixth diode D6 to conduct. The voltage reflected onto the primary magnetizing inductor causes the magnetizing current to increase linearly. The difference between the input voltage and the output voltage reflected onto the primary side is applied to the resonant chain, generating a sinusoidal resonant current. At time 10, the first switch S1 is turned off. Because the switching frequency equals the resonant frequency, the resonant current at this moment is equal to the magnetizing current, and the currents of the seventh diode D7 and the sixth diode D6 on the secondary side cross zero and are turned off.
[0052] In the second stage, diodes D7 (seventh) and D6 (sixth) are off, as are switches S1 and S3. There exists a time interval during which none of these switches conducts. This interval is also a resonant interval. However, due to the involvement of the magnetizing inductor, the resonant frequency is significantly reduced. Since this interval is very short, the resonant current can be considered constant within it. Therefore, the junction capacitance of switch S1 is charged, while the junction capacitances of switches S2 and S3 are discharged. When the voltage across the junctions of switches S2 and S3 drops to zero, the resonant current will cause the body diodes of switches S2 and S3 to conduct first, ensuring that switches S2 and S3 achieve ZVS turn-on when driven. To achieve ZVS turn-on of switches S2 and S3, the dead time must be set to be greater than the time required for the junction capacitance voltage of switches S2 and S3 to drop to zero.
[0053] In the third stage, the second switch S2 and the third switch S3 are driven and ZVS is turned on. The resonant chain current is less than the current of the magnetizing inductor, and the fifth diode D5 and the seventh diode D7 are turned on. The voltage reflected onto the primary magnetizing inductor causes the magnetizing current to decrease linearly. The output voltage reflected onto the primary side is applied to the resonant chain, generating a sinusoidal resonant current. At time 10, the second switch S2 is turned off. Because the switching frequency is equal to the resonant frequency, the resonant current at this moment is equal to the magnetizing current. The current of the fifth diode D5 and the seventh diode D7 on the secondary side crosses zero and are turned off.
[0054] In the fourth stage, diodes D5 and D7 are cut off, as are switches S2 and S3. This interval is also a resonant interval. However, due to the involvement of the magnetizing inductor, the resonant frequency is greatly reduced. Since this interval is very short, the resonant current can be considered constant within it. Therefore, the junction capacitances of switches S2 and S3 are charged, and the junction capacitance of switch S1 is discharged. When the voltage across switch S1 drops to zero, the resonant current will cause the body diode of switch S1 to conduct first, ensuring that switch S1 achieves ZVS turn-on when driven. To achieve ZVS turn-on of switch S1, the dead time must be set to be greater than the time required for the junction capacitance voltage of switch S1 to drop to zero.
[0055] In summary, after receiving the load efficiency level command, the converter operates near its respective resonant frequency at both power levels, improving efficiency. Furthermore, the transformer has advantages over the traditional LLC at low power levels, with higher heat generation and efficiency.
[0056] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.
Claims
1. An LLC power converter, characterized in that, include: The first MOSFET has its drain connected to the first terminal of the first capacitor, the second terminal of the first capacitor connected to the first terminal of the first inductor, and the second terminal of the first inductor connected to the first input terminal of the primary winding of the transformer. The drain of the second MOSFET is connected to the first terminal of the first capacitor and the drain of the first MOSFET, respectively. The source of the second MOS transistor is connected to the second input terminal of the primary winding of the transformer; The third MOS transistor, the drain of which is connected to the drain of the second MOS transistor and the first input terminal of the primary winding of the transformer; The source of the third MOS transistor is connected to the first terminal of the second capacitor, the second terminal of the second capacitor is connected to the first terminal of the second inductor, and the second terminal of the second inductor is connected to the second input terminal of the primary winding of the transformer.
2. The LLC power converter as described in claim 1, characterized in that, It also includes a first diode, the cathode of which is connected to the drain of the first MOS transistor; and the anode of which is connected to the source of the first MOS transistor.
3. The LLC power converter as described in claim 1, characterized in that, It also includes a second diode, the cathode of which is connected to the drain of the second MOS transistor; and the anode of which is connected to the source of the second MOS transistor.
4. The LLC power converter as described in claim 1, characterized in that, It also includes a third diode, the cathode of which is connected to the drain of the third MOS transistor; the anode of which is connected to the source of the third MOS transistor.
5. The LLC power converter as described in claim 1, characterized in that, The transformer is provided with a first secondary winding corresponding to the primary winding; A fourth diode is also provided, the anode of which is connected to the first output terminal of the first secondary winding.
6. The LLC power converter as described in claim 5, characterized in that, A fifth diode is also provided, the anode of which is connected to the second output terminal of the first secondary winding.
7. The LLC power converter as described in claim 5, characterized in that, The transformer is provided with a second secondary winding corresponding to the second primary winding; A fifth diode is also provided, the anode of which is connected to the first output terminal of the second secondary winding.
8. The LLC power converter as described in claim 7, characterized in that, A sixth diode is also provided, the anode of which is connected to the second output terminal of the second secondary winding.
9. The LLC power converter as described in claim 7, characterized in that, The first secondary winding consists of a first part and a second part connected in series; The first end of the load resistor is connected between the first part and the second part; The second end of the load resistor is connected to the cathode of the fourth diode and the cathode of the fifth diode, respectively.
10. The LLC power converter as described in claim 9, characterized in that, The second secondary winding includes a third part and a fourth part connected in series; The first end of the load capacitor is connected between the third and fourth parts; The second terminal of the load capacitor is connected to the cathode of the fourth diode, the cathode of the fifth diode, and the second terminal of the load resistor, respectively. A sixth diode is also provided, the anode of which is connected to the first output terminal of the second secondary winding; A seventh diode is also provided, the anode of which is connected to the second output terminal of the second secondary winding.