WO2024045798A1

WO2024045798A1 - Non-isolated llc resonant converter

Info

Publication number: WO2024045798A1
Application number: PCT/CN2023/102032
Authority: WO
Inventors: 李斌; 李培永; 杨鑫; 周远平; 乔宗标
Original assignee: 上海英联电子系统有限公司
Priority date: 2022-08-30
Filing date: 2023-06-25
Publication date: 2024-03-07
Also published as: CN115425838A

Abstract

The present invention provides a non-isolated LLC resonant converter, comprising a first resonant bridge, a second resonant bridge, a resonant network, a rectifier bridge, a transformer, a load, and an output capacitor. The transformer comprises a first transformer inductor and a second transformer inductor. The circuit is simple, the control is simple and easy, and the cost is low.

Description

Non-Isolated LLC Resonant Converter

This application requires the priority of a Chinese patent application with a filing date of August 30, 2022, an application number of 2022110568862, and an invention titled "Non-Isolated LLC Resonant Converter". The contents of the above application are incorporated herein by reference.

Technical field

The present invention relates to the field of power supply technology, and in particular, to a non-isolated LLC resonant converter.

Background technique

In recent years, with the increase in computing volume, the power demand of server single boards has become larger and larger. Especially with the widespread use of rack-mounted servers, the current of the DC power supply bus has become larger and larger. The 48V bus is used to power server boards. The power supply architecture gradually replaces the traditional architecture of the 12V bus; this 48V architecture usually converts the AC grid power into a 48V DC bus through the AC power supply, and then converts the 48V to 12V by the DCDC power supply, and then converts the 12V to what each chipset requires. Various voltages as low as 0.6V are used to power the chipset. There are also some solutions that directly convert 48V into a CPU core voltage of about 1V to power the CPU. Since in server systems, in addition to each chipset requiring low-voltage power supply as low as 0.6V, there are also many 12V loads, such as fans and memory. The method of converting 48V to 12V and then converting 12V to voltage to power the chipset has gradually become mainstream.

On the one hand, the server market is huge and the cost pressure is high; on the other hand, the global requirements for energy conservation and consumption reduction are getting higher and higher, which makes low-cost, high-efficiency 48V to 12V It has become a very important research direction in the field of power electronics. Many research resources have entered this field, and many research results have been presented one after another. There are two technical directions that have been most widely used: One direction is to continuously optimize the design based on the 48V to 12V module power supply that is widely used in the traditional communication field. In recent years, new products have been launched in this direction, and power density and efficiency have also increased year by year; most leading companies use isolated half-bridge or full-bridge hard switching circuits, and a few use isolated half-bridge or full-bridge non-isolated LLC resonance Converter circuit; in order to achieve higher efficiency and power density, this development direction continues to increase the number of layers and copper thickness of PCB boards, constantly optimize the design of isolation transformers, and select power MOS tubes with better performance. The consequences of this are Continuously pushing up the cost of products, lengthening the development cycle, increasing design difficulty and technical requirements for technicians have made the development in this direction reach a bottleneck, making it difficult to continue to balance development between performance and price. The other direction is non-isolated 48V to 12V applications, and the corresponding switched tank converter resonant converter (Switched Tank Converters, STC) was first introduced, as shown in Figure 4. This converter is cascaded through a multi-stage resonant circuit, which can realize soft switching of all switching devices, and the stress of the switching devices is effectively controlled through the series connection of the switching devices and the output voltage clamping, so that the efficiency of the converter is at a lower level. The cost has been very effectively improved, making this circuit a hot spot in the research field. However, this circuit also has two inherent shortcomings: first, the converter is a resonant scheme of a switched capacitor circuit, the relationship between the input and output voltages is a fixed transformation ratio, and voltage regulation cannot be performed, which greatly limits the application of the converter, especially in After several leading companies successively shifted their server power supply solutions to 12V voltage controllable, the attention of this circuit began to decline; in addition, there are many switching devices and complex control. The series connection of multiple switching devices makes the driving scheme and auxiliary source design complex. Without Dedicated analog controller case enables circuit The implementation and cost have been pushed up, which also limits the application of the circuit to a certain extent. After that, the buck conversion circuit shown in Figure 5 received attention again. This circuit added a series capacitor to the traditional buck conversion circuit. Due to the existence of this capacitor, the duty cycle of the converter can be expanded. It also greatly reduces the voltage ripple in front of the output filter inductor and improves the working conditions of the filter inductor, allowing the converter to lower the switching frequency, reduce switching losses, and improve efficiency. At the same time, the circuit structure of the converter is also compared with the STC circuit. Be simple and reduce the design difficulty. This circuit is a relatively optimized solution for current non-isolated 48V to 12V applications. The only drawback to this circuit is the hard switching. Since the switching device is in a hard switching condition during operation, it limits the increase in the switching frequency of the converter to a certain extent, which limits the module from further improving the power density of the power module.

Therefore, it is necessary to provide a new type of non-isolated LLC resonant converter to solve some of the above problems existing in the prior art.

Contents of the invention

The purpose of the present invention is to provide a non-isolated LLC resonant converter to reduce control difficulty and cost.

In order to achieve the above object, the non-isolated LLC resonant converter of the present invention includes a first resonant bridge, a second resonant bridge, a resonant network, a rectifier bridge, a transformer, a load and an output capacitor. The transformer includes a first transformer inductor and A second transformer inductor. The first transformer inductor is connected in series with the resonant network to form a transformer resonant unit. The first end of the transformer resonant unit is connected to the first resonant bridge. The second end of the transformer resonant unit is Connected to the second resonant bridge, both ends of the second transformer inductor are connected to the whole The rectifier bridge is connected to the first resonant bridge, the second resonant bridge, one end of the load, and one end of the output capacitor, and the other end of the load and the other end of the output capacitor are connected. One end and the rectifier bridge are both connected to the negative pole of the power supply and grounded. The first resonant bridge is used to connect the first end of the transformer resonant unit with the positive pole of the power supply or one end of the load. The second resonant bridge The bridge is used to connect the second end of the transformer resonant unit with the positive pole of the power supply or one end of the load, and the rectifier bridge is used to connect both ends of the second transformer inductor with one end of the load and one end of the load respectively. The other end of the load is connected.

The beneficial effect of the non-isolated LLC resonant converter is that it includes a first resonant bridge, a second resonant bridge, a resonant network, a rectifier bridge, a transformer, a load and an output capacitor. The transformer includes a first transformer inductor and a second transformer inductor. , the circuit is simple, the control is simple and easy, and the cost is low.

Optionally, the first resonant bridge includes a first switch unit and a third switch unit, the first terminal of the first switch unit is connected to the positive pole of the power supply, and the second terminal of the first switch unit is connected to the third switch unit. The first end of the three switch units is connected, and the second end of the third switch unit is connected to one end of the load.

Optionally, both the first switch unit and the third switch unit are controllable switching devices.

Optionally, the second resonant bridge includes a second switch unit and a fourth switch unit, the first terminal of the second switch unit is connected to the positive pole of the power supply, and the second terminal of the second switch unit is connected to the third switch unit. The first end of the four switch units is connected, and the second end of the fourth switch unit is connected to one end of the load.

Optionally, both the second switch unit and the fourth switch unit are controllable switching devices.

Optionally, the rectifier bridge includes a fifth switch unit, a sixth switch unit, a seventh switch unit and an eighth switch unit, the first end of the fifth switch unit and the first end of the sixth switch unit Both are connected to one end of the load, the second end of the fifth switch unit is connected to the first end of the seventh switch unit, the second end of the sixth switch unit is connected to the eighth switch unit The first end is connected, and the second end of the seventh switch and the second end of the eighth switch are both connected to the other end of the load.

Optionally, the fifth switch unit, the sixth switch unit, the seventh switch unit and the eighth switch unit are all controllable switching devices or uncontrollable switching devices.

Optionally, the controllable switching device includes a metal oxide semiconductor field effect transistor, an insulated gate bipolar transistor, a gallium nitride transistor, a silicon carbide MOS transistor, and a first combined switching unit, and the first combined switching unit is a triode. combination with diodes.

Optionally, the uncontrollable switching device includes a diode and a second combined switch unit, and the second combined switch unit includes a diode and a metal oxide semiconductor field effect transistor, an insulated gate bipolar transistor, a gallium nitride transistor, and a silicon carbide Any combination of MOS tubes.

Optionally, the resonant network includes a first resonant inductor and a resonant capacitor, and the first resonant inductor, the resonant capacitor and the first transformer inductor are connected in series.

Optionally, the resonant network further includes a resistor, which is connected in series with the first resonant inductor, the resonant capacitor, and the first transformer inductor.

Optionally, the transformer further includes a second resonant inductor, the second resonant inductor is connected to The first transformer inductor or the second transformer inductor is connected in parallel.

Optionally, the first transformer inductor includes at least one sub-transformer inductor, and the sub-transformer inductors are connected in series.

Description of drawings

Figure 1 is a circuit schematic diagram of a non-isolated LLC resonant converter in some embodiments of the present invention;

Figure 2 is a schematic circuit diagram of a non-isolated LLC resonant converter in some embodiments of the present invention;

Figure 3 is a timing diagram of the non-isolated LLC resonant converter shown in Figure 1 in some embodiments of the present invention;

Figure 4 is a schematic circuit diagram of an STC resonant converter in the prior art;

FIG. 5 is a circuit schematic diagram of a buck conversion circuit in the prior art.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are part of the present invention. Examples, not all examples. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention. Unless otherwise Without definitions, the technical terms or scientific terms used here should have the usual meanings understood by those with ordinary skills in the field to which the present invention belongs. The use of "comprising" and similar words herein means that the elements or things appearing before the word include the elements or things listed after the word and their equivalents, without excluding other elements or things.

In order to solve the problems existing in the prior art, embodiments of the present invention provide a non-isolated LLC resonant converter. Referring to Figure 1, the non-isolated LLC resonant converter 100 includes a first resonant bridge 101, a second resonant bridge 102, a resonant network 103, a rectifier bridge 104, a transformer 105, a load Ro and an output capacitor Co. The transformer 105 includes a third a transformer inductor N1 and a second transformer inductor N2.

In some embodiments, the first transformer inductor is connected in series with the resonant network to form a transformer resonant unit, a first end of the transformer resonant unit is connected to the first resonant bridge, and a second end of the transformer resonant unit is connected to the first resonant bridge. Connected to the second resonant bridge, both ends of the second transformer inductor are connected to the rectifier bridge, and the rectifier bridge is connected to the first resonant bridge, the second resonant bridge, and one end of the load. , one end of the output capacitor is connected, the other end of the load, the other end of the output capacitor, and the rectifier bridge are all connected to the negative pole of the power supply and grounded, and the first resonant bridge is used to resonate the transformer The first end of the unit is connected to the positive pole of the power supply or one end of the load. The second resonant bridge is used to connect the second end of the transformer resonant unit to the positive pole of the power supply or one end of the load. The rectifier The bridge is used to connect two ends of the second transformer inductor to one end of the load and the other end of the load respectively.

In some embodiments, the first resonant bridge includes a first switch unit and a third switch unit. The first terminal of the first switch unit is connected to the positive pole of the power supply. The first switch unit has a The second end is connected to the first end of the third switching unit, and the second end of the third switching unit is connected to one end of the load.

In some embodiments, the second resonant bridge includes a second switch unit and a fourth switch unit, a first terminal of the second switch unit is connected to the positive pole of the power supply, and a second terminal of the second switch unit is connected to the The first end of the fourth switch unit is connected, and the second end of the fourth switch unit is connected to one end of the load.

In some embodiments, the rectifier bridge includes a fifth switching unit, a sixth switching unit, a seventh switching unit and an eighth switching unit, and the first end of the fifth switching unit and the first end of the sixth switching unit Both ends are connected to one end of the load, the second end of the fifth switching unit is connected to the first end of the seventh switching unit, the second end of the sixth switching unit is connected to the eighth switching unit The first end of the seventh switch and the second end of the eighth switch are both connected to the other end of the load.

In some embodiments, the first switching unit, the second switching unit, the third switching unit and the fourth switching unit are all controllable switching devices, and the fifth switching unit, the sixth switching unit The switch unit, the seventh switch unit and the eighth switch unit are all controllable switching devices or uncontrollable switching devices. Specifically, the controllable switching device includes a metal oxide semiconductor field effect transistor, an insulated gate bipolar transistor, a gallium nitride transistor, a silicon carbide MOS transistor, and a first combined switching unit. The first combined switching unit is a triode and a A combination of diodes. The uncontrollable switching device includes a diode and a second combined switch unit. The second combined switch unit includes a diode and a metal oxide semiconductor field effect transistor, an insulated gate bipolar transistor, a gallium nitride transistor, and a silicon carbide Any combination of MOS tubes.

Referring to Figure 1, the first switching unit is a first NMOS transistor S1, the second switching unit is a second NMOS transistor S2, the third switching unit is a third NMOS transistor S3, and the fourth switching unit is The fourth NMOS transistor S4, the fifth switching unit is the fifth NMOS transistor S5, the sixth switching unit is the sixth NMOS transistor S6, the seventh switching unit is the seventh NMOS transistor S7, and the eighth switch The unit is the eighth NMOS transistor S8.

Referring to Figure 1, the drain of the first NMOS transistor S1 is connected to the anode of the power supply Vin, the source of the first NMOS transistor S1 is connected to the drain of the third NMOS transistor S3, and the first transformer inductor N1 The opposite ends are connected, and the source of the third NMOS transistor S3 is connected to one end of the load Ro and one end of the output capacitor Co.

Referring to Figure 1, the drain of the second NMOS transistor S2 is connected to the anode of the power supply Vin, the source of the second NMOS is connected to the drain of the fourth NMOS transistor S4, and the drain of the fourth NMOS transistor S4 The source is connected to one end of the load Ro and one end of the output capacitor Co.

Referring to Figure 1, the drain of the fifth NMOS transistor S5 and the drain of the sixth NMOS transistor S6 are both connected to one end of the load Ro, and the source of the fifth NMOS transistor S5 is connected to the seventh NMOS transistor S6. The drain of the NMOS transistor S7 is connected to the opposite terminal of the second transformer inductor N2, and the source of the sixth NMOS transistor S6 is connected to the drain of the eighth NMOS transistor S8 and the opposite terminal of the second transformer inductor N2. The same terminal is connected, and the source of the seventh NMOS transistor S7 is connected to the source of the eighth NMOS transistor S8, the other end of the load Ro, the other end of the output capacitor Co, and the negative electrode of the power source Vin and grounded. .

Referring to Figure 1, the gate of the first NMOS transistor S1 is connected to the first control signal, and the The gate of the second NMOS transistor S2 is connected to the second control signal, the gate of the third NMOS transistor S3 is connected to the third control signal, the gate of the fourth NMOS transistor S4 is connected to the fourth control signal, and the gate of the fifth NMOS transistor S4 is connected to the fourth control signal. The gate of the NMOS transistor S5 is connected to the fifth control signal, the gate of the sixth NMOS transistor S6 is connected to the sixth control signal, the gate of the seventh NMOS transistor S7 is connected to the seventh control signal, and the eighth NMOS transistor S7 is connected to the seventh control signal. The gate of S8 is connected to the eighth control signal.

In some embodiments, the resonant network includes a first resonant inductor and a resonant capacitor, and the first resonant inductor, the resonant capacitor and the first transformer inductor are connected in series.

In some embodiments, the resonant network further includes a resistor, the resistor is connected in series with the first resonant inductor, the resonant capacitor, and the first transformer inductor.

In some embodiments, the transformer further includes a second resonant inductor, and the second resonant inductor is connected in parallel with the first transformer inductor or the second transformer inductor. The second resonant inductor is an independent inductor or a magnetizing inductor of the transformer.

In some embodiments, the first transformer inductor includes at least one sub-transformer inductor, and the sub-transformer inductors are connected in series.

Referring to Figure 1, the resonant network 103 includes a first resonant inductor Lr and a resonant capacitor Cr. One end of the first resonant inductor Lr is connected to the same end of the first transformer inductor N1. The first resonant inductor Lr has The other end is connected to one end of the resonant capacitor Cr, and the other end of the resonant capacitor Cr is connected to the source of the second NMOS transistor S2. The transformer also includes a second resonant inductor Lm. The second resonant inductor One end of Lm is connected to the same-name end of the first transformer inductor N1, and the other end of the second resonant inductor Lm is connected to the opposite-name end of the first transformer inductor N1.

Figure 2 is a schematic circuit diagram of a non-isolated LLC resonant converter in some embodiments of the present invention. Referring to Figure 2 and Figure 1, the difference between Figure 2 and Figure 1 is that the fifth NMOS transistor S5, the sixth NMOS transistor S6, the seventh NMOS transistor S7 and the eighth NMOS transistor S8 are all replaced. for the diode.

FIG. 3 is a timing diagram of the non-isolated LLC resonant converter shown in FIG. 1 in some embodiments of the present invention. Referring to Figure 3, _S1 represents the first control signal, _S2 represents the second control signal, _S3 represents the third control signal, _S4 represents the fourth control signal, _S5 represents the fifth control signal, and _S6 represents the sixth control signal. signal, S ₇ represents the seventh control signal, S ₈ represents the eighth control signal, I _Lr represents the current flowing through the first resonant inductor, I _Lm represents the current flowing through the second resonant inductor, I _Ro represents the current flowing through the load , V _S1 represents the voltage difference between the source and drain of the first NMOS transistor, V _S2 represents the voltage difference between the source and drain of the second NMOS transistor, V _S3 represents the source of the third NMOS transistor. The voltage difference between the electrode and the drain, V _S4 represents the voltage difference between the source and the drain of the fourth NMOS transistor, and S ₁ and S ₄ are the same, S ₂ and S ₄ are the same, S ₅ and S ₈ are the same, S ₆ and _S7 are the same, _VS2 and _VS3 are the same, _VS1 and _VS4 are the same.

Referring to Figures 1 and 3, at time t0 to t1, the first NMOS transistor S1, the fourth NMOS transistor S4, the fifth NMOS transistor S5 and the eighth NMOS transistor S8 are turned on. The second NMOS transistor S2, the third NMOS transistor S3, the sixth NMOS transistor S6 and the seventh NMOS transistor S7 are turned off. At time t0, due to the body diode of the first NMOS transistor S1 and the The body diode of the fourth NMOS transistor S4, the body diode of the fifth NMOS transistor S5, and the body diode of the eighth NMOS transistor S8 are turned on in advance, and at this time, the first NMOS transistor S1 and the fourth NMOS transistor S1 are turned on. The transistor S4, the fifth NMOS transistor S5 and the eighth NMOS transistor S8 can realize 0 voltage soft switching conduction. Pass; the ratio of the number of turns of the first transformer inductor N1 to the number of turns of the second transformer inductor N2 is n:1. Therefore, the voltage at both ends of the first resonant inductor Lr and the resonant capacitor Cr after they are connected in series is the resonant voltage, which is the difference between the power supply voltage V _in and (n+1) times the output voltage VoVo. Under the excitation of the resonant voltage, the current flowing through the first resonant inductor first resonates sinusoidally. After rising, the resonance decreases; the voltage across the second resonant inductor Lm is n times the output voltage VoVo. Under the excitation of the voltage across the second resonant inductor Lm, the current flowing through the second resonant inductor Lm linear rise.

Referring to Figures 1 and 3, at time t0 to t1, the current flowing through the first transformer inductor N1 is the difference between the current flowing through the first resonant inductor Lr and the current flowing through the second resonant inductor Lm, According to the coupling relationship between the first transformer inductor N1 and the second transformer inductor N2, the current flowing through the second transformer inductor N2 is n times the current flowing through the first transformer inductor N1, and is injected into the The total current of the output capacitor Co and the load Ro is the sum of the current flowing through the first transformer inductor N1 and the current flowing through the second transformer inductor N2; at this stage, the first NMOS transistor S1 source The voltage across the source and drain of the fourth NMOS transistor S4, the voltage across the source and drain of the fifth NMOS transistor S5 and the source and sum of the eighth NMOS transistor S8 The voltages across the drain are both 0V. The voltages across the source and drain of the second NMOS transistor S2 and the voltages across the source and drain of the third NMOS transistor S3 are both the power supply voltage V _in and the output voltage VoVo. The difference between the voltage across the source and drain of the sixth NMOS transistor S6 and the voltage across the source and drain of the seventh NMOS transistor S7 are both the output voltage VoVo.

Referring to Figure 1 and Figure 3, at time t1~Ts/2, at time t1, the first NMOS The tube S1, the fourth NMOS tube S4, the fifth NMOS tube S5 and the eighth NMOS tube S8 are turned off, and the current direction on the first resonant inductor Lr will not change suddenly. At this time, the first When the current direction on the resonant inductor Lr is positive, it will affect the junction capacitance of the first NMOS transistor S1, the junction capacitance of the fourth NMOS transistor S4, the junction capacitance of the fifth NMOS transistor S5 and the eighth NMOS transistor. The junction capacitance of tube S8 is charged, and at the same time, the junction capacitance of the second NMOS tube S2, the junction capacitance of the third NMOS tube S3, the junction capacitance of the sixth NMOS tube S6 and the junction capacitance of the seventh NMOS tube S7 are charged. Capacitor discharge; before time Ts/2, the voltage across the source and drain of the second NMOS transistor S2, the voltage across the source and drain of the third NMOS transistor S3, the source of the sixth NMOS transistor S6 After the voltages across the pole and drain of the seventh NMOS transistor S7 and the voltages across the source and drain of the seventh NMOS transistor S7 gradually drop to 0, the body diode of the second NMOS transistor S2 and the body diode of the third NMOS transistor S3 , the body diode of the sixth NMOS transistor S6 and the body diode of the seventh NMOS transistor S7 are conductive.

Referring to Figures 1 and 3, at time Ts/2 to time t2, at time Ts/2, due to the body diode of the second NMOS transistor S2, the body diode of the third NMOS transistor S3, the sixth NMOS transistor The body diode of S6 and the body diode of the seventh NMOS transistor S7 are turned on in advance. At this time, the second NMOS transistor S2, the third NMOS transistor S3, the sixth NMOS transistor S6 and the third NMOS transistor S7 are turned on. The seven NMOS transistors S7 can achieve zero voltage conduction; the voltage at both ends after the first resonant inductor Lr and the resonant capacitor Cr are connected in series is the resonant voltage, and the resonant voltage is the power supply voltage V _in and (n+1) times the output The difference in voltage VoVo, under the excitation of the resonant voltage, the current flowing through the first resonant inductor Lr first decreases with sinusoidal resonance and then rises with resonance; the voltage across the second resonant inductor Lm is negative n times the output voltage VoVo, under the excitation of the voltage across the second resonant inductor Lm, the current flowing through the second resonant inductor Lm decreases linearly.

Referring to Figures 1 and 3, at time Ts/2~t2, the current flowing through the first transformer inductor N1 is the current flowing through the first resonant inductor Lr and the current flowing through the second resonant inductor Lm. The difference; according to the coupling relationship between the first transformer inductor N1 and the second transformer inductor N2, the current flowing through the second transformer inductor N2 is n times the current flowing through the first transformer inductor N1 ; The total current injected into the output capacitor Co and the load Ro is the sum of the current flowing through the first transformer inductor N1 and the current flowing through the second transformer inductor N2; at this stage, the second The voltage across the source and drain of the NMOS transistor S2, the voltage across the source and drain of the third NMOS transistor S3, the voltage across the source and drain of the sixth NMOS transistor S6 and the voltage across the seventh NMOS transistor S6 The voltages across the source and drain of S7 are both 0. The voltages across the source and drain of the first NMOS transistor S1 and the voltages across the source and drain of the fourth NMOS transistor S4 are both the power supply voltage V _in The difference between the output voltage Vo and the voltage across the source and drain of the fifth NMOS transistor S5 and the voltage across the source and drain of the eighth NMOS transistor S8 are both the output voltage VoVo.

Referring to Figures 1 and 3, between time t2 and Ts, at time t2, the second NMOS transistor S2, the third NMOS transistor S3, the sixth NMOS transistor S6 and the seventh NMOS transistor S7 are turned off. , the current on the first resonant inductor Lr will not change suddenly. At this time, the direction of the current flowing through the first resonant inductor Lr is negative. For the junction capacitance of the second NMOS transistor S2 and the third NMOS The junction capacitance of tube S3, the junction capacitance of the sixth NMOS tube S6 and the junction capacitance of the seventh NMOSUAN are charged, and at the same time, the first The junction capacitance of the NMOS transistor S1, the junction capacitance of the fourth NMOS transistor S4, the junction capacitance of the fifth NMOS transistor S5 and the junction capacitance of the eighth NMOS transistor S8 are discharged; before time Ts, the first NMOS The voltage across the source and drain of tube S1, the voltage across the source and drain of the fourth NMOS tube S4, the voltage across the source and drain of the fifth NMOS tube S5 and the eighth NMOS tube S8 After the voltage across the source and drain gradually drops to 0, the body diode of the first NMOS transistor S1, the body diode of the fourth NMOS transistor S4, the body diode of the fifth NMOS transistor S5 and the body diode of the third NMOS transistor S5 The body diode of the eight NMOS transistor S8 is turned on. At time Ts, the first NMOS transistor S1, the fourth NMOS transistor S4, the fifth NMOS transistor S5 and the eighth NMOS transistor S8 are turned on. The NMOS transistor S4, the fifth NMOS transistor S5 and the eighth NMOS transistor S8 are turned on at 0 voltage, and the non-isolated LLC resonant converter enters the next switching cycle.

Referring to Figures 1 and 3, at times t0 to t1 and times Ts/2 to t2, the impedances of the first resonant inductor Lr, the resonant capacitor Cr and the second resonant inductor Lm change with the operating frequency. Therefore, By adjusting the operating frequency of the non-isolated LLC resonant converter, the adjustment function of the current injected into the load Ro and the output voltage Vo can be realized.

The first NMOS transistor and the fourth NMOS transistor are conductive in the same phase, the second NMOS transistor and the third NMOS transistor are conductive in the same phase, and the first NMOS transistor and the sixth NMOS transistor are in complementary conduction. , the second NMOS transistor and the fifth NMOS transistor are in complementary conduction. By controlling the on and off of the first NMOS transistor, the second NMOS transistor, the third NMOS transistor and the fourth NMOS transistor, the first resonant inductor and the resonant capacitor can be made to resonate. work, thereby utilizing resonant energy to achieve the first The 0-voltage switching of the NMOS tube, the second NMOS tube, the third NMOS tube and the fourth NMOS tube realizes soft switching and realizes high frequency and high efficiency of the power supply. At the same time, the circuit is simple, safe and reliable. Controls are simple and easy. The resonant network is used to form a resonant current, and the voltage and current coupling relationship between the first transformer inductor and the second transformer inductor of the transformer are used to change the voltage and reduce the current of the first transformer inductor and the second transformer inductor, and the input voltage to output voltage conversion. By adjusting the turns ratio of the first transformer inductor and the second transformer inductor, the output voltage can be adjusted. By adjusting the switching frequency of the non-isolated LLC resonant converter, the output voltage can be adjusted.

Although the embodiments of the present invention have been described in detail above, it will be obvious to those skilled in the art that various modifications and changes can be made to these embodiments. However, it should be understood that such modifications and changes are within the scope and spirit of the invention as described in the claims. Furthermore, the invention described herein is capable of other embodiments and of being practiced or carried out in various ways.

Claims

A non-isolated LLC resonant converter, characterized in that it includes a first resonant bridge, a second resonant bridge, a resonant network, a rectifier bridge, a transformer, a load and an output capacitor, and the transformer includes a first transformer inductor and a second transformer inductor. , the first transformer inductor is connected in series with the resonant network to form a transformer resonant unit, the first end of the transformer resonant unit is connected to the first resonant bridge, and the second end of the transformer resonant unit is connected to the third resonant bridge. Two resonant bridges are connected, both ends of the second transformer inductor are connected to the rectifier bridge, and the rectifier bridge is connected to the first resonant bridge, the second resonant bridge, one end of the load, and the output One end of the capacitor is connected, the other end of the load, the other end of the output capacitor, and the rectifier bridge are all connected to the negative pole of the power supply and grounded. The first resonant bridge is used to connect the first resonant end of the transformer resonant unit. The second resonant bridge is used to connect the second end of the transformer resonant unit to the positive pole of the power supply or one end of the load, and the rectifier bridge is used to connect the Two ends of the second transformer inductor are connected to one end of the load and the other end of the load respectively.
The non-isolated LLC resonant converter according to claim 1, wherein the first resonant bridge includes a first switching unit and a third switching unit, and the first terminal of the first switching unit is connected to the positive electrode of the power supply, The second end of the first switch unit is connected to the first end of the third switch unit, and the second end of the third switch unit is connected to one end of the load.
The non-isolated LLC resonant converter according to claim 2, wherein both the first switching unit and the third switching unit are controllable switching devices.
The non-isolated LLC resonant converter according to claim 1, characterized in that, The second resonant bridge includes a second switch unit and a fourth switch unit. The first terminal of the second switch unit is connected to the positive electrode of the power supply. The second terminal of the second switch unit is connected to the positive terminal of the fourth switch unit. The first end is connected, and the second end of the fourth switch unit is connected to one end of the load.
The non-isolated LLC resonant converter according to claim 4, wherein both the second switching unit and the fourth switching unit are controllable switching devices.
The non-isolated LLC resonant converter according to claim 1, wherein the rectifier bridge includes a fifth switching unit, a sixth switching unit, a seventh switching unit and an eighth switching unit, and the fifth switching unit The first end of the sixth switching unit and the first end of the sixth switching unit are both connected to one end of the load, the second end of the fifth switching unit is connected to the first end of the seventh switching unit, and the sixth The second end of the switch unit is connected to the first end of the eighth switch unit, and the second end of the seventh switch and the second end of the eighth switch are both connected to the other end of the load.
The non-isolated LLC resonant converter according to claim 6, wherein the fifth switch unit, the sixth switch unit, the seventh switch unit and the eighth switch unit are controllable switches. devices or uncontrollable switching devices.
The non-isolated LLC resonant converter according to claim 3, 5 or 7, characterized in that the controllable switching device includes a metal oxide semiconductor field effect transistor, an insulated gate bipolar transistor, a gallium nitride transistor, a silicon carbide MOS tube and a first combined switch unit, the first combined switch unit is a combination of a triode and a diode.
The non-isolated LLC resonant converter according to claim 7, characterized in that: The uncontrollable switching device includes a diode and a second combined switch unit. The second combined switch unit includes any of a diode and a metal oxide semiconductor field effect transistor, an insulated gate bipolar transistor, a gallium nitride transistor, or a silicon carbide MOS transistor. A combination of.
The non-isolated LLC resonant converter according to claim 1, wherein the resonant network includes a first resonant inductor and a resonant capacitor, and the first resonant inductor, the resonant capacitor and the first transformer inductor are connected in series. .
The non-isolated LLC resonant converter according to claim 10, wherein the resonant network further includes a resistor connected in series with the first resonant inductor, the resonant capacitor and the first transformer inductor.
The non-isolated LLC resonant converter according to claim 1, wherein the transformer further includes a second resonant inductor, and the second resonant inductor is connected in parallel with the first transformer inductor or the second transformer inductor.
The non-isolated LLC resonant converter according to claim 1, wherein the first transformer inductor includes at least one sub-transformer inductor, and the sub-transformer inductors are connected in series.