CN114938144A

CN114938144A - Non-isolated LLC resonant converter circuit

Info

Publication number: CN114938144A
Application number: CN202210641599.1A
Authority: CN
Inventors: 李培永; 杨鑫; 周远平; 乔宗标; 李斌
Original assignee: Shanghai Yinglian Electronic System Co ltd
Current assignee: Shanghai Yinglian Electronic System Co ltd
Priority date: 2022-06-08
Filing date: 2022-06-08
Publication date: 2022-08-23

Abstract

The invention discloses a non-isolated LLC resonant converter circuit, which utilizes the resonance principle of an inductor and a capacitor to realize soft switching of all switching devices, utilizes the coupling relation of a non-isolated transformer to realize resonant current multiplication and output voltage adjustment, effectively improves the conversion efficiency and power density, and reduces the cost. The converter circuit has simple structure, safety, reliability and easy control.

Description

Non-isolated LLC resonant converter circuit

Technical Field

The invention relates to the field of switching power supplies. The invention discloses a non-isolated LLC resonant converter circuit which can realize soft switching of all switching tubes.

Background

In recent years, due to the continuous and high-speed development of the data market, the demand for rack-mounted servers is promoted to be continuously increased, and the demand mainly comprises two aspects of deployment quantity and single-machine computing capacity. With the obvious problem of how to reduce initial capital expenditure and post-operational maintenance costs. Generally speaking, important expenses in the later operation cost mainly include energy consumption of the server itself and energy consumption of the environment maintenance system required for ensuring normal operation of the server itself and the accessory equipment, while the latter is restricted by the former, and the low energy consumption of the former also means that the construction cost and energy consumption of the latter can be reduced. Therefore, it is a comprehensive solution to use a high-efficiency power transmission architecture and reduce the energy consumption of the board card at the same time.

In order to reduce the electric energy loss and the cable cost in the power transmission process, a bus architecture which adopts 48V to supply power for a server board card is favored by the industry to replace the traditional 12V bus architecture; in the architecture, usually, a grid voltage is converted into a 48V direct current through an isolated AC-DC converter, and then the 48V direct current is transmitted to a board card, and then the 48V direct current is converted into 12V through the DC-DC converter inside the board card, and then power is supplied to each chipset, CPU, GPU or acceleration chips for various purposes through a Point-to-Point (Load) converter.

Therefore, in order to reduce the energy consumption and cost of the server, a high conversion efficiency and low cost solution of converting 48V into 12V is urgently needed in the field. There are three techniques currently gaining wide attention and application:

firstly, a 48V-to-12V module power supply scheme widely applied in the traditional communication field is continuously optimized, most of the power supplies adopt isolated half-bridge or full-bridge hard switch circuits, and a small part of the power supplies adopt LLC resonant converter circuits. In order to achieve higher conversion efficiency and power density, the number of layers and copper thickness of a PCB are generally increased, the design of an isolation transformer is optimized, and a power MOS tube with more excellent performance is adopted, so that the material cost of a product is continuously increased, the process difficulty is increased, and the development period is prolonged. While new products using such technologies continue to be launched, it has been difficult to continue to balance performance against price.

The other is the non-isolated, resonant converter scheme Switched Tank Converters (STC) developed and published by google, usa. The principle is that soft switching of all switching devices is realized through cascade connection of multi-stage resonant circuits, and the stress of the switching devices is effectively controlled in a mode of series connection and output voltage clamping. Thus, the efficiency of the converter is still effectively improved on the basis of using lower-cost devices. However, the converter is formed by cascading a plurality of stages of resonant circuits, and cannot adjust output voltage; the driving scheme and the auxiliary source circuit are complex in design due to the fact that the number of the switching devices is large, the control is complex, the switching devices are connected in series, and the like, and the overall cost of the circuit is increased.

And thirdly, the series capacitor BUCK circuit disclosed by Delta in 2004 patent US7230405B2 improves the working condition of the filter inductor by adding the series capacitor in the traditional BUCK circuit, so that the duty ratio of the converter can be expanded, the voltage pulse before the filter inductor is output is reduced, and the working condition of the filter inductor is improved. The converter can reduce the switching frequency, reduce the switching loss and improve the efficiency, thereby reducing the complexity. However, the switching devices of the circuit operate under hard switching conditions, which limits the increase of the switching frequency of the converter, and thus limits the further increase of the power density.

Disclosure of Invention

The invention provides a non-isolated LLC resonant converter circuit which is remarkably characterized in that a resonant capacitor and a resonant inductor form an LC resonant network, and soft switching of all switching devices is realized by utilizing the resonance work of LC; realizing resonance current multiplication by using a coupling relation of a non-isolation transformer; the output voltage is adjusted by adjusting the switching frequency and the turn ratio of the non-isolated transformer; because the soft switching of the switching device is realized, the high frequency and the high efficiency of the power supply can be realized; the circuit has simple structure, safety and reliability, and simple and easy control.

The circuit topology of the present invention is shown in fig. 1.

The invention provides a non-isolated LLC resonant converter circuit, which consists of a power supply Vin, two LC resonant networks, a TX transformer, a follow current tube, an output filter capacitor Co and an output load Ro, wherein: the two LC resonance networks are composed of an LC resonance network A and an LC resonance network B; the LC resonance network A consists of switching tubes S1 and S2, a resonance inductor Lr1 and a resonance capacitor Cr 1; the LC resonance network B consists of switching tubes S6 and S5, a resonance inductor Lr2 and a resonance capacitor Cr 2; the TX transformer consists of a winding TX _1, a winding TX _2, a winding TX _3, a winding TX _4 and an inductor Lm; the follow current pipe is composed of S3 and S4;

the left end of the switch tube S1 and the left end of the switch tube S6 are connected with the positive end of a power Vin; the right end of S1 is connected with the left end of S2 and the left end of Lr1, and the right end of Lr1 is connected with the left end of Cr 1; the right end of S6 is connected with the left end of S5 and the left end of Lr2, and the right end of Lr2 is connected with the left end of Cr 2; the right end of Cr1 is connected with the right end of S5, the upper end of Lm and the homonymous end of TX _3, and the heteronymous end of TX _3 is connected with the upper end of S4 and the homonymous end of TX _ 1; the right end of Cr2 is connected with the right end of S2, the lower end of Lm and the synonym end of TX _4, and the homonym end of TX _4 is connected with the upper end of S3 and the synonym end of TX _ 2; the TX _1 synonym terminal is connected with the TX _2 homonym terminal, the Co upper end and the Ro upper end, and the S3 lower end, the S4 lower end, the Co lower end, the Ro lower end and the power Vin negative end are connected with a reference ground;

controlling the on and off of S1, S2, S6 and S5, enabling Lr1 to work with Cr1 and Lr2 to work with Cr2 in a resonant mode to form resonant current, injecting the resonant current into one or more windings of the TX transformer, utilizing the coupling relation of the TX transformer to form induced current in the other winding or windings, enabling the current to simultaneously flow out from the different-name end of TX _1 and the same-name end of TX _2 through a freewheeling path provided by S3 or S4, realizing that the total current injected into an output filter capacitor Co and a load Ro is distributed in the TX _1 winding and the TX _2 winding according to a specific proportion, reducing the effective value of the current in the windings, and converting the input voltage into the output voltage.

Drawings

In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the embodiments and the drawings used in the description of the prior art. It is obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings can be derived from these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a converter circuit topology of an embodiment of the present invention;

FIG. 2 is a main operating waveform of an embodiment of the present invention;

fig. 3 is an STC resonant converter proposed by google;

FIG. 4 is a BUCK circuit with series capacitance as proposed by Delta;

FIG. 5 is a converter circuit topology diagram with zero turns for windings TX _3 and TX _4 according to an embodiment of the invention;

FIG. 6 is a converter circuit topology with the LC resonant network B removed according to an embodiment of the present invention;

FIG. 7 is a converter circuit topology with the LC resonant network B removed and the winding TX _3 having zero turns according to an embodiment of the invention;

FIG. 8 is a converter circuit topology with the LC resonant network B removed and zero turns in winding TX _4 according to an embodiment of the present invention;

fig. 9 is a converter circuit topology diagram with zero turns for windings TX _3 and TX _4 with the LC resonant network B removed according to an embodiment of the present invention.

Detailed Description

In order to clearly and completely describe the technical solutions in the embodiments of the present invention in the following with reference to the accompanying drawings in the embodiments of the present invention, it is obvious that the described embodiments are a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 1, the converter circuit of the present invention is composed of a power source Vin, two LC resonant networks, a TX transformer, a freewheeling tube, an output filter capacitor Co and an output load Ro, wherein: the two LC resonance networks are composed of an LC resonance network A and an LC resonance network B; the LC resonance network A consists of switching tubes S1 and S2, a resonance inductor Lr1 and a resonance capacitor Cr 1; the LC resonance network B is composed of switching tubes S6 and S5, a resonance inductor Lr2 and a resonance capacitor Cr 2; the TX transformer consists of a winding TX _1, a winding TX _2, a winding TX _3, a winding TX _4 and an inductor Lm; the follow current pipe is composed of S3 and S4;

as shown in fig. 2, the converter consists of 4 operating modes per cycle, which are described below in terms of different operating modes.

Mode 1: in a time period of t 0-t 1, at the time of t0, S1, S3 and S5 are turned on, S2, S4 and S6 are turned off, and as the body diodes of S1, S3 and S5 are turned on in advance, the turning on of S1, S3 and S5 can realize the turning on of a zero-voltage soft switch; the turn ratio of the TX transformer windings TX _1, TX _2, TX _3 and TX _4 is 1: 1: n: n, therefore, after Lr1 and Cr1 are connected in series, the voltage at two ends is equal to the difference between the input voltage Vin and (n + 2) -times output voltage, and under the excitation of the voltage, the current on Lr1 and Cr1 rises according to sinusoidal resonance and then falls in resonance; after Lr2 and Cr2 are connected in series, the voltage at two ends is equal to (2 n + 2) times of output voltage, and under the excitation of the voltage, the current on Lr2 and Cr2 falls according to sinusoidal resonance and then rises in resonance; the voltage at two ends of Lm is (2 n + 2) times of output voltage, and the inductive current rises linearly under the excitation of the voltage; the current injected into the same-name end of the winding TX _3 is the difference value of the Lr1 current, the Lr2 current and the Lm current; the current of the winding TX _3 rises from zero and then falls, and is injected into an output capacitor Co and a load Ro through TX _ 1; meanwhile, due to the coupling relation between the TX _1 and the TX _2, a TX _1 current which is multiplied by (3/2 x n + 1) is induced in the TX _2 winding, and the TX _2 current flows through S3 at the same time; the total current injected into the output capacitor Co and the load Ro is (3/2 × n + 2) times the current of the winding TX _ 3. In the stage, the voltage across the terminals S1, S3, and S5 is 0V, the voltage across the terminal S2 is the input voltage Vin plus n times the output voltage, the voltage across the terminal S4 is 2 times the output voltage, and the voltage across the terminal S6 is the input voltage Vin minus (n + 2) times the output voltage.

Mode 2: in a time period of t 1-Ts/2, at the time of t1, S1, S3 and S5 are turned off, the directions of currents on Lr1 and Lr2 cannot change suddenly, the current on Lr1 is positive, the current on Lr2 is negative, the S1 and S5 junction capacitors are charged, and meanwhile the S2 and S6 junction capacitors are discharged; before the time Ts/2, after the voltages on S2 and S6 are reduced to zero, the body diodes are conducted, and the voltages at the two ends of S2 and S6 are zero; the S3 body diode flows through the Lr1, the difference value of the Lr2 current and the Lm current, and is gradually reduced to zero.

Modality 3: in the time period of Ts/2-t 2, at the time of Ts/2, because the body diodes of S2, S4 and S6 are conducted in advance, the turning-on of S2, S4 and S6 can realize the turning-on of a zero-voltage soft switch; after Lr2 and Cr2 are connected in series, the voltage at two ends is equal to the difference value between the input voltage Vin and (n + 2) times of output voltage, and under the excitation of the voltage, the currents on Lr2 and Cr2 rise according to sinusoidal resonance and then fall through resonance; after the Lr1 and the Cr1 are connected in series, the voltage at two ends is equal to (2 n + 2) times of output voltage, and under the excitation of the voltage, the current on the Lr1 and the Cr1 falls according to sinusoidal resonance and then rises through resonance; the voltage at two ends of Lm is negative (2 n + 2) times of output voltage, and the inductive current is linearly reduced under the excitation of the voltage; the current injected into the different-name end of the winding TX _4 is the difference value of the current Lr2, the current Lr1 and the current Lm; the current of the winding TX _4 rises from zero and then falls, and is injected into an output capacitor Co and a load Ro through TX _ 2; meanwhile, due to the coupling relationship between TX _2 and TX _1, a (3/2 × n + 1) time of TX _2 current is induced in the TX _1 winding, and the TX _1 current flows through S4 at the same time; the total current injected into the output capacitor Co and the load Ro is (3/2 × n + 2) times the current of the winding TX _ 4. In this stage, the voltages at the two ends of S2, S4, and S6 are 0V, the voltage at the two ends of S5 is the sum of the input voltage Vin and n times of the output voltage, the voltage at the two ends of S3 is 2 times of the output voltage, and the voltage at the two ends of S1 is the sum of the input voltage Vin and (n + 2) times of the output voltage.

Modality 4: in a time period of t 2-Ts, at the time of t2, S2, S4 and S6 are turned off, the directions of currents on Lr2 and Lr1 cannot change suddenly, the current on Lr2 is positive, the current on Lr1 is negative, the S2 and S6 junction capacitors are charged, and meanwhile the S1 and S5 junction capacitors are discharged; before the time Ts, after the voltages on S1 and S5 are reduced to zero, the body diode is conducted, and the voltages at the two ends of S1 and S5 are zero; the S4 body diode flows through the Lr2, the difference value of the Lr1 current and the Lm current, and is gradually reduced to zero.

The impedance of the series resonance of the working

modes

1 and 3, namely Lr1 and Cr1, Lr2 and Cr2 of the converter circuit changes along with the working frequency, so that the functions of injecting load current and adjusting output voltage can be realized by adjusting the working frequency of the converter circuit.

From the above analysis of the operation principle, S1 is conducted in phase with S5, S2 is conducted in phase with S6, and S1, S5 are conducted complementarily with S2, S6; and controlling the on and off of S1, S2, S6 and S5, enabling Lr1 and Cr1 and Lr2 and Cr2 to work in a resonant mode, and realizing zero-voltage switching of S1, S2, S6 and S5 by utilizing resonant energy. The positions of Lr1 and Cr1 can be interchanged, and the positions of Lr2 and Cr2 can be interchanged, so that the functional realization of the circuit is not influenced.

The above analysis of the operating principle shows that the two LC resonant network parameters are completely consistent, or are inconsistent, or only one LC resonant network parameter exists, and the realization of the circuit function is not influenced.

From the above analysis of the operating principle, the turn ratio of the winding TX _1 to the winding TX _2 in the TX transformer is 1: 1; adjusting the turn ratio of the winding TX _3 and the winding TX _4 to the winding TX _1 and the winding TX _2 to realize the function of adjusting the output voltage; the number of turns of the winding TX _3 and the winding TX _4 in the TX transformer can be zero at the same time or zero at any one of the two.

From the above analysis of the working principle, the number of turns of the TX transformer winding TX _3 and the winding TX _4 can be adjusted, and the LC resonant network A, LC can be removed and retained by the resonant network B in any combination:

in the embodiment shown in fig. 5, the winding TX _3 and the winding TX _4 are zero-turn converter circuit topology;

as in the embodiment of fig. 6, the LC resonant network B is removed from the converter circuit topology;

in the embodiment shown in fig. 7, the LC resonant network B is removed, and the winding TX _3 is a converter circuit topology with zero turns;

in the embodiment shown in fig. 8, the LC resonant network B is removed, and the winding TX _4 is a converter circuit topology with zero turns;

in the embodiment shown in fig. 9, the LC resonant network B is removed, and the windings TX _3 and TX _4 are zero-turn converter circuit topology.

As can be seen from the above analysis of the operating principle, the resonant inductor and the resonant capacitor in the LC resonant network may be composed of a single resonant inductor and a single resonant capacitor, or may be composed of an impedance network composed of a plurality of inductors, capacitors, and resistors.

The above analysis of the operating principle shows that the positions of Lr1 and Cr1 are interchanged, and the positions of Lr2 and Cr2 are interchanged, so that the circuit function is not affected.

As can be seen from the above analysis of the operating principle, the inductor Lm may be an excitation inductor of the transformer TX or an independent inductor.

From the above analysis of the operation principle, the switching devices S1, S2, S6, and S5 in the converter circuit may be various controllable switching devices or combinations of switching devices, such as MOSFETs, IGBTs, diodes with transistors, GaN, and SiC MOSFETs, that can achieve resonant operation of the resonant network.

From the above analysis of the operation principle, the freewheeling tubes S3 and S4 in the present converter circuit can be various uncontrollable switching devices or combinations of devices, such as diodes, capable of realizing the freewheeling function.

From the above analysis of the operation principle, the freewheeling tubes S3 and S4 in the present converter circuit can be various controllable or uncontrollable switching devices or combinations of devices capable of realizing the freewheeling function, such as MOSFET, IGBT, GaN MOSFET, SiC MOSFET or diode and MOSFET, IGBT, GaN MOSFET, SiC MOSFET combinations.

The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. A non-isolated LLC resonant converter circuit is characterized by comprising a power source Vin, two LC resonant networks, a TX transformer, a follow current tube, an output filter capacitor Co and an output load Ro, wherein:

the two LC resonance networks are composed of an LC resonance network A and an LC resonance network B;

the LC resonance network A consists of switching tubes S1 and S2, a resonance inductor Lr1 and a resonance capacitor Cr 1;

the LC resonance network B is composed of switching tubes S6 and S5, a resonance inductor Lr2 and a resonance capacitor Cr 2;

the TX transformer consists of a winding TX _1, a winding TX _2, a winding TX _3, a winding TX _4 and an inductor Lm;

the follow current pipe is composed of S3 and S4;

in the above-described circuit, the first and second circuits,

the left end of the switch tube S1 and the left end of the switch tube S6 are connected with the positive end of a power Vin;

the right end of S1 is connected with the left end of S2 and the left end of Lr1, and the right end of Lr1 is connected with the left end of Cr 1;

the right end of S6 is connected with the left end of S5 and the left end of Lr2, and the right end of Lr2 is connected with the left end of Cr 2;

the right end of Cr1 is connected with the right end of S5, the upper end of Lm and the homonymous end of TX _3, and the heteronymous end of TX _3 is connected with the upper end of S4 and the homonymous end of TX _ 1;

the right end of Cr2 is connected with the right end of S2, the lower end of Lm and the synonym end of TX _4, and the homonym end of TX _4 is connected with the upper end of S3 and the synonym end of TX _ 2;

the TX _1 synonym terminal is connected with the TX _2 homonym terminal, the Co upper end and the Ro upper end, and the S3 lower end, the S4 lower end, the Co lower end, the Ro lower end and the power Vin negative end are connected with a reference ground;

2. A non-isolated LLC resonant converter circuit as claimed in claim 1, wherein: s1 and S5 are conducted in the same phase, S2 and S6 are conducted in the same phase, and S1, S5 and S2, S6 are conducted complementarily; and controlling the on and off of S1, S2, S6 and S5, enabling Lr1 and Cr1 and Lr2 and Cr2 to work in a resonant mode, and realizing zero-voltage switching of S1, S2, S6 and S5 by utilizing resonant energy.

3. A non-isolated LLC resonant converter circuit as claimed in claim 1, wherein: the function of output voltage regulation is realized by changing the switching frequency of S1, S2, S6 and S5.

4. A non-isolated LLC resonant converter circuit as claimed in claim 1, wherein said LC resonant network A, LC is a resonant network B, characterized in that: the positions of Lr1 and Cr1 can be interchanged, and the positions of Lr2 and Cr2 can be interchanged, so that the functional realization of the circuit is not influenced.

5. A non-isolated LLC resonant converter circuit as claimed in claim 1, wherein said LC resonant network A, LC resonant network B is formed by a single resonant inductor, a single resonant capacitor, or an impedance network formed by a plurality of inductors, capacitors, and resistors.

6. A non-isolated LLC resonant converter circuit as claimed in claim 1, wherein: the two LC resonance network parameters are completely consistent, or are inconsistent, or only one LC resonance network parameter exists, and the realization of the circuit function is not influenced.

7. The non-isolated LLC resonant converter circuit of claim 1, wherein said TX transformer is characterized by a winding TX _1 to winding TX _2 turns ratio of 1: and 1, adjusting the turn ratio of the windings TX _3 and TX _4 to the windings TX _1 and TX _2 to realize the function of adjusting the output voltage.

8. A non-isolated LLC resonant converter circuit according to claim 4, wherein said TX transformer is characterized in that two of the number of turns of winding TX _3 and TX _4 can be zero at the same time or either one can be zero.

9. A non-isolated LLC resonant converter circuit as claimed in claim 1, wherein: the number of turns of TX transformer winding TX _3, winding TX _4, and the removal and retention of LC resonant network A, LC resonant network B may be combined in any combination.

10. A non-isolated LLC resonant converter circuit as claimed in claim 1, wherein said inductance Lm, is characterized in that the inductance Lm can be the magnetizing inductance of the transformer TX or can be implemented by a separate inductance.

11. A non-isolated LLC resonant converter circuit as claimed in claim 1, wherein: the switching devices S1, S2, S6 and S5 in the converter circuit may be various controllable switching devices or combinations of switching devices, such as MOSFETs, IGBTs, diodes with transistors, GaN and SiC MOSFETs, that can implement the resonant operation of the resonant network.

12. A non-isolated LLC resonant converter circuit as claimed in claim 1, wherein: the freewheeling tubes S3, S4 may be various uncontrollable switching devices or combinations of devices, such as diodes, capable of freewheeling functions.

13. A non-isolated LLC resonant converter circuit as claimed in claim 1, wherein: the freewheeling tubes S3, S4 may be various controllable or non-controllable switching devices or combinations of devices that can perform the freewheeling function, such as MOSFETs, IGBTs, GaN MOSFETs, SiC MOSFETs or diodes and combinations of MOSFETs, IGBTs, GaN MOSFETs, SiC MOSFETs.