CN114938144A - A non-isolated LLC resonant converter circuit - Google Patents

Abstract

The invention discloses a non-isolated LLC resonant converter circuit. The converter utilizes the resonance principle of inductance and capacitance to realize soft switching of all switching devices, utilizes the non-isolated transformer coupling relationship to realize resonant current multiplication and output voltage adjustment, and effectively improves the conversion rate. efficiency and power density, and reduced costs. The converter circuit is simple in structure, safe, reliable and easy to control.

Description

A 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 switch tubes.

Background technique

In recent years, due to the continuous and rapid development of the data market, the demand for rack-mounted servers has been continuously increased, mainly including the number of deployments and the computing power of a single computer. What follows is the outstanding problem of how to reduce the initial capital expenditure and the later operation and maintenance cost. Generally speaking, the important expenditures in the later operation cost mainly include the energy consumption of the server itself and the energy consumption of the environment maintenance system required to ensure the normal operation of itself and its auxiliary equipment, while the latter is restricted by the former, and the low energy consumption of the former itself also means that The construction cost and energy consumption of the latter can be reduced. Therefore, using a high-efficiency power transmission architecture while reducing the energy consumption of the board is a comprehensive solution.

In order to reduce the power loss and cable cost in the power transmission process, the bus architecture that uses 48V to power the server board is favored by the industry instead of the traditional 12V bus architecture; this architecture usually converts the grid voltage through an isolated AC-DC converter first. It is 48V DC. After it is transmitted to the board, the 48V is converted to 12V with a DC-DC converter inside, and then the PoL-Point of Load converter is used for each chipset, CPU, GPU or various purposes. The accelerator chip is powered.

Therefore, in order to reduce the energy consumption and cost of the server, there is an urgent need for a high conversion efficiency, low-cost 48V to 12V solution in this field. There are three technologies that have been widely concerned and applied at present:

One is to continuously optimize the 48V to 12V module power supply scheme that is widely used in the traditional communication field. Most of these power supplies use isolated half-bridge or full-bridge hard switching circuits, and a few use LLC resonant converter circuits. In order to achieve higher conversion efficiency and power density, it is generally by increasing the number of layers and copper thickness of the PCB board, optimizing the design of the isolation transformer, and using power MOS transistors with better performance, but the result is constantly pushing up the cost of products. , Increase the difficulty of the process and lengthen the development cycle. Although there are still new products using this technology, it has been difficult to continue to develop a balance between performance and price.

The second is the Switched TankConverters (STC), a non-isolated, resonant converter solution developed and announced by Google in the United States. The principle is to realize the soft switching of all switching devices by cascading multi-stage resonant circuits, and the stress of the switching devices is effectively controlled by means of series connection and output voltage clamping. In this way, on the basis of using lower cost devices, the efficiency of the converter is still very effectively improved. However, this converter is composed of multi-stage resonant circuits in cascade, and the output voltage cannot be adjusted; many switching devices, complicated control, and multiple switching devices are connected in series, which makes the driving scheme and auxiliary source circuit design complicated, which pushes up the overall cost of the circuit.

The third is the series capacitor BUCK circuit disclosed by Delta in the 2004 patent US7230405B2. This circuit increases the series capacitor in the traditional BUCK circuit, so that the duty cycle of the converter can be expanded and the voltage ripple before the output filter inductor is reduced, improving the the working conditions of the filter inductor. Converters can reduce switching frequency, reduce switching losses, and improve efficiency, thereby reducing complexity. However, the switching devices of this circuit work under hard switching conditions, which limits the increase of the switching frequency of the converter, thereby limiting the further improvement of the power density.

The invention discloses a non-isolated LLC resonant converter circuit. The converter utilizes the resonance principle of inductance and capacitance to realize soft switching of all switching devices, utilizes the non-isolated transformer coupling relationship to realize resonant current multiplication and output voltage adjustment, and effectively improves the conversion rate. efficiency and power density, and reduced cost. The converter circuit is simple in structure, safe and reliable, and easy to control.

SUMMARY OF THE INVENTION

The invention proposes a non-isolated LLC resonant converter circuit, which is characterized in that a resonant capacitor and a resonant inductor form an LC resonant network, and the resonant operation of the LC is used to realize the soft switching of all switching devices; the non-isolated transformer coupling relationship is used to realize the The resonant current is multiplied; the output voltage can be adjusted by adjusting the switching frequency and the turns ratio of the non-isolated transformer; due to the realization of the soft switching of the switching device, the high frequency and high efficiency of the power supply can be realized; the circuit structure is simple, safe and reliable, and the control is simple and easy Row.

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

The present invention proposes a non-isolated LLC resonant converter circuit, which 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: two LC resonant networks The network consists of LC resonant network A and LC resonant network B; LC resonant network A consists of switch tubes S1, S2, resonant inductor Lr1, resonant capacitor Cr1; LC resonant network B consists of switch tubes S6, S5, resonant inductor Lr2, resonant capacitor Cr2 is composed; TX transformer is composed of winding TX_1, winding TX_2, winding TX_3, winding TX_4 and inductor Lm; freewheeling tube is composed of S3 and S4;

The left end of switch S1 and the left end of S6 are connected to the positive end of the power supply Vin; the right end of S1 is connected to the left end of S2 and the left end of Lr1, the right end of Lr1 is connected to the left end of Cr1; the right end of S6 is connected to the left end of S5 and the left end of Lr2, the right end of Lr2 is connected to the left end of Cr2; the right end of Cr1 is connected It is connected to the right end of S5, the upper end of Lm, and the same name of TX_3, and the synonymous end of TX_3 is connected to the upper end of S4 and the same name of TX_1; the right end of Cr2 is connected to the right end of S2, the lower end of Lm, and the same name of TX_4. The TX_1 synonym end is connected to the same name end of TX_2, the upper end of Co, and the upper end of Ro, and the lower end of S3, the lower end of S4, the lower end of Co, the lower end of Ro, and the negative end of power supply Vin are connected to the reference ground;

Control the turn-on and turn-off of S1, S2, S6, and S5, so that Lr1 and Cr1, Lr2 and Cr2 work in resonance to form a resonant current, which is injected into one or several windings of the TX transformer, and the coupling relationship of the TX transformer is used in another one or several windings. The induced current is formed in the winding, and the freewheeling path provided by S3 or S4 causes the current to flow out from the same name terminal of TX_1 and the same name terminal of TX_2 at the same time, so that the total current injected into the output filter capacitor Co and the load Ro is distributed in the TX_1 winding and The TX_2 winding reduces the rms value of the current in the winding and converts the input voltage to the output voltage.

Description of drawings

In order to illustrate the technical solutions of the present invention more clearly, the embodiments and the accompanying drawings used in the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can also be obtained from these drawings without creative effort.

1 is a topology diagram of a converter circuit according to an embodiment of the present invention;

Fig. 2 is the main working waveform of the embodiment of the present invention;

Figure 3 is the STC resonant converter proposed by Google;

Figure 4 is the BUCK circuit of the series capacitor proposed by Delta;

5 is a topology diagram of a converter circuit with zero turns of winding TX_3 and winding TX_4 according to an embodiment of the present invention;

Fig. 6 is the converter circuit topology diagram that the LC resonance network B of the embodiment of the present invention is removed;

7 is a topological diagram of a converter circuit with the LC resonant network B removed and the winding TX_3 being zero turns according to an embodiment of the present invention;

8 is a topology diagram of a converter circuit with the LC resonant network B removed and the winding TX_4 being zero turns according to an embodiment of the present invention;

9 is a topology diagram of a converter circuit in which the LC resonant network B is removed, and the winding TX_3 and the winding TX_4 are zero turns according to an embodiment of the present invention.

Detailed ways

In order to clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention, it is obvious that the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

As shown in Figure 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 resonant networks are composed of LC resonant networks. A and LC resonant network B are composed; LC resonant network A is composed of switch tubes S1, S2, resonant inductor Lr1, and resonant capacitor Cr1; LC resonant network B is composed of switch tubes S6, S5, resonant inductor Lr2, and resonant capacitor Cr2; TX transformer It is composed of winding TX_1, winding TX_2, winding TX_3, winding TX_4 and inductor Lm; the freewheeling tube is composed of S3 and S4;

The left end of switch S1 and the left end of S6 are connected to the positive end of the power supply Vin; the right end of S1 is connected to the left end of S2 and the left end of Lr1, the right end of Lr1 is connected to the left end of Cr1; the right end of S6 is connected to the left end of S5 and the left end of Lr2, the right end of Lr2 is connected to the left end of Cr2; the right end of Cr1 is connected It is connected to the right end of S5, the upper end of Lm, and the same name of TX_3, and the synonymous end of TX_3 is connected to the upper end of S4 and the same name of TX_1; the right end of Cr2 is connected to the right end of S2, the lower end of Lm, and the same name of TX_4. The TX_1 synonym end is connected to the same name end of TX_2, the upper end of Co, and the upper end of Ro, and the lower end of S3, the lower end of S4, the lower end of Co, the lower end of Ro, and the negative end of power supply Vin are connected to the reference ground;

As shown in Figure 2, each cycle of the converter consists of 4 working modes, which are described below according to different working modes.

Mode 1: During the period from t0 to t1, at time t0, S1, S3, and S5 are turned on, and S2, S4, and S6 are turned off. Since the body diodes of S1, S3, and S5 are turned on in advance, turning on S1, S3, and S5 at this time can Realize zero-voltage soft-switching turn-on; the turns ratio of TX transformer windings TX_1, TX_2, TX_3, TX_4 is 1:1:n:n, so after Lr1 and Cr1 are connected in series, the voltage at both ends is equal to the input voltage Vin and (n+2) times the output The difference of voltage, under this voltage excitation, the current on Lr1 and Cr1 rises according to sinusoidal resonance and then drops after resonance; after Lr2 and Cr2 are connected in series, the voltage at both ends is equal to (2n+2) times the output voltage, under this voltage excitation, Lr2 , The current on Cr2 drops according to sinusoidal resonance and then rises after resonance; the voltage across Lm is (2n+2) times the output voltage, and the inductor current rises linearly under the excitation of this voltage; the current injected into the end of the same name of the winding TX_3 is the Lr1 current and the Lr2 current, The difference of the Lm current; the current of the winding TX_3 rises from zero and then falls, and is injected into the output capacitor Co and the load Ro through TX_1; at the same time, due to the coupling relationship between TX_1 and TX_2, the TX_2 winding induces (3/2*n+1 ) times the TX_1 current, 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. At this stage, the voltage across S1, S3, and S5 is 0V, the voltage across S2 is the input voltage Vin plus n times the output voltage, the voltage across S4 is twice the output voltage, and the voltage across S6 is the input voltage Vin minus (n +2) times the output voltage.

Mode 2: During the period from t1 to Ts/2, at t1, S1, S3, and S5 are turned off, and the current directions on Lr1 and Lr2 will not change abruptly. At this time, the current on Lr1 is positive and the current on Lr2 is negative. , S5 junction capacitance is charged, and S2, S6 junction capacitance is discharged at the same time; before Ts/2 time, after the voltage on S2 and S6 drops to zero, the body diode is turned on, and the voltage across S2 and S6 is zero; S3 body diode current The difference between the Lr1 and Lr2 currents and the Lm current gradually decreases to zero.

Mode 3: During the period from Ts/2 to t2, at the time of Ts/2, since the body diodes of S2, S4, and S6 are turned on in advance, turning on S2, S4, and S6 at this time can realize zero-voltage soft-switching turn-on; Lr2 and Cr2 are connected in series The voltage at the rear end is equal to the difference between the input voltage Vin and (n+2) times the output voltage. Under this voltage excitation, the current on Lr2 and Cr2 rises according to sinusoidal resonance and then drops after resonance; after Lr1 and Cr1 are connected in series, the voltage at both ends is equal to (2n+2) times the output voltage, under the excitation of this voltage, the currents on Lr1 and Cr1 drop according to sinusoidal resonance and then rise after resonance; the voltage across Lm is negative (2n+2) times the output voltage, under this voltage excitation The inductor current decreases linearly; the current injected into the synonym end of the winding TX_4 is the difference between the Lr2 current, the Lr1 current, and the Lm current; the current of the winding TX_4 increases from zero and then decreases, and is injected into the output capacitor Co and the load Ro through TX_2; The coupling relationship with TX_1, the TX_1 winding induces (3/2*n+1) times the TX_2 current, 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 winding TX_4. At this stage, the voltage across S2, S4, and S6 is 0V, the voltage across S5 is the input voltage Vin plus n times the output voltage, the voltage across S3 is twice the output voltage, and the voltage across S1 is the input voltage Vin minus (n +2) times the output voltage.

Mode 4: During the period from t2 to Ts, at the time of t2, S2, S4, and S6 are turned off, and the current directions on Lr2 and Lr1 will not change abruptly. At this time, the current on Lr2 is positive, and the current on Lr1 is negative. The junction capacitance is charged, and the junction capacitance of S1 and S5 is discharged at the same time; before the time Ts, after the voltage on S1 and S5 drops to zero, the body diode is turned on, and the voltage across S1 and S5 is zero; the body diode of S4 flows through Lr2 and Lr1 The difference between the current and the Lm current gradually decreases to zero.

In the working mode 1 and mode 3 of the converter circuit, the impedance of the series resonance between Lr1 and Cr1, Lr2 and Cr2 changes with the working frequency. Therefore, by adjusting the working frequency of the converter circuit, the injected load current and output voltage can be realized. adjustment function.

It can be seen from the above working principle analysis that S1 and S5 conduct in-phase conduction, S2 and S6 conduct in-phase conduction, S1, S5 and S2, S6 complementarily conduct; Cr1, Lr2 and Cr2 work in resonance, and use the resonance energy to realize zero-voltage switching of S1, S2, S6, and S5. The positions of Lr1 and Cr1 are interchangeable, and the positions of Lr2 and Cr2 are interchangeable, which does not affect the realization of circuit functions.

It can be seen from the above working principle analysis that the parameters of the two LC resonant networks are completely consistent, or inconsistent, or there is only one, which does not affect the realization of the circuit function.

It can be seen from the above working principle analysis that the turns ratio of winding TX_1 and winding TX_2 in the TX transformer is 1:1; adjusting the turns ratio of winding TX_3, winding TX_4 and winding TX_1, winding TX_2 realizes the function of output voltage adjustment; The number of turns of winding TX_3 and winding TX_4 can be zero at the same time or any one of them can be zero.

It can be seen from the above working principle analysis that the adjustment of the number of turns of the TX transformer winding TX_3 and winding TX_4 and the removal and retention of the LC resonant network A and the LC resonant network B can be combined arbitrarily:

In the embodiment shown in FIG. 5, the topology diagram of the converter circuit with zero turns of winding TX_3 and winding TX_4;

In the embodiment shown in Figure 6, the topology diagram of the converter circuit removed by the LC resonant network B;

In the embodiment shown in FIG. 7 , the topology diagram of the converter circuit with the LC resonant network B removed and the winding TX_3 being zero turns;

In the embodiment shown in FIG. 8 , the topology diagram of the converter circuit with the LC resonant network B removed and the winding TX_4 being zero turns;

In the embodiment shown in FIG. 9 , the LC resonant network B is removed, and the winding TX_3 and the winding TX_4 are zero turns of the converter circuit topology diagram.

It can be seen from the above working principle analysis that the resonant inductance and resonant capacitor in the LC resonant network can be composed of a single resonant inductance, a single resonant capacitor, or an impedance network composed of multiple inductors, capacitors, and resistors.

It can be seen from the above working principle analysis that the positions of Lr1 and Cr1 are interchanged, and the positions of Lr2 and Cr2 are interchanged, which does not affect the realization of circuit functions.

It can be known from the above working principle analysis that the inductance Lm can be the magnetizing inductance of the transformer TX, or it can be an independent inductance.

From the above working principle analysis, it can be seen that the switching devices S1, S2, S6, S5 in the converter circuit can be a variety of controllable switching devices that can realize the resonant network to complete the resonant work, or a combination of switching devices, such as MOSFET, IGBT , triodes with diodes, GaN and SiC MOSFETs.

It can be seen from the above working principle analysis that the freewheeling tubes S3 and S4 in the converter circuit can be various uncontrollable switching devices or combinations of devices that can realize the freewheeling function, such as diodes.

It can be seen from the above working principle analysis that the freewheeling tubes S3 and S4 in the converter circuit can be a combination of various controllable or uncontrollable switching devices or devices that can realize the freewheeling function, such as MOSFET, IGBT, GaN MOSFET , SiCMOSFET or a combination of diode and MOSFET, IGBT, GaN MOSFET, SiC MOSFET.

The basic principles and main features of the present invention and the advantages of the present invention have been shown and described above. It should be understood by those skilled in the art that the present invention is not limited by the above-mentioned embodiments, and without departing from the spirit and scope of the present invention, the present invention will also have various changes and improvements, and these changes and improvements all fall into the protection requirements within the scope of the present invention. The claimed scope of the present invention is defined by the appended claims and their equivalents.

Claims (13)

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;

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.

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.

Images