LLC-buck combined wide gain dc-dc converter with bridge arm multiplexing

Abstract

The application discloses a kind of bridge arm multiplexing LLC-Buck combination type wide gain DC-DC converter, the converter is combined by main power circuit LLC converter and partial power circuit Buck converter, main power circuit LLC converter is by high-frequency transformer primary side H bridge circuit, and high-frequency transformer secondary side resonance network, voltage doubling rectifier circuit is constituted;Buck converter multiplexed LLC converter primary side H bridge circuit first bridge arm;LLC converter and Buck converter are connected in series at output side and work in wide gain boost mode;The application improves the power transmission efficiency of converter and system reliability, reduces the stress of secondary side power tube, improves the service life of power tube has the advantages, such as high degree of integration of converter, low cost, good practicality, and has wide application prospect in new energy field.

Description

Technical Field

[0001] This invention belongs to the field of DC-DC converter technology, specifically relating to an LLC-Buck combined wide-gain DC-DC converter with bridge arm multiplexing. Background Technology

[0002] In new energy power generation and storage systems, the voltages of photovoltaic cells, fuel cells, and system energy storage devices are very low. DC / DC converters are needed to boost these low voltages to a higher DC bus voltage to meet the requirements of subsequent inverters. While DAB converters offer wide-range voltage regulation, their efficiency is relatively low over a wide voltage and power range due to issues such as soft-switching range, circulating current power loss, and high turn-off current stress, making it difficult to meet the high efficiency requirements across the entire voltage domain. LLC resonant converters, with their zero-voltage turn-on and zero-current turn-off characteristics, offer high operating efficiency. However, when the system voltage is adjusted over a wide range, the switching frequency needs to be adjusted over a large range, posing challenges to circuit design and reducing operating efficiency. Therefore, LLC resonant converters are widely used in industry in DC-transformer (DCX) mode. To address this issue, researchers at the CPES Research Center in the United States first proposed a Sigma-type combined converter for data center power supply systems. In this converter, an LLC-DCX handles most of the power for high-efficiency transmission, while a Buck converter handles a smaller portion. PWM closed-loop control is used to achieve wide-range voltage regulation. This converter primarily achieves high-voltage input and low-voltage output, and has relatively low power density. A paper titled "Resonant Push–Pull Converter With Flyback Regulator for MHz High Step-Up Power Conversion" published in IEEE Transactions on Industrial Electronics, Volume 68, Issue 2, 2021, proposed a combined converter that uses a push-pull converter as the main power circuit and an active flyback converter as a partial power circuit, effectively reducing losses and stress. However, this converter suffers from low component density. Summary of the Invention

[0003] Based on the above-mentioned technical problems, the purpose of this invention is to provide an LLC-Buck combined wide-gain DC-DC converter with multiplexed bridge arms, which reduces power transistor stress, reduces the number of power transistors, and increases power density. It has many advantages such as reasonable structure, convenient implementation, good versatility, high system integration, and low cost.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A combined LLC-Buck wide-gain DC-DC converter with multiplexed bridge arms is characterized in that the converter is composed of a main power circuit LLC converter and a partial power circuit Buck converter. The LLC converter consists of a high-frequency transformer primary-side H-bridge circuit, a high-frequency transformer secondary-side resonant network, and a voltage doubler rectifier circuit. The Buck converter reuses the first bridge arm of the primary-side H-bridge circuit of the LLC converter. The LLC converter and the Buck converter are connected in series on the output side and operate in wide-gain boost mode.

[0006] The primary circuit of the main power circuit LLC converter includes the primary winding N of the transformer. P H-bridge circuit, DC voltage source U in and DC side capacitor C in An H-bridge circuit consisting of four power transistors: S1 (with junction capacitance), S2 (with junction capacitance), S3 (with junction capacitance), and S4 (with junction diodes in anti-parallel connection); primary winding N... P The same terminal is connected to the drain of the first power transistor S1 and the source of the third power transistor S3, and the primary winding N P The opposite-named terminal is connected to the drain of the second power transistor S2 and the source of the fourth power transistor S4. The sources of the first power transistor S1 and the second power transistor S2 are connected to the DC voltage source U. in and DC side capacitor C in The positive terminal of the transistor, and the drains of the third power transistor S3 and the fourth power transistor S4 are connected to the DC voltage source U. in and DC side capacitor C in The negative electrode;

[0007] The main power circuit LLC converter secondary circuit includes a high-frequency transformer secondary winding N. S Secondary resonant network, voltage doubler rectifier circuit, and filter capacitor C o1 Load R o Magnetizing inductance L m Resonant inductor L r Resonant capacitor C r The secondary resonant network is formed; the fifth power transistor S5, the sixth power transistor S6, the voltage multiplier capacitor C1, and the voltage multiplier capacitor C2 form a voltage multiplier rectifier circuit; the secondary winding N S The same name of the magnetizing inductor L m The left end and the resonant inductor L r The left end, secondary winding N S The excitation inductor L with different names is connected to the excitation inductor. m The right end and the resonant capacitor C r The negative terminal, resonant inductor L r The right end is connected to the drain of the fifth power transistor S5 and the source of the sixth power transistor S6, and the resonant capacitor C rThe positive terminal of the transistor S5 is connected to the negative terminal of voltage multiplier capacitor C1 and the positive terminal of voltage multiplier capacitor C2. The source terminal of the fifth power transistor S5 is connected to the positive terminal of voltage multiplier capacitor C1 and the filter capacitor C. o1 The positive electrode and the load R o At the top, the drain of the sixth power transistor S6 is connected to the negative terminal of the voltage multiplier capacitor C2 and the filter capacitor C. o1 The negative terminal and the output capacitor C o2 The positive electrode;

[0008] The partially powered Buck converter reuses the first bridge arm of the primary-side H-bridge circuit of the LLC converter, which is composed of the first power transistor S1 and the third power transistor S3; the partially powered Buck converter includes a step-down inductor L B and output capacitor C o2 Step-down inductor L B The left end is connected to the drain of the first power transistor S1 and the source of the third power transistor S3, and the step-down inductor L B The right end is connected to a filter capacitor C. o1 The negative terminal and output capacitor C o2 The positive terminal, output capacitor C o2 The negative terminal is connected to the drain of the third power transistor S3 and the fourth power transistor S4, and to the load R. o The lower part; the power circuit of the Buck converter forms a loop by connecting the midpoint of the first bridge arm and the end point of the second bridge arm, with filter capacitor C. o1 The negative terminal and the output capacitor C o2 The positive terminals are connected in series to form the output series;

[0009] Preferably, a bridge-arm multiplexed LLC-Buck combined wide-gain DC-DC converter is characterized in that all devices have a switching frequency of f. S In the primary-side H-bridge circuit of the LLC converter, the first power transistor S1 and the fourth power transistor S4 have a duty cycle of 0.5 and are driven by the same driver. The second power transistor S2 and the third power transistor S3 also have a duty cycle of 0.5 and are driven by the same driver. The first power transistor S1 and the third power transistor S3 are complementary in conduction, and the second power transistor S2 and the fourth power transistor S4 are complementary in conduction. The switching frequency is f. S for:

[0010]

[0011] Where L r For resonant inductance, C r It is a resonant capacitor;

[0012] The secondary side of the main power circuit LLC converter adopts a variable duty cycle modulation strategy. The fifth power transistor S5 and the sixth power transistor S6 are symmetrically driven. During the positive half-cycle, the conduction sequence is sixth power transistor S6, fifth power transistor S5, and sixth power transistor S6, and the conduction time of the sixth power transistor S6 is the same in both segments. Voltage regulation is achieved by changing the conduction time of the fifth power transistor S5 in the positive half-cycle. During the negative half-cycle, the conduction sequence is fifth power transistor S5, sixth power transistor S6, and fifth power transistor S5, and the conduction time of the fifth power transistor S5 is the same in both segments. Voltage regulation is achieved by changing the conduction time of the sixth power transistor S6 in the negative half-cycle.

[0013] Preferably, a bridge-arm multiplexed LLC-Buck combined wide-gain DC-DC converter is characterized in that the total gain M is equal to the gain M of the LLC converter. LLC and the gain M of the Buck converter Buck The result obtained by superposition is:

[0014]

[0015] Among them, M LLC The gain of the main power circuit LLC converter, M Buck Here, n represents the gain of the Buck converter in the partial power circuit, n is the turns ratio of the high-frequency transformer, and D is the gain of the Buck converter in the partial power circuit. S D is the ratio of the conduction time of the fifth power transistor S5 during the positive half-cycle to the total cycle time. P This represents the duty cycle of the primary-side switching transistor of the transformer.

[0016] Preferably, the fifth power transistor S5 and the sixth power transistor S6 are power field-effect transistors (MOSFETs).

[0017] Preferably, within one switching cycle, the operation of the invented converter can be divided into 12 modes, namely [t0~t1], [t1~t2], [t2~t3], [t3~t4], [t4~t5], [t5~t6], [t6~t7], [t7~t8], [t8~t9], [t9~t1 ...4~t5], [t5~t6], [t6~t7], [t7~t8], [t8~t9], [t9~t1], [t2~t3], [t4~t5], [t5~t6], [t6~t7], 10 ]、[t 10 ~t 11 ]、[t 11 ~t 12 ], where [t0~t6] represents the working state of the first half of the cycle, and [t7~t6] represents the working state of the second half of the cycle. 12 This indicates the second half of the operating cycle.

[0018] Mode 1 [t0~t1]:

[0019] At time t0, power transistors S2, S3, and S5 are turned off. The primary current of the high-frequency transformer flows through the junction capacitance C of power transistor S2. oss2 The junction capacitance C of power transistor S4oss4 Primary winding N P The junction capacitance C of power transistor S1 oss1 The junction capacitance C of power transistor S3 oss3 The secondary current of the high-frequency transformer flows through the secondary winding N. S Magnetizing inductance L m Resonant inductor L r Resonant capacitor C r The resonant cavity and the junction capacitance C of the power transistor S5 oss5 The junction capacitance C of power transistor S6 oss6 C1 voltage multiplier capacitor, C2 voltage multiplier capacitor, and finally C o1 After the filter capacitor, part of the power circuit current flows through the step-down inductor L. B Finally, through C o2 Output capacitor output;

[0020] During this stage, the energy refracted by the resonant cavity onto the primary side of the high-frequency transformer causes the parallel capacitor C of power transistors S1 and S4 to... oss1 C oss4 The voltage across U in When discharged to zero, the parallel capacitor C of power transistors S2 and S3... oss2 C oss3 The voltage at both ends is charged from zero to U. in The energy of the resonant cavity causes the parallel capacitor C of the power transistor S5 to... oss5 The voltage at both ends is charged from zero to U. o1 The parallel capacitor C of power transistor S6 oss6 The voltage across U o1 Discharge to zero. The soft-switching conditions for power transistors S1 and S3 are the same, as are those for power transistors S2 and S4. Therefore, only power transistors S1 and S4 will be analyzed.

[0021] At this time, the excitation current i m With resonant current i r All are less than 0. Therefore, the energy condition that power transistor S1 needs to satisfy to achieve zero-voltage turn-on is:

[0022]

[0023] In the formula t d This refers to the dead zone time.

[0024] The energy condition that power transistor S4 needs to meet to achieve zero-voltage turn-on is:

[0025]

[0026] The excitation current during this stage is:

[0027]

[0028] The expression for the output current of a Buck converter is:

[0029]

[0030] The excitation inductance at this stage satisfies:

[0031]

[0032] Mode 2 [t1~t2]:

[0033] At time t1, power transistors S1 and S4 are both turned on, and secondary power transistor S6 is conducting freewheeling. Due to the junction capacitance C... oss1 C oss4 C oss6 The function is that power transistors S1, S4, and S6 are at zero voltage, and the primary current of the high-frequency transformer flows through power transistor S1 and the primary winding N. P Power transistor S4; the secondary current of the high-frequency transformer flows through the secondary winding N. S Magnetizing inductance L m Resonant inductor L r Resonant capacitor C r The resonant cavity, power transistor S6, voltage multiplier capacitors C1 and C2 are constructed, and finally connected via C o1 Output after filtering capacitor; some power circuit current flows through buck inductor L B Finally, through C o2 Output capacitor output;

[0034] Mode 3 [t2~t3]:

[0035] At time t2, power transistor S6 is turned off, and the primary current of the high-frequency transformer flows through power transistor S1 and the primary winding N. P Power transistor S4; the secondary current of the high-frequency transformer flows through the secondary winding N. S Magnetizing inductance L m Resonant inductor L r Resonant capacitor C r The resonant cavity and the junction capacitance C of the power transistor S5 oss5 The junction capacitance C of power transistor S6 oss6 C1 voltage multiplier capacitor, C2 voltage multiplier capacitor, and finally C o1 Output after filtering capacitor; some power circuit current flows through buck inductor L B Finally, through C o2 Output capacitor output;

[0036] Mode 4 [t3~t4]:

[0037] At time t3, power transistor S5 is turned on. Due to the junction capacitance C... oss5 The function is that power transistor S5 is turned on with zero voltage; the primary current of the high-frequency transformer flows through power transistor S1 and the primary winding N. P Power transistor S4; the secondary current of the high-frequency transformer flows through the secondary winding N. S Magnetizing inductance L m Resonant inductor L r Resonant capacitor C r The resonant cavity, power transistor S5, voltage multiplier capacitors C1 and C2 are constructed, and finally connected via C o1 After the filter capacitor, part of the power circuit current flows through the step-down inductor L. B Finally, through C o2 Output capacitor output;

[0038] Mode 5 [t4~t5]:

[0039] At time t4, power transistor S5 is turned off, and the primary current of the high-frequency transformer flows through power transistor S1 and the primary winding N. P Power transistor S4; the secondary current of the high-frequency transformer flows through the secondary winding N. S Magnetizing inductance L m Resonant inductor L r Resonant capacitor C r The resonant cavity and the junction capacitance C of the power transistor S5 oss5 The junction capacitance C of power transistor S6 oss6 C1 voltage multiplier capacitor, C2 voltage multiplier capacitor, and finally C o1 After the filter capacitor, part of the power circuit current flows through the step-down inductor L. B Finally, through C o2 Output capacitor output;

[0040] Mode 6 [t5~t6]:

[0041] At time t5, power transistor S6 is turned on. Due to the junction capacitance C... oss6 The function is that power transistor S6 is turned on with zero voltage; the primary current of the high-frequency transformer flows through power transistor S1 and the primary winding N. P Power transistor S4; the secondary current of the high-frequency transformer flows through the secondary winding N. S Magnetizing inductance L m Resonant inductor L r Resonant capacitor C r The resonant cavity, power transistor S6, voltage multiplier capacitors C1 and C2 are constructed, and finally connected via C o1 After the filter capacitor, part of the power circuit current flows through the step-down inductor L. B Finally, through C o2 Output capacitor output.

[0042] Preferably, the switching timing of the LLC-Buck combined wide-gain DC-DC converter with bridge arm multiplexing is as follows:

[0043] ① After a certain dead time, power transistors S1, S4, and S6 are all turned on. (1-2D) s ) * T s / 4-t d After a certain time, the power transistor S6 will be turned off.

[0044] ② After a certain dead time, power transistor S5 is turned on, and power transistors S1, S4, and S5 are all turned on together. s* T s -t d Power transistor S5 will be turned off after a certain time.

[0045] ③ After a certain dead time, power transistor S6 is turned on. Power transistors S1, S4, and S6 are all turned on together. (1-2D) s ) * T s / 4-t d After a certain time, power transistors S1, S4, and S6 are turned off.

[0046] ④ After a certain dead time, power transistors S2, S3, and S5 are all turned on. (1-2D) s ) * T s / 4-t d Power transistor S5 will be turned off after a certain time.

[0047] ⑤ After a certain dead time, power transistor S6 is turned on. Power transistors S2, S3, and S6 are all turned on together. s* T s -t d After a certain time, the power transistor S6 will be turned off.

[0048] ⑥ After a certain dead time, power transistor S5 is turned on, and power transistors S2, S3, and S5 are all turned on together. (1-2D) s ) * T s / 4-t d Power transistor S5 will be turned off after a certain time.

[0049] ⑦ After a certain dead time, power transistors S1, S4, and S6 are turned on together, returning to the first process; this cycle continues.

[0050] Compared with the prior art, the present invention, employing the above technical solution, has the following beneficial effects:

[0051] 1. The LLC-Buck combined wide-gain DC-DC converter of the present invention, which uses multiplexed bridge arms, improves the power integration by multiplexing the first bridge arm composed of power transistors S1 and S3.

[0052] 2. The present invention provides an LLC-Buck combined wide-gain DC-DC converter with multiplexed bridge arms, which adopts a modulation strategy of varying the duty cycle of the secondary power transistors and uses the switching frequency of the devices as the resonant frequency, thereby improving the power transfer efficiency and system reliability of the converter.

[0053] 3. The present invention provides an LLC-Buck combined wide-gain DC-DC converter with bridge arm multiplexing, wherein the main power circuit LLC converter and part of the power circuit Buck converter are connected in series on the output side, which reduces the stress on the secondary power transistors and improves the service life of the power transistors.

[0054] 4. The LLC-Buck combined wide-gain DC-DC converter with bridge arm multiplexing provided by the present invention has a relatively simple structure, realizes soft switching operation of the converter power transistor, reduces the switching loss of the converter, and is conducive to the high-frequency operation of the converter and the reduction of device size. Attached Figure Description

[0055] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0056] Appendix Figure 1 The attached diagram shows the LLC-Buck combined wide-gain DC-DC converter circuit with bridge arm multiplexing of the present invention; Figure 2 This is a PWM switching timing diagram of the LLC-Buck combined wide-gain DC-DC converter with bridge arm multiplexing according to the present invention;

[0057] Appendix Figure 3 The attached figure shows the main waveforms of the LLC-Buck combined wide-gain DC-DC converter implementation circuit with bridge arm multiplexing according to the present invention.

[0058] Appendix Figure 4 This is a schematic diagram of the switching modes [t0~t1] of an embodiment of the LLC-Buck combined wide-gain DC-DC converter with bridge arm multiplexing according to the present invention.

[0059] Appendix Figure 5 This is a schematic diagram of the switching modes [t1~t2] of an embodiment of the LLC-Buck combined wide-gain DC-DC converter with bridge arm multiplexing according to the present invention.

[0060] Appendix Figure 6 This is a schematic diagram of the switching modes [t2~t3] of an embodiment of the LLC-Buck combined wide-gain DC-DC converter with bridge arm multiplexing according to the present invention.

[0061] Appendix Figure 7 This is a schematic diagram of the switching modes [t3~t4] of an embodiment of the LLC-Buck combined wide-gain DC-DC converter with bridge arm multiplexing according to the present invention.

[0062] Appendix Figure 8 This is a schematic diagram of the switching modes [t4~t5] of an embodiment of the LLC-Buck combined wide-gain DC-DC converter with bridge arm multiplexing according to the present invention.

[0063] Appendix Figure 9 This is a schematic diagram of the switching modes [t5~t6] of an embodiment of the LLC-Buck combined wide-gain DC-DC converter with bridge arm multiplexing according to the present invention.

[0064] Appendix Figure 10 This is a schematic diagram of the switching modes [t6~t7] of an embodiment of the LLC-Buck combined wide-gain DC-DC converter with bridge arm multiplexing according to the present invention.

[0065] Appendix Figure 11 This is a schematic diagram of the switching modes [t7~t8] of an embodiment of the LLC-Buck combined wide-gain DC-DC converter with bridge arm multiplexing according to the present invention.

[0066] Appendix Figure 12 This is a schematic diagram of the switching modes [t8~t9] of an embodiment of the LLC-Buck combined wide-gain DC-DC converter with bridge arm multiplexing according to the present invention.

[0067] Appendix Figure 13 The switching modes [t9~t] of the LLC-Buck combined wide-gain DC-DC converter embodiment of the present invention with bridge arm multiplexing 10 [Illustrative diagram attached.]

[0068] Appendix Figure 14 This is the switching mode of the LLC-Buck combined wide-gain DC-DC converter embodiment of the present invention with multiplexed bridge arms [t]. 10 ~t 11 [Illustrative diagram attached.]

[0069] Appendix Figure 15 This is the switching mode of the LLC-Buck combined wide-gain DC-DC converter embodiment of the present invention with multiplexed bridge arms [t]. 11 ~t 12 [Illustrative diagram attached.]

[0070] Appendix Figure 16 The excitation current i provided by the input voltage of 28V in this embodiment of the invention is m Resonant current i r Output voltage U o The experimental waveform.

[0071] Appendix Figure 17 The excitation current i provided by the input voltage of 30V in this embodiment of the invention is... m Resonant current i r Output voltage U o The experimental waveform. Specific implementation methods

[0072] The technology of the present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0073] Appendix Figure 1 and attached Figure 2 The attached diagram shows a bridge arm multiplexed LLC-Buck combined wide-gain DC-DC converter circuit proposed in this invention, along with its corresponding switching timing diagram.

[0074] As attached Figure 1 As shown, an embodiment of the present invention discloses a bridge-arm multiplexed LLC-Buck combined wide-gain DC-DC converter, which consists of one DC voltage source, six power transistors, one high-frequency transformer, four capacitors, one inductor, one LC resonant cavity, and a load. Wherein, S1 to S6 are the six power transistors, C... oss1 It is the junction capacitance of S1, C oss2 It is the junction capacitance of S2, C oss3 It is the junction capacitance of S3, C oss4 It is the junction capacitance of S4, C oss5 It is the junction capacitance of S5, C oss6 D1 is the junction capacitance of S6; D2 is the body diode of S1, D3 is the body diode of S3, D4 is the body diode of S4, D5 is the body diode of S5, and D6 is the body diode of S6; power transistors S5 and S6, voltage multiplier capacitors C1 and C2 form a voltage multiplier rectifier circuit; L m It is the magnetizing inductor, L r It is a resonant inductor, C r It is a resonant capacitor, C o1 It is a filter capacitor, L B It is a step-down inductor, C o2 It is the output capacitor, R o It is the load; where U in DC power supply voltage; U ab : This refers to the voltage on the primary side of the transformer; U cd :L m Lr C r The voltage of the resonant cavity; i p : The current flowing through the primary side of the transformer; i m : The current flows through the magnetizing inductor L m The current; i r : Flow through resonant inductor L r The current; U Cr Resonant capacitor C r Voltage on; U o1 : Filter capacitor C o1 Voltage on; U o2 : Filter capacitor C o2 Voltage on; U o Output voltage.

[0075] This bridge arm reuses an LLC-Buck combined wide-gain DC-DC converter with additional... Figure 2 The switching sequence shown is as follows:

[0076] 1) After a certain dead time, power transistors S1, S4, and S6 are all turned on. (1-2D) s ) * T s / 4-t d After a certain time, power transistor S6 is turned off, while power transistors S1 and S4 remain on.

[0077] 2) After a certain dead time, power transistor S5 is turned on, and in D... s* T s -t d During this period, power transistor S5 is turned off, while power transistors S1 and S4 remain on during the continuous conduction period.

[0078] 3) After a certain dead time, power transistor S6 is turned on, and in (1-2D) s ) * T s / 4-t d During this period, power transistors S1, S4, and S6 are turned off.

[0079] 4) After a certain dead time, power transistors S2, S3, and S5 are turned on. (1-2D) s ) * T s / 4-t d After a certain time, power transistor S5 is turned off, while power transistors S2 and S3 remain on.

[0080] 5) After a certain dead time, power transistor S6 is turned on, and in D... s* T s -td During this period, power transistor S6 is turned off, while power transistors S2 and S3 remain on during the continuous conduction period.

[0081] 6) After a certain dead time, power transistor S5 is turned on, and in (1-2D) s ) * T s / 4-t d During this period, power transistors S2, S3, and S5 are turned off.

[0082] 7) After a certain dead time, power transistors S1, S4, and S6 are turned on, returning to process 1); this cycle continues.

[0083] The following is an appendix to the present invention. Figure 1 Based on the LLC-Buck combined wide-gain DC-DC converter with bridge arm multiplexing, combined with... Figure 2 The switching sequence used is attached. Figure 4 ~Attached Figure 9 This paper will explain the specific working principle of the DC-DC converter of the present invention.

[0084] From the appendix Figure 2 It can be seen that within one switching cycle, the operation of the invented converter can be divided into 12 modes, namely [t0~t1], [t1~t2], [t2~t3], [t3~t4], [t4~t5], [t5~t6], [t6~t7], [t7~t8], [t8~t9], [t9~t1 ...4~t5], [t5~t6], [t6~t7], [t7~t8], [t8~t9], [t9~t1], [t2~t3], [t4~t5], [t5~t6], [t6~t 10 ]、[t 10 ~t 11 ]、[t 11 ~t 12 ], where [t0~t6] represents the working state of the first half of the cycle, and [t7~t6] represents the working state of the second half of the cycle. 12 This represents the second half of the operating cycle. The working principles of each mode are analyzed in detail below.

[0085] For ease of analysis, let's make the following general assumptions: ① Power transistors S1 to S6 are all ideal devices with zero on-state voltage drop; ② The junction capacitances of the six power transistors are C... oss1 ~C oss6 The values ​​are equal, both equal to C. oss ③ The magnetizing inductance of the high-frequency transformer T is sufficiently large, the magnetizing current is negligible, and the turns ratio of the secondary and primary windings is n = N. P / N s Leakage inductance is negligible; ④ Filter capacitor C o1 It is large enough that its voltage is equivalent to a constant voltage source during switching transients;

[0086] 1. Mode 1 [t0~t1], as shown in the appendix Figure 4As shown.

[0087] At time t0, power transistors S2, S3, and S5 are turned off. The primary current of the high-frequency transformer flows through the junction capacitance C of power transistor S2. oss2 The junction capacitance C of power transistor S4 oss4 Primary winding N P The junction capacitance C of power transistor S1 oss1 The junction capacitance C of power transistor S3 oss3 The secondary current of the high-frequency transformer flows through the secondary winding N. S Magnetizing inductance L m Resonant inductor L r Resonant capacitor C r The resonant cavity and the junction capacitance C of the power transistor S5 oss5 The junction capacitance C of power transistor S6 oss6 C1 voltage multiplier capacitor, C2 voltage multiplier capacitor, and finally C o1 The output is after the filter capacitor. Part of the power circuit current flows through the step-down inductor L. B Finally, through C o2 Output capacitor output.

[0088] During this stage, the energy refracted by the resonant cavity onto the primary side of the high-frequency transformer causes the parallel capacitor C of power transistors S1 and S4 to... oss1 C oss4 The voltage across U in When discharged to zero, the parallel capacitor C of power transistors S2 and S3... oss2 C oss3 The voltage at both ends is charged from zero to U. in The energy of the resonant cavity causes the parallel capacitor C of the power transistor S5 to... oss5 The voltage at both ends is charged from zero to U. o1 The parallel capacitor C of power transistor S6 oss6 The voltage across U o1 Discharge to zero. The soft-switching conditions for power transistors S1 and S3 are the same, as are those for power transistors S2 and S4. Therefore, only power transistors S1 and S4 will be analyzed.

[0089] The energy condition that power transistor S1 needs to meet to achieve zero-voltage turn-on is:

[0090]

[0091] In the formula t d This refers to the dead zone time.

[0092] The energy condition that power transistor S4 needs to meet to achieve zero-voltage turn-on is:

[0093]

[0094] The excitation current during this stage is:

[0095]

[0096] The expression for the output current of a Buck converter is:

[0097]

[0098] The excitation inductance at this stage satisfies:

[0099]

[0100] 2. Mode 2 [t1~t2], as shown in the appendix. Figure 5 As shown.

[0101] At time t1, power transistors S1 and S4 are both turned on, and secondary power transistor S6 is conducting freewheeling. Due to the junction capacitance C... oss1 C oss4 C oss6 The function of this is to ensure that power transistors S1, S4, and S6 are turned on at zero voltage. The primary current of the high-frequency transformer flows through power transistor S1 and the primary winding N. P Power transistor S4; the secondary current of the high-frequency transformer flows through the secondary winding N. S Magnetizing inductance L m Resonant inductor L r Resonant capacitor C r The resonant cavity, power transistor S6, voltage multiplier capacitors C1 and C2 are constructed, and finally connected via C o1 The output is after the filter capacitor. Part of the power circuit current flows through the step-down inductor L. B Finally, through C o2 Output capacitor output.

[0102] 3. Mode 3 [t2~t3], as shown in the appendix. Figure 6 As shown.

[0103] At time t2, power transistor S6 is turned off, and the primary current of the high-frequency transformer flows through power transistor S1 and the primary winding N. P Power transistor S4; the secondary current of the high-frequency transformer flows through the secondary winding N. S Magnetizing inductance L m Resonant inductor L r Resonant capacitor C r The resonant cavity and the junction capacitance C of the power transistor S5 oss5 The junction capacitance C of power transistor S6 oss6 C1 voltage multiplier capacitor, C2 voltage multiplier capacitor, and finally C o1 The output is after the filter capacitor. Part of the power circuit current flows through the step-down inductor L. BFinally, through C o2 Output capacitor output.

[0104] 4. Mode 4 [t3~t4], as shown in the appendix. Figure 7 As shown.

[0105] At time t3, power transistor S5 is turned on. Due to the junction capacitance C... oss5 The function is that power transistor S5 is turned on with zero voltage; the primary current of the high-frequency transformer flows through power transistor S1 and the primary winding N. P Power transistor S4; the secondary current of the high-frequency transformer flows through the secondary winding N. S Magnetizing inductance L m Resonant inductor L r Resonant capacitor C r The resonant cavity, power transistor S5, voltage multiplier capacitors C1 and C2 are constructed, and finally connected via C o1 The output is after the filter capacitor. Part of the power circuit current flows through the step-down inductor L. B Finally, through C o2 Output capacitor output.

[0106] 5. Mode 5 [t4~t5], as shown in the appendix. Figure 8 As shown.

[0107] At time t4, power transistor S5 is turned off, and the primary current of the high-frequency transformer flows through power transistor S1 and the primary winding N. P Power transistor S4; the secondary current of the high-frequency transformer flows through the secondary winding N. S Magnetizing inductance L m Resonant inductor L r Resonant capacitor C r The resonant cavity and the junction capacitance C of the power transistor S5 oss5 The junction capacitance C of power transistor S6 oss6 C1 voltage multiplier capacitor, C2 voltage multiplier capacitor, and finally C o1 The output is after the filter capacitor. Part of the power circuit current flows through the step-down inductor L. B Finally, through C o2 Output capacitor output.

[0108] 6. Mode 6 [t5~t6], as shown in the appendix. Figure 9 As shown.

[0109] At time t5, power transistor S6 is turned on. Due to the junction capacitance C... oss6 The function is that power transistor S6 is turned on with zero voltage; the primary current of the high-frequency transformer flows through power transistor S1 and the primary winding N. P Power transistor S4; the secondary current of the high-frequency transformer flows through the secondary winding N. S Magnetizing inductance L m Resonant inductor L rResonant capacitor C r The resonant cavity, power transistor S6, voltage multiplier capacitors C1 and C2 are constructed, and finally connected via C o1 The output is after the filter capacitor. Part of the power circuit current flows through the step-down inductor L. B Finally, through C o2 Output capacitor output.

[0110] Appendix Figure 16 It can be seen that, at the input voltage U in =28V, load 800W, dead time t d =0.02, turns ratio n = 1:5.75, resonant inductance L r =34.5μH, magnetizing inductance L m =388μH, resonant capacitance C r =78.93nF, primary side duty cycle D P =0.5, secondary side duty cycle D S =0.40, switching frequency f S =96.4kHz, excitation current i m Resonant current i r Output voltage U o The experimental waveform.

[0111] Appendix Figure 17 It can be seen that, at the input voltage U in =30V, load 800W, dead time t d =0.02, turns ratio n = 1:5.75, resonant inductance L r =34.5μH, magnetizing inductance L m =388μH, resonant capacitance C r =78.93nF, primary side duty cycle D P =0.5, secondary side duty cycle D S =0.37, switching frequency f S =96.4kHz, excitation current i m Resonant current i r Output voltage U o The experimental waveform.

Claims

1. A bridge-arm multiplexed LLC-Buck combined wide-gain DC-DC converter, characterized in that, The converter is composed of a main power circuit LLC converter and a partial power circuit Buck converter. The main power circuit LLC converter consists of a high-frequency transformer primary-side H-bridge circuit, a high-frequency transformer secondary-side resonant network, and a voltage doubler rectifier circuit. The Buck converter reuses the first bridge arm of the primary-side H-bridge circuit of the LLC converter. The LLC converter and the Buck converter are connected in series on the output side and operate in wide gain boost mode. The primary circuit of the main power circuit LLC converter includes the primary winding N of the transformer. P H-bridge circuit, DC voltage source U in and DC side capacitor C in An H-bridge circuit consisting of four power transistors: S1 (with junction capacitance), S2 (with junction capacitance), S3 (with junction capacitance), and S4 (with junction diodes in anti-parallel connection); primary winding N... P The same terminal is connected to the drain of the first power transistor S1 and the source of the third power transistor S3, and the primary winding N P The opposite-named terminal is connected to the drain of the second power transistor S2 and the source of the fourth power transistor S4. The sources of the first power transistor S1 and the second power transistor S2 are connected to the DC voltage source U. in and DC side capacitor C in The positive terminal of the transistor, and the drains of the third power transistor S3 and the fourth power transistor S4 are connected to the DC voltage source U. in and DC side capacitor C in The negative electrode; The main power circuit LLC converter secondary circuit includes the high-frequency transformer secondary winding N. S Secondary resonant network, voltage doubler rectifier circuit, and filter capacitor C o1 Load R o Magnetizing inductance L m Resonant inductor L r Resonant capacitor C r The secondary resonant network is formed; the fifth power transistor S5, the sixth power transistor S6, the voltage multiplier capacitor C1, and the voltage multiplier capacitor C2 form a voltage multiplier rectifier circuit; the secondary winding N S The same name of the magnetizing inductor L m The left end and the resonant inductor L r The left end, secondary winding N S The opposite-named terminal of the magnetizing inductor L m The right end and the resonant capacitor C r The negative terminal, resonant inductor L r The right end is connected to the drain of the fifth power transistor S5 and the source of the sixth power transistor S6, and the resonant capacitor C r The positive terminal of the transistor S5 is connected to the negative terminal of voltage multiplier capacitor C1 and the positive terminal of voltage multiplier capacitor C2. The source terminal of the fifth power transistor S5 is connected to the positive terminal of voltage multiplier capacitor C1 and the filter capacitor C. o1 The positive electrode and the load R o At the top, the drain of the sixth power transistor S6 is connected to the negative terminal of the voltage multiplier capacitor C2 and the filter capacitor C. o1 The negative terminal and the output capacitor C o2 The positive electrode; The partially powered Buck converter reuses the first bridge arm of the primary-side H-bridge circuit of the LLC converter, which is composed of the first power transistor S1 and the third power transistor S3; the partially powered Buck converter includes a step-down inductor L. B and output capacitor C o2 Step-down inductor L B The left end is connected to the drain of the first power transistor S1 and the source of the third power transistor S3, and the step-down inductor L B The right end is connected to a filter capacitor C. o1 The negative terminal and output capacitor C o2 The positive terminal, output capacitor C o2 The negative terminal is connected to the drain of the third power transistor S3 and the fourth power transistor S4, and the load R. o The lower part; the power circuit of the Buck converter forms a loop by connecting the midpoint of the first bridge arm and the end point of the second bridge arm, with filter capacitor C. o1 The negative terminal and the output capacitor C o2 The positive terminals are connected to form an output series connection.

2. The LLC-Buck combined wide-gain DC-DC converter with bridge arm multiplexing according to claim 1, characterized in that, The switching frequency of all devices is f. S In the primary-side H-bridge circuit of the LLC converter, the first power transistor S1 and the fourth power transistor S4 have a duty cycle of 0.5 and are driven by the same driver. The second power transistor S2 and the third power transistor S3 also have a duty cycle of 0.5 and are driven by the same driver. The first power transistor S1 and the third power transistor S3 are complementary in conduction, and the second power transistor S2 and the fourth power transistor S4 are complementary in conduction. The switching frequency is f. S for: Where L r For resonant inductance, C r It is a resonant capacitor; The secondary side of the main power circuit LLC converter adopts a variable duty cycle modulation strategy. The fifth power transistor S5 and the sixth power transistor S6 are symmetrically driven. During the positive half-cycle, the conduction sequence is sixth power transistor S6, fifth power transistor S5, and sixth power transistor S6. The conduction time of the sixth power transistor S6 is the same in both segments of the positive half-cycle. During the negative half-cycle, the conduction sequence is fifth power transistor S5, sixth power transistor S6, and fifth power transistor S5. The conduction time of the fifth power transistor S5 is the same in both segments of the negative half-cycle. The conduction time of S5 in the positive half-cycle is the same as that of S6 in the negative half-cycle. Voltage regulation is achieved by changing the conduction time of the fifth power transistor S5 in the positive half-cycle.

3. The LLC-Buck combined wide-gain DC-DC converter with bridge arm multiplexing according to claim 1, characterized in that, The total gain M is the gain M of the LLC converter. LLC and the gain M of the Buck converter Buck The result obtained by superposition is: Among them, M LLC The gain of the main power circuit LLC converter, M Buck Here, n is the gain of the Buck converter in the partial power circuit, n is the turns ratio of the high-frequency transformer, D2 is the ratio of the conduction time of the fifth power transistor S5 in the positive half-cycle to the total cycle time, and D1 is the duty cycle of the primary-side switch of the transformer.

4. The LLC-Buck combined wide-gain DC-DC converter with bridge arm multiplexing according to claim 1, characterized in that, The fifth power transistor S5 and the sixth power transistor S6 are power field-effect transistors (MOSFETs).

5. A bridge-arm multiplexed LLC-Buck combined wide-gain DC-DC converter according to claim 1, characterized in that, Within one switching cycle, the invented converter operates in 12 modes: [t0~t1], [t1~t2], [t2~t3], [t3~t4], [t4~t5], [t5~t6], [t6~t7], [t7~t8], [t8~t9], [t9~t1 ...4~t5], [t5~t6], [t6~t7], [t7~t8], [t8~t9], [t9~t1], [t2~t3], [t4~t5], [t5~t6], [t6~t7], [t7~t8], 10 ]、[t 10 ~t 11 ]、[t 11 ~t 12 ], where [t0~t6] represents the working state of the first half of the cycle, and [t7~t6] represents the working state of the second half of the cycle. 12 This indicates the second half of the operating cycle. Mode 1 [t0~t1]: At time t0, power transistors S2, S3, and S5 are turned off. The primary current of the high-frequency transformer flows through the junction capacitance C of power transistor S2. oss2 The junction capacitance C of power transistor S4 oss4 Primary winding N P The junction capacitance C of power transistor S1 oss1 The junction capacitance C of power transistor S3 oss3 The secondary current of the high-frequency transformer flows through the secondary winding N. S Magnetizing inductance L m Resonant inductor L r Resonant capacitor C r The resonant cavity and the junction capacitance C of the power transistor S5 oss5 The junction capacitance C of power transistor S6 oss6 C1 voltage multiplier capacitor, C2 voltage multiplier capacitor, and finally C o1 After the filter capacitor, part of the power circuit current flows through the step-down inductor L. B Finally, through C o2 Output capacitor output; During this stage, the energy refracted by the resonant cavity onto the primary side of the high-frequency transformer causes the parallel capacitor C of power transistors S1 and S4 to... oss1 C oss4 The voltage across U in When discharged to zero, the parallel capacitor C of power transistors S2 and S3... oss2 C oss3 The voltage at both ends is charged from zero to U. in The energy of the resonant cavity causes the parallel capacitor C of the power transistor S5 to... oss5 The voltage at both ends is charged from zero to U. o1 The parallel capacitor C of power transistor S6 oss6 The voltage across U o1 Discharge to zero; the soft-switching conditions for power transistors S1 and S3 are the same, and the soft-switching conditions for power transistors S2 and S4 are the same; therefore, only power transistors S1 and S4 are analyzed. At this time, the excitation current i m With resonant current i r All are less than 0; therefore, the energy condition that power transistor S1 needs to satisfy to achieve zero-voltage turn-on is: In the formula t d Dead time; The energy condition that power transistor S4 needs to meet to achieve zero-voltage turn-on is: The excitation current during this stage is: The expression for the output current of a Buck converter is: The excitation inductance at this stage satisfies: Mode 2 [t1~t2]: At time t1, power transistors S1 and S4 are both turned on, and secondary power transistor S6 is conducting freewheeling. Due to the junction capacitance C... oss1 C oss4 C oss6 The function is that power transistors S1, S4, and S6 are at zero voltage, and the primary current of the high-frequency transformer flows through power transistor S1 and the primary winding N. P Power transistor S4; the secondary current of the high-frequency transformer flows through the secondary winding N. S Magnetizing inductance L m Resonant inductor L r Resonant capacitor C r The resonant cavity, power transistor S6, voltage multiplier capacitors C1 and C2 are constructed, and finally connected via C o1 Output after filtering capacitor; some power circuit current flows through buck inductor L B Finally, through C o2 Output capacitor output; Mode 3 [t2~t3]: At time t2, power transistor S6 is turned off, and the primary current of the high-frequency transformer flows through power transistor S1 and the primary winding N. P Power transistor S4; the secondary current of the high-frequency transformer flows through the secondary winding N. S Magnetizing inductance L m Resonant inductor L r Resonant capacitor C r The resonant cavity and the junction capacitance C of the power transistor S5 oss5 The junction capacitance C of power transistor S6 oss6 C1 voltage multiplier capacitor, C2 voltage multiplier capacitor, and finally C o1 Output after filtering capacitor; some power circuit current flows through buck inductor L B Finally, through C o2 Output capacitor output; Mode 4 [t3~t4]: At time t3, power transistor S5 is turned on. Due to the junction capacitance C... oss5 The function is that power transistor S5 is turned on with zero voltage; the primary current of the high-frequency transformer flows through power transistor S1 and the primary winding N. P Power transistor S4; the secondary current of the high-frequency transformer flows through the secondary winding N. S Magnetizing inductance L m Resonant inductor L r Resonant capacitor C r The resonant cavity, power transistor S5, voltage multiplier capacitors C1 and C2 are constructed, and finally connected via C o1 After the filter capacitor, part of the power circuit current flows through the step-down inductor L. B Finally, through C o2 Output capacitor output; Mode 5 [t4~t5]: At time t4, power transistor S5 is turned off, and the primary current of the high-frequency transformer flows through power transistor S1 and the primary winding N. P Power transistor S4; the secondary current of the high-frequency transformer flows through the secondary winding N. S Magnetizing inductance L m Resonant inductor L r Resonant capacitor C r The resonant cavity and the junction capacitance C of the power transistor S5 oss5 The junction capacitance C of power transistor S6 oss6 C1 voltage multiplier capacitor, C2 voltage multiplier capacitor, and finally C o1 After the filter capacitor, part of the power circuit current flows through the step-down inductor L. B Finally, through C o2 Output capacitor output; Mode 6 [t5~t6]: At time t5, power transistor S6 is turned on. Due to the junction capacitance C... oss6 The function is that power transistor S6 is turned on with zero voltage; the primary current of the high-frequency transformer flows through power transistor S1 and the primary winding N. P Power transistor S4; the secondary current of the high-frequency transformer flows through the secondary winding N. S Magnetizing inductance L m Resonant inductor L r Resonant capacitor C r The resonant cavity, power transistor S6, voltage multiplier capacitors C1 and C2 are constructed, and finally connected via C o1 After the filter capacitor, part of the power circuit current flows through the step-down inductor L. B Finally, through C o2 Output capacitor output.

6. A bridge-arm multiplexed LLC-Buck combined wide-gain DC-DC converter according to claim 1, characterized in that, The switching timing of the LLC-Buck combined wide-gain DC-DC converter with bridge arm multiplexing is as follows: ① After a certain dead time, power transistors S1, S4, and S6 are all turned on, (1-2D2) * T s / 4-t d After a certain time, the power transistor S6 will be turned off. ② After a certain dead time, power transistor S5 is turned on, and power transistors S1, S4, and S5 are all turned on together. 2* T s -t d Power transistor S5 will be turned off after a certain time. ③ After a certain dead time, power transistor S6 is turned on, and power transistors S1, S4 and S6 are turned on together (1-2D2). * T s / 4-t d After a certain time, power transistors S1, S4, and S6 are turned off. ④ After a certain dead time, power transistors S2, S3, and S5 are all turned on, (1-2D2) * T s / 4-t d Power transistor S5 will be turned off after a certain time. ⑤ After a certain dead time, power transistor S6 is turned on. Power transistors S2, S3, and S6 are all turned on together. 2* T s -t d After a certain time, the power transistor S6 will be turned off. ⑥ After a certain dead time, power transistor S5 is turned on, and power transistors S2, S3, and S5 are all turned on together. (1-2D) s ) * T s / 4-t d Power transistor S5 will be turned off after a certain time. ⑦ After a certain dead time, power transistors S1, S4, and S6 are turned on together, returning to the first process; this cycle continues.

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