LLC resonant converter with wide input voltage range

Abstract

This invention discloses an LLC resonant converter with a wide voltage range input, belonging to the field of power electronics technology, including a DC voltage source V. in First bus voltage divider capacitor C in1 Second bus voltage divider capacitor C in2 First full-bridge switch Q1, second full-bridge switch Q2, third full-bridge switch Q3, fourth full-bridge switch Q4, first bidirectional switch Q5, second bidirectional switch Q6, first resonant inductor L r1 Second resonant inductor L r2 First resonant capacitor C r1 Second resonant capacitor C r2 First excitation inductor L m1 Second excitation inductor L m2 Transformer TR1, Transformer TR2, First rectifier diode D7, Second rectifier diode D8, Third rectifier diode D9, Fourth rectifier diode D 10 Output filter capacitor C o And load R. This invention can effectively eliminate the situation of instantaneous input voltage instability without increasing the complexity of the main control circuit, and ensure the normal operation of downstream electrical equipment.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and more specifically to an LLC resonant converter with a wide voltage range input. Background Technology

[0002] Energy conversion efficiency has always been a hot topic, and power conversion devices, as a representative of efficiency conversion in the power industry, are widely used in various fields such as switching power supplies, distributed power supplies, and uninterruptible power supplies. Traditional power conversion devices mostly operate in hard switching mode, which has many problems such as large switching losses, high voltage stress, low power density, high EMI, and low conversion efficiency. LLC resonant converters can solve these problems very well.

[0003] In the under-resonance state, the primary-side main switch of the LLC resonant converter can achieve ZVS turn-on and the secondary-side rectifier diode can achieve ZCS turn-off, which can effectively reduce switching losses, improve the efficiency of the resonant converter, further reduce the size and weight of the resonant converter, and improve the power density and dynamic performance of the resonant converter.

[0004] Power supply stability is a key performance indicator for power electronic products in many applications, especially for precision instruments and big data centers. However, traditional LLC resonant converters have a narrow gain range and cannot maintain a constant output voltage through frequency modulation control when faced with large input voltage fluctuations. Therefore, traditional LLC resonant converters are not suitable for applications with wide input voltage ranges.

[0005] To address the aforementioned issues, Chinese invention patent application CN201510629077.X discloses a wide-input-range dual-bridge LLC resonant converter, which adds a set of bidirectional switches to a full-bridge LLC resonant converter to achieve the wide input range. Chinese invention patent application CN201911363439.X discloses an ultra-wide voltage-range isolated LLC converter, which improves the primary circuit of the transformer based on a full-bridge LLC resonant converter, employing a parallel structure of two full-bridge converters to broaden the voltage range. However, the improvements proposed in the above documents only provide a limited widening of the LLC resonant converter's voltage input range. To obtain a larger voltage input range and gain, a wide-voltage-range input LLC resonant converter is proposed. Summary of the Invention

[0006] The technical problem this invention aims to solve is how to obtain a wider voltage input range and gain. It provides an LLC resonant converter with a wide voltage input range, which maintains a constant output voltage under wide voltage input conditions through frequency modulation control and mode switching. Furthermore, it achieves ZVS (zero voltage turn-on) and ZCS (zero current turn-on) across the entire load range.

[0007] The present invention solves the above-mentioned technical problems through the following technical solution: the present invention includes a DC voltage source V. in First bus voltage divider capacitor C in1 Second bus voltage divider capacitor C in2 First full-bridge switch Q1, second full-bridge switch Q2, third full-bridge switch Q3, fourth full-bridge switch Q4, first bidirectional switch Q5, second bidirectional switch Q6, first resonant inductor L r1 Second resonant inductor L r2 First resonant capacitor C r1 Second resonant capacitor C r2 First excitation inductor L m1 Second excitation inductor L m2 Transformer TR1, Transformer TR2, First rectifier diode D7, Second rectifier diode D8, Third rectifier diode D9, Fourth rectifier diode D 10 Output filter capacitor C o and load R;

[0008] DC voltage source V in The positive terminals are respectively connected to the first bus voltage divider capacitor C. in1 The positive terminal, the drain of the first full-bridge switch Q1, and the drain of the second full-bridge switch Q2 are connected; the first bus voltage divider capacitor C in1 The negative terminals are respectively connected to the second bus voltage divider capacitor C. in2 The positive terminal and the drain of the first bidirectional switching transistor Q5 are connected; the second bus voltage divider capacitor C in2 The negative terminals are respectively connected to the DC voltage source V in The negative terminal of the first full-bridge switch Q3, the source of the third full-bridge switch Q3, and the source of the fourth full-bridge switch Q4 are connected; the source of the first bidirectional switch Q5 is connected to the source of the second bidirectional switch Q6; the second resonant inductor L... r2 One end is connected to the drain of the second bidirectional switch Q6, and the other end is connected to the second resonant capacitor C. r2 One end is connected; the second resonant capacitor C r2 The other end is connected to the second magnetizing inductor L m2 One end is connected; the second magnetizing inductor L m2 The other end is connected to the first magnetizing inductor L. m1One end of the first full-bridge switch Q2 is connected to the source of the second full-bridge switch Q2 and the drain of the fourth full-bridge switch Q4; the first magnetizing inductor L m1 The other end is connected to the first resonant capacitor C r1 One end is connected; the first resonant inductor L r1 One end is connected to the first resonant capacitor C r1 The other end is connected to the source of the first full-bridge switch Q1 and the drain of the third full-bridge switch Q3, respectively; the primary winding of the first transformer TR1 is connected in parallel to the first magnetizing inductor L. m1 Above, the primary winding of the second transformer TR2 is connected in parallel to the second magnetizing inductor L. m2 superior;

[0009] One end of the first secondary winding of the first transformer TR1 is connected to the anode of the first rectifier diode D7. The cathode of the first rectifier diode D7 is connected to the cathode of the second rectifier diode D8 and the output filter capacitor C, respectively. o One end of the first transformer TR1 is connected to one end of the load R; one end of the second secondary winding of the first transformer TR1 is connected to the anode of the second rectifier diode D8, and the other end is connected to the other end of the first secondary winding of the first transformer TR1, the cathode of the third rectifier diode D9, and the cathode of the fourth rectifier diode D8. 10 The cathode of the first transformer TR2 is connected to the cathode; one end of the first secondary winding of the second transformer TR2 is connected to the anode of the third rectifier diode D9, and the other end is connected to the output filter capacitor C. o The other end of the second secondary winding of the second transformer TR2 is connected to the other end of the load R and one end of the second secondary winding of the second transformer TR2; the other end of the second secondary winding of the second transformer TR2 is connected to the fourth rectifier diode D. 10 Anode connection.

[0010] Furthermore, the formula for calculating the resonant frequency of the resonant converter is as follows:

[0011]

[0012] Among them, f r1 f is the resonant frequency at which the resonant converter achieves binary resonance during operation. r2 L is the resonant frequency at which the three-element resonance occurs when the resonant converter is working. r C represents the resonant inductance participating in the resonance. r This represents the resonant capacitor that participates in the resonance.

[0013] Furthermore, the inductance ratio calculation formula for the resonant converter is as follows:

[0014]

[0015] Among them, L rL represents the resonant inductance participating in the resonance. m This refers to the magnetizing inductance during operation.

[0016] Furthermore, the quality factor calculation formula for the resonant converter is as follows:

[0017]

[0018] Among them, L r C represents the resonant inductance participating in the resonance. r R represents the resonant capacitance involved in the resonance. eq This represents the resistance R of the secondary side equivalent resistance referred to the primary side. eq =8N 2 R / π 2 N is the transformer turns ratio, and R is the load.

[0019] Furthermore, the gain calculation formula for the resonant converter is as follows:

[0020]

[0021] Among them, f x Indicates the switching frequency f s With resonant frequency f r The ratio, m0 represents the inductance ratio, Q o The quality factor is represented by the formula, which is based on the gain calculation formula of a half-bridge LLC resonant converter. The gain of a full-bridge LLC resonant converter is 2G.

[0022] Furthermore, the operating mode control of the resonant converter is specifically as follows:

[0023] First half-bridge mode: bidirectional switches Q5 and Q6 are continuously on, first full-bridge switch Q1 and third full-bridge switch Q3 are continuously off, and second full-bridge switch Q2 and fourth full-bridge switch Q4 are complementary on.

[0024] Second half-bridge mode: bidirectional switches Q5 and Q6 are continuously on, second full-bridge switches Q2 and fourth full-bridge switches Q4 are continuously off, and first full-bridge switches Q1 and third full-bridge switches Q3 are complementary on.

[0025] Full-bridge mode: Bidirectional switches Q5 and Q6 remain off, while the first full-bridge switch Q1, the fourth full-bridge switch Q4, the second full-bridge switch Q2, and the third full-bridge switch Q3 are complementary and conduct.

[0026] Dual-bridge superposition mode: bidirectional switches Q5 and Q6 are continuously turned on, while the first full-bridge switch Q1, the fourth full-bridge switch Q4, the second full-bridge switch Q2, and the third full-bridge switch Q3 are turned on in a complementary manner.

[0027] The present invention has the following advantages over the prior art:

[0028] 1. With an ultra-wide adjustable voltage range, the LLC resonant converter can operate in four modes by controlling the auxiliary circuit and switching circuit on the primary side of the transformer: half-bridge mode 1, half-bridge mode 2, full-bridge mode, and dual-bridge superposition mode.

[0029] 2. Under the full load range and all operating modes, the primary-side main switch can achieve ZVS turn-on, and the secondary-side rectifier diodes can achieve ZCS turn-off;

[0030] 3. The driving timing is simple, which makes it easy to control the main circuit, effectively reducing circuit losses and enabling high frequency and high power density. Attached Figure Description

[0031] Figure 1 This is a topology diagram of the LLC resonant converter in an embodiment of the present invention;

[0032] Figure 2(a) is a topology diagram of the resonant converter operating in half-bridge mode 1 in an embodiment of the present invention;

[0033] Figure 2(b) is a steady-state waveform diagram of the resonant converter operating in half-bridge mode 1 in an embodiment of the present invention;

[0034] Figure 3(a) is a topology diagram of the resonant converter operating in half-bridge mode 2 in an embodiment of the present invention;

[0035] Figure 3(b) is a steady-state waveform diagram of the resonant converter operating in half-bridge mode 2 in an embodiment of the present invention;

[0036] Figure 4(a) is a topology diagram of the resonant converter operating in full-bridge mode in an embodiment of the present invention;

[0037] Figure 4(b) is a steady-state waveform diagram of the resonant converter operating in full-bridge mode in an embodiment of the present invention;

[0038] Figure 5 This is a topology diagram of the resonant converter operating in dual-bridge superposition mode in an embodiment of the present invention;

[0039] Figure 6 This is a steady-state waveform diagram of the resonant converter operating in the dual-bridge superposition mode in an embodiment of the present invention;

[0040] Figure 7(a) shows the circuit mode (Mode1) of the resonant converter operating in the dual-bridge superposition mode in the embodiment of the present invention;

[0041] Figure 7(b) shows the circuit mode (Mode2) of the resonant converter operating in the dual-bridge superposition mode in the embodiment of the present invention;

[0042] Figure 7(c) shows the circuit mode (Mode3) of the resonant converter operating in the dual-bridge superposition mode in the embodiment of the present invention;

[0043] Figure 7(d) shows the circuit mode (Mode4) of the resonant converter operating in the dual-bridge superposition mode in the embodiment of the present invention;

[0044] Figure 7(e) shows the circuit mode (Mode5) of the resonant converter operating in the dual-bridge superposition mode in the embodiment of the present invention;

[0045] Figure 8(a) is an equivalent circuit diagram of the resonant converter operating in half-bridge mode 1 in an embodiment of the present invention;

[0046] Figure 8(b) is a resonant current diagram of the resonant converter operating in half-bridge mode 1 in an embodiment of the present invention;

[0047] Figure 8(c) is a soft-switching implementation diagram of the resonant converter operating in half-bridge mode 1 in an embodiment of the present invention;

[0048] Figure 9(a) is an equivalent circuit diagram of the resonant converter operating in half-bridge mode 2 in an embodiment of the present invention;

[0049] Figure 9(b) is a resonant current diagram of the resonant converter operating in half-bridge mode 2 in an embodiment of the present invention;

[0050] Figure 9(c) is a soft-switching implementation diagram of the resonant converter operating in half-bridge mode 2 in an embodiment of the present invention;

[0051] Figure 10(a) is an equivalent circuit diagram of the resonant converter operating in full-bridge mode in an embodiment of the present invention;

[0052] Figure 10(b) is a resonant current diagram of the resonant converter operating in full-bridge mode in an embodiment of the present invention;

[0053] Figure 10(c) is a soft-switching implementation diagram of the resonant converter operating in full-bridge mode in an embodiment of the present invention;

[0054] Figure 11(a) is an equivalent circuit diagram of the resonant converter operating in the dual-bridge superposition mode in an embodiment of the present invention;

[0055] Figure 11(b) is a resonant current diagram of the resonant converter operating in the dual-bridge superposition mode in an embodiment of the present invention;

[0056] Figure 11(c) is a soft-switching implementation diagram of the resonant converter operating in the dual-bridge superposition mode in an embodiment of the present invention.

[0057] Meaning of symbols in the image:

[0058] V in It is a DC voltage source, C in1 With C in2These are voltage divider capacitors. Q1, Q2, Q3, and Q4 are the main switching transistors, Q5 and Q6 are the auxiliary switching transistors, D1, D2, D3, D4, D5, and D6 are the body diodes of the switching transistors, and C1, C2, C3, C4, C5, and C6 are the body capacitances of the switching transistors. r1 C r2 For resonant capacitor, L r1 L r2 For resonant inductance, L m1 L m2 TR1 and TR2 are magnetizing inductors, and D7, D8, D9, and D are high-frequency transformers. 10 C is a rectifier diode, C0 is an output filter capacitor, R is the load, A is the potential point between switching transistors Q1 and Q3, B is the potential point between switching transistors Q2 and Q4, and C is the voltage divider capacitor. in1 With C in2 The potential point between; V AB V AC V BC These are the voltages between potential points A and B, between potential points A and C, and between potential points B and C, respectively; R eq The secondary resistance R is the equivalent resistance referred to the primary side; where L r1 With L r2 C r1 With C r2 L m1 With L m2 TR1 and TR2 have the same parameters, L r =L r1 =L r2 C r =C r1 =C r2 L m =L m1 =L m2 V ds1 V ds2 V ds3 V ds4 These are the drain-source voltages of the main switching transistors Q1, Q2, Q3, and Q4, respectively; I r1 I r2 These are the resonant currents of the upper and lower resonant cavities, respectively; I r For resonant current; I d i d V represents the current of a single output diode at the output terminal. gs1 V gs4 These are the drive signals for the main switching transistors Q1 and Q4, respectively. Detailed Implementation

[0059] The embodiments of the present invention are described in detail below. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments. The present invention will be further described in detail below with reference to the accompanying drawings:

[0060] like Figure 1 As shown, this embodiment of the invention provides a technical solution: a wide voltage range input LLC resonant converter, comprising: a DC voltage source V in First bus voltage divider capacitor C in1 Second bus voltage divider capacitor C in2 First full-bridge switch Q1, second full-bridge switch Q2, third full-bridge switch Q3, fourth full-bridge switch Q4, first bidirectional switch Q5, second bidirectional switch Q6, first resonant inductor L r1 Second resonant inductor L r2 First resonant capacitor C r1 Second resonant capacitor C r2 First excitation inductor L m1 Second excitation inductor L m2 Transformer TR1, Transformer TR2, First rectifier diode D7, Second rectifier diode D8, Third rectifier diode D9, Fourth rectifier diode D 10 Output filter capacitor C o and load R;

[0061] DC voltage source V in The positive terminals are respectively connected to the first bus voltage divider capacitor C. in1 The positive terminal, the drain of the first full-bridge switch Q1, and the drain of the second full-bridge switch Q2 are connected; the first bus voltage divider capacitor C in1 The negative terminals are respectively connected to the second bus voltage divider capacitor C. in2 The positive terminal and the drain of the first bidirectional switching transistor Q5 are connected; the second bus voltage divider capacitor C in2 The negative terminals are respectively connected to the DC voltage source V in The negative terminal of the first full-bridge switch Q3, the source of the third full-bridge switch Q3, and the source of the fourth full-bridge switch Q4 are connected; the source of the first bidirectional switch Q5 is connected to the source of the second bidirectional switch Q6; the second resonant inductor L... r2 One end is connected to the drain of the second bidirectional switch Q6, and the other end is connected to the second resonant capacitor C. r2 One end is connected; the second resonant capacitor C r2 The other end is connected to the second magnetizing inductor L m2 One end is connected; the second magnetizing inductor L m2 The other end is connected to the first magnetizing inductor L. m1One end of the first full-bridge switch Q2 is connected to the source of the second full-bridge switch Q2 and the drain of the fourth full-bridge switch Q4; the first magnetizing inductor L m1 The other end is connected to the first resonant capacitor C r1 One end is connected; the first resonant inductor L r1 One end is connected to the first resonant capacitor C r1 The other end is connected to the source of the first full-bridge switch Q1 and the drain of the third full-bridge switch Q3, respectively; the primary winding of the first transformer TR1 is connected in parallel to the first magnetizing inductor L. m1 Above, the primary winding of the second transformer TR2 is connected in parallel to the second magnetizing inductor L. m2 superior;

[0062] One end of the first secondary winding of the first transformer TR1 is connected to the anode of the first rectifier diode D7. The cathode of the first rectifier diode D7 is connected to the cathode of the second rectifier diode D8 and the output filter capacitor C, respectively. o One end of the first transformer TR1 is connected to the load end; one end of the second secondary winding of the first transformer TR1 is connected to the anode of the second rectifier diode D8, and the other end is connected to the other end of the first secondary winding of TR1, the cathode of the third rectifier diode D9, and the cathode of the fourth rectifier diode D8. 10 The cathode of the first transformer TR2 is connected to the cathode; one end of the first secondary winding of the second transformer TR2 is connected to the anode of the third rectifier diode D9, and the other end is connected to the output filter capacitor C. o The other end is connected to the other end of the load and one end of the second secondary winding of the second transformer TR2; the other end of the second secondary winding of the second transformer TR2 is connected to the fourth rectifier diode D. 10 Anode connection.

[0063] The formula for calculating the resonant frequency of the resonant converter described in this invention is as follows:

[0064]

[0065] Where f r1 f is the resonant frequency at which the resonant converter achieves binary resonance during operation. r2 L is the resonant frequency at which the three-element resonance occurs when the resonant converter is working. r C represents the resonant inductance participating in the resonance. r This represents the resonant capacitor that participates in the resonance.

[0066] The formula for calculating the inductance ratio of the resonant converter described in this invention is as follows:

[0067]

[0068] Where L r L represents the resonant inductance participating in the resonance.m This refers to the magnetizing inductance during operation.

[0069] The formula for calculating the quality factor of the resonant converter described in this invention is as follows:

[0070]

[0071] Where L r C represents the resonant inductance participating in the resonance. r R represents the resonant capacitance involved in the resonance. eq This represents the resistance R of the secondary side equivalent resistance referred to the primary side. eq =8N 2 R / π 2 In the formula, N is the transformer turns ratio and R is the load.

[0072] The gain calculation formula for the resonant converter described in this invention is as follows:

[0073]

[0074] Where f x Indicates the switching frequency f s With resonant frequency f r The ratio, m0 represents the inductance ratio, Q o The quality factor is represented by the formula, which is based on the gain calculation formula of a half-bridge LLC resonant converter. The gain of a full-bridge LLC resonant converter is 2G.

[0075] As shown in Figure 2(a), the LLC resonant converter operates in half-bridge mode 1, with auxiliary switches Q5 and Q6 continuously on, and main switches Q2 and Q4 conducting complementaryly.

[0076] As shown in Figure 3(b), the LLC resonant converter operates in half-bridge mode 2, with auxiliary switches Q5 and Q6 continuously on, and main switches Q1 and Q3 conducting complementaryly. The modal analysis of half-bridge mode 1 and half-bridge mode 2 is consistent with that of the traditional half-bridge LLC circuit, because the first five modes are symmetrical with the last five modes within one cycle. Here, only the first half-cycle is analyzed.

[0077] Figure 2(b) shows the steady-state waveform of the LLC resonant converter operating in half-bridge mode 1. The first half of the cycle contains five modes, as follows:

[0078] During the Mode1[t0-t1] phase, switch Q1 is turned on, switch Q3 is turned off, and resonant inductor L... r1 L r2 Resonant capacitor C r1 C r2Both participate in resonance. The magnetizing inductor is clamped by the secondary side of the transformer and does not participate in resonance. When the resonant current no longer flows through the magnetizing inductor, it enters the next mode.

[0079] During the Mode2[t1-t2] phase, the resonant current does not flow through the primary magnetizing inductor of the transformer, and the secondary rectifier circuit of the transformer does not work until the switching transistor Q1 is turned off and enters the next mode.

[0080] In the Mode3[t2-t3] phase, both switching transistors Q1 and Q3 are turned off, and the body capacitances C1 and C3 of the two transistors are charged and discharged respectively, providing conditions for the zero-voltage turn-on (ZVS) of switching transistor Q3. When the body capacitance C3 is fully discharged, the next mode is entered.

[0081] In the Mode4[t3-t4] phase, the body capacitor C3 discharges to the forward voltage drop of the body diode D3. At this time, the current flows through the body diode D3 of the switch Q3, and the drive signal of the switch Q3 changes from low to high to enter the next mode.

[0082] In Mode 5 [t4-t5], switch Q1 is turned off and switch Q3 is turned on. Simultaneously with the drive signal of switch Q3 transitioning from low to high, the voltage across Q3 is 0, resulting in zero-voltage turn-on. The resonant current continues to rotate clockwise. The next mode begins when the resonant current flowing through the magnetizing inductor reaches zero.

[0083] Since the modal analysis of half-bridge mode 2 is basically the same as that of half-bridge mode 1, the analysis of half-bridge mode 2 will not be repeated here.

[0084] As shown in Figure 4(a), the LLC resonant converter operates in full-bridge mode, with auxiliary switches Q5 and Q6 in the off state, and main switches Q1 and Q3 conducting complementaryly with Q2 and Q4. The modal analysis of the full-bridge operating mode is consistent with that of the traditional full-bridge LLC circuit. Figure 4(b) shows the steady-state waveform of the LLC resonant converter operating in full-bridge mode. The first half of the cycle contains five modes, as follows:

[0085] During the Mode1[t0-t1] phase, switching transistors Q1 and Q4 are turned on, while switching transistors Q2 and Q3 are turned off, and the resonant inductor L... r1 Resonant capacitor C r1 Magnetizing inductance L m1 The secondary side clamp of the transformer does not participate in the resonance. When the resonant current does not flow through the magnetizing inductor, the secondary side diode can be observed to turn off with zero current and enter the next mode.

[0086] During the Mode2[t1-t2] phase, the resonant current does not flow through the primary magnetizing inductance L of the transformer. m1 The full-wave rectifier circuit on the secondary side of the transformer is not working, and the resonant inductor L... r1 Resonant capacitor C r1Magnetizing inductance L m1 It participates in resonance until the switching transistors Q1 and Q4 are turned off and enter the next mode;

[0087] During the Mode3[t2-t3] phase, the switching transistors Q2 and Q3 are not yet turned on. The body capacitances C1 and C4 of the switching transistors Q1 and Q4 begin to charge due to being turned off. The resonant current discharges the body capacitances C2 and C3 of the switching transistors Q2 and Q3 to 0, providing conditions for the zero-voltage turn-on (ZVS) of the switching transistors Q2 and Q3.

[0088] During the Mode4[t3-t4] phase, the body capacitor C2 discharges to the forward voltage drop of the body diode. At this time, current flows through the body diodes D2 and D3 of the switching transistors Q2 and Q3, and the drive signals of the switching transistors Q2 and Q3 change from low to high to enter the next mode.

[0089] In the Mode5[t4-t5] phase, switches Q1 and Q4 are turned off, while switches Q2 and Q3 are turned on. At the same time that the drive signals of switches Q2 and Q3 change from low to high, their voltages are 0. Therefore, this is a zero-voltage turn-on, and the resonant current still maintains a clockwise direction. When the resonant current flowing through the magnetizing inductor is 0, the mode enters the next mode.

[0090] like Figure 5 As shown, the LLC resonant converter operates in a dual-bridge superposition mode, with auxiliary switches Q5 and Q6 continuously on, and main switches Q1 and Q3 conducting in a complementary manner to Q2 and Q4.

[0091] like Figure 6 The figure shows the steady-state waveform of the LLC resonant converter operating in dual-bridge superposition mode. The first half of the cycle contains five modes, as detailed below:

[0092] During the Mode1[t0-t1] phase, as shown in Figure 7(a), before time t0, the anti-parallel diodes D1 and D4 are already conducting. At time t0, Q1 and Q4 achieve ZVS turn-on. The primary side of transformer TR1 bears reverse voltage, and the primary side of TR2 bears forward voltage. Rectifier diodes D7 and D... 10 On; Magnetizing inductor L m1 And excitation inductance L m2 The voltage is clamped and does not participate in resonance; the resonant current I r1 The resonant current I flows through Q1. r2 Flowing through Q5 and Q6. r1 and I r2 Gradually decrease to 0; resonant current, capacitor voltage, and excitation current are:

[0093]

[0094]

[0095]

[0096] In the formula V in V is the input voltage. Cin1 For the voltage divider bus capacitor C in1 The terminal voltage, V0 is the output voltage, ω r Angular frequency, Z r Characteristic impedance, n is the transformer turns ratio;

[0097] During the Mode2[t1-t2] phase, as shown in Figure 7(b), at time t1, the resonant current I... r1 The direction is positive, and the resonant current I r2 Reduced to 0, resonant current I r2 The direction is also positive; during this process, L m1 and L m2 Rectifier diodes D7 and D do not participate in resonance. 10 When the circuit is turned on, power is supplied to the load R through the secondary windings of transformers TR1 and TR2; the resonant current, capacitor voltage, and magnetizing current are:

[0098]

[0099]

[0100]

[0101] In the formula, V Cin2 For the voltage divider bus capacitor C in2 Terminal voltage;

[0102] During the Mode3[t2-t3] phase, as shown in Figure 7(c), at time t2, the resonant current I... r1 With excitation current I m1 Equal, resonant current I r2 With excitation current I m2 Equal, rectifier diodes D7 and D 10 ZCS turn-off completed; magnetizing inductance L m1 and L m2 During the resonance process, the filter capacitor C0 provides energy to the load R; the resonant current, capacitor voltage, and excitation current are:

[0103]

[0104]

[0105]

[0106] In the formula, m is the inductance ratio.

[0107] During the Mode4[t3-t4] phase, as shown in Figure 7(d), at time t3, switches Q1 and Q4 are turned off, and the body capacitances of Q1 and Q4 are charged, while the body capacitances of Q2 and Q3 are discharged. Before time t4, the voltages across switches Q1 and Q4 rise, while the voltages across switches Q2 and Q3 drop to zero, preparing the conditions for the ZVS turn-on of Q2 and Q3. Rectifier diodes D8 and D9 begin to conduct.

[0108] During the Mode5[t4-t5] phase, as shown in Figure 7(e), at time t4, the magnetizing inductance L m1 With excitation inductance L m2 It does not participate in resonance; the resonant current I r1 Flowing through L m1 Resonant current I r2 Flowing through L m2 The secondary rectifier diodes D8 and D9 are turned on, and the switching transistors Q2 and Q3 are turned on at time t5, completing the ZVS turn-on of Q2 and Q3.

[0109] The control loop of this invention includes a sampling circuit, a control processor (microcontroller, DSP, FPGA, etc. to process the signals fed back to it), and a drive circuit that uses a modulation method to adjust the duty cycle to drive the switching circuit to send signals to the switching transistor.

[0110] The specific parameters of the resonant converter are shown in Table 1:

[0111] Table 1 Specific parameters of the resonant converter

[0112] <![CDATA[Input voltage v in / v]]> 80～370 <![CDATA[Output voltage V0 / V]]> 12 Output power P / W 240 <![CDATA[Switching frequency f s / kHz]]> 100 <![CDATA[Resonant inductor L r / uH]]> 36 <![CDATA[Resonant capacitor C r / nF]]> 54 <![CDATA[Excitation inductance L m / uH]]> 120 Transformer turns ratio n 13∶1∶1

[0113] The switching mode voltage gain of the resonant converter is shown in Table 2:

[0114] Table 2 Switching-mode voltage gain of the resonant converter

[0115]

[0116] In the table, G represents voltage gain; n represents transformer turns ratio; V in Vo and V are the DC input and DC output voltages, respectively.

[0117] According to Table 2, the resonant converter described in this invention can achieve a voltage gain range of 1 to 5.25, and can also obtain a wide DC input voltage range of 104V to 345V.

[0118] Example 1

[0119] The resonant converter described in this invention was tested using an experimental machine. The correctness and feasibility of the resonant converter circuit topology were verified by combining the oscilloscope data obtained from the experiment.

[0120] When bidirectional switches Q5 and Q6 are continuously on, switches Q2 and Q4 are continuously off, and switches Q1 and Q3 are complementary on, the resonant converter operates in half-bridge mode 1. Figure 8(a) shows the equivalent circuit for half-bridge mode 1, which consists of two LLC resonant cavities connected in series. The resonant frequency is the same as in the other three operating modes. AC Input voltage V in One-half;

[0121] The steady-state waveform of the resonant converter is shown in Figure 8(b). The input voltage is 345V, and the output voltage is 12V as shown in Table 1. Figure 8(c) verifies that the resonant converter can achieve soft switching in this mode.

[0122] Example 2

[0123] When bidirectional switches Q5 and Q6 are continuously on, switches Q1 and Q3 are continuously off, and switches Q2 and Q4 are complementary on, the resonant converter operates in half-bridge mode 2. Figure 9(a) shows the equivalent circuit for half-bridge mode 2, which consists of a series LLC resonant cavity. The resonant frequency is the same as in the other three operating modes. BC Input voltage V in Half of the input voltage. The steady-state waveform of the resonant converter is shown in Figure 9(b). The input voltage is 312V, and the output voltage is 12V as shown in Table 1. Figure 9(c) verifies that the resonant converter can achieve soft switching in this mode.

[0124] Example 3

[0125] When bidirectional switches Q5 and Q6 remain off, and switches Q1 and Q4 and Q2 and Q3 are complementaryly turned on, the resonant converter operates in full-bridge mode. Figure 10(a) shows the equivalent circuit in full-bridge mode, which consists of a series LLC resonant cavity. The resonant frequency is the same as in the other three operating modes. AB With input voltage V in The steady-state waveform of the resonant converter is shown in Figure 10(b). The input voltage is 156V, and the output voltage is 12V as shown in Table 1. Figure 10(c) verifies that the resonant converter can achieve soft switching in this mode.

[0126] Example 4

[0127] When bidirectional switches Q5 and Q6 are continuously turned on, and switches Q1 and Q4 and Q2 and Q3 are complementaryly turned on, the resonant converter operates in dual-bridge superposition mode. Figure 11(a) shows the equivalent circuit of the dual-bridge superposition mode, which consists of two LLC resonant cavities connected in series, with the same resonant frequency as the other three operating modes. The steady-state waveform of the resonant converter is shown in Figure 11(b), with an input voltage of 104V and an output voltage of 12V as shown in Table 1. Figure 11(c) verifies that the resonant converter can achieve soft switching in this mode.

[0128] In summary, the wide-voltage-range input LLC resonant converter of the above embodiments can effectively eliminate the problem of instantaneous input voltage instability without increasing the complexity of the main control circuit, thus ensuring the normal operation of downstream electrical equipment.

[0129] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A wide voltage range input LLC resonant converter, characterized in that, include: DC voltage source V in First bus voltage divider capacitor C in1 Second bus voltage divider capacitor C in2 First full-bridge switch Q1, second full-bridge switch Q2, third full-bridge switch Q3, fourth full-bridge switch Q4, first bidirectional switch Q5, second bidirectional switch Q6, first resonant inductor L r1 Second resonant inductor L r2 First resonant capacitor C r1 Second resonant capacitor C r2 First excitation inductor L m1 Second excitation inductor L m2 Transformer TR1, Transformer TR2, First rectifier diode D7, Second rectifier diode D8, Third rectifier diode D9, Fourth rectifier diode D 10 Output filter capacitor C o and load R; DC voltage source V in The positive terminals are respectively connected to the voltage divider capacitor C of the first bus. in1 The positive terminal, the drain of the first full-bridge switch Q1, and the drain of the second full-bridge switch Q2 are connected; the first bus voltage divider capacitor C in1 The negative terminals are respectively connected to the second bus voltage divider capacitor C. in2 The positive terminal and the drain of the first bidirectional switching transistor Q5 are connected; the second bus voltage divider capacitor C in2 The negative terminals are respectively connected to the DC voltage source V in The negative terminal of the first full-bridge switch Q3, the source of the third full-bridge switch Q3, and the source of the fourth full-bridge switch Q4 are connected; the source of the first bidirectional switch Q5 is connected to the source of the second bidirectional switch Q6; the second resonant inductor L... r2 One end is connected to the drain of the second bidirectional switch Q6, and the other end is connected to the second resonant capacitor C. r2 One end is connected; the second resonant capacitor C r2 The other end is connected to the second magnetizing inductor L m2 One end is connected; the second magnetizing inductor L m2 The other end is connected to the first magnetizing inductor L. m1 One end of the first full-bridge switch Q2 is connected to the source of the second full-bridge switch Q2 and the drain of the fourth full-bridge switch Q4; the first magnetizing inductor L m1 The other end is connected to the first resonant capacitor C r1 One end is connected; the first resonant inductor L r1 One end is connected to the first resonant capacitor C r1 The other end is connected to the source of the first full-bridge switch Q1 and the drain of the third full-bridge switch Q3, respectively; the primary winding of the first transformer TR1 is connected in parallel to the first magnetizing inductor L. m1 Above, the primary winding of the second transformer TR2 is connected in parallel to the second magnetizing inductor L. m2 superior; One end of the first secondary winding of the first transformer TR1 is connected to the anode of the first rectifier diode D7. The cathode of the first rectifier diode D7 is connected to the cathode of the second rectifier diode D8 and the output filter capacitor C, respectively. o One end of the first transformer TR1 is connected to one end of the load R; one end of the second secondary winding of the first transformer TR1 is connected to the anode of the second rectifier diode D8, and the other end is connected to the other end of the first secondary winding of the first transformer TR1, the cathode of the third rectifier diode D9, and the cathode of the fourth rectifier diode D8. 10 The cathode of the first transformer TR2 is connected to the cathode; one end of the first secondary winding of the second transformer TR2 is connected to the anode of the third rectifier diode D9, and the other end is connected to the output filter capacitor C. o The other end of the second secondary winding of the second transformer TR2 is connected to the other end of the load R and one end of the second secondary winding of the second transformer TR2; the other end of the second secondary winding of the second transformer TR2 is connected to the fourth rectifier diode D. 10 Anode connection.

2. The LLC resonant converter with a wide voltage range input according to claim 1, characterized in that: The formula for calculating the resonant frequency of the resonant converter is as follows: Among them, f r1 f is the resonant frequency at which the resonant converter achieves binary resonance during operation. r2 L is the resonant frequency at which the three-element resonance occurs when the resonant converter is working. r C represents the resonant inductance participating in the resonance. r This represents the resonant capacitor that participates in the resonance.

3. The LLC resonant converter with a wide voltage range input according to claim 2, characterized in that: The inductance ratio of the resonant converter is calculated using the following formula: Among them, L r L represents the resonant inductance participating in the resonance. m This refers to the magnetizing inductance during operation.

4. The LLC resonant converter with a wide voltage range input according to claim 3, characterized in that: The quality factor calculation formula for the resonant converter is as follows: Among them, L r C represents the resonant inductance participating in the resonance. r R represents the resonant capacitance involved in the resonance. eq This represents the resistance R of the secondary side equivalent resistance referred to the primary side. eq =8N 2 R / π 2 N is the transformer turns ratio, and R is the load.

5. The LLC resonant converter with a wide voltage range input according to claim 4, characterized in that: The gain calculation formula for the resonant converter is as follows: Among them, f x Indicates the switching frequency f s With resonant frequency f r The ratio, m0 represents the inductance ratio, Q o The quality factor is represented by the formula, which is based on the gain calculation formula of a half-bridge LLC resonant converter. The gain of a full-bridge LLC resonant converter is 2G.

6. A wide voltage range input LLC resonant converter according to claim 1 or 5, characterized in that: The specific operating modes of the resonant converter are as follows: First half-bridge mode: bidirectional switches Q5 and Q6 are continuously on, first full-bridge switch Q1 and third full-bridge switch Q3 are continuously off, and second full-bridge switch Q2 and fourth full-bridge switch Q4 are complementary on. Second half-bridge mode: bidirectional switches Q5 and Q6 are continuously on, second full-bridge switches Q2 and fourth full-bridge switches Q4 are continuously off, and first full-bridge switches Q1 and third full-bridge switches Q3 are complementary on. Full-bridge mode: Bidirectional switches Q5 and Q6 remain off, while the first full-bridge switch Q1, the fourth full-bridge switch Q4, the second full-bridge switch Q2, and the third full-bridge switch Q3 are complementary and conduct. Dual-bridge superposition mode: bidirectional switches Q5 and Q6 are continuously turned on, while the first full-bridge switch Q1, the fourth full-bridge switch Q4, the second full-bridge switch Q2, and the third full-bridge switch Q3 are turned on in a complementary manner.

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