CN107294394A - A kind of full-bridge type LLC resonant converter with double fault-tolerant abilitys - Google Patents

Abstract

The invention discloses a full-bridge LLC resonant converter with double fault tolerance, which comprises two full-bridge LLC resonant circuits and two auxiliary diodes; the primary side of the full-bridge LLC resonant circuit is a full-bridge circuit structure, and the secondary side is a Full-wave rectification circuit structure; the two auxiliary diodes are power diodes, which are used to reconfigure the topology of the secondary side during the second fault to ensure the normal operation of the converter. The converter of the present invention realizes the first fault tolerance through redundant circuit topology, realizes the second fault tolerance through topology reconstruction, and has the capability of maintaining normal operation after suffering two faults. The control strategy of the converter of the present invention is simple, and the voltage and current stress of the switch tube on the primary side does not increase before and after the failure, simplifies the design of system control and circuit parameters, and reduces the device cost. In addition, the switching tubes on the primary side of the converter of the present invention can realize zero-voltage turn-on during operation, which improves the efficiency of the converter and avoids electromagnetic interference caused by hard switching.

Description

A Full-Bridge LLC Resonant Converter with Double Fault Tolerance

technical field

The invention belongs to the field of power electronics and specifically designs a full-bridge LLC resonant converter with double fault tolerance.

Background technique

With the increasingly fierce competition in the aviation market, lower cost and more environmentally friendly aircraft have become a research hotspot for aviation manufacturers. In order to meet the ever-increasing requirements of the aviation industry, more electric aircraft technology has emerged. Different from traditional aircraft, it uses electric power system as the main secondary energy system, replacing the mechanical, hydraulic and pneumatic systems of traditional aircraft, improving the comprehensive utilization efficiency of energy, effectively reducing aircraft emissions, and reducing the impact on the environment . At the same time, using electric energy as a secondary energy source makes it easier to optimize the energy structure, reduces the power demand for the engine, and effectively reduces the fuel consumption of the aircraft. Compared with traditional aircraft, the power system of multi-electric aircraft is more complicated. Taking the HVDC power supply system of a multi-electric aircraft as an example, it includes a 270V high-voltage DC bus, a 28V low-voltage DC bus and a 115V/400Hz AC voltage bus. In order to realize voltage conversion and power control between buses, power electronic converters have been widely used in multi-electric aircraft power systems, such as DC-DC converters, DC-AC converters, AC-DC converters, etc.

The safety and reliability of the power system of multi-electric aircraft is very important, and the modern aviation industry requires that the power system of the aircraft can withstand multiple failures. After experiencing a failure, the power supply system should still be able to supply power to all aircraft electrical loads. And after two failures, the power system should still be able to supply power to all mission-critical loads. In order to meet the above requirements, the power electronic converter as an important component of the power system should also have the ability to tolerate multiple faults. The easiest way to achieve multiple fault tolerance is to have multiple redundant backups of power electronic converters, but redundant backups will result in a large overall system size and high costs. In order to obtain a power electronic converter with multiple fault tolerance and low cost, a series of converter topologies and control methods have been proposed in the existing literature, but most of them are aimed at DC-AC converters. The research on the corresponding DC-DC converter is relatively rare.

L.Costa and G.Buticchi proposed a topology reconfiguration in the article titled A Fault-Tolerant Series-Resonant DC-DCConverter (IEEE Transactions on Power Electronic, 2017, 32(2), pp.900-905) Technology, that is, when a bridge arm of the full-bridge series resonant DC-DC converter fails, by ensuring that the upper tube area of the bridge arm is open and the lower tube area of the bridge arm is short-circuited, the conversion from the full-bridge topology to the half-bridge topology is realized, ensuring the conversion The device can still work normally. At the same time, in order to keep the output voltage constant, this article adds an auxiliary switch tube to the secondary side circuit, so that the secondary side structure is controlled to switch to the voltage doubler output structure when a fault occurs. But the converter can only withstand one failure. In addition, after a fault occurs, in order to ensure the same power output, the current stress of the switch tube on the primary side of the converter increases, which is greater than the normal operating value, which not only increases the cost of the device, but also brings inconvenience to the design of circuit parameters.

Contents of the invention

Aiming at the above-mentioned technical problems existing in the prior art, the present invention proposes a full-bridge LLC resonant converter with double fault tolerance. The converter combines redundant structure and topology reconstruction technology. Only one redundant backup and two auxiliary diodes are needed to make the converter have double fault tolerance, which greatly improves the converter's performance while keeping the system cost as low as possible. reliability and safety.

A full-bridge LLC resonant converter with double fault tolerance is composed of two sub-circuits and two auxiliary circuits, the sub-circuit is a full-bridge LLC resonant conversion circuit, and the primary side of the full-bridge LLC resonant conversion circuit It is a full-bridge circuit structure, the secondary side is a full-wave rectification circuit structure, and the auxiliary diode is a power diode.

The primary side of the sub-circuit includes a primary winding, a resonant capacitor, a resonant inductance, a magnetizing inductance and two bridge arms connected in parallel, and each bridge arm consists of two switch tubes with anti-parallel diodes connected in series via a fuse composition; the opposite end of the primary winding is connected to the drain of the lower tube of one of the bridge arms and the lower end of the corresponding fuse through the resonant capacitor, the same end of the primary winding is connected to one end of the resonant inductor, and the other end of the resonant inductor is connected to The drain of the lower tube of the other bridge arm is connected together with the lower end of the corresponding fuse in the bridge arm; the two ends of the exciting inductance are connected with the two ends of the primary winding. The switch tube can realize zero-voltage turn-on, and a metal-oxide semiconductor field effect transistor (MOSFET) is selected.

The resonant inductance is the equivalent leakage inductance of the primary side of the isolation transformer or an external inductance; the excitation inductance is the equivalent excitation inductance of the primary side of the isolation transformer.

Preferably, both ends of the source and drain of the metal-oxide semiconductor field effect transistor (MOSFET) are connected in parallel with a buffer capacitor, and the buffer capacitor is a parasitic capacitor inside the switch tube or an external capacitor; the capacitor It is beneficial for the switching tube to realize soft switching, avoiding various electromagnetic interference problems caused by the hard switching of the switching tube, and improving the efficiency of the converter at the same time.

In the two sub-circuits, the secondary side of one of the sub-circuits includes the first and second secondary windings of the first isolation transformer, the first power diode and the second power diode; the first secondary winding of the first isolation transformer The opposite end of is connected to the cathode of the first power diode. The terminal with the same name of the first secondary winding of the first isolation transformer is connected with the terminal with the same name of the second secondary winding of the first isolation transformer, and is connected with the positive terminal of the output load. The anode of the first power diode is connected with the anode of the second power diode and connected with the negative terminal of the output load. The cathode of the second power diode is connected to the terminal with the same name of the second secondary winding of the first isolation transformer.

The secondary side of the second sub-circuit includes the first and second secondary windings of the second isolation transformer, the third power diode and the fourth power diode; the opposite end of the first secondary winding of the second isolation transformer and The anodes of the third power diodes are connected together. The terminal with the same name of the first secondary winding of the second isolation transformer is connected with the terminal with the same name of the second secondary winding of the second isolation transformer, and is connected with the negative terminal of the output load. The cathode of the third power diode is connected with the cathode of the fourth power diode and connected with the positive terminal of the output load. The anode of the fourth power diode is connected to the terminal with the same name of the second secondary winding of the second isolation transformer.

The anode of the first auxiliary diode is connected to the opposite end of the first secondary winding of the second sub-circuit and the anode of the third power diode; the cathode of the first auxiliary diode is connected to the first secondary of one of the sub-circuits The opposite end of the winding and the cathode of the first power diode are connected in common.

The anode of the second auxiliary diode is connected with the end of the same name of the second secondary winding of the second sub-circuit and the anode of the fourth power diode; the cathode of the second auxiliary diode is connected with the second secondary winding of one of the sub-circuits The terminal with the same name is connected in common with the cathode of the second power diode.

According to actual conditions, a filter capacitor is connected in parallel at both ends of the load of the converter to obtain a better output waveform.

Compared with the prior art, the inverter of the present invention has the following advantages:

(1) The converter of the present invention has double fault-tolerant capability, and can still maintain normal operation after suffering two faults, and output rated voltage and rated power normally.

(2) The voltage and current stress of the switching tube remains basically unchanged before and after each fault occurs in the converter of the present invention, which simplifies device selection and circuit parameter design, and reduces costs.

(3) When each fault occurs in the converter of the present invention, the circuit structure is automatically switched without additional auxiliary switching tubes, which simplifies the control strategy of the converter.

(4) The power switching tube in the converter of the present invention is easy to implement soft switching, avoiding various electromagnetic interference problems caused by hard switching of the switching tube, easy to realize high frequency of the circuit, and at the same time, it is beneficial to the improvement of circuit efficiency.

(5) The converter of the present invention is based on mature technology, the sub-circuit is a traditional LLC resonant circuit, the primary side is a full bridge structure, and the secondary side is a full-wave rectification structure; the circuit adopts the PFM modulation method of the traditional LLC resonant circuit , the technology is mature.

The invention can be used in the power supply system of a multi-electric aircraft to realize voltage conversion and electric energy control, or be used in other occasions requiring multiple fault-tolerant capabilities, such as server power supplies and the like.

Description of drawings

FIG. 1 is a schematic diagram of a full-bridge LLC resonant converter of the present invention.

Fig. 2 is a schematic diagram of a full-bridge LLC resonant converter of the present invention working in a normal mode.

Fig. 3 is a schematic diagram of main waveforms of the full-bridge LLC resonant converter of the present invention working in normal mode.

FIG. 4 is a schematic diagram of a full-bridge LLC resonant converter of the present invention working in mode 2A.

FIG. 5 is a schematic diagram of main waveforms of the full-bridge LLC resonant converter of the present invention working in mode 2A.

Fig. 6 is a schematic diagram of the full-bridge LLC resonant converter of the present invention working in mode 2B.

FIG. 7 is a schematic diagram of a full-bridge LLC resonant converter of the present invention working in mode 3A.

FIG. 8 is a schematic diagram of main waveforms of the full-bridge LLC resonant converter of the present invention working in mode 3A.

FIG. 9 is a schematic diagram of a full-bridge LLC resonant converter of the present invention working in mode 3B.

FIG. 10 is a schematic diagram of a full-bridge LLC resonant converter of the present invention working in mode 3C.

Fig. 11 is a schematic diagram of a full-bridge LLC resonant converter of the present invention working in mode 3D.

detailed description

In order to describe the present invention more specifically, the technical solutions and related working principles of the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

A full-bridge LLC resonant converter with double fault tolerance, including two full-bridge LLC resonant circuits and two auxiliary diodes; the primary side of the full-bridge LLC resonant circuit is a full-bridge circuit structure, and the secondary side is a full-wave rectifier circuit structure; the auxiliary diode is a power diode.

As shown in Figure 1, the primary circuit includes:

1) The first primary side branch connected in parallel with the input power supply consists of the first power switch S ₁ with anti-parallel diode D _S1 , the second power switch S ₂ with anti-parallel diode D _S2 , and the first buffer capacitor C _S1 , the second buffer capacitor C _S2 , and the first fuse F ₁ ; the drain of the first power switch S ₁ with anti-parallel diode D _S1 is connected to the positive pole of the power supply, and the first power switch S1 with anti-parallel diode D _S1 The source of the switching tube S1 is connected to _one end of the _first fuse F1, and the other end of the _first fuse F1 is connected to the drain of the _second power switching tube S2 with an antiparallel diode D _S2 (the connection point is point a ), the source of the _second power switch S2 with anti-parallel diode D _S2 is connected to the negative pole of the power supply, and the two ends of the first buffer capacitor C _S1 are respectively connected to the _first power switch S1 with anti-parallel diode D _S1 The drain and source of the second buffer capacitor C _S2 are respectively connected to the drain and source of the _second power switch S2 with anti _- parallel diode D _{S2 ;} the switch S1 and S2 It is a power metal-oxide semiconductor field effect transistor (MOSFET).

2) The second primary side branch connected in parallel with the input power supply consists of the fourth power switch S ₄ with anti-parallel diode D _S4 , the third power switch S ₄ with anti-parallel diode D _S3 , and the third buffer capacitor C _S3 , the fourth buffer capacitor C _S4 and the _second fuse F2; wherein the drain of the _fourth power switch S4 with anti-parallel diode D _S4 is connected to the positive pole of the power supply, and the fourth power switch S4 with anti-parallel diode D _{S4 The} source of the switching tube S4 is connected to one end of the _second fuse F2, and the other end of the _second fuse F2 is connected to the drain of the _third power switching tube S3 with an antiparallel diode D _S3 (the connection point is point b ), the source of the _third power switch S3 with an anti-parallel diode D _S3 is connected to the negative pole of the power supply, and the two ends of the fourth buffer capacitor C _S4 are respectively connected to the _fourth power switch S4 with an anti-parallel diode D _S4 The drain and source of the third buffer capacitor C _S3 are respectively connected to the drain and source of the _third power switch S3 with an antiparallel diode _{D S3 ;} the switch S3 and S4 It is a power metal-oxide semiconductor field effect transistor (MOSFET).

3) The third primary side branch connected in parallel with the input power supply consists of the _fifth power switch S5 with anti-parallel diode D _S5 , the sixth power switch _S6 with anti-parallel diode D _S6 , and the fifth buffer capacitor C _S5 , the sixth buffer capacitor C _S6 and the _third fuse F3; wherein the drain of the _fifth power switch S5 with anti-parallel diode D _S5 is connected to the positive pole of the power supply, and the fifth power switch with anti-parallel diode D _{S5 The} source of the switching tube S5 is connected to one end of the _third fuse F3, and the other end of the _third fuse F3 is connected to the drain of the _sixth power switching tube S6 with an antiparallel diode D _S6 (the connection point is point c ), the source of the _sixth power switch tube S6 with anti-parallel diode D _S6 is connected to the negative pole of the power supply, and the two ends of the fifth buffer capacitor C _S5 are respectively connected to the _fifth power switch tube S5 with anti-parallel diode D _S5 The drain and source of the sixth buffer capacitor C _S6 are respectively connected to the drain and source of the _sixth power switch S6 with an antiparallel diode D _{S6 ;} the switch S5 and _S6 It is a power metal-oxide semiconductor field effect transistor (MOSFET).

4) The fourth primary side branch connected in parallel with the input power supply consists of the seventh power switch S ₇ with anti-parallel diode D _S7 , the eighth power switch S ₈ with anti-parallel diode D _S8 , and the seventh buffer capacitor C _S7 , the eighth buffer capacitor C _S8 and the fourth fuse _F4 ; wherein the drain of the _eighth power switch S8 with anti-parallel diode D _S8 is connected to the positive pole of the power supply, and the eighth power switch S8 with anti-parallel diode D _S8 The source of the switching tube _S8 is connected to one end of the _fourth fuse F4, and the other end of the _fourth fuse F4 is connected to the drain of the _seventh power switching tube S7 with an antiparallel diode D _S7 (the connection point is point d ), the source of the _seventh power switch tube S7 with anti-parallel diode D _S7 is connected to the negative pole of the power supply, and the two ends of the seventh buffer capacitor C _S7 are respectively connected to the _seventh power switch tube S7 with anti-parallel diode D _S7 The drain and source of the eighth buffer capacitor C _S8 are respectively connected to the drain and source of the _eighth power switch S8 with an anti _- parallel diode D _S8 ; the switch S7 and _S8 It is a power metal-oxide semiconductor field effect transistor (MOSFET).

4) The primary winding N ₁₁ of the first isolation transformer T ₁ , the first resonant inductance L _r1 , the first resonant capacitor C _r1 and the first exciting inductance L _m1 ; one end of the resonant capacitor C _r1 is connected to point b, and C _r1 The other end of the _first isolation transformer T1 is connected to the opposite end of the primary winding _N11 , the same end of the primary winding _N11 of the first isolation transformer T1 is connected to one end of the first resonant inductor L _r1 , and the other end of L _r1 One end is connected to point a; the two ends of the first exciting inductance L _m1 are connected with the two ends of the primary winding N ₁₁ of the first isolation transformer T ₁ ,

5) The primary winding N ₂₁ of the second isolation transformer T ₂ , the second resonant inductance L _r2 , the second resonant capacitor C _r2 and the second exciting inductance L _m2 ; wherein one end of the second resonant capacitor C _r2 is connected to point d, The other end of C _r2 is connected to the opposite end of the primary winding N ₂₁ of the first isolation transformer T2, and the end of the same name of the primary winding N ₂₁ of the _second isolation transformer T2 is connected to one end of the second resonant inductor L _r2 , L _r2 The other end of is connected to point c; the two ends of the second excitation inductance L _m2 are connected with the two ends of the primary winding N21 of the _second isolation transformer T2. The secondary circuit includes:

1) The first secondary branch connected in parallel with the output load is composed of the first power diode D1 and the _first secondary winding N12 _of the _first isolation transformer T1; wherein the anode of the _first power diode D1 is connected to the output load The negative end of the first power diode D1 is connected to the negative end of the _first power diode D1 and the opposite end of the first secondary winding N12 _of the _first isolation transformer T1 is connected (the connection point is point e), and the _first isolation transformer T1 The terminal with the same name _of the secondary winding N12 is connected to the positive terminal of the output load.

2) The second secondary branch connected in parallel with the output load is composed of the second power diode D2 and the _second secondary winding _N13 of the _first isolation transformer T1; wherein the anode of the _second power diode D2 is connected to The negative terminal of the output load is connected, the cathode of the _second power diode D2 is connected with the end of the same name of the second secondary winding _N13 of the _first isolation transformer T1 (connection point is point f), the _first isolation transformer T1 The opposite end of the secondary winding N ₁₃ is connected to the positive end of the output load.

3) The third secondary branch connected in parallel with the output load is composed of the third power diode _D3 and the first secondary winding _N22 of the _second isolation transformer T2; wherein the cathode of the _third power diode D3 is connected to the output load The anode of the _third power diode D3 is connected to the opposite end of the first secondary winding _N22 of the _second isolation transformer T2 (the connection point is point g), the first of the _second isolation transformer T2 The same terminal of the secondary winding N ₂₂ is connected to the negative terminal of the output load.

4) The fourth secondary branch connected in parallel with the output load is composed of the _fourth power diode D4 and the second secondary winding _N23 of the _second isolation transformer T2; wherein the cathode of the _fourth power diode D4 is connected to the output load The positive terminal of the _fourth power diode D4 is connected to the terminal of the same name of the second secondary winding _N23 of the _second isolation transformer T2 (the connection point is point h), and the second secondary of the _second isolation transformer T2 The opposite terminal of the side winding N ₂₃ is connected to the negative terminal of the output load.

5) The first auxiliary diode D ₅ ; the anode of the first auxiliary diode D ₅ is connected to point g; the cathode of the first auxiliary diode D ₅ is connected to point e.

6) The second auxiliary diode D ₆ ; the anode of the second auxiliary diode D ₆ is connected to point h; the cathode of the second auxiliary diode D ₆ is connected to point f.

7) Output filter capacitor C _o ; the positive and negative terminals of the output filter capacitor C _o are respectively connected to the positive and negative ends of the output port.

8) Resistive load R; the resistive load R is connected across the positive and negative ends of the output port.

In Figure 1, the first resonant inductance L _r1 and the second resonant inductance L _r2 are composed of separate inductances, or the equivalent leakage inductance of the primary side of the _first isolation transformer T1 and the equivalent leakage of the primary side of the _second isolation transformer T2 Composition of inductance; the first excitation L _m1 and the second excitation inductance L _m2 are formed by the equivalent excitation inductance of the primary side of the _first isolation transformer T1 and the equivalent excitation inductance of the primary side of the _second isolation transformer T2.

In Figure 1, the first buffer capacitor _CS1 , the second buffer capacitor _CS2 , the third buffer capacitor _CS3 , the fourth buffer capacitor _CS4 , the fifth buffer capacitor _CS5 , the sixth buffer capacitor _CS6 , and the seventh buffer capacitor C _S7 and the eighth buffer capacitor C _S8 are composed of a separate capacitor, or the parasitic capacitance between the drain and source of the _first power switch tube S1 with an anti-parallel diode D _S1 , and the second power switch with an anti-parallel diode D _{S2 The} parasitic capacitance between the drain and the source of the switching tube S2, the parasitic capacitance between the drain and the source of the _third power switching tube S3 with the anti-parallel diode D _S3 , the fourth power switching tube with the anti-parallel diode D _S4 The parasitic capacitance between the drain and source of S ₄ , the parasitic capacitance between the drain and source of the _fifth power switch S5 with anti-parallel diode D _S5 , the sixth power switch _S6 with anti-parallel diode D _S6 The parasitic capacitance between the drain and the source, the parasitic capacitance between the drain and the source of the _seventh power switch S7 with anti-parallel diode D _S7 , the drain of the _eighth power switch S8 with anti-parallel diode D _S8 constitutes the parasitic capacitance between the source and the source.

The full-bridge LLC resonant converter of the present invention adopts the PFM modulation method of the traditional full-bridge LLC resonant converter, and is divided into three working modes according to the number of faults experienced:

1) Mode 1, normal working mode: as shown in Figure 2, the converter is not faulty, and only one of the sub-circuits is involved in the work, and the primary side includes the first to fourth power switch tubes S ₁ -S ₄ with anti-parallel diodes , the first and second fuses F ₁ , F ₂ , the primary winding N ₁₁ of the first isolation transformer T ₁ , the first exciting inductance L _m1 , the first resonant inductance L _r1 and the first resonant capacitor C _r1 ; the secondary side includes The first branch of the secondary side and the second branch of the secondary side, that is, the first and second power diodes D ₁ and D ₂ and the first and second secondary windings N ₁₂ and N ₁₃ of the first isolation transformer T ₁ ; In this mode, the working principle of the converter is the same as that of the full-bridge LLC resonant converter with full-wave rectification. The drives of the primary switch tubes S ₁ and S ₃ are both d ₁ , and the drives of S ₂ and S ₄ are both d ₂ and d ₁ Complementary to _d2 and both are 50% duty cycle, secondary diodes D1 and D2 work alternately, the key working waveform _of the converter in normal mode is shown in Figure ₃ .

2) Mode 2, one-time failure mode: in normal operation mode, if any switch tube on the primary side branch fails, the converter enters one-time failure mode. According to the location of the faulty branch, the mode 2 can be divided into two states: mode 2A and mode 2B. When the fault is in the first primary branch, the converter works in mode 2A; when the fault is in the second primary branch, the converter works in mode 2B.

As shown in Figure 4, assuming that the fault is located in the first primary side branch, if the _second power switch tube S2 is short-circuited after a fault occurs during normal operation, the _first fuse F1 will be blown due to the large current caused by the short-circuit, and the converter will switch to work in mode 2A. One of the sub-circuits stops working, that is, the driving of the first to fourth power switch tubes S ₁ -S ₄ is blocked. At the same time, the second sub-circuit starts to work. The primary side includes the fifth to eighth power switch tubes S ₅ -S ₈ with anti-parallel diodes, the third and fourth fuses F ₃ and F ₄ , and the second isolation transformer T ₂ The primary winding N ₂₁ , the second excitation inductance L _m2 , the second resonant inductance L _r2 and the second resonant capacitor C _r2 ; the secondary side includes the third branch of the secondary side and the fourth branch of the secondary side, that is, the third and fourth Power diodes D ₃ , D ₄ and the first and second secondary windings N ₂₂ and N ₂₃ of the second isolation transformer T ₂ ; in this mode, the working principle of the converter is basically the same as that of mode 1, and the primary switch tubes S ₅ , S ₇ is driven by d ₁ , both S ₆ and S ₈ are driven by d ₂ , d ₁ and d ₂ are complementary and both have a 50% duty cycle, the secondary diodes D ₃ and D ₄ work alternately, the converter is in The key working waveforms in mode 2A are shown in Figure 5.

As shown in Figure 6, assuming that the fault is located in the second primary side branch, if the _third power switch tube S3 is short-circuited after a fault occurs during normal operation, the _second fuse F2 will be blown due to the large current caused by the short-circuit, and the converter will switch to work in mode 2B. The same as mode 2A, one of the sub-circuits stops working, and the second sub-circuit starts to work. Its working principle, driving configuration and working waveform are exactly the same as those of mode 2A, and will not be repeated here.

3) Mode 3, secondary failure mode: on the basis of the primary failure, if any of the third or fourth primary side branch fails, the converter enters the secondary failure mode. Also according to the difference of the primary side branch where the fault is located, there are 2×2=4 classifications in mode 3, which are respectively mode 3A (fault is located in the first and third primary side branch), mode 3B (fault is located in the first and the fourth primary branch), mode 3C (the fault is located in the second and third primary branch), and mode 3D (the fault is located in the second and fourth primary branch).

As shown in Figure 7, on the basis of mode 2A, assuming that the third primary side branch fails, for example, the sixth power switch tube _S6 fails and short-circuits, the _third fuse F3 is blown, and the converter switches to mode 3A Work. At this time, the second and fourth primary side branches without failure, the first and second isolation transformers T ₁ and T ₂ , the first and second resonant inductance L _r1 and L _r2 , the first and second excitation inductance L _m1 , L _m2 , the first and second resonant capacitors C _r1 and C _r2 and the first and second secondary side auxiliary diodes D ₅ and D ₆ participate in the work to form a double half-bridge LLC resonant conversion in which the primary side is connected in parallel and the secondary side is connected in series device structure. S ₃ and S ₄ , S ₇ and S ₈ are complementary conduction, and the duty cycle is 50%, wherein the driving of S ₃ and S ₇ is d ₁ , and the driving of S ₄ and S ₈ is d ₂ . The key working waveforms of the converter in mode 3A are shown in Figure 8.

As shown in Figure 9, on the basis of mode 2A, assuming that the fourth primary side branch fails, for example, the _seventh power switch tube S7 fails and short-circuits, the _fourth fuse F4 is blown, and the converter switches to mode 3B. . Similarly, the second and third primary side branches without faults, the first and second isolation transformers T ₁ and T ₂ , the first and second resonant inductances L _r1 and L _r2 , the first and second exciting inductances L _m1 , L _m2 , the first and second resonant capacitors C _r1 and C _r2 and the first and second secondary side auxiliary diodes D ₅ and D ₆ participate in the work to form a double half-bridge LLC resonant conversion in which the primary side is connected in parallel and the secondary side is connected in series device structure. S ₃ and S ₄ , S ₅ and S ₆ are complementary conduction, and the duty cycle is 50%, wherein the driving of S ₃ and S ₅ is d ₁ , and the driving of S ₄ and S ₆ is d ₂ .

As shown in Figure 10, on the basis of mode 2B, assuming that the third primary side branch fails, for example, the fifth and sixth power switch tube _S6 fails and short-circuits, the _third fuse F3 is blown, and the converter switches Up to mode 3C work. In this mode, the first and fourth primary side branches without failure, the first and second isolation transformers T ₁ and T ₂ , the first and second resonant inductors L _r1 and L _r2 , the first and second excitation Inductors L _m1 and L _m2 , first and second resonant capacitors C _r1 and C _r2 , and first and second secondary side auxiliary diodes D ₅ and D ₆ work together to form a double half-bridge LLC resonant converter structure. S ₁ and S ₂ , S ₇ and S ₈ are complementary conduction, and the duty cycle is 50%, wherein the driving of S ₁ and S ₇ is d ₁ , and the driving of S ₂ and S ₈ is d ₂ .

As shown in Figure 11, on the basis of mode 2B, assuming that the fourth primary side branch fails, for example, the seventh power switch tube S ₇ fails and then short-circuits, the fourth fuse F ₄ is blown, and the converter switches to mode 3D. . In this mode, the first and third primary side branches without failure, the first and second isolation transformers T ₁ and T ₂ , the first and second resonant inductors L _r1 and L _r2 , the first and second excitation Inductors L _m1 and L _m2 , first and second resonant capacitors C _r1 and C _r2 , and first and second secondary side auxiliary diodes D ₅ and D ₆ work together to form a double half-bridge LLC resonant converter structure. S ₁ and S ₂ , S ₅ and S ₆ are complementary conduction, and the duty cycle is 50%, wherein the driving of S ₁ and S ₅ is d ₁ , and the driving of S ₂ and S ₆ is d ₂ .

The working waveform of the converter in mode 3B-3D is similar to the key working waveform of mode 3A shown in Fig. 9 and is not shown here. Table 1 shows the fault status corresponding to each working mode and the drive of each power switch tube in different modes, where 0 means that the drive is blocked, and 1 means that the corresponding switch tube is short-circuited after failure.

Table 1 Corresponding fault state and drive of each switching tube for each mode of the converter of the present invention

Claims (7)

1. A full-bridge LLC resonant converter with double fault tolerance is characterized in that: it is made of two sub-circuits and two auxiliary diodes, and said sub-circuit is a full-bridge LLC resonant circuit; said full-bridge LLC The primary side of the resonant circuit is a full-bridge circuit structure, which is used to invert the DC input voltage into an AC voltage, and the secondary side is a full-wave rectification structure, which is used to rectify the AC voltage obtained from the primary side into a DC output voltage. The two sub-circuits The primary side shares one input; the secondary sides of the two sub-circuits share one output; the auxiliary diode is a power diode, which is arranged between the secondary sides of the two sub-circuits, and is used to reconstruct the converter in the secondary failure mode to achieve fault tolerance function, the secondary failure mode refers to the failure of the primary sides of the two sub-circuits. 2. The full-bridge LLC resonant converter with double fault tolerance according to claim 1, characterized in that: the primary sides of each sub-circuit include a primary winding, a resonant capacitor, a resonant inductance, and an excitation Inductor and two parallel bridge arms, each bridge arm is composed of two switch tubes with anti-parallel diodes connected in series through a fuse; the opposite end of the primary winding is connected to the drain of the lower tube of one of the bridge arms through a resonant capacitor And the lower end of the fuse in the bridge arm is connected together, the end of the primary winding with the same name is connected to one end of the resonant inductance, the other end of the resonant inductance is connected to the drain of the lower tube of the other bridge arm and the lower end of the corresponding fuse; the excitation inductance The two ends of the winding are connected to the two ends of the primary winding. 3. The full-bridge LLC resonant converter with double fault tolerance according to claim 2, characterized in that: the resonant inductance is the transformer primary equivalent leakage inductance or external inductance; the magnetizing inductance is The equivalent magnetizing inductance of the primary side of the transformer. 4. The full-bridge LLC resonant converter with double fault tolerance according to claim 2, characterized in that: the source and drain terminals of the switching tubes forming the bridge arms are provided with snubber capacitors, and the snubber capacitors It is the parasitic capacitance inside the switch tube or external capacitance. 5. The full-bridge LLC resonant converter with double fault tolerance according to claim 4, characterized in that: in the two sub-circuits, the secondary side of one of the sub-circuits comprises the first, The second secondary winding, the first power diode and the second power diode; the opposite end of the first secondary winding of the first isolation transformer is connected to the cathode of the first power diode, and the first secondary winding of the first isolation transformer The end with the same name is connected to the end with the same name of the second secondary winding of the first isolation transformer, and is connected to the positive end of the output load, and the anode of the first power diode is connected to the anode of the second power diode, and is connected to the negative end of the output load, The cathode of the second power diode is connected to the end with the same name of the second secondary winding of the first isolation transformer; the secondary side of the second sub-circuit includes the first and second secondary windings of the second isolation transformer, the third power diode and the second secondary winding Four power diodes; the opposite end of the first secondary winding of the second isolation transformer is connected to the anode of the third power diode, and the same end of the first secondary winding of the second isolation transformer is connected to the second secondary of the second isolation transformer The opposite end of the side winding is connected to the negative end of the output load, the cathode of the third power diode is connected to the cathode of the fourth power diode, and is connected to the positive end of the output load, and the anode of the fourth power diode is connected to the second isolation transformer The same-named end of the second secondary side winding is connected. 6. the full-bridge LLC resonant converter with double fault tolerance according to claim 5, is characterized in that: the anode of the first auxiliary diode and the opposite end of the first secondary winding of two of the sub-circuits And the anode of the third power diode is connected in common; the cathode of the first auxiliary diode is connected in common with the opposite end of the first secondary winding of one of the sub-circuits and the cathode of the first power diode; the anode of the second auxiliary diode It is connected with the same-named end of the second secondary winding of the second sub-circuit and the anode of the fourth power diode; the cathode of the second auxiliary diode is connected with the same-named end of the second secondary winding of one of the sub-circuits and the second power diode Cathode common connection. 7. The full-bridge LLC resonant converter with double fault tolerance according to claim 1, characterized in that a filter capacitor is connected in parallel at both ends of the load of the converter.