A combined flyback converter with a voltage equalizing module

Abstract

The present invention discloses a combined flyback converter with a voltage equalizing module, comprising: a front-stage voltage equalizing module and a rear-stage output module; wherein, the front-stage voltage equalizing module includes a power supply, and the rear-stage output module includes a first load terminal and a second load terminal; the front-stage voltage equalizing module is configured to perform voltage equalizing processing on the input voltage of the power supply port and then input it to the rear-stage output module; the rear-stage output module is configured to convert the voltage after voltage equalizing processing and output it externally through the first load terminal and the second load terminal. The combined flyback converter of the present invention can process high input voltages through low-voltage power semiconductor devices. In addition, input voltage equalization can be achieved without any special control strategy, simplifying the control system and improving stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of switching power supplies, and particularly relates to a combined flyback converter with a voltage equalizing module. Background Art

[0002] In recent years, the application of high DC input voltage has gradually increased. The DC bus voltage of a converter with high voltage input can usually reach several thousand volts, which requires the converter to have the ability to handle high input voltage. Literature (A. Kadavelugu, G. Wang, S. Bhattacharya and A. Huang, “Auxiliary power supply for Solid State Transformers,” 2012 IEEE Energy Conversion Congress and Exposition (ECCE), 2012, pp. 1426-1432.) etc. proposed a converter based on high voltage (HV) power semiconductor devices, and the voltage stress of the switching device is 3 kV, which is very uneconomical for low power applications. Literature (A. J. B. Bottion and I. Barbi, “Input-Series and Output-Series Connected Modular Output Capacitor Full-Bridge PWM DC–DC Converter,” in IEEE Transactions on Industrial Electronics, vol. 62, no. 10, pp. 6213-6221, Oct. 2015.) etc. proposed a high voltage converter based on a modular input series structure, which reduces the voltage stress of the switching device through voltage distribution between series modules. However, if a modular series structure is used, the voltage imbalance problem between series modules must be solved. To achieve input voltage sharing (IVS), literature (L. Qu, D. Zhang and B. Zhang, "Input Voltage Sharing Control Scheme for Input Series and Output Parallel Connected DC–DC Converters Based on Peak Current Control," in IEEE Transactions on Industrial Electronics, vol. 66, no. 1, pp. 429-439, Jan. 2019.) etc. proposed some special voltage balance control strategies. Since these control strategies inevitably introduce some closed-loop controllers, it greatly increases the complexity of the control system and reduces the stability of the converter.

[0003] To simplify the circuit system, a flyback-based input series output parallel high-voltage converter was proposed in literature (A. Rodriguez et al., “Auxiliary power supply based on a modular ISOP flyback configuration with very high input voltage,” 2016 IEEE Energy Conversion Congress and Exposition (ECCE), 2016, pp. 1-7.). The output sides of all flyback converters are connected in parallel and operate in continuous conduction mode to stabilize the input voltage of the series modules. However, this topology cannot achieve input voltage sharing (IVS). In addition, the proposed access point can only provide a single output and cannot be used for multi-output applications. Additionally, a input series flyback converter was proposed in literature (T. Meng, Y. Song, Z. Wang, H. Ben and C. Li, “Investigation and Implementation of an Input-Series Auxiliary Power Supply Scheme for High-Input-Voltage Low-Power Applications,” in IEEE Transactions on Power Electronics, vol. 33, no. 1, pp. 437-447, Jan. 2018.). An integrated transformer instead of a single transformer was used in it, and input voltage sharing (IVS) was achieved by using the principle of electromagnetic coupling. However, for an integrated transformer, the manufacturing process is complex and the manufacturing cost is high, which is not suitable for wide use. Summary of the Invention

[0004] In view of the above problems, the present invention provides a combined flyback converter with a voltage sharing module to solve the problem of voltage imbalance between the converter modules of a modular input series structure.

[0005] A combined flyback converter with a voltage sharing module includes: a front-stage voltage sharing module and a rear-stage output module; wherein, the front-stage voltage sharing module includes a power supply, and the rear-stage output module includes a first load terminal and a second load terminal; the front-stage voltage sharing module is used to perform voltage sharing processing on the input voltage of the power supply port and then input it to the rear-stage output module; the rear-stage output module is used to convert the voltage after voltage sharing processing and output it externally through the first load terminal and the second load terminal.

[0006] Furthermore, the front-stage voltage sharing module further includes a first switching tubeS i1 , the second switching transistor S i2 , the third switching transistor S i3 , the fourth switching transistor S i4 , the fifth switching transistor S i5 , the sixth switching transistor S i6 , the first inductor L i1 , the second inductor L i2 , the third inductor L i3 , the first voltage-sharing capacitor C i1 , the second voltage-sharing capacitor C i2 , the third voltage-sharing capacitor C i3 and the fourth voltage-sharing capacitor C i4 ;

[0007] Among them, the drain of the first switching transistor S i1 is connected to the positive pole of the power supply, and the source of the first switching transistor S i1 is connected to the drain of the second switching transistor S i2 , the drain of the third switching transistor S i3 is connected to the source of the second switching transistor S i2 , the source of the third switching transistor S i3 is connected to the drain of the fourth switching transistor S i4 , the source of the fourth switching transistor S i4 is connected to the negative pole of the power supply, and the source of the fifth switching transistor S i5 is connected to the drain of the sixth switching transistor S i6 ; The first end of the first inductor L i1 is connected to the source of the first switching transistor S i1 and the drain of the second switching transistor S i2 , and the second end of the first inductor L i1 is connected to one end of the first voltage-sharing capacitor C i1 and one end of the second voltage-sharing capacitorC i2 One end is connected; the second inductor L i2 The first end is connected to the source of the third switching transistor S i3 and the drain of the fourth switching transistor S i4 The second inductor is connected to one end of the third voltage-sharing capacitor L i2 The second end is connected to one end of the third voltage-sharing capacitor C i3 and one end of the fourth voltage-sharing capacitor C i4 The third inductor L i3 The first end is connected to the source of the fifth switching transistor S i5 and the drain of the sixth switching transistor S i6 The third inductor L i3 The second end is connected to the source of the second switching transistor S i2 and the drain of the third switching transistor S i3 The third inductor L i3 The second end is also connected to one end of the second voltage-sharing capacitor C i2 and one end of the third voltage-sharing capacitor C i3 are connected.

[0008] Furthermore, the post-stage output module further includes a first flyback converter, a second flyback converter, a third flyback converter, and a fourth flyback converter;

[0009] Among them, the input ends of the first flyback converter, the second flyback converter, the third flyback converter, and the fourth flyback converter are connected in series and then respectively connected to the first voltage-sharing capacitor C i1 , the second voltage-sharing capacitor C i2 , the third voltage-sharing capacitor C i3 , the fourth voltage-sharing capacitor C i4 are connected.

[0010] Furthermore, the input end of the first flyback converter includes the exciting inductor of the input end of the first transformer T 1 L m1 and the first switching transistor S i1 , the input end of the second flyback converter includes the second transformer TThe magnetizing inductance of the input terminal of 2 L m2 and the second switching transistor S i2 The input terminal of the third flyback converter includes a third transformer T The magnetizing inductance of the input terminal of 3 L m3 and the third main switching transistor S 3. The input terminal of the fourth flyback converter includes a fourth transformer T The magnetizing inductance of the input terminal of 4 L m4 and the fourth main switching transistor S 4;

[0011] Wherein, one end of the magnetizing inductance of the input terminal of the first transformer T 1 is connected to the positive pole of the power supply, the drain of the first switching transistor L m1 , one end of the first equalizing capacitor S i1 . The other end of the magnetizing inductance of the input terminal of the first transformer C i1 1 is connected to the drain of the first main switching transistor T 1. The source of the first main switching transistor L m1 1 is connected to one end of the magnetizing inductance of the input terminal of the second transformer S 2. The other end of the magnetizing inductance of the input terminal of the second transformer S 1 is connected to the drain of the second main switching transistor T 2. The source of the second main switching transistor L m2 2 is connected to one end of the magnetizing inductance of the input terminal of the third transformer T 2. The other end of the magnetizing inductance of the input terminal of the third transformer L m2 2 is connected to the drain of the third main switching transistor S 2. The source of the third main switching transistor S 2 is connected to one end of the magnetizing inductance of the input terminal of the third transformer T 3. The other end of the magnetizing inductance of the input terminal of the third transformer L m3 3 is connected to the drain of the third main switching transistor T 3. The source of the third main switching transistor L m3 3 is connected to one end of the magnetizing inductance of the input terminal of the fourth transformer S 3. The other end of the magnetizing inductance of the input terminal of the fourth transformer S 3 is connected to the drain of the fourth main switching transistor T 4. The source of the fourth main switching transistor L m4 4 is connected to one end of the magnetizing inductance of the input terminal of the fourth transformer T 4. The other end of the magnetizing inductance of the input terminal of the fourth transformer L m4 4 is connected to the drain of the fourth main switching transistor S 4. The source of the fourth main switching transistorS The source electrode of 4 is connected to the negative electrode of the power supply, the fourth switching transistor S i1 the source electrode of, the fourth voltage-sharing capacitor C i4 is connected at one end.

[0012] Furthermore, the first inductor L i1 the second end is also connected to the source electrode of the first main switching transistor S 1, the input excitation inductor of the second transformer T 2 L m2 is connected at one end; the second inductor L i2 the second end is also connected to the source electrode of the third main switching transistor S 3, the input excitation inductor of the fourth transformer T 4 L m4 is connected at one end; the third inductor L i3 the second end is also connected to the source electrode of the second main switching transistor S 2, the input excitation inductor of the third transformer T 3 L m3 is connected at one end.

[0013] Furthermore, the first flyback converter further includes a first rectifying diode D 1, a first output capacitor C o1 ;

[0014] wherein, one end of the secondary side of the first transformer T 1 is connected to the anode of the first rectifying diode D 1, the cathode of the first rectifying diode D 1 is connected to one end of the first output capacitor C o1 one end of the first output capacitor C o1 the other end is connected to the other end of the secondary side of the first transformer T 1.

[0015] Furthermore, the second flyback converter further includes a second rectifying diode D 2, a second output capacitor C o2 ;

[0016] wherein, one end of the secondary side of the second transformer T 2 is connected to the anode of the second rectifying diode D 2, the cathode of the second rectifying diode D 2 is connected to the second output capacitor Co2 One end is connected, and the second output capacitor C o2 The other end is connected to the secondary side of the second transformer T at the other end of the secondary side of 2.

[0017] Furthermore, the third flyback converter further includes a third rectifier diode D 3 and a third output capacitor C o3 ;

[0018] Wherein, one end of the secondary side of the third transformer T 3 is connected to the anode of the third rectifier diode D 3, and the cathode of the third rectifier diode D 3 is connected to one end of the third output capacitor C o3 One end is connected, and the third output capacitor C o3 The other end is connected to the other end of the secondary side of the third transformer T 3.

[0019] Furthermore, the fourth flyback converter further includes a fourth rectifier diode D 4 and a fourth output capacitor C o4 ;

[0020] Wherein, one end of the secondary side of the fourth transformer T 4 is connected to the anode of the fourth rectifier diode D 4, and the cathode of the fourth rectifier diode D 4 is connected to one end of the fourth output capacitor C o4 One end is connected, and the fourth output capacitor C o4 The other end is connected to the other end of the secondary side of the fourth transformer T 4.

[0021] Furthermore, in one switching cycle, the pre-stage voltage sharing module includes a first mode of the pre-stage voltage sharing module and a second mode of the pre-stage voltage sharing module;

[0022] First mode of the pre-stage voltage sharing module: The first switch tube S i1 , the third switch tube S i3 , and the fifth switch tube S i5 are turned on, and the current of the first inductor L i1 , the second inductor L i2 , and the third inductor L i3 continues to rise to store energy;

[0023] The second mode of the pre-stage voltage equalizing module: the second switching tube S i2 , the fourth switching tube S i4 , the sixth switching tube S i6 turn on, and the current of the first inductor L i1 , the second inductor L i2 , the third inductor L i3 starts to decrease and releases energy.

[0024] Furthermore, the post-stage output module includes a first mode and a second mode of the post-stage output module in one switching cycle;

[0025] The first mode of the post-stage output module: the first main switching tube S 1. The second main switching tube S 2. The third main switching tube S 3. The fourth main switching tube S 4 turn on, and the voltages output by the first voltage equalizing capacitor C i1 V i1 , the second voltage equalizing capacitor C i2 V i2 , the third voltage equalizing capacitor C i3 V i3 , the fourth voltage equalizing capacitor C i4 V i4 respectively charge the exciting inductors at the input ends of the first transformer T 1, the second transformer L m1 , the third transformer T 2, the fourth transformer L m2 3, the fourth transformer T 3, the exciting inductors at the input ends of the fourth transformer L m3 , the fourth transformer T 4, the exciting inductors at the input ends of the fourth transformer L m4 , and the energy is stored in the first transformer T 1, the second transformer T 2, the third transformer T 3, the fourth transformer T 4;​​​​

[0026] Second mode of the post-stage output module: the first main switch S 1. The second main switch S 2. The third main switch S 3. The fourth main switch S 4 is turned off, and the exciting inductance of the input end of the first transformer T of the first transformer L m1 and the second transformer T of the exciting inductance of the input end of the second transformer L m2 and the third transformer T of the exciting inductance of the input end of the third transformer L m3 and the fourth transformer T of the exciting inductance of the input end of the fourth transformer L m4 discharges, and the energy is transferred to the first load terminal and the second load terminal through the first transformer T1, the second transformer T2, the third transformer T3, and the fourth transformer T4.

[0027] Furthermore, by controlling the first main switch S 1, the second main switch S 2, the third main switch S 3, the fourth main switch S 4 of the drive duty cycle d , the voltage gain of the converter is specifically:

[0028]

[0029] In the formula, V out represents the output voltage of the flyback converter, V ix represents the input voltage of the flyback converter, where ，x=1-4， respectively represent the input voltages of the first flyback converter, the second flyback converter, the third flyback converter, and the fourth flyback converter V i1 , V i2 , V i3 , V i4 ，N represents the first transformer T 1, the second transformer T 2, the third transformer T 3, the fourth transformer T 4 turns ratio of the primary and secondary sides.

[0030] Furthermore, the first main switch S1. The second main switching transistor S 2. The third main switching transistor S 3. The fourth main switching transistor S 4. The voltage stress is V Sm :

[0031] V Sm= V ix + NV om

[0032] Wherein, m = 1, 2, V S1 represents the first main switching transistor S 1. The voltage stress of the third main switching transistor S 3; V S2 represents the second main switching transistor S 2. The voltage stress of the fourth main switching transistor S 4; V ix represents the input voltage of the flyback converter, where ，x=1-4， respectively represent the input terminal voltages of the first flyback converter, the second flyback converter, the third flyback converter, and the fourth flyback converter V i1 , V i2 , V i3 , V i4 ，N represents the first transformer T 1. The second transformer T 2. The third transformer T 3. The fourth transformer T 4. The turns ratio of the primary and secondary sides ，V om represents the load terminal voltage, V o1 represents the first load terminal voltage, V o2 represents the second load terminal voltage.

[0033] Advantages of the present invention: The combined flyback converter of the present invention can handle high input voltages with low-voltage power semiconductor devices. In addition, input voltage equalization can be achieved without any special control strategy, simplifying the control system and improving stability.

[0034] Other features and advantages of the present invention will be set forth in the following description, and in part will be obvious from the description, or may be learned by practice of the present invention. The objectives and other advantages of the present invention may be realized and attained by the structure particularly pointed out in the specification, claims as well as the drawings. Description of the Drawings

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following briefly introduces the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0036] Figure 1 Shows the main circuit diagram of a combined flyback converter with a voltage equalizing module according to an embodiment of the present invention;

[0037] Figure 2 Shows the current path diagram of the first mode of the front-stage voltage equalizing module according to an embodiment of the present invention;

[0038] Figure 3 Shows the current path diagram of the second mode of the front-stage voltage equalizing module according to an embodiment of the present invention;

[0039] Figure 4 Shows the current path diagram of the first mode of the rear-stage output module according to an embodiment of the present invention;

[0040] Figure 5 Shows the current path diagram of the second mode of the rear-stage output module according to an embodiment of the present invention. Detailed Embodiments

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following clearly and completely describes the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0042] The present invention provides a low-power combined flyback converter applicable to high-voltage input and low-voltage output with a voltage equalizing module. The front-stage voltage equalizing module evenly distributes the high input voltage across four capacitors, reducing the voltage stress on the devices of the rear-stage output module.

[0043] Please refer to Figure 1 , Figure 1 which shows the main circuit diagram of a combined flyback converter with a voltage equalizing module according to an embodiment of the present invention.

[0044] A combined flyback converter with a voltage equalizing module, comprising a front-stage voltage equalizing module and a rear-stage output module, the front-stage voltage equalizing module is connected to the rear-stage output module; the front-stage voltage equalizing module includes a power supply, and the rear-stage output module includes a first load terminal and a second load terminal; the front-stage voltage equalizing module is configured to perform voltage equalizing processing on the input voltage of the power supply and then input it to the rear-stage output module; the rear-stage output module is configured to convert the voltage after voltage equalizing processing and output it externally through the first load terminal and the second load terminal.

[0045] The front-stage voltage equalizing module and the rear-stage output module of the embodiment of the present invention work independently, and the operating frequencies of the two modules may be different. To reduce the volume of the transformer and improve the power density of the device, the switching operating frequency of the rear-stage output module can be increased.

[0046] Specifically, the front-stage voltage equalizing module further includes a first half-bridge, a second half-bridge, a third half-bridge, a first inductor L i1 , a second inductor L i2 , a third inductor L i3 , a first voltage equalizing capacitor C i1 , a second voltage equalizing capacitor C i2 , a third voltage equalizing capacitor C i3 , a fourth voltage equalizing capacitor C i4 . Among them, the first half-bridge includes a first switching tube S i1 and a second switching tube connected in series S i2 , the source of the first switching tube S i1 is connected to the drain of the second switching tube S i2 ; the second half-bridge includes a third switching tube S i3 and a fourth switching tube connected in series S i4 , the source of the third switching tube S i3 is connected to the drain of the fourth switching tube S i4 ; the third half-bridge includes a fifth switching tube S i5 and a sixth switching tube connected in series S i6 , the source of the fifth switching tube S i5 is connected to the drain of the sixth switching tube S i6 .

[0047] The first half-bridge and the second half-bridge are connected in series across both ends of a power supply. The drain of the third switching transistor S i3 is connected to the source of the second switching transistor S i2 . The drain of the first switching transistor S i1 is connected to the positive pole of the power supply. The source of the fourth switching transistor S i4 is connected to the negative pole of the power supply.

[0048] The first voltage-sharing capacitor C i1 has one end connected to the positive pole of the power supply and the drain of the first switching transistor S i1 . The other end of the first voltage-sharing capacitor C i1 is connected in series with the second voltage-sharing capacitor C i2 , the third voltage-sharing capacitor C i3 , and the fourth voltage-sharing capacitor C i4 in sequence. One end of the fourth voltage-sharing capacitor C i4 is connected to the negative pole of the power supply. The drain of the fifth switching transistor S i5 is connected to one end of the first voltage-sharing capacitor C i1 and one end of the second voltage-sharing capacitor C i2 . The source of the sixth switching transistor S i6 is connected to one end of the third voltage-sharing capacitor C i3 and one end of the fourth voltage-sharing capacitor C i4 .

[0049] The first inductor L i1 has its first end connected to the source of the first switching transistor S i1 and the drain of the second switching transistor S i2 . The second end of the first inductor L i1 is connected to one end of the first voltage-sharing capacitor C i1 and one end of the second voltage-sharing capacitor C i2 . The first end of the second inductor L i2 is connected to the third switching transistor Si3 The source electrode of S i4 is connected to the drain electrode of the fourth switching transistor, and the second inductor L i2 The second end is connected to one end of the third voltage-sharing capacitor C i3 and one end of the fourth voltage-sharing capacitor C i4 ; The third inductor L i3 The first end is connected to the source electrode of the fifth switching transistor S i5 and the drain electrode of the sixth switching transistor S i6 ; The third inductor L i3 The second end is also connected to the source electrode of the second switching transistor S i2 and the drain electrode of the third switching transistor S i3 ; The third inductor L i3 The second end is also connected to one end of the second voltage-sharing capacitor C i2 and one end of the third voltage-sharing capacitor C i3 .

[0050] Specifically, the post-stage output module further includes a first flyback converter, a second flyback converter, a third flyback converter, and a fourth flyback converter. Among them, the input terminals of the first flyback converter, the second flyback converter, the third flyback converter, and the fourth flyback converter are connected in series and then respectively connected to the first voltage-sharing capacitor C i1 , the second voltage-sharing capacitor C i2 , the third voltage-sharing capacitor C i3 , and the fourth voltage-sharing capacitor C i4 .

[0051] The output terminal of the first flyback converter and the output terminal of the third flyback converter are connected in parallel to form a first load terminal, and the output terminal of the second flyback converter and the output terminal of the fourth flyback converter are connected in parallel to form a second load terminal.

[0052] The first flyback converter includes a first main switching transistor S 1, a first transformer T 1, a first rectifying diode D 1, and a first output capacitor C o1 . The second flyback converter includes a second main switching transistor S 2, a second transformer T2. The second rectifying diode D 2. The second output capacitor C o2 . The third flyback converter includes a third main switching transistor S 3. The third transformer T 3. The third rectifying diode D 3. The third output capacitor C o3 . The fourth flyback converter includes a fourth main switching transistor S 4. The fourth transformer T 4. The fourth rectifying diode D 4. The fourth output capacitor C o4 .

[0053] Specifically, the first load terminal is connected in parallel with the first output capacitor C o1 and the third output capacitor C o3 ; the second load terminal is connected in parallel with the second output capacitor C o2 and the fourth output capacitor C o4 .

[0054] Specifically, the input terminal of the first flyback converter includes the input excitation inductance of the first transformer T 1 and the first switching transistor L m1 and the first switching transistor S i1 , the input terminal of the second flyback converter includes the input excitation inductance of the second transformer T 2 and the second switching transistor L m2 and the second switching transistor S i2 , the input terminal of the third flyback converter includes the input excitation inductance of the third transformer T 3 and the third main switching transistor L m3 and the third main switching transistor S 3, the input terminal of the fourth flyback converter includes the input excitation inductance of the fourth transformer T 4 and the fourth main switching transistor L m4 and the fourth main switching transistor S 4;

[0055] Among them, one end of the input excitation inductance of the first transformer T 1 is connected to the positive pole of the power supply, the drain of the first switching transistor L m1 and the drain of the first switching transistor S i1 , the first voltage-sharing capacitor Ci1 One end is connected to the exciting inductance of the input terminal of the first transformer T of the first transformer 1 L m1 The other end is connected to the drain of the first main switch transistor S 1, and the source of the first main switch transistor S 1 is connected to the exciting inductance of the input terminal of the second transformer T 2 L m2 One end is connected to the exciting inductance of the input terminal of the second transformer T of the second transformer 2 L m2 The other end is connected to the drain of the second main switch transistor S 2, and the source of the second main switch transistor S 2 is connected to the exciting inductance of the input terminal of the third transformer T 3 L m3 One end is connected to the exciting inductance of the input terminal of the third transformer T of the third transformer 3 L m3 The other end is connected to the drain of the third main switch transistor S 3, and the source of the third main switch transistor S 3 is connected to the exciting inductance of the input terminal of the fourth transformer T 4 L m4 One end is connected to the exciting inductance of the input terminal of the fourth transformer T of the fourth transformer 4 L m4 The other end is connected to the drain of the fourth main switch transistor S 4, and the source of the fourth main switch transistor S 4 is connected to the negative pole of the power supply, the source of the fourth switch transistor S i1 and one end of the fourth equalizing capacitor C i4 One end is connected.

[0056] The first inductor L i1 The second end is also connected to the source of the first main switch transistor S 1, the exciting inductance of the input terminal of the second transformer T 2 L m2 One end is connected; the second inductor L i2 The second end is also connected to the source of the third main switch transistor S 3, the exciting inductance of the input terminal of the fourth transformer T 4 L m4 One end is connected; the third inductor L i3 The second end is also connected to the second main switch transistorS The source electrode of 2, the third transformer T The input end exciting inductance of 3 L m3 Are connected at one end.

[0057] The first transformer T The output end of 1 is connected to the first rectifying diode D 1, the first output capacitor C o1 In series, specifically: the first transformer T One end of the secondary side of 1 is connected to the anode of the first rectifying diode D 1, the cathode of the first rectifying diode D 1 is connected to one end of the first output capacitor C o1 One end of the first output capacitor C o1 The other end is connected to the other end of the secondary side of the first transformer T 1.

[0058] The second transformer T The output end of 2 is connected to the second rectifying diode D 2, the second output capacitor C o2 In series, specifically: the second transformer T One end of the secondary side of 2 is connected to the anode of the second rectifying diode D 2, the cathode of the second rectifying diode D 2 is connected to one end of the second output capacitor C o2 One end of the second output capacitor C o2 The other end is connected to the other end of the secondary side of the second transformer T 2.

[0059] The third transformer T The output end of 3 is connected to the third rectifying diode D 3, the third output capacitor C o3 In series, specifically: the third transformer T One end of the secondary side of 3 is connected to the anode of the third rectifying diode D 3, the cathode of the third rectifying diode D 3 is connected to one end of the third output capacitor C o3 One end of the third output capacitor C o3 The other end is connected to the other end of the secondary side of the third transformer T 3.

[0060] The fourth transformer T The output end of 4 is connected to the fourth rectifying diodeD 4. Fourth output capacitor C o4 In series, specifically: the secondary side of the fourth transformer T One end of the secondary side of 4 is connected to the anode of the fourth rectifier diode D 4, and the cathode of the fourth rectifier diode D 4 is connected to one end of the fourth output capacitor C o4 One end of the fourth output capacitor C o4 The other end is connected to the other end of the secondary side of the fourth transformer T 4.

[0061] Furthermore, the third output capacitor C o3 Is in parallel with the first output capacitor C o1 , the first load terminal, and the fourth output capacitor C o4 Is in parallel with the second output capacitor C o2 , the second load terminal.

[0062] During specific implementation, the upper switching tubes of the first half-bridge, second half-bridge, and third half-bridge of the pre-stage voltage equalization module S i1 , the third switching tube S i3 , the fifth switching tube S i5 Are synchronously turned on and off, and the lower switching tubes, the second switching tube S i2 , the fourth switching tube S i4 , the sixth switching tube S i6 Complementary conduct with the upper tubes, and the duty cycle is 0.5 for each, so as to control the first voltage equalization capacitor C i1 , the second voltage equalization capacitor C i2 , the third voltage equalization capacitor C i3 , the fourth voltage equalization capacitor C i4 To have the same voltage, that is V i1 = V i2 = V i3 = V i4 , without any special control strategy, simplifies the control system and improves stability.

[0063] The first flyback converter, the second flyback converter, the third flyback converter, and the fourth flyback converter of the post-stage output module are connected in series at the input and are respectively connected to the first voltage-sharing capacitor C i1 , the second voltage-sharing capacitor C i2 , the third voltage-sharing capacitor C i3 , and the fourth voltage-sharing capacitor C i4 . Therefore, the input voltages of the four flyback converters are respectively V i1 , V i2 , V i3 , V i4 . The first main switch tubes S 1, the second main switch tubes S 2, the third main switch tubes S 3, and the fourth main switch tubes S 4 of the four flyback converters are synchronously turned on and off under the control of a fixed-frequency PWM, and the switching period is T s .

[0064] Furthermore, by controlling the driving duty ratios S 1 of the first main switch tubes S 2, the second main switch tubes S 3, the third main switch tubes S 4, the regulation of the voltage gain of the converter is realized. Specifically: d

[0065]

[0066] In the formula, V out represents the output voltage of the flyback converter, V ix represents the input voltage of the flyback converter, where ，x=1-4， respectively represent the input terminal voltages of the first flyback converter, the second flyback converter, the third flyback converter, and the fourth flyback converter V i1 , V i2 , V i3 , V i4 ，N represents the first transformer T 1, the second transformer T 2, the third transformer T 3, and the fourth transformer T4 Primary-secondary turns ratio.

[0067] Specifically, the pre-stage voltage-sharing module has two modes in one switching cycle. Please refer to Figure 2 and Figure 3 , Figure 2 which shows the current path diagram of the first mode of the pre-stage voltage-sharing module according to an embodiment of the present invention; Figure 3 which shows the current path diagram of the second mode of the pre-stage voltage-sharing module according to an embodiment of the present invention.

[0068] In the first mode of the pre-stage voltage-sharing module, the upper switches of the first half-bridge, the second half-bridge, and the third half-bridge, the first switching tube S i1 , the third switching tube S i3 , the fifth switching tube S i5 are turned on. Within this mode, the currents of the first inductor L i1 , the second inductor L i2 , and the third inductor L i3 continue to rise and store energy.

[0069] In the second mode of the pre-stage voltage-sharing module, the lower switches of the first half-bridge, the second half-bridge, and the third half-bridge, the second switching tube S i2 , the fourth switching tube S i4 , the sixth switching tube S i6 are turned on. Within this mode, the currents of the first inductor L i1 , the second inductor L i2 , and the third inductor L i3 begin to decline and release energy.

[0070] The conduction times of the upper and lower switches in the first half-bridge, the second half-bridge, and the third half-bridge are the same. Therefore, the durations of the first mode and the second mode of the pre-stage voltage-sharing module are the same. The first half-bridge composed of the first switching tube S i1 , the second switching tube S i2 ensures the voltage sharing of the first voltage-sharing capacitor C i1 , the second voltage-sharing capacitor C i2 ; the third switching tube S i3 , the fourth switching tube S i4The second half-bridge composed ensures the voltage sharing of the third voltage-sharing capacitor C i3 and the fourth voltage-sharing capacitor C i4 ; The third half-bridge composed of the fifth switching transistor S i5 and the sixth switching transistor S i6 ensures the voltage sharing of the second voltage-sharing capacitor C i2 and the third voltage-sharing capacitor C i3 , thereby ensuring that the high input voltage V i is evenly divided and transferred to the first voltage-sharing capacitor C i1 , the second voltage-sharing capacitor C i2 , the third voltage-sharing capacitor C i3 , and the fourth voltage-sharing capacitor C i4 and then transferred to the subsequent output module, reducing the voltage stress of the components in the subsequent circuit.

[0071] Specifically, the subsequent output module has two modes in one switching cycle. Please refer to Figure 4 and Figure 5 , Figure 4 shows the current path diagram of the first mode of the subsequent output module according to the embodiment of the present invention; Figure 5 shows the current path diagram of the second mode of the subsequent output module according to the embodiment of the present invention.

[0072] In the first mode of the subsequent output module, the first main switching transistor S 1, the second main switching transistor S 2, the third main switching transistor S 3, and the fourth main switching transistor S 4 are turned on. In this mode, the voltage C i1 output by the first voltage-sharing capacitor V i1 , the voltage C i2 output by the second voltage-sharing capacitor V i2 , the voltage C i3 output by the third voltage-sharing capacitor V i3 , and the voltage C i4 output by the fourth voltage-sharing capacitor V i4 respectively excite the input inductance of the first transformer T 1L m1 , the second transformer T The exciting inductance of the input terminal of 2 L m2 , the third transformer T The exciting inductance of the input terminal of 3 L m3 , the fourth transformer T The exciting inductance of the input terminal of 4 L m4 is charged. The first rectifying diode D 1, the second rectifying diode D 2, the third rectifying diode D 3, the fourth rectifying diode D 4 is cut off, and the energy is stored in the first transformer T 1, the second transformer T 2, the third transformer T 3, the fourth transformer T 4.

[0073] In the second mode of the post-stage output module, the first main switch tube S 1, the second main switch tube S 2, the third main switch tube S 3, the fourth main switch tube S 4 is turned off. In this mode, the exciting inductance of the input terminal of the first transformer T 1 L m1 , the second transformer T 2 L m2 , the third transformer T 3 L m3 , the fourth transformer T 4 L m4 discharges. The first rectifying diode D 1, the second rectifying diode D 2, the third rectifying diode D 3, the fourth rectifying diode D 4 conducts, and the energy is transferred to the first load terminal and the second load terminal through the first transformer T 1, the second transformer T 2, the third transformer T 3, the fourth transformer T 4.

[0074] In the embodiment of the present invention, the pre-stage voltage equalization module divides the high input voltage of the power supply equally to the first voltage equalization capacitor C i1 , the second voltage equalization capacitorC i2 , the third voltage-sharing capacitor C i3 , the fourth voltage-sharing capacitor C i4 , so the first main switching transistors of the four flyback converters at the later stage S 1. The second main switching transistor S 2. The third main switching transistor S 3. The fourth main switching transistor S 4. The voltage stress is V Sm :

[0075] V Sm= V ix + NV om

[0076] In the formula, m = 1, 2, V S1 represents the voltage stress of the first main switching transistor S 1. The third main switching transistor S 3. The voltage stress; V S2 represents the voltage stress of the second main switching transistor S 2. The fourth main switching transistor S 4. The voltage stress; V ix represents the input voltage of the flyback converter, where ，x=1-4， respectively represent the input terminal voltages of the first flyback converter, the second flyback converter, the third flyback converter, and the fourth flyback converter V i1 , V i2 , V i3 , V i4 ，N represents the first transformer T 1. The second transformer T 2. The third transformer T 3. The fourth transformer T 4. The turns ratio of the primary and secondary sides ，V om represents the load terminal voltage, V o1 represents the first load terminal voltage, V o2 represents the second load terminal voltage.

[0077] It should be noted that the first load terminal voltage V o1 and the second load terminal voltageV o2 When they are different, it is used for multiple outputs.

[0078] In the embodiment of the present invention, the low-power combined flyback converter with a voltage equalization module reduces the voltage stress of the output circuit devices, and converts the high input voltage V i into a low voltage V o1 and V o2 outputs, and processes the high input voltage through low-voltage power semiconductor devices.

[0079] In addition, the low-power combined flyback converter with a voltage equalization module of the present invention in the embodiment of the present invention can achieve input voltage equalization without any special control strategy, simplifies the control system, and improves the stability.

[0080] Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A combined flyback converter with a voltage equalizing module, characterized in that, Comprising: A pre-stage voltage equalization module and a post-stage output module; Among them, the pre-stage voltage equalization module includes a power supply, and the post-stage output module includes a first load terminal and a second load terminal; the pre-stage voltage equalization module is used to perform voltage equalization processing on the input voltage of the power supply port and then input it to the post-stage output module; the post-stage output module is used to perform conversion processing on the voltage after voltage equalization and output it externally through the first load terminal and the second load terminal; The pre-stage voltage equalization module further includes a first switching transistor Si1, a second switching transistor Si2, a third switching transistor Si3, a fourth switching transistor Si4, a fifth switching transistor Si5, a sixth switching transistor Si6, a first inductor Li1, a second inductor Li2, a third inductor Li3, a first voltage equalization capacitor Ci1, a second voltage equalization capacitor Ci2, a third voltage equalization capacitor Ci3, and a fourth voltage equalization capacitor Ci4; Among them, the drain of the first switching transistor Si1 is connected to the positive pole of the power supply, the source of the first switching transistor Si1 is connected to the drain of the second switching transistor Si2, the drain of the third switching transistor Si3 is connected to the source of the second switching transistor Si2, the source of the third switching transistor Si3 is connected to the drain of the fourth switching transistor Si4, the source of the fourth switching transistor Si4 is connected to the negative pole of the power supply, and the source of the fifth switching transistor Si5 is connected to the drain of the sixth switching transistor Si6; the first end of the first inductor Li1 is connected to the source of the first switching transistor Si1 and the drain of the second switching transistor Si2, and the second end of the first inductor Li1 is connected to one end of the first voltage equalization capacitor Ci1 and one end of the second voltage equalization capacitor Ci2; the first end of the second inductor Li2 is connected to the source of the third switching transistor Si3 and the drain of the fourth switching transistor Si4, and the second end of the second inductor Li2 is connected to one end of the third voltage equalization capacitor Ci3 and one end of the fourth voltage equalization capacitor Ci4; the first end of the third inductor Li3 is connected to the source of the fifth switching transistor Si5 and the drain of the sixth switching transistor Si6, and the second end of the third inductor Li3 is connected to the source of the second switching transistor Si2 and the drain of the third switching transistor Si3, and the second end of the third inductor Li3 is further connected to one end of the second voltage equalization capacitor Ci2 and one end of the third voltage equalization capacitor Ci3.

2. The combined flyback converter with a voltage equalizing module according to claim 1, wherein, The post-stage output module further includes a first flyback converter, a second flyback converter, a third flyback converter, and a fourth flyback converter; Among them, the input ends of the first flyback converter, the second flyback converter, the third flyback converter, and the fourth flyback converter are connected in series and then respectively connected to the first voltage-sharing capacitor C i1 , the second voltage-sharing capacitor C i2 , the third voltage-sharing capacitor C i3 , and the fourth voltage-sharing capacitor C i4 respectively.

3. The combined flyback converter with a voltage equalizing module according to claim 2, wherein, The input terminal of the first flyback converter includes a first transformer T The exciting inductance of the input terminal of 1 L m1 and a first switching transistor S i1 The input terminal of the second flyback converter includes a second transformer T The exciting inductance of the input terminal of 2 L m2 and a second switching transistor S i2 The input terminal of the third flyback converter includes a third transformer T The exciting inductance of the input terminal of 3 L m3 and a third main switching transistor S 3. The input terminal of the fourth flyback converter includes a fourth transformer T The exciting inductance of the input terminal of 4 L m4 and a fourth main switching transistor S 4; Among them, the first transformer T The exciting inductance of the input end of 1 L m1 One end is connected to the positive pole of the power supply, the drain of the first switching tube S i1 And one end of the first voltage-sharing capacitor C i1 One end of the exciting inductance of the input end of the first transformer 1 T The exciting inductance of the input end of 1 L m1 The other end is connected to the drain of the first main switching tube 1 S The source of the first main switching tube 1 is connected to the exciting inductance of the input end of the second transformer 2 S 2 T The exciting inductance of the input end of 2 L m2 One end of the exciting inductance of the input end of the second transformer 2 T The exciting inductance of the input end of 2 L m2 The other end is connected to the drain of the second main switching tube 2 S 2 S The source of the second main switching tube 2 is connected to the exciting inductance of the input end of the third transformer 3 T 3 L m3 One end of the exciting inductance of the input end of the third transformer 3 T The exciting inductance of the input end of 3 L m3 The other end is connected to the drain of the third main switching tube 3 S 3 S The source of the third main switching tube 3 is connected to the exciting inductance of the input end of the fourth transformer 4 T 4 L m4 One end of the exciting inductance of the input end of the fourth transformer 4 T The exciting inductance of the input end of 4 L m4 The other end is connected to the drain of the fourth main switching tube 4 S 4 S The source of the fourth main switching tube 4 is connected to the negative pole of the power supply, the source of the fourth switching tube S i1 And one end of the fourth voltage-sharing capacitor C i4 Are connected at one end.

4. The combined flyback converter with a voltage equalizing module according to claim 3, characterized in that, The first inductor L i1 The second end is also connected to the source electrode of the first main switch tube S 1, the exciting inductor at the input end of the second transformer T 2 L m2 One end is connected; the second inductor L i2 The second end is also connected to the source electrode of the third main switch tube S 3, the exciting inductor at the input end of the fourth transformer T 4 L m4 One end is connected; the third inductor L i3 The second end is also connected to the source electrode of the second main switch tube S 2, the exciting inductor at the input end of the third transformer T 3 L m3 One end is connected.

5. The combined flyback converter with a voltage equalizing module according to claim 3, characterized in that, The first flyback converter further includes a first rectifying diode D 1. First output capacitor C o1 ; Among them, the first transformer T One end of the secondary side of 1 is connected to the anode of the first rectifying diode D 1, and the cathode of the first rectifying diode D 1 is connected to one end of the first output capacitor C o1 One end, and the other end of the first output capacitor C o1 is connected to the other end of the secondary side of the first transformer T 1.

6. The combined flyback converter with a voltage equalizing module according to claim 3, characterized in that, The second flyback converter further includes a second rectifying diode D 2. Second output capacitor C o2 ; Among them, the second transformer T One end of the secondary side of 2 is connected to the anode of the second rectifying diode D 2, and the cathode of the second rectifying diode D 2 is connected to one end of the second output capacitor C o2 One end of the second output capacitor C o2 The other end is connected to the other end of the secondary side of the second transformer T 2.

7. The combined flyback converter with a voltage equalizing module according to claim 3, characterized in that, The third flyback converter further includes a third rectifying diode D 3. The third output capacitor C o3 ; Among them, the third transformer T One end of the secondary side of 3 is connected to the anode of the third rectifying diode D 3, and the cathode of the third rectifying diode D 3 is connected to one end of the third output capacitor C o3 One end of the third output capacitor C o3 The other end is connected to the other end of the secondary side of the third transformer T 3.

8. The combined flyback converter with a voltage equalizing module according to claim 3, characterized in that, The fourth flyback converter further includes a fourth rectifying diode D 4. Fourth output capacitor C o4 ; Among them, the fourth transformer T One end of the secondary side of 4 is connected to the anode of the fourth rectifying diode D 4, and the cathode of the fourth rectifying diode D 4 is connected to one end of the fourth output capacitor C o4 One end of the fourth output capacitor C o4 The other end is connected to the other end of the secondary side of the fourth transformer T 4.

9. The combined flyback converter with a voltage equalizing module according to any one of claims 1-8, characterized in that, In one switching cycle, the pre-stage voltage equalization module includes a first mode of the pre-stage voltage equalization module and a second mode of the pre-stage voltage equalization module; First-stage voltage equalization module first mode: first switching transistor S i1 , third switching transistor S i3 , fifth switching transistor S i5 turn on, the current of the first inductor L i1 , second inductor L i2 , third inductor L i3 continues to rise and stores energy; Pre - stage voltage equalizing module second mode: second switching tube S i2 , fourth switching tube S i4 , sixth switching tube S i6 turn on, and the current of the first inductor L i1 , second inductor L i2 , third inductor L i3 starts to decline and releases energy.

10. The combined flyback converter with a voltage equalizing module according to any one of claims 3-8, characterized in that In one switching cycle, the post-stage output module includes a first mode of the post-stage output module and a second mode of the post-stage output module; Post-stage output module first mode: First main switch transistor S 1. Second main switch transistor S 2. Third main switch transistor S 3. Fourth main switch transistor S 4 turns on, the first equalizing capacitor C i1 The output voltage V i1 and the second equalizing capacitor C i2 The output voltage V i2 and the third equalizing capacitor C i3 The output voltage V i3 and the fourth equalizing capacitor C i4 The output voltage V i4 respectively charge the exciting inductance at the input of the first transformer T 1, the exciting inductance at the input of the second transformer L m1 2, the exciting inductance at the input of the third transformer T 3, the exciting inductance at the input of the fourth transformer L m2 4, and the exciting inductance at the input of the fourth transformer T 4, the exciting inductance at the input of the fourth transformer L m3 4, and store the energy in the first transformer T 1, the second transformer L m4 2, the third transformer T 3, the fourth transformer T 2, the third transformer T 3, the fourth transformer T 4; Second Mode of the Post-stage Output Module: The First Main Switching Transistor S 1. The Second Main Switching Transistor S 2. The Third Main Switching Transistor S 3. The Fourth Main Switching Transistor S 4 is turned off, and the exciting inductance of the input end of the first transformer T 1 L m1 and the second transformer T 2 L m2 and the third transformer T 3 L m3 and the fourth transformer T 4 L m4 discharge, and the energy is transferred to the first load terminal and the second load terminal through the first transformer T 1, the second transformer T 2, the third transformer T 3, the fourth transformer T 4 11. The combined flyback converter with a voltage equalizing module according to claim 10, wherein By controlling the first main switch S 1. The second main switch S 2. The third main switch S 3. The fourth main switch S 4. The driving duty cycle d , the voltage gain of the converter is specifically achieved as follows: Wherein, V out represents the output voltage of the flyback converter, V ix represents the input voltage of the flyback converter, where ，x=1-4， respectively represent the input terminal voltages of the first flyback converter, the second flyback converter, the third flyback converter, and the fourth flyback converter V i1 , V i2 , V i3 , V i4 ，N represents the first transformer T 1, the second transformer T 2, the third transformer T 3, the fourth transformer T 4, the turns ratio of the primary and secondary windings.

12. The combined flyback converter with a voltage equalizing module according to claim 10, characterized in that, The first main switching transistor S 1. The second main switching transistor S 2. The third main switching transistor S 3. The fourth main switching transistor S 4. The voltage stress is V Sm : V Sm= V ix + NV om Wherein, m = 1, 2, V S1 represents the first main switch tube S 1, the third main switch tube S 3 voltage stresses; V S2 represents the second main switch tube S 2, the fourth main switch tube S 4 voltage stresses; V ix represents the input voltage of the flyback converter, where ，x=1-4， respectively represent the input voltages of the first flyback converter, the second flyback converter, the third flyback converter, and the fourth flyback converter V i1 , V i2 , V i3 , V i4 ，N represents the first transformer T 1, the second transformer T 2, the third transformer T 3, the fourth transformer T 4 turns ratio of the primary and secondary windings ，V om represents the load terminal voltage, V o1 represents the first load terminal voltage, V o2 represents the second load terminal voltage.

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