Power converter

Abstract

The invention discloses a power converter, which is a magnetic integrated current doubling rectifying circuit with a low transformer transformation ratio, and can not only improve the effective duty ratio of a system, but also reduce the gain of the circuit by adjusting the connection mode of a synchronous rectifying tube and a corresponding bridge arm. Therefore, the power converter can reduce the turn ratio of the transformer under the condition of the same output voltage, thereby reducing the loss of the transformer and reducing the cost of the transformer.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and more particularly to a power converter. Background Art

[0002] In order to obtain a higher system conversion efficiency, the prior art often uses a two-phase half-bridge current doubler circuit and a two-phase full-bridge current doubler circuit for power conversion.

[0003] In the two-phase half-bridge current doubler circuit, as shown in FIG1(a), transistors Q1, Q2, Q3 and Q4 are all main switch tubes. When they are turned on, the transformer is excited. When they are turned off, the corresponding rectifier tubes SR1-SR4 are turned on to output the excitation energy for demagnetization. In this scheme, since transistors Q1 and Q2 belong to the same half-bridge circuit, transistors Q1 and Q2 cannot be turned on at the same time, that is, the duty cycle range of the two-phase half-bridge circuit is 0-50%.

[0004] In the two-phase full-bridge current doubler circuit, as shown in Figure 1(b), transistors Q1 and Q3 are the main switch tubes. When they are turned on, the transformer is excited. When they are turned off, the corresponding rectifier tubes SR1 and SR2 and the lower switch tubes (Q2 and Q4) of the corresponding bridge arm are turned on for demagnetization. In this scheme, when the duty cycle is less than 50%, its output voltage is (D / N)*V in , where D is the duty cycle and N is the turns ratio of the transformer; if the duty cycle is greater than 50%, there will be a mode in which the main switches Q1 and Q3 are turned on at the same time. At this time, the rectifier switches SR1 and SR2 are both turned off, so the excitation current will flow through the body diode, which will increase the loss and is not conducive to improving the system efficiency. When the duty cycle is greater than 50%, the mode in which the main switches Q1 and Q3 are turned on at the same time and the mode in which the lower switches Q2 and Q4 are turned on at the same time are symmetrical. Therefore, when the duty cycle is greater than 50%, the output voltage of the circuit is [(1-D) / N]*V in , the voltage gain cannot be further adjusted. Summary of the invention

[0005] In view of this, the present invention provides a power converter, which is a magnetic integrated current doubler rectifier circuit with a low transformer ratio. The circuit can improve the effective duty cycle of the system and reduce the gain of the circuit by adjusting the connection mode between the synchronous rectifier and the corresponding bridge arm. The power converter can reduce the turns ratio of the transformer under the same output voltage, thereby reducing the transformer loss and the cost of the transformer.

[0006] The present invention provides a power converter, characterized in that it comprises:

[0007] M transformer units, each of which includes a primary winding and a secondary winding, and M is an integer not less than 3; and

[0008] M bridge arms, each bridge arm is coupled between two input terminals of a DC input voltage, and each bridge arm includes an upper switch tube, a lower switch tube and a synchronous rectifier tube connected in series;

[0009] Among them, the same-name end of each primary winding is connected to the common node of the upper switch tube and the lower switch tube in a corresponding bridge arm, and the non-same-name end of each primary winding is connected to the same common node; and one end of each secondary winding is connected to the common node of the lower switch tube and the synchronous rectifier tube in different bridge arms, and the other end of each secondary winding is connected to an output end of the power converter.

[0010] Preferably, each of the bridge arms is coupled to a primary winding and a secondary winding in a different transformer unit.

[0011] Preferably, the i-th bridge arm includes an i-th upper switch tube, an i-th lower switch tube and an i+1-th synchronous rectifier tube connected in series, the same-name end of the i-th primary winding is connected to the common node of the i-th upper switch tube and the i-th lower switch tube, and the same-name end of the i+1-th secondary winding is connected to the common node of the i+1-th synchronous rectifier tube and the i-th lower switch tube, where i is a natural number less than M.

[0012] Preferably, the i-th bridge arm includes an i-th upper switch tube, an i-th lower switch tube and a first synchronous rectifier tube connected in series, the same-name end of the i-th primary winding is connected to the common node of the i-th upper switch tube and the i-th lower switch tube, and the same-name end of the first secondary winding is connected to the common node of the first synchronous rectifier tube and the i-th lower switch tube, where i is equal to M.

[0013] Preferably, the conduction time of each of the upper switch tubes is the same, and there is a phase difference of 360° / M in sequence, each of the secondary rectifier tubes is complementarily conducted with the upper switch tube with the same number as it, and each of the lower switch tubes is turned on when the upper switch tube and the synchronous rectifier tube on the bridge arm where it is located are turned off.

[0014] Preferably, each of the bridge arms is coupled to a primary winding and a secondary winding in the same transformer unit.

[0015] Preferably, the i-th bridge arm includes an i-th upper switch tube, an i-th lower switch tube and an i-th synchronous rectifier tube connected in series, the like-name end of the i-th primary winding is connected to the common node of the i-th upper switch tube and the i-th lower switch tube, and the non-like-name end of the i-th secondary winding is connected to the common node of the i-th lower switch tube and the i-th synchronous rectifier tube, wherein i is a natural number not less than M.

[0016] Preferably, the conduction time of each of the lower switch tubes is the same, and there is a phase difference of 360° / M in sequence, each of the secondary rectifier tubes is complementarily conducted with the lower switch tube with the same number, and each of the upper switch tubes is complementarily conducted with the lower switch tube with the same number.

[0017] Preferably, the duty cycles of the upper switch tubes or the lower switch tubes in the M bridge arms are the same, and the maximum duty cycle is 1-1 / M.

[0018] Preferably, the voltage conversion ratio of the power converter is the ratio of the duty cycle to the sum of the turns ratio of the transformer unit and 1, the turns ratio of the transformer unit is the ratio of the number of turns of the primary winding to the number of turns of the secondary winding, wherein the M transformer units have the same turns ratio, wherein the duty cycle is the ratio of the conduction time of the upper switch tube or the lower switch tube to the switching period. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0020] FIG1 is a schematic diagram of a power converter in the prior art;

[0021] Figure 2 is a schematic diagram of a power converter according to a first embodiment of the present invention;

[0022] FIG3 is a driving timing diagram of the power converter according to the first embodiment of the present invention;

[0023] Figure 4 is a schematic diagram of a power converter according to a second embodiment of the present invention;

[0024] FIG5 is a driving timing diagram of a power converter according to a second embodiment of the present invention;

[0025] Figure 6 is a schematic diagram of a power converter according to a third embodiment of the present invention;

[0026] Figure 7 FIG. 4 is a schematic diagram of a power converter according to a fourth embodiment of the present invention. DETAILED DESCRIPTION

[0027] The present invention is described below based on embodiments, but the present invention is not limited to these embodiments. In the detailed description of the present invention below, some specific details are described in detail. It is possible for a person skilled in the art to fully understand the present invention without the description of these details. In order to avoid confusing the essence of the present invention, known methods, processes, flows, components and circuits are not described in detail.

[0028] In addition, persons of ordinary skill in the art will appreciate that the drawings provided herein are for illustration purposes and are not necessarily drawn to scale.

[0029] At the same time, it should be understood that in the following description, "circuit" refers to a conductive loop composed of at least one element or subcircuit through electrical connection or electromagnetic connection. When an element or circuit is said to be "connected to" another element or an element / circuit is said to be "connected between" two nodes, it can be directly coupled or connected to another element or there can be an intermediate element, and the connection between the elements can be physical, logical, or a combination thereof. On the contrary, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there is no intermediate element between the two.

[0030] Unless the context clearly requires otherwise, throughout the specification and claims, the words "include", "comprising" and similar words should be interpreted in an inclusive sense rather than an exclusive or exhaustive sense; that is, in the sense of "including but not limited to".

[0031] In the description of the present invention, it should be understood that the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0032] Figure 2 FIG. 1 is a schematic diagram of a power converter according to a first embodiment of the present invention. Figure 2 As shown, the power converter of this embodiment is described by taking a structure based on three transformer units as an example, which includes three transformer units and three bridge arms.

[0033] Specifically, each transformer unit includes a primary winding and a secondary winding, and each bridge arm is coupled to a DC input voltage V in between two input ends, and each bridge arm includes an upper switch tube, a lower switch tube and a synchronous rectifier tube connected in series.

[0034] More specifically, the same-name end of each primary winding is connected to a common node of a corresponding upper switch tube and a lower switch tube, and the non-same-name end of each primary winding is connected to the same common node; and the same-name end of each secondary winding is connected to a common node of a different lower switch tube and a synchronous rectifier tube, and the non-same-name end of each secondary winding is connected to the same common node, and the common node is connected to the non-grounded output terminal of the power converter, and an output voltage V is generated at the output terminal. o .

[0035] In one embodiment, each bridge arm is coupled to a primary winding and a secondary winding in a different transformer unit. In another embodiment, each bridge arm is coupled to a primary winding and a secondary winding in a same transformer unit.

[0036] In the embodiment of the present invention, the transformer unit T1 includes a primary winding P1 and a secondary winding S1, the transformer unit T2 includes a primary winding P2 and a secondary winding S2, and the transformer unit T3 includes a primary winding P3 and a secondary winding S3. Each bridge arm is coupled to the primary winding and the secondary winding in different transformer units. The first bridge arm includes an upper switch tube Q connected in series. 1H , lower switch tube Q 1L and synchronous rectifier SR2; the second bridge arm includes an upper switch tube Q connected in series 2H , lower switch tube Q 2L and synchronous rectifier SR3; the third bridge arm includes an upper switch tube Q connected in series 3H , lower switch tube Q 3L And synchronous rectifier SR1.

[0037] It should be noted that the inductors L connected in parallel to the secondary windings S1, S2 and S3 are m1 , L m2 , L m3 It can be realized by the magnetizing inductance of the transformer unit or by an independent inductor connected in parallel externally. In actual transformers, since the magnetic core and coil are not ideal, there are many parasitic parameters. First, the magnetic permeability of the magnetic core is not infinite, so the secondary winding of the transformer can be equivalent to an ideal secondary winding and a magnetizing inductance connected in parallel. Second, the primary winding and the secondary winding of the transformer are not fully coupled, and there is also some leakage inductance, but in this application, the leakage inductance is temporarily ignored.

[0038] It should be understood that the transformer unit T1 , the transformer unit T2 and the transformer unit T3 may be three separate transformer modules respectively, or may be one transformer module integrated together in a magnetic integration manner.

[0039] Furthermore, the same-name end of the primary winding P1 of the transformer unit T1 is connected to the upper switch tube Q in the first bridge arm. 1HWith the lower switch tube Q 1L The common node of the transformer unit T1 and the same-name end of the secondary winding S1 are connected to the lower switch tube Q in the third bridge arm. 3L The common node with the synchronous rectifier SR1; the same end of the primary winding P2 of the transformer unit T2 is connected to the upper switch tube Q in the second bridge arm 2H With the lower switch tube Q 2L The common node of the transformer unit T2 and the same-name end of the secondary winding S2 are connected to the lower switch tube Q in the first bridge arm. 1L The common node with the synchronous rectifier SR2; the same end of the primary winding P3 of the transformer unit T3 is connected to the upper switch tube Q in the third bridge arm 3H With the lower switch tube Q 3L The common node of the transformer unit T3 and the same-name end of the secondary winding S3 are connected to the lower switch tube Q in the second bridge arm. 2L The non-same-named ends of all primary windings are connected to the common node g1, and the non-same-named ends of all secondary windings are connected to the output capacitor C o connect.

[0040] Figure 2 When designing the control logic of the switch tube, the upper switch tube Q in each bridge arm is used as the control logic of the switch tube. 1H , Q 2H and Q 3H The upper switch tube Q is the main switch tube. 1H , Q 2H and Q 3H The ratio of the on-time to the switching period is recorded as the duty cycle D, and all upper switch tubes Q 1H , Q 2H and Q 3H The duty cycle D and conduction time of the upper switch tube Q are the same. 1H , Q 2H , Q 3H The switch control signals have a phase difference of 120°.

[0041] Furthermore, the synchronous rectifier tubes SR1, SR2, and SR3 are respectively connected to the corresponding main switch tubes Q 1H , Q 2H , Q 3H Complementary conduction, that is, Vg_SR1 = ! Vg_Q 1H 、Vg_SR2=!Vg_Q 2H 、Vg_SR3=!Vg_Q 3HIt should be noted that the complementary conduction mentioned here is based on the ideal working condition that the related switch tubes will not be turned on at the same time, and does not take into account the situation with dead time. When there is dead time, the synchronous rectifier tubes SR1, SR2, SR3 and the corresponding main switch tube Q 1H , Q 2H , Q 3H Non-overlapping conduction. Here, Vg_SR i 、Vg_Q iH 、Vg_Q iL They are the control signals of the corresponding synchronous rectifier tube, the upper switch tube and the lower switch tube respectively.

[0042] Furthermore, the lower switch tube Q of each bridge arm 1L , Q 2L , Q 3L Then the corresponding bridge arm is turned on when the other switch tubes are turned off, that is, "Vg_Q 1L =! Vg_Q 1H &! Vg_SR2", "Vg_Q 2L =! Vg_Q 2H &! Vg_SR3", "Vg_Q 3L =! Vg_Q 3H &! Vg_SR1". That is, the lower switch tube Q 1L On the upper switch tube Q 1H When the synchronous rectifier SR2 is turned off, the lower switch Q 2L On the upper switch tube Q 2H and synchronous rectifier SR3 are turned off, the lower switch tube Q 3L On the upper switch tube Q 3H And the synchronous rectifier SR1 is turned off.

[0043] FIG3 shows a driving timing diagram of the power converter of the first embodiment. FIG3(a) mainly shows the working waveform of the transformer unit T1 when the duty cycle D is less than 1 / 3; FIG3(b) mainly shows the working waveform of the transformer unit T1 when the duty cycle D is greater than 1 / 3 and less than 2 / 3. It should be noted that in order to save space, only the working process of the first third of each working cycle T is analyzed here. Waveform I P is the current flowing through the primary winding of the transformer unit, waveform I SR is the current flowing through the synchronous rectifier, and the waveform VLm is the voltage on the inductor connected in parallel with the secondary winding. First, let's explain the working condition when the duty cycle D is less than 1 / 3, combined with Figure 3(a) and Figure 2 , in the time period of 0~DT, the upper switch tube Q 1H On, upper switch tube Q 2H , Q 3HThe current conduction path is the upper switch tube Q 1H -T1's primary winding P1 -T3's primary winding P3 - output capacitor Co, so (the transformer's same-name terminal is defined as the positive terminal):

[0044] V in =V P1 -V P3 +V S1 +V o

[0045] And the secondary windings S2, S3 and the output capacitor Co are connected in parallel, so:

[0046] V Lm2 =V Lm3 =V S2 =V S3 =-V o

[0047] Where V Si is the voltage on the ith secondary winding.

[0048] The turns ratio of the transformer is defined as Np:Ns. According to the definition of the transformer, we have:

[0049]

[0050] Then organize it into:

[0051]

[0052] It can be deduced that:

[0053]

[0054] During the period of DT to T / 3, the upper switch tube Q 1H , Q 2H , Q 3H All are turned off, and the synchronous rectifiers SR1, SR2, and SR3 are all turned on, so:

[0055] V Lm1 =V Lm2 =V Lm3 =-V o

[0056] Then we can get:

[0057]

[0058] In steady state, according to the inductor volt-second balance and combined with the above formula:

[0059]

[0060] After finishing, we can get:

[0061]

[0062] Next, the operating condition where the duty cycle D is greater than 1 / 3 and less than 2 / 3 is described, combining FIG3(b) and Figure 2 , in the time period of 0~(D-1 / 3)T, the upper switch tube Q 1H , Q 3H On, upper switch tube Q 2H Turn off, lower switch tube Q 2L The synchronous rectifier SR2 is turned on. So:

[0063] V in =V P1 -V P2 +V S3 +V o

[0064] V in =V P3 -V P2 +V S3 +V o

[0065] V P1 =V P3

[0066] Secondary winding S2 and output capacitor C O In parallel, we have:

[0067] V Lm2 =V S2 =-V o

[0068] According to the definition of transformer, we have:

[0069]

[0070] It can be deduced that:

[0071]

[0072] During the period (D-1 / 3)T~T / 3, the upper switch tube Q 1H On, upper switch tube Q 2H , Q 3H The current conduction path is the upper switch tube Q 1H -T1's primary winding P1 -T3's primary winding P3 -output capacitor Co, so:

[0073]

[0074] Then we can get:

[0075]

[0076] In steady state, according to the inductor volt-second balance and combined with the above formula, we can get:

[0077]

[0078] It can be seen that the power converter of the embodiment of the present invention adjusts the output voltage V O for Adjust the output voltage to V O for Therefore, under the condition of achieving the same output voltage, the number of turns of the primary winding of the transformer can be reduced, thereby reducing the loss and cost of the transformer.

[0079] Figure 4 FIG. 1 is a schematic diagram of a power converter according to a second embodiment of the present invention. Figure 4 As shown, the power converter of this embodiment takes a structure based on three transformer units as an example, which includes three transformer units and three bridge arms. The difference between this embodiment of the present invention and the first embodiment is that each bridge arm is only coupled to the primary winding and the secondary winding in the same transformer unit.

[0080] In the embodiment of the present invention, the transformer unit T1 includes a primary winding P1 and a secondary winding S1, the transformer unit T2 includes a primary winding P2 and a secondary winding S2, and the transformer unit T3 includes a primary winding P3 and a secondary winding S3. Each bridge arm is coupled to the primary winding and the secondary winding in the same transformer unit, and the first bridge arm includes an upper switch tube Q connected in series. 1H , lower switch tube Q 1L and synchronous rectifier SR1; the second bridge arm includes an upper switch tube Q connected in series 2H , lower switch tube Q 2L and synchronous rectifier SR2; the third bridge arm includes an upper switch tube Q connected in series 3H , lower switch tube Q 3L And synchronous rectifier SR3.

[0081] Furthermore, the same-name end of the primary winding P1 of the transformer unit T1 is connected to the upper switch tube Q in the first bridge arm. 1H With the lower switch tube Q 1L The common node of the transformer unit T1 and the non-same-name end of the secondary winding S1 are connected to the lower switch tube Q in the first bridge arm. 1L The common node with the synchronous rectifier SR1; the same end of the primary winding P2 of the transformer unit T2 is connected to the upper switch tube Q in the second bridge arm 2HWith the lower switch tube Q 2L The common node of the transformer unit T2 and the non-same-name end of the secondary winding S2 are connected to the lower switch tube Q in the second bridge arm. 2L The common node with the synchronous rectifier SR2; the same end of the primary winding P3 of the transformer unit T3 is connected to the upper switch tube Q in the third bridge arm 3H With the lower switch tube Q 3L The common node of the transformer unit T3 and the non-same-name end of the secondary winding S3 are connected to the lower switch tube Q in the third bridge arm. 3L The non-same-named ends of all primary windings are connected to the common node g1, and the non-same-named ends of all secondary windings are connected to the output capacitor C o connect.

[0082] Figure 4 When designing the control logic of the switch tube, the circuit structure shown in the figure is based on the lower switch tube Q in each bridge arm. 1L , Q 2L and Q 3L The lower switch tube Q is the main switch tube. 1L , Q 2L and Q 3L The ratio of the conduction time of the switch to the switching period is recorded as the duty cycle D, and all lower switch tubes Q 1L , Q 2L and Q 3L The duty cycle D and conduction time of the lower switch tube Q are the same. 1L , Q 2L and Q 3L The switch control signals have a phase difference of 120°.

[0083] Furthermore, the synchronous rectifier tubes SR1, SR2, and SR3 are respectively connected to the corresponding main switch tubes Q 1L , Q 2L , Q 3L Complementary conduction, that is, Vg_SR1 = ! Vg_Q 1L 、Vg_SR2=!Vg_Q 2L 、Vg_SR3=!Vg_Q 3L It should be noted that the complementary conduction mentioned here is based on the ideal working condition that the related switch tubes will not be turned on at the same time, and does not take into account the situation with dead time. When there is dead time, the synchronous rectifier tubes SR1, SR2, SR3 and the corresponding main switch tube Q 1L , Q 2L , Q 3L Non-overlapping conduction.

[0084] Furthermore, the upper switch tube Q of each bridge arm 1H , Q2H , Q 3H Then the corresponding main switch tube Q 1L , Q 2L , Q 3L Complementary conduction. That is, Vg_Q 1H =! Vg_Q 1L 、Vg_Q 2H =! Vg_Q 2L 、Vg_Q 3H =! Vg_Q 3L .

[0085] It can be seen that, on the one hand, in terms of circuit structure, the scheme of the first embodiment of the present invention has the interlacing of the primary and secondary side structures of the transformer, and a single bridge arm needs to be connected to two different transformers; while in the scheme of the second embodiment of the present invention, a single transformer is only associated with one bridge arm, which is simpler in circuit implementation; on the other hand, in terms of control method, in the scheme of the first embodiment of the present invention, the lower switch tube of each bridge arm is turned on when the other switch tubes on the corresponding bridge arm are turned off, and the lower switch tube of each bridge arm needs to adopt a more complex control method, and needs independent judgment and independent control; while the control logic of the upper switch tube in the scheme of the second embodiment of the present invention is the same as the control logic of the secondary rectifier tube SR. While subtracting the logical judgment, the corresponding control signal is also reduced, reducing the demand for the control circuit.

[0086] FIG5 shows a driving timing diagram of the power converter of the second embodiment. FIG5(a) mainly shows the working waveform of the transformer unit T1 when the duty cycle D is less than 1 / 3; FIG5(b) mainly shows the working waveform of the transformer unit T1 when the duty cycle D is greater than 1 / 3 and less than 2 / 3. It should be noted that in order to save space, only the working process of the first third of each working cycle T is analyzed here. Waveform I P is the current flowing through the primary winding of the transformer unit, waveform I SR is the current flowing through the synchronous rectifier, waveform V Lm is the voltage across the inductor connected in parallel with the secondary winding.

[0087] First, let's explain the working condition when the duty cycle D is less than 1 / 3, combined with Figure 5(a) and Figure 4 , in the time period from 0 to DT, the lower switch tube Q 1L The lower switch tube Q is turned on. 2L , Q 3L Turn off, at this time (the same-name end of the transformer is defined as the positive end, and the positive end of the inductor is opposite to that of the transformer):

[0088] V in =V P2 -V P1 -VS1 +V o

[0089] V in =V P3 -V P1 -V S1 +V o

[0090] Synchronous rectifiers SR2 and SR3 are turned on, and the secondary windings S2 and S3 and the output capacitor C O In parallel, we have:

[0091] V S2 =V S3 =V o V Lm2 =V Lm3 =-V o

[0092] According to the definition of transformer, we have:

[0093]

[0094] Then we can get:

[0095]

[0096] In the time period of DT to T / 3, the synchronous rectifiers SR1, SR2, and SR3 are all turned on, so:

[0097] V Lm1 =V Lm2 =V Lm3 =-V o

[0098] In steady state, according to the inductor volt-second balance and combined with the above formula, we can get:

[0099]

[0100] Next, the duty cycle D is greater than 1 / 3 and less than 2 / 3. Combining Figure 5(b) and Figure 5, in the time period of 0 to (D-1 / 3)T, the lower switch tube Q 1L , Q 3L The lower switch tube Q is turned on. 2L Turn off, and the synchronous rectifier SR2 is turned on. At this time, (the same-name end of the transformer is defined as the positive end, and the positive end of the inductor is opposite to that of the transformer):

[0101] V in =V P2 -V P1 -V S1 +V o

[0102] Vin =V P2 -V P3 -V S3 +V o

[0103] The synchronous rectifier SR2 is turned on, so that the secondary winding S2 and the output capacitor C O In parallel, we have:

[0104] V S2 =V o , V Lm2 =-V o

[0105] According to the definition of transformer, we have:

[0106]

[0107] Then we can get:

[0108]

[0109] Similarly, there are:

[0110]

[0111] In the time period of (D-1 / 3)T~T / 3, the lower switch tube Q IL The synchronous rectifiers SR2 and SR3 are turned on, the secondary windings S2 and S3 and the output capacitor C O In parallel, we have:

[0112]

[0113] In steady state, according to the inductor volt-second balance and combined with the above formula, we can get:

[0114]

[0115] It can be seen that the power converter of the embodiment of the present invention adjusts the output voltage V O for Adjust the output voltage to V O for Therefore, under the condition of achieving the same output voltage, the number of turns of the primary winding of the transformer can be reduced, thereby reducing the loss and cost of the transformer.

[0116] Figure 6 Schematic diagram of a power converter according to a third embodiment of the present invention; the power converter of this embodiment takes a structure based on four transformer units as an example, and includes four transformer units and four bridge arms.

[0117] In the embodiment of the present invention, the transformer unit T1 includes a primary winding P1 and a secondary winding S1, the transformer unit T2 includes a primary winding P2 and a secondary winding S2, and the transformer unit T3 includes a primary winding P3 and a secondary winding S3. Each bridge arm is coupled to the primary winding and the secondary winding in different transformer units. The first bridge arm includes an upper switch tube Q connected in series. 1H , lower switch tube Q 1L and synchronous rectifier SR2; the second bridge arm includes an upper switch tube Q connected in series 2H , lower switch tube Q 2L and synchronous rectifier SR3; the third bridge arm includes an upper switch tube Q connected in series 3H , lower switch tube Q 3L and synchronous rectifier SR4; the fourth bridge arm includes an upper switch tube Q connected in series 4H , lower switch tube Q 4L And synchronous rectifier SR1.

[0118] Furthermore, the same-name end of the primary winding P1 of the transformer unit T1 is connected to the upper switch tube Q in the first bridge arm. 1H With the lower switch tube Q 1L The common node of the transformer unit T1 and the same-name end of the secondary winding S1 are connected to the lower switch tube Q in the fourth bridge arm. 4L The common node with the synchronous rectifier SR1; the same end of the primary winding P2 of the transformer unit T2 is connected to the upper switch tube Q in the second bridge arm 2H With the lower switch tube Q 2L The common node of the transformer unit T2 and the same-name end of the secondary winding S2 are connected to the lower switch tube Q in the first bridge arm. 1L The common node with the synchronous rectifier SR2; the same end of the primary winding P3 of the transformer unit T3 is connected to the upper switch tube Q in the third bridge arm 3H With the lower switch tube Q 3L The common node of the transformer unit T3 and the same-name end of the secondary winding S3 are connected to the lower switch tube Q in the second bridge arm. 2L The common node of the synchronous rectifier tube SR3; the same end of the primary winding P4 of the transformer unit T4 is connected to the upper switch tube Q in the fourth bridge arm 4H With the lower switch tube Q 4L The common node of the transformer unit T4 and the same-name end of the secondary winding S4 are connected to the lower switch tube Q in the third bridge arm. 3L The non-same-named ends of all primary windings are connected to the common node g1, and the non-same-named ends of all secondary windings are connected to the output capacitor C o connect.

[0119] Figure 6When designing the control logic of the switch tube, the upper switch tube Q in each bridge arm is used as the control logic of the switch tube. 1H , Q 2H , Q 3H and Q 4H The upper switch tube Q is the main switch tube. 1H , Q 2H , Q 3H and Q 4H The ratio of the on-time to the switching period is recorded as the duty cycle D, and all upper switch tubes Q 1H , Q 2H , Q 3H and Q 4H The duty cycle D and conduction time of the upper switch tube Q are the same. 1H , Q 2H , Q 3H and Q 4H The switch control signals have a phase difference of 90°.

[0120] Furthermore, the synchronous rectifier tubes SR1, SR2, SR3, and SR4 are respectively connected to the corresponding main switch tubes Q 1H , Q 2H , Q 3H and Q 4H Complementary conduction, that is, Vg_SR1 = ! Vg_Q 1H 、Vg_SR2=!Vg_Q 2H 、Vg_SR3=!Vg_Q 3H 、Vg_SR4=! Vg_Q 4H Furthermore, the lower switch tube Q of each bridge arm 1L , Q 2L , Q 3L , Q 4L Then the corresponding bridge arm is turned on when the other switch tubes are turned off, that is, "Vg_Q 1L =! Vg_Q 1H &! Vg_SR2", "Vg_Q 2L =! Vg_Q 2H &! Vg_SR3", "Vg_Q 3L =! Vg_Q 3H &! Vg_SR4", "Vg_Q 4L =! Vg_Q 4H &! Vg_SR1". That is, the lower switch tube Q 1L On the upper switch tube Q 1H When the synchronous rectifier SR2 is turned off, the lower switch Q 2L On the upper switch tube Q 2Hand synchronous rectifier SR3 are turned off, the lower switch tube Q 3L On the upper switch tube Q 3H and synchronous rectifier SR4 are turned off, the lower switch tube Q 4L On the upper switch tube Q 4H And the synchronous rectifier SR1 is turned off.

[0121] In combination with the first and third embodiments of the present invention, it can be known that when expanded to M transformer units, the i-th bridge arm includes the i-th upper switch tube, the i-th lower switch tube and the i+1-th synchronous rectifier tube connected in series, the same-name end of the i-th primary winding is connected to the common node of the i-th upper switch tube and the i-th lower switch tube, and the same-name end of the i+1-th secondary winding is connected to the common node of the i-th synchronous rectifier tube and the i-th lower switch tube, where i is a natural number less than M.

[0122] The i-th bridge arm includes an i-th upper switch tube, an i-th lower switch tube and a first synchronous rectifier tube connected in series, the same-name end of the i-th primary winding is connected to a common node of the i-th upper switch tube and the i-th lower switch tube, and the same-name end of the first secondary winding is connected to a common node of the first synchronous rectifier tube and the i-th lower switch tube, where i is equal to M.

[0123] Each upper switch tube is a main switch tube, and their conduction time is the same, and there is a phase difference of 360° / M in sequence. Each secondary rectifier tube is complementarily conducted with the upper switch tube with the same number as it, and each lower switch tube is turned on when the upper switch tube and the synchronous rectifier tube on the bridge arm where it is located are turned off.

[0124] Figure 7 FIG. 4 is a schematic diagram of a power converter according to a fourth embodiment of the present invention. The power converter of this embodiment takes a structure based on four transformer units as an example, and includes four transformer units and four bridge arms.

[0125] In the embodiment of the present invention, the transformer unit T1 includes a primary winding P1 and a secondary winding S1, the transformer unit T2 includes a primary winding P2 and a secondary winding S2, and the transformer unit T3 includes a primary winding P3 and a secondary winding S3. Each bridge arm is coupled to the primary winding and the secondary winding in the corresponding transformer unit. The first bridge arm includes an upper switch tube Q connected in series. 1H , lower switch tube Q 1L and synchronous rectifier SR1; the second bridge arm includes an upper switch tube Q connected in series 2H , lower switch tube Q 2L and synchronous rectifier SR2; the third bridge arm includes an upper switch tube Q connected in series 3H , lower switch tube Q 3L and synchronous rectifier SR3; the fourth bridge arm includes an upper switch tube Q connected in series 4H , lower switch tube Q4L And synchronous rectifier SR4.

[0126] Furthermore, the same-name end of the primary winding P1 of the transformer unit T1 is connected to the upper switch tube Q in the first bridge arm. 1H With the lower switch tube Q 1L The common node of the transformer unit T1 and the non-same-name end of the secondary winding S1 are connected to the lower switch tube Q in the first bridge arm. 1L The common node with the synchronous rectifier SR1; the same end of the primary winding P2 of the transformer unit T2 is connected to the upper switch tube Q in the second bridge arm 2H With the lower switch tube Q 2L The common node of the transformer unit T2 and the non-same-name end of the secondary winding S2 are connected to the lower switch tube Q in the second bridge arm. 2L The common node with the synchronous rectifier SR2; the same end of the primary winding P3 of the transformer unit T3 is connected to the upper switch tube Q in the third bridge arm 3H With the lower switch tube Q 3L The common node of the transformer unit T3 and the non-same-name end of the secondary winding S3 are connected to the lower switch tube Q in the third bridge arm. 3L The common node of the synchronous rectifier tube SR3; the same end of the primary winding P4 of the transformer unit T4 is connected to the upper switch tube Q in the fourth bridge arm 4H With the lower switch tube Q 4L The common node of the transformer unit T4 and the non-same-name end of the secondary winding S4 are connected to the lower switch tube Q in the fourth bridge arm. 4L The non-same-named ends of all primary windings are connected to the common node g1, and the non-same-named ends of all secondary windings are connected to the output capacitor C o connect.

[0127] Figure 7 When designing the control logic of the switch tube, the circuit structure shown in the figure is based on the lower switch tube Q in each bridge arm. 1L , Q 2L , Q 3L and Q 4L The lower switch tube Q is the main switch tube. 1L , Q 2L , Q 3L and Q 4L The ratio of the conduction time of the switch to the switching period is recorded as the duty cycle D, and all lower switch tubes Q 1L , Q 2L , Q 3L and Q 4L The duty cycle D and conduction time of the lower switch tube Q are the same. 1L , Q 2L , Q 3L and Q 4LThe switch control signals have a phase difference of 90°.

[0128] Furthermore, the synchronous rectifier tubes SR1, SR2, SR3, SR4 and the corresponding main switch tubes Q 1L , Q 2L , Q 3L , Q 4L Complementary conduction, that is, Vg_SR1 = ! Vg_Q 1L 、Vg_SR2=!Vg_Q 2L 、Vg_SR3=!Vg_Q 3L 、Vg_SR4=! Vg_Q 4L Furthermore, the upper switch tube Q of each bridge arm 1H , Q 2H , Q 3H , Q 4H Then the corresponding main switch tube Q 1L , Q 2L , Q 3L , Q 4L Complementary conduction. That is, Vg_Q 1H =! Vg_Q 1L 、Vg_Q 2H =! Vg_Q 2L 、Vg_Q 3H =! Vg_Q 3L 、Vg_Q 4H =! Vg_Q 4L .

[0129] In combination with the second and fourth embodiments, it can be seen that when expanded to M transformer units, the i-th bridge arm includes the i-th upper switch tube, the i-th lower switch tube and the i-th synchronous rectifier tube connected in series, the like-name end of the i-th primary winding is connected to the common node of the i-th upper switch tube and the i-th lower switch tube, and the non-like-name end of the i-th secondary winding is connected to the common node of the i-th lower switch tube and the i-th synchronous rectifier tube, where i is a natural number not greater than M.

[0130] Each lower switch tube serves as a main switch tube, has the same conduction time, and has a phase difference of 360° / M in sequence. Each of the secondary rectifier tubes is complementarily conducted with the lower switch tube with the same number, and each of the upper switch tubes is complementarily conducted with the lower switch tube with the same number.

[0131] It can be seen that the power converter of the present invention is a magnetic integrated current doubler rectifier circuit with a low transformer ratio. By adjusting the connection method between the synchronous rectifier and the corresponding bridge arm, the effective duty cycle of the system can be improved while reducing the gain of the circuit. The power converter of the embodiment of the present application can reduce the turns ratio of the transformer under the same output voltage, thereby reducing transformer losses and reducing the cost of the transformer.

[0132] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A power converter, characterized in that: include: M transformer units, each of which includes a primary winding and a secondary winding, and M is an integer not less than 3; as well as M bridge arms, each bridge arm is coupled between two input terminals of a DC input voltage, and each bridge arm includes an upper switch tube, a lower switch tube and a synchronous rectifier tube connected in series; Among them, the same-name end of each primary winding is connected to the common node of the upper switch tube and the lower switch tube in a corresponding bridge arm, and the non-same-name end of each primary winding is connected to the same common node; and one end of each secondary winding is connected to the common node of the lower switch tube and the synchronous rectifier tube in different bridge arms, and the other end of each secondary winding is connected to an output end of the power converter.

2. The power converter according to claim 1, characterized in that: Each of the bridge arms is coupled to a primary winding and a secondary winding in a different transformer unit.

3. The power converter according to claim 2, characterized in that: The i-th bridge arm includes an i-th upper switch tube, an i-th lower switch tube and an i+1-th synchronous rectifier tube connected in series, the same-name end of the i-th primary winding is connected to the common node of the i-th upper switch tube and the i-th lower switch tube, and the same-name end of the i+1-th secondary winding is connected to the common node of the i+1-th synchronous rectifier tube and the i-th lower switch tube, where i is a natural number less than M.

4. The power converter according to claim 2, wherein: The i-th bridge arm includes an i-th upper switch tube, an i-th lower switch tube and a first synchronous rectifier tube connected in series, the same-name end of the i-th primary winding is connected to the common node of the i-th upper switch tube and the i-th lower switch tube, and the same-name end of the first secondary winding is connected to the common node of the first synchronous rectifier tube and the i-th lower switch tube, where i is equal to M.

5. The power converter according to claim 3 or 4, characterized in that: The conduction time of each upper switch tube is the same, and there is a phase difference of 360° / M in sequence. Each secondary rectifier tube is complementarily conducted with the upper switch tube with the same number as it, and each lower switch tube is turned on when the upper switch tube and the synchronous rectifier tube on the bridge arm where it is located are turned off.

6. The power converter according to claim 1, wherein: Each of the bridge arms is coupled to the primary winding and the secondary winding in the same transformer unit.

7. The power converter according to claim 6, characterized in that: The i-th bridge arm includes an i-th upper switch tube, an i-th lower switch tube and an i-th synchronous rectifier tube connected in series, the same-name end of the i-th primary winding is connected to the common node of the i-th upper switch tube and the i-th lower switch tube, and the non-same-name end of the i-th secondary winding is connected to the common node of the i-th lower switch tube and the i-th synchronous rectifier tube, wherein i is a natural number not less than M.

8. The power converter according to claim 6, characterized in that: The conduction time of each lower switch tube is the same, and there is a phase difference of 360° / M in sequence. Each secondary rectifier tube is complementarily conducted with the lower switch tube with the same number, and each upper switch tube is complementarily conducted with the lower switch tube with the same number.

9. The power converter according to claim 1, wherein: The duty cycles of the upper switch tubes or the lower switch tubes in the M bridge arms are the same, and the maximum duty cycle is 1-1 / M.

10. The power converter according to claim 9, characterized in that: The voltage conversion ratio of the power converter is the ratio of the duty cycle to the sum of the turns ratio of the transformer unit and 1, the turns ratio of the transformer unit is the ratio of the number of turns of the primary winding to the number of turns of the secondary winding, wherein the M transformer units have the same turns ratio, wherein the duty cycle is the ratio of the conduction time of the upper switch tube or the lower switch tube to the switching period.

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