Isolated DC-DC converter

Abstract

The present case relates to an isolated DC-DC converter, comprising n conversion circuit units, wherein the connection point between the two first switching elements of the first primary bridge arm of the primary circuit unit forms a first connection point, the connection point between the two first electronic elements of the second primary bridge arm forms a second connection point, the connection point between the two second switching elements of the first secondary bridge arm of the secondary circuit unit forms a third connection point, and the connection point between the two second switching elements of the second secondary bridge arm forms a fourth connection point, the first coupling inductor and the first capacitor are coupled in series between the first connection point and the third connection point, the second coupling inductor and the second capacitor are coupled in series between the second connection point and the fourth connection point, the first coupling inductor and the second coupling inductor are coupled to each other, each primary circuit unit of the n conversion circuit units is connected in one of a series connection and a parallel connection, and each secondary circuit unit of the n conversion circuit units is connected in another of a series connection and a parallel connection.

Description

Technical Field

[0001] This case relates to a DC-DC converter, and particularly to an isolated DC-DC converter. Background Art

[0002] Traditional DC-DC (Direct current to Direct current) converters use transformers for isolation to meet insulation requirements. However, with the increase in the operating frequency and power density of DC-DC converters, the limitations of transformers in DC-DC converters have become more prominent. For example, the volume of the transformer is relatively large, resulting in a decrease in the power density of the DC-DC converter; and the number of turns of the transformer has a lower limit, making the design of the DC-DC converter difficult; in addition, the loss of the transformer is relatively large, resulting in a relatively high overall loss of the DC-DC converter; even more, the heat dissipation capacity of the transformer is relatively low, resulting in a relatively low overall heat dissipation capacity of the DC-DC converter. Therefore, it is difficult to improve the overall efficiency and power density of traditional DC-DC converters using transformers for isolation.

[0003] Therefore, how to develop a converter to solve the problems faced by the prior art is an urgent issue that needs to be addressed in this field. Summary of the Invention

[0004] The purpose of this case is to provide an isolated DC-DC converter, which has the advantages of a relatively small volume, relatively low loss, and relatively high heat dissipation capacity.

[0005] To achieve the above object, a preferred embodiment of the present disclosure provides an isolated DC-DC converter including n conversion circuit units, where n is an integer greater than or equal to 2. Each conversion circuit unit includes a primary circuit unit, a secondary circuit unit, a first coupled inductor, a first capacitor, a second coupled inductor, and a second capacitor. The primary circuit unit includes a first primary bridge arm and a second primary bridge arm connected in parallel. The first primary bridge arm includes two first switching elements connected in series. The connection point between the two first switching elements of the first primary bridge arm forms a first connection point. The second primary bridge arm includes two first electronic elements connected in series. The connection point between the two first electronic elements of the second primary bridge arm forms a second connection point. The secondary circuit unit includes a first secondary bridge arm and a second secondary bridge arm connected in parallel. The first secondary bridge arm and the second secondary bridge arm respectively include two second switching elements connected in series. The connection point between the two second switching elements of the first secondary bridge arm forms a third connection point. The connection point between the two second switching elements of the second secondary bridge arm forms a fourth connection point. The first coupled inductor and the first capacitor are serially coupled between the first connection point and the third connection point. The second coupled inductor and the second capacitor are serially coupled between the second connection point and the fourth connection point, where the first coupled inductor and the second coupled inductor are mutually coupled. Each primary circuit unit of the n conversion circuit units is connected in one of series and parallel, and each secondary circuit unit of the n conversion circuit units is connected in the other of series and parallel.

[0006] To achieve the above object, another preferred embodiment of the present disclosure provides an isolated DC-DC converter including n conversion circuit units, where n is an integer greater than or equal to 2. Each conversion circuit unit includes a primary circuit unit, a secondary circuit unit, a first coupled inductor, a first capacitor, a second coupled inductor, and a second capacitor. The primary circuit unit includes a primary bridge arm, and the primary bridge arm includes two first switching elements connected in series. The connection point between the two first switching elements forms a first connection point, and a second connection point is formed between one of the two first switching elements and the input terminal. The secondary circuit unit includes a first secondary bridge arm and a second secondary bridge arm connected in parallel. The first secondary bridge arm and the second secondary bridge arm respectively include two second switching elements connected in series. The connection point between the two second switching elements of the first secondary bridge arm forms a third connection point. The connection point between the two second switching elements of the second secondary bridge arm forms a fourth connection point. The first coupled inductor and the first capacitor are serially coupled between the first connection point and the third connection point. The second coupled inductor and the second capacitor are serially coupled between the second connection point and the fourth connection point, where the first coupled inductor and the second coupled inductor are mutually coupled. Each primary circuit unit of the n conversion circuit units is connected in one of series and parallel, and each secondary circuit unit of the n conversion circuit units is connected in the other of series and parallel. Description of the Drawings

[0007] Figure 1 This is the circuit topology diagram of the isolated DC-DC converter according to the first embodiment of the present disclosure.

[0008] Figure 2 It is Figure 1 the circuit topology diagram of the first embodiment of the conversion circuit unit of the isolated DC-DC converter shown.

[0009] Figure 3 It is Figure 1 the circuit topology diagram of the second embodiment of the conversion circuit unit of the isolated DC-DC converter shown.

[0010] Figure 4 It is Figure 1 the circuit topology diagram of the third embodiment of the conversion circuit unit of the isolated DC-DC converter shown.

[0011] Figure 5 It is Figure 1 the circuit topology diagram of the fourth embodiment of the conversion circuit unit of the isolated DC-DC converter shown.

[0012] Figure 6 It is Figure 1 the circuit topology diagram of the fifth embodiment of the conversion circuit unit of the isolated DC-DC converter shown.

[0013] Figure 7 It is Figure 1 the circuit topology diagram of the sixth embodiment of the conversion circuit unit of the isolated DC-DC converter shown.

[0014] Figure 8 It is Figure 1 the circuit topology diagram of the seventh embodiment of the conversion circuit unit of the isolated DC-DC converter shown.

[0015] Figure 9 It is Figure 1 the circuit topology diagram of the eighth embodiment of the conversion circuit unit of the isolated DC-DC converter shown.

[0016] Figure 10 This is the circuit topology diagram of the isolated DC-DC converter according to the second embodiment of the present disclosure.

[0017] Figure 11a It is the circuit topology diagram of an isolated DC-DC converter including two conversion circuit units.

[0018] Figure 11b It is Figure 11aThe circuit topology equivalent diagram is shown when the current flowing through the first coupled inductor L1 is the positive half cycle of the alternating current.

[0019] [List of Reference Numerals]

[0020] 1: Isolated DC-DC converter

[0021] Vin+: input positive

[0022] Vin-: input negative pole

[0023] Vout+: output positive

[0024] Vout-: output negative pole

[0025] 2, 2a, 2b, 2c, 2d, 2e, 2f, 2g: conversion circuit unit

[0026] 21: First input terminal

[0027] 22: Second input terminal

[0028] 23: First output terminal

[0029] 24: Second output terminal

[0030] 3: Primary circuit unit

[0031] 31: First primary bridge arm, primary bridge arm

[0032] Q11, Q12: First switch element

[0033] 32: Second primary bridge arm

[0034] Q13, Q14: First switch element

[0035] A: First connection point

[0036] B: Second connection point

[0037] 4: Secondary circuit unit

[0038] 41: First secondary bridge arm

[0039] Q21, Q22: Second switch element

[0040] 42: Second secondary bridge arm

[0041] Q23, Q24: Second switch element

[0042] C: Third connection point

[0043] D: Fourth connection point

[0044] L1: First coupled inductor

[0045] C1: First capacitor

[0046] L2: Second coupling inductor

[0047] C2: Second capacitor

[0048] Cin: Input capacitor

[0049] Co: Output capacitor

[0050] Lm: Magnetizing inductor

[0051] L3: First resonant inductor

[0052] L4: Second resonant inductor Detailed implementation manners

[0053] Some typical embodiments embodying the features and advantages of the present disclosure will be described in detail in the following description. It should be understood that the present disclosure can have various variations in different embodiments, all of which do not depart from the scope of the present disclosure, and the descriptions and drawings therein are used for illustrative purposes in essence rather than for limiting the present disclosure.

[0054] Please refer to Figure 1 and Figure 2 , wherein Figure 1 is the circuit topology diagram of the isolated DC-DC converter according to the first embodiment of the present disclosure, Figure 2 is Figure 1 the circuit topology diagram of the first embodiment of the conversion circuit unit of the isolated DC-DC converter shown. As shown in Figure 1 , the isolated DC-DC converter 1 of the present disclosure receives input electrical energy via the input positive terminal Vin+ and the input negative terminal Vin-, converts the input electrical energy, and outputs the output electrical energy to a load (not shown) via the output positive terminal Vout+ and the output negative terminal Vout-. The isolated DC-DC converter 1 includes n conversion circuit units 2, where n is an integer greater than or equal to 2. In this embodiment, the input ends of the n conversion circuit units 2 are connected in series with each other, and the output ends of the n conversion circuit units 2 are connected in parallel with each other, so that the isolated DC-DC converter achieves a step-down function, and the number of the conversion circuit units 2 is related to the step-down magnitude and the power magnitude.

[0055] In Figure 2 shows the internal circuit topology of a single conversion circuit unit 2, and Figure 1 the internal circuit topology of each conversion circuit unit 2 in Figure 2 can be the same as the internal circuit topology of the conversion circuit unit 2 in Figure 2As shown, the conversion circuit unit 2 includes a first input terminal 21, a second input terminal 22, a first output terminal 23, and a second output terminal 24. The first input terminal 21 of the first conversion circuit unit 2 among the n conversion circuit units 2 is electrically connected to the input positive terminal Vin+, the second input terminal 22 of the nth conversion circuit unit 2 among the n conversion circuit units 2 is electrically connected to the input negative terminal Vin-, and the second input terminal 22 of the mth conversion circuit unit 2 among the n conversion circuit units 2 is electrically connected to the first input terminal 21 of the (m + 1)th conversion circuit unit 2, where 1 ≤ m < n. The n first output terminals 23 of the n conversion circuit units 2 are all connected to each other and are connected to the output positive terminal Vout+, and the n second output terminals 24 of the n conversion circuit units 2 are all connected to each other and are connected to the output negative terminal Vout-.

[0056] The conversion circuit unit 2 includes a primary circuit unit 3, a secondary circuit unit 4, a first coupling inductor L1, a first capacitor C1, a second coupling inductor L2, and a second capacitor C2. The primary circuit unit 3 is a full-bridge circuit and includes a first primary bridge arm 31 and a second primary bridge arm 32, and the first primary bridge arm 31 and the second primary bridge arm 32 are connected in parallel. The first primary bridge arm 31 includes two first switching elements Q11, Q12. The two first switching elements Q11, Q12 can be formed by switching tubes, for example, and the two first switching elements Q11, Q12 are connected in series, and the connection point between the two first switching elements Q11, Q12 forms a first connection point A. The second primary bridge arm 32 includes two first switching elements Q13, Q14. In this embodiment, the two first switching elements Q13, Q14 are formed by switching tubes, and the two first switching elements Q13, Q14 are connected in series, and the connection point between the two first switching elements Q13, Q14 forms a second connection point B. In some other embodiments, the primary circuit unit 3 is a half-bridge circuit and includes a first primary bridge arm 31 and a second primary bridge arm 32, and the first primary bridge arm 31 and the second primary bridge arm 32 are connected in parallel. The first primary bridge arm 31 includes two first switching elements Q11, Q12. The two first switching elements Q11, Q12 can be formed by switching tubes, for example, and the two first switching elements Q11, Q12 are connected in series, and the connection point between the two first switching elements Q11, Q12 forms a first connection point A. The second primary bridge arm 32 includes two capacitor elements, and the two capacitor elements are connected in series, and the connection point between the two capacitor elements forms a second connection point B.

[0057] The secondary circuit unit 4 is a full-bridge circuit and includes a first secondary bridge arm 41 and a second secondary bridge arm 42. The first secondary bridge arm 41 and the second secondary bridge arm 42 are connected in parallel. The first secondary bridge arm 41 includes two second switching elements Q21 and Q22. The two second switching elements Q21 and Q22 can be formed by, for example, switching tubes or diodes. In this embodiment, the two second switching elements Q21 and Q22 are formed by switching tubes and are connected in series, and a connection point between the two second switching elements Q21 and Q22 forms a third connection point C. The second secondary bridge arm 42 includes two second switching elements Q23 and Q24. The two second switching elements Q23 and Q24 can be formed by, for example, switching tubes or diodes. In this embodiment, the two second switching elements Q23 and Q24 are formed by switching tubes and are connected in series, and a connection point between the two second switching elements Q23 and Q24 forms a fourth connection point D.

[0058] The first coupling inductor L1 and the first capacitor C1 are serially coupled between the first connection point A and the third connection point C. In this embodiment, the first end of the first coupling inductor L1 is electrically connected to the first connection point A, the second end of the first coupling inductor L1 is electrically connected to the first end of the first capacitor C1, and the second end of the first capacitor C1 is electrically connected to the third connection point C. The second coupling inductor L2 and the second capacitor C2 are serially coupled between the second connection point B and the fourth connection point D. In this embodiment, the first end of the first coupling inductor L2 is electrically connected to the second connection point B, the second end of the second coupling inductor L2 is electrically connected to the first end of the second capacitor C2, and the second end of the second capacitor C2 is electrically connected to the fourth connection point D. The first coupling inductor L1 and the second coupling inductor L2 are mutually coupled, and the coupling coefficient between the first coupling inductor L1 and the second coupling inductor L2 is less than 1, for example, between 0.2 and 0.8, and preferably can be 0.5, which means that a part of the first coupling inductor L1 and a part of the second coupling inductor L2 are mutually coupled. The uncoupled partial inductances between the first coupling inductor L1 and the second coupling inductor L2 resonate with the first capacitor C1 and the second capacitor C2 to achieve the effect of power conversion. The coupled partial inductances between the first coupling inductor L1 and the second coupling inductor L2 can equalize the currents flowing between the first connection point A and the third connection point C and between the second connection point B and the fourth connection point D, and further equalize the currents between the conversion path units 2 in the isolated DC-DC converter 1.

[0059] Due to the limitations of existing manufacturing process technologies, there may be errors in the parameters of inductors, capacitors, and switching elements in an isolated DC-DC converter. Differences in the parameters of inductors, capacitors, or switching elements can cause current imbalance between the conversion circuit units of the isolated DC-DC converter, and further cause heat imbalance in the isolated DC-DC converter. Severe heat imbalance may lead to damage to the isolated DC-DC converter. In the isolated DC-DC converter 1 of the present disclosure, the conversion circuit unit 2 couples the first coupled inductor L1 and the second coupled inductor L2. This coupling method can make the currents flowing between the first connection point A and the third connection point C and the currents flowing between the second connection point B and the fourth connection point D achieve current sharing. Specifically, taking the isolated DC-DC converter 1 of this embodiment including two conversion circuit units 2 as an example, its circuit topology is as Figure 11a shown, Figure 11b is Figure 11a the equivalent diagram when the current flowing through the first coupled inductor L1 is in the positive half cycle of the alternating current. The first coupled inductor L1 and the second coupled inductor L2 are coupled. When the currents flowing through the first coupled inductor L1 and the second coupled inductor L2 are imbalanced, the coupling coefficient between the first coupled inductor L1 and the second coupled inductor L2 can be adjusted to make the currents flowing between the first connection point A and the third connection point C and the currents flowing between the second connection point B and the fourth connection point D achieve current sharing, and further make the currents between the conversion circuit units 2 in the isolated DC-DC converter 1 achieve current sharing. For example, when the current flowing through the first coupled inductor L1 is not equal to the current flowing through the second coupled inductor L2, for example, the current flowing through the first coupled inductor L1 is larger, a reverse electromotive force will be generated in the partially coupled inductance between the first coupled inductor L1 and the second coupled inductor L2. The reverse potential will cause the current flowing through the first coupled inductor L1 to decrease and the current flowing through the second coupled inductor L2 to increase, thereby making the currents flowing through the first coupled inductor L1 and the second coupled inductor L2 achieve current sharing. It can be understood that the negative half cycle of the current flowing through the first coupled inductor L1 is also within the protection scope of the present disclosure, and the present disclosure does not make any restrictions.

[0060] In some embodiments, the positions of the first coupled inductor L1 and the first capacitor C1 can be interchanged, that is, the first end of the first capacitor C1 is electrically connected to the first connection point A, the second end of the first capacitor C1 is electrically connected to the first end of the first coupled inductor L1, and the second end of the first coupled inductor L1 is electrically connected to the third connection point C. Also, the positions of the second coupled inductor L2 and the second capacitor C2 can be interchanged, that is, the first end of the second capacitor C2 is electrically connected to the second connection point B, the second end of the second capacitor C2 is electrically connected to the first end of the second coupled inductor L2, and the second end of the second coupled inductor L2 is electrically connected to the fourth connection point D.

[0061] As can be seen from the above, the conversion circuit unit 2 of the isolated DC-DC converter 1 of the present disclosure includes a first coupled inductor L1, a first capacitor C1, a second coupled inductor L2, and a second capacitor C2. The first coupled inductor L1 and the first capacitor C1 are coupled between a first connection point A and a third connection point C, and the second coupled inductor L2 and the second capacitor C2 are coupled between a second connection point B and a fourth connection point D. That is, it represents that the conversion circuit unit 2 of the isolated DC-DC converter 1 of the present disclosure uses the first capacitor C1 and the second capacitor C2 for electrical isolation, and performs resonant conversion using the first branch formed by the first coupled inductor L1 and the first capacitor C1 and the second branch formed by the second coupled inductor L2 and the second capacitor C2. Among them, compared with the transformer in the traditional DC-DC converter, the volume is larger, the loss is higher, and the heat dissipation capacity is lower. The total volume of the inductor and the capacitor is smaller, the loss is lower, and the heat dissipation capacity is higher than that of a general transformer. Therefore, compared with the traditional DC-DC converter, the isolated DC-DC converter 1 of the present disclosure uses the voltage withstand characteristic of the capacitor to replace the electrical insulation of the transformer, and can achieve the advantages of smaller volume, lower loss, and higher heat dissipation capacity, so that the overall power and power density of the isolated DC-DC converter 1 of the present disclosure are higher. In addition, since the conversion circuit unit 2 of the isolated DC-DC converter 1 of the present disclosure includes a first coupled inductor L1 and a second coupled inductor L2, and the first coupled inductor L1 and the second coupled inductor L2 are mutually coupled, therefore, the current flowing between the first connection point A and the third connection point C and the current flowing between the second connection point B and the fourth connection point D can achieve an equal current sharing effect, and further make the current between the conversion circuit units 2 in the isolated DC-DC converter 1 reach an equalized effect.

[0062] Please continue to refer to Figure 2 , the conversion circuit unit 2 of the isolated DC-DC converter 1 of this embodiment may further include an input capacitor Cin and an output capacitor Co. The input capacitor Cin is connected in parallel with the first primary bridge arm 31 and the second primary bridge arm 32 of the primary circuit unit 3. The output capacitor is connected in parallel with the first secondary bridge arm 41 and the second secondary bridge arm 42 of the secondary circuit unit 4.

[0063] Please continue to refer to Figure 1 and Figure 2, each of the n conversion circuit units 2 includes a first coupled inductor L1 and a second coupled inductor L2 that are coupled to each other, that is, it means that the n conversion circuit units 2 have a total of n first coupled inductors L1 and n second coupled inductors L2. In some embodiments, all windings of the n first coupled inductors L1 and all windings of the n second coupled inductors L2 in the n conversion circuit units 2 can be commonly wound on a single magnetic core. In other embodiments, each set of windings of the first coupled inductor L1 and the second coupled inductor L2 that are coupled to each other are wound on a corresponding magnetic core, and the windings of the n first coupled inductors L1 and the second coupled inductors L2 in the n conversion circuit units 2 can be respectively wound on n magnetic cores.

[0064] In some embodiments, the conversion circuit unit of the isolated DC-DC converter may further include an exciting inductor, which can be used to increase the gain (Vo / Vin) adjustment range of the conversion circuit unit of the isolated DC-DC converter. Please refer to Figure 3 and cooperate with Figure 1 , where Figure 3 is Figure 1 the circuit topology diagram of the second embodiment of the conversion circuit unit of the isolated DC-DC converter shown in. As shown in the figure, compared with Figure 2 the conversion circuit unit 2 shown in, the conversion circuit unit 2a of this embodiment further includes an exciting inductor Lm, which is electrically connected between the third connection point C and the fourth connection point D, so that the gain adjustment range of the conversion circuit unit of the isolated DC-DC converter is wider. Of course, the positions of the coupled inductor and the capacitor can also be changed as described above, so it will not be elaborated here.

[0065] Please refer to Figure 4 and cooperate with Figure 1 , where Figure 4 is Figure 1 the circuit topology diagram of the third embodiment of the conversion circuit unit of the isolated DC-DC converter shown in. As shown in the figure, compared with Figure 2The transformation circuit unit 2 shown. The transformation circuit unit 2b of this embodiment further includes a first resonant inductor L3 and a second resonant inductor L4. Among them, the first resonant inductor L3, the first coupled inductor L1, and the first capacitor C1 are serially coupled between the first connection point A and the third connection point C. And in this embodiment, the first end of the first resonant inductor L3 is electrically connected to the first connection point A, the second end of the first resonant inductor L3 is electrically connected to the first end of the first coupled inductor L1, the second end of the first coupled inductor L1 is electrically connected to the first end of the first capacitor C1, and the second end of the first capacitor C1 is electrically connected to the third connection point C. The second resonant inductor L4, the second coupled inductor L2, and the second capacitor C2 are serially coupled between the second connection point B and the fourth connection point D. And in this embodiment, the first end of the second resonant inductor L4 is electrically connected to the second connection point B, the second end of the second resonant inductor L4 is electrically connected to the first end of the first coupled inductor L2, the second end of the second coupled inductor L2 is electrically connected to the first end of the second capacitor C2, and the second end of the second capacitor C2 is electrically connected to the fourth connection point D. In this embodiment, the first coupled inductor L1 and the second coupled inductor L2 are mutually coupled, and the coupling coefficient of the first coupled inductor L1 and the second coupled inductor L2 is less than or equal to 1 and greater than or equal to 0.9, preferably 1, which means that the first coupled inductor L1 and the second coupled inductor L2 are completely coupled. Among them, the first coupled inductor L1 and the second coupled inductor L2 are mutually coupled, so that the current flowing between the first connection point A and the third connection point C and the current flowing between the second connection point B and the fourth connection point D can achieve the effect of current sharing; and the first resonant inductor L3, the second resonant inductor L4, the first capacitor C1, and the second capacitor C2 perform series resonance together to achieve the effect of power conversion.

[0066] Of course, in some embodiments, the transformation circuit unit of the isolated DC-DC converter may simultaneously include an exciting inductor, a first resonant inductor, and a second resonant inductor. Please refer to Figure 5 and cooperate with Figure 1 , where Figure 5 is Figure 1 the circuit topology diagram of the fourth embodiment of the transformation circuit unit of the isolated DC-DC converter shown. As shown in the figure, compared with Figure 4 the transformation circuit unit 2b shown, the transformation circuit unit 2c of this embodiment further includes an exciting inductor Lm, which is electrically connected between the third connection point C and the fourth connection point D, so that the gain adjustment range of the transformation circuit unit of the isolated DC-DC converter is wider. Of course, the positions of the coupled inductor and the capacitor can also be transformed as described above, so it will not be elaborated here.

[0067] In some embodiments, the primary circuit unit of the transformation circuit unit of the isolated DC-DC converter can be a half-bridge circuit including one bridge arm. Please refer to Figure 6 and cooperate withFigure 1 , where Figure 6 is Figure 1 the circuit topology diagram of the fifth embodiment of the conversion circuit unit of the isolated DC-DC converter shown in. As shown in the figure, compared with Figure 1 the primary circuit unit 3 of the conversion circuit unit 2 shown in, the conversion circuit unit 2d of this embodiment only includes a single bridge arm, that is, the primary bridge arm 31. The primary bridge arm 31 is electrically connected between the first input terminal 21 and the second input terminal 22, and includes two first switching elements Q11, Q12. The two first switching elements Q11, Q12 can be constituted by switching tubes, for example, and the two first switching elements Q11, Q12 are connected in series. The connection point between the two first switching elements Q11, Q12 forms the first connection point A. The connection point between the first switching element Q12 and the second input terminal 22 forms the second connection point B, that is, the connection point between the first switching element Q12 and the input negative terminal Vin- forms the second connection point B. In some embodiments, the connection point between the first switching element Q11 and the first input terminal 21 can also form the second connection point B, that is, the connection point between the first switching element Q11 and the input positive terminal Vin+ forms the second connection point B. And in this embodiment, the first coupling inductor L1 and the first capacitor C1 are connected in series between the first connection point A and the third connection point C, and the second coupling inductor L2 and the second capacitor C2 are connected in series between the second connection point B and the fourth connection point D. The connection method is similar to Figure 1 the connection method shown in, so it will not be elaborated here.

[0068] Of course, in some embodiments, when the primary circuit unit of the conversion circuit unit of the isolated DC-DC converter is a half-bridge circuit, the conversion circuit unit of the isolated DC-DC converter can also include an exciting inductor. Please refer to Figure 7 and cooperate with Figure 1 , where Figure 7 is Figure 1 the circuit topology diagram of the sixth embodiment of the conversion circuit unit of the isolated DC-DC converter shown in. As shown in the figure, compared with Figure 6 the conversion circuit unit 2d shown in, the conversion circuit unit 2e of this embodiment also includes an exciting inductor Lm, so that the gain of the conversion circuit unit of the isolated DC-DC converter can be adjusted and the range is wider, and it is electrically connected between the third connection point C and the fourth connection point D. Of course, the positions of the coupling inductor and the capacitor can also be changed as described above, so it will not be elaborated here.

[0069] Of course, in some embodiments, when the primary circuit unit of the conversion circuit unit of the isolated DC-DC converter is a half-bridge circuit, the conversion circuit unit of the isolated DC-DC converter can also include a first resonant inductor and a second resonant inductor. Please refer toFigure 8 And cooperate with Figure 1 , wherein Figure 8 is Figure 1 The circuit topology diagram of the seventh embodiment of the conversion circuit unit of the isolated DC-DC converter shown in. As Figure 8 shown, compared with Figure 6 the conversion circuit unit 2d shown, the conversion circuit unit 2f of this embodiment further includes a first resonant inductor L3 and a second resonant inductor L4. Among them, the first resonant inductor L3, the first coupled inductor L1 and the first capacitor C1 are serially coupled between the first connection point A and the third connection point C. And in this embodiment, the first end of the first resonant inductor L3 is electrically connected to the first connection point A, the second end of the first resonant inductor L3 is electrically connected to the first end of the first coupled inductor L1, the second end of the first coupled inductor L1 is electrically connected to the first end of the first capacitor C1, and the second end of the first capacitor C1 is electrically connected to the third connection point C. The second resonant inductor L4, the second coupled inductor L2 and the second capacitor C2 are serially coupled between the second connection point B and the fourth connection point D. And in this embodiment, the first end of the second resonant inductor L4 is electrically connected to the second connection point B, the second end of the second resonant inductor L4 is electrically connected to the first end of the second coupled inductor L2, the second end of the second coupled inductor L2 is electrically connected to the first end of the second capacitor C2, and the second end of the second capacitor C2 is electrically connected to the fourth connection point D. In this embodiment, the first coupled inductor L1 and the second coupled inductor L2 are mutually coupled, and the coupling coefficient between the first coupled inductor L1 and the second coupled inductor L2 is less than or equal to 1 and greater than or equal to 0.9, preferably 1, which means that the first coupled inductor L1 and the second coupled inductor L2 are completely coupled. Among them, the first coupled inductor L1 and the second coupled inductor L2 are mutually coupled, so that the current flowing between the first connection point A and the third connection point C and the current flowing between the second connection point B and the fourth connection point D can achieve the effect of current sharing; and the first resonant inductor L3, the second resonant inductor L4, the first capacitor C1 and the second capacitor C2 perform series resonance together to achieve the effect of electric energy conversion.

[0070] Of course, in some embodiments, when the primary circuit unit of the conversion circuit unit of the isolated DC-DC converter is a half-bridge circuit, the conversion circuit unit of the isolated DC-DC converter may simultaneously include an exciting inductor, a first resonant inductor and a second resonant inductor. Please refer to Figure 9 And cooperate with Figure 1 , wherein Figure 9 is Figure 1 The circuit topology diagram of the eighth embodiment of the conversion circuit unit of the isolated DC-DC converter shown in. As shown in the figure, compared with Figure 8For the conversion circuit unit 2f shown, the conversion circuit unit 2g of this embodiment further includes an exciting inductor Lm, which is electrically connected between the third connection point C and the fourth connection point D, so that the gain adjustment range of the conversion circuit unit of the isolated DC-DC converter is wider. Of course, the positions of the coupled inductor and the capacitor can also be changed as described above, so they will not be elaborated here.

[0071] In some embodiments, in order to enable the isolated DC-DC converter to achieve a boosting function, the input ends of the n conversion circuit units of the isolated DC-DC converter are connected in parallel with each other, and the output ends of the n conversion circuit units are connected in series with each other. Please refer to Figure 10 , where Figure 10 is the circuit topology diagram of the isolated DC-DC converter according to the second embodiment of the present disclosure. As Figure 10 shown, the input ends of the n conversion circuit units 2 of the isolated DC-DC converter 1a of this embodiment are connected in parallel with each other, and the output ends of the n conversion circuit units 2 are connected in series with each other, so that the isolated DC-DC converter achieves a boosting function, and the number of conversion circuit units 2 is related to the boosting magnitude and power. Of course, each conversion circuit unit 2 in the isolated DC-DC converter 1a can be replaced by the conversion circuit unit in the above embodiment, so they will not be elaborated here.

[0072] In summary, the conversion circuit unit of the isolated DC-DC converter of the present disclosure includes a first coupled inductor, a first capacitor, a second coupled inductor, and a second capacitor. The first coupled inductor and the first capacitor are coupled between a first connection point and a third connection point, and the second coupled inductor and the second capacitor are coupled between a second connection point and a fourth connection point. That is, the conversion circuit unit of the isolated DC-DC converter of the present disclosure uses the voltage withstand characteristics of the first capacitor and the second capacitor for electrical isolation, and uses the first branch formed by the first coupled inductor and the first capacitor and the second branch formed by the second coupled inductor and the second capacitor for resonant conversion. Among them, compared with the relatively large volume, high loss, and low heat dissipation capacity of the transformer in the traditional DC-DC converter, since the volume of the inductor and the capacitor is smaller, the loss is lower, and the heat dissipation capacity is higher than that of the general transformer. Therefore, compared with the traditional DC-DC converter, the isolated DC-DC converter of the present disclosure uses the voltage withstand characteristics of the inductor and the capacitor to replace the electrical isolation of the transformer, which can achieve the advantages of smaller volume, lower loss, and higher heat dissipation capacity, and make the overall power and power density of the isolated DC-DC converter of the present disclosure higher. In addition, since the conversion circuit unit of the isolated DC-DC converter of the present disclosure includes a first coupled inductor and a second coupled inductor, and the first coupled inductor and the second coupled inductor are mutually coupled, the current flowing between the first connection point and the third connection point and the current flowing between the second connection point and the fourth connection point can achieve an equal current sharing effect, thereby achieving an equal current effect between the conversion circuit units 2 in the isolated DC-DC converter 1.

Claims

1. An isolated DC-DC converter, comprising: n conversion circuit units, where n is an integer greater than or equal to 2, and each of the conversion circuit units comprises: A primary circuit unit, comprising a first primary bridge arm and a second primary bridge arm connected in parallel. The first primary bridge arm comprises two first switching elements connected in series, and a connection point between the two first switching elements of the first primary bridge arm forms a first connection point. The second primary bridge arm comprises two first electronic elements connected in series, and a connection point between the two first electronic elements of the second primary bridge arm forms a second connection point; A secondary circuit unit, comprising a first secondary bridge arm and a second secondary bridge arm connected in parallel. The first secondary bridge arm and the second secondary bridge arm respectively comprise two second switching elements connected in series, and a connection point between the two second switching elements of the first secondary bridge arm forms a third connection point. A connection point between the two second switching elements of the second secondary bridge arm forms a fourth connection point; A first coupled inductor and a first capacitor, serially coupled between the first connection point and the third connection point; and A second coupled inductor and a second capacitor, serially coupled between the second connection point and the fourth connection point, wherein the first coupled inductor and the second coupled inductor are mutually coupled, so that the current flowing between the first connection point and the third connection point and the current flowing between the second connection point and the fourth connection point achieve current sharing, and further the current between the n conversion circuit units achieves current sharing; Wherein, Each of the primary circuit units of the n conversion circuit units is connected in one of series and parallel, and each of the secondary circuit units of the n conversion circuit units is connected in the other of series and parallel.

2. The isolated DC-DC converter according to claim 1, wherein each of the conversion circuit units comprises an exciting inductor, electrically connected between the third connection point and the fourth connection point.

3. The isolated DC-DC converter according to claim 1, wherein part of the first coupled inductor and part of the second coupled inductor are mutually coupled, and the uncoupled partial inductance between the first coupled inductor and the second coupled inductor resonates with the first capacitor and the second capacitor.

4. The isolated DC-DC converter according to claim 3, wherein the coupling coefficient between the first coupled inductor and the second coupled inductor is between 0.2 and 0.

8.

5. The isolated DC-DC converter according to claim 1, wherein each of the conversion circuit units further comprises a first resonant inductor and a second resonant inductor. The first resonant inductor is electrically coupled between the first connection point and the third connection point, and the second resonant inductor is electrically coupled between the second connection point and the fourth connection point, Wherein, The first resonant inductor, the second resonant inductor, the first capacitor and the second capacitor perform series resonance.

6. The isolated DC-DC converter according to claim 5, wherein the first coupled inductor and the second coupled inductor are completely coupled.

7. The isolated DC-DC converter as claimed in claim 6, wherein the coupling coefficient of the first coupled inductor and the second coupled inductor is less than or equal to 1 and greater than or equal to 0.

9.

8. The isolated DC-DC converter as claimed in claim 1, wherein each of the conversion circuit units includes an input capacitor connected in parallel with the first primary bridge arm and the second primary bridge arm of the primary circuit unit.

9. The isolated DC-DC converter as claimed in claim 1, wherein each of the conversion circuit units includes an output capacitor connected in parallel with the first secondary bridge arm and the second secondary bridge arm of the secondary circuit unit.

10. The isolated DC-DC converter as claimed in claim 1, wherein the first switching element is a switching transistor, the first electronic component is a switching transistor or a capacitor, and the second switching element is a switching transistor or a diode.

11. The isolated DC-DC converter as claimed in claim 1, wherein all windings of the n first coupled inductors and all windings of the n second coupled inductors in the n conversion circuit units are wound around a magnetic core together.

12. The isolated DC-DC converter as claimed in claim 1, wherein the windings of the first coupled inductor and the second coupled inductor that are mutually coupled in each of the conversion circuit units are wound around a corresponding magnetic core.

13. An isolated DC-DC converter, comprising: n conversion circuit units, where n is an integer greater than or equal to 2, and each of the conversion circuit units includes: a primary circuit unit including a primary bridge arm, the primary bridge arm including two first switching elements connected in series, a connection point between the two first switching elements forming a first connection point, and a second connection point being formed between one of the two first switching elements and an input terminal; a secondary circuit unit including a first secondary bridge arm and a second secondary bridge arm connected in parallel, the first secondary bridge arm and the second secondary bridge arm each including two second switching elements connected in series, a connection point between the two second switching elements of the first secondary bridge arm forming a third connection point, and a connection point between the two second switching elements of the second secondary bridge arm forming a fourth connection point; a first coupled inductor and a first capacitor connected in series between the first connection point and the third connection point; and a second coupled inductor and a second capacitor connected in series between the second connection point and the fourth connection point, wherein the first coupled inductor and the second coupled inductor are mutually coupled, so that the current flowing between the first connection point and the third connection point and the current flowing between the second connection point and the fourth connection point achieve current sharing, and further the current between the n conversion circuit units achieves current sharing; wherein, each of the primary circuit units of the n conversion circuit units is connected in one of series and parallel, and each of the secondary circuit units of the n conversion circuit units is connected in the other of series and parallel.

14. The isolated DC-DC converter according to claim 13, wherein each of the conversion circuit units includes an exciting inductor electrically connected between the third connection point and the fourth connection point.

15. The isolated DC-DC converter according to claim 13, wherein the input terminal is a positive input terminal or a negative input terminal.

16. The isolated DC-DC converter according to claim 13, wherein part of the first coupled inductor L1 and part of the second coupled inductor L2 are coupled to each other, and the uncoupled partial inductances between the first coupled inductor L1 and the second coupled inductor L2 resonate with the first capacitor C1 and the second capacitor C2.

17. The isolated DC-DC converter according to claim 16, wherein the coupling coefficient between the first coupled inductor and the second coupled inductor is between 0.2 and 0.

8.

18. The isolated DC-DC converter according to claim 13, wherein each of the conversion circuit units further includes a first resonant inductor and a second resonant inductor. The first resonant inductor is electrically coupled between the first connection point and the third connection point, and the second resonant inductor is electrically coupled between the second connection point and the fourth connection point. Wherein, the first resonant inductor, the second resonant inductor, the first capacitor and the second capacitor perform series resonance.

19. The isolated DC-DC converter according to claim 16, wherein the first coupled inductor and the second coupled inductor are completely coupled.

20. The isolated DC-DC converter according to claim 19, wherein the coupling coefficient between the first coupled inductor and the second coupled inductor is less than or equal to 1 and greater than or equal to 0.

9.

21. The isolated DC-DC converter according to claim 13, wherein each of the conversion circuit units includes an input capacitor connected in parallel with the primary bridge arm of the primary circuit unit.

22. The isolated DC-DC converter according to claim 13, wherein each of the conversion circuit units includes an output capacitor connected in parallel with the first secondary bridge arm and the second secondary bridge arm of the secondary circuit unit.

23. The isolated DC-DC converter according to claim 13, wherein the first switching element is a switching tube, and the second switching element is a switching tube or a diode.

24. The isolated DC-DC converter according to claim 13, wherein all windings of the n first coupled inductors and all windings of the n second coupled inductors in the n conversion circuit units are commonly wound on a magnetic core.

25. The isolated DC-DC converter according to claim 13, wherein the windings of the first coupled inductor and the windings of the second coupled inductor that are coupled to each other in each of the conversion circuit units are wound on a corresponding magnetic core.

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