TWI685187B - Bi-directional dc-to-dc converter - Google Patents

Abstract

A bi-directional DC-to-DC converter is provided to convert an input DC voltage to into a DC output voltage. The bi-directional DC-to-DC converter includes a primary-side half-bridge switch circuit, a CLLLC resonant circuit, and a secondary-side half-bridge switch circuit. The primary-side half-bridge switch circuit receives the input DC voltage and converts the input DC voltage into a first voltage. The CLLLC resonant circuit is coupled to the primary-side half-bridge switch circuit and is controlled by the first voltage to output a second voltage. The secondary-side half-bridge switch circuit is coupled to the CLLLC resonant circuit, and receives the second voltage and converts the second voltage into the DC output voltage.

Description

Bidirectional DC to DC converter

The invention relates to a bidirectional DC-DC converter, in particular to a three-phase bidirectional DC-DC converter.

Existing resonant DC-DC converters usually achieve the functions of bidirectional voltage conversion and energy transfer by increasing the use of resonant inductors and resonant capacitors. Typically, the input side of the resonant DC-DC converter is the high voltage side, and the output side is the low voltage side. Operation from the high voltage side to the low voltage side can be called forward operation (or buck operation); operation from the low voltage side to the high voltage side can be called reverse operation (or boost) operating).

For the existing two-way resonant DC-DC converter, its obvious defects are: First, it is not easy to achieve the effect of wide input and wide output under forward operation; Second, it is not easy to achieve high voltage gain under reverse operation Efficiency; and three, it is not easy to achieve the requirements of high efficiency and high power density of the bidirectional resonant DC-DC converter.

To achieve the above-mentioned purpose, the bidirectional DC-DC converter proposed by the present invention converts the input DC voltage to provide the output DC voltage. The bidirectional DC-DC converter includes a primary side half-bridge switching bridge arm circuit, a CLLLC resonant tank circuit, and a secondary side half-bridge switching bridge arm circuit. The primary side half-bridge switch bridge arm circuit receives the input DC voltage and converts the input DC voltage to the first voltage. CLLLC The resonant tank circuit is coupled to the primary side half-bridge switching bridge arm circuit, and is controlled by the first voltage to output the second voltage. The secondary side half-bridge switch bridge arm circuit is coupled to the CLLLC resonant tank circuit, receives the second voltage, and converts the second voltage to an output DC voltage.

In one embodiment, any phase of the CLLLC resonant tank circuit includes a transformer that provides a magnetizing inductance, two resonant inductances, and two resonant capacitors.

In one embodiment, the transformer has a star connection structure.

In an embodiment, the component parameter values of the two resonant inductors are symmetric or approximately symmetric, and the component parameter values of the two resonant capacitors are symmetric or approximately symmetric.

In one embodiment, the primary side half-bridge switch bridge circuit includes a switch bridge circuit. The switch bridge arm circuit is powered by the input DC voltage. The switch bridge arm circuit includes a first bridge arm having a first switch and a second switch, a second bridge arm having a third switch and a fourth switch, and a fifth switch and a first switch. The third bridge arm of six switches.

In one embodiment, the secondary side half-bridge switch bridge circuit includes a switch bridge circuit. The switch bridge arm circuit provides an output DC voltage. The switch bridge arm circuit includes a first bridge arm having a first switch and a second switch, a second bridge arm having a third switch and a fourth switch, and a fifth switch and a sixth switch. The third arm of the switch.

In an embodiment, the switches of each bridge arm are transistor switches.

In order to further understand the technology, means and effects of the present invention to achieve the intended purpose, please refer to the following detailed description and drawings of the present invention. I believe the purpose, features and characteristics of the present invention can be obtained in depth and For specific understanding, the accompanying drawings are provided for reference and explanation only, and are not intended to limit the present invention.

Vin+, Vin-‧‧‧ input DC voltage

Vout+, Vout-‧‧‧ output DC voltage

10‧‧‧Bidirectional DC-DC converter

11‧‧‧ Primary side half-bridge switch bridge arm circuit

12‧‧‧CLLLC resonant tank circuit

13‧‧‧ Secondary side half-bridge switch bridge arm circuit

Cin‧‧‧Input capacitance

Co‧‧‧ Output capacitance

Qa1~Qa6‧‧‧switch

Qa7~Qa12‧‧‧switch

Txa1~Txb3‧‧‧transformer

Cra1~Cra6‧‧‧‧Resonant capacitor

Lra1~Lra6‧‧‧‧Resonant inductor

S1~S6‧‧‧Control signal

C _Q1 ~C _Q3 ‧‧‧Voltage gain curve

fr1‧‧‧First resonance frequency

fr2‧‧‧Second resonance frequency

Gv‧‧‧Voltage gain

Figure 1: The circuit diagram of the bidirectional DC-DC converter of the present invention.

Figure 2: The single-phase equivalent circuit diagram of the CLLLC resonant tank circuit of the bidirectional DC-DC converter of the present invention.

FIG. 3 is a waveform diagram of the control mode of the three-phase interleaved half-bridge switching bridge arm of the bidirectional DC-DC converter of the present invention.

4 is a schematic diagram of the voltage gain of the bidirectional DC-DC converter of the present invention.

The technical content and detailed description of the present invention are explained below in conjunction with the drawings.

Please refer to FIG. 1, which is a circuit diagram of a bidirectional DC-DC converter of the present invention. The bidirectional DC-DC converter 10 can be applied to the requirements of bidirectional DC energy conversion, such as but not limited to the bidirectional DC-DC conversion used in the bidirectional energy storage system.

The bidirectional DC-DC converter 10 shown in FIG. 1 is a three-phase circuit topology, which mainly includes a primary side half-bridge switching bridge arm circuit 11 (or high-voltage side half-bridge switching bridge arm circuit), a CLLLC resonant tank circuit 12 and The secondary side half-bridge switch bridge arm circuit 13 (or low-voltage side half-bridge switch bridge arm circuit). The input side of the primary side half-bridge switch bridge arm circuit 11 is coupled to the input DC voltages Vin+, Vin-, and the output side of the primary-side half-bridge switch bridge arm circuit 11 is coupled to the input side of the CLLLC resonant tank circuit 12. The output side of the CLLLC resonant tank circuit 12 is coupled to the input side of the secondary side half-bridge switch bridge arm circuit 13, and the output side of the secondary side half-bridge switch bridge circuit 13 is coupled to output DC voltages Vout+, Vout-. Among them, the primary side half-bridge switch bridge arm circuit 11 adopts an interleaved method to achieve three-phase interleaved control in a phase difference of 120 degrees in sequence, which will be described later. Similarly, the secondary side half-bridge switching bridge arm circuit 13 also achieves three-phase interleaving control by interleaving the phases by 120 degrees from each other in sequence.

The input side of the primary side half-bridge switching bridge arm circuit 11 is coupled to the input DC voltage Vin+, Vin-, wherein the positive input voltage Vin+ and the negative input voltage Vin- are across the input capacitor Cin to supply the primary side half-bridge switching bridge The switch bridge arm circuit of the arm circuit 11.

The switch bridge arm circuit includes three bridge arms, which are a first bridge arm having a first switch Qa1 and a second switch Qa2, a second bridge arm having a third switch Qa3 and a fourth switch Qa4, and a fifth switch Qa5 and a sixth switch The third arm of switch Qa6. The first switch Qa1 and the second switch Qa2 are coupled to point A, the third switch Qa3 and the fourth switch Qa4 are coupled to point B, and the fifth switch Qa5 and the sixth switch Qa6 are coupled to point C.

The output side of the secondary side half-bridge switch bridge circuit 13 is coupled to the output DC voltages Vout+, Vout-, wherein the positive output voltage Vout+ and the negative output voltage Vout- are across the output capacitor Co to provide the positive output voltage Vout+ and Negative output voltage Vout-.

The switch bridge arm circuit includes three bridge arms, which are a first bridge arm having a first switch Qa7 and a second switch Qa8, a second bridge arm having a third switch Qa9 and a fourth switch Qa10, and a fifth switch Qa11 and a sixth switch. The third arm of switch Qa12. The first switch Qa7 and the second switch Qa8 are coupled to point X, the third switch Qa9 and the fourth switch Qa10 are coupled to point Y, and the fifth switch Qa11 and the sixth switch Qa12 are coupled to point Z. Wherein, the above switch may be a transistor switch, such as but not limited to a metal oxide semiconductor field effect transistor (MOSFET), a double carrier junction transistor (BJT) or an insulated gate bipolar transistor (IGBT).

Referring again to FIG. 1 as an example, the input side of the CLLLC resonant tank circuit 12 is coupled to the output side of the primary side half-bridge switch bridge arm circuit 11, and the output side of the CLLLC resonant tank circuit 12 is coupled to the secondary side half-bridge switch bridge arm circuit The input side of 13. Corresponding to the bidirectional DC-DC converter 10 being a three-phase circuit topology, the CLLLC resonant tank circuit 12 has a set of three-phase CLLLC resonant tanks.

The three-phase CLLLC resonant tank has three single-phase CLLLC resonant tanks, namely a first single-phase CLLLC resonant tank, a second single-phase CLLLC resonant tank, and a third single-phase CLLLC resonant tank. among them The first single-phase CLLLC resonant tank includes a first resonant capacitor Cra1, a first resonant inductor Lra1, a first transformer Txa1 with a first magnetizing inductor, a second resonant inductor Lra4, and a second resonant capacitor Cra4 to form the "CLLLC resonance" The "groove" structure, that is, the resonance groove of each phase is composed of a magnetizing inductance, two resonance inductances, and two resonance capacitances. The first single-phase CLLLC resonant tank is coupled between point A of the primary side half-bridge switch bridge arm circuit 11 and point X of the secondary side half-bridge switch bridge arm circuit 13.

Similarly, the second single-phase CLLLC resonant tank includes a third resonant capacitor Cra2, a third resonant inductor Lra2, a second transformer Txa2 having a second magnetizing inductance, a fourth resonant inductor Lra5, and a fourth resonant capacitor Cra5 to constitute the The structure of "CLLLC resonance tank", that is, the resonance tank of each phase is composed of a magnetizing inductance, two resonance inductances and two resonance capacitors. The second single-phase CLLLC resonant tank is coupled between the point B of the primary side half-bridge switch bridge arm circuit 11 and the point Y of the secondary side half-bridge switch bridge arm circuit 13.

Similarly, the third single-phase CLLLC resonant tank includes a fifth resonant capacitor Cra3, a fifth resonant inductor Lra3, a third transformer Txa3 with a third magnetizing inductor, a sixth resonant inductor Lra6, and a sixth resonant capacitor Cra6 to constitute the The structure of "CLLLC resonance tank", that is, the resonance tank of each phase is composed of a magnetizing inductance, two resonance inductances and two resonance capacitors. The third single-phase CLLLC resonance tank is coupled between the point C of the primary side half-bridge switch bridge arm circuit 11 and the point Z of the secondary side half-bridge switch bridge arm circuit 13.

In the present invention, the primary side and secondary side of the transformer of each phase CLLLC resonant tank (ie, transformers Txa1~Txa3, transformers Txb1~Txb3) are Y-connected (star-connected) architecture, so the transformer of each phase CLLLC resonant tank Topology for YY connection. Through the circuit structure connected by Y-Y, three-phase balance and current sharing can be achieved.

Taking the first single-phase CLLLC resonant tank as an example, the first resonant capacitor Cra1 and the first resonant inductor Lra1 are coupled in series to the primary side of the first transformer Txa1, and the second resonant inductor Lra4 and the second The resonance capacitor Cra4 is coupled in series to the secondary side of the first transformer Txa1. According to this, in accordance with the magnetizing inductance of the first transformer Txa1, a structure of a so-called CLLLC resonance tank is formed.

Furthermore, through the CLLLC resonant tank circuit of symmetrical design or approximately symmetrical design, that is, the symmetrical design or approximately symmetrical design of the resonance capacitor and resonant inductance component parameter values coupled to the primary side and the secondary side of the transformer can meet the bidirectional power supply The wide voltage range and high voltage gain requirements under operation. Taking the first single-phase CLLLC resonant tank as an example, the first resonance is designed according to the turns ratio relationship between the primary side coil and the secondary side coil of the first transformer Txa1 (for impedance design, it refers to the relationship of the square turns ratio) The capacitance values of the capacitor Cra1 and the second resonant capacitor Cra4, and the inductance values of the first resonant inductor Lra1 and the second resonant inductor Lra4 are designed to meet the requirements of a wide voltage range and high voltage gain under bidirectional operation of the power supply. Other single-phase CLLLC resonant tanks also have the same circuit topology design and component parameter design requirements. Please refer to the foregoing description of the first single-phase CLLLC resonant tank as an example, which will not be repeated here.

2 and 3, which are respectively a single-phase equivalent circuit diagram of the CLLLC resonant tank circuit of the bidirectional DC-DC converter of the present invention and a waveform diagram of the control mode of the three-phase interleaved half-bridge switching bridge arm. As shown in FIGS. 3 and 1, taking the control of the upper switching bridge arm circuit of the primary side half-bridge switching bridge arm circuit 11 as an example, three-phase interleaving control with phases different from each other by 120 degrees in sequence is performed, in which the switching control signals S1, S2 Control the first switch Qa1 and the second switch Qa2 of the upper switch bridge arm circuit respectively, the switch control signals S3, S4 respectively control the third switch Qa3 and the fourth switch Qa4 of the upper switch bridge arm circuit, and the switch control signals S5, S6 respectively Control the fifth switch Qa5 and the sixth switch Qa6 of the upper switch arm circuit, that is, the control timing of each switch arm is 120 degrees apart from each other, thereby generating the input voltage V _AB , V _BC , V of the high frequency AC square wave _CA supplies the CLLLC resonant tank circuit 12.

As shown in FIG. 2, the A and B phase voltages (input voltage V _AB ) generated in FIG. 3 supply the first single-phase CLLLC resonant tank and the second single-phase CLLLC resonant tank. Similarly, the B and C phase voltages (input voltage V _BC ) supply the second single-phase CLLLC resonance tank and the third single-phase CLLLC resonance tank; the C and A phase voltages (input voltage V _CA ) supply the third single-phase CLLLC The resonant tank and the first single-phase CLLLC resonant tank. Incidentally, FIG. 2 can be regarded as the equivalent circuit of the single-phase CLLLC resonant tank circuit 12 on the primary side or the secondary side, that is, through the conversion of the turns ratio relationship between the primary side coil and the secondary side coil, which includes the magnetizing inductance Lm, resonance inductance Lr1, Lr2 and resonance capacitance Cr1, Cr2.

；第二諧振頻率

；其中，第一諧振頻率fr1大於第二諧振頻率fr2。 Taking the CLLLC resonant tank circuit 12 shown in FIG. 2 as an example, due to the effects of the magnetizing inductance and the resonant inductance, it generates two resonance frequencies, namely a first resonance frequency fr1 and a second resonance frequency fr2. Among them, the first resonance frequency

; Second resonant frequency

; Where the first resonance frequency fr1 is greater than the second resonance frequency fr2.

When the switching frequency of the switch is greater than the first resonant frequency fr1, the CLLLC resonant tank circuit 12 is equivalent to operating in a series resonant converter (SRC) state, and the series resonant circuit has zero voltage switching (ZVS) characteristics. When operating in the SRC state, the voltage gain is less than or equal to 1, and the maximum value of the voltage gain occurs when the switching frequency is equal to the first resonance frequency fr1.

When the switching frequency of the switch is less than the first resonant frequency fr1 and greater than the second resonant frequency fr2, the CLLLC resonant tank circuit 12 is equivalent to operating in an LLC resonant converter (LLC) state. The difference between LLC and SRC is that the former (LLC) adds a magnetizing inductance Lm as a resonant element, so both have the characteristics of zero voltage switching (ZVS). In addition, when operating in the LLC state, the voltage gain is greater than or equal to 1, and the LLC resonant converter has the characteristics of rectification and zero current switching (ZCS).

Therefore, by changing different switching frequencies, the CLLLC resonant tank circuit 12 provides circuit characteristics with zero voltage switching (ZVS) and zero current switching (ZCS) to achieve flexible switching of all switches and effectively reduce switching losses, Improve the overall efficiency of the converter.

為例，配合參見圖1，在順向操作時，可透過設計諧振電感Lr1為Lra1、Lra2或者Lra3，設計諧振電容Cr1為Cra1、Cra2或者Cra3；在逆向操作時，可透過設計諧振電感Lr1為Lra4、Lra5或者Lra6，設計諧振電容Cr1為Cra4、Cra5或者Cra5，使得滿足順向操作時的第一諧振頻率fr1與逆向操作時的第一諧振頻率fr1兩者相差在±20%以內的要求，以實現CLLLC諧振槽電路的近似對稱設計。 By the way, the CLLLC resonant tank circuit of the approximately symmetrical design described in the previous disclosure refers to the design of the parameter values of the resonant capacitor and the resonant inductance element to make the first resonance frequency fr1 in forward operation and the first resonance in reverse operation The frequency fr1 is within ±20%. At the first resonant frequency

For example, referring to FIG. 1, in forward operation, the resonant inductor Lr1 can be designed as Lra1, Lra2 or Lra3, and the resonant capacitor Cr1 can be designed as Cra1, Cra2 or Cra3; in reverse operation, the resonant inductor Lr1 can be designed as For Lra4, Lra5 or Lra6, design the resonant capacitor Cr1 to be Cra4, Cra5 or Cra5 so that the first resonance frequency fr1 in forward operation and the first resonance frequency fr1 in reverse operation are within ±20% of the difference, In order to realize the approximately symmetrical design of CLLLC resonant tank circuit.

Please refer to FIG. 4, which is a schematic diagram of the voltage gain of the bidirectional DC-DC converter of the present invention. According to the design of the aforementioned CLLLC resonant tank circuit 12, the voltage gain Gv during forward operation as illustrated in FIG. 4 can be obtained. FIG. 4 shows three voltage gain curves, namely a first voltage gain curve C _Q1 , a second voltage gain curve C _Q2 and a third voltage gain curve C _Q3 . Among them, the common intersection of the three voltage gain curves is when the operating frequency is equal to the first resonance frequency fr1. Specifically, the three voltage gain curves represent the voltage gain of the CLLLC resonant tank circuit 12 under different quality factors (Q values). Among them, the quality factor (Q value) refers to the ratio of the stored energy of the system to the energy provided by the outside world in each cycle at the resonance frequency of the system when the signal amplitude does not change with time, that is, the high Q value indicates the energy at resonance The loss rate is slow and the resonance lasts for a long time. Conversely, a low Q value indicates that the energy loss rate at resonance is faster and the resonance lasts for a shorter time. Therefore, the quality factor of the first voltage gain curve C _Q1 is less than the quality factor of the second voltage gain curve C _Q2 , and the quality factor of the second voltage gain curve C _Q2 is less than the quality factor of the third voltage gain curve C _Q3 .

In this way, in addition to changing the different switching frequencies, the CLLLC resonant tank circuit 12 provides circuit characteristics with zero voltage switching (ZVS) and zero current switching (ZCS), and makes the CLLLC resonant tank circuit 12 forward It can provide better (greater than 1) voltage gain Gv during operation. same Ground, when the CLLLC resonant tank circuit 12 is operated in reverse, it can also provide a better (greater than 1) voltage gain Gv. In addition, in order to meet the requirements of wide voltage range and high voltage gain under bidirectional operation of the power supply, the present invention adopts a CLLLC resonant tank circuit with a symmetrical design or an approximately symmetrical design. Therefore, the voltage gain Gv during reverse operation is also as shown in FIG. The voltage gain schematic shown is approximate and will not be repeated here. In summary, the bidirectional DC-DC converter 10 of the present invention can achieve the effect of high voltage gain in both forward (buck) operation and reverse (boost) operation.

In summary, the present invention has the following features and advantages:

1. Through the symmetrical design or approximately symmetrical design of the CLLLC resonant tank circuit, that is, the symmetrical design or approximately symmetrical design of the resonance capacitor and resonant inductance component parameter values coupled to the primary and secondary sides of the transformer can meet the bidirectional operation of the power supply Under the wide voltage range and high voltage gain requirements.

2. The CLLLC resonant tank circuit has a plurality of Y-Y connected transformers Txa1~Txa3, so that through the Y-Y connected circuit structure, three-phase balance and current sharing can be achieved.

3. By changing different switching frequencies, the CLLLC resonant tank circuit provides circuit characteristics with zero voltage switching (ZVS) and zero current switching (ZCS) to achieve flexible switching of all switches, effectively reducing switching losses, and improving The overall efficiency of the converter.

4. The bidirectional DC-DC converter proposed by the present invention can achieve the effect of wide input and wide output in forward operation; in reverse operation, it can easily achieve the effect of high voltage gain; and the bidirectional resonance is easy to achieve The requirement of high efficiency and high power density of DC-to-DC converter.

The above are only the detailed descriptions and drawings of the preferred embodiments of the present invention, but the features of the present invention are not limited to this, and are not intended to limit the present invention. All the scope of the present invention should be based on the following patent applications Subject to the implementation of the spirit and similar changes within the scope of the patent application of the present invention For example, all should be included in the scope of the present invention, and any person who is familiar with this skill in the field of the present invention can easily think of changes or modifications that can be covered by the patent scope of the following case.

Vin+, Vin-‧‧‧ input DC voltage

Vout+, Vout-‧‧‧ output DC voltage

10‧‧‧Bidirectional DC-DC converter

11‧‧‧ Primary side half-bridge switch bridge arm circuit

12‧‧‧CLLLC resonant tank circuit

13‧‧‧ Secondary side half-bridge switch bridge arm circuit

Cin‧‧‧Input capacitance

Co‧‧‧ Output capacitance

Qa1~Qa6‧‧‧switch

Qa7~Qa12‧‧‧switch

Txa1~Txa3‧‧‧transformer

Cra1~Cra3, Cra4~Cra6 ‧‧‧ resonant capacitor

Lra1~Lra3, Lra4~Lra6 ‧‧‧Resonance inductance

Claims (8)

A bidirectional DC-DC converter converts an input DC voltage to provide an output DC voltage. The bidirectional DC-DC converter includes: a primary-side half-bridge switching bridge arm circuit that receives the input DC voltage and converts the input The DC voltage is a first voltage; a CLLLC resonant tank circuit, coupled to the primary side half-bridge switching bridge circuit, and controlled by the first voltage to output a second voltage; the CLLLC resonant tank circuit generates a first voltage A resonant frequency and a second resonant frequency, and the first resonant frequency is greater than the second resonant frequency; and the primary side half-bridge switch bridge arm circuit is coupled to the CLLLC resonant tank circuit, receives the second voltage, and converts the The second voltage is the output DC voltage; wherein, when the switching frequency is greater than the first resonant frequency, the CLLLC resonant tank circuit operates as a series resonant converter; when the switching frequency is less than the first resonant frequency, and greater than the first At two resonant frequencies, the CLLLC resonant tank circuit operates in the LLC resonant converter state. The bidirectional DC-DC converter as described in item 1 of the patent application scope, wherein any phase of the CLLLC resonant tank circuit includes a transformer that provides a magnetizing inductance, two resonant inductances, and two resonant capacitors. The bidirectional DC-DC converter as described in item 2 of the patent application scope, in which the transformer has a star connection structure. The bidirectional DC-DC converter as described in item 2 of the patent application scope, wherein the component parameter values of the two resonant inductors are symmetrical or approximately symmetrical, and the component parameter values of the two resonant capacitors are symmetrical or approximately symmetrical. The bidirectional DC-DC converter as described in item 1 of the patent application scope, wherein the primary side half-bridge switch bridge arm circuit includes: a switch bridge arm circuit powered by the input DC voltage, and the switch bridge arm circuit includes A first bridge arm with a first switch and a second switch, a second bridge arm with a third switch and a fourth switch, and a third bridge arm with a fifth switch and a sixth switch. The bidirectional DC-DC converter as described in item 5 of the patent application, wherein the switch of each bridge arm is a transistor switch. The bidirectional DC-DC converter as described in item 1 of the patent scope, wherein the secondary side half-bridge switch bridge arm circuit includes: a switch bridge arm circuit that provides the output DC voltage, and the switch bridge arm circuit includes A first bridge arm with a first switch and a second switch, a second bridge arm with a third switch and a fourth switch, and a third bridge arm with a fifth switch and a sixth switch. The bidirectional DC-DC converter as described in item 7 of the patent application scope, wherein the switch of each bridge arm is a transistor switch.

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