Bidirectional DC-DC converter for dual power supply system in vehicle

Abstract

The present invention relates to the field of electronic technology, and in particular to a bidirectional DC-DC converter for a vehicle-mounted dual power supply system, characterized in that a two-phase staggered parallel bidirectional four-switch Buck-Boost circuit is adopted as the basic topology of the bidirectional DC-DC converter, and the basic topology structure includes four groups of bridge arm circuits and a first energy storage inductor, a second energy storage inductor, a first power supply, a second power supply, a generator, a first capacitor and a second capacitor; the four groups of bridge arm circuits include a first group of bridge arms, a second group of bridge arms, a third group of bridge arms and a fourth group of bridge arms, wherein the first group of bridge arms and the first energy storage inductor and the second group of bridge arms constitute a first-phase bidirectional DCDC circuit; the third group of bridge arms and the second energy storage inductor and the fourth group of bridge arms constitute a second-phase bidirectional DCDC circuit; the present invention has the characteristics of bidirectional energy flow, improves the power level of the system, reduces the output voltage and current ripple, can automatically realize current sharing, and reduces the volume of the system and reduces the complexity of the system.

Description

Technical Field

[0001] The present invention relates to the field of electronic technology, and in particular to a bidirectional DC-DC converter for a vehicle-mounted dual power supply system, which has the characteristics of bidirectional energy flow, improves the power level of the system, reduces the output voltage and current ripple, can automatically achieve current balancing, reduces the volume of the system, and reduces the complexity of the system. Background Art

[0002] With the vigorous development of the logistics and transportation industry, modern commercial vehicles and logistics transport vehicles have become indispensable transportation and distribution tools in the logistics industry. People not only put forward high requirements for their practicality and reliability, but also put forward further requirements for the comfort of the driver. Since the original vehicle battery is still a thin-plate battery suitable for vehicle starting, it cannot adapt to the high-current deep discharge state when high-power electrical equipment (air conditioners, induction cookers, etc.) is running, which seriously affects the service life of the battery. Therefore, adding a lithium battery pack to the traditional on-board single power supply system to form a dual power supply system can effectively reduce the discharge current and increase the service life of the original vehicle battery. And between the original vehicle battery and the lithium battery pack, it is necessary to insert the core part of the on-board dual power supply system, that is, the bidirectional DC-DC converter, so as to realize the bidirectional flow of energy. The DC-DC converter is a device that converts one type of direct current into another type of fixed or adjustable direct current, also known as a DC-DC converter, which is widely used in hybrid vehicle driving and battery energy storage systems. In the prior art, most DC-DC converters are unidirectional, that is, they can only step up or down in one direction. For a unidirectional boost DC-DC converter, after DC power is input at one end, a higher voltage DC power will be output at the other end; for a unidirectional buck DC-DC converter, after DC power is input at one end, a lower voltage DC power will be output at the other end. The energy flow direction of this unidirectional DC-DC converter is fixed and not reversible.

[0003] For situations where bidirectional energy flow is required, if two unidirectional DC-DC converters are used in parallel in opposite directions, bidirectional energy flow can be achieved by switching between two working states. Although this method is easy to control, it will increase the complexity of the system, and the system power level is low. At the same time, it will increase the volume and weight of the system, resulting in a waste of resources. Existing patent document: 201711406600.8 discloses a bidirectional DC-DC topology structure that can achieve bidirectional energy flow and has various conversion methods, but the output voltage and current ripple is large, the current sharing problem needs to be considered, and the fault tolerance is low. Summary of the invention

[0004] In view of the shortcomings and deficiencies in the prior art, the present invention provides a bidirectional DC-DC converter for a vehicle-mounted dual power supply system that has the characteristic of bidirectional energy flow, solves the problem that a traditional DC-DC converter can only realize unidirectional energy flow in a single working mode, improves the power level of the system, reduces the output voltage and current ripple, can automatically realize current balancing, and at the same time reduces the volume of the system and reduces the complexity of the system.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A bidirectional DC-DC converter for a vehicle-mounted dual power supply system, characterized in that a two-phase staggered parallel bidirectional four-switch Buck-Boost circuit is used as the basic topology of the bidirectional DC-DC converter, the basic topology structure includes four groups of bridge arm circuits and a first energy storage inductor, a second energy storage inductor, a first power supply, a second power supply, a generator, a first capacitor and a second capacitor; the four groups of bridge arm circuits include a first group of bridge arms, a second group of bridge arms, a third group of bridge arms and a fourth group of bridge arms, wherein the first group of bridge arms and the first energy storage inductor and the second group of bridge arms constitute a first-phase bidirectional DCDC circuit; the third group of bridge arms and the second energy storage inductor and the fourth group of bridge arms constitute a second-phase bidirectional DCDC circuit;

[0007] The first bridge arm group is composed of switch tubes VT1 and VT2, the second bridge arm group is composed of switch tubes VT3 and VT4, the third bridge arm group is composed of switch tubes VT5 and VT6, and the fourth bridge arm group is composed of switch tubes VT7 and VT8.

[0008] The source of the switch tube VT1 is connected to the drain of the switch tube VT2, and is connected to the first end of the first energy storage inductor as the common end of the first group of bridge arms. The drain of the switch tube VT1 is connected to the first end of the first capacitor and the first end of the generator as the first end of the first group of bridge arms. The source of the switch tube VT2 is connected to the second end of the first capacitor and the second end of the generator as the second end of the first group of bridge arms.

[0009] The drain of the switch tube VT3 is connected to the source of the switch tube VT4 and is connected to the second end of the second energy storage inductor as the common end of the second group of bridge arms. The drain of the switch tube VT4 is connected to the first end of the second capacitor as the first end of the second group of bridge arms. The source of the switch tube VT3 is connected to the second end of the second capacitor as the second end of the second group of bridge arms.

[0010] The source of the switch tube VT5 is connected to the drain of the switch tube VT6, and is connected to the first end of the second energy storage inductor as the common end of the third group of bridge arms. The drain of the switch tube VT5 is connected to the first end of the first capacitor and the first end of the generator as the first end of the third group of bridge arms. The source of the switch tube VT5 is connected to the second end of the first capacitor and the generator as the second end of the third group of bridge arms.

[0011] The drain of the switch tube VT7 is connected to the source of the switch tube VT8 and is connected to the second end of the second energy storage inductor as the common end of the fourth group of bridge arms. The drain of the switch tube VT8 is connected to the first end of the second capacitor as the first end of the fourth group of bridge arms. The source of the switch tube VT7 is connected to the second end of the second capacitor as the second end of the fourth group of bridge arms.

[0012] In the present invention, each switch tube has a diode connected in reverse parallel therewith to play a freewheeling role; the eight switch tubes are all NMOS tubes; the parameters of the first capacitor and the second capacitor are the same; the parameters of the first energy storage inductor and the second energy storage inductor are the same.

[0013] In the present invention, the first power source adopts a lead-acid battery, that is, an original vehicle battery, and the second power source adopts a lithium battery pack.

[0014] The bidirectional DC-DC converter in the vehicle-mounted dual power supply system proposed by the present invention can work in six working modes, namely, bidirectional Boost mode, bidirectional Buck mode, and bidirectional Buck-Boost mode: when the bidirectional DC-DC converter works in the forward Boost mode, the switch tubes VT1 and VT5 are turned on, and the switch tubes VT2 and VT6 are turned off; the switch tubes VT3, VT4, VT7, and VT8 work at a certain duty cycle respectively; the bidirectional DC-DC converter can be equivalent to a two-phase forward Boost circuit staggered in parallel;

[0015] When the bidirectional DC-DC converter operates in the reverse Buck mode, the switch tubes VT1 and VT5 are turned on, the switch tubes VT2 and VT6 are turned off, VT4 and VT8 operate at a certain duty cycle, and the switch tubes VT3 and VT7 operate at a complementary duty cycle with a dead time. The bidirectional DC-DC converter can be equivalent to a form of two reverse Buck circuits staggered in parallel.

[0016] When the bidirectional DC-DC converter operates in the forward Buck-Boost mode, the switch tubes VT1, VT3, VT5, and VT7 operate at a certain duty cycle, and the switch tubes VT2, VT4, VT6, and VT8 operate at a complementary duty cycle with a dead time. The bidirectional DC-DC converter can be equivalent to two circuit structures in which the first-phase Buck converter and the second-phase Boost converter are staggered in parallel or the first-phase Boost converter and the second-phase Buck converter are staggered in parallel.

[0017] When the bidirectional DC-DC converter operates in the reverse Buck-Boost mode, the switch tubes VT2, VT4, VT6, and VT8 operate at a certain duty cycle, and the switch tubes VT1, VT3, VT5, and VT7 operate at a complementary duty cycle with a dead time. Therefore, the bidirectional DC-DC converter can be equivalent to two circuit structures in which the first-phase Boost converter and the second-phase Buck converter are staggered in parallel or the first-phase Buck converter and the second-phase Boost converter are staggered in parallel.

[0018] When the bidirectional DC-DC converter operates in the reverse Boost mode, the switch tubes VT4 and VT8 are turned on, the switch tubes VT3 and VT7 are turned off, and the switch tubes VT1, VT5, VT2, and VT6 respectively operate at a certain duty cycle. The bidirectional DC-DC converter can be equivalent to the form of two reverse Boost circuits staggered in parallel.

[0019] When the bidirectional DC-DC converter operates in the forward Buck mode, the switch tubes VT4 and VT8 are turned on, the corresponding switch tubes VT3 and VT7 are turned off, and the switch tubes VT1, VT2, VT5, and VT6 respectively operate at a certain duty cycle. The bidirectional DC-DC converter can be equivalent to a two-phase forward Buck circuit staggered in parallel.

[0020] In summary, the present invention provides the following beneficial effects: (1) The present invention adopts a two-phase staggered parallel synchronous four-switch Buck-Boost circuit, which can realize bidirectional energy flow according to the charging and discharging requirements of the original vehicle battery, and can also convert the mode according to the status of the connected original vehicle battery and the lithium battery pack to realize bidirectional energy flow. (2) The present invention can work in a bidirectional Buck-Boost mode, that is, when the voltages at both ends of the bidirectional DC-DC converter are similar, the conversion method is diverse. (3) The present invention adopts the form of staggered parallel connection, which can effectively reduce the discharge current of high-power electrical equipment in the system during operation, and improve the power level and work efficiency of the system; at the same time, the present invention adopts the form of staggered parallel connection, which can reduce the output voltage and current ripple and improve the dynamic response speed of the system. (4) The present invention adopts the form of staggered parallel connection, and the system fault tolerance is high. When one phase of the bidirectional DC-DC converter fails, the other phase of the bidirectional DC-DC converter can still continue to work. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Attached Figure 1 It is a circuit diagram of the present invention.

[0022] Attached Figure 2 is the working modal diagram of the forward Boost mode when D<0.5 in the embodiment of the present invention, where Figure 2 (1) is the modal diagram of t0-t1, Figure 2 (2) is the modal diagram of t1-t2, Figure 2 (3) is the modal diagram of t2-t3, Figure 2 (4) is the modal diagram of t3-t4.

[0023] Attached Figure 3 is the working modal diagram of the forward Boost mode when D=0.5 in the embodiment of the present invention, wherein Figure 3 (1) is the modal diagram of t0-t1, Figure 3 (2) is the modal diagram of t1-t2.

[0024] Attached Figure 4 is the working modal diagram of the forward Boost mode when D>0.5 in the embodiment of the present invention, where Figure 4 (1) is the modal diagram of t0-t1, Figure 4 (2) is the modal diagram of t1-t2, Figure 4 (3) is the modal diagram of t2-t3, Figure 4 (4) is the modal diagram of t3-t4.

[0025] Attached Figure 5 is the working mode diagram of the reverse Buck mode when D<0.5 in the embodiment of the present invention, where Figure 5 (1) is the modal diagram of t0-t1, Figure 5 (2) is the modal diagram of t1-t2, Figure 5 (3) is the modal diagram of t2-t3, Figure 5 (4) is the modal diagram of t3-t4.

[0026] Attached Figure 6 is the working mode diagram of the reverse Buck mode D=0.5 in the embodiment of the present invention, where Figure 6 (1) is the modal diagram of t0-t1, Figure 6 (2) is the modal diagram of t1-t2.

[0027] Attached Figure 7 is the working mode diagram of the reverse Buck mode when D>0.5 in the embodiment of the present invention, where Figure 7 (1) is the modal diagram of t0-t1, Figure 7 (2) is the modal diagram of t1-t2, Figure 7 (3) is the modal diagram of t2-t3, Figure 7 (4) is the modal diagram of t3-t4.

[0028] Attached Figure 8 This is a circuit diagram of an upper-path Boost converter and a lower-path Buck converter in a forward Buck-Boost mode in an embodiment of the present invention being alternately connected in parallel.

[0029] Attached Fig. 9 The circuit diagram of the upper Buck converter and the lower Boost converter in the forward Buck-Boost mode in an embodiment of the present invention is an alternately connected circuit in parallel.

[0030] Attached Fig.10 is a working mode diagram of the forward Buck-Boost mode in an embodiment of the present invention, wherein Fig.10 (1) is the modal diagram of t0-t1, Fig.10 (2) is the modal diagram of t1-t2, Fig.10 (3) is the modal diagram of t2-t3, Fig.10 (4) is the modal diagram of t3-t4.

[0031] Figure numerals: first group of bridge arms 1, second group of bridge arms 2, third group of bridge arms 3, fourth group of bridge arms 4, first energy storage inductor 5, second energy storage inductor 6, first capacitor 7, second capacitor 8, first power supply 9, second power supply 10, generator 11. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be fully and clearly described below in conjunction with the accompanying drawings and embodiments.

[0033] Example:

[0034] The present invention provides a bidirectional DC-DC converter for a vehicle-mounted dual power supply system, which is used to realize bidirectional flow of energy and can effectively reduce output voltage and current ripples, automatically realize current balancing, and improve the power level and working efficiency of the system.

[0035] As attached Figure 1 As shown, the present invention includes four groups of bridge arms (respectively, a first group of bridge arms 1, a second group of bridge arms 2, a third group of bridge arms 3, and a fourth group of bridge arms 4), a first energy storage inductor 5, a second energy storage inductor 6, a first power supply 9, a second power supply 10, a generator 11, a first capacitor 7, and a second capacitor 8. The first group of bridge arms 1 includes switch tubes VT1 and VT2, the second group of bridge arms 2 includes switch tubes VT3 and VT4, the third group of bridge arms 3 includes switch tubes VT5 and VT6, and the fourth group of bridge arms 4 includes switch tubes VT7 and VT8. All eight switch tubes are reversely connected in parallel with a diode to play a freewheeling role; the eight switch tubes of the four groups of bridge arms are NMOS tubes;

[0036] The specific connection relationship of the four groups of bridge arm circuits is as follows:

[0037] The source of the switch tube VT1 in the first group of bridge arms 1 is connected to the drain of the switch tube VT2, and is connected to the first end of the first energy storage inductor 5 as the common end of the first group of bridge arms 1, the drain of the switch tube VT1 is connected to the first end of the first capacitor 7 as the first end of the first group of bridge arms 1, and the source of the switch tube VT2 is connected to the second end of the first capacitor 7 as the second end of the second group of bridge arms 2;

[0038] The drain of the switch tube VT3 in the second group of bridge arms 2 is connected to the source of the switch tube VT4, and is connected to the second end of the first energy storage inductor 5 as the common end of the second group of bridge arms 2. The drain of the switch tube VT4 is connected to the first end of the second capacitor 8 as the first end of the second group of bridge arms 2. The source of the switch tube VT5 is connected to the second end of the second capacitor 8 as the second end of the second group of bridge arms 2.

[0039] The drain of the switch tube VT5 in the third group of bridge arms 3 is connected to the source of the switch tube VT6, and is connected to the first end of the second energy storage inductor 6 as the common end of the third group of bridge arms 3, the drain of the switch tube VT5 is connected to the first end of the first capacitor 7 as the first end of the third group of bridge arms 3, and the source of the switch tube VT6 is connected to the second end of the first capacitor 7 as the second end of the third group of bridge arms 3;

[0040] The drain of the switch tube VT7 in the fourth group of bridge arms 4 is connected to the source of the switch tube VT8, and is connected to the second end of the second energy storage inductor 6 as the common end of the fourth group of bridge arms 4, the drain of the switch tube VT8 is connected to the first end of the second capacitor 8 as the first end of the fourth group of bridge arms 4, and the source of the switch tube VT7 is connected to the second end of the second capacitor 8 as the second end of the fourth group of bridge arms 4;

[0041] The first end and the second end of the first capacitor 7 are connected to the positive electrode and the negative electrode of the first power supply 9 respectively, and the first end and the second end of the second capacitor 8 are connected to the positive electrode and the negative electrode of the second power supply 10 respectively.

[0042] In this example, the bidirectional DC-DC converter used in the vehicle dual power system can work in six working modes, namely, bidirectional Boost mode, bidirectional Buck mode, and bidirectional Buck-Boost mode. The following will describe in detail the conduction of the switch tube controlled by the drive circuit and the selection of the duty cycle. It should be noted that since the analysis methods are similar among the six working modes, the following analysis only includes three working modes:

[0043] 1. Bidirectional DC-DC converter works in forward Boost mode

[0044] When the bidirectional DC-DC converter works in the forward Boost mode, the switches VT1 and VT5 remain turned on, the switches VT2 and VT6 remain turned off, and the switches VT3, VT4, VT7, and VT8 work at a certain duty cycle. According to the duty cycle D of the switches VT3 and VT7, the forward Boost mode can be divided into three states: D<0.5, D=0.5, and D>0.5.

[0045] Figure 2 This is the working mode diagram when the duty cycle D<0.5 in the forward Boost mode. At t0~t1, the drive circuit controls the switch tubes VT3 and VT8 to turn on, VT4 and VT7 to turn off, the first inductor 5 stores energy, and the second inductor 6 releases energy; at t1~t2, the drive circuit controls the switch tubes VT3 and VT7 to turn off, VT4 and VT8 to turn on, the first inductor 5 and the second inductor 6 to release energy; at t2~t3, the drive circuit controls the switch tubes VT3 and VT8 to turn off, VT4 and VT7 to turn on, the first inductor 5 releases energy, and the second inductor 6 stores energy; the switching process of t3~t4 is the same as that of t1~t2.

[0046] Figure 3 This is the working mode diagram when the duty cycle D=0.5 in the forward Boost mode. At t0~t1, the drive circuit controls the switch tubes VT3 and VT8 to turn on, the switch tubes VT7 and VT4 to turn off, the first inductor 5 stores energy, and the second inductor 6 releases energy; at t1~t2, the drive circuit controls the switch tubes VT3 and VT8 to turn off, the switch tubes VT7 and VT4 to turn on, the first inductor 5 releases energy, and the second inductor 6 stores energy.

[0047] Figure 4This is the working mode diagram when the duty cycle D>0.5 in the forward Boost mode. At t0~t1, the drive circuit controls the switch tubes VT3 and VT7 to turn on, VT4 and VT8 to turn off, and the first inductor 5 and the second inductor 6 to store energy; at t1~t2, the drive circuit controls the switch tubes VT3 and VT8 to turn on, VT4 and VT7 to turn off, the first inductor 5 to store energy, and the second inductor 6 to release energy; the switching process of t2~t3 is the same as that of t1~t2; at t3~t4, the drive circuit controls the switch tubes VT3 and VT8 to turn off, VT4 and VT7 to turn on, the first inductor 5 to release energy, and the second inductor 6 to store energy.

[0048] 2. The bidirectional DC-DC converter operates in reverse Buck mode.

[0049] When the bidirectional DC-DC converter works in the reverse Buck mode, the switch tubes VT1 and VT5 remain turned on, VT2 and VT6 remain turned off, VT4 and VT8 work at a certain duty cycle, and VT3 and VT7 work at a complementary duty cycle with dead time. According to the duty cycle D of the switch tubes VT4 and VT8, the Buck mode can be divided into three states: D<0.5, D=0.5, D>0.5.

[0050] Figure 5 This is the working mode diagram when the duty cycle D<0.5 in the reverse Buck mode. At t0~t1, the drive circuit controls the switch tubes VT4 and VT7 to turn on, the switch tubes VT3 and VT8 to turn off, the first inductor 5 stores energy, and the second inductor 6 releases energy; at t1~t2, the drive circuit controls the switch tubes VT4 and VT8 to turn off; the switch tubes VT3 and VT8 to turn on, the first inductor 5 and the second inductor 6 release energy; at t2~t3, the drive circuit controls the switch tubes VT3 and VT8 to turn on, VT4 and VT7 to turn off, the first inductor 5 releases energy, and the second inductor 6 stores energy; the switching process of t3~t4 is the same as that of t1~t2.

[0051] Figure 6 This is the working mode diagram when the duty cycle D=0.5 in the reverse Buck mode. At t0~t1, the drive circuit controls the switch tubes VT4 and VT7 to turn on, the switch tubes VT3 and VT8 to turn off, the first inductor 5 stores energy, and the second inductor 6 releases energy; at t1~t2, the drive circuit controls the switch tubes VT3 and VT8 to turn off, VT4 and VT7 to turn on, the first inductor 5 releases energy, and the second inductor 6 stores energy.

[0052] Figure 7It is the working mode diagram when the duty cycle D>0.5 in the reverse Buck mode. From t0 to t1, the driving circuit controls the switch tubes VT4 and VT8 to conduct, and the switch tubes VT3 and VT7 to turn off. The first inductor 5 and the second inductor 6 store energy. From t1 to t2, the driving circuit controls the switch tubes VT4 and VT7 to conduct, and the switch tubes VT3 and VT8 to turn off. The first inductor 5 stores energy, and the second inductor 6 releases energy; the switching process from t2 to t3 is the same as that from t0 to t1; from t3 to t4, the driving circuit controls the switch tubes VT4 and VT7 to turn off, and VT3 and VT8 to conduct. The first inductor 5 releases energy, and the second inductor 6 stores energy.

[0053] 3. The bidirectional DC-DC converter operates in the forward Buck-Boost mode.

[0054] The switch tubes VT1, VT3, VT5, and VT7 operate with a certain duty cycle, and VT2, VT4, VT6, and VT8 operate with a complementary duty cycle with dead time. Figure 8 It is the equivalent circuit diagram of the interleaved parallel connection of the upper Boost converter and the lower Buck converter when the bidirectional DC-DC converter in the embodiment of the present invention operates in the forward Buck-Boost mode. Fig. 9 It is the equivalent circuit diagram of the interleaved parallel connection of the upper Buck converter and the lower Boost converter when the bidirectional DC-DC converter in the embodiment of the present invention operates in the forward Buck-Boost mode.

[0055] It should be noted that according to the magnitudes of the first power supply 9 and the second power supply 10, the forward Buck-Boost mode can be further divided into two cases, namely V1>V2 and V1<V2. To avoid repetition, only the case where the duty cycles D1 of VT1 and VT5 are equal and D1>0.5, and VT2 and VT6 operate with a complementary duty cycle with dead time; the duty cycles D2 of VT3 and VT7 are equal and D2<0.5, and VT4 and VT8 operate with a complementary duty cycle with dead time, that is, V1>V2, is taken as an example to analyze the forward Buck-Boost mode. The switching processes of the other duty cycle combinations are similar.

[0056] When V1>V2, the bidirectional DC-DC converter switches from the forward Buck mode to the forward Buck-Boost mode. Fig.10This is the working mode diagram of the forward Buck-Boost mode. At t0~t1, the first phase circuit is in the Buck discharge mode, the drive circuit controls the switch tube VT1 to turn off, VT2 to turn on, the first inductor 5 releases energy, the second phase circuit is in the Boost charging mode, the drive circuit controls the switch tube VT7 to turn on, VT8 to turn off, and the second inductor 6 stores energy; at t1~t2, the first phase circuit is in the Buck charging mode, the drive circuit controls the switch tube VT1 to turn on, VT2 to turn off, the first inductor 5 stores energy, the second phase circuit is in the Boost discharge mode, the drive circuit controls the switch tube VT7 to turn off, VT8 to turn on, because V1>V2, the second inductor 6 still stores energy; From t2 to t3, the first phase circuit is in the Boost charging mode, the drive circuit controls the switch tube VT3 to be turned on, VT4 to be turned off, the first inductor 5 stores energy, and the second phase circuit is in the Buck discharge mode, the drive circuit controls the switch tube VT5 to be turned off, VT6 to be turned on, and the second inductor 6 releases energy; from t3 to t4, the first phase circuit is in the Boost discharge mode, the drive circuit controls the switch tube VT4 to be turned on, VT3 to be turned off, since V1>V2, the first inductor 5 still releases energy, and the second phase circuit is in the Buck charging mode, the drive circuit controls the switch tube VT6 to be turned off, VT5 to be turned on, and the second inductor 6 stores energy.

[0057] The above is a detailed introduction to a bidirectional DC-DC converter for a vehicle-mounted dual power supply system provided by the present invention. In this specification, relational terms such as first and second, etc. are only used to distinguish two different entities, and no actual order is required between these entities or operations.

Claims

1. A bidirectional DC-DC converter for a vehicle-mounted dual power supply system, characterized in that: A two-phase staggered parallel bidirectional four-switch Buck-Boost circuit is used as the basic topology of the bidirectional DC-DC converter, and the basic topology structure includes four groups of bridge arm circuits and a first energy storage inductor, a second energy storage inductor, a first power supply, a second power supply, a generator, a first capacitor and a second capacitor; the four groups of bridge arm circuits include a first group of bridge arms, a second group of bridge arms, a third group of bridge arms and a fourth group of bridge arms, wherein the first group of bridge arms and the first energy storage inductor and the second group of bridge arms constitute a first-phase bidirectional DCDC circuit; the third group of bridge arms and the second energy storage inductor and the fourth group of bridge arms constitute a second-phase bidirectional DCDC circuit; The first bridge arm group is composed of switch tubes VT1 and VT2, the second bridge arm group is composed of switch tubes VT3 and VT4, the third bridge arm group is composed of switch tubes VT5 and VT6, and the fourth bridge arm group is composed of switch tubes VT7 and VT8. The source of the switch tube VT1 is connected to the drain of the switch tube VT2, and is connected to the first end of the first energy storage inductor as the common end of the first group of bridge arms. The drain of the switch tube VT1 is connected to the first end of the first capacitor and the first end of the generator as the first end of the first group of bridge arms. The source of the switch tube VT2 is connected to the second end of the first capacitor and the second end of the generator as the second end of the first group of bridge arms. The drain of the switch tube VT3 is connected to the source of the switch tube VT4 and is connected to the second end of the second energy storage inductor as the common end of the second group of bridge arms. The drain of the switch tube VT4 is connected to the first end of the second capacitor as the first end of the second group of bridge arms. The source of the switch tube VT3 is connected to the second end of the second capacitor as the second end of the second group of bridge arms. The source of the switch tube VT5 is connected to the drain of the switch tube VT6, and is connected to the first end of the second energy storage inductor as the common end of the third group of bridge arms. The drain of the switch tube VT5 is connected to the first end of the first capacitor and the first end of the generator as the first end of the third group of bridge arms. The source of the switch tube VT5 is connected to the second end of the first capacitor and the generator as the second end of the third group of bridge arms. The drain of the switch tube VT7 is connected to the source of the switch tube VT8 and is connected to the second end of the second energy storage inductor as the common end of the fourth group of bridge arms. The drain of the switch tube VT8 is connected to the first end of the second capacitor as the first end of the fourth group of bridge arms. The source of the switch tube VT7 is connected to the second end of the second capacitor as the second end of the fourth group of bridge arms.

2. A bidirectional DC-DC converter for a vehicle-mounted dual power supply system according to claim 1, characterized in that: Each switch tube has a diode connected in reverse parallel with it to play the role of freewheeling.

3. The bidirectional DC-DC converter for a vehicle-mounted dual power supply system according to claim 1, characterized in that: The eight switch tubes are all NMOS tubes.

4. The bidirectional DC-DC converter for a vehicle-mounted dual power supply system according to claim 1, characterized in that: The first capacitor and the second capacitor have the same parameters.

5. The bidirectional DC-DC converter for a vehicle-mounted dual power supply system according to claim 1, characterized in that: The parameters of the first energy storage inductor and the second energy storage inductor are the same.

6. The bidirectional DC-DC converter for a vehicle-mounted dual power supply system according to claim 1, characterized in that: The first power source adopts a lead-acid battery, that is, the original vehicle battery, and the second power source adopts a lithium battery pack.

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