A bidirectional buck-boost circuit for battery charging and discharging and a control method thereof

Abstract

The application belongs to the technical field of battery charging and discharging, and discloses a bidirectional voltage reduction-voltage increase circuit and a control method for battery charging and discharging, which comprises a voltage reduction-voltage increase switching control circuit, a double-tube main power voltage reduction-voltage increase circuit and a charging and discharging current sampling switching circuit; the voltage reduction-voltage increase switching control circuit is electrically connected with the double-tube main power voltage reduction-voltage increase circuit, and the double-tube main power voltage reduction-voltage increase circuit is electrically connected with the charging and discharging current sampling switching circuit. The application adopts a double-tube BUCK-BOOST topological structure, can realize BUCK charging function and reverse BOOST discharging function, has obvious cost and size advantages, and adopts analog power chip control, does not need complex control algorithm, and only needs to control PWM wave output through hardware logic.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery charging and discharging, and particularly relates to a bidirectional buck-boost circuit and control method for battery charging and discharging. BACKGROUND

[0002] With the development of energy storage technology, batteries, as a key component, play a crucial role. In the battery manufacturing process, battery formation is an important process step, which is a charging process for the battery after liquid injection. The purpose is to change the battery from a "pile of materials" to a stable "electrochemical system". At the same time, before the battery is shipped, it must undergo multiple charge and discharge cycle tests.

[0003] In the charging and discharging system, the main function of the bidirectional BUCK-BOOST circuit is to reduce the high voltage to the voltage suitable for the battery during charging, and to boost the battery voltage to the required high voltage during discharging, and then convert it to mains power through an inverter to feed back to the grid. The current design scheme usually includes the following two kinds:

[0004] Independent BUCK and BOOST circuits: This scheme uses a BUCK circuit and a BOOST circuit, which can only work separately during charging and discharging, thereby increasing the cost and volume;

[0005] Dual-tube or four-tube scheme with shared power tube: This scheme uses a shared power tube to realize the BUCK and BOOST functions, and can be flexibly switched during charging and discharging. However, when using this scheme, an MCU (Micro Control Unit) is usually required for precise control, and a complex control algorithm is needed to adjust the working state of the circuit.

[0006] Therefore, how to provide a bidirectional buck-boost circuit and control method for battery charging and discharging is a problem to be solved at present. SUMMARY

[0007] The embodiment of the present application provides a bidirectional buck-boost circuit and control method for battery charging and discharging, to solve the problem of relying on a complex control algorithm to adjust the working state of the circuit in the prior art.

[0008] The following presents a simplified summary of some aspects of the disclosed embodiments. This summary is not an extensive overview of the application. It is not intended to identify key / critical elements of the embodiments or to delineate the scope thereof. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.

[0009] According to a first aspect of the embodiment of the present application, a bidirectional buck-boost circuit for battery charging and discharging is provided.

[0010] In one embodiment, the bidirectional step-down / step-up circuit for battery charging and discharging comprises a step-down / step-up switching control circuit, a double-tube main power step-down / step-up circuit, and a charging and discharging current sampling switching circuit.

[0011] The step-down / step-up switching control circuit is electrically connected to the double-tube main power step-down / step-up circuit, and the double-tube main power step-down / step-up circuit is electrically connected to the charging and discharging current sampling switching circuit.

[0012] In one embodiment, the step-down / step-up switching control circuit comprises a power supply chip U1, an inverter U2, an AND gate U3, an AND gate U4, an AND gate U5, an NAND gate U6, a half-bridge driving chip U7, an operational amplifier U8, an operational amplifier U9, an operational amplifier U10, an operational amplifier U11, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a capacitor C1, a capacitor C2, a capacitor C3, a diode D1, a diode D2, and a diode D3.

[0013] The power supply chip U1 inputs a PWM signal to one end of the inverter U2 and the first pin of the NAND gate U6, the second pin of the NAND gate U6 is connected to a MODE signal, the other end of the inverter U2 is connected to the first pin of the AND gate U3, the second pin of the AND gate U3 is connected to the MODE signal, the third pin of the AND gate U3 is connected to the first pin of the AND gate U4, the second pin of the AND gate U4 is connected to the first pin of the AND gate U5 and an EN signal, the second pin of the AND gate U5 is connected to the third pin of the NAND gate U6, the third pin of the AND gate U4 is connected to the HIN pin of the half-bridge driving chip U7, the third pin of the AND gate U5 is connected to the LIN pin of the half-bridge driving chip U7, the VS pin of the half-bridge driving chip U7 is connected to one end of the capacitor C1, the other end of the capacitor C1 is respectively connected to the VB pin of the half-bridge driving chip U7 and the negative electrode of the diode D1, the negative electrode of the diode D1 is connected to the VCC pin of the half-bridge driving chip U7.

[0014] The Comp pin of the power chip U1 is connected with the negative pole of the diode D2 and the negative pole of the diode D3 respectively, the positive pole of the diode D2 is connected with one end of the capacitor C2 and the output end of the operational amplifier U11 respectively, the other end of the capacitor C2 is connected with one end of the resistor R12, the other end of the resistor R12 is connected with the negative phase input end of the operational amplifier U11 and one end of the resistor R7 respectively, the other end of the resistor R7 sets the voltage value VSET, the same phase input end of the operational amplifier U11 is connected with one end of the resistor R6 and the output end of the operational amplifier U8 through the resistor R8 respectively, the other end of the resistor R6 is connected with the negative phase input end of the operational amplifier U8 and one end of the resistor R1 respectively, the other end of the resistor R1 is connected with the negative pole of the battery, the same phase input end of the operational amplifier U8 is connected with one end of the resistor R2 and one end of the resistor R14 respectively, the other end of the resistor R2 is connected with the positive pole of the battery, the other end of the resistor R14 is connected with the ground, the positive pole of the diode D3 is connected with one end of the capacitor C3 and the output end of the operational amplifier U10 respectively, the other end of the capacitor C3 is connected with one end of the resistor R11, the other end of the resistor R11 is connected with the negative phase input end of the operational amplifier U10 and one end of the resistor R9 respectively, the other end of the resistor R9 sets the current value ISET, the same phase input end of the operational amplifier U10 is connected with one end of the resistor R10, the other end of the resistor R10 is connected with one end of the resistor R5 and the output end of the operational amplifier U9 respectively, the other end of the resistor R5 is connected with the negative phase input end of the operational amplifier U9 and one end of the resistor R3 respectively, the same phase input end of the operational amplifier U9 is connected with one end of the resistor R4 and one end of the resistor R13 respectively, the other end of the resistor R13 is connected with the ground, the other end of the resistor R3 and the other end of the resistor R4 are connected with the charge-discharge current sampling feedback voltage respectively.

[0015] In one embodiment, the operational amplifier U8, the resistor R6, the resistor R1, the resistor R2 and the resistor R14 in the buck-boost switching control circuit form a differential amplification circuit, and the differential amplification circuit is used for sampling and amplifying the battery voltage.

[0016] In one embodiment, the resistor R7, the resistor R8, the resistor R12, the capacitor C2, the operational amplifier U11 and the diode D2 in the buck-boost switching control circuit form a voltage loop error amplifier, and the voltage loop error amplifier is used to respond to the change of the battery voltage and provide a comparison value for the power chip U1 to generate a PWM signal.

[0017] In one embodiment, the double-tube main power step-down and step-up circuit comprises a capacitor C4, a capacitor C5, a field effect transistor VT2, a field effect transistor VT3, a diode D4, a diode D5, an inductor L1, a resistor R_Isense, a relay switch S1, and a battery VBAT.

[0018] The positive pole of the capacitor C4 is connected with the VIN end, the negative pole of the diode D4, and the drain of the field effect transistor VT2, the gate of the field effect transistor VT2 is connected with the Ho_driver end, the source of the field effect transistor VT2 is connected with the positive pole of the diode D4, the VS end, one end of the inductor L1, the drain of the field effect transistor VT3, and the negative pole of the diode D5, the other end of the inductor L1 is connected with the I- end, one end of the resistor R_Isense, and the positive pole of the capacitor C5, the other end of the resistor R_Isense is connected with the I+ end and one end of the relay switch S1, the other end of the relay switch S1 is connected with the positive pole of the battery VBAT, the negative pole of the battery VBAT is connected with the negative pole of the capacitor C5, the positive pole of the diode D5, the source of the field effect transistor VT3, and the negative pole of the capacitor C4 and grounded, and the gate of the field effect transistor VT3 is connected with the Lo_driver end.

[0019] In one embodiment, the capacitor C4 is an input capacitor, the capacitor C5 is an output capacitor, and the resistor R_Isense is a charge and discharge current sampling resistor.

[0020] In one embodiment, the charge and discharge current sampling switching circuit comprises an analog switch chip U11, a resistor R15, a resistor R16, and a triode VT1.

[0021] The S1 pin and the S3 pin of the analog switch chip U11 are connected with the I- end, the S2 pin and the S4 pin of the analog switch chip U11 are connected with the I+ end, the D1 pin and the D2 pin of the analog switch chip U11 are connected with the I— end, the D3 pin and the D4 pin of the analog switch chip U11 are connected with the I++ end, the IN4 pin of the analog switch chip U11 is connected with the MODE signal, the IN1 pin of the analog switch chip U11 is connected with the MODE signal and one end of the resistor R16, the other end of the resistor R16 is connected with the base of the triode VT1, the collector of the triode VT1 is connected with the resistor R15, the IN2 pin of the analog switch chip U11, and the IN3 pin of the analog switch chip U11, and the emitter of the triode VT1 is grounded.

[0022] In one embodiment, the charge-discharge current sampling switching circuit realizes automatic switching of current sampling according to the MODE signal, and ensures that the output of the differential amplification circuit is a positive voltage.

[0023] In one embodiment, the input of the analog switch chip U11 is IN1 pin, IN2 pin, IN3 pin and IN4 pin respectively, and the IN1 pin controls the switch of S1 pin and D1 pin, the IN2 pin controls the switch of S2 pin and D2 pin, the IN3 pin controls the switch of S3 pin and D3 pin, and the IN4 pin controls the switch of S4 pin and D4 pin.

[0024] According to a second aspect of the embodiment of the present application, a control method of a bidirectional buck-boost circuit for battery charging and discharging is provided.

[0025] In one embodiment, the control method of the bidirectional buck-boost circuit for battery charging and discharging comprises:

[0026] When the relay switch S1 is opened, and the EN signal and the MODE signal are both in high level state, the PWM signal is output through the Ho_driver pin of the half-bridge drive chip U7, and the Lo_driver pin of the half-bridge drive chip U7 is always in low level state, at this time, the double-tube main power buck-boost circuit is in the buck charging mode, and the field effect tube VT2 and the diode D5 start to work to realize battery charging.

[0027] When the relay switch S1 is opened, and the EN signal is in high level state and the MODE signal is in low level state, the PWM signal is output through the Lo_driver pin of the half-bridge drive chip U7, and the Ho_driver pin of the half-bridge drive chip U7 is always in low level state, at this time, the double-tube main power buck-boost circuit is in the boost discharging mode, and the field effect tube VT3 and the diode D4 start to work to realize battery discharging.

[0028] When the relay switch S1 is opened, and the EN signal and the MODE signal are both in low level state, the Ho_driver pin and the Lo_driver pin of the half-bridge drive chip U7 are both in low level state, at this time, the battery stops charging and discharging.

[0029] The technical scheme provided by the embodiment of the present application can include the following beneficial effects:

[0030] The application adopts a double-tube BUCK-BOOST topology structure, can realize BUCK charging function and reverse BOOST discharging function, has obvious cost and volume advantages, adopts analog power chip control, does not need complex control algorithm, and only needs to control PWM wave output through hardware logic; the application can realize control on the upper tube through hardware control on the PWM wave output by the power chip, thereby completing the BUCK charging function; meanwhile, the reverse BOOST discharging function can be realized through control on the lower tube, thereby not only effectively reducing the cost and volume, but also adopting pure hardware control, so that the scheme is simple and reliable.

[0031] It should be understood that the foregoing general description and the following detailed description are only exemplary and explanatory and are not restrictive of the application. BRIEF DESCRIPTION OF DRAWINGS

[0032] The accompanying drawings incorporated in and forming a part of the specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the application.

[0033] Figure 1 is a principle block diagram of a bidirectional buck-boost circuit for battery charging and discharging according to an exemplary embodiment;

[0034] Figure 2 is a flow chart of a control method of a bidirectional buck-boost circuit for battery charging and discharging according to an exemplary embodiment;

[0035] Figure 3 is a circuit diagram of a buck-boost switching control circuit in a bidirectional buck-boost circuit for battery charging and discharging according to an exemplary embodiment;

[0036] Figure 4 is a circuit diagram of a double-tube main power buck-boost circuit in a bidirectional buck-boost circuit for battery charging and discharging according to an exemplary embodiment;

[0037] Figure 5 is a circuit diagram of a charging and discharging current sampling switching circuit in a bidirectional buck-boost circuit for battery charging and discharging according to an exemplary embodiment;

[0038] Figure 6 is a charging and discharging control flow chart of a control method of a bidirectional buck-boost circuit for battery charging and discharging according to an exemplary embodiment. DETAILED DESCRIPTION

[0039] The following description and drawings are illustrative of specific embodiments thereof and are not intended to limit the scope of the embodiments. Parts and features of some embodiments can be included or substituted in or for parts and features of other embodiments. The scope of the embodiments encompassed herein includes the whole scope of the claims together with all available equivalents of the claims. In this document, the terms "first", "second", etc. are used merely to distinguish one element from another, and do not require or imply any actual relationship or order between the elements. In fact, the first element can be referred to as the second element, and vice versa. Also, the terms "comprises", "comprising", or any other variations thereof are intended to cover a non-exclusive inclusion, such that a structure, device, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such structure, device, or apparatus. Without further limitation, an element defined by an "includes a" statement does not exclude the presence of additional identical elements in the structure, device, or apparatus that includes the element. Various embodiments are described in progressive stages, each of which focuses on the differences from other embodiments, and the same or similar parts between various embodiments can be referred to each other.

[0040] The terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, as used herein, indicate relative positions or orientation relationships based on the positions or orientation relationships shown in the drawings, and are only used for the convenience of description herein and simplification of description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In the description herein, unless otherwise specified and limited, the terms "mount", "connect", "connection" should be interpreted broadly, for example, it can be a mechanical connection or an electrical connection, it can be a communication between two elements inside, it can be a direct connection or an indirect connection through an intermediate medium, and the specific meaning of the above terms can be understood by those skilled in the art according to the specific circumstances.

[0041] In this document, the term "multiple" means two or more, unless otherwise specified.

[0042] In this document, the character " / " represents an "or" relationship between the objects before and after it. For example, A / B means A or B.

[0043] In this document, the term "and / or" is a description of the relationship between the objects, which means that there can be three relationships. For example, A and / or B means that there are three relationships of A or B, or A and B.

[0044] It should be understood that although the steps in the flowchart are shown in sequential order, such that each step depends on completion of the previous step before commencement of the next step, the steps are not necessarily performed in the order shown by the arrows. Unless otherwise explicitly stated herein, the steps are not necessarily performed in the order shown, and the steps can be performed in other orders. Moreover, at least some of the steps in the figure can include multiple sub-steps or multiple stages, which are not necessarily performed at the same time, and which can be performed in different orders, and which can be performed in alternating or interleaved fashion with other steps or sub-steps or stages of other steps.

[0045] The various modules in the device or system of the present application can be implemented in whole or in part by software, hardware, and combinations thereof. The various modules described above can be embedded in or independent of a processor in a computer device in hardware form, or stored in a memory in a computer device in software form, so as to be called and executed by a processor to perform the operations corresponding to the various modules.

[0046] In the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0047] Figure 1 An embodiment of a bidirectional buck-boost circuit for battery charging and discharging is shown.

[0048] In this alternative embodiment, the bidirectional buck-boost circuit for battery charging and discharging includes a buck-boost switching control circuit 1, a double-tube main power buck-boost circuit 2, and a charging and discharging current sampling switching circuit 3.

[0049] The buck-boost switching control circuit 1 is electrically connected to the double-tube main power buck-boost circuit 2, and the double-tube main power buck-boost circuit 2 is electrically connected to the charging and discharging current sampling switching circuit 3.

[0050] In this alternative embodiment, as shown in Figure 3 The buck-boost switching control circuit 1 includes a power supply chip U1, an inverter U2, an AND gate U3, an AND gate U4, an AND gate U5, an NAND gate U6, a half-bridge driving chip U7, an operational amplifier U8, an operational amplifier U9, an operational amplifier U10, an operational amplifier U11, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a capacitor C1, a capacitor C2, a capacitor C3, a diode D1, a diode D2, and a diode D3.

[0051] The power supply chip U1 inputs a PWM signal to one end of the inverter U2 and the first pin of the NAND gate U6, the second pin of the NAND gate U6 is connected with the MODE signal, the other end of the inverter U2 is connected with the first pin of the AND gate U3, the second pin of the AND gate U3 is connected with the MODE signal, the third pin of the AND gate U3 is connected with the first pin of the AND gate U4, the second pin of the AND gate U4 is connected with the first pin of the AND gate U5 and the EN signal, the second pin of the AND gate U5 is connected with the third pin of the NAND gate U6, the third pin of the AND gate U4 is connected with the HIN pin of the half-bridge drive chip U7, the third pin of the AND gate U5 is connected with the LIN pin of the half-bridge drive chip U7, the VS pin of the half-bridge drive chip U7 is connected with one end of the capacitor C1, the other end of the capacitor C1 is connected with the VB pin of the half-bridge drive chip U7 and the negative electrode of the diode D1 respectively, the negative electrode of the diode D1 is connected with the VCC pin of the half-bridge drive chip U7;

[0052] The Comp pin of the power chip U1 is connected with the negative pole of the diode D2 and the negative pole of the diode D3 respectively, the positive pole of the diode D2 is connected with one end of the capacitor C2 and the output end of the operational amplifier U11 respectively, the other end of the capacitor C2 is connected with one end of the resistor R12, the other end of the resistor R12 is connected with the negative phase input end of the operational amplifier U11 and one end of the resistor R7 respectively, the other end of the resistor R7 sets the voltage value VSET, the same phase input end of the operational amplifier U11 is connected with one end of the resistor R6 and the output end of the operational amplifier U8 through the resistor R8 respectively, the other end of the resistor R6 is connected with the negative phase input end of the operational amplifier U8 and one end of the resistor R1 respectively, the other end of the resistor R1 is connected with the negative pole of the battery, the same phase input end of the operational amplifier U8 is connected with one end of the resistor R2 and one end of the resistor R14 respectively, the other end of the resistor R2 is connected with the positive pole of the battery, the other end of the resistor R14 is connected with the ground, the positive pole of the diode D3 is connected with one end of the capacitor C3 and the output end of the operational amplifier U10 respectively, the other end of the capacitor C3 is connected with one end of the resistor R11, the other end of the resistor R11 is connected with the negative phase input end of the operational amplifier U10 and one end of the resistor R9 respectively, the other end of the resistor R9 sets the current value ISET, the same phase input end of the operational amplifier U10 is connected with one end of the resistor R10, the other end of the resistor R10 is connected with one end of the resistor R5 and the output end of the operational amplifier U9 respectively, the other end of the resistor R5 is connected with the negative phase input end of the operational amplifier U9 and one end of the resistor R3 respectively, the same phase input end of the operational amplifier U9 is connected with one end of the resistor R4 and one end of the resistor R13 respectively, the other end of the resistor R13 is connected with the ground, the other end of the resistor R3 and the other end of the resistor R4 are connected with the charge-discharge current sampling feedback voltage respectively.

[0053] In the optional embodiment, the operational amplifier U8, the resistor R6, the resistor R1, the resistor R2 and the resistor R14 in the buck-boost switching control circuit 1 form a differential amplification circuit, and the differential amplification circuit is used for sampling and amplifying the battery voltage.

[0054] In the optional embodiment, the resistor R7, the resistor R8, the resistor R12, the capacitor C2, the operational amplifier U11 and the diode D2 in the buck-boost switching control circuit 1 form a voltage loop error amplifier, and the voltage loop error amplifier is used for responding to the change of the battery voltage and providing a comparison value for the power chip U1 to generate a PWM signal.

[0055] In the optional embodiment, as shown in Figure 4As shown, the double-tube main power step-down and step-up circuit 2 comprises a capacitor C4, a capacitor C5, a field effect transistor VT2, a field effect transistor VT3, a diode D4, a diode D5, an inductor L1, a resistor R_Isense, a relay switch S1 and a battery VBAT.

[0056] The positive pole of the capacitor C4 is connected with the VIN end, the negative pole of the diode D4 and the drain of the field effect transistor VT2, the gate of the field effect transistor VT2 is connected with the Ho_driver end, the source of the field effect transistor VT2 is connected with the positive pole of the diode D4, the VS end, one end of the inductor L1, the drain of the field effect transistor VT3 and the negative pole of the diode D5, the other end of the inductor L1 is connected with the I- end, one end of the resistor R_Isense and the positive pole of the capacitor C5, the other end of the resistor R_Isense is connected with the I+ end and one end of the relay switch S1, the other end of the relay switch S1 is connected with the positive pole of the battery VBAT, the negative pole of the battery VBAT is connected with the negative pole of the capacitor C5, the positive pole of the diode D5, the source of the field effect transistor VT3 and the negative pole of the capacitor C4 and grounded, and the gate of the field effect transistor VT3 is connected with the Lo_driver end.

[0057] In this optional embodiment, the capacitor C4 is an input capacitor, the capacitor C5 is an output capacitor, and the resistor R_Isense is a charge and discharge current sampling resistor.

[0058] In this optional embodiment, as shown, Figure 5 As shown, the charge and discharge current sampling switching circuit 3 comprises an analog switch chip U11, a resistor R15, a resistor R16 and a triode VT1.

[0059] The S1 pin and the S3 pin of the analog switch chip U11 are connected with the I- end, the S2 pin and the S4 pin of the analog switch chip U11 are connected with the I+ end, the D1 pin and the D2 pin of the analog switch chip U11 are connected with the I- end, the D3 pin and the D4 pin of the analog switch chip U11 are connected with the I++ end, the IN4 pin of the analog switch chip U11 is connected with the MODE signal, the IN1 pin of the analog switch chip U11 is connected with the MODE signal and one end of the resistor R16, the other end of the resistor R16 is connected with the base of the triode VT1, the collector of the triode VT1 is connected with the resistor R15, the IN2 pin of the analog switch chip U11 and the IN3 pin of the analog switch chip U11, and the emitter of the triode VT1 is grounded.

[0060] In the optional embodiment, the charge-discharge current sampling switch circuit 3 realizes automatic switching of current sampling according to the MODE signal, and ensures that the output of the differential amplification circuit is a positive voltage.

[0061] In the optional embodiment, the input of the analog switch chip U11 is IN1 pin, IN2 pin, IN3 pin and IN4 pin respectively, and the IN1 pin controls the switch of S1 pin and D1 pin, the IN2 pin controls the switch of S2 pin and D2 pin, the IN3 pin controls the switch of S3 pin and D3 pin, and the IN4 pin controls the switch of S4 pin and D4 pin.

[0062] Figure 2 An embodiment of a control method of a bidirectional buck-boost circuit for battery charging and discharging of the application is shown.

[0063] In the optional embodiment, the control method of the bidirectional buck-boost circuit for battery charging and discharging comprises:

[0064] S201, when the relay switch S1 is opened, and the EN signal and the MODE signal are both in high level state, the PWM signal is output through the Ho_driver pin of the half-bridge drive chip U7, and the Lo_driver pin of the half-bridge drive chip U7 is always in low level state, at this time the double-tube main power buck-boost circuit 2 is in buck charging mode, and the field effect tube VT2 and the diode D5 start to work to realize battery charging;

[0065] S203, when the relay switch S1 is opened, and the EN signal is in high level state and the MODE signal is in low level state, the PWM signal is output through the Lo_driver pin of the half-bridge drive chip U7, and the Ho_driver pin of the half-bridge drive chip U7 is always in low level state, at this time the double-tube main power buck-boost circuit 2 is in boost discharging mode, and the field effect tube VT3 and the diode D4 start to work to realize battery discharging;

[0066] S205, when the relay switch S1 is opened, and the EN signal and the MODE signal are in low level state, the Ho_driver pin and the Lo_driver pin of the half-bridge drive chip U7 are both in low level state, at this time the battery stops charging and discharging.

[0067] In order to facilitate the understanding of the above technical solutions of the application, the bidirectional buck-boost circuit for battery charging and discharging and the control method of the application in the actual process are described in detail as follows:

[0068] A bidirectional BUCK-BOOST circuit for battery charging and discharging (the bidirectional BUCK-BOOST circuit is a circuit capable of realizing the mutual conversion of voltage during charging and discharging, which integrates the functions of voltage reduction BUCK and voltage increase BOOST, and thus can support battery charging and discharging at the same time, namely, a bidirectional voltage reduction-increase circuit) comprises a PWM control and BUCK-BOOST switching control circuit (equivalent to a voltage reduction-increase switching control circuit), a double-tube main power BUCK-BOOST circuit (equivalent to a double-tube main power voltage reduction-increase circuit), and a charging and discharging current sampling switching circuit (equivalent to a charging and discharging current sampling switching circuit).

[0069] The working principles between the respective circuits are as follows:

[0070] 1. BUCK charging (voltage reduction charging): the EN signal and the MODE signal are high, the charging and discharging current sampling switching circuit sends an output charging current signal into the PWM control and BUCK-BOOST switching control circuit for differential amplification according to the MODE signal; the PWM control and BUCK-BOOST switching control circuit outputs a PWM driving signal according to the output charging current and the battery voltage signal; the PWM signal drives the high-side MOS tube of the double-tube main power BUCK-BOOST circuit to work.

[0071] 2. BOOST discharging (voltage increase discharging): the EN signal is high and the MODE signal is low, the charging and discharging current sampling switching circuit sends a discharging current signal into the PWM control and BUCK-BOOST switching control circuit for differential amplification according to the MODE signal; the PWM control and BUCK-BOOST switching control circuit outputs a PWM driving signal according to the discharging current signal; the PWM signal drives the low-side MOS tube (field effect tube) of the double-tube main power BUCK-BOOST circuit to work.

[0072] The PWM control and BUCK-BOOST switching control circuit comprises: operational amplifier U8, operational amplifier U9, operational amplifier U10, operational amplifier U11, resistor R1, resistor R2, resistor R3, resistor R4, resistor R5, resistor R6, resistor R7, resistor R8, resistor R9, resistor R10, resistor R11, resistor R12, resistor R13, resistor R14, capacitor C2, capacitor C3, diode D2, diode D3, power supply chip U1 constitutes a PWM control circuit, realizes voltage and current double closed loop control, V+ and V- are battery feedback voltages, I++ and I-- are charge and discharge current sampling feedback voltages, the voltage loop and the current loop compete for priority through diode D2 and diode D3, the value greater than the value enters the Comp pin of the power supply chip U1, and the power supply chip U1 is controlled internally to output a PWM wave, wherein the low level of the PWM is an effective duty cycle; the inverter U2, the AND gate U3, the AND gate U4, the AND gate U5, the NAND gate U6, the half-bridge drive chip U7, the capacitor C1 and the diode D1 constitute a BUCK-BOOST switching control circuit (BUCK-BOOST switching control circuit), realize BUCK and BOOST mode switching, and provide driving for the power tube of the double-tube main power BUCK-BOOST circuit; the main hardware implementation logic is:

[0073] 1, BUCK charging (the EN signal is high, and the MODE signal is high): ① when the PWM is low, the inverter U2 outputs high, the AND gate U3 outputs high, the AND gate U4 outputs high, that is, HIN is high, and the Ho_driver of the half-bridge drive chip U7 is high; when the PWM is high, the inverter U2 outputs low, the AND gate U3 outputs low, the AND gate U4 outputs low, that is, HIN is low, and the Ho_driver of the half-bridge drive chip U7 is low; therefore, the Ho_driver is controlled by the PWM output by the power supply chip U1; ② the MODE is high, the NAND gate U6 always outputs low, the AND gate U5 always outputs low, that is, LIN is always low, therefore, the Lo_driver is always low, and is not controlled by the PWM output by the power supply chip; ③ the Ho_driver is used for controlling the upper tube, and the Lo_driver is used for controlling the lower tube; therefore, the BUCK charging function can be realized.

[0074] 2、BOOST discharge (EN is high, MODE is low): ① MODE is low, and the AND gate U3 always outputs low, and the AND gate U4 always outputs low, that is, HIN is always low, therefore, Ho_driver is not controlled by the output PWM of the power supply chip; ② when PWM is low, the NAND gate U6 outputs high, and the AND gate U5 outputs high, that is, LIN is high, and the Lo_driver of the half-bridge driving chip U7 is high; when PWM is high, the NAND gate U6 outputs low, and the AND gate U5 outputs low, that is, LIN is low, and the Lo_driver of the half-bridge driving chip U7 is low; therefore, the Lo_driver is controlled by the output PWM of the power supply chip; ③ Ho_driver is used to control the upper tube, and Lo_driver is used to control the lower tube; therefore, the BOOST discharge function can be realized.

[0075] 3、Stop charging and discharging (EN, MODE are low): EN is low, HIN and LIN are both low, Ho_driver and Lo_driver are also both low, and the upper and lower tubes do not work, and the charging and discharging are stopped.

[0076] Among them, the double-tube main power BUCK-BOOST circuit includes: input capacitor C3, MOS tube (field effect tube) VT2, field effect tube VT3, diode D4, diode D5, inductor L1, output capacitor C2, charging and discharging current sampling resistor R_Isense and relay switch S1, and the working principle is as follows:

[0077] 1、BUCK charging: Ho_driver outputs PWM waveform, drives MOS tube VT2 to work, and Lo_driver is always low, and MOS tube VT3 does not work; when Ho_driver is high, the input voltage VIN excites the inductor L1, and at the same time provides energy for the battery; when Ho_driver is low, the inductor L1 flows through the diode D5, and provides energy for the battery.

[0078] 2、BOOST discharge: Lo_driver outputs PWM waveform, drives MOS tube VT3 to work, and Ho_driver is always low, and MOS tube VT2 does not work; when Lo_driver is high, the battery excites the inductor L1, and at the same time the input capacitor C1 provides discharge energy; when Lo_driver is low, the inductor L1 and the battery voltage flow through the diode D4, and provide discharge energy.

[0079] 3、Stop charging and discharging: Ho_driver and Lo_driver are both low, and the double tubes do not work, and the relay switch S1 is disconnected, preventing the battery voltage from being back-primed.

[0080] The charging and discharging current sampling switch circuit comprises an analog switch chip U11, resistors R15 and R16, and a triode VT1; the analog switch chip U11 has inputs IN1, IN2, IN3 and IN4, which control the opening and closing of the S1 pin and the D1 pin, the S2 pin and the D2 pin, the S3 pin and the D3 pin, and the S4 pin and the D4 pin, and are low-level effective; since the directions of the charging and discharging currents are opposite, the circuit can realize automatic switching of current sampling, and the working principle is as follows:

[0081] 1. BUCK charging: the voltage between the charging and discharging current sampling resistors R_Isense is I->I+, the MODE signal is high, the S2 pin and the D2 pin and the S3 pin and the D3 pin are turned on, I++=I- and I--=I+, and the output of the current sampling differential circuit is ensured to be a positive voltage.

[0082] 2. BOOST discharging: the voltage between the charging and discharging current sampling resistors R_Isense is I+>I-, the MODE signal is low, the S1 pin and the D1 pin and the S4 pin and the D4 pin are turned on, I++=I+ and I--=I-, and the output voltage of the current sampling differential circuit is ensured to be a positive voltage.

[0083] The connection mode of the buck-boost switching control circuit, the double-tube main power buck-boost circuit and the charging and discharging current sampling switch circuit will be described in detail below.

[0084] The connection mode of the PWM control and the BUCK-BOOST switching control circuit is as follows:

[0085] 1. One end of the resistor R1 is connected to the negative pole V- of the battery, and the other end is connected to the negative input of the operational amplifier U8; one end of the resistor R2 is connected to the positive pole V+ of the battery, and the other end is connected to the same-phase input of the operational amplifier U8; one end of the resistor R6 is connected to the negative input of the operational amplifier U8, and the other end is connected to the output of the operational amplifier U8; one end of the resistor R14 is connected to the same-phase input of the operational amplifier U8, and the other end is connected to GND; wherein the resistor R1=the resistor R2, and the resistor R14=the resistor R6; the operational amplifier U8, the resistor R6, the resistor R1, the resistor R2 and the resistor R14 constitute a differential amplification circuit for sampling and amplifying the battery voltage; wherein V- is directly connected to the root of the negative pole of the battery, so as to avoid the influence of the line voltage of the power loop on the battery voltage sampling.

[0086] 2、 resistance R8 one end connects the output of operational amplifier U8, one end connects the same phase input of operational amplifier U11; resistance R7 one end connects the set voltage value VSET, one end connects the negative phase input of operational amplifier U11; resistance R12 one end connects the negative phase input of operational amplifier U11, one end connects capacitor C2; capacitor C2 one end connects resistance R12, one end connects the output of operational amplifier U11; diode D2 one end connects the output of operational amplifier U11, one end connects the Comp of power supply chip U1; resistance R7, resistance R8, resistance R12, capacitor C2, operational amplifier U11, diode D2 constitute voltage loop error amplifier, for responding to the change of battery voltage, for power supply chip U1 provides comparison value, thus generating PWM wave.

[0087] 3、 resistance R3 one end connects the I- of charge and discharge current sampling resistance, one end connects the negative phase input of operational amplifier U9; resistance R4 one end connects the I+ of charge and discharge current sampling resistance, one end connects the same phase input of operational amplifier U9; resistance R5 one end connects the negative phase input of operational amplifier U9, one end connects the output of operational amplifier U9; resistance R13 one end connects the same phase input of operational amplifier U9, one end connects GND; wherein resistance R5 = resistance R13, resistance R3 = resistance R4; operational amplifier U9, resistance R5, resistance R3, resistance R4 and resistance R13 constitute differential amplification circuit, for sampling charge and discharge current.

[0088] 4、 resistance R10 one end connects the output of operational amplifier U9, one end connects the same phase input of operational amplifier U10; R9 one end connects the set current value ISET, one end connects the negative phase input of operational amplifier U10; resistance R11 one end connects the negative phase input of operational amplifier U10, one end connects capacitor C3; capacitor C3 one end connects resistance R11, one end connects the output of operational amplifier U10; diode D3 one end connects the output of operational amplifier U10, one end connects the Comp of U1; resistance R9, resistance R10, resistance R11, capacitor C3, operational amplifier U10, diode D3 constitute current loop error amplifier, for responding to the change of charge and discharge current, for power supply chip provides comparison value, thus generating PWM wave.

[0089] 5、The input of the inverter U2 is connected with the PWM of the power chip U1, the output is connected with the input one of the AND gate U3, the output of the AND gate U3 is connected with the input one of the AND gate U4, the output of the AND gate U4 is connected with the HIN of the half-bridge drive chip U7, the input one of the NAND gate U6 is connected with the PWM of the power chip U1, the output of the NAND gate U6 is connected with the input one of the AND gate U5, the output of the AND gate U5 is connected with the LIN of the half-bridge drive chip U7, the MODE is connected with the input two of the AND gate U3 and the NAND gate U6, the EN is connected with the input two of the AND gate U4 and the AND gate U5; the inverter U2, the AND gate U3, the AND gate U4, the AND gate U5 and the NAND gate U6 constitute the BUCK-BOOST switching control circuit, according to the state of the MODE and the EN, the start-stop of the charging and discharging and the switching of the BUCK and the BOOST can be realized, and the algorithm control is not needed.

[0090] 6、The one end of the capacitor C1 is connected with the VS of the half-bridge drive chip U7, and the one end is connected with the VB of the half-bridge drive chip U7; the one end of the diode D1 is connected with the VCC of the half-bridge drive chip U7, and the one end is connected with the VCC of the half-bridge drive chip U7; wherein the diode D1 is a bootstrap diode, and the capacitor C1 is a bootstrap capacitor, and the circuit can realize the driving of the high-side MOS and the low-side MOS.

[0091] The connection mode of the double-tube main power BUCK-BOOST circuit is as follows:

[0092] The positive pole of the capacitor C4 is connected with the input VIN, and the negative pole is connected with the GND; the cathode of the diode D4 is connected with the input VIN, and the anode is connected with the VS; the gate of the field effect tube VT2 is connected with the Ho_driver, the drain is connected with the VIN, and the source is connected with the VS; the cathode of the diode D5 is connected with the VS, and the anode is connected with the GND; the gate of the field effect tube VT3 is connected with the Lo_driver, the drain is connected with the VS, and the source is connected with the GND; the one end of the inductor L1 is connected with the VS, and the one end is connected with the I-; the positive pole of the capacitor C2 is connected with the I-, and the negative pole is connected with the GND; the one end of the R_Isense is connected with the I-, and the one end is connected with the I+; the one end of the relay switch S1 is connected with the I+, and the one end is connected with the positive pole of the battery; the negative pole of the battery is connected with the GND; the circuit receives the driving signal of the PWM control and the BUCK-BOOST switching control circuit, and realizes the charging and discharging of the battery.

[0093] The connection mode of the charging and discharging current sampling switching circuit is as follows:

[0094] The S1 and S3 of the analog switch chip U11 are connected with I-, the S2 and S4 are connected with I+, the D1 and D2 of the analog switch chip U11 are connected with I--, the D3 and D4 are connected with I++, the IN4 and IN1 of the analog switch chip U11 are connected with MODE, one end of the resistor R16 is connected with MODE, one end of the resistor R16 is connected with the base of the triode VT1, one end of the resistor R15 is connected with the collector of the triode VT1, one end of the resistor R15 is connected with the voltage 3.3V, the emitter of the triode VT1 is connected with GND, the IN2 and IN3 of the analog switch chip U11 are connected with the collector of the triode VT1, due to the opposite direction of charging and discharging, the circuit can realize the automatic switching of current sampling according to the MODE signal, and ensures that the output of the current sampling differential amplification circuit is always positive voltage.

[0095] As shown in Figure 6 When the relay switch S1 is opened and the EN signal and the MODE signal are in high level state, the PWM signal is output through the Ho_driver pin of the half-bridge drive chip U7, the Lo_driver pin of the half-bridge drive chip U7 is always in low level state, at this time, the double-tube main power buck-boost circuit is in buck charging mode, and the field effect tube VT2 and the diode D5 start to work to realize battery charging.

[0096] When the relay switch S1 is opened and the EN signal is in high level state and the MODE signal is in low level state, the PWM signal is output through the Lo_driver pin of the half-bridge drive chip U7, the Ho_driver pin of the half-bridge drive chip U7 is always in low level state, at this time, the double-tube main power buck-boost circuit is in boost discharging mode, and the field effect tube VT3 and the diode D4 start to work to realize battery discharging.

[0097] When the relay switch S1 is opened and the EN signal and the MODE signal are in low level state, the Ho_driver pin and the Lo_driver pin of the half-bridge drive chip U7 are in low level state, at this time, the battery stops charging and discharging.

[0098] The present application is not limited to the structure described above and shown in the drawings, and various modifications and changes can be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A bidirectional buck-boost circuit for charging and discharging a battery, characterized by, The application relates to a power supply device, which comprises a buck-boost switching control circuit, a double-tube main power buck-boost circuit and a charge-discharge current sampling switching circuit. The buck-boost switching control circuit is electrically connected with the double-tube main power buck-boost circuit, and the double-tube main power buck-boost circuit is electrically connected with the charge-discharge current sampling switching circuit. The buck-boost switching control circuit comprises a power supply chip U1, an inverter U2, an AND gate U3, an AND gate U4, an AND gate U5, an NAND gate U6, a half-bridge driving chip U7, operational amplifiers U8, U9, U10 and U11, resistors R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13 and R14, and capacitors C1, C2 and C3, diodes D1, D2 and D3. The power supply chip U1 inputs a PWM signal to one end of the inverter U2 and a first pin of the NAND gate U6, a second pin of the NAND gate U6 is connected with a MODE signal, another end of the inverter U2 is connected with a first pin of the AND gate U3, a second pin of the AND gate U3 is connected with the MODE signal, a third pin of the AND gate U3 is connected with a first pin of the AND gate U4, a second pin of the AND gate U4 is connected with a first pin of the AND gate U5 and an EN signal, a second pin of the AND gate U5 is connected with a third pin of the NAND gate U6, a third pin of the AND gate U4 is connected with an HIN pin of the half-bridge driving chip U7, a third pin of the AND gate U5 is connected with a LIN pin of the half-bridge driving chip U7, a VS pin of the half-bridge driving chip U7 is connected with one end of the capacitor C1, another end of the capacitor C1 is connected with a VB pin of the half-bridge driving chip U7 and a negative electrode of the diode D1 respectively, the negative electrode of the diode D1 is connected with a VCC pin of the half-bridge driving chip U7. The operational amplifier U8, the resistor R6, the resistor R1, the resistor R2 and the resistor R14 form a differential amplification circuit, and the differential amplification circuit is used for sampling and amplifying a battery voltage. The resistor R7, the resistor R8, the resistor R12, the capacitor C2, the operational amplifier U11 and the diode D2 form a voltage loop error amplifier, and the voltage loop error amplifier is used for responding to a change of the battery voltage and providing a comparison value for the power supply chip U1 to generate the PWM signal. The charge-discharge current sampling switching circuit comprises an analog switch chip U11, resistors R15 and R16 and a triode VT1. The S1 pin and the S3 pin of the analog switch chip U11 are connected with the I- end, the S2 pin and the S4 pin of the analog switch chip U11 are connected with the I+ end, the D1 pin and the D2 pin of the analog switch chip U11 are connected with the I- end, the D3 pin and the D4 pin of the analog switch chip U11 are connected with the I++ end, the IN4 pin of the analog switch chip U11 is connected with the MODE signal, the IN1 pin of the analog switch chip U11 is connected with the MODE signal and one end of the resistor R16 respectively, the other end of the resistor R16 is connected with the base of the triode VT1, the collector of the triode VT1 is connected with the resistor R15, the IN2 pin of the analog switch chip U11 and the IN3 pin of the analog switch chip U11 respectively, and the emitter of the triode VT1 is grounded.

2. The bidirectional buck-boost circuit for charging and discharging a battery according to claim 1, wherein The Comp pin of the power supply chip U1 is connected with the negative pole of the diode D2 and the negative pole of the diode D3 respectively, the positive pole of the diode D2 is connected with one end of the capacitor C2 and the output end of the operational amplifier U11 respectively, the other end of the capacitor C2 is connected with one end of the resistor R12, the other end of the resistor R12 is connected with the negative phase input end of the operational amplifier U11 and one end of the resistor R7 respectively, the other end of the resistor R7 is set as the voltage value VSET, the same phase input end of the operational amplifier U11 is connected with one end of the resistor R6 and the output end of the operational amplifier U8 through the resistor R8 respectively, the other end of the resistor R6 is connected with the negative phase input end of the operational amplifier U8 and one end of the resistor R1 respectively, the other end of the resistor R1 is connected with the negative pole of the battery, the same phase input end of the operational amplifier U8 is connected with one end of the resistor R2 and one end of the resistor R14 respectively, the other end of the resistor R2 is connected with the positive pole of the battery, the other end of the resistor R14 is grounded, the positive pole of the diode D3 is connected with one end of the capacitor C3 and the output end of the operational amplifier U10 respectively, the other end of the capacitor C3 is connected with one end of the resistor R11, the other end of the resistor R11 is connected with the negative phase input end of the operational amplifier U10 and one end of the resistor R9 respectively, the other end of the resistor R9 is set as the current value ISET, the same phase input end of the operational amplifier U10 is connected with one end of the resistor R10, the other end of the resistor R10 is connected with one end of the resistor R5 and the output end of the operational amplifier U9 respectively, the other end of the resistor R5 is connected with the negative phase input end of the operational amplifier U9 and one end of the resistor R3 respectively, the same phase input end of the operational amplifier U9 is connected with one end of the resistor R4 and one end of the resistor R13 respectively, the other end of the resistor R13 is grounded, and the other end of the resistor R3 and the other end of the resistor R4 are connected with the charge-discharge current sampling feedback voltage respectively.

3. The bidirectional buck-boost circuit for charging and discharging a battery according to claim 2, wherein The double-tube main power step-down and step-up circuit comprises a capacitor C4, a capacitor C5, a field effect tube VT2, a field effect tube VT3, a diode D4, a diode D5, an inductor L1, a resistor R_Isense, a relay switch S1 and a battery VBAT. The positive pole of the capacitor C4 is connected with a VIN end, a negative pole of the diode D4 and a drain of the field effect tube VT2, a gate of the field effect tube VT2 is connected with a Ho_driver end, a source of the field effect tube VT2 is connected with a positive pole of the diode D4, a VS end, one end of the inductor L1, a drain of the field effect tube VT3 and a negative pole of the diode D5, the other end of the inductor L1 is connected with an I- end, one end of the resistor R_Isense and a positive pole of the capacitor C5, the other end of the resistor R_Isense is connected with an I+ end and one end of the relay switch S1, the other end of the relay switch S1 is connected with a positive pole of the battery VBAT, a negative pole of the battery VBAT is connected with a negative pole of the capacitor C5, a positive pole of the diode D5, a source of the field effect tube VT3 and a negative pole of the capacitor C4 and grounded, and a gate of the field effect tube VT3 is connected with a Lo_driver end.

4. The bidirectional buck-boost circuit for charging and discharging a battery according to claim 3, wherein The capacitor C4 is an input capacitor, the capacitor C5 is an output capacitor, and the resistor R_Isense is a charge and discharge current sampling resistor.

5. The bidirectional buck-boost circuit for charging and discharging a battery according to claim 4, wherein The charge and discharge current sampling switching circuit automatically switches the current sampling according to a MODE signal and ensures that the output of the differential amplification circuit is a positive voltage.

6. The bidirectional buck-boost circuit for charging and discharging a battery according to claim 5, wherein The input of the analog switch chip U11 is IN1 pin, IN2 pin, IN3 pin and IN4 pin, and the IN1 pin controls the switches of S1 pin and D1 pin, the IN2 pin controls the switches of S2 pin and D2 pin, the IN3 pin controls the switches of S3 pin and D3 pin, and the IN4 pin controls the switches of S4 pin and D4 pin.

7. A control method of a bidirectional step-down / step-up circuit for charging / discharging a battery, which controls the bidirectional step-down / step-up circuit for charging / discharging a battery described in claim 6, characterized by The control method comprises: When the relay switch S1 is opened and the EN signal and the MODE signal are both in a high level state, a PWM signal is output through a Ho_driver pin of the half-bridge drive chip U7, a Lo_driver pin of the half-bridge drive chip U7 is always in a low level state, at this time, the double-tube main power step-down and step-up circuit is in a step-down charging mode, and the field effect tube VT2 and the diode D5 start to work to realize battery charging; When the relay switch S1 is opened and the EN signal is in a high level state and the MODE signal is in a low level state, a PWM signal is output through a Lo_driver pin of the half-bridge drive chip U7, a Ho_driver pin of the half-bridge drive chip U7 is always in a low level state, at this time, the double-tube main power step-down and step-up circuit is in a step-up discharging mode, and the field effect tube VT3 and the diode D4 start to work to realize battery discharging; When the relay switch S1 is opened and the EN signal is in a high level state and the MODE signal is in a low level state, a PWM signal is output through a Lo_driver pin of the half-bridge drive chip U7, a Ho_driver pin of the half-bridge drive chip U7 is always in a low level state, at this time, the double-tube main power step-down and step-up circuit is in a step-up discharging mode, and the field effect tube VT3 and the diode D4 start to work to realize battery discharging; When the relay switch S1 is disconnected, and the EN signal and the MODE signal are in low level state, the Ho_driver pin and the Lo_driver pin of the half-bridge drive chip U7 are in low level state, at this time the battery stops charging and discharging.

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