Buck-boost circuit applied to sodium ion battery

Abstract

The invention discloses a buck-boost circuit applied to a sodium ion battery, which comprises a protection circuit, a power conversion and direct connection circuit and a discharge control circuit, and is characterized in that the protection circuit is used for providing a secondary protection function for the sodium ion battery; the power conversion and straight-through circuit is used for providing functions of boost discharge, buck charge, buck feed, straight-through mode charge and discharge and the like for the sodium ion battery, and the discharge control circuit is used for controlling the sodium ion battery to discharge external equipment. When the voltage of the battery meets the lowest working voltage of the load, the voltage of the battery is directly output to supply power to the load through the power conversion and the direct connection function of the direct connection circuit; when the voltage of the battery is lower than the lowest working voltage of the load, the battery is boosted to supply power to the load through the boosting function of the power conversion and through circuit. According to the invention, the low-voltage energy of the sodium-ion battery can be released, the energy utilization efficiency of the sodium-ion battery is improved, the circuit design is simple, the cost is relatively low, and the market competitiveness is very strong.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion battery power supply, and in particular relates to a step-up and step-down circuit applied to a sodium ion battery. Background Art

[0002] Compared with lithium batteries, sodium-ion batteries have the advantages of low-temperature operation and higher safety, and the reserves of sodium are very abundant, and the cost is lower than that of lithium batteries. Therefore, as the technology of sodium-ion batteries matures, the application areas of sodium-ion batteries will become more extensive.

[0003] The core problem faced by sodium-ion batteries in practical applications is the low energy utilization rate caused by the wide voltage range, which is specifically manifested in the following two aspects: 1. Energy waste in the low-voltage area: When the battery voltage drops below 2.5V, although there is still 20% to 30% of remaining capacity, the voltage is close to the system-set cutoff voltage (usually 2.0 to 2.5V). To prevent over-discharge, the battery management system (BMS) will forcibly terminate discharge, resulting in the ineffective use of this part of energy.

[0004] 2. System Design Challenges: The wide voltage range (3.8-4.2V at full charge to 2.0-2.5V at cutoff) places higher demands on the design of power electronics. DC-DC converters must maintain high efficiency across a wide input voltage range, increasing system complexity and cost. In energy storage systems, voltage inconsistencies between individual cells are amplified, further reducing the system's available capacity.

[0005] Through research and retrieval, we can find some existing technical solutions such as the Chinese patent applications with publication numbers CN119298282A and CN119401618A, but these patent technologies each have corresponding defects and deficiencies. Comprehensive analysis shows that the voltage behavior of sodium-ion batteries is derived from the intrinsic characteristics of their electrode materials; unlike lithium-ion batteries, sodium-ion batteries lack a stable voltage platform during the discharge process, and their discharge curves show a continuous downward trend. Their operating voltage range is 1.5V to 3.9V, and the corresponding energy is 0%~100%; while the operating voltage range of lithium batteries is 2.5V~3.9V, and the corresponding energy SOC (State Of Charge) is 0%~100%, such as Figure 9 Obviously, at the same operating voltage Vp of the external system equipment, 15% to 20% of the energy of the sodium battery will not be released and utilized, resulting in the sodium battery's energy in the low-voltage range being unusable. This will sacrifice the energy of the sodium-ion battery and lead to a decline in the competitiveness of the sodium-ion battery. Summary of the Invention

[0006] In view of the above, the present invention provides a step-up / step-down circuit for sodium ion batteries, which can release the low-voltage energy of the sodium ion battery and improve the energy utilization efficiency of the sodium ion battery.

[0007] A step-up / down circuit for a sodium-ion battery comprises a protection circuit, a power conversion and pass-through circuit, and a discharge control circuit. The sodium-ion battery is connected to the power conversion and pass-through circuit via the protection circuit, and the discharge control circuit is connected to the sodium-ion battery or an external device. The protection circuit is used to provide secondary protection for the sodium-ion battery. The power conversion and pass-through circuit is used to provide the sodium-ion battery with boost discharge, step-down charging, step-down feeding, and pass-through mode charging and discharging functions. The discharge control circuit is used to control the sodium-ion battery to discharge an external device. The power conversion and pass-through circuit has two operating modes: discharge and charge, and automatically switches to the corresponding operating mode based on a comparison result between the sodium-ion battery voltage and the external device voltage.

[0008] Furthermore, one end of the protection circuit is connected to the positive terminal of the sodium-ion battery, and the other end is connected to the positive input terminal of the power conversion and direct-through circuit, which is used to physically protect the sodium-ion battery after other protections fail. According to design requirements, the protection circuit uses an ordinary fuse, a three-terminal fuse or other circuit-breaking device to ensure that the connection between the power conversion and direct-through circuit and the sodium-ion battery is disconnected when other protections fail. Therefore, it is also called secondary protection, which can improve the safety of the battery.

[0009] Furthermore, in the discharge mode, when the sodium-ion battery voltage meets the minimum operating voltage of the external device, the power conversion and pass-through circuit is directly connected, and the sodium-ion battery voltage is directly output to power the external device; when the sodium-ion battery voltage is lower than the minimum operating voltage of the external device, the power conversion and pass-through circuit starts the boost function, boosts the sodium-ion battery and reaches the normal operating voltage of the external device to power the external device, thereby realizing dynamic adaptation to the operating voltage range of the external device.

[0010] Furthermore, in the charging mode, when the sodium-ion battery voltage is within the output voltage range of the external device, the power conversion and pass-through circuit is directly connected, and the sodium-ion battery is directly charged using the output voltage of the external device; when the sodium-ion battery voltage is lower than the minimum output voltage of the external device, the power conversion and pass-through circuit starts the step-down function, and charges the sodium-ion battery after stepping down the output voltage of the external device.

[0011] Furthermore, when the external device needs power supply, the discharge control circuit is closed; when the external device does not need power supply or a circuit fault occurs, the discharge control circuit is disconnected.

[0012] Furthermore, the discharge control circuit is implemented by a power switch device with controllable on / off, such as a power MOS (metal oxide semiconductor) and an IGBT (insulated gate bipolar transistor).

[0013] Furthermore, the discharge control circuit has three connection methods: the first is that one end of the discharge control circuit is connected to the positive output end of the power conversion and direct-through circuit, and the other end is connected to the positive end of the external device; the second is that one end of the discharge control circuit is connected to the negative end of the power conversion and direct-through circuit, and the other end is connected to the negative end of the external device; the third is that one end of the discharge control circuit is connected to the negative end of the sodium-ion battery, and the other end is connected to the negative end of the power conversion and direct-through circuit.

[0014] Furthermore, the power conversion and pass-through circuit consists of two parts: a pass-through circuit module and a buck-boost circuit module. When the voltage of the sodium ion battery meets the voltage requirement of the external device, the pass-through circuit module is started, and direct charging and discharging between the external device and the sodium ion battery is achieved through this module; when the voltage of the sodium ion battery is lower than the voltage requirement of the external device, the buck-boost circuit module is started, and the sodium ion battery is boosted and discharged through this module, or the voltage of the external device is stepped down through this module to charge the sodium ion battery.

[0015] Furthermore, the direct-through circuit module is implemented using a switch tube S3. The buck-boost circuit module includes two capacitors C1 and C2, two switch tubes S1 and S2, and an inductor L1. One end of S3 is connected to one end of L1 and one end of C1 as the positive input end of the power conversion and direct-through circuit, the other end of L1 is connected to one end of S1 and one end of S2, the other end of S1 is connected to the other end of S3 and one end of C2 as the positive output end of the power conversion and direct-through circuit, the other end of C1 is connected to the other end of S2 and the other end of C2 as the negative end of the power conversion and direct-through circuit, and the control electrodes of the switch tubes S1 to S3 are connected to the switching signals provided by the external controller.

[0016] Based on the above technical solution, the present invention has the following beneficial technical effects: 1. When the sodium-ion battery voltage meets the voltage requirements of the external device, the pass-through circuit in the power conversion and pass-through circuit works, so that the battery voltage is directly output, improving the working efficiency in this range.

[0017] 2. When the sodium-ion battery voltage is lower than the voltage requirement of the external device, the buck-boost circuit in the power conversion and pass-through circuit operates to boost the sodium-ion battery output voltage to meet the voltage requirement of the external device. Through the boost of this boost circuit, all the energy of the sodium battery can be released for use by the external device, thereby improving the efficiency of the sodium battery.

[0018] 3. The present invention uses a direct circuit or a buck-boost circuit to realize a power feeding function when the electric vehicle brakes or goes downhill, thereby recovering kinetic energy and improving efficiency.

[0019] 4. The present invention adds a secondary protection circuit between the battery terminal and the power conversion and pass-through circuit, which can further improve the reliability of the battery under complex operating conditions. If the power conversion and pass-through circuits experience an abnormality, they can be disconnected by this protection circuit to protect the battery from damage.

[0020] 5. The present invention adds a discharge control circuit between the power conversion and pass-through circuit and the external device, which can quickly and effectively isolate the battery from the external power-consuming device when encountering a failure of the external device.

[0021] Therefore, the present invention addresses the problem of sodium-ion batteries requiring a boost to meet external system requirements when operating at low voltage, targeting applications requiring sodium-ion batteries for power supply, backup power, or energy storage. Furthermore, the present invention offers a simple circuit design, comprehensive functionality, high reliability, and low cost, making it highly competitive in the market. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The figure is a schematic diagram of the buck-boost circuit system architecture of the present invention applied to sodium ion batteries.

[0023] Figure 2 Schematic diagram of the buck-boost circuit structure applied to a sodium ion battery in Example 1 of the present invention (the discharge control circuit is placed at the positive end of the load).

[0024] Figure 3 Schematic diagram of the connection of the buck-boost circuit in the discharge through working mode in Example 1 of the present invention.

[0025] Figure 4 Schematic diagram of the connection of the buck-boost circuit in the boost discharge working mode in Example 1 of the present invention.

[0026] Figure 5 Schematic diagram of the connection of the buck-boost circuit in the charging pass-through mode in Example 1 of the present invention.

[0027] Figure 6 Schematic diagram of the connection of the buck-boost circuit in buck charging or feeding mode in embodiment 1 of the present invention.

[0028] Figure 7 Schematic diagram of the buck-boost circuit structure applied to a sodium ion battery in Example 2 of the present invention (the discharge control circuit is placed at the negative end of the load).

[0029] Figure 8 Schematic diagram of the buck-boost circuit structure applied to a sodium ion battery in Example 3 of the present invention (the discharge control circuit is placed at the negative terminal of the battery).

[0030] Figure 9 Schematic diagram of the change of lithium battery voltage and sodium battery voltage with SOC. In the figure, V1 and V2 are the operating voltages of lithium batteries when SOC=0 and SOC=100%.

[0031] Figure 10 Schematic diagram of the discharge control strategy of the sodium ion battery in the present invention.

[0032] Figure 11 Schematic diagram of the charging / feeding control strategy of the sodium ion battery in the present invention. DETAILED DESCRIPTION

[0033] In order to describe the present invention more specifically, the technical solution of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] like Figure 1 As shown, the buck-boost circuit applied to a sodium-ion battery of the present invention includes: a protection circuit, a power conversion and pass-through circuit, and a discharge control circuit, wherein: the protection circuit is connected to the sodium battery and the power conversion and pass-through circuit, and has a secondary protection function for the sodium battery; the power conversion and pass-through circuit is connected between the secondary protection and the sodium battery discharge control circuit, and has functions such as boost discharge, buck charging, buck feeding, and pass-through mode charging and discharging; the discharge control circuit is connected between the power conversion and pass-through circuit and the load port, and has a function of controlling external discharge.

[0035] One end of the protection circuit is connected to the sodium battery, and the other end is connected to the power conversion and pass-through circuit. Generally, a fuse, a three-terminal fuse or other device that can disconnect the battery connection in the event of a short circuit is used to ensure that the connection with the battery is disconnected when other protections fail. Therefore, it is also called a secondary protection circuit, which can improve the safety of the battery.

[0036] The power conversion and pass-through circuit primarily consists of two functional circuit modules: a pass-through circuit module and a buck-boost circuit module. When the sodium-ion battery voltage meets the requirements of the external device, the pass-through circuit module activates and directly outputs the battery voltage, enabling direct charging and discharging between the external load and the sodium-ion battery. The pass-through circuit module generally utilizes switchable power devices, such as power MOS and IGBTs. When the sodium-ion battery voltage falls below the external load's required voltage, the buck-boost circuit module activates, boosting the internal sodium-ion battery voltage for discharge and stepping down the voltage at the external load port to charge the battery. The buck-boost circuit module consists of an inductor, two switching transistors, and two capacitors, the two capacitors providing high-frequency operation for the buck-boost circuit.

[0037] like Figure 10As shown in the figure, in the discharge mode, when the sodium-ion battery voltage Vb satisfies V1≤Vb≤V2, the power conversion and pass-through circuit starts the pass-through discharge function and directly outputs the sodium-ion battery voltage to power the external device; when the sodium-ion battery voltage Vb≤V1, the power conversion and pass-through circuit starts the boost discharge function, boosts the sodium-ion battery voltage and reaches the normal operating voltage of the external device to power the external device, thereby realizing dynamic adaptation to the operating voltage range of the external device; V1 and V2 are the lower limit and upper limit of the operating voltage of the external device, respectively.

[0038] like Figure 11 As shown in the charging mode, when the sodium ion battery voltage Vb satisfies V1≤Vb≤V2, the power conversion and pass-through circuit starts the pass-through charging / feeding function, and uses the output voltage of the external device to directly charge / feed the sodium ion battery; when the sodium ion battery voltage Vb≤V1, the power conversion and pass-through circuit starts the step-down charging / feeding function, and charges the sodium ion battery after stepping down the output voltage of the external device.

[0039] One end of the discharge control circuit is connected to the power conversion and pass-through circuit, and the other end is connected to the positive terminal of the external load. It generally uses controllable power devices such as power MOS and IGBT. When the external load requires power, the discharge control circuit is closed, and the output port can obtain the sodium-ion battery voltage. When the external load does not need power or a circuit fault occurs, the discharge control circuit is disconnected, and the port voltage disappears.

[0040] Example 1 like Figure 2 As shown, in this embodiment, the positive terminal of the sodium-ion battery is connected to one end of a secondary protection fuse F1, the other end of fuse F1 is connected to the input of the power conversion and direct-through circuit, the output of the power conversion and direct-through circuit is connected to one end of a discharge control circuit S4, and the other end of S4 is connected to the positive terminal of an external load. The internal connections of the power conversion and direct-through circuit are as follows: an inductor L1 is connected in series with a switch S1, then connected in parallel with a switch S3, and connected across the input and output of the power conversion and direct-through circuit; one end of a capacitor C1 is connected to the input of the power conversion and direct-through circuit, and the other end of capacitor C1 is connected to the negative terminal of the battery; one end of a capacitor C2 is connected to the output of the power conversion and direct-through circuit, and the other end of capacitor C2 is connected to the negative terminal of the battery; one end of a switch S2 is connected to the common terminal of the inductor L1 and the switch S1, and the other end of the switch S2 is connected to the negative terminal of the battery, which is directly connected to the negative terminal of the external load.

[0041] like Figure 3 As shown, the system is in discharge direct working mode, at this time S1 and S2 are turned off, S3 is turned on, and the sodium ion battery voltage Vb is directly discharged outward through S3. Figure 4As shown, the system is in the boost discharge mode, at this time S1 and S2 are turned on alternately, S3 is turned off, and the sodium ion battery voltage Vb is discharged after being boosted. Figure 5 As shown, the system is in the charging direct working mode, at this time S1 and S2 are turned off, S3 is turned on, and the external voltage Vp directly charges or feeds the sodium ion battery through S3. Figure 6 As shown, the system is in the step-down charging or feeding working mode. At this time, S1 and S2 are alternately turned on, S3 is turned off, and the external voltage Vp is stepped down to charge or feed the sodium ion battery.

[0042] Example 2 like Figure 7 As shown, in this embodiment, the voltage of the sodium ion battery is recorded as Vb, and its positive terminal is connected to one end of the secondary protection fuse F1. The other end of F1 is connected to the input end of the power conversion and direct-through circuit, that is, connected to one end of the switch tube S3, one end of the inductor L1, and one end of the capacitor C1 respectively. The other end of the inductor L1 is connected to one end of the switch tube S1, and the other end of the switch tube S1 is respectively connected to one end of the capacitor C2 and the positive end of the external load; the switch tube S3 is connected between the input and output ends of the power conversion and direct-through circuit; the other end of the capacitor C1 is connected to the negative end of the battery, and the other end of the capacitor C2 is connected to the negative end of the battery. One end of the switch tube S2 is connected to the common connection point of L1 and S1, and the other end is connected to the negative end of the battery; one end of the discharge control circuit S4 is connected to the negative end of the external load, and the other end is connected to the other end of C1, the other end of C2, and the other end of S2.

[0043] Example 3 like Figure 8 As shown, in this embodiment, the voltage of the sodium ion battery is Vb, the positive terminal of the sodium ion battery is connected to one end of the secondary protection fuse F1, and the other end of F1 is connected to the input end of the power conversion and direct-through circuit, that is, connected to one end of the switch tube S3, one end of the inductor L1, and one end of the capacitor C1, respectively. The other end of the inductor L1 is connected to one end of the switch tube S1, and the other end of the switch tube S1 is connected to one end of the capacitor C2 and the positive end of the external load; the switch tube S3 is connected between the input and output ends of the power conversion and direct-through circuit; the other ends of the capacitors C1 and C2 are both connected to the negative terminal of the battery; one end of the switch tube S2 is connected to the common connection point of L1 and S1, and the other end is connected to the negative terminal of the battery; one end of the discharge control circuit S4 is connected to the negative terminal of the battery, and the other end is connected to the other end of C1, the other end of C2, and the other end of S2.

[0044] The above description of the embodiments is intended to facilitate understanding and application of the present invention by those skilled in the art. It is apparent that those skilled in the art can readily make various modifications to the above embodiments and apply the general principles described herein to other embodiments without requiring creative effort. Therefore, the present invention is not limited to the above embodiments. Any improvements or modifications made by those skilled in the art based on the disclosure of the present invention should fall within the scope of protection of the present invention.

Claims

1. A step-up / step-down circuit for sodium ion batteries, characterized in that: The invention comprises a protection circuit, a power conversion and pass-through circuit, and a discharge control circuit, wherein a sodium ion battery is connected to the power conversion and pass-through circuit via the protection circuit, and the discharge control circuit is connected to the sodium ion battery or an external device; the protection circuit is used to provide a secondary protection function for the sodium ion battery, the power conversion and pass-through circuit is used to provide the sodium ion battery with the functions of boost discharge, buck charging, buck feeding, and pass-through mode charging and discharging; the discharge control circuit is used to control the sodium ion battery to discharge the external device; the power conversion and pass-through circuit has two working modes, discharge and charge, and automatically switches to the corresponding working mode according to the comparison result between the sodium ion battery voltage and the external device voltage.

2. The step-up / down circuit for sodium ion batteries according to claim 1, wherein: One end of the protection circuit is connected to the positive terminal of the sodium-ion battery, and the other end is connected to the positive input terminal of the power conversion and direct-through circuit, which is used to physically protect the sodium-ion battery after the protection fails. According to design requirements, the protection circuit uses circuit-breaking devices including ordinary fuses and three-terminal fuses to ensure that the connection between the power conversion and direct-through circuit and the sodium-ion battery is disconnected under the premise of protection failure.

3. The step-up / down circuit for sodium ion batteries according to claim 1, wherein: In discharge mode, when the sodium-ion battery voltage meets the minimum operating voltage of the external device, the power conversion and pass-through circuit is directly connected, and the sodium-ion battery voltage is directly output to power the external device; when the sodium-ion battery voltage is lower than the minimum operating voltage of the external device, the power conversion and pass-through circuit starts the boost function, boosts the sodium-ion battery and reaches the normal operating voltage of the external device to power the external device, thereby realizing dynamic adaptation to the operating voltage range of the external device.

4. The step-up / down circuit for sodium ion batteries according to claim 1, wherein: In charging mode, when the sodium-ion battery voltage is within the output voltage range of the external device, the power conversion and pass-through circuit is directly connected, and the sodium-ion battery is directly charged using the output voltage of the external device; when the sodium-ion battery voltage is lower than the minimum output voltage of the external device, the power conversion and pass-through circuit starts the step-down function, and charges the sodium-ion battery after stepping down the output voltage of the external device.

5. The step-up / down circuit for sodium ion batteries according to claim 1, wherein: When the external device needs power supply, the discharge control circuit is closed; when the external device does not need power supply or a circuit fault occurs, the discharge control circuit is disconnected.

6. The step-up / down circuit for sodium ion batteries according to claim 5, characterized in that: The discharge control circuit is implemented by a power switch device with controllable on and off.

7. The step-up / down circuit for sodium ion batteries according to claim 5, characterized in that: The discharge control circuit has three connection modes: the first is that one end of the discharge control circuit is connected to the positive output end of the power conversion and direct-through circuit, and the other end is connected to the positive end of the external device; the second is that one end of the discharge control circuit is connected to the negative end of the power conversion and direct-through circuit, and the other end is connected to the negative end of the external device; the third is that one end of the discharge control circuit is connected to the negative end of the sodium ion battery, and the other end is connected to the negative end of the power conversion and direct-through circuit.

8. The step-up / down circuit for sodium ion batteries according to claim 1, wherein: The power conversion and pass-through circuit consists of two parts: a pass-through circuit module and a buck-boost circuit module. When the voltage of the sodium ion battery meets the voltage requirement of the external device, the pass-through circuit module is activated to achieve direct charging and discharging between the external device and the sodium ion battery. When the voltage of the sodium ion battery is lower than the voltage requirement of the external device, the buck-boost circuit module is activated to achieve boost discharge of the sodium ion battery or charge the sodium ion battery after the voltage of the external device is stepped down by the module.

9. The step-up / down circuit for sodium ion batteries according to claim 8, characterized in that: The direct-through circuit module is implemented using a switch tube S3. The buck-boost circuit module includes two capacitors C1 and C2, two switch tubes S1 and S2, and an inductor L1. One end of S3 is connected to one end of L1 and one end of C1 as the positive input end of the power conversion and direct-through circuit. The other end of L1 is connected to one end of S1 and one end of S2. The other end of S1 is connected to the other end of S3 and one end of C2 as the positive output end of the power conversion and direct-through circuit. The other end of C1 is connected to the other end of S2 and the other end of C2 as the negative end of the power conversion and direct-through circuit. The control electrodes of the switch tubes S1 to S3 are connected to the switching signals provided by an external controller.

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