Starting circuit of switching power supply, switching power supply and battery system

Abstract

The invention discloses a starting circuit of a switching power supply, the switching power supply and a battery system, and relates to the field of circuits, a battery charges a first capacitor through a first current limiting module, and if the switching power supply needs to be started subsequently and then a starting switch is controlled to be switched on, the first capacitor charges a second capacitor through the switched-on starting switch at the moment; therefore, the starting time of the switching power supply corresponds to the time required by the process of charging the second capacitor until the voltage of the first end of the second capacitor reaches the starting voltage of the driving chip, and the starting time depends on the capacitance value of the first capacitor and the capacitance value of the second capacitor, so that the starting time of the switching power supply in different application scenes can be basically consistent. Meanwhile, the voltage endurance capability and the current-carrying capability of the starting switch also depend on the energy storage voltage after the first capacitor is fully charged, and compared with the battery voltage, the energy storage voltage of the first capacitor is smaller, so that the size of the starting switch is effectively reduced, and the implementation cost of the starting switch is reduced.

Description

Technical Field

[0001] This invention relates to the field of circuits, and in particular to a startup circuit for a switching power supply, a switching power supply, and a battery system. Background Technology

[0002] Switching power supplies are widely used in industrial control, new energy, and power electronic converter industries due to their advantages such as small size, light weight, high conversion efficiency, and stable and reliable performance. They are particularly useful for powering battery management systems (BMS). In existing technologies, when a switching power supply is used to power a battery's BMS, its input terminal is connected to the battery via a start switch, and its output terminal is connected to the power supply terminal of the battery's BMS. The start-up of the switching power supply is controlled by turning the start switch on or off. However, since batteries are often constructed using multiple cells connected in series, the number of cells in series varies depending on the application scenario. Therefore, the voltage input to the switching power supply differs between different batteries, resulting in significant differences in the startup time of the switching power supply for different batteries. When the number of cells in series is small, the input voltage of the switching power supply is low, and the startup time is long after power-on. When the number of cells in series is large, the input voltage of the switching power supply is high, and the startup time is short after power-on. Furthermore, when there are a large number of cells connected in series, especially in the application scenario of high-voltage batteries, the voltage range from the battery input to the switching power supply is wide. The starting switch needs to be selected with a switching device that has sufficient voltage resistance and current carrying capacity, which will lead to an increase in the size of the starting switch and increase the implementation cost of the starting switch. Summary of the Invention

[0003] The purpose of this invention is to provide a startup circuit, a switching power supply, and a battery system for a switching power supply, aiming to solve the technical problem of differences in startup time of switching power supplies under different application scenarios.

[0004] To solve the above-mentioned technical problems, the present invention provides a startup circuit for a switching power supply, comprising: The first current limiting module has its first terminal connected to the output terminal of the battery. The first capacitor, with its first terminal connected to the first power supply ground, is used to charge the battery based on the electrical energy output when the battery outputs electrical energy. A power switch is configured such that its first terminal is connected to the second terminal of the first current limiting module and the second terminal of the first capacitor, respectively, and is used to turn on when the switching power supply needs to be started and turn off when the switching power supply has completed the startup process. The second capacitor has its first end connected to the second end of the start switch and the power supply terminal of the driver chip in the switching power supply, and its second end connected to the first power ground. It is used to charge the first capacitor based on the electrical energy stored in it when the start switch is turned on, so that the switching power supply can be started when the voltage at the first end of the second capacitor reaches the start voltage of the driver chip.

[0005] Optionally, the startup circuit of the switching power supply may also include: The first voltage regulator is connected in parallel across the first capacitor to provide overvoltage protection for the first capacitor. And / or, The second voltage regulator is connected in parallel across the second capacitor to provide overvoltage protection for the second capacitor.

[0006] Optionally, the first voltage regulator is a first Zener diode, with the positive terminal of the first Zener diode connected to the first power supply ground and the negative terminal connected to the second terminal of the first capacitor. The second voltage regulator is a second Zener diode, with its anode connected to the first power supply ground and its cathode connected to the first terminal of the second capacitor.

[0007] Optionally, the startup circuit of the switching power supply may also include: The second current limiting module has its first end connected to the second end of the start switch, and its second end connected to the first end of the second capacitor and the power supply terminal of the driver chip in the switching power supply.

[0008] Optionally, the startup circuit of the switching power supply may also include: The discharge circuit has its input terminal connected to the first terminal of the second capacitor. It is used to discharge the second capacitor when the battery is undervoltage, so as to control the switching power supply to stop working.

[0009] Optionally, the discharge circuit includes: The first terminal of the discharge resistor is connected to the first terminal of the second capacitor. The discharge switch has its first end connected to the second end of the discharge resistor and its second end connected to the first power supply ground. It is used to turn on when the battery is undervoltage to discharge the second capacitor, and to turn off when the battery is not undervoltage.

[0010] Optionally, the discharge switch is an optocoupler, the collector of the optocoupler is connected to the second end of the discharge resistor, and the emitter is connected to the first power supply ground; The discharge circuit further includes: The third current limiting module has its first end connected to the output terminal of the switching power supply and its second end connected to the anode of the optocoupler. A controllable switch has a first end connected to the cathode of the optocoupler, a second end connected to the second power ground, and a control end connected to the output end of the battery management system of the battery. It is used to turn on when a discharge signal output by the battery management system is received, and turn off when no discharge signal output by the battery management system is received. The discharge signal is generated when the battery management system detects that the battery is undervoltage.

[0011] To solve the above-mentioned technical problems, the present invention also provides a switching power supply, including a transformer, a power transistor, a driver chip, and a startup circuit of the switching power supply as described above. The first end of the primary winding of the transformer is connected to the output end of the battery, the second end of the primary winding is connected to the first end of the power transistor, the control end of the power transistor is connected to the signal output end of the driver chip, and the power supply end of the driver chip is connected to the output end of the startup circuit of the switching power supply and the auxiliary winding of the transformer, respectively. The startup circuit of the switching power supply is used to supply power to the driver chip to start the switching power supply when it is required to start the switching power supply; The auxiliary winding of the transformer is used to supply power to the driver chip after the switching power supply has finished starting.

[0012] Optionally, the switching power supply further includes: The rectifier diode, with its positive terminal connected to the first end of the auxiliary winding of the transformer, is used to convert the alternating current output from the auxiliary winding of the transformer into direct current, so as to supply power to the driver chip after the switching power supply has completed startup. The second end of the auxiliary winding of the transformer is connected to the ground of the first power supply; The current-limiting resistor has its first end connected to the negative terminal of the rectifier diode and its second end connected to the power supply terminal of the driver chip.

[0013] To address the aforementioned technical problems, the present invention also provides a battery system, comprising a battery, a battery management system, and a switching power supply as described above. The positive output terminal of the battery is connected to a first end of the primary winding of the transformer in the switching power supply and an input terminal of the startup circuit of the switching power supply. The negative output terminal of the battery serves as a first power ground. The input terminal of the battery management system is connected to the output terminal of the switching power supply, and the output terminal of the battery management system is connected to the control terminal of the startup circuit of the switching power supply.

[0014] This invention provides a startup circuit for a switching power supply, including a first current limiting module, a first capacitor, a startup switch, and a second capacitor. A battery serves as the input power source for the switching power supply. When the battery outputs electrical energy, it charges the first capacitor through the first current limiting module. After the first capacitor is fully charged, if the switching power supply needs to be started, the startup switch is turned on. At this time, the first capacitor charges the second capacitor through the turned-on startup switch. Therefore, the startup time of the switching power supply corresponds to the time required for the voltage at the first terminal of the second capacitor to reach the startup voltage of the driver chip. This startup time is independent of the voltage input from the battery to the switching power supply, but depends on the capacitance values ​​of the first and second capacitors, thus achieving a consistent startup time for the switching power supply across different application scenarios. Simultaneously, the voltage withstand capability and current carrying capacity of the startup switch also depend on the energy storage voltage of the first capacitor after it is fully charged. Compared to the battery voltage, the energy storage voltage of the first capacitor is smaller, effectively reducing the size of the startup switch and lowering its implementation cost.

[0015] The present invention also provides a switching power supply and battery system, which have the same beneficial effects as the startup circuit of the aforementioned switching power supply. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the prior art and embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A schematic diagram of the startup circuit of a switching power supply provided by the present invention; Figure 2 A schematic diagram of a switching power supply provided by the present invention; Figure 3 This is a schematic diagram of a discharge circuit provided by the present invention. Detailed Implementation

[0018] The core of this invention is to provide a startup circuit for a switching power supply, a switching power supply, and a battery system. The startup time of the switching power supply depends on the capacitance values ​​of the first capacitor and the second capacitor, thereby achieving a basically consistent startup time for the switching power supply under different application scenarios. Simultaneously, the voltage withstand capability and current carrying capacity of the startup switch also depend on the energy storage voltage of the first capacitor after it is fully charged. Compared to the battery voltage, this effectively reduces the size of the startup switch and lowers its implementation cost.

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] See Figure 1 As shown, Figure 1 This invention provides a schematic diagram of the startup circuit for a switching power supply. To solve the above-mentioned technical problems, this invention provides a startup circuit 1 for a switching power supply, comprising: The first current limiting module R1 has its first terminal connected to the output terminal of the battery. The first capacitor C1 has its first terminal connected to the first power supply ground, and is used to charge the battery based on the output power when the battery outputs power. The first terminal of the start switch S0 is connected to the second terminal of the first current limiting module R1 and the second terminal of the first capacitor C1, respectively, and is used to turn on when the power supply of the start switch S0 needs to be turned on, and to turn off when the power supply has completed the start-up process. The second capacitor C2 has its first end connected to the second end of the start switch S0 and the power supply terminal of the driver chip U0 in the switching power supply, respectively. Its second end is connected to the first power ground. When the start switch S0 is turned on, it is charged based on the electrical energy stored in the first capacitor C1, so that the power supply of the switch S0 is turned on when the voltage at the first end of the second capacitor C2 reaches the start voltage of the driver chip U0.

[0021] It is easy to understand that, in order to address the inconsistency in startup time of the switching power supply under different application scenarios, especially when the battery voltage level connected to the input terminal of the switching power supply is different, this application provides a new startup circuit 1 for the switching power supply to achieve startup. The first terminal of the first current limiting module R1 is directly connected to the output terminal of the battery, and the second terminal of the first capacitor C1 is connected to the output terminal of the battery through the first current limiting module R1. As long as the battery has power output, it will automatically charge the first capacitor C1 through the first current limiting module R1, and the first capacitor C1 will charge quickly. If it is necessary to start the power supply of the start switch S0, the start switch S0 is turned on. At this time, the voltage across the first capacitor C1 will charge the second capacitor C2 through the turned-on start switch S0. The second capacitor C2 continues to charge. When the voltage at the first terminal of the second capacitor C2 reaches the startup voltage of the driver chip U0, the driver chip U0 can start and begin to work. The startup circuit 1 provides initial operating power to the driver chip U0, enabling the driver chip U0 to start working. After the driver chip U0 starts working and completes its own initialization, it will output the corresponding drive signal to turn on the power transistor Q0 in the switching power supply, thereby completing the startup of the switching power supply.

[0022] It is understandable that the first capacitor C1 is directly connected to the battery through the first current limiting module R1. Before the start switch S0 is turned on, the battery has already charged the first capacitor C1 through the first current limiting module R1, and the first capacitor C1 will quickly charge to a fully charged state. Then, by operating the start switch S0 to turn on, the first capacitor C1 charges the second capacitor C2 through the turned-on start switch S0. By charging the second capacitor C2, the voltage at the first terminal of the second capacitor C2, that is, the voltage at the power supply terminal of the driver chip U0, reaches the start-up voltage of the driver chip U0. Therefore, the startup time of the switching power supply depends on the time required for the first capacitor C1 to charge the second capacitor C2 to the startup voltage of the driver chip U0. This time is only related to the final voltage of the first capacitor C1 when fully charged and the startup voltage of the second capacitor C2. The final voltage of the first capacitor C1 when fully charged depends on the capacitance value of the first capacitor C1. The startup voltage is a fixed value, and the capacitance value of the second capacitor C2 is usually designed based on the final voltage of the second capacitor C2 being equal to or slightly greater than the startup voltage to ensure that the driver chip U0 can start based on a stable startup voltage when the second capacitor C2 is fully charged. Therefore, the startup voltage is only related to the capacitance values ​​of the first capacitor C1 and the second capacitor C2. The larger the capacitance difference between the first capacitor C1 and the second capacitor C2, the faster the charging speed of the second capacitor C2, the smaller the voltage drop across the first capacitor C1 when the switching power supply starts, and the shorter the corresponding startup time. Therefore, for switching power supplies in different application scenarios, as long as these switching power supplies all use the startup circuit 1 provided in this application, and the startup circuit 1 uses the same first capacitor C1 and second capacitor C2, the startup time of each switching power supply will be consistent (or basically consistent).

[0023] It is easy to understand that at this time, the start switch S0 only needs to handle the charging voltage and charging current when the first capacitor C1 charges the second capacitor C2. Therefore, when designing and selecting the start switch S0, it is only necessary to design the current carrying capacity and voltage withstand capacity based on the voltage across the first capacitor C1, especially the full-charge voltage after the first capacitor C1 is fully charged. It is unrelated to the output voltage and output current of the battery. In comparison, the requirements for the current carrying capacity and voltage withstand capacity of the start switch S0 are smaller, which allows the start switch S0 to be implemented with a smaller size and lower cost.

[0024] It should be noted that, in addition to the startup circuit 1 and the driver chip U0, the switching power supply also includes a transformer T1 and a power transistor Q0. Once the driver chip U0 successfully starts up, it outputs a drive signal to the power transistor Q0. Under the action of the driver chip U0, the power transistor Q0 begins to operate, and the switching power supply completes its startup. At this time, the auxiliary winding N2 of the transformer T1 in the switching power supply will work normally, outputting electrical energy and taking over the power supply to the driver chip U0. At this point, the start switch S0 can be turned off, and the switching power supply begins to operate normally. The start switch S0 is only turned on when power is needed and is turned off again after the switching power supply has completed startup; when power is not needed, the start switch S0 remains in the off state.

[0025] It is easy to understand that once the stacked and fabricated batteries are connected to the startup circuit 1 of the switching power supply, the first capacitor C1 will begin charging. This charging process is relatively fast, especially when the battery voltage level is high, the first capacitor C1 will quickly reach a fully charged state. Therefore, the switching power supply can be started by operating the startup switch S0 shortly after the circuit connection. In practical applications, you can wait for the first capacitor C1 to be fully charged before confirming whether to start the power supply via switch S0 according to the actual application requirements. Alternatively, you can start the switching power supply after the first capacitor C1 has charged to a certain level (as long as it can support the second capacitor C2 to charge to the startup voltage of the driver chip U0). The resistance value of the first current limiting module R1 will affect the charging speed of the first capacitor C1. Therefore, the resistance value of the first current limiting module R1 can be configured according to the actual application to achieve fast charging of the first capacitor C1 after the circuit connection. This application does not make any special restrictions on the specific type and implementation method of the first current limiting module R1. It can be implemented using a single resistor element or multiple resistor elements connected in series. Its specific resistance value can be set and adjusted according to the actual application requirements.

[0026] It should be noted that this application does not impose any special limitations on the specific types and implementation methods of the first capacitor C1 and the second capacitor C2. The capacitance values ​​of the first capacitor C1 and the second capacitor C2 can be designed according to actual application requirements, such as the need for a sufficiently short startup time for the switching power supply (e.g., starting the driver chip U0 within 1 second after the start switch S0 is turned on). This application does not impose any special limitations on the specific type and implementation method of the start switch S0. Its operation control can be implemented in various ways. Considering the condition of power-off during startup of the switching power supply, and to adapt to battery application design, the start switch S0 can be implemented as a push-button switch. When the push-button switch is pressed, the circuit is closed (corresponding to the on state); when it is not pressed, the circuit is open (corresponding to the off state). The operator can manually operate the push-button switch (press or release) to control whether the switching power supply is started or not. The cost of the push-button switch itself and the control cost are relatively low, reducing the implementation cost of the start switch S0.

[0027] It should be further noted that this application does not impose any special limitations on the specific circuit topology of the driver chip U0 and the switching power supply. The driver chip U0 can be implemented using various chips capable of driving the power transistor Q0 in the switching power supply, such as the UCC28C44 chip. This application also does not impose any special limitations on the specific type of battery or its implementation method; it can be any type of battery, battery pack, or battery group. The startup circuit 1 of the switching power supply provided in this application is also applicable to other power supply scenarios. The input power supply connected to the startup circuit 1 is not limited to batteries; it can also be other types of power supplies, enabling multiple switching power supplies connected to input power supplies of different voltage levels to start up with a substantially consistent startup time.

[0028] This invention provides a startup circuit 1 for a switching power supply, used to enable the startup of the switching power supply. It is applicable to BMS power supply scenarios with different series-connected high-voltage batteries, achieving a relatively consistent startup time even when different PACKs are connected in series, i.e., the input power supply voltages of the switching power supply are inconsistent. Multiple switching power supplies for different application scenarios can complete startup based on the same or substantially consistent startup time. Furthermore, the startup switch S0 can be implemented with a smaller size and lower cost, effectively reducing the cost of the startup circuit 1 and the entire switching power supply. In addition, the smaller size of the startup switch S0 makes layout easier during circuit design, reducing the size of the startup circuit 1 and the entire switching power supply.

[0029] Based on the above embodiments, see Figure 2 As shown, Figure 2A schematic diagram of a switching power supply provided by the present invention. As an optional embodiment, the startup circuit 1 of the switching power supply further includes: The first voltage regulator is connected in parallel across the first capacitor C1 to provide overvoltage protection for the first capacitor C1. And / or, The second voltage regulator is connected in parallel across the two ends of the second capacitor C2 to provide overvoltage protection for the second capacitor C2.

[0030] It is understood that, in order to protect the first capacitor C1 and / or the second capacitor C2, the startup circuit 1 can further be equipped with a first voltage regulator connected in parallel with the first capacitor C1 and / or a second voltage regulator connected in parallel with the second capacitor C2. These two voltage regulators can effectively regulate and clamp the voltage across the corresponding capacitor. The voltage regulators can stabilize the voltage across the corresponding capacitor near a specific voltage, which is usually the upper limit of the voltage during the charging process of the corresponding capacitor. This ensures that after the corresponding capacitor is charged to the upper limit of the voltage, the voltage across it will not continue to rise, thus maintaining voltage stability and preventing overvoltage of the corresponding capacitor. This application does not specifically limit the specific type and implementation method of the first and second voltage regulators. The voltage regulation values ​​of the first and second voltage regulators can be designed based on the final voltage across the corresponding capacitor after it is fully charged. The voltage regulation value of the first voltage regulator is greater than the voltage regulation value of the second voltage regulator, and the voltage regulation value of the second voltage regulator needs to be greater than or equal to the startup voltage of the driver chip U0.

[0031] It should be noted that when a first voltage regulator and / or a second voltage regulator are configured, the voltage across the corresponding capacitor after it is fully charged will be clamped to the voltage regulation value set by the corresponding voltage regulator. Therefore, the startup time of the switching power supply also depends on the voltage regulation value of the first voltage regulator and / or the second voltage regulator. In other words, the startup time of the switching power supply depends on the capacitance values ​​of the first capacitor, the second capacitor, the first voltage regulator, and the second voltage regulator. Therefore, the capacitance values ​​of the first capacitor C1, the second capacitor C2, the first voltage regulator, and the second voltage regulator can be comprehensively designed according to the required startup time. When a first voltage regulator is configured, the current carrying capacity and voltage withstand capacity of the start switch S0 are positively correlated with the voltage regulation value of the first voltage regulator. The start switch S0 can be designed and selected directly based on the voltage regulation value of the first voltage regulator, and the load voltage matched by its voltage withstand capacity can be directly achieved using the voltage regulation value of the first voltage regulator.

[0032] Specifically, by setting the first voltage regulator and / or the second voltage regulator, the safety of the first capacitor C1 and / or the second capacitor C2 can be effectively guaranteed, and the safety and reliability of the startup circuit 1 and the entire switching power supply can be improved. The circuit structure is simple and easy to implement, which is conducive to the simple implementation of the startup circuit 1 and the entire switching power supply.

[0033] As an optional embodiment, the first voltage regulator is a first Zener diode D1, with the positive terminal of the first Zener diode D1 connected to the first power supply ground and the negative terminal connected to the second terminal of the first capacitor C1. The second voltage regulator is a second Zener diode D2. The positive terminal of the second Zener diode D2 is connected to the first power supply ground, and the negative terminal is connected to the first terminal of the second capacitor C2.

[0034] It is understood that both the first and second voltage regulator devices can be implemented using Zener diodes, effectively regulating and clamping the voltage across the first capacitor C1 and the second capacitor C2 by utilizing the physical characteristic of reverse breakdown of the PN junction. This application does not impose any specific limitations on the specific type or implementation method of the first Zener diode D1 and the second Zener diode D2.

[0035] Specifically, Zener diodes can be directly used to implement the first and / or second voltage regulator devices. The structure is simple, easy to implement, low in cost, small in size, easy to integrate, and has a fast response speed and high reliability; it can effectively ensure circuit safety.

[0036] As an optional embodiment, the startup circuit 1 of the switching power supply further includes: The second current limiting module R2 has its first end connected to the second end of the start switch S0, and its second end connected to the first end of the second capacitor C2 and the power supply terminal of the driver chip U0 in the switching power supply.

[0037] It is easy to understand that, to further improve the safety of the charging process of the first capacitor C1 to the second capacitor C2, a second current-limiting module R2 connected in series with the start switch S0 can be added to limit the charging current of the first capacitor C1 to the second capacitor C2. When the start switch S0 is on, the first capacitor C1 charges the second capacitor C2 through the on-state start switch S0 and the second current-limiting module R2. This application does not specifically limit the specific type and implementation method of the second current-limiting module R2; it can be implemented directly using a resistor element, either a single resistor element or multiple resistor elements connected in series. The resistance value of the second current-limiting module R2 will affect the charging speed of the second capacitor C2, thus the start-up time is also related to the resistance value of the second current-limiting module R2. The resistance value of the second current-limiting module R2 can be designed according to actual application requirements. Furthermore, the resistance value of the second current-limiting module R2 will also affect the selection of the current-carrying capacity of the start switch S0. The load current matching the current-carrying capacity can be determined directly based on the ratio of the load voltage matched by the withstand voltage capability to the resistance value of the second current-limiting module R2.

[0038] Specifically, the design of the second current limiting module R2 enables overcurrent protection during the charging process of the first capacitor C1 to the second capacitor C2, further ensuring the safety of the second capacitor C2 and improving the safety and reliability of the startup circuit 1 and the entire switching power supply. The circuit structure is simple and easy to implement, which is beneficial to the simple implementation of the startup circuit 1 and the entire switching power supply.

[0039] See Figure 3 As shown, Figure 3 A schematic diagram of a discharge circuit provided by the present invention. As an optional embodiment, the startup circuit 1 of the switching power supply further includes: The discharge circuit has its input terminal connected to the first terminal of the second capacitor C2. It is used to discharge the second capacitor C2 when the battery is undervoltage, so as to control the switching power supply to stop working.

[0040] It is understandable that as the load and switching power supply consume power, the battery may experience undervoltage. Considering that if the switching power supply continues to operate and consume battery power when the battery is undervoltage, it will lead to severe undervoltage, causing battery damage or even failure. Therefore, the switching power supply should ideally stop operating promptly when the battery is undervoltage to prevent severe undervoltage and failure. Existing technology uses a switching device with shunt trip function to implement a start switch S0 connected in series between the switching power supply input and the battery. When the battery is undervoltage, the shunt trip function controls the start switch S0 to open, thereby reducing battery power consumption. This further increases the size and cost of the start switch S0. To solve this technical problem, this application further adds a discharge circuit to the start circuit 1. The discharge circuit can discharge the second capacitor C2 when the battery is undervoltage, causing the voltage at the first terminal of the second capacitor C2 to drop below the operating voltage of the driver chip U0. Once this voltage drops, the driver chip U0 will stop driving the power transistor Q0, thereby controlling the switching power supply to stop operating. This application does not specifically limit the specific type and implementation method of the discharge circuit. The discharge circuit can also intervene in a timely manner to control the switching power supply to stop working when other abnormalities occur in the battery, not limited to undervoltage abnormalities.

[0041] Specifically, by further adding a discharge circuit, the switching power supply stops operating when the battery is undervoltage. Timely discharge when the battery is undervoltage controls the switching power supply to stop working, ensuring the battery only consumes its own power, reducing battery power consumption, and thus preventing damage or even failure of the battery due to severe undervoltage, ensuring battery safety. At the same time, the use of switching devices with shunt trip functions to implement the start switch S0 is avoided, further reducing the size and implementation cost of the start switch S0.

[0042] As an optional embodiment, the discharge circuit includes: The first terminal of the discharge resistor R0 is connected to the first terminal of the second capacitor C2. The discharge switch has its first terminal connected to the second terminal of the discharge resistor R0 and its second terminal connected to the first power supply ground. It is used to turn on when the battery is undervoltage to discharge the second capacitor C2, and to turn off when the battery is not undervoltage.

[0043] It is easy to understand that, in order to achieve rapid discharge of the second capacitor C2, the discharge circuit can specifically use a discharge resistor R0 and a discharge switch connected in series. When the battery is undervoltage, the discharge switch is turned on, and the first terminal of the second capacitor C2 discharges rapidly through the discharge resistor R0 and the on and grounded discharge switch, causing the voltage at the power supply terminal VDD of the driver chip to be undervoltage, thereby controlling the driver chip U0 to stop working, and thus controlling the switching power supply to stop working. This application does not specifically limit the specific type and implementation method of the discharge resistor R0 and the discharge switch.

[0044] Specifically, the discharge switch effectively controls whether or not the power supply is discharged, and the discharge resistor R0 enables rapid discharge of the second capacitor C2. Battery undervoltage occurs after the switching power supply has started and is operating, at which point the start switch S0 is already off. Therefore, after the discharge circuit controls the switching power supply to stop operating, the off start switch S0 will not restart. Thus, this startup circuit 1 design prevents repeated starting and stopping of the driver chip U0 and the switching power supply, effectively reducing power consumption in standby mode. The discharge circuit has a simple structure and is easy to implement, facilitating the simplified implementation of startup circuit 1 and the entire switching power supply.

[0045] As an optional embodiment, the discharge switch is an optocoupler U1, the collector C of the optocoupler U1 is connected to the second end of the discharge resistor R0, and the emitter E is connected to the first power supply ground; The discharge circuit also includes: The third current limiting module R3 has its first terminal connected to the output terminal of the switching power supply and its second terminal connected to the anode A of the optocoupler U1. The controllable switch Q1 has its first terminal connected to the cathode K of the optocoupler U1, its second terminal connected to the second power ground, and its control terminal connected to the output terminal of the battery management system. It is used to turn on when the discharge signal DO1 output by the battery management system is received, and to turn off when the discharge signal DO1 output by the battery management system is not received. Among them, the discharge signal DO1 is generated when the battery management system detects that the battery is undervoltage.

[0046] Understandably, the battery itself has a BMS to manage its operation. Therefore, the BMS can detect undervoltage in a timely manner and generate a discharge signal to instruct the discharge circuit to begin discharging. Since the BMS is powered by a switching power supply, its input is connected to the output. The output and input of the switching power supply are isolated by the output winding and primary winding N1 of transformer T1. Furthermore, the voltage levels of the output and input may differ; the input corresponds to the battery voltage and is at a higher voltage, while the output corresponds to the BMS's power requirements and is at a lower voltage. Therefore, considering high-voltage insulation, electrical isolation, and interference immunity, the switching power supply is designed with a non-common ground for isolation between its input and output terminals.

[0047] Specifically, in a switching power supply, the primary winding N1 and the auxiliary winding N2 of transformer T1 will use the first power supply ground (e.g., Figure 1 The GND0 shown and Figure 2As shown in BAT-), the output side corresponding to the output winding will use a second power ground (such as BAT-). Figure 2 (DGND shown). The BMS is on the output side, and the startup circuit 1 is on the primary side. The discharge control process via the BMS involves the secondary side circuit controlling the primary side circuit. Since these two circuits are not grounded, to control the discharge circuit in startup circuit 1 via the BMS, the discharge switch in the discharge circuit is implemented using an optocoupler U1 with isolation function. The output side of optocoupler U1 is connected in series with the discharge resistor R0 to discharge the second capacitor C2. The input side of optocoupler U1 is connected in series with the third current limiting module R3 and the controllable switch Q1, working in conjunction with the discharge signal DO1 output by the BMS and the controllable switch Q1 to control the conduction between the collector and emitter on the output side.

[0048] It's easy to understand that the BMS output is connected to the control terminal of the controllable switch Q1. The BMS monitors the battery status in real time. When the battery is undervoltage, it generates a discharge signal DO1 and outputs DO1 to the control terminal of the controllable switch Q1. Upon receiving the discharge signal DO1, the controllable switch Q1 conducts, using the output voltage of the switching power supply connected to the first terminal of the third current limiting module R3 to apply a positive voltage to the anode A of the optocoupler U1. This causes the LED on the input side of the optocoupler U1 to light up. The LED then controls the phototransistor on the output side of the optocoupler U1 to conduct, connecting the collector C and emitter E of the phototransistor. This allows the second capacitor C2 to discharge rapidly through the discharge resistor R0 and the conducting phototransistor. When the battery is not undervoltage, the controllable switch Q1 remains off, the phototransistor on the output side of the optocoupler U1 is off, and the driver chip U0 and the switching power supply operate normally.

[0049] It should be noted that this application does not impose any special limitations on the specific type and implementation method of the optocoupler U1; other types of switching devices with isolation functions can also be used. Similarly, this application does not impose any special limitations on the specific type and implementation method of the third current limiting module R3 and the controllable switch Q1. The third current limiting module R3 can be directly implemented using resistors, and the controllable switch Q1 can be implemented using transistors or other controllable switching devices. Furthermore, this application does not impose any special limitations on the specific implementation method of the discharge signal DO1; it can be implemented using level signals, etc.

[0050] Specifically, through the design of optocoupler U1, the BMS can be effectively used to control the discharge circuit, thereby effectively controlling the switching power supply to stop working; the circuit structure is simple and easy to implement, which is conducive to the simple implementation of the startup circuit 1 and the entire switching power supply.

[0051] As a specific embodiment, such as Figure 2As shown, when the switching power supply is operating normally, the output voltage of the auxiliary winding N2 of transformer T1 in the switching power supply is defined as Vcc, the output voltage of the output winding of transformer T1 in the switching power supply is defined as Vout, the battery voltage input to the switching power supply is defined as Vin, and the voltage regulation value of the first Zener diode D1 connected in parallel across the first capacitor C1 is V. ZD1 The voltage across the second capacitor C2 at time t is V. start(t) The charging current when the first capacitor C1 charges the second capacitor C2 is I. start .but: (1) (2) Where R2 is the resistance of the second current limiting module R2, and C2 is the capacitance of the second capacitor C2.

[0052] Based on the above embodiments, the entire switching power supply has three operating states.

[0053] The first operating state is the initial state before the switching power supply starts. After the battery PCAK is stacked and connected in series with the startup circuit 1 of the switching power supply and the switching power supply, the battery will use its stored electrical energy to charge the first capacitor C1 through the first current limiting module R1. The maximum voltage corresponding to the first capacitor C1 being fully charged is equal to the voltage regulation value of the first Zener diode D1 (for the UCC28C44 chip, a first Zener diode with a voltage regulation value of 25V can be used).

[0054] The second operating state is the startup state of the power supply to the start switch S0 when it is turned on. When the start switch S0 is turned on, the first capacitor C1 charges the second capacitor C2 through the second current limiting module R2. Assuming the second current limiting module R2 is implemented using a 1kΩ resistor, the startup voltage of the driver chip U0 is 15.5V, the capacitance of the first capacitor C1 is 10 times that of the second capacitor C2, and the capacitance of the second capacitor C2 is set to 47uF. In this case, after the start switch S0 is turned on, the first capacitor C1 charges the second capacitor C2, causing the voltage across the second capacitor C2 to exceed the startup voltage of the driver chip U0 within 0.1s; and the current is also greater than the 0.1mA startup current required by the driver chip U0. The voltage regulation value of the first Zener diode D1 is determined to be the maximum load voltage matching the voltage withstand capability of the start switch S0, and the load current corresponding to the current carrying capacity of the start switch S0 can be designed to be less than 10mA.

[0055] The third operating state is the normal operating state of the switching power supply after the start switch S0 is turned off. After the switching power supply has finished starting, the start switch S0 is turned off. At this time, the charging circuit between the first capacitor C1 and the second capacitor C2 is disconnected. The auxiliary winding N2 of the transformer T1 in the switching power supply is now working normally, and the output power supplies the driver chip U0, allowing the switching power supply to continue operating normally. During normal operation, if the BMS detects a low battery voltage, it can control the output side of the optocoupler U1 to conduct via a discharge signal, allowing the second capacitor C2 to discharge through the discharge resistor R0. This causes the power supply terminal VDD of the driver chip to fall below the operating voltage, thereby shutting down the switching power supply. The power transistor Q0 stops operating without loss. Furthermore, since the start switch S0 is now off, the switching power supply will not restart repeatedly, effectively preventing the switching power supply from affecting battery power consumption and avoiding standby power consumption caused by repeated start-stop cycles. At this time, only the first current limiting module R1 in the entire switching power supply will cause minimal loss, and the battery burden is relatively small.

[0056] To solve the above-mentioned technical problems, the present invention also provides a switching power supply, including a transformer T1, a power transistor Q0, a driver chip U0, and a startup circuit 1 of the switching power supply as described above. The first end of the primary winding N1 of the transformer T1 is connected to the output end of the battery, the second end of the primary winding N1 is connected to the first end of the power transistor Q0, the control end of the power transistor Q0 is connected to the signal output end of the driver chip U0, and the power supply terminal VDD of the driver chip is connected to the output end of the startup circuit 1 of the switching power supply and the auxiliary winding N2 of the transformer T1, respectively. The startup circuit 1 of the switching power supply is used to supply power to the driver chip U0 to start the switching power supply S0 when it is necessary to start the switching power supply S0. The auxiliary winding N2 of transformer T1 is used to supply power to the driver chip U0 after the switching power supply has finished starting.

[0057] It is easy to understand that the startup circuit 1 of the switching power supply based on the above embodiment can provide a switching power supply for powering the BMS, applicable to various types of series-connected high-voltage batteries. After the driver chip U0 operates normally and drives the power transistor Q0, both the auxiliary winding N2 and the output winding of the transformer T1 operate normally and can output electrical energy. The auxiliary winding N2 outputs electrical energy to power the driver chip U0, and the output winding outputs electrical energy to power the BMS. This application does not make any special limitations on the specific types and implementation methods of the transformer T1, power transistor Q0, and driver chip U0 in the switching power supply. The input terminal of the switching power supply also needs to be connected to the output terminal of the battery to use the battery's output electrical energy to power the BMS. Therefore, the input terminal of the switching power supply, namely the first end of the primary winding N1 of the transformer T1 and the input terminal of the startup circuit 1 of the switching power supply (the input terminal of the first current limiting module R1), are both connected to the output terminal of the battery.

[0058] It should be noted that other circuit structures can be configured in switching power supplies according to requirements, and this application does not impose any special limitations on them. For example... Figure 2 As shown, the second terminal of power transistor Q0 can be connected to the first power supply ground through a series resistor R5. Resistor R5 limits the current flowing through power transistor Q0 during operation, ensuring safety. The current detection terminal Isense of the driver chip U0 is connected to the series connection point of power transistor Q0 and resistor R5, detecting the current flowing through power transistor Q0 in real time to achieve feedback closed-loop control of power transistor Q0. In the secondary-side circuit corresponding to secondary winding N3, a series diode D4 can be further set to specify the direction of the output power. Simultaneously, a parallel resistor R6 and capacitor C3 are used for filtering, ensuring the accuracy and stability of the power supply voltage output to the BMS.

[0059] For an introduction to the switching power supply provided by this invention, please refer to the above embodiment of the switching power supply startup circuit; this invention will not be described in detail here.

[0060] As an optional embodiment, the switching power supply further includes: The positive terminal of rectifier diode D3 is connected to the first end of the auxiliary winding N2 of transformer T1. It is used to convert the AC power output from the auxiliary winding N2 of transformer T1 into DC power to supply power to the driver chip U0 after the switching power supply has completed the startup. The second end of the auxiliary winding N2 of transformer T1 is connected to the first power supply ground; The current-limiting resistor R4 has its first end connected to the negative terminal of the rectifier diode D3, and its second end connected to the power supply terminal VDD of the driver chip.

[0061] It is understandable that, considering the operating voltage required by the driver chip U0 is typically DC, it is best to connect a rectifier diode D3 and a current-limiting resistor R4 in series between the auxiliary winding N2 and the power supply terminal VDD of the driver chip. The rectifier diode D3 converts the output power of the auxiliary winding N2 of the transformer T1 into DC power to effectively supply power to the driver chip U0. Simultaneously, the series current-limiting resistor R4 limits the supply current from the auxiliary winding N2 to the driver chip U0, ensuring the safety and reliability of the driver chip U0. This application does not specifically limit the specific type and implementation method of the rectifier diode D3 and the current-limiting resistor R4.

[0062] To solve the above-mentioned technical problems, the present invention also provides a battery system, including a battery, a battery management system, and a switching power supply as described above. The positive output terminal of the battery is connected to the first end of the primary winding N1 of the transformer T1 in the switching power supply and the input terminal of the starting circuit 1 of the switching power supply. The negative output terminal of the battery serves as the first power ground. The input terminal of the battery management system is connected to the output terminal of the switching power supply, and the output terminal of the battery management system is connected to the control terminal of the starting circuit 1 of the switching power supply.

[0063] It is easy to understand that the battery specifically includes a positive output terminal and a negative output terminal. Power is supplied by forming a circuit with the load through these two terminals. Therefore, the connection between the starting circuit 1 of the switching power supply and the input terminal of the switching power supply and the battery is specifically connected to the positive output terminal of the battery. The negative output terminal of the battery serves as the first power ground of the primary side circuit of the switching power supply. This application does not specifically limit the specific implementation of the first and second power grounds. The connection between the input terminal of the battery management system and the output terminal of the switching power supply is specifically connected to both ends of the secondary winding N3 of the switching power supply to receive power from the switching power supply. The connection between the output terminal of the battery management system and the control terminal of the starting circuit 1 of the switching power supply is specifically connected to the discharge circuit, particularly the control terminal of the controllable switch Q1 in the discharge circuit, to stop the switching power supply from operating when the battery is undervoltage.

[0064] For an introduction to the battery system provided by this invention, please refer to the above embodiment of the starting circuit of the switching power supply; this invention will not be described in detail here.

[0065] The various embodiments described in this specification are presented in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. It should also be noted that in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0066] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A startup circuit for a switching power supply, characterized in that, include: The first current limiting module has its first terminal connected to the output terminal of the battery. The first capacitor, with its first terminal connected to the first power supply ground, is used to charge the battery based on the electrical energy output when the battery outputs electrical energy. A power switch is configured such that its first terminal is connected to the second terminal of the first current limiting module and the second terminal of the first capacitor, respectively, and is used to turn on when the switching power supply needs to be started and turn off when the switching power supply has completed the startup process. The second capacitor has its first end connected to the second end of the start switch and the power supply terminal of the driver chip in the switching power supply, and its second end connected to the first power ground. It is used to charge the first capacitor based on the electrical energy stored in it when the start switch is turned on, so that the switching power supply can be started when the voltage at the first end of the second capacitor reaches the start voltage of the driver chip.

2. The startup circuit of the switching power supply according to claim 1, characterized in that, Also includes: The first voltage regulator is connected in parallel across the first capacitor to provide overvoltage protection for the first capacitor. And / or, The second voltage regulator is connected in parallel across the second capacitor to provide overvoltage protection for the second capacitor.

3. The startup circuit of the switching power supply according to claim 2, characterized in that, The first voltage regulator is a first Zener diode, with its positive terminal connected to the first power supply ground and its negative terminal connected to the second terminal of the first capacitor. The second voltage regulator is a second Zener diode, with its anode connected to the first power supply ground and its cathode connected to the first terminal of the second capacitor.

4. The startup circuit of the switching power supply according to claim 1, characterized in that, Also includes: The second current limiting module has its first end connected to the second end of the start switch, and its second end connected to the first end of the second capacitor and the power supply terminal of the driver chip in the switching power supply.

5. The startup circuit of the switching power supply according to any one of claims 1 to 4, characterized in that, Also includes: The discharge circuit has its input terminal connected to the first terminal of the second capacitor. It is used to discharge the second capacitor when the battery is undervoltage, so as to control the switching power supply to stop working.

6. The startup circuit of the switching power supply according to claim 5, characterized in that, The discharge circuit includes: The first terminal of the discharge resistor is connected to the first terminal of the second capacitor. The discharge switch has its first end connected to the second end of the discharge resistor and its second end connected to the first power supply ground. It is used to turn on when the battery is undervoltage to discharge the second capacitor, and to turn off when the battery is not undervoltage.

7. The startup circuit of the switching power supply according to claim 6, characterized in that, The discharge switch is an optocoupler, the collector of the optocoupler is connected to the second end of the discharge resistor, and the emitter is connected to the first power supply ground; The discharge circuit further includes: The third current limiting module has its first end connected to the output terminal of the switching power supply and its second end connected to the anode of the optocoupler. A controllable switch has a first end connected to the cathode of the optocoupler, a second end connected to the second power ground, and a control end connected to the output end of the battery management system of the battery. It is used to turn on when a discharge signal output by the battery management system is received, and turn off when no discharge signal output by the battery management system is received. The discharge signal is generated when the battery management system detects that the battery is undervoltage.

8. A switching power supply, characterized in that, The power supply includes a transformer, a power transistor, a driver chip, and a startup circuit for a switching power supply as described in any one of claims 1-7. The first end of the primary winding of the transformer is connected to the output terminal of the battery, the second end of the primary winding is connected to the first end of the power transistor, the control terminal of the power transistor is connected to the signal output terminal of the driver chip, and the power supply terminal of the driver chip is connected to the output terminal of the startup circuit of the switching power supply and the auxiliary winding of the transformer, respectively. The startup circuit of the switching power supply is used to supply power to the driver chip to start the switching power supply when it is required to start the switching power supply; The auxiliary winding of the transformer is used to supply power to the driver chip after the switching power supply has finished starting.

9. The switching power supply according to claim 8, characterized in that, Also includes: The rectifier diode, with its positive terminal connected to the first end of the auxiliary winding of the transformer, is used to convert the alternating current output from the auxiliary winding of the transformer into direct current, so as to supply power to the driver chip after the switching power supply has completed startup. The second end of the auxiliary winding of the transformer is connected to the ground of the first power supply; The current-limiting resistor has its first end connected to the negative terminal of the rectifier diode and its second end connected to the power supply terminal of the driver chip.

10. A battery system, characterized in that, The device includes a battery, a battery management system, and a switching power supply as described in claim 8 or 9. The positive output terminal of the battery is connected to the first end of the primary winding of the transformer in the switching power supply and the input terminal of the startup circuit of the switching power supply. The negative output terminal of the battery serves as a first power ground. The input terminal of the battery management system is connected to the output terminal of the switching power supply, and the output terminal of the battery management system is connected to the control terminal of the startup circuit of the switching power supply.

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