Battery voltage limiting protection circuit, switching power supply and battery protection method

Abstract

The invention provides a battery voltage limiting protection circuit, a switching power supply and a battery protection method. The circuit is applied to a direct current input circuit comprising a control chip and a first capacitor. The battery voltage limiting protection circuit comprises a branch control unit and a branch load unit. The branch control unit controls the branch load unit to be conducted after the control chip is started, so that the preset load is connected to the two ends of the first capacitor; when the voltage of the direct current source is lower than the preset voltage and the control chip is turned off, the first capacitor simultaneously discharges to the preset load and the control chip, and the voltage of the first capacitor is rapidly reduced below the starting voltage of the control chip through the shunting effect, so that the control chip is reliably prevented from being restarted, the over-discharge of the direct current source (such as a battery) is effectively avoided, and the service life is prolonged. The service life is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic circuits, and in particular to a battery voltage limiting protection circuit, a switching power supply and a battery protection method. BACKGROUND

[0002] In modern electronic power supply systems, especially those that use AC / DC mutual standby power supply (such as communication base stations, data centers, industrial control systems, and new energy power stations), a direct current source usually uses an energy storage battery as a backup energy source. When the system is normally running, the AC power grid is preferentially powered; when the AC power fails, it is seamlessly switched to direct current battery power supply to ensure uninterrupted operation of the load.

[0003] In such a system, the core of the direct current input circuit is a control chip (for example, a PWM controller), which is responsible for managing the energy conversion on the direct current side (such as controlling the on-off of the switching tube). The normal operation of the control chip is crucial for the system to successfully switch to direct current power supply when the AC power fails.

[0004] However, the inventors have found through in-depth research that when the system is completely powered by a direct current source (battery) and the battery voltage gradually drops due to continuous discharge, a hidden technical problem will emerge and pose a serious threat to the battery life. Specifically, when the battery voltage drops to the under-voltage protection threshold of the control chip, the control chip will perform a shutdown operation to protect itself and the battery. Ideally, the system should stop working completely. However, in reality, the capacitor (supply capacitor) connected in parallel with the control chip has been fully charged in the last working period, and there is still a considerable amount of charge between its two ends, and its voltage may still be higher than the minimum starting voltage of the control chip. This leads to a vicious cycle: after the control chip is turned off, the capacitor continues to supply power to it, which may cause the control chip power voltage (VCC) to rise above the starting voltage after a short drop, causing the control chip to restart. Once the control chip restarts, the system will again draw energy from the battery that is already in an under-voltage state, even if it is only a small current, which will exacerbate the depth of battery discharge. This "under-voltage shutdown-capacitor maintenance-chip restart-continue discharge" cycle will continue to consume the remaining power of the battery, eventually leading to over-discharge of the battery and significantly shortening its service life.

[0005] Therefore, there is an urgent need for an effective protection circuit that can reliably prevent the control chip from restarting due to the residual charge of the first capacitor after the control chip is turned off due to low voltage of the direct current source, thereby completely avoiding over-discharge of the direct current source. SUMMARY

[0006] The embodiments of the present application provide a battery voltage limiting protection circuit, a switching power supply and a battery protection method to prevent the control chip from restarting and protect the battery from over-discharge when the voltage of the direct current source is too low.

[0007] In a first aspect, embodiments of this application provide a battery voltage limiting protection circuit applied to an AC / DC power supply system. The AC / DC power supply system includes a DC input circuit, which includes a control chip and a first capacitor. The first capacitor is used to supply power to the control chip. The battery voltage limiting protection circuit includes a branch control unit and a branch load unit. The branch load unit includes a preset load, and a first terminal and a second terminal of the branch load unit are used to connect to the two ends of the first capacitor.

[0008] The first end of the branch control unit is used to connect to a DC source, the second end of the branch control unit is connected to the second end of the branch load unit, and the third end of the branch control unit is connected to the control end of the branch load unit.

[0009] The branch control unit is used to control the first and second terminals of the branch load unit to be turned on after the control chip is started, so that the two ends of the preset load are connected to the two ends of the first capacitor; thereby, after the control chip is turned off, the first capacitor discharges to the preset load and the control chip to prevent the control chip from restarting.

[0010] In one possible implementation, the branch control unit includes a first resistor and a fourth capacitor; a first end of the first resistor serves as a first end of the branch control unit and is used to connect to the DC source; a second end of the first resistor is connected to a first end of the fourth capacitor and a third end of the branch control unit; and a second end of the fourth capacitor serves as a second end of the branch control unit and is connected to a second end of the branch load unit.

[0011] In one possible implementation, the capacitance of the fourth capacitor is greater than that of the first capacitor.

[0012] In one possible implementation, the branch load unit further includes a second switching transistor; the preset load includes a second resistor; the first end of the second resistor serves as the first end of the branch load unit and is used to connect to the first end of the first capacitor; the second end of the second resistor is connected to the first end of the second switching transistor; the second end of the second switching transistor serves as the second end of the branch load unit and is used to connect to the second end of the first capacitor; the control end of the second switching transistor serves as the control end of the branch load unit and is used to connect to the third end of the branch control unit.

[0013] In one possible implementation, the DC input circuit further includes a startup module; a first terminal of the startup module is used to connect to the DC source, and a second terminal of the startup module is used to connect to the first terminal of the first capacitor; the startup module is used to charge the first capacitor when the control chip is in an inactive state and the voltage of the DC source is greater than a preset voltage.

[0014] Secondly, embodiments of this application provide a switching power supply, including the battery voltage limiting protection circuit described in the first aspect above.

[0015] Thirdly, embodiments of this application provide an AC / DC power supply system, including an AC source, a DC source, a battery voltage limiting protection circuit as described in the first aspect above, and a load.

[0016] Fourthly, this application provides a battery protection method applied to an AC / DC power supply system. The method includes: detecting the voltage of a DC source; turning off a control chip when the voltage of the DC source is less than or equal to a preset voltage; controlling a branch load unit to conduct through a branch control unit, so that a preset load is connected across a first capacitor; wherein the first capacitor is used to supply power to the control chip, and the shunt of the preset load prevents the control chip from restarting.

[0017] The beneficial effects of this application's embodiments are: by setting up branch control units and branch load units, after the control chip is turned off, the discharge speed of the first capacitor is accelerated by utilizing the preset load shunt, preventing the control chip from restarting due to insufficient power supply, thereby avoiding over-discharge of the battery and extending battery life. At the same time, this circuit structure is simple and easy to integrate into existing AC / DC power supply systems. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Fig. 1 This is a schematic diagram of the AC / DC power supply system provided in this application;

[0020] Fig. 2 This is a first structural schematic diagram of the AC / DC power supply switching circuit provided in the embodiments of this application;

[0021] Fig. 3 This is a schematic diagram of the second structure of the AC / DC power supply switching circuit provided in the embodiments of this application;

[0022] Fig. 4 This is a schematic diagram of the AC / DC power supply switching circuit provided in another embodiment of this application;

[0023] Fig. 5 This is a detailed schematic diagram of the battery voltage limiting protection circuit provided in the embodiments of this application. Detailed Implementation

[0024] To enable those skilled in the art to better understand this solution, the technical solutions in the embodiments of this solution will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this solution, not all of them. Based on the embodiments of this solution, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this solution.

[0025] The term "comprising" and any other variations thereof in the specification, claims, and accompanying drawings of this invention mean "including but not limited to," and are intended to cover a non-exclusive inclusion, not limited to the examples listed herein. Furthermore, the terms "first" and "second," etc., are used to distinguish different objects, not to describe a specific order.

[0026] To make the purpose, technical solution, and advantages of this application clearer, the following will first refer to the appendix. Figs. 1 to 4 This paper describes the AC / DC power supply system used in the battery voltage limiting protection circuit of this application. The battery voltage limiting protection circuit of this application is mainly integrated into the DC input circuit of the system and is used to solve the over-discharge protection problem of the DC source (usually a battery).

[0027] See Figs. 1 to 4 The AC / DC power supply system includes an AC input circuit and a DC input circuit. The AC input circuit includes a first transformer (such as windings T1A, T1B, and T1C), and the DC input circuit includes a second transformer (such as windings T2A, T2B, and T2C), a control chip U1, a first switching transistor Q1, and a first capacitor C1. Its basic working principle is as follows: when the AC source is normal, the AC input circuit provides priority power; when the AC source fails, the system switches to DC power (battery) to ensure uninterrupted operation of the load. To ensure a smooth switching, a second-stage winding T1C is included in the AC input circuit to power the control chip U1 and the first capacitor C1 of the DC input circuit during AC power supply, preventing the control chip from locking up due to power loss before switching.

[0028] In the aforementioned AC / DC power supply system, the inventors discovered that when the system is powered by a DC source (battery) for an extended period, a unique technical problem arises: how to prevent over-discharge of the battery caused by the control chip restarting after undervoltage shutdown. The core of this application is precisely to solve this problem.

[0029] Please refer to this carefully. Fig. 5 This illustrates the detailed principle of the battery voltage limiting protection circuit according to an embodiment of this application. The circuit mainly includes a branch control unit and a branch load unit, which are integrated in the DC input circuit.

[0030] The branch control unit includes a first resistor R1 and a fourth capacitor C4. The first terminal of the first resistor R1 is connected to the positive terminal of the DC source (battery Bat) (i.e., the first terminal of the second primary winding T2A). The second terminal of the first resistor R1 is connected to the first terminal of the fourth capacitor C4 and the control terminal (gate) of the second switching transistor Q2 in the branch load unit. The second terminal of the fourth capacitor C4 is grounded.

[0031] The branch load unit includes a second resistor R2 (as a preset load) and a second switch Q2. The first terminal of the second resistor R2 is connected to the first terminal of the first capacitor C1 (i.e., the VCC power supply terminal of the control chip U1). The second terminal of the second resistor R2 is connected to the first terminal (drain) of the second switch Q2. The second terminal (source) of the second switch Q2 is grounded.

[0032] The working process and timing control of the battery voltage limiting protection circuit are as follows:

[0033] S1: System Power-On and Chip Startup: When the DC power source (battery) starts supplying power, the battery voltage is normal. The startup module (not shown in the diagram, but may include resistors and diodes) charges the first capacitor C1, while the battery charges the fourth capacitor C4 through the first resistor R1. The key design feature is that the capacitance of the fourth capacitor C4 is set to be much larger than that of the first capacitor C1 (C4 >> C1). Therefore, C1 charges much faster than C4. This allows the voltage on the first capacitor C1 to reach the startup voltage of the control chip U1 first, ensuring reliable startup and normal operation of the control chip. At this time, the voltage on the fourth capacitor C4 has not yet reached the turn-on threshold of the second switch Q2, Q2 is in the off state, and the second resistor R2 is not connected to the circuit, thus not affecting the normal startup of the system.

[0034] S2: Branch Load Unit Delayed Turn-On: After the control chip U1 starts, the system enters a steady state. The fourth capacitor C4 continues to be slowly charged. When the voltage across C4 gradually rises and reaches the turn-on threshold of the second switch Q2, Q2 turns on. At this time, the second resistor R2 is connected to the circuit in parallel with the first capacitor C1. During normal system operation, since the self-powered winding of the DC input circuit (such as the fourth secondary winding T2C) can provide continuous energy to the system, the shunt effect of the second resistor R2 is minimal, and the system operation is unaffected.

[0035] S3: Key mechanism for battery undervoltage protection and restart prevention: When the battery voltage drops to the preset undervoltage protection value due to continuous discharge, the control chip U1 performs a shutdown operation. At this time, without this protection circuit, the fully charged first capacitor C1 will discharge to the shut-off control chip U1 (which still has a small static current). The discharge curve is flat, and the voltage of C1 may remain above the startup voltage of U1, causing U1 to restart, thereby continuing to consume battery power and causing battery over-discharge.

[0036] In this application, since the second resistor R2 is connected in parallel across capacitor C1, when the control chip U1 is turned off, the charge stored in the first capacitor C1 needs to discharge simultaneously for the quiescent current of the control chip U1 and the load current of the second resistor R2. The second resistor R2 provides a significant shunt path (its current is typically much greater than the chip's quiescent current), which greatly accelerates the discharge rate of the first capacitor C1, causing its voltage to drop rapidly below the startup voltage of the control chip U1. This mechanism reliably prevents any attempt by the control chip U1 to restart, ensuring a complete system shutdown, effective battery protection, and avoiding over-discharge damage.

[0037] S4: Protection State and System Recovery: In the protection state (system shutdown), the battery consumes only microamps of current through the high-resistance first resistor R1 and the fourth capacitor C4 to ground, resulting in extremely low power consumption. When the battery is recharged or replaced, the voltage returns to normal, and the system will repeat the power-on startup process described above.

[0038] This application, by adding a load branch (second resistor R2 and second switch Q2) controlled by an RC delay circuit (first resistor R1 and fourth capacitor C4) to the DC input circuit, cleverly utilizes the time difference of capacitor charging to achieve a timing logic of "ensuring chip startup first, then connecting the protection load" with extremely low cost and a simple structure. Ultimately, when the battery is undervoltage, the shunt effect completely solves the problem of battery over-discharge caused by the restart of the control chip after shutdown. This circuit, organically combined with the aforementioned AC / DC power supply system, improves the reliability of the entire system.

[0039] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A battery voltage limiting protection circuit, characterized in that, The invention is applied to an AC / DC power supply system, which includes a DC input circuit, a control chip, and a first capacitor, wherein the first capacitor is used to power the control chip; the battery voltage limiting protection circuit includes a branch control unit and a branch load unit. The branch load unit includes a preset load, and the first and second ends of the branch load unit are used to connect to the two ends of the first capacitor. The first terminal of the branch control unit is used to connect to a DC source, the second terminal of the branch control unit is connected to the second terminal of the branch load unit, and the third terminal of the branch control unit is connected to the control terminal of the branch load unit. The branch control unit is used to control the first and second terminals of the branch load unit to be turned on after the control chip is started, so that the two ends of the preset load are connected to the two ends of the first capacitor; thereby, after the control chip is turned off, the first capacitor discharges to the preset load and the control chip to prevent the control chip from restarting.

2. The battery voltage limiting protection circuit according to claim 1, characterized in that, The branch control unit includes a first resistor and a fourth capacitor; The first end of the first resistor serves as the first end of the branch control unit and is used to connect to the DC source; the second end of the first resistor is connected to the first end of the fourth capacitor and the third end of the branch control unit. The second terminal of the fourth capacitor serves as the second terminal of the branch control unit and is connected to the second terminal of the branch load unit.

3. The battery voltage limiting protection circuit according to claim 2, characterized in that, The capacitance of the fourth capacitor is greater than that of the first capacitor.

4. The battery voltage limiting protection circuit according to claim 1, characterized in that, The branch load unit further includes a second switching transistor; the preset load includes a second resistor; The first end of the second resistor serves as the first end of the branch load unit and is used to connect to the first end of the first capacitor; the second end of the second resistor is connected to the first end of the second switching transistor. The second terminal of the second switching transistor serves as the second terminal of the branch load unit and is used to connect to the second terminal of the first capacitor. The control terminal of the second switching transistor serves as the control terminal of the branch load unit and is used to connect to the third terminal of the branch control unit.

5. The battery voltage limiting protection circuit according to claim 1, characterized in that, The DC input circuit also includes a startup module; The first end of the starting module is used to connect to the DC source, and the second end of the starting module is used to connect to the first end of the first capacitor; The startup module is used to charge the first capacitor when the control chip is in an inactive state and the voltage of the DC source is greater than a preset voltage.

6. The battery voltage limiting protection circuit according to claim 1, characterized in that, The control chip is used to detect the voltage of the DC source and turn it off when the voltage of the DC source is less than or equal to a preset voltage.

7. A switching power supply, characterized in that, Includes the battery voltage limiting protection circuit as described in any one of claims 1 to 6.

8. An AC / DC power supply system, characterized in that, It includes an AC power source, a DC power source, a battery voltage limiting protection circuit as described in any one of claims 1 to 6, and a load.

9. A battery protection method, characterized in that, The method, applicable to AC / DC power supply systems, includes: detecting the voltage of a DC source; turning off a control chip when the voltage of the DC source is less than or equal to a preset voltage; controlling a branch load unit to conduct through a branch control unit, so that a preset load is connected across a first capacitor; wherein the first capacitor is used to supply power to the control chip, and the shunt of the preset load prevents the control chip from restarting.

10. The battery protection method according to claim 9, characterized in that, The branch control unit includes a first resistor and a fourth capacitor, wherein the capacitance of the fourth capacitor is greater than the capacitance of the first capacitor; the method further includes: after the control chip is started, controlling the branch load unit to conduct by charging the first resistor and the fourth capacitor.

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