Short-circuit protection circuit and battery protection board
By designing a combination of discharge MOS tube, protection MOS tube and voltage divider resistor in the short-circuit protection circuit, the problem of high voltage and large loss when the MOSFET tube is turned off is solved, and the effects of fast shutdown and low loss are achieved.
Patent Information
- Application Number
- CN202421769168.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-24
- Publication Date
- 2025-05-30
- Estimated Expiration
- 2034-07-24
AI Technical Summary
In the prior art, the voltage of the MOSFET tube is high when it is turned off, resulting in a large shutdown loss.
A short circuit protection circuit is designed, including a discharge MOS tube, a protection MOS tube and a first voltage divider resistor. By connecting the source of the protection MOS tube to the positive electrode of the output end of the lithium battery, and connecting the gate of the protection MOS tube to the drain of the discharge MOS tube, the first voltage divider resistor is connected in series between the gate of the protection MOS tube and the drain of the discharge MOS tube, so as to achieve rapid shutdown.
Through this design, the discharge MOS tube is quickly turned off, the response speed is fast, the shutdown loss is smaller, and the circuit structure is simple and the cost is low.
Smart Images
Figure CN222928090U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of lithium batteries, in particular to a short - circuit protection circuit and a battery protection board. Background Art
[0002] On a lithium - battery protection board, a MOSFET (Metal - Oxide - Semiconductor Field - Effect Transistor) is commonly used as a switch to control the turn - on and turn - off of the power supply; the MOSFET is designed with a fast - turn - off function. This design can quickly cut off the current when a short - circuit or other abnormal conditions are detected, thereby protecting the device from damage; the fast - turn - off mechanism can be triggered by detecting changes in current or voltage. Once a short - circuit or other abnormal conditions are detected, the MOSFET will be quickly turned off to cut off the main current path to avoid further damage to the protection board.
[0003] When the MOSFET is turned off, the voltage is usually higher than when it is turned on, and the loss generated during turn - off is relatively large. Therefore, it is necessary to design a short - circuit protection circuit and a battery protection board to make the circuit turn - off faster and the loss generated during turn - off smaller. Summary of the Utility Model
[0004] The technical problem to be solved by the embodiments of the utility model is to provide a short - circuit protection circuit and a battery protection board to solve the problem that when the MOSFET is turned off in the prior art, the voltage is higher than when it is turned on, and the loss generated during turn - off is relatively large.
[0005] The utility model discloses a short - circuit protection circuit, and the solution lies in that it includes: a discharge MOS transistor, a protection MOS transistor, and a first voltage - dividing resistor. The drain of the discharge MOS transistor is connected to the positive electrode of the lithium battery. The source of the discharge MOS transistor and the source of the protection MOS transistor are both connected to the positive electrode of the output end of the lithium battery. The gate of the protection MOS transistor is connected to the drain of the discharge MOS transistor. The first voltage - dividing resistor is connected in series between the gate of the protection MOS transistor and the drain of the discharge MOS transistor. The drain of the protection MOS transistor and the gate of the discharge MOS transistor are both connected to an external controller.
[0006] Optionally, a first capacitor and a second capacitor are further connected in series between the gate of the protection MOS transistor and the drain of the discharge MOS transistor.
[0007] Optionally, a zener diode is connected in parallel between the gate and the source of the protection MOS transistor.
[0008] Optionally, a second voltage - dividing resistor is further connected in parallel between the gate and the source of the protection MOS transistor.
[0009] Optionally, a driving resistor is connected in series on the gate of the discharge MOS transistor.
[0010] Optionally, a variable resistor is connected in series to the drain of the protection MOS transistor.
[0011] Optionally, the protection MOS transistor is an N-channel MOS transistor.
[0012] Optionally, a filter module is provided between the source of the discharge MOS transistor and the positive pole of the output terminal of the lithium battery.
[0013] Optionally, a protection resistor is also provided between the source of the discharge MOS transistor and the positive pole of the output terminal of the lithium battery.
[0014] To solve the problems existing in the prior art, the present utility model further provides a battery protection board, which includes a circuit board provided with a charge and discharge controller and a short-circuit protection circuit as described in any one of the above.
[0015] Compared with the prior art, the beneficial effects of the short-circuit protection circuit provided by the embodiment of the present utility model are as follows: By providing a voltage-dividing resistor and a protection MOS transistor on the discharge MOS transistor, and connecting the gate of the protection MOS transistor to the drain of the discharge MOS transistor, the first voltage-dividing resistor is connected in series between the gate of the protection MOS transistor and the drain of the discharge MOS transistor. When the positive and negative poles of the output terminal of the lithium battery are short-circuited, the source voltage of the protection MOS transistor is 0V, the voltage between the gate and the source of the protection MOS transistor is a positive voltage, and the protection MOS transistor is turned on; the drain voltage of the protection MOS transistor and the gate voltage of the discharge MOS transistor are both 0V, and the voltage between the gate and the source of the discharge MOS transistor is a negative voltage, realizing the rapid turn-off of the discharge MOS transistor, with a fast response speed, smaller turn-off loss, and a simple circuit structure and low cost. Description of the Drawings
[0016] The technical solution of the present utility model will be further described in detail below with reference to the drawings and embodiments. In the drawings:
[0017] Figure 1 is the circuit diagram of the short-circuit protection circuit provided by the embodiment of the present utility model. Detailed Embodiments
[0018] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. Now, with reference to the drawings, the preferred embodiments of the present utility model will be described in detail.
[0019] As Figure 1 shown, the present utility model provides a specific embodiment of a short-circuit protection circuit.
[0020] A short-circuit protection circuit, referring to Figure 1, the short - circuit protection circuit includes a discharge MOS transistor M1, a protection MOS transistor M2, and a first voltage - dividing resistor R1. The drain of the discharge MOS transistor M1 is connected to the positive electrode B+ of the lithium battery. The source of the discharge MOS transistor M1 and the source of the protection MOS transistor M2 are both connected to the positive electrode P+ of the lithium - battery output terminal. The gate of the protection MOS transistor M2 is connected to the drain of the discharge MOS transistor M1. The first voltage - dividing resistor R1 is connected in series between the gate of the protection MOS transistor M2 and the drain of the discharge MOS transistor M1. The drain of the protection MOS transistor M2 and the gate of the discharge MOS transistor M1 are both connected to an external controller.
[0021] Specifically, referring to Figure 1 , the discharge MOS transistor M1 is used for overload protection. When there is an overload or short - circuit in the circuit, the discharge MOS transistor M1 can be quickly turned off to divert excessive current to the ground, protecting other circuit components from damage. Since the quick - turn - off mechanism of the discharge MOS transistor M1 is generally triggered by detecting changes in current or voltage, once a short - circuit or other abnormal conditions are detected, the discharge MOS transistor M1 will quickly turn off to cut off the current path, thus preventing further damage to the protection board. When the discharge MOS transistor M1 turns off, the voltage is usually higher than when it is conducting, resulting in relatively large losses when the discharge MOS transistor M1 turns off.
[0022] In the short - circuit protection circuit of this embodiment, a protection MOS transistor M2 and a first voltage - dividing resistor R1 are also provided. By connecting the source of the protection MOS transistor M2 to the positive electrode P+ of the lithium - battery output terminal, connecting the gate of the protection MOS transistor M2 to the drain of the discharge MOS transistor M1, and setting the first voltage - dividing resistor R1 between the gate of the protection MOS transistor M2 and the drain of the discharge MOS transistor M1, the voltage at the drain of the discharge MOS transistor M1 is limited in current and divided in voltage through the first voltage - dividing resistor R1 and then enters the gate of the protection MOS transistor M2.
[0023] When the positive electrode P+ and the negative electrode of the lithium - battery output terminal are in a normal working state, the voltage of the positive electrode P+ of the lithium - battery output terminal is a high voltage, that is, the source of the protection MOS transistor M2 is at a high voltage. At this time, the voltage between the gate and the source of the protection MOS transistor M2 is a negative voltage, and the protection MOS transistor M2 is not conducting.
[0024] When the positive electrode P+ of the lithium battery output terminal and the negative electrode of the lithium battery output terminal are short-circuited instantaneously, the positive electrode P+ of the lithium battery output terminal is equivalent to being grounded, that is, the source voltage of the protection MOS transistor M2 is 0V. At this time, the voltage between the gate of the protection MOS transistor M2 and the source of the protection MOS transistor M2 is a positive voltage, and the protection MOS transistor M2 is turned on; when it is turned on, the drain voltage of the protection MOS transistor M2 becomes 0V. At this time, the gate voltage of the discharge MOS transistor M1 becomes 0V, and the voltage between the gate of the discharge MOS transistor M1 and the source of the discharge MOS transistor M1 is a negative voltage, and the discharge MOS transistor M1 is quickly turned off.
[0025] In this embodiment, by providing a voltage-dividing resistor and a protection MOS transistor on the discharge MOS transistor, and connecting the gate of the protection MOS transistor to the drain of the discharge MOS transistor, the first voltage-dividing resistor is connected in series between the gate of the protection MOS transistor and the drain of the discharge MOS transistor. When the positive and negative electrodes of the lithium battery output terminal are short-circuited, the source voltage of the protection MOS transistor is 0V, and the voltage between the gate of the protection MOS transistor and the source of the protection MOS transistor is a positive voltage, and the protection MOS transistor is turned on; the drain of the protection MOS transistor and the gate voltage of the discharge MOS transistor are both 0V, and the voltage between the gate of the discharge MOS transistor and the source of the discharge MOS transistor is a negative voltage, realizing the rapid turn-off of the discharge MOS transistor, which not only has a fast response speed but also makes the turn-off loss smaller.
[0026] In one of the embodiments, referring to Figure 1 , a first capacitor C1 and a second capacitor C2 are also connected in series between the gate of the protection MOS transistor M2 and the drain of the discharge MOS transistor M1.
[0027] Specifically, referring to Figure 1 , one end of the first capacitor C1 is connected to one end of the first voltage-dividing resistor R1, the other end of the first capacitor C1 is connected to one end of the second capacitor C2, the other end of the second capacitor C2 is connected to the gate of the protection MOS transistor M2, and the drain voltage of the discharge MOS transistor M1 passes through the first voltage-dividing resistor R1 for voltage division first, and then passes through the first capacitor C1 and the second capacitor C2 to enter the gate of the protection MOS transistor M2. The functions of the first capacitor C1 and the second capacitor C2 are to utilize the characteristic that the capacitor is equivalent to being disconnected when it is full, to prevent the discharge MOS transistor M1 from never being able to turn on after a short circuit.
[0028] In one of the embodiments, referring to Figure 1 , a zener diode Z1 is connected in parallel between the gate and the source of the protection MOS transistor M2.
[0029] Specifically, referring to Figure 1, the positive electrode of the voltage stabilizing diode Z1 is connected between the source electrode of the protection MOS transistor M2 and the positive electrode P+ of the lithium battery output terminal. The negative electrode of the voltage stabilizing diode Z1 is connected to the gate of the protection MOS transistor M2. The voltage stabilizing diode Z1 is a diode with a breakdown voltage of 15V. The voltage stabilizing diode Z1 can operate under the reverse breakdown voltage. Once the voltage exceeds its rated breakdown voltage, the stabilizing diode will conduct to keep the voltage in the circuit at a stable level. In this embodiment, the voltage stabilizing diode Z1 is used to limit the voltage fluctuation in the circuit to ensure that the key components in the circuit are not affected by excessive voltage.
[0030] In one embodiment, referring to Figure 1 , a second voltage dividing resistor R2 is also connected in parallel between the gate and the source of the protection MOS transistor M2.
[0031] Specifically, referring to Figure 1 , one end of the second voltage dividing resistor R2 is connected between the source electrode of the protection MOS transistor M2 and the positive electrode P+ of the lithium battery output terminal, and the other end of the second voltage dividing resistor R2 is connected to the gate of the protection MOS transistor M2. The second voltage dividing resistor R2 is used to divide the voltage between the gate and the source of the protection MOS transistor M2.
[0032] In one embodiment, referring to Figure 1 , a variable resistor R3 is connected in series on the drain of the protection MOS transistor M2, and a driving resistor R4 is connected in series on the gate of the discharge MOS transistor M1.
[0033] Specifically, referring to Figure 1 , when the positive electrode P+ and the negative electrode of the lithium battery output terminal are short-circuited instantaneously, the positive electrode P+ of the lithium battery output terminal is equivalent to being grounded, that is, the source voltage of the protection MOS transistor M2 is 0V. At this time, the voltage between the gate and the source of the protection MOS transistor M2 is a positive voltage, and the protection MOS transistor M2 conducts; when it conducts, the drain voltage of the protection MOS transistor M2 becomes 0V. This voltage passes through the variable resistor R3 and the driving resistor R4, making the gate voltage of the discharge MOS transistor M1 become 0V. The voltage between the gate and the source of the discharge MOS transistor M1 is a negative voltage, and the discharge MOS transistor M1 is quickly turned off.
[0034] In one embodiment, the protection MOS transistor M2 is an N-channel MOS transistor.
[0035] Specifically, an N-channel MOS transistor is a metal-oxide-semiconductor field-effect transistor, where the conductive carriers are electrons. When a positive voltage is applied to the gate, the electrons in the N-type channel under the gate are attracted to the vicinity of the gate, forming a conductive channel to turn on the protection MOS transistor M2. When the gate voltage is 0 or a negative voltage, the conductive channel disappears, turning off the protection MOS transistor M2 so that it does not conduct electricity.
[0036] In one embodiment, referring to Figure 1 , a filter module 100 is provided between the source of the discharge MOS transistor M1 and the positive electrode P+ of the lithium battery output terminal, and a protection resistor R5 is also provided between the source of the discharge MOS transistor M1 and the positive electrode P+ of the lithium battery output terminal.
[0037] The present utility model also provides a specific embodiment of a battery protection board.
[0038] A battery protection board, which includes a circuit board. An charge and discharge controller and the short-circuit protection circuit as described in any one of the above are provided on the circuit board. In the short-circuit protection circuit, the drain of the protection MOS transistor M2 and the gate of the discharge MOS transistor M1 are both connected to the charge and discharge controller, and the charge and discharge controller is used to control the discharge MOS transistor M1 to turn on.
[0039] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present utility model and are not intended to limit it. For those skilled in the art, the technical solutions described in the above embodiments can be modified, or some of the technical features can be equivalently replaced; and all such modifications and replacements should fall within the protection scope of the appended claims of the present utility model.
Claims
1. A short circuit protection circuit, characterized in that: include: A discharge MOS tube, a protection MOS tube and a first voltage-dividing resistor, wherein the drain of the discharge MOS tube is connected to the positive electrode of the lithium battery, the source of the discharge MOS tube and the source of the protection MOS tube are both connected to the positive electrode of the output end of the lithium battery, the gate of the protection MOS tube is connected to the drain of the discharge MOS tube, the first voltage-dividing resistor is connected in series between the gate of the protection MOS tube and the drain of the discharge MOS tube, and the drain of the protection MOS tube and the gate of the discharge MOS tube are both connected to an external controller.
2. The short circuit protection circuit according to claim 1, characterized in that: A first capacitor and a second capacitor are connected in series between the gate of the protection MOS tube and the drain of the discharge MOS tube.
3. The short circuit protection circuit according to claim 1, characterized in that: A voltage stabilizing diode is connected in parallel between the gate and source of the protection MOS tube.
4. The short circuit protection circuit according to claim 3, characterized in that: A second voltage-dividing resistor is also connected in parallel between the gate and source of the protection MOS tube.
5. The short circuit protection circuit according to claim 1, characterized in that: A driving resistor is connected in series to the gate of the discharge MOS tube.
6. The short circuit protection circuit according to claim 1, characterized in that: An adjustable resistor is connected in series to the drain of the protection MOS tube.
7. The short circuit protection circuit according to claim 1, characterized in that: The protection MOS tube is an N-channel MOS tube.
8. The short circuit protection circuit according to claim 1, characterized in that: A filter module is arranged between the source electrode of the discharge MOS tube and the positive electrode of the output end of the lithium battery.
9. The short circuit protection circuit according to claim 8, characterized in that: A protective resistor is also arranged between the source electrode of the discharge MOS tube and the positive electrode of the output end of the lithium battery.
10. A battery protection board, characterized in that: It comprises a circuit board, on which a charge and discharge controller and a short-circuit protection circuit as claimed in any one of claims 1 to 9 are arranged.