Over / under voltage protection circuit and fttr device

Abstract

The utility model discloses a kind of overvoltage protection circuit and FTTR equipment, including the first resistance network for providing the battery module corresponding battery voltage division voltage to overvoltage protection circuit and the base of NPN triode;Overvoltage protection circuit is used to connect ground terminal, when battery voltage division voltage is greater than overvoltage protection threshold, first resistance network and ground terminal are turned on;The collector of NPN triode is connected with battery module, the emitter of NPN triode is connected with voltage output circuit, for when overvoltage protection circuit turns on first resistance network and ground terminal, and / or, when battery voltage division voltage is less than under-voltage protection threshold, enter off state;Voltage output circuit is connected with for connecting battery module, ground terminal and load, when NPN triode is in off state, disconnect battery module and load.This technical solution protects battery module by hardware circuit, there is no software delay, response speed is fast, and can simultaneously realize under-voltage and overvoltage protection, circuit structure is simple, and cost is relatively lower.

Description

Technical Field

[0001] This utility model relates to the field of electrical equipment technology, and in particular to an over / under voltage protection circuit and an FTTR device. Background Technology

[0002] FTTR (Fiber to the Room) equipment often uses rechargeable batteries as an auxiliary power source to ensure the continued operation of critical functions, such as network connectivity and connection failure alarms, during external power outages. However, battery voltage fluctuates during use and charging. For example, over-discharging can lead to excessively low voltage, severely damaging battery life or even causing permanent damage; overcharging can result in excessively high voltage, posing safety risks such as thermal runaway and fire, and potentially burning out the expensive FTTR main control chip. While existing complex Battery Management Systems (BMS) provide comprehensive protection, they are costly and have complex circuitry, making them unsuitable for FTTR equipment where cost and control logic simplicity are critical. Therefore, there is an urgent need for a simple, low-cost, fast-responding, and reliable circuit that can automatically cut off the power supply when the battery voltage is abnormal, protecting both the battery and the equipment itself. Utility Model Content

[0003] This utility model provides an over / under voltage protection circuit and an FTTR device to solve the problems of existing battery management systems being costly and complex, making them unsuitable for FTTR devices that have high requirements for cost and control logic simplicity.

[0004] An over / under voltage protection circuit includes a first resistor network, an overvoltage protection circuit, an NPN transistor, and a voltage output circuit. The first resistor network is used to connect the battery module, and is connected to the overvoltage protection circuit and the base of the NPN transistor, to provide the battery voltage corresponding to the battery module to the overvoltage protection circuit and the base of the NPN transistor; The overvoltage protection circuit is used to connect to the ground terminal, and when the battery voltage divider is greater than the overvoltage protection threshold, the first resistor network and the ground terminal are turned on. The collector of the NPN transistor is connected to the battery module, and the emitter of the NPN transistor is connected to the voltage output circuit. It is used to enter the shutdown state when the overvoltage protection circuit turns on the first resistor network and the ground terminal, and / or when the battery voltage is less than the undervoltage protection threshold. The voltage output circuit is used to connect the battery module, the ground terminal, and the load. When the NPN transistor is in the off state, it disconnects the battery module and the load.

[0005] Furthermore, the first resistor network includes a first resistor and a second resistor; The first end of the first resistor is connected to the battery module, and the second end of the first resistor is connected to the first end of the second resistor and the overvoltage protection circuit. The second end of the second resistor is connected to the base of the NPN transistor.

[0006] Furthermore, the overvoltage protection circuit includes a Zener diode; the cathode of the Zener diode is connected to the first resistor network, and the anode of the Zener diode is connected to the ground terminal.

[0007] Furthermore, the voltage output circuit includes a first voltage divider circuit and a PMOS transistor; The first terminal of the first voltage divider circuit is connected to the battery module, the second terminal of the first voltage divider circuit is connected to the ground terminal, and the third terminal of the first voltage divider circuit is connected to the emitter of the NPN transistor and the gate of the PMOS transistor. The source of the PMOS transistor is connected to the battery module, and the drain of the PMOS transistor is connected to the load. Furthermore, the first voltage divider circuit includes a third resistor and a fourth resistor; The third resistor and the fourth resistor are connected in series between the battery module and the ground terminal, and the connection node between the third resistor and the fourth resistor is the third terminal of the first voltage divider circuit.

[0008] Furthermore, the voltage output circuit also includes a fifth resistor; the first end of the fifth resistor is connected to the drain of the PMOS transistor, and the second end of the fifth resistor is connected to the ground terminal.

[0009] An FTTR device includes a battery module and the aforementioned over / under voltage protection circuit.

[0010] This utility model embodiment provides an over / under voltage protection circuit and an FTTR device. A first resistor network is used to connect the battery module, which is connected to the base of the overvoltage protection circuit and the NPN transistor. This network provides the battery voltage divider corresponding to the battery module to the base of the overvoltage protection circuit and the NPN transistor. The battery voltage of the battery module is detected by the battery voltage divider. When the battery voltage divider exceeds the overvoltage protection threshold, i.e., when the battery module is overvoltageed, the overvoltage protection circuit connects the first resistor network and the ground terminal, pulling the battery voltage down. The base potential of the NPN transistor is low, thereby controlling the NPN transistor to enter the off state. When the battery voltage is less than the undervoltage protection threshold, i.e. when the battery module is undervoltage, the NPN transistor enters the off state according to its own characteristics because the base voltage is too low. In the off state, the NPN transistor controls the voltage output circuit of the battery module and the load, thereby protecting the battery module through hardware circuit. There is no software delay, the response speed is fast, and it can simultaneously achieve undervoltage and overvoltage protection. The circuit structure is simple and the cost is low. Attached Figure Description

[0011] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments of this utility model will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram of an over / under voltage protection circuit in one embodiment of the present invention.

[0013] In the diagram: 1. First resistor network; 2. Overvoltage protection circuit; 3. NPN transistor; 4. Voltage output circuit; 41. First voltage divider circuit; 42. PMOS transistor. Detailed Implementation

[0014] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present utility model.

[0015] It should be understood that this invention can be embodied in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of this invention to those skilled in the art.

[0016] To fully understand this utility model, detailed structures and steps will be presented in the following description to illustrate the technical solution proposed by this utility model. Preferred embodiments of this utility model are described in detail below; however, in addition to these detailed descriptions, this utility model may have other embodiments.

[0017] This embodiment provides an over / under voltage protection circuit applied in an FTTR device, which includes a battery module and the over / under voltage protection circuit. The over / under voltage protection circuit is connected to the battery module and other loads in the FTTR device. When the external power supply to the FTTR device is interrupted, and the battery module experiences over / under voltage, the circuit disconnects the battery module and the loads to protect the safety of the FTTR device.

[0018] This embodiment provides an over / under voltage protection circuit, such as... Figure 1 As shown, the circuit includes a first resistor network 1, an overvoltage protection circuit 2, an NPN transistor 3, and a voltage output circuit 4. The first resistor network 1 is used to connect the battery module and is connected to the base of the overvoltage protection circuit 2 and the NPN transistor 3, providing the battery voltage corresponding to the battery module to the base of the overvoltage protection circuit 2 and the NPN transistor 3. The overvoltage protection circuit 2 is used to connect to the ground terminal, and when the battery voltage is greater than the overvoltage protection threshold, it turns on the first resistor network 1 and the ground terminal. The collector of the NPN transistor 3 is connected to the battery module, and the emitter of the NPN transistor 3 is connected to the voltage output circuit 4, which is used to enter the off state when the overvoltage protection circuit 2 turns on the first resistor network 1 and the ground terminal, and / or when the battery voltage is less than the undervoltage protection threshold. The voltage output circuit 4 is used to connect the battery module, the ground terminal, and the load, and disconnects the battery module and the load when the NPN transistor 3 is in the off state.

[0019] In this embodiment, a first resistor network 1 is used to connect the battery module, which is connected to the base of the overvoltage protection circuit 2 and the NPN transistor 3. This network provides the battery voltage corresponding to the battery module to the base of the overvoltage protection circuit 2 and the NPN transistor 3. The battery voltage of the battery module is detected by the battery voltage divider. When the battery voltage divider exceeds the overvoltage protection threshold (i.e., when the battery module is overvoltaged), the overvoltage protection circuit 2 connects the first resistor network 1 and the ground terminal, pulling down the NPN transistor. The base potential of transistor 3 is controlled to turn off the NPN transistor 3. When the battery voltage is less than the undervoltage protection threshold, i.e. when the battery module is undervoltage, the base voltage of NPN transistor 3 is too low, causing NPN transistor 3 to turn off according to its own characteristics. In the off state, NPN transistor 3 controls the voltage output circuit 4, which controls the battery module and the load, thereby protecting the battery module through hardware circuit. There is no software delay, the response speed is fast, and it can simultaneously achieve undervoltage and overvoltage protection. The circuit structure is simple and the cost is low.

[0020] In one embodiment, the first resistor network 1 includes a first resistor and a second resistor; the first end of the first resistor is connected to the battery module, the second end of the first resistor is connected to the first end of the second resistor and the overvoltage protection circuit 2; the second end of the second resistor is connected to the base of the NPN transistor 3.

[0021] In this embodiment, the overvoltage protection voltage point of the battery module can be determined through practical experience. Then, the overvoltage protection threshold of the overvoltage protection circuit 2 is determined. Based on the overvoltage protection voltage point and the overvoltage protection threshold, the resistance values ​​of the first resistor and the second resistor are determined. This ensures that when the battery voltage of the battery module reaches the overvoltage protection voltage point, the voltage at the voltage divider node between the first resistor and the second resistor is greater than the overvoltage protection threshold of the overvoltage protection circuit 2. Consequently, the overvoltage protection circuit 2 conducts the first resistor network 1 and the ground terminal, pulling down the base potential of the NPN transistor 3, thereby controlling the NPN transistor 3 to enter the off state. For example, if the overvoltage protection voltage point VBAT_ovp is 14V and the overvoltage protection threshold Vz is 5.1V, then according to the resistor voltage divider formula: Vz = VBAT_ovp * [ R2 / (R1 + R2) ] That is: 5.1V = 14V * [R2 / (R1 + R2)] Solving for R1 / R2, we get: R1 / R2 ≈ (14V / 5.1V) - 1 ≈ 1.745.

[0022] Where R1 is the resistance value of the first resistor and R2 is the resistance value of the second resistor, therefore, in specific implementation, the nominal values ​​R1 = 17.4kΩ and R2 = 10kΩ can be selected.

[0023] In one embodiment, the overvoltage protection circuit 2 includes a Zener diode; the cathode of the Zener diode is connected to the first resistor network 1, and the anode of the Zener diode is connected to the ground terminal.

[0024] For example, the Zener diode is selected as BZT52C5V1S, with a Zener voltage of 5.1V, and is packaged in an SOD-123 package. When the voltage at the sampling point of the first resistor network 1 exceeds 5.1V, the Zener diode breaks down and conducts.

[0025] In this embodiment, the breakdown characteristics of the Zener diode are used to achieve precise overvoltage protection, which can quickly respond when the voltage of the battery module is abnormal and protect the battery module.

[0026] In one embodiment, the voltage output circuit 4 includes a first voltage divider circuit 41 and a PMOS transistor 42; the first terminal of the first voltage divider circuit 41 is connected to the battery module, the second terminal of the first voltage divider circuit 41 is connected to the ground terminal, and the third terminal of the first voltage divider circuit 41 is connected to the emitter of the NPN transistor 3 and the gate of the PMOS transistor 42; the source of the PMOS transistor 42 is connected to the battery module, and the drain of the PMOS transistor 42 is connected to the load.

[0027] In this embodiment, the main switch of the battery module discharge path is implemented by PMOS transistor 42, which has low on-resistance, low power consumption, and fast switching speed.

[0028] In one embodiment, the first voltage divider circuit 41 includes a third resistor and a fourth resistor; the third resistor and the fourth resistor are connected in series between the battery module and the ground terminal, and the connection node between the third resistor and the fourth resistor is the third terminal of the first voltage divider circuit 41.

[0029] In this embodiment, the driving voltage is provided to the gate of the PMOS transistor 42 through the third resistor and the fourth resistor, which has a simple structure and low cost.

[0030] In one embodiment, the voltage output circuit 4 further includes a fifth resistor; the first end of the fifth resistor is connected to the drain of the PMOS transistor 42, and the second end of the fifth resistor is connected to the ground terminal.

[0031] In this embodiment, the first end of the fifth resistor is connected to the drain of the PMOS transistor 42, and the second end of the fifth resistor is connected to the ground terminal to ensure the stability of the output voltage.

[0032] As an example, the overvoltage protection threshold of the battery module is 14V, and the undervoltage protection threshold is 10V. The working principle of the overvoltage and undervoltage protection circuit in the above embodiment is as follows: When the battery voltage of the battery module is between 10V and 14V, the voltage divided by the first and second resistors is less than the voltage regulation value of the Zener diode and greater than the conduction threshold of NPN transistor 3. The Zener diode is cut off, and NPN transistor 3 is turned on. Since NPN transistor 3 is turned on, it is equivalent to connecting a very small on-resistance in parallel with the third resistor, thereby pulling the voltage at the voltage divider point of the third and fourth resistors down to a level close to ground potential, thus controlling PMOS transistor 42 to turn on, and the battery module normally supplies power to the load.

[0033] When the battery voltage of the battery module exceeds 14V, the Zener diode breaks down and conducts, clamping the base voltage of NPN transistor 3 and shunting most of the base current, causing NPN transistor 3 to turn off. After NPN transistor 3 turns off, it disconnects from the third resistor. At this time, the gate voltage of PMOS transistor 42 is determined by the voltage division of the third and fourth resistors. The third and fourth resistors increase significantly, and the gate voltage of PMOS transistor 42 increases, making the gate-source voltage of PMOS transistor 42 insufficient to turn it on, thus stopping the battery module from discharging.

[0034] When the battery voltage of the battery module is less than 10V, the voltage divider voltage of the first resistor and the second resistor decreases as the battery voltage of the battery module decreases. The Zener diode remains off. Because the battery voltage of the battery module is too low, the base-emitter voltage of NPN transistor 3 is less than 0.7V, which cannot maintain the conduction of NPN transistor 3. Therefore, NPN transistor 3 is off, and PMOS transistor 42 cannot be turned on due to insufficient gate drive voltage, thus cutting off the power supply.

[0035] This embodiment provides an FTTR device, including a battery module and the over / under voltage protection circuit described above.

[0036] In this embodiment, when the battery module voltage is abnormal, the protection circuit automatically cuts off the power supply path to extend the battery life.

[0037] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model, and should all be included within the protection scope of this utility model.

Claims

1. An over / under voltage protection circuit, characterized in that, It includes a first resistor network, an overvoltage protection circuit, an NPN transistor, and a voltage output circuit; The first resistor network is used to connect the battery module, and is connected to the overvoltage protection circuit and the base of the NPN transistor, to provide the battery voltage corresponding to the battery module to the overvoltage protection circuit and the base of the NPN transistor; The overvoltage protection circuit is used to connect to the ground terminal, and when the battery voltage divider is greater than the overvoltage protection threshold, the first resistor network and the ground terminal are turned on. The collector of the NPN transistor is connected to the battery module, and the emitter of the NPN transistor is connected to the voltage output circuit. It is used to enter the shutdown state when the overvoltage protection circuit turns on the first resistor network and the ground terminal, and / or when the battery voltage is less than the undervoltage protection threshold. The voltage output circuit is used to connect the battery module, the ground terminal, and the load. When the NPN transistor is in the off state, it disconnects the battery module and the load.

2. The over / under voltage protection circuit according to claim 1, characterized in that, The first resistor network includes a first resistor and a second resistor; The first end of the first resistor is connected to the battery module, and the second end of the first resistor is connected to the first end of the second resistor and the overvoltage protection circuit. The second end of the second resistor is connected to the base of the NPN transistor.

3. The over / under voltage protection circuit according to claim 1, characterized in that, The overvoltage protection circuit includes a Zener diode; the cathode of the Zener diode is connected to the first resistor network, and the anode of the Zener diode is connected to the ground terminal.

4. The over / under voltage protection circuit according to claim 1, characterized in that, The voltage output circuit includes a first voltage divider circuit and a PMOS transistor; The first terminal of the first voltage divider circuit is connected to the battery module, the second terminal of the first voltage divider circuit is connected to the ground terminal, and the third terminal of the first voltage divider circuit is connected to the emitter of the NPN transistor and the gate of the PMOS transistor. The source of the PMOS transistor is connected to the battery module, and the drain of the PMOS transistor is connected to the load.

5. The over / under voltage protection circuit according to claim 4, characterized in that, The first voltage divider circuit includes a third resistor and a fourth resistor; The third resistor and the fourth resistor are connected in series between the battery module and the ground terminal, and the connection node between the third resistor and the fourth resistor is the third terminal of the first voltage divider circuit.

6. The over / under voltage protection circuit according to claim 4, characterized in that, The voltage output circuit further includes a fifth resistor; the first end of the fifth resistor is connected to the drain of the PMOS transistor, and the second end of the fifth resistor is connected to the ground terminal.

7. An FTTR device, characterized in that, It includes a battery module and an over / under voltage protection circuit as described in any one of claims 1 to 6.

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