A battery over-discharge protection circuit

Abstract

The invention discloses a battery over-discharge protection circuit, comprising: a first diode, a second diode, a third diode, a comparison circuit, a switch circuit and a first switch, wherein the first diode is located between a power input terminal and a power output terminal of a device, the third diode is connected between the first terminal of the comparison circuit and the power input terminal of the device, the second terminal of the comparison circuit and the power output terminal of the device are connected with the second diode, the third terminal of the comparison circuit is connected with the first terminal of the switch circuit, the second terminal of the switch circuit is connected to the output terminal of the battery through the first switch, the third terminal of the switch circuit is connected to the power output terminal of the device after passing through the second diode, and the comparison circuit controls the switch circuit to disconnect after determining that the voltage of the power input terminal is less than a preset voltage threshold. The comparison circuit compares the voltage of the power input terminal to achieve the effect of triggering battery discharge and over-discharge detection, avoids excessive discharge of the battery, reduces battery loss, and improves the service life of the battery.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of analog electronic technology, and in particular to a battery over-discharge protection circuit. Background Art

[0002] Batteries are widely used in consumer products, communication equipment, UPS power supplies and other fields, and the methods of use are different in different application scenarios. In the circuit, MOS tubes or relays are usually used as battery switches. This switch can be controlled by a single-chip microcomputer or other control circuit to protect the battery. Most batteries integrate charge and discharge protection circuits. The circuit disconnects the battery switch only when the battery is fully charged or the battery is basically discharged to protect the battery. However, in actual applications, it is necessary to add a switch circuit outside the battery to ensure that the battery can be turned on or off at any time. During the transportation of the battery, due to misoperation of environmental factors such as vibration, the battery may enter a discharge state, causing dangerous situations such as circuit heating and sparks. Therefore, additional battery switch circuits are also added to the equipment using the battery. At present, most battery protection uses integrated chips and relay circuits. These methods have problems such as high circuit cost and long switch on and off time. Summary of the invention

[0003] The embodiment of the present invention provides a battery over-discharge protection circuit, which is used to solve the problem that the battery is discharged completely due to mistaken switching during transportation.

[0004] An embodiment of the present invention provides a battery over-discharge protection circuit, comprising: a first diode, a second diode, a third diode, a comparison circuit, a switch circuit and a first switch;

[0005] The first diode is located between the power input terminal and the power output terminal of the device;

[0006] The third diode is connected between the first end of the comparison circuit and the power input end of the device, the second diode is connected between the second end of the comparison circuit and the power output end of the device, and the third end of the comparison circuit is connected to the first end of the switch circuit;

[0007] The second end of the switch circuit is connected to the output end of the battery through the first switch, and the third end of the switch circuit is connected to the power output end of the device after passing through the second diode;

[0008] The comparison circuit controls the switch circuit to be disconnected after determining that the voltage at the power input terminal is less than a preset voltage threshold.

[0009] The above technical solution can trigger battery discharge and over-discharge detection by comparing the voltage at the power input terminal through the comparison circuit, thereby avoiding excessive discharge of the battery, reducing battery loss, and increasing the service life of the battery.

[0010] Optionally, the first end of the first diode is connected to the power supply output terminal, and the second end of the first diode is connected to the power supply input terminal; the first end of the second diode is connected to the power supply output terminal, and the second end of the second diode is connected to the second end of the comparison circuit; the first end of the third diode is connected to the first end of the comparison circuit, and the second end of the third diode is connected to the power supply input terminal.

[0011] Optionally, the comparison circuit includes a first resistor, a second resistor, a third resistor and an adjustable voltage source;

[0012] The first end of the first resistor is the second end of the comparison circuit, the second end of the first resistor, the second end of the second resistor and the second end of the third resistor are respectively connected to the second end of the adjustable voltage-stabilizing source, the first end of the second resistor is the first end of the comparison circuit, the first end of the third resistor and the third end of the adjustable voltage-stabilizing source are respectively grounded, and the first end of the adjustable voltage-stabilizing source is the third end of the comparison circuit.

[0013] Optionally, the comparison circuit further includes a control circuit;

[0014] The control circuit includes a triode, a fourth resistor and a fifth resistor;

[0015] The first end of the fourth resistor and the first end of the fifth resistor are connected to the control pin of the control chip of the device, the second end of the fourth resistor is connected to the first end of the transistor, the second end of the fifth resistor is connected to the second end of the transistor and then grounded, and the third end of the transistor is connected to the second end of the second resistor.

[0016] Optionally, the transistor is an NPN transistor.

[0017] Optionally, the adjustable voltage stabilizing source is a TL431 adjustable voltage stabilizing source.

[0018] Optionally, the switch circuit includes a MOS tube, a sixth resistor and a seventh resistor;

[0019] The first end of the seventh resistor is the first end of the switch circuit, the second end of the seventh resistor and the second end of the sixth resistor are respectively connected to the first end of the MOS tube, the first end of the sixth resistor is connected to the third end of the MOS tube and serves as the third end of the switch circuit, and the second end of the MOS tube is the second end of the switch circuit.

[0020] Optionally, the MOS tube is a PMOS tube.

[0021] Correspondingly, an embodiment of the present invention further provides a communication device, comprising the above-mentioned battery over-discharge protection circuit.

[0022] The above embodiment shows that a battery over-discharge protection circuit includes: a first diode, a second diode, a third diode, a comparison circuit, a switch circuit and a first switch, the first diode is located between the power input terminal and the power output terminal of the device, the third diode is connected between the first end of the comparison circuit and the power input terminal of the device, the second end of the comparison circuit and the power output terminal of the device are connected with the second diode, the third end of the comparison circuit is connected to the first end of the switch circuit, the second end of the switch circuit is connected to the output terminal of the battery through the first switch, the third end of the switch circuit is connected to the power output terminal of the device after passing through the second diode, and the comparison circuit controls the switch circuit to disconnect after determining that the voltage of the power input terminal is less than the preset voltage threshold. By comparing the voltage of the power input terminal through the comparison circuit, the effect of triggering battery discharge and over-discharge detection can be achieved, which avoids excessive discharge of the battery, reduces battery loss, and improves the service life of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 A schematic diagram of the structure of a battery over-discharge protection circuit provided by an embodiment of the present invention;

[0025] Figure 2 A schematic diagram of the structure of a comparison circuit provided by an embodiment of the present invention;

[0026] Figure 3 A schematic diagram of the structure of another comparison circuit provided by an embodiment of the present invention;

[0027] Figure 4 A schematic diagram of the structure of a switch circuit provided by an embodiment of the present invention;

[0028] Figure 5 A schematic structural diagram of a battery over-discharge protection circuit provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Figure 1 The structure of a battery over-discharge protection circuit provided by an embodiment of the present invention is exemplarily shown. Figure 1 As shown, the battery over-discharge protection circuit may include a first diode 100 , a second diode 200 , a third diode 300 , a comparison circuit 400 , a switch circuit 500 and a first switch 600 .

[0031] Among them, the first diode 100 is located between the power input terminal VIN and the power output terminal VOUT of the device. A third diode 300 is connected between the first end 410 of the comparison circuit 400 and the power input terminal VIN of the device, a second diode 200 is connected between the second end 420 of the comparison circuit 400 and the power output terminal VOUT of the device, and a third end 430 of the comparison circuit 400 is connected to the first end 510 of the switch circuit 500. The second end 520 of the switch circuit 500 is connected to the power output terminal VOUT of the device after passing through the second diode 200, and the third end 530 of the switch circuit 500 is connected to the output terminal of the battery through the first switch 600. After determining that the voltage of the power input terminal VIN is less than the preset voltage threshold, the comparison circuit 400 controls the switch circuit 500 to disconnect. The preset voltage threshold can be set based on experience.

[0032] The connection relationship of the above three diodes can be: the first end 110 of the first diode 100 is connected to the power output terminal VOUT, and the second end 120 of the first diode 100 is connected to the power input terminal VIN; the first end 210 of the second diode 200 is connected to the power output terminal VOUT, and the second end 220 of the second diode 200 is connected to the second end 420 of the comparison circuit 400; the first end 310 of the third diode 300 is connected to the first end 410 of the comparison circuit 400, and the second end 320 of the third diode 300 is connected to the power input terminal VIN.

[0033] Figure 2 Shown above Figure 1The structure of the comparison circuit 400 in FIG. 4 may include a first resistor 440, a second resistor 450, a third resistor 460 and an adjustable voltage-stabilizing source 470. The first end 441 of the first resistor 440 is the second end 420 of the comparison circuit 400, the second end 442 of the first resistor 440, the second end 452 of the second resistor 450 and the second end 462 of the third resistor 460 are respectively connected to the second end 472 of the adjustable voltage-stabilizing source 470, the first end 451 of the second resistor 450 is the first end 410 of the comparison circuit 400, the first end 461 of the third resistor 460 and the third end 473 of the adjustable voltage-stabilizing source 470 are respectively grounded, and the first end 471 of the adjustable voltage-stabilizing source 470 is the third end 410 of the comparison circuit 400.

[0034] In order to further prevent the battery from over-discharging, the comparison circuit 400 may further include a control circuit 700, such as Figure 3 As shown in the structure, the control circuit 700 may include a transistor 710, a fourth resistor 720 and a fifth resistor 730. The first end 721 of the fourth resistor 720 and the first end 731 of the fifth resistor 730 are connected to the control pin of the control chip of the device, the second end 722 of the fourth resistor 720 is connected to the first end 711 of the transistor 710, the second end 732 of the fifth resistor 730 is connected to the second end 712 of the transistor 710 and then grounded, and the third end 713 of the transistor 710 is connected to the second end 452 of the second resistor 450.

[0035] Optional, Figure 4 The above is exemplarily shown Figure 1 The structure of the switch circuit 500 in FIG. 5 may include a MOS transistor 540, a sixth resistor 550, and a seventh resistor 560. The first end 561 of the seventh resistor 560 is the first end 510 of the switch circuit 500, the second end 562 of the seventh resistor 560 and the second end 552 of the sixth resistor 550 are respectively connected to the first end 541 of the MOS transistor 540, the first end 551 of the sixth resistor 550 is connected to the third end 543 of the MOS transistor 540 as the third end 530 of the switch circuit 500, and the second end 542 of the MOS transistor 540 is the second end 520 of the switch circuit 500.

[0036] It should be noted that the above-mentioned transistor 710 can be an NPN transistor, the above-mentioned adjustable voltage regulator 470 can be a TL431 adjustable voltage regulator, and the above-mentioned MOS tube 540 can be a PMOS tube, that is, a P-type MOS tube. The embodiment of the present invention is only an example and is not specifically limited to this. In actual applications, similar devices can be used for replacement.

[0037] Based on the structure of the battery over-discharge protection circuit, when the voltage of the second end 472 of the adjustable voltage-stabilizing source 470 is greater than 2.5V, the voltage of the first end 471 is 2.5V; when the voltage of the second end 472 of the adjustable voltage-stabilizing source 470 is less than 2.5V, the first end 471 does not absorb current, and the voltage of the first end 471 is the battery voltage. In engineering applications, the first switch 600 is always closed. When the power input terminal VIN is powered on, the second resistor 450 and the third resistor 460 form a voltage divider circuit, and the trigger voltage VT of the power input terminal VIN is calculated to be 2.5 / the third resistor 460*(the second resistor 450+the third resistor 460). After the voltage of the power input terminal VIN is greater than VT, the first terminal 471 of the adjustable voltage regulator 470 outputs 2.5V, so that the voltage difference Ugs of the MOS tube 540 is (VB-2.5) / (the sixth resistor 550+the seventh resistor 560)*the sixth resistor 550. The battery voltage is set to VB, and the MOS tube 540 is turned on. At this time, the first resistor 440, the second resistor 450, and the third resistor 460 form a voltage divider circuit, which will increase the potential of the second terminal 472 of the adjustable voltage regulator 470, and the output of the first terminal 471 of the adjustable voltage regulator 470 remains unchanged. After the power input terminal VIN loses power, the voltage gradually decreases. When the voltage of the power input terminal VIN is less than the battery voltage VB, the output of the power output terminal VOUT is provided by the battery. When the voltage of the power input terminal VIN is less than 2.5V, the function of the third diode 300 is reflected. At this time, the third diode 300 is in the cut-off state, the second resistor 450 fails, and the first resistor 440 and the second resistor 450 form a voltage divider circuit, so the discharge cut-off voltage VC = 2.5 / third resistor 460*(first resistor 440+third resistor 460). When the battery voltage VB is less than VC, the first end 471 of the adjustable voltage regulator 470 does not absorb current, the Ugs of the MOS tube 540 is 0V, and the MOS tube 540 is disconnected, thereby disconnecting the power supply to the power output terminal VOUT, thereby realizing the over-discharge protection function.

[0038] Furthermore, when the voltage at the power input terminal VIN = 0V, the first switch 600 is closed, the second terminal 472 of the adjustable voltage regulator 470 inputs 0V, the first terminal 471 of the adjustable voltage regulator 470 does not absorb current, the Ugs of the MOS tube 540 is 0V, the MOS tube 540 is turned off, and VOUT will not have current output, thereby realizing the function of preventing mis-switching.

[0039] Furthermore, in specific Figure 3 After the structure of the control circuit 700 in the dotted line part, the battery over-discharge protection circuit also specifically turns off the battery power supply in advance, and the control signal can be sent by the control pin of the single-chip microcomputer of the device or the output pin of other control chips. The control signal can be a high level.

[0040] Based on the above embodiments, the structure of the battery over-discharge protection circuit will be described below through a specific structure. Figure 5 In the structure shown, the battery over-discharge protection circuit may include three diodes D1, D2, and D3, an adjustable voltage regulator TL431 (D4), an external switch K1, an NPN transistor K2, a PMOS tube K3, a battery B1, and seven resistors R1 to R7. It can also be said that it includes a diode D1 directly connected to the VIN network and the VOUT network, a diode D2 connected to the PMOS tube output and the VOUT network, a diode D3 connected to the VIN network and R2, an adjustable voltage regulator TL431 (D4), an external switch K1 connected to the device, an NPN transistor K2 for discharge control, a lithium battery discharge switch PMOS tube K3, an internal power supply battery B1, sampling resistors R1, R2, and R3, a current limiting resistor R4 of the transistor K2, a pull-down resistor R5 of the BAT_CTL network, and bias resistors R6 and R7.

[0041] During transportation, the VIN voltage of the battery over-discharge protection circuit is 0V. Whether K1 is open or closed, the battery power will not be consumed, and the VOUT voltage is always 0V, so the internal circuit will not work.

[0042] When the battery over-discharge protection circuit works normally, K1 is closed, the power network VIN is powered on, TL431 is triggered, and MOS tube K3 is turned on. Since VIN is greater than the battery voltage VB, diode D2 is turned off. When the system is powered off, the VIN network voltage becomes 0V, diodes D1 and D3 are turned off, D2 is turned on, and VOUT is powered by the battery. When the battery voltage drops to the predetermined value VC=2.5 / R3*(R1+R3), pin 1 of TL431 does not draw current, MOS tube Ugs is 0V, and MOS tube is disconnected, thereby disconnecting the power supply to VOUT.

[0043] The dotted circuit has the function of shutting down the battery power supply in advance. The BAT_CTL network can be directly connected to the control pin of the microcontroller or the output pin of other control chips. It is worth noting that the BAT_CTL network requires a low level when powered on, otherwise the power supply VIN input may be cut off and the power supply may not be able to be supplied. Of course, this part of the circuit can also be not installed. In this case, K3 will be disconnected only when the battery voltage reaches the expected value of the design.

[0044] Specifically, TL431 (D4) and resistors R1, R2, and R3 form a comparison circuit to achieve the effect of triggering battery discharge and over-discharge detection. R6, R7, and P-channel MOS form a battery discharge switch, which is controlled by the output of pin 1 of TL431. R6 and R7 form the bias of the MOS tube, and the appropriate resistance value is selected to adapt to the parameter requirements of different MOS tubes.

[0045] Furthermore, according to the parameter requirements of TL431, the input current of the second pin of TL431 can be ignored. When the voltage of the second pin of TL431 is greater than 2.5V, the output pin 1 is 2.5V. When the voltage of the second pin of TL431 is less than 2.5V, the output pin 1 does not absorb current, so it is the battery voltage. In engineering applications, K1 is always closed. When VIN is powered on, R2 and R3 divide the voltage, and calculate the trigger voltage of VIN VT = 2.5 / R3*(R2+R3). After VIN is greater than VT, TL431 outputs 2.5V, making the voltage difference of PMOS Ugs = (VB-2.5) / (R6+R7)*R6. The battery voltage is set to VB, and the PMOS tube is turned on. At this time, R1, R2, and R3 form a voltage divider network, which will increase the potential of the second pin of TL431, and the output of TL431 remains unchanged. After VIN loses power, the voltage gradually decreases. When VIN is less than the battery voltage VB, the output of VOUT is provided by the battery; when VIN is less than 2.5V, the role of D3 is reflected. At this time, D3 is in the cut-off state, R2 fails, and R1 and R2 form a voltage divider circuit, so the discharge cut-off voltage VC=2.5 / R3*(R1+R3). When the battery voltage is less than VC, pin 1 of TL431 does not absorb current, the MOS tube Ugs is 0V, the MOS tube is disconnected, and the power supply to VOUT is disconnected, thus realizing the over-discharge protection function.

[0046] Furthermore, when the VIN voltage = 0V, the switch K1 is closed, the input of pin 2 of TL431 is 0V, the pin 1 of TL431 does not absorb current, the MOS tube Ugs is 0V, the MOS tube is turned off, and there is no current output from VOUT, thereby realizing the function of preventing false switching.

[0047] Compared with the prior art, the battery over-discharge protection circuit provided by the embodiment of the present invention has the following advantages: it avoids the battery from being accidentally switched on and off during transportation; it controls the battery to work at a specific voltage; and it can control the battery switch to avoid excessive discharge of the battery. The embodiment of the present invention reduces battery loss and increases the battery life. The battery over-discharge protection circuit provided by the embodiment of the present invention has low cost, simple structure, easy implementation, and high stability.

[0048] Based on the same technical concept, an embodiment of the present invention further provides a communication device, including the above-mentioned battery over-discharge protection circuit.

[0049] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0050] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A battery over-discharge protection circuit, characterized in that: include: A first diode, a second diode, a third diode, a comparison circuit, a switch circuit and a first switch; The first diode is located between the power input terminal and the power output terminal of the device; The third diode is connected between the first end of the comparison circuit and the power input end of the device, the second diode is connected between the second end of the comparison circuit and the power output end of the device, and the third end of the comparison circuit is connected to the first end of the switch circuit; The second end of the switch circuit is connected to the power output end of the device after passing through the second diode, and the third end of the switch circuit is connected to the output end of the battery through the first switch; The comparison circuit controls the switch circuit to disconnect after determining that the voltage at the power input terminal is less than a preset voltage threshold; Wherein, the comparison circuit comprises a first resistor, a second resistor, a third resistor and an adjustable voltage source; The first end of the first resistor is the second end of the comparison circuit, the second end of the first resistor, the second end of the second resistor and the second end of the third resistor are respectively connected to the second end of the adjustable voltage-stabilizing source, the first end of the second resistor is the first end of the comparison circuit, the first end of the third resistor and the third end of the adjustable voltage-stabilizing source are respectively grounded, and the first end of the adjustable voltage-stabilizing source is the third end of the comparison circuit.

2. The battery over-discharge protection circuit according to claim 1, characterized in that: The comparison circuit also includes a control circuit; The control circuit includes a triode, a fourth resistor and a fifth resistor; The first end of the fourth resistor and the first end of the fifth resistor are connected to the control pin of the control chip of the device, the second end of the fourth resistor is connected to the first end of the transistor, the second end of the fifth resistor is connected to the second end of the transistor and then grounded, and the third end of the transistor is connected to the second end of the second resistor.

3. The battery over-discharge protection circuit as claimed in claim 2, characterized in that: The transistor is an NPN transistor.

4. The battery over-discharge protection circuit according to claim 1, characterized in that: The adjustable voltage stabilizing source is a TL431 adjustable voltage stabilizing source.

5. The battery over-discharge protection circuit according to claim 1, characterized in that: The switch circuit includes a MOS tube, a sixth resistor and a seventh resistor; The first end of the seventh resistor is the first end of the switch circuit, the second end of the seventh resistor and the second end of the sixth resistor are respectively connected to the first end of the MOS tube, the first end of the sixth resistor is connected to the third end of the MOS tube and serves as the third end of the switch circuit, and the second end of the MOS tube is the second end of the switch circuit.

6. The battery over-discharge protection circuit as claimed in claim 5, characterized in that: The MOS tube is a PMOS tube.

7. A communication device, characterized in that: The invention comprises a battery over-discharge protection circuit as claimed in any one of claims 1 to 6.

8. A battery, characterized in that: The invention comprises a battery over-discharge protection circuit as claimed in any one of claims 1 to 6.

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