An under-voltage protection circuit

Abstract

The utility model belongs to the technical field of electronic circuit, disclose a kind of under-voltage protection circuit, comprising: under-voltage protection module, power control module, LED load module and the power module for providing electric energy to other module respectively;Under-voltage protection module is also connected with power control module, is provided with first switch tube, second switch tube and characteristic resistance, first switch tube and second switch tube are used as comparison controller, according to the electric energy change provided by power module and switch into different switch state, to produce enable signal, and enable signal is transmitted to power control module;Characteristic resistance is used to be respectively as upper voltage dividing resistance or lower voltage dividing resistance under different switch state, to produce hysteresis voltage;Power control module and LED load module constitute load loop, and power control module is used to control the on-off of load loop according to enable signal;LED load module is provided with LED light unit.The utility model aims at improving the reliability of under-voltage protection circuit and reducing its circuit cost.

Description

Technical Field

[0001] This utility model relates to the field of electronic circuit technology, and in particular to an undervoltage protection circuit. Background Technology

[0002] In related technologies, some devices, such as the drive circuit of automotive lights, have undervoltage protection. When the power supply voltage drops below a set threshold, the circuit will shut off the output power to protect the downstream circuit system. However, due to losses such as line loss, there is a certain loss between the output of the power supply circuit and the input of the drive circuit. This results in a voltage difference between the two, which causes the circuit to repeatedly enter and exit the undervoltage protection state, frequently turning the output power supply on and off. This leads to unstable operation of the devices and can easily cause damage.

[0003] In summary, the technical problems existing in the relevant technologies need to be improved. Utility Model Content

[0004] This utility model aims to solve at least one of the technical problems existing in the prior art. To this end, this utility model proposes an undervoltage protection circuit, which includes: a power supply module, an undervoltage protection module, a power control module, and an LED load module; The power module is connected to the undervoltage protection module and the power control module respectively, and provides power to the undervoltage protection module, the power control module and the LED load module; The undervoltage protection module is also connected to the power control module. The undervoltage protection module is equipped with a first switching transistor, a second switching transistor, and a characteristic resistor. The first and second switching transistors are used as comparator controllers to switch to different switching states according to the changes in electrical energy provided by the power module, so as to generate an enable signal and transmit the enable signal to the power control module. The characteristic resistor is used as an upper voltage divider resistor or a lower voltage divider resistor in different switching states to generate hysteresis voltage. The power control module and the LED load module form a load circuit. The power control module is used to control the on / off state of the load circuit according to the enable signal. The LED load module is provided with an LED light-emitting unit.

[0005] In some embodiments, the undervoltage protection module further includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor. The first switching transistor is a first transistor, and the second switching transistor is a second transistor. The first power input terminal of the undervoltage protection module is connected to the first resistor, the third resistor, and the fourth resistor, respectively. The other end of the first resistor is connected to the second resistor and the base of the first transistor, respectively. The other end of the third resistor is connected to the collector of the first transistor, and the other end of the fourth resistor is connected to the collector of the second transistor. The fifth resistor is the characteristic resistor, connected between the base of the first transistor and the collector of the second transistor. The sixth resistor is connected between the collector of the first transistor and the base of the second transistor. The other end of the second resistor, the emitter of the first transistor, and the emitter of the second transistor are all grounded. The collector of the second transistor is provided with a first enable terminal, which is used to determine the enable signal.

[0006] In some embodiments, the first enable terminal is connected to the power control module and is used to determine the enable signal according to the logic level of the position of the first enable terminal and transmit the enable signal to the power control module.

[0007] In some embodiments, the undervoltage protection module further includes a Zener diode, and the first resistor is connected to the first power input terminal through the Zener diode.

[0008] In some embodiments, the undervoltage protection module further includes a seventh resistor, an eighth resistor, and a third transistor. One end of the seventh resistor is connected to the first power input terminal, and the other end of the seventh resistor is connected to the collector of the third transistor. The eighth resistor is connected between the collector of the first transistor and the base of the third transistor. The emitter of the third transistor is grounded. The collector of the third transistor is provided with a second enable terminal. The second enable terminal is used to replicate the logic level of the first enable terminal. The second enable terminal is connected to the power control module and is used to determine the enable signal according to the logic level of the second enable terminal and transmit the enable signal to the power control module.

[0009] In some embodiments, the power control module includes a fourth transistor, a fifth transistor, a sixth transistor, a seventh transistor, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, and a sixteenth resistor. The second power input terminal of the power control module is connected to the ninth resistor, the thirteenth resistor, the collector of the fourth transistor, and the collector of the sixth transistor, respectively. The collectors of the fourth transistor and the sixth transistor are also connected to the undervoltage protection module. The other end of the ninth resistor is connected to the base of the fifth transistor, and the other end of the thirteenth resistor is connected to the base of the seventh transistor. The collectors of the fifth transistor and the seventh transistor are connected to... The LED load module is connected, the base of the fourth transistor is connected to the tenth resistor, the other end of the tenth resistor is connected to the emitter of the fifth transistor, the eleventh resistor and the twelfth resistor respectively, the eleventh resistor and the twelfth resistor are connected in parallel, the base of the sixth transistor is connected to the fourteenth resistor, the other end of the fourteenth resistor is connected to the emitter of the seventh transistor, the fifteenth resistor and the sixteenth resistor respectively, the fifteenth resistor and the sixteenth resistor are connected in parallel, the emitter of the fourth transistor, the base of the fifth transistor, the other end of the eleventh resistor, the emitter of the sixth transistor, the base of the seventh transistor and the other end of the fifteenth resistor are all grounded.

[0010] In some embodiments, the circuit further includes a current limiting module, which includes a seventeenth resistor and an eighteenth resistor connected in parallel. One end of the parallel connection is connected to the power supply module and the LED load module, respectively, and the other end of the parallel connection is connected to the power control module.

[0011] In some embodiments, the power control module includes a chip control unit based on an LED driver chip. The chip control unit is provided with a third power input terminal, an enable input terminal, a control terminal, and a ground terminal. The third power input terminal is connected to the power supply module, the enable input terminal is connected to the undervoltage protection module, the control terminal is connected to the LED load module, and the ground terminal is grounded.

[0012] In some embodiments, the LED load module includes a first light-emitting diode and a second light-emitting diode connected in series in the same direction. The positive terminal of the first light-emitting diode is connected to the power supply module as a fourth power input terminal, and the negative terminal of the second light-emitting diode is connected to the power control module to form the load circuit.

[0013] In some embodiments, the power module includes a battery input terminal, a product input terminal, a nineteenth resistor, a first capacitor, and a diode. The battery input terminal is connected to the nineteenth resistor, and the other end of the nineteenth resistor is connected to the product input terminal and the positive terminal of the diode. The negative terminal of the diode serves as the power output terminal and is connected to the undervoltage protection module, the first capacitor, the power control module, and the LED load module. The other end of the first capacitor is grounded. The current flowing from the negative terminal of the diode passes sequentially through the branch connected to the undervoltage protection module and the branch connected to the first capacitor before flowing to the power control module and the LED load module, respectively.

[0014] The beneficial effects of this utility model are as follows: An undervoltage protection circuit is designed, comprising a power supply module, an undervoltage protection module, a power control module, and an LED load module. The power supply module is connected to the undervoltage protection module, the power control module, and the LED load module to provide electrical energy. The undervoltage protection module is also connected to the power control module. A first and second switching transistor within the power supply module act as a comparator controller, switching to different switching states based on changes in the electrical energy supplied by the power supply module, generating an enable signal. Simultaneously, a characteristic resistor within the power supply module acts as an upper or lower voltage divider resistor in different switching states, generating a hysteresis voltage, thus achieving a hysteresis-based undervoltage protection effect. The enable signal then controls the load loop formed between the power control module and the LED load module, achieving on / off control of the LED light-emitting unit. Compared to undervoltage protection circuits that repeatedly switch states, this application designs a hysteresis-based undervoltage protection circuit, allowing for a smoother transition between undervoltage protection states, avoiding frequent switching, and improving circuit reliability. Furthermore, this hysteresis-based undervoltage protection effect is achieved based on switching transistors, without relying on integrated ICs or other components, reducing the cost of the undervoltage protection circuit. Attached Figure Description

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 A, Figure 1 B is a schematic diagram of the framework of an undervoltage protection circuit provided in an embodiment of this utility model; Figure 2 A schematic diagram of the undervoltage protection module provided in an embodiment of this utility model; Figure 3 A, Figure 3 B is a schematic diagram of the current direction of the undervoltage protection module provided in this embodiment of the utility model; Figure 4 A schematic diagram of an undervoltage protection module provided in another embodiment of this utility model; Figure 5A schematic diagram of an undervoltage protection module provided in another embodiment of this utility model; Figure 6 A schematic diagram of the power control module provided in an embodiment of this utility model; Figure 7 A schematic diagram of the undervoltage protection circuit provided in this embodiment of the utility model; Figure 8 A, Figure 8 B is a schematic diagram of the current direction of the undervoltage protection circuit provided in this embodiment of the utility model; Figure 9 This is a schematic diagram of a power control module provided in another embodiment of the present invention.

[0016] In the diagram: Power module 100, undervoltage protection module 200, power control module 300, LED load module 400, current limiting module 500, chip control unit 510, first enable terminal EN1, second enable terminal EN2, first power input terminal VIN1, second power input terminal VIN2, battery input terminal VBAT, product input terminal VIN, first resistor R1, second resistor R2, third resistor R3, fourth resistor R4, fifth resistor R5, sixth resistor R6, seventh resistor R7, eighth resistor R8, ninth resistor R9, tenth resistor R10, eleventh resistor R11, twelfth resistor R1 2. Thirteenth resistor R13, fourteenth resistor R14, fifteenth resistor R15, sixteenth resistor R16, seventeenth resistor R17, eighteenth resistor R18, nineteenth resistor R19, Zener diode D1, diode D2, first light-emitting diode LED1, second light-emitting diode LED2, first capacitor C1, second capacitor C2, third capacitor C3, fourth capacitor C4, fifth capacitor C5, sixth capacitor C6, seventh capacitor C7, first transistor Q1, second transistor Q2, third transistor Q3, fourth transistor Q4, fifth transistor Q5, sixth transistor Q6, seventh transistor Q7. Detailed Implementation

[0017] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0018] In related technologies, some devices, such as the drive circuit of automotive lights, have an undervoltage protection design. When the power supply voltage drops below a set threshold, the circuit will shut off the output power supply to protect the downstream circuit system. However, due to losses such as line loss, there is a certain loss between the output of the power supply circuit and the input of the drive circuit. This results in a voltage difference between the two. When the drive circuit detects that the voltage is below the set threshold and determines to enter the undervoltage protection state, the voltage on the power supply circuit side may still be above the set threshold. At this time, the current of the circuit in the undervoltage protection state decreases sharply, the line loss decreases, and the voltage on the drive circuit side becomes closer to the original voltage on the power supply circuit side. The voltage rises again to a level above the set threshold, and the undervoltage protection state is determined to be exited. However, after exiting, the line loss will reappear. This leads to repeated entry and exit from the undervoltage protection state, frequent switching of the output power supply, resulting in unstable operation of the device and easy damage to it.

[0019] In view of this, an undervoltage protection circuit is provided in the embodiments of this application. Figure 1 A, Figure 1 B is a schematic diagram of an undervoltage protection circuit provided in an embodiment of this application. Figure 1 The undervoltage protection circuit may include, but is not limited to: power module 100, undervoltage protection module 200, power control module 300, and LED load module 400; The power module 100 is connected to the undervoltage protection module 200 and the power control module 300 respectively, and provides power to the undervoltage protection module 200, the power control module 300 and the LED load module 400. The undervoltage protection module 200 is also connected to the power control module 300. The undervoltage protection module 200 is equipped with a first switching transistor, a second switching transistor, and a characteristic resistor. The first and second switching transistors are used as a comparator controller to switch to different switching states according to the changes in electrical energy provided by the power module 100, so as to generate an enable signal and transmit the enable signal to the power control module 200. The characteristic resistor is used as an upper voltage divider resistor or a lower voltage divider resistor in different switching states to generate hysteresis voltage. The power control module 300 and the LED load module 400 form a load circuit. The power control module 300 is used to control the on / off state of the load circuit according to the enable signal. The LED load module 400 is equipped with an LED light-emitting unit. Figure 1 A and Figure 1 B is used to illustrate two different power supply methods for the LED load module 400. The LED load module 400 can be powered as follows: Figure 1 As shown in Figure A, power can be drawn directly from the power module 100, or as shown in Figure A. Figure 1 As shown in Figure B, power is drawn from the power control module 300.

[0020] Specifically, the first and second switching transistors are connected and function as a comparator controller. Their switching states change according to the power supply provided by the power module 100, thus providing undervoltage protection. For example, when the circuit is on (not undervoltage protection), the first switching transistor is on and the second switching transistor is off; conversely, when the circuit is undervoltage protection, the first switching transistor is off and the second switching transistor is on. The switching state changes of the first and second switching transistors are reflected in the level of the enable signal, thereby affecting whether the load circuit between the power control module 300 and the LED load module 400 is connected.

[0021] The characteristic resistor is also connected to both the first and second switching transistors. Its role in the circuit changes as the switching states of the two transistors change. For example, when the circuit is on, the characteristic resistor acts as the upper voltage divider resistor; while when the circuit is in undervoltage protection mode, it acts as the lower voltage divider resistor. This difference in function results in the generation of hysteresis voltage, thus providing undervoltage protection with hysteresis.

[0022] In addition, the LED light-emitting unit is used to refer to the light-emitting device based on LED in the LED load module 400. In other embodiments, other types of load modules can be used to replace the LED load module 400 without affecting the undervoltage protection function with hysteresis played by other modules in this embodiment.

[0023] This embodiment designs an undervoltage protection circuit, including a power supply module 100, an undervoltage protection module 200, a power control module 300, and an LED load module 400. The power supply module 100 is connected to the undervoltage protection module 200, the power control module 300, and the LED load module 400 to provide power. The undervoltage protection module 200 is also connected to the power control module 300. The first and second switching transistors in the power supply module 100 act as a comparator controller, switching to different switching states according to the changes in the power supplied by the power supply module 100, generating an enable signal. At the same time, the characteristic resistors in the power supply module 200 act as upper or lower voltage divider resistors in different switching states, generating hysteresis voltage to achieve undervoltage protection with hysteresis. Then, the enable signal controls the load loop formed between the power control module 300 and the LED load module 400 to control the on / off state of the LED light-emitting unit. Compared with undervoltage protection circuits that repeatedly switch states, this application designs an undervoltage protection circuit with hysteresis, which allows for a smoother transition when switching undervoltage protection states, avoiding frequent switching and improving circuit reliability. At the same time, the undervoltage protection effect with hysteresis is achieved based on switching transistors and does not rely on integrated ICs or other devices, thus reducing the cost of the undervoltage protection circuit.

[0024] refer to Figure 2 In some embodiments, the undervoltage protection module 200 further includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, and a sixth resistor R6. The first switching transistor is a first transistor Q1, and the second switching transistor is a second transistor Q2. The first power input terminal VIN1 of the undervoltage protection module 200 is connected to the first resistor R1, the third resistor R3, and the fourth resistor R4, respectively. The other end of the first resistor R1 is connected to the second resistor R2 and the base of the first transistor Q1, respectively. The other end of the third resistor R3 is connected to the base of the first transistor Q1. The collector of the first transistor Q1 is connected to the first transistor Q2, and the other end of the fourth resistor R4 is connected to the collector of the second transistor Q2. The fifth resistor R5 is a characteristic resistor and is connected between the base of the first transistor Q1 and the collector of the second transistor Q2. The sixth resistor R6 is connected between the collector of the first transistor Q1 and the base of the second transistor Q2. The other end of the second resistor R2, the emitter of the first transistor Q1, and the emitter of the second transistor Q2 are all grounded. The collector of the second transistor Q2 is provided with a first enable terminal EN1, which is used to determine the enable signal.

[0025] Specifically, both transistor Q1 and transistor Q2 are NPN transistors, according to Figure 2 As shown and described above, when the circuit is on (i.e., not in undervoltage protection mode), the first transistor Q1 is on and the second transistor Q2 is off. At this time, the fifth resistor R5 acts as the upper voltage divider resistor for the base of the first transistor Q1. Additionally, the first resistor R1 and the fourth resistor R4 also act as upper voltage dividers, and the second resistor R2 acts as a lower voltage divider resistor. However, when the circuit is in undervoltage protection mode, and the load circuit between the power control module 300 and the LED load module 400 is disconnected, the first transistor Q1 is off and the second transistor Q2 is on. At this time, the fifth resistor R5 acts as the lower voltage divider resistor for the first transistor Q1. Additionally, the first resistor R1 acts as an upper voltage divider resistor, and the second resistor R2 acts as a lower voltage divider resistor. The current flow in both states can be referenced. Figure 3 As shown, Figure 3 A indicates that the first transistor Q1 is turned on and the second transistor Q2 is turned off, which shows the current flow when the device is not in undervoltage protection mode. Figure 3 B indicates that the first transistor Q1 is off and the second transistor Q2 is on, which shows the current flow under undervoltage protection conditions. It should be noted that... Figure 3 Only the current flow direction of the key branches is shown; the current flow directions of all branches are not shown. Based on the changing role of the fifth resistor R5 as a positive feedback resistor, hysteresis voltages are generated due to the on / off states of the first transistor Q1 and the second transistor Q2, thus affecting the input hysteresis voltage corresponding to the on / off state of the first transistor Q1.

[0026] On the other hand, the first enable terminal EN1 is also driven by the first transistor Q1. Based on the switching state of the first transistor Q1, it generates high and low level changes, which are ultimately reflected as logic level changes at the first enable terminal EN1 to determine the enable signal. This enable signal is the signal used to control the power control module 300. When not in undervoltage protection mode, the enable signal is high; when in undervoltage protection mode, the enable signal is low.

[0027] In addition, a capacitor, defined as a second capacitor, can be added to the undervoltage protection module 200. This second capacitor is connected between the base of the first transistor Q1 and ground. (Refer to...) Figure 2 This serves to decouple the components.

[0028] Through the coordination between the first transistor Q1, the second transistor Q2, and the fifth resistor R5, the undervoltage protection module 200 produces an undervoltage protection effect with hysteresis, improving the reliability of the circuit, and generating an enable signal to control the on / off state of the subsequent circuit power control module 300 and LED load module 400.

[0029] In some embodiments, the first enable terminal EN1 is connected to the power control module 300 and is used to determine an enable signal based on the logic level of the position of the first enable terminal EN1 and transmit the enable signal to the power control module 300.

[0030] In this embodiment, an enable signal can be directly output through the first enable terminal EN1 and connected to the power control module 300, so that the first enable terminal EN1 can directly control the power control module 300 in the subsequent stage, thereby realizing the control of the power control module 300 by the undervoltage protection module 200 and thus realizing the state switching of undervoltage protection.

[0031] In some embodiments, reference Figure 4 The undervoltage protection module 200 also includes a Zener diode D1, and the first resistor R1 is connected to the first power input terminal VIN1 through the Zener diode D1.

[0032] Optionally, in the undervoltage protection module 200, a Zener diode D1 can also be added between the first resistor R1 and the first power input terminal VIN1. The positive terminal of the Zener diode D1 is connected to the first resistor R1, and the negative terminal is connected to the first power input terminal VIN1. By adding the Zener diode D1, the accuracy of the undervoltage protection setting threshold, i.e. the undervoltage protection threshold, can be improved, thereby improving the accuracy of the circuit's undervoltage protection.

[0033] In some embodiments, reference Figure 5The undervoltage protection module 200 also includes a seventh resistor R7, an eighth resistor R8, and a third transistor Q3. One end of the seventh resistor R7 is connected to the first power input terminal VIN1, and the other end of the seventh resistor R7 is connected to the collector of the third transistor Q3. The eighth resistor R8 is connected between the collector of the first transistor Q1 and the base of the third transistor Q3. The emitter of the third transistor Q3 is grounded. The collector of the third transistor Q3 is provided with a second enable terminal EN2. The second enable terminal EN2 is used to replicate the logic level of the first enable terminal EN1. The second enable terminal EN2 is connected to the power control module 300 and is used to determine the enable signal according to the logic level of the second enable terminal EN2 and transmit the enable signal to the power control module 300.

[0034] Compared to Figure 2 The circuit shown in this embodiment mainly adds a third transistor Q3, and forms a second enable terminal EN2 based on the third transistor Q3. This second enable terminal EN2 is used to replicate the logic level of the first enable terminal EN1. When the first enable terminal EN1 is high, the second enable terminal EN2 is also high, and vice versa. At the same time, unlike the above embodiment, the subsequent circuits (power control module 300 and LED load module 400) are also controlled based on the enable signal determined by the second enable terminal EN2, rather than directly using the first enable terminal EN1. This can avoid the impedance of the subsequent circuit affecting the level of the first enable terminal EN1, and thus affecting the value of the hysteresis voltage; when the impedance of the subsequent circuit is high, it is more inclined to directly use the first enable terminal EN1 to output the enable signal.

[0035] Specifically, based on the circuit of this embodiment, when the first transistor Q1 is turned off, the voltage divider resistor at its base is... Its lower voltage divider resistor value is (Ignore the on-state voltage drop of the second transistor Q2); when the first transistor Q1 is turned on, the voltage divider resistance at its base is... Its lower voltage divider resistor value is ,in, Indicates resistance and The resistance value in parallel, Indicates resistance and The resistance value in series.

[0036] Therefore, when the base voltage of the first transistor Q1 is greater than or equal to its turn-on voltage, the first transistor Q1 conducts, and the downstream circuit operates; when the base voltage of the first transistor Q1 is less than its turn-on voltage, the first transistor Q1 is turned off, and the downstream circuit is disconnected. Thus, the input undervoltage protection threshold... The formula is as follows (1): (1) in, This is the turn-on voltage of the first transistor Q1.

[0037] When the input voltage at the first power input terminal VIN1 rises from 0V to... During the process, the base voltage of the first transistor Q1 rises from 0V, therefore the first transistor Q1 remains off during the rising process, at which point the following condition is met. ,and By substituting it into equation (1) above, we can obtain equation (2) below: (2) in, This is the undervoltage protection threshold during the process of the input voltage rising from 0V to the undervoltage protection threshold.

[0038] When the input voltage at the first power input terminal VIN1 is higher than During the process of the voltage dropping to 0V, the base voltage of the first transistor Q1 decreases from a level greater than the turn-on voltage. Therefore, the first transistor Q1 remains on during the decrease, and at this time, the following condition is met. ,and By substituting it into equation (1) above, we can obtain equation (3) below: (3) in, The undervoltage protection threshold is the value of the input voltage as it drops from above the undervoltage protection threshold to the undervoltage protection threshold.

[0039] By comparing equations (2) and (3), it can be determined that Therefore, hysteresis voltage is generated. And satisfy equation (4): (4) As the resistance of R5 decreases The voltage will increase, so in practical applications, the required hysteresis voltage can be set by adjusting the resistance value of R5.

[0040] In addition, it should be noted that although Figure 5 The circuit is not shown, but in this embodiment, a Zener diode D1 can be added between the first resistor R1 and the first power input terminal VIN1 to improve the accuracy of the undervoltage protection threshold.

[0041] By setting the second enable terminal EN2, the influence of the subsequent circuit on the enable signal is avoided, and R5, as a positive feedback resistor, can affect the hysteresis voltage, thereby improving the accuracy of the circuit's undervoltage protection.

[0042] In some embodiments, reference Figure 6The power control module 300 includes a fourth transistor Q4, a fifth transistor Q5, a sixth transistor Q6, a seventh transistor Q7, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12, a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, and a sixteenth resistor R16. The second power input terminal VIN2 of the power control module 300 is connected to the ninth resistor R9, the thirteenth resistor R13, the collector of the fourth transistor Q4, and the collector of the sixth transistor Q6. The collectors of the fourth transistor Q4 and the sixth transistor Q6 are also connected to the undervoltage protection module 200. The other end of the ninth resistor R9 is connected to the base of the fifth transistor Q5, and the other end of the thirteenth resistor R13 is connected to the base of the seventh transistor Q7. The collector of the fifth transistor Q5... The collector of the fourth transistor Q4 and the seventh transistor Q7 are connected to the LED load module 400. The base of the fourth transistor Q4 is connected to the tenth resistor R10. The other end of the tenth resistor R10 is connected to the emitter of the fifth transistor Q5, the eleventh resistor R11, and the twelfth resistor R12. The eleventh resistor R11 and the twelfth resistor R12 are connected in parallel. The base of the sixth transistor Q6 is connected to the fourteenth resistor R14. The other end of the fourteenth resistor R14 is connected to the emitter of the seventh transistor Q7, the fifteenth resistor R15, and the sixteenth resistor R16. The fifteenth resistor R15 and the sixteenth resistor R16 are connected in parallel. The emitter of the fourth transistor Q4, the base of the fifth transistor, the other end of the eleventh resistor R11, the emitter of the sixth transistor Q6, the base of the seventh transistor, and the other end of the fifteenth resistor R15 are all grounded.

[0043] Specifically, the power control module 300 can be divided into two parallel power control units. One unit includes a fourth transistor Q4, a fifth transistor Q5, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, and a twelfth resistor R12. The other unit includes a sixth transistor Q6, a seventh transistor Q7, a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, and a sixteenth resistor R16. The fourth transistor Q4, the fifth transistor Q5, the sixth transistor Q6, and the seventh transistor Q7 are all NPN transistors.

[0044] The two power control units have the same control logic: they obtain power from the power module 100, obtain the enable signal from the first enable terminal EN1 or the second enable terminal EN2 from the undervoltage protection module 200, and form a load loop with the LED load module 400. Figure 6The connection point between the LED load circuit and the circuit is indicated by OUT. The switching states of transistors Q5 (fifth transistor) and Q7 (seventh transistor) actually affect the continuity of the load circuit. When transistor Q1 is off, transistors Q5 and Q7 are also off via the enable signal, thus disconnecting the load circuit. When transistor Q1 is on, transistors Q5 and Q7 are also on via the enable signal, thus connecting the load circuit. The switching states of transistors Q5 and Q7 are identical.

[0045] In addition, decoupling capacitors can be added to the power control module 300, defined as the third, fourth, fifth, and sixth capacitors, all of which are electrolytic capacitors. For details, refer to... Figure 6 Connect the third capacitor between the base of the fifth transistor Q5 and ground, connect the fourth capacitor between the base of the fourth transistor Q4 and its emitter, connect the fifth capacitor between the base of the seventh transistor Q7 and ground, and connect the sixth capacitor between the base of the sixth transistor Q6 and its emitter.

[0046] By setting the power control module 300, the load circuit can be switched on and off according to the enable signal of the undervoltage protection module 200, thereby achieving the control effect of the LED load.

[0047] In some embodiments, reference Figure 7 The circuit also includes a current limiting module 500, which includes a seventeenth resistor R17 and an eighteenth resistor R18 connected in parallel. One end of the parallel connection is connected to the power supply module 100 and the LED load module 400, respectively, and the other end of the parallel connection is connected to the power control module 300.

[0048] The seventeenth resistor R17 and the eighteenth resistor R18 in the current limiting module 500 provide base current for the fifth transistor Q5 and the seventh transistor Q7. When the enable signal is low, it makes the base level of the fifth transistor Q5 and the seventh transistor Q7 also low, thereby turning off the fifth transistor Q5 and the seventh transistor Q7 and breaking the conduction circuit. Conversely, it turns on, thereby supporting the function implementation of the undervoltage protection module 200 and the power control module 300.

[0049] In addition, a capacitor, defined as the seventh capacitor, can be added to the current limiting module 500, and connected in parallel with the seventeenth resistor R17 and the eighteenth resistor R18, as shown in the reference. Figure 7 This serves to decouple the components.

[0050] In some embodiments, reference Figure 7 , Figure 7The LED load module 400 draws power directly from the power supply module 100. The LED load module 400 includes a first light-emitting diode LED1 and a second light-emitting diode LED2 connected in series in the same direction. The positive terminal of the first light-emitting diode LED1 is connected to the power supply module 100 as the fourth power input terminal, and the negative terminal of the second light-emitting diode LED2 is connected to the power control module 300 to form a load circuit.

[0051] In this embodiment, the LED light-emitting unit of the LED load module 400 includes two light-emitting diodes, specifically a first light-emitting diode LED1 and a second light-emitting diode LED2. The two light-emitting diodes are in the same direction and connected in series, so that the power supplied by the power module 100 can achieve the effect of lighting.

[0052] also, Figure 7 LED+ and LED- are used to indicate the positive and negative terminals of the load circuit, respectively.

[0053] In some embodiments, reference Figure 7 The power module 100 includes a battery input terminal VBAT, a product input terminal VIN, a nineteenth resistor R19, a first capacitor C1, and a diode D2. The battery input terminal VBAT is connected to the nineteenth resistor R19. The other end of the nineteenth resistor R19 is connected to the product input terminal VIN and the positive terminal of the diode D2. The negative terminal of the diode D2 serves as the power output terminal and is connected to the undervoltage protection module 200, the first capacitor C1, the power control module 300, and the LED load module 400. The other end of the first capacitor C1 is grounded. The current flowing from the negative terminal of the diode D2 passes sequentially through the branch connected to the undervoltage protection module 200 and the branch connected to the first capacitor C1, and then flows to the power control module 300 and the LED load module 400, respectively.

[0054] The power module 100 includes a battery input terminal VBAT and a product input terminal VIN. The battery input terminal VBAT receives electrical energy generated by the battery and also supports undervoltage protection during the gradual rise and fall of the battery voltage, as described in this embodiment. The product input terminal VIN receives electrical energy generated by an external circuit or other power supply device. Optionally, the product input terminal VIN can serve as the conventional power supply for the circuit in this embodiment, while the battery input terminal VBAT serves as a backup power supply.

[0055] In conjunction with the above embodiments, refer to Figure 8 , Figure 8 A illustrates the current flow in the undervoltage protection circuit when it is not in undervoltage protection mode. Figure 8 B illustrates the current flow in the undervoltage protection circuit when it is in undervoltage protection mode. It should be noted that... Figure 8Only the current flow direction of the critical branches is shown; the current flow direction of all branches is not shown.

[0056] In some embodiments, reference Figure 9 The power control module 300 includes a chip control unit 510 based on an LED driver chip. The chip control unit 510 is provided with a third power input terminal, an enable input terminal, a control terminal and a ground terminal. The third power input terminal is connected to the power supply module 100, the enable input terminal is connected to the undervoltage protection module 200, the control terminal is connected to the LED load module 400, and the ground terminal is grounded.

[0057] Unlike the embodiments described above, the power control effect of the power control module 300 can also be achieved by setting up an LED driver chip and its supporting circuitry, rather than by using the aforementioned transistor. Furthermore, it is more suitable for directly determining the enable signal using the first enable terminal EN1. Figure 9 The circuit shown includes, for example: Figure 2 The undervoltage protection module 200 of the illustrated embodiment. A chip control unit 510 is built based on the LED driver chip. In this case, the LED load module 400 can draw power from the power control module 300, rather than being directly connected to the power supply module 100. This results in more precise control and a higher degree of circuit integration, but it is also more expensive than solutions based on the fifth transistor Q5 and the seventh transistor Q7.

[0058] In the description of this utility model, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0059] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.

[0060] In the description of this utility model, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this utility model. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0061] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. An undervoltage protection circuit, characterized in that, The circuit includes a power supply module, an undervoltage protection module, a power control module, and an LED load module; The power module is connected to the undervoltage protection module and the power control module respectively, and provides power to the undervoltage protection module, the power control module and the LED load module; The undervoltage protection module is also connected to the power control module. The undervoltage protection module is equipped with a first switching transistor, a second switching transistor, and a characteristic resistor. The first and second switching transistors are used as comparator controllers to switch to different switching states according to the changes in electrical energy provided by the power module, so as to generate an enable signal and transmit the enable signal to the power control module. The characteristic resistor is used as an upper voltage divider resistor or a lower voltage divider resistor in different switching states to generate hysteresis voltage. The power control module and the LED load module form a load circuit. The power control module is used to control the on / off state of the load circuit according to the enable signal. The LED load module is provided with an LED light-emitting unit.

2. The circuit according to claim 1, characterized in that, The undervoltage protection module further includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor. The first switching transistor is a first transistor, and the second switching transistor is a second transistor. The first power input terminal of the undervoltage protection module is connected to the first resistor, the third resistor, and the fourth resistor, respectively. The other end of the first resistor is connected to the second resistor and the base of the first transistor, respectively. The other end of the third resistor is connected to the collector of the first transistor, and the other end of the fourth resistor is connected to the collector of the second transistor. The fifth resistor is the characteristic resistor and is connected between the base of the first transistor and the collector of the second transistor. The sixth resistor is connected between the collector of the first transistor and the base of the second transistor. The other end of the second resistor, the emitter of the first transistor, and the emitter of the second transistor are all grounded. The collector of the second transistor is provided with a first enable terminal, which is used to determine the enable signal.

3. The circuit according to claim 2, characterized in that, The first enable terminal is connected to the power control module and is used to determine the enable signal according to the logic level of the first enable terminal position and transmit the enable signal to the power control module.

4. The circuit according to claim 2, characterized in that, The undervoltage protection module also includes a Zener diode, and the first resistor is connected to the first power input terminal through the Zener diode.

5. The circuit according to claim 2, characterized in that, The undervoltage protection module further includes a seventh resistor, an eighth resistor, and a third transistor. One end of the seventh resistor is connected to the first power input terminal, and the other end of the seventh resistor is connected to the collector of the third transistor. The eighth resistor is connected between the collector of the first transistor and the base of the third transistor. The emitter of the third transistor is grounded. The collector of the third transistor is provided with a second enable terminal. The second enable terminal is used to replicate the logic level of the first enable terminal. The second enable terminal is connected to the power control module and is used to determine the enable signal according to the logic level of the second enable terminal and transmit the enable signal to the power control module.

6. The circuit according to claim 1, characterized in that, The power control module includes a fourth transistor, a fifth transistor, a sixth transistor, a seventh transistor, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, and a sixteenth resistor. The second power input terminal of the power control module is connected to the ninth resistor, the thirteenth resistor, the collector of the fourth transistor, and the collector of the sixth transistor, respectively. The collectors of the fourth transistor and the sixth transistor are also connected to the undervoltage protection module. The other end of the ninth resistor is connected to the base of the fifth transistor, and the other end of the thirteenth resistor is connected to the base of the seventh transistor. The collectors of the fifth transistor and the seventh transistor are connected to the LE. The load module is connected in D. The base of the fourth transistor is connected to the tenth resistor. The other end of the tenth resistor is connected to the emitter of the fifth transistor, the eleventh resistor, and the twelfth resistor. The eleventh resistor and the twelfth resistor are connected in parallel. The base of the sixth transistor is connected to the fourteenth resistor. The other end of the fourteenth resistor is connected to the emitter of the seventh transistor, the fifteenth resistor, and the sixteenth resistor. The fifteenth resistor and the sixteenth resistor are connected in parallel. The emitter of the fourth transistor, the base of the fifth transistor, the other end of the eleventh resistor, the emitter of the sixth transistor, the base of the seventh transistor, and the other end of the fifteenth resistor are all grounded.

7. The circuit according to claim 6, characterized in that, The circuit also includes a current limiting module, which includes a seventeenth resistor and an eighteenth resistor connected in parallel. One end of the parallel connection is connected to the power supply module and the LED load module, respectively, and the other end of the parallel connection is connected to the power control module.

8. The circuit according to claim 1, characterized in that, The power control module includes a chip control unit based on an LED driver chip. The chip control unit is provided with a third power input terminal, an enable input terminal, a control terminal, and a ground terminal. The third power input terminal is connected to the power supply module, the enable input terminal is connected to the undervoltage protection module, the control terminal is connected to the LED load module, and the ground terminal is grounded.

9. The circuit according to claim 1, characterized in that, The LED load module includes a first light-emitting diode and a second light-emitting diode connected in series in the same direction. The positive terminal of the first light-emitting diode is connected to the power supply module as the fourth power input terminal, and the negative terminal of the second light-emitting diode is connected to the power control module to form the load circuit.

10. The circuit according to claim 1, characterized in that, The power module includes a battery input terminal, a product input terminal, a nineteenth resistor, a first capacitor, and a diode. The battery input terminal is connected to the nineteenth resistor, and the other end of the nineteenth resistor is connected to both the product input terminal and the positive terminal of the diode. The negative terminal of the diode serves as the power output terminal and is connected to the undervoltage protection module, the first capacitor, the power control module, and the LED load module. The other end of the first capacitor is grounded. The current flowing from the negative terminal of the diode passes sequentially through the branch connected to the undervoltage protection module and the branch connected to the first capacitor before flowing to the power control module and the LED load module, respectively.

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