Over-temperature protection circuit and LED driving system

Abstract

The invention provides an over-temperature protection circuit and an LED driving system, and relates to the technical field of integrated circuits, and the over-temperature protection circuit comprises a positive temperature coefficient current module, an over-temperature adaptive module and an over-temperature hysteresis turn-off module. When the temperature of the LED device is smaller than the over-temperature threshold value, the over-temperature self-adaption module outputs reference voltage to the LED driving circuit. And when the temperature of the LED device is greater than or equal to the over-temperature threshold value and the temperature of the LED device is less than the over-temperature threshold value, the over-temperature self-adaptive module outputs a negative temperature coefficient voltage which is reduced along with the rise of the temperature to the LED driving circuit. And when the temperature of the LED device is greater than or equal to the over-temperature threshold value, the over-temperature hysteresis turn-off module outputs turn-off voltage to the LED driving circuit, so that the LED driving circuit stops working. The over-temperature protection circuit can prevent the LED from being turned off suddenly due to over-temperature on the premise of ensuring safety, and meanwhile, the service life of the LED device is prolonged.

Description

Technical Field

[0001] The present application relates to the technical field of integrated circuits, and in particular to an over-temperature protection circuit and an LED driving system. Background Art

[0002] As a light-sensitive device, the performance of LED is significantly affected by temperature. When the junction temperature rises, the forward voltage drop will decrease, which will cause the current to change. At the same time, the temperature increase will also cause the luminous efficiency of the LED to decrease. Therefore, in the LED drive circuit, over-temperature protection is very important.

[0003] Traditional LED over-temperature protection mechanisms usually take measures such as immediate power outage or rapid current zeroing to protect the subsequent circuits from working immediately. However, this treatment method is not suitable for areas that require continuous lighting, such as car lighting, etc. Sudden power outages will affect driving safety and pose a great safety hazard.

[0004] Therefore, how to avoid sudden LED light-off due to overheating while ensuring safety and at the same time prolonging the service life of LED has become a major challenge in LED overtemperature protection design. Summary of the invention

[0005] The purpose of the present application is to provide an over-temperature protection circuit and an LED driving system to prevent the LED from suddenly turning off due to over-temperature while ensuring safety, and to increase the service life of the LED.

[0006] In order to achieve the above purpose, the technical solution adopted in this application is as follows: On the one hand, the present application provides an over-temperature protection circuit for providing a driving voltage and a shutdown voltage for an LED driving circuit, wherein the LED driving circuit is connected to an LED device, and the over-temperature protection circuit comprises: a positive temperature coefficient current module, an over-temperature adaptive module, and an over-temperature hysteresis shutdown module; The first port of the positive temperature coefficient current module, the first port of the over-temperature adaptive module and the first port of the over-temperature hysteresis shutdown module are all connected to a first node, the output end of the over-temperature adaptive module is connected to the driving input end of the LED driving circuit, and the output end of the over-temperature hysteresis shutdown module is connected to the shutdown control end of the LED driving circuit; The positive temperature coefficient current module is used to provide a positive temperature coefficient current for the over-temperature adaptive module and the over-temperature hysteresis shutdown module; When the temperature of the LED device When the over-temperature threshold is reached, the over-temperature adaptive module is used to output a reference voltage to the LED driving circuit; When the over temperature threshold LED device temperature When the temperature exceeds the threshold, the over-temperature adaptive module is used to output a negative temperature coefficient voltage to the LED driving circuit that decreases as the temperature increases; When the temperature of the LED device When the temperature exceeds the threshold value, the over-temperature hysteresis shutdown module is used to output a shutdown voltage to the LED driving circuit to stop the LED driving circuit from working.

[0007] Further, the over-temperature adaptive module includes: a first positive temperature coefficient voltage generating unit, a voltage subtractor, a second positive temperature coefficient voltage generating unit, a first control unit, a first transmission gate and a second transmission gate; The first port of the first positive temperature coefficient voltage generating unit is connected to the first node, the second port of the first positive temperature coefficient voltage generating unit is connected to the first input terminal of the voltage subtractor, the second input terminal of the voltage subtractor is connected to the reference voltage, and the output terminal of the voltage subtractor outputs a negative temperature coefficient voltage; The first port of the second positive temperature coefficient voltage generating unit and the first port of the first control unit are both connected to the first node, and the second port of the second positive temperature coefficient voltage generating unit is connected to the control terminal of the first control unit; The first port of the first transmission gate and the second port of the second transmission gate are both connected to the second output end of the first control unit, the second port of the first transmission gate and the first port of the second transmission gate are both connected to the first output end of the first control unit, the third port of the first transmission gate is connected to the second input end of the voltage subtractor, the third port of the second transmission gate is connected to the output end of the voltage subtractor, and the fourth port of the first transmission gate and the fourth port of the second transmission gate are connected to serve as the output end of the over-temperature adaptive module; When the temperature of the LED device At the over-temperature threshold, the first output terminal of the first control unit is at a low level, the second output terminal of the first control unit is at a high level, the first transmission gate is turned on, the second transmission gate is turned off, and the over-temperature adaptive module outputs a reference voltage; When the over temperature threshold LED device temperature When the temperature threshold is exceeded, the first output terminal of the first control unit is at a high level, the second output terminal of the first control unit is at a low level, the first transmission gate is turned off, the second transmission gate is turned on, and the over-temperature adaptive module outputs a negative temperature coefficient voltage.

[0008] Further, the first positive temperature coefficient voltage generating unit includes a first PMOS tube and a first resistor, and the voltage subtractor includes a second resistor, a third resistor and an operational amplifier; The source of the first PMOS tube is connected to a power supply, the gate of the first PMOS tube is connected to the first node, the drain of the first PMOS tube is respectively connected to one end of the first resistor and one end of the second resistor, and the other end of the first resistor is grounded; The other end of the second resistor is connected to the inverting input terminal of the operational amplifier and one end of the third resistor respectively, the other end of the third resistor is connected to the output terminal of the operational amplifier, and the non-inverting input terminal of the operational amplifier is connected to a reference voltage.

[0009] Further, the second positive temperature coefficient voltage generating unit includes a second PMOS tube and a fourth resistor, and the first control unit includes a third PMOS tube, a first NMOS tube and a secondary inverter; The source of the second PMOS tube, the source of the third PMOS tube and the first port of the secondary inverter are all connected to a power supply, the gate of the second PMOS tube and the gate of the third PMOS tube are both connected to the first node, the drain of the second PMOS tube is respectively connected to one end of the fourth resistor and the gate of the first NMOS tube, and the other end of the fourth resistor, the source of the first NMOS tube and the second port of the secondary inverter are all grounded; The drain of the first NMOS tube is connected to the drain of the third PMOS tube and the input end of the secondary inverter respectively, the first output end of the secondary inverter is connected to the second port of the first transmission gate and the first port of the second transmission gate respectively, and the second output end of the secondary inverter is connected to the first port of the first transmission gate and the second port of the second transmission gate respectively; When the temperature of the LED device When the temperature is over the threshold, the first NMOS tube is turned off, the first output end of the secondary inverter is at a low level, and the second output end of the secondary inverter is at a high level; When the over temperature threshold LED device temperature When the temperature threshold is exceeded, the first NMOS tube is turned on, the first output end of the secondary inverter is at a high level, and the second output end of the secondary inverter is at a low level.

[0010] Further, the secondary inverter includes a fourth PMOS tube, a fifth PMOS tube, a second NMOS tube and a third NMOS tube; The source of the fourth PMOS tube and the source of the fifth PMOS tube are both connected to a power supply, and the source of the second NMOS tube and the source of the third NMOS tube are both grounded; The gate of the fourth PMOS tube and the gate of the second NMOS tube are both connected to the drain of the first NMOS tube. The drain of the fourth PMOS tube and the drain of the second NMOS tube are connected and then serve as the first output end of the secondary inverter and are respectively connected to the second port of the first transmission gate, the first port of the second transmission gate, the gate of the fifth PMOS tube and the gate of the third NMOS tube. The drain of the fifth PMOS tube and the drain of the third NMOS tube are connected and then serve as the second output end of the secondary inverter.

[0011] Further, the first transmission gate includes a fourth NMOS tube and a sixth PMOS tube, and the second transmission gate includes a fifth NMOS tube and a seventh PMOS tube; The gate of the fourth NMOS tube and the gate of the seventh PMOS tube are both connected to the second output end of the first control unit, the gate of the sixth PMOS tube and the gate of the fifth NMOS tube are both connected to the first output end of the first control unit, the drain of the fourth NMOS tube and the drain of the sixth PMOS tube are both connected to the second input end of the voltage subtractor, the drain of the fifth NMOS tube and the drain of the seventh PMOS tube are both connected to the output end of the voltage subtractor, and the source of the fourth NMOS tube, the source of the sixth PMOS tube, the source of the fifth NMOS tube and the source of the seventh PMOS tube are connected to serve as the output end of the over-temperature adaptive module.

[0012] Further, the over-temperature hysteresis shutdown module includes a third positive temperature coefficient voltage generating unit and a second control unit; The first port of the third positive temperature coefficient voltage generating unit and the first port of the second control unit are both connected to the first node, the second port of the third positive temperature coefficient voltage generating unit is connected to the control end of the second control unit, the third port of the third positive temperature coefficient voltage generating unit is connected to the first output end of the second control unit, and the second output end of the second control unit is the output end of the over-temperature hysteresis shutdown module; When the temperature of the LED device When the temperature threshold is exceeded, the first output terminal of the second control unit is at a low level, and the second output terminal of the second control unit is at a high level.

[0013] Further, the third positive temperature coefficient voltage generating unit includes an eighth PMOS tube, a fifth resistor, a sixth resistor and a sixth NMOS tube, and the second control unit includes a ninth PMOS tube, a tenth PMOS tube, an eleventh PMOS tube, a twelfth PMOS tube, a seventh NMOS tube, an eighth NMOS tube, a ninth NMOS tube and a tenth NMOS tube; The source of the eighth PMOS tube, the source of the ninth PMOS tube, the source of the tenth PMOS tube, the source of the eleventh PMOS tube and the source of the twelfth PMOS tube are all connected to the power supply; the gate of the eighth PMOS tube and the gate of the ninth PMOS tube are both connected to the first node, the drain of the eighth PMOS tube is respectively connected to one end of the fifth resistor and the gate of the seventh NMOS tube, and the other end of the fifth resistor is respectively connected to one end of the sixth resistor and the drain of the sixth NMOS tube; the other end of the sixth resistor, the source of the sixth NMOS tube, the source of the seventh NMOS tube, the source of the eighth NMOS tube, the source of the ninth NMOS tube and the source of the tenth NMOS tube are all grounded; The drain of the ninth PMOS tube is connected to the drain of the seventh NMOS tube and then connected to the gate of the tenth PMOS tube and the gate of the eighth NMOS tube respectively; the drain of the tenth PMOS tube is connected to the drain of the eighth NMOS and then connected to the gate of the eleventh PMOS tube and the gate of the ninth NMOS tube respectively; the drain of the eleventh PMOS tube is connected to the drain of the ninth NMOS tube and then connected as the first output end of the second control unit to the gate of the sixth NMOS tube, the gate of the twelfth PMOS tube and the gate of the tenth NMOS tube respectively; the drain of the twelfth PMOS tube is connected to the drain of the tenth NMOS tube and then connected as the second output end of the second control unit; When the temperature of the LED device When the temperature exceeds the threshold, the seventh NMOS tube is turned on, so that the first output terminal of the second control unit is at a low level, and the second output terminal of the second control unit is at a high level.

[0014] Further, the positive temperature coefficient current module includes: a thirteenth PMOS tube, a fourteenth PMOS tube, an eleventh NMOS tube, a twelfth NMOS tube and a seventh resistor; The source of the thirteenth PMOS tube and the source of the fourteenth PMOS tube are both connected to the power supply, the gate of the fourteenth PMOS tube is connected to the gate of the thirteenth PMOS tube, and the gate of the fourteenth PMOS tube is also connected to the drain of the fourteenth PMOS tube at the first node; The gate of the eleventh NMOS tube is respectively connected to the gate of the twelfth NMOS tube, the drain of the eleventh NMOS tube and the drain of the thirteenth PMOS tube, and the source of the eleventh NMOS tube is grounded; the drain of the twelfth NMOS tube is connected to the first node, and the source of the twelfth NMOS tube is grounded through the seventh resistor.

[0015] On the other hand, the present application further provides an LED driving system, which includes an LED device, an LED driving circuit, and an over-temperature protection circuit as described in any one of the aforementioned implementations.

[0016] Compared with the prior art, this application has the following beneficial effects: The present application provides an over-temperature protection circuit and an LED driving system. The over-temperature protection circuit includes: a positive temperature coefficient current module, an over-temperature adaptive module and an over-temperature hysteresis shutdown module. When the over-temperature threshold is reached, the over-temperature adaptive module outputs a reference voltage to the LED drive circuit, so that the LED drive circuit can drive the LED device to work normally under the action of the reference voltage. LED device temperature When the temperature exceeds the threshold, in order to prevent the LED from suddenly turning off due to overheating, the overtemperature adaptive module outputs a negative temperature coefficient voltage to the LED drive circuit that decreases as the temperature rises. The higher the temperature, the weaker the luminous intensity of the LED device. While protecting the LED device, it ensures that the LED device will not turn off immediately, improving driving safety.

[0017] When the temperature of the LED device When the temperature exceeds the threshold, the over-temperature hysteresis shutdown module outputs a shutdown voltage to the LED drive circuit to stop the LED drive circuit from working, thereby increasing the service life and safety factor of the LED device. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians of the art without making creative work are within the scope of protection of the present application.

[0019] Figure 1 It is a circuit diagram of an LED driving circuit in the prior art; Figure 2 A schematic diagram of the structure of an over-temperature protection circuit provided in this application; Figure 3 A circuit diagram of a positive temperature coefficient current module provided in this application; Figure 4A circuit diagram of an over-temperature adaptive module provided in this application; Figure 5 A circuit diagram of an over-temperature hysteresis shutdown module provided in this application; Figure 6 A circuit diagram of an over-temperature protection circuit provided in the present application.

[0020] Figure markings: 10-over-temperature protection circuit; 100-positive temperature coefficient current module; 200-over-temperature adaptive module; 210-first positive temperature coefficient voltage generating unit; 220-voltage subtractor; 230-second positive temperature coefficient voltage generating unit; 240-first control unit; 241-secondary inverter; 250-first transmission gate; 260-second transmission gate; 300-over-temperature hysteresis shutdown module; 310-third positive temperature coefficient voltage generating unit; 320-second control unit. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0022] In the description of this application, it should be noted that relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The term "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0023] As mentioned in the background technology, the current LED driving circuit is Figure 1 As shown. Among them, A is an operational amplifier, NM20 and NM21 are both N-type MOS tubes, PM22 and PM23 are both P-type MOS tubes, R20 is a resistor, D1 and D2 are both LED devices, and They are the driving voltage and the turn-off voltage of the LED driving circuit respectively.

[0024] The non-inverting input of operational amplifier A is connected to the driving voltage , the gate of NM20 is connected to the turn-off voltage The working principle of the entire LED driving circuit is: the driving voltage at the in-phase input terminal is converted to The current is copied to the resistor R20 to generate current, and the current on R20 is mirrored to the LED side through the current mirror composed of PM22 and PM23 to achieve driving.

[0025] When the temperature of the LED device When the over-temperature threshold is reached, the voltage is turned off. The increase makes NM20 turned on. After NM20 is turned on, the gate voltage of NM21 is pulled down and NM28 is turned off, thereby controlling the LED drive circuit to stop working immediately.

[0026] It can be seen that in the current LED drive circuit, is a fixed voltage, as long as the temperature of the LED device Over temperature threshold, The LED driver circuit is controlled to immediately cut off the power supply, thereby protecting the LED device. However, this processing method is not suitable for areas that require continuous lighting, such as car lighting, etc. The sudden power-off processing will affect driving safety and pose a great safety hazard.

[0027] Therefore, how to avoid sudden LED light-off due to overheating while ensuring safety and at the same time increase the service life of the LED is a technical problem that needs to be solved urgently by those skilled in the art.

[0028] To solve the above technical problems, please refer to Figure 2 The embodiment of the present application provides an over-temperature protection circuit 10, which is used to provide a driving voltage and a shut-off voltage for an LED driving circuit, wherein the LED driving circuit is connected to an LED device.

[0029] The over-temperature protection circuit 10 includes: a positive temperature coefficient current module 100, an over-temperature adaptive module 200 and an over-temperature hysteresis shutdown module 300. Among them, the first port of the positive temperature coefficient current module 100, the first port of the over-temperature adaptive module 200 and the first port of the over-temperature hysteresis shutdown module 300 are all connected to the first node N1. The output end of the over-temperature adaptive module 200 is connected to the driving input end P of the LED driving circuit, and the output end of the over-temperature hysteresis shutdown module 300 is connected to the shutdown control end Q of the LED driving circuit.

[0030] The positive temperature coefficient current module 100 is used to provide a positive temperature coefficient current for the over-temperature adaptive module 200 and the over-temperature hysteresis shutdown module 300. The over-temperature hysteresis shutdown module 300 is used to provide a shutdown voltage for the LED drive circuit. The over-temperature adaptive module 200 is used to provide a driving voltage for the LED driving circuit. Among them, the driving voltage Divided into reference voltage and negative temperature coefficient voltage .

[0031] When the temperature of the LED device When the temperature is over the threshold, it means that the temperature of the LED device is normal, and the over-temperature adaptive module 200 outputs a reference voltage to the LED driving circuit. To make the LED drive circuit at the reference voltage Under the action of , the LED device is driven to work normally.

[0032] When the over temperature threshold LED device temperature When the temperature exceeds the threshold, in order to avoid the LED suddenly turning off due to overheating, the overtemperature adaptive module 200 outputs a negative temperature coefficient voltage to the LED driving circuit that decreases as the temperature rises. The higher the temperature, the weaker the luminous intensity of the LED device. This protects the LED device while ensuring that the LED device will not turn off immediately, thus improving driving safety.

[0033] When the temperature of the LED device When the temperature exceeds the threshold, the over-temperature hysteresis shutdown module 300 outputs a shutdown voltage to the LED drive circuit. , so that the LED drive circuit stops working and can only restart working when the temperature of the LED device drops below the over-temperature threshold, thereby improving the service life and safety factor of the LED device.

[0034] Compared with the prior art, the driving voltage output by the over-temperature adaptive module 200 in this application is The voltage value depends on the temperature of the LED device. When the over-temperature threshold is reached, the drive voltage A reference voltage with a constant voltage value When the over temperature threshold LED device temperature When the temperature exceeds the threshold, the drive voltage A negative temperature coefficient voltage whose voltage value decreases as the temperature increases. , thus avoiding the sudden shutdown of the LED caused by overheating and improving driving safety. When the temperature exceeds the threshold, the over-temperature hysteresis shutdown module 300 outputs a high-level shutdown voltage. , to protect the LED devices.

[0035] In order to better understand the driving voltage of this application and shutdown voltage The principle of generation is as follows. The specific circuit structures of the positive temperature coefficient current module 100, the over-temperature adaptive module 200 and the over-temperature hysteresis shutdown module 300 will be described in turn.

[0036] The circuit structure of the positive temperature coefficient current module 100 is as follows: Figure 3 As shown, in the embodiment of the present application, the positive temperature coefficient current module 100 includes: a thirteenth PMOS transistor PM13, a fourteenth PMOS transistor PM14, an eleventh NMOS transistor NM11, a twelfth NMOS transistor NM12 and a seventh resistor R7.

[0037] Among them, the source of the thirteenth PMOS transistor PM13 and the source of the fourteenth PMOS transistor PM14 are both connected to the power supply VDD, the gate of the fourteenth PMOS transistor PM14 is connected to the gate of the thirteenth PMOS transistor PM13, and the gate of the fourteenth PMOS transistor PM14 is also connected to the drain of the fourteenth PMOS transistor PM14 to the first node N1. The gate of the eleventh NMOS transistor NM11 is respectively connected to the gate of the twelfth NMOS transistor NM12, the drain of the eleventh NMOS transistor NM11 and the drain of the thirteenth PMOS transistor PM13, and the source of the eleventh NMOS transistor NM11 is grounded. The drain of the twelfth NMOS transistor NM12 is connected to the first node N1, and the source of the twelfth NMOS transistor NM12 is grounded through the seventh resistor R7.

[0038] The drain of the fourteenth PMOS transistor PM14 in the positive temperature coefficient current module 100 generates a positive temperature coefficient current that increases with increasing temperature. , thereby providing a reference current for the subsequent over-temperature adaptive module 200 and the over-temperature hysteresis shutdown module 300 .

[0039] The circuit structure of the over-temperature adaptive module 200 is as follows: Figure 4 As shown, in the embodiment of the present application, the over-temperature adaptive module 200 includes: a first positive temperature coefficient voltage generating unit 210, a voltage subtractor 220, a second positive temperature coefficient voltage generating unit 230, a first control unit 240, a first transmission gate 250 and a second transmission gate 260.

[0040] The first port of the first positive temperature coefficient voltage generating unit 210 is connected to the first node N1, the second port C of the first positive temperature coefficient voltage generating unit 210 is connected to the first input terminal of the voltage subtractor 220, and the second input terminal of the voltage subtractor 220 is connected to the reference voltage. The output terminal of the voltage subtractor 220 outputs a negative temperature coefficient voltage .

[0041] The first port of the second PTCC voltage generating unit 230 and the first port of the first control unit 240 are both connected to the first node N1 , and the second port D of the second PTCC voltage generating unit 230 is connected to the control terminal of the first control unit 240 .

[0042] The first port of the first transmission gate 250 and the second port of the second transmission gate 260 are both connected to the second output terminal F of the first control unit 240, and the second port of the first transmission gate 250 and the first port of the second transmission gate 260 are both connected to the first output terminal E of the first control unit 240. The third port of the first transmission gate 250 is connected to the second input terminal of the voltage subtractor 220, and the third port of the second transmission gate 260 is connected to the output terminal of the voltage subtractor 220. The fourth port of the first transmission gate 250 and the fourth port of the second transmission gate 260 are connected as the output terminal of the over-temperature adaptive module 200, which is used to output the driving voltage .

[0043] When the temperature of the LED device When the over-temperature threshold is reached, the first output terminal E of the first control unit 240 is at a low level, the second output terminal F of the first control unit 240 is at a high level, the first transmission gate 250 is turned on, the second transmission gate 260 is turned off, and the over-temperature adaptive module 200 outputs a reference voltage ,Right now = .

[0044] When the over temperature threshold LED device temperature When the temperature exceeds the threshold, the first output terminal E of the first control unit 240 is high, the second output terminal F of the first control unit 240 is low, the first transmission gate 250 is turned off, the second transmission gate 260 is turned on, and the over-temperature adaptive module 200 outputs a negative temperature coefficient voltage ,Right now = .

[0045] Specifically, the first positive temperature coefficient voltage generating unit 210 includes a first PMOS transistor PM1 and a first resistor R1 , and the voltage subtractor 220 includes a second resistor R2 , a third resistor R3 and an operational amplifier A1 .

[0046] Among them, the source of the first PMOS tube PM1 is connected to the power supply VDD, the gate of the first PMOS tube PM1 (that is, the first port of the first positive temperature coefficient voltage generating unit 210) is connected to the first node N1, the drain of the first PMOS tube PM1 is respectively connected to one end of the first resistor R1 and one end of the second resistor R2, and the other end of the first resistor R1 is grounded.

[0047] The other end of the second resistor R2 is connected to the inverting input terminal of the operational amplifier A1 and one end of the third resistor R3 respectively. The other end of the third resistor R3 is connected to the output terminal of the operational amplifier A1. The non-inverting input terminal of the operational amplifier A1 is connected to the reference voltage. .

[0048] It should be noted that the first PMOS transistor PM1 and the fourteenth PMOS transistor PM14 in the positive temperature coefficient current module 100 form a pair of current mirrors. The positive temperature coefficient current can be converted to The first resistor R1 is copied to the first resistor R1, which converts the positive temperature coefficient current Converted to positive temperature coefficient voltage and is input to the inverting input terminal of the operational amplifier A1 through the second resistor R2, so that the operational amplifier A1 outputs a negative temperature coefficient voltage that decreases as the temperature increases under the action of the second resistor R2 and the third resistor R3. .

[0049] Further, the second positive temperature coefficient voltage generating unit 230 includes a second PMOS transistor PM2 and a fourth resistor R4 , and the first control unit 240 includes a third PMOS transistor PM3 , a first NMOS transistor NM1 and a secondary inverter 241 .

[0050] The source of the second PMOS transistor PM2, the source of the third PMOS transistor PM3 and the first port of the secondary inverter 241 are all connected to the power supply VDD. The gate of the second PMOS transistor PM2 (i.e., the first port of the second positive temperature coefficient voltage generating unit 230) and the gate of the third PMOS transistor PM3 (i.e., the first port of the first control unit 240) are all connected to the first node N1. The drain of the second PMOS transistor PM2 is respectively connected to one end of the fourth resistor R4 and the gate of the first NMOS transistor NM1, and the other end of the fourth resistor R4, the source of the first NMOS transistor NM1 and the second port of the secondary inverter 241 are all grounded.

[0051] The drain of the first NMOS transistor NM1 is respectively connected to the drain of the third PMOS transistor PM3 and the input end of the secondary inverter 241, the first output end E of the secondary inverter 241 (i.e., the first output end E of the first control unit 240) is respectively connected to the second port of the first transmission gate 250 and the first port of the second transmission gate 260, and the second output end F of the secondary inverter 241 (i.e., the second output end F of the first control unit 240) is respectively connected to the first port of the first transmission gate 250 and the second port of the second transmission gate 260.

[0052] It should be noted that the first PMOS tube PM1, the second PMOS tube PM2 and the third PMOS tube PM3 in the over-temperature adaptive module 200 respectively form three pairs of current mirrors with the fourteenth PMOS tube PM14 in the positive temperature coefficient current module 100. The first PMOS tube PM1, the second PMOS tube PM2 and the third PMOS tube PM3 respectively convert the positive temperature coefficient current at the drain of the fourteenth PMOS tube PM14 The transistor is copied to the drains of the first PMOS transistor PM1 , the second PMOS transistor PM2 , and the third PMOS transistor PM3 .

[0053] When the temperature of the LED device When the temperature is over the threshold, the first NMOS transistor NM1 is turned off, the first output terminal E of the secondary inverter 241 is at a low level, and the second output terminal F of the secondary inverter 241 is at a high level.

[0054] When the over temperature threshold LED device temperature When the temperature threshold is exceeded, the first NMOS transistor NM1 is turned on, the first output terminal E of the secondary inverter 241 is at a high level, and the second output terminal F of the secondary inverter 241 is at a low level.

[0055] As an optional implementation, the two-stage inverter 241 includes a fourth PMOS transistor PM4, a fifth PMOS transistor PM5, a second NMOS transistor NM2 and a third NMOS transistor NM3.

[0056] The source of the fourth PMOS transistor PM4 and the source of the fifth PMOS transistor PM5 are both connected to the power supply VDD, and the source of the second NMOS transistor NM2 and the source of the third NMOS transistor NM3 are both grounded.

[0057] The gate of the fourth PMOS transistor PM4 and the gate of the second NMOS transistor NM2 are both connected to the drain of the first NMOS transistor NM1. The drain of the fourth PMOS transistor PM4 and the drain of the second NMOS transistor NM2 are connected as the first output terminal E of the secondary inverter 241, and are respectively connected to the second port of the first transmission gate 250, the first port of the second transmission gate 260, the gate of the fifth PMOS transistor PM5, and the gate of the third NMOS transistor NM3. The drain of the fifth PMOS transistor PM5 and the drain of the third NMOS transistor NM3 are connected as the second output terminal F of the secondary inverter 241.

[0058] Further, the first transmission gate 250 includes a fourth NMOS transistor NM4 and a sixth PMOS transistor PM6 , and the second transmission gate 260 includes a fifth NMOS transistor NM5 and a seventh PMOS transistor PM7 .

[0059] The gates of the fourth NMOS transistor NM4 and the seventh PMOS transistor PM7 are connected to the second output terminal F of the first control unit 240 , and the gates of the sixth PMOS transistor PM6 and the fifth NMOS transistor NM5 are connected to the first output terminal E of the first control unit 240 .

[0060] The drain of the fourth NMOS tube NM4 and the drain of the sixth PMOS tube PM6 are both connected to the second input terminal of the voltage subtractor 220 (equivalent to the drain of the fourth NMOS tube NM4 and the drain of the sixth PMOS tube PM6 being connected to the reference voltage ), the drain of the fifth NMOS tube NM5 and the drain of the seventh PMOS tube PM7 are both connected to the output end of the voltage subtractor 220 (equivalent to the drain of the fifth NMOS tube NM5 and the drain of the seventh PMOS tube PM7 are both connected to the negative temperature coefficient voltage ).

[0061] The source of the fourth NMOS transistor NM4 , the source of the sixth PMOS transistor PM6 , the source of the fifth NMOS transistor NM5 , and the source of the seventh PMOS transistor PM7 are connected to serve as the output end of the over-temperature adaptive module 200 .

[0062] The circuit structure of the over-temperature hysteresis shutdown module 300 is as follows: Figure 5 As shown, in the embodiment of the present application, the over-temperature hysteresis shutdown module 300 includes: a third positive temperature coefficient voltage generating unit 310 and a second control unit 320 .

[0063] The first port of the third positive temperature coefficient voltage generating unit 310 and the first port of the second control unit 320 are both connected to the first node N1. The second port A of the third positive temperature coefficient voltage generating unit 310 is connected to the control end of the second control unit 320, and the third port of the third positive temperature coefficient voltage generating unit 310 is connected to the first output end B of the second control unit 320. The second output end of the second control unit 320 is the output end of the over-temperature hysteresis shutdown module 300.

[0064] When the temperature of the LED device When the temperature exceeds the threshold, the first output terminal B of the second control unit 320 is at a low level, and the second output terminal of the second control unit 320 is at a high level (ie, the over-temperature hysteresis shutdown module 300 outputs a high level shutdown voltage). ).

[0065] Specifically, the third positive temperature coefficient voltage generating unit 310 includes: an eighth PMOS transistor PM8, a fifth resistor R5, a sixth resistor R6 and a sixth NMOS transistor NM6. The second control unit 320 includes: a ninth PMOS transistor PM9, a tenth PMOS transistor PM10, an eleventh PMOS transistor PM11, a twelfth PMOS transistor PM12, a seventh NMOS transistor NM7, an eighth NMOS transistor NM8, a ninth NMOS transistor NM9 and a tenth NMOS transistor NM10.

[0066] Among them, the source of the eighth PMOS transistor PM8 , the source of the ninth PMOS transistor PM9 , the source of the tenth PMOS transistor PM10 , the source of the eleventh PMOS transistor PM11 and the source of the twelfth PMOS transistor PM12 are all connected to the power supply VDD.

[0067] The gate of the eighth PMOS transistor PM8 (i.e., the first port of the third positive temperature coefficient voltage generating unit 310) and the gate of the ninth PMOS transistor PM9 (i.e., the first port of the second control unit 320) are both connected to the first node N1 (i.e., the eighth PMOS transistor PM8 and the ninth PMOS transistor PM9 respectively form two pairs of current mirrors with the fourteenth PMOS transistor PM14). The drain of the eighth PMOS transistor PM8 is respectively connected to one end of the fifth resistor R5 and the gate of the seventh NMOS transistor NM7, and the other end of the fifth resistor R5 is respectively connected to one end of the sixth resistor R6 and the drain of the sixth NMOS transistor NM6. The other end of the sixth resistor R6, the source of the sixth NMOS transistor NM6, the source of the seventh NMOS transistor NM7, the source of the eighth NMOS transistor NM8, the source of the ninth NMOS transistor NM9, and the source of the tenth NMOS transistor NM10 are all grounded.

[0068] The drain of the ninth PMOS transistor PM9 is connected to the drain of the seventh NMOS transistor NM7 and then connected to the gate of the tenth PMOS transistor PM10 and the gate of the eighth NMOS transistor NM8 respectively. The drain of the tenth PMOS and the drain of the eighth NMOS are connected to the gate of the eleventh PMOS transistor PM11 and the gate of the ninth NMOS transistor NM9 respectively. The drain of the eleventh PMOS transistor PM11 and the drain of the ninth NMOS transistor NM9 are connected as the first output terminal B of the second control unit 320 and then connected to the gate of the sixth NMOS transistor NM6 (i.e., the third port of the third positive temperature coefficient voltage generating unit 310), the gate of the twelfth PMOS transistor PM12 and the gate of the tenth NMOS transistor NM10 respectively. The drain of the twelfth PMOS transistor PM12 and the drain of the tenth NMOS transistor NM10 are connected as the second output terminal of the second control unit 320.

[0069] When the temperature of the LED device When the temperature exceeds the threshold, the seventh NMOS transistor NM7 is turned on, so that the first output terminal B of the second control unit 320 is at a low level, and the second output terminal of the second control unit 320 is at a high level.

[0070] Based on the above design, the following Figure 6 The overall working principle of the over-temperature protection circuit 10 provided in the present application is explained.

[0071] In the positive temperature coefficient current module 100, PM13 and PM14 form a pair of current mirrors, and NM11 and NM12 form a pair of current mirrors. In addition, PM13 and PM14 have the same width-to-length ratio (ie, the MOS tubes have the same size), and NM11 and NM12 have a width-to-length ratio of 1: , from which we can get the following formula: (1) Right now: (2) in, is the gate-source voltage of NM11, is the gate-source voltage of NM12, is the threshold voltage of NM11, is the threshold voltage of NM12, is the drain current of NM11, is the drain current of NM12, is the width-to-length ratio of NM11, is the electron mobility of the MOS tube, It is the process constant of MOS tube.

[0072] From the current mirror relationship and MOS tube technology, we can know that: = = = , = .

[0073] So we can get: (1 )= 7 (3) Right now: (4) in: (5) In formula (5) is T= The electron mobility at , m is the temperature constant, and is substituted into formula (4) to obtain: (6) According to formula (6), the PM14 drain generates It is the current that increases with the increase of temperature T.

[0074] In the over-temperature adaptive module 200, PM1, PM2, PM3 and PM14 in the positive temperature coefficient current module 100 form three pairs of current mirrors. PM4 and NM2 form an inverter, PM5 and NM3 form an inverter. NM4 and PM6 form a group of transmission gates, and NM5 and PM7 form a group of transmission gates. The specific working principle is as follows: PM1 Copy To R1 branch (the width-to-length ratio of PM14 to PM1 is 1): ), a PTAT (positive temperature coefficient) voltage is generated on R1 : (7) R2, R3 and A1 form a voltage subtractor. The inverting input of A1 is a PTAT voltage generated by the voltage divider of R2 and R3, and the non-inverting input of A1 is the reference voltage. , the output voltage of A1 is , the calculation formula is as follows: (8) Because the temperature coefficients of R2 and R3 are the same, is a temperature-independent reference voltage. is a voltage that is positively correlated with temperature, so and Subtracting the voltage will give a voltage that is negatively correlated with temperature. .

[0075] PM2 Copy To R4 branch (the width-to-length ratio of PM14 to PM2 is 1: ), a PTAT voltage is generated on R4 , Control the on and off of NM1 to achieve temperature judgment.

[0076] When the temperature of the LED device Over temperature threshold, It is not enough to turn on NM1, so the inverter output point E is low level, point F is high level, NM4 and PM6 are turned on, NM5 and PM7 are turned off. The output value is .

[0077] When the over temperature threshold LED device temperature When the temperature exceeds the threshold, Greater than the threshold voltage of NM1 , NM1 is turned on, so the inverter output point E is high level, point F is low level, NM4 and PM6 are turned off, NM5 and PM7 are turned on, at this time The output value is .

[0078] In the over-temperature hysteresis shutdown module 300, when the temperature of the LED device When the temperature exceeds the threshold, NM7, which acts as a switch tube, is turned on, causing the module to output a high level and stop the subsequent circuits from working.

[0079] PM8 and PM9 form two pairs of current mirrors with PM14 in the positive temperature coefficient current module 100. To the branch formed by R5 and R6 in series (the width-to-length ratio of PM14 to PM8 is 1: ), generates a PTAT voltage, which controls the on and off of NM7 to achieve temperature judgment. PM9 Copy To the branch where NM7 is located (the width-to-length ratio of PM14 to PM9 is 1: ), provides bias current for this branch.

[0080] PM10 and NM8, PM11 and NM9, PM12 and NM10 form three inverters respectively, and NM7 is the switch tube control The output level is high. NM6 implements hysteresis shutdown function to prevent the circuit from thermal oscillation at the shutdown point. The specific working principle is as follows: When the temperature of the LED device Over temperature threshold When the LED drive circuit works normally, Output low level, NM6 is turned on, R6 is short-circuited, then: (9) When the temperature of the LED device rises to just equal hour, Greater than the threshold voltage of NM7 Make NM7 conduction, Output high level to stop the LED driving circuit and turn off NM6.

[0081] Right now: (10) Will Substituting expression (6) into equation (10) yields: (11) make = After finishing, we can get: (12) LED device temperature Over temperature threshold When NM6 is turned off, the gate voltage of NM7 is 5 and 6 provides, at this time there are: (13) The temperature of the LED device drops to the over-temperature threshold The following makes the circuit start working normally again, Requires a threshold voltage lower than NM7 Turn off NM7, and according to the equation, we can calculate: (14) That is, the maximum temperature in the temperature hysteresis range is , the minimum temperature is , by changing 5 and The size of 6 can adjust the size of the hysteresis interval. For example, if the over-temperature threshold is set to 125°C and the over-temperature threshold (i.e., the restart working temperature) is set to 75°C, then =125℃, =75℃, which can be calculated from equations (12) and (14): 5 and The resistance value of 6.

[0082] Furthermore, the embodiment of the present application also provides an LED driving system, which includes an LED device, an LED driving circuit, and an over-temperature protection circuit 10 as described in any one of the above embodiments.

[0083] In summary, the embodiment of the present application provides an over-temperature protection circuit and an LED driving system. The over-temperature protection circuit includes: a positive temperature coefficient current module, an over-temperature adaptive module and an over-temperature hysteresis shutdown module. Among them, the positive temperature coefficient current module is used to provide a positive temperature coefficient current for the over-temperature adaptive module and the over-temperature hysteresis shutdown module. When the temperature of the LED device When the over-temperature threshold is reached, the over-temperature adaptive module outputs a reference voltage to the LED drive circuit. LED device temperature When the temperature exceeds the threshold, in order to prevent the LED from suddenly turning off due to overheating, the overtemperature adaptive module outputs a negative temperature coefficient voltage to the LED drive circuit that decreases as the temperature rises. The higher the temperature, the weaker the luminous intensity of the LED device. While protecting the LED device, it ensures that the LED device will not turn off immediately, improving driving safety.

[0084] When the temperature of the LED device When the temperature exceeds the threshold, the over-temperature hysteresis shutdown module outputs a shutdown voltage to the LED drive circuit to stop the LED drive circuit from working until the temperature of the LED device drops below the over-temperature threshold, thereby increasing the service life and safety factor of the LED device.

[0085] Compared with the prior art, the voltage value of the driving voltage output by the over-temperature adaptive module in the present application depends on the temperature of the LED device. When the over-temperature threshold is reached, the driving voltage is a reference voltage with a constant voltage value. LED device temperature When the temperature exceeds the threshold, the driving voltage is a negative temperature coefficient voltage whose voltage value decreases as the temperature rises, thereby avoiding the sudden shutdown of the LED due to overheating and improving driving safety. When the temperature exceeds the threshold, the over-temperature hysteresis shutdown module outputs a high-level shutdown voltage to protect the LED device.

[0086] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0087] It will be apparent to those skilled in the art that the present application is not limited to the details of the exemplary embodiments described above, and that the present application can be implemented in other specific forms without departing from the spirit or essential features of the present application. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the present application is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present application. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. An over-temperature protection circuit, used for providing a driving voltage and a shutdown voltage for an LED driving circuit, wherein the LED driving circuit is connected to an LED device, characterized in that: The over-temperature protection circuit comprises: a positive temperature coefficient current module, an over-temperature adaptive module and an over-temperature hysteresis shutdown module; The first port of the positive temperature coefficient current module, the first port of the over-temperature adaptive module and the first port of the over-temperature hysteresis shutdown module are all connected to a first node, the output end of the over-temperature adaptive module is connected to the driving input end of the LED driving circuit, and the output end of the over-temperature hysteresis shutdown module is connected to the shutdown control end of the LED driving circuit; The positive temperature coefficient current module is used to provide a positive temperature coefficient current for the over-temperature adaptive module and the over-temperature hysteresis shutdown module; When the temperature of the LED device When the over-temperature threshold is reached, the over-temperature adaptive module is used to output a reference voltage to the LED driving circuit; When the over temperature threshold LED device temperature When the temperature exceeds the threshold, the over-temperature adaptive module is used to output a negative temperature coefficient voltage to the LED driving circuit that decreases as the temperature increases; When the temperature of the LED device When the temperature exceeds the threshold value, the over-temperature hysteresis shutdown module is used to output a shutdown voltage to the LED driving circuit to stop the LED driving circuit from working.

2. The over-temperature protection circuit according to claim 1, characterized in that: The over-temperature adaptive module includes: a first positive temperature coefficient voltage generating unit, a voltage subtractor, a second positive temperature coefficient voltage generating unit, a first control unit, a first transmission gate and a second transmission gate; The first port of the first positive temperature coefficient voltage generating unit is connected to the first node, the second port of the first positive temperature coefficient voltage generating unit is connected to the first input terminal of the voltage subtractor, the second input terminal of the voltage subtractor is connected to the reference voltage, and the output terminal of the voltage subtractor outputs a negative temperature coefficient voltage; The first port of the second positive temperature coefficient voltage generating unit and the first port of the first control unit are both connected to the first node, and the second port of the second positive temperature coefficient voltage generating unit is connected to the control terminal of the first control unit; The first port of the first transmission gate and the second port of the second transmission gate are both connected to the second output end of the first control unit, the second port of the first transmission gate and the first port of the second transmission gate are both connected to the first output end of the first control unit, the third port of the first transmission gate is connected to the second input end of the voltage subtractor, the third port of the second transmission gate is connected to the output end of the voltage subtractor, and the fourth port of the first transmission gate and the fourth port of the second transmission gate are connected to serve as the output end of the over-temperature adaptive module; When the temperature of the LED device At the over-temperature threshold, the first output terminal of the first control unit is at a low level, the second output terminal of the first control unit is at a high level, the first transmission gate is turned on, the second transmission gate is turned off, and the over-temperature adaptive module outputs a reference voltage; When the over temperature threshold LED device temperature When the temperature threshold is exceeded, the first output terminal of the first control unit is at a high level, the second output terminal of the first control unit is at a low level, the first transmission gate is turned off, the second transmission gate is turned on, and the over-temperature adaptive module outputs a negative temperature coefficient voltage.

3. The over-temperature protection circuit according to claim 2, characterized in that: The first positive temperature coefficient voltage generating unit includes a first PMOS tube and a first resistor, and the voltage subtractor includes a second resistor, a third resistor and an operational amplifier; The source of the first PMOS tube is connected to a power supply, the gate of the first PMOS tube is connected to the first node, the drain of the first PMOS tube is respectively connected to one end of the first resistor and one end of the second resistor, and the other end of the first resistor is grounded; The other end of the second resistor is connected to the inverting input terminal of the operational amplifier and one end of the third resistor respectively, the other end of the third resistor is connected to the output terminal of the operational amplifier, and the non-inverting input terminal of the operational amplifier is connected to a reference voltage.

4. The over-temperature protection circuit according to claim 2, characterized in that: The second positive temperature coefficient voltage generating unit includes a second PMOS tube and a fourth resistor, and the first control unit includes a third PMOS tube, a first NMOS tube and a secondary inverter; The source of the second PMOS tube, the source of the third PMOS tube and the first port of the secondary inverter are all connected to a power supply, the gate of the second PMOS tube and the gate of the third PMOS tube are both connected to the first node, the drain of the second PMOS tube is respectively connected to one end of the fourth resistor and the gate of the first NMOS tube, and the other end of the fourth resistor, the source of the first NMOS tube and the second port of the secondary inverter are all grounded; The drain of the first NMOS tube is connected to the drain of the third PMOS tube and the input end of the secondary inverter respectively, the first output end of the secondary inverter is connected to the second port of the first transmission gate and the first port of the second transmission gate respectively, and the second output end of the secondary inverter is connected to the first port of the first transmission gate and the second port of the second transmission gate respectively; When the temperature of the LED device When the temperature is over the threshold, the first NMOS tube is turned off, the first output end of the secondary inverter is at a low level, and the second output end of the secondary inverter is at a high level; When the over temperature threshold LED device temperature When the temperature threshold is exceeded, the first NMOS tube is turned on, the first output end of the secondary inverter is at a high level, and the second output end of the secondary inverter is at a low level.

5. The over-temperature protection circuit according to claim 4, characterized in that: The secondary inverter includes a fourth PMOS tube, a fifth PMOS tube, a second NMOS tube and a third NMOS tube; The source of the fourth PMOS tube and the source of the fifth PMOS tube are both connected to a power supply, and the source of the second NMOS tube and the source of the third NMOS tube are both grounded; The gate of the fourth PMOS tube and the gate of the second NMOS tube are both connected to the drain of the first NMOS tube. The drain of the fourth PMOS tube and the drain of the second NMOS tube are connected and then serve as the first output end of the secondary inverter and are respectively connected to the second port of the first transmission gate, the first port of the second transmission gate, the gate of the fifth PMOS tube and the gate of the third NMOS tube. The drain of the fifth PMOS tube and the drain of the third NMOS tube are connected and then serve as the second output end of the secondary inverter.

6. The over-temperature protection circuit according to claim 2, characterized in that: The first transmission gate includes a fourth NMOS tube and a sixth PMOS tube, and the second transmission gate includes a fifth NMOS tube and a seventh PMOS tube; The gate of the fourth NMOS tube and the gate of the seventh PMOS tube are both connected to the second output end of the first control unit, the gate of the sixth PMOS tube and the gate of the fifth NMOS tube are both connected to the first output end of the first control unit, the drain of the fourth NMOS tube and the drain of the sixth PMOS tube are both connected to the second input end of the voltage subtractor, the drain of the fifth NMOS tube and the drain of the seventh PMOS tube are both connected to the output end of the voltage subtractor, and the source of the fourth NMOS tube, the source of the sixth PMOS tube, the source of the fifth NMOS tube and the source of the seventh PMOS tube are connected to serve as the output end of the over-temperature adaptive module.

7. The over-temperature protection circuit according to claim 1, characterized in that: The over-temperature hysteresis shutdown module includes a third positive temperature coefficient voltage generating unit and a second control unit; The first port of the third positive temperature coefficient voltage generating unit and the first port of the second control unit are both connected to the first node, the second port of the third positive temperature coefficient voltage generating unit is connected to the control end of the second control unit, the third port of the third positive temperature coefficient voltage generating unit is connected to the first output end of the second control unit, and the second output end of the second control unit is the output end of the over-temperature hysteresis shutdown module; When the temperature of the LED device When the temperature threshold is exceeded, the first output terminal of the second control unit is at a low level, and the second output terminal of the second control unit is at a high level.

8. The over-temperature protection circuit according to claim 7, characterized in that: The third positive temperature coefficient voltage generating unit includes an eighth PMOS tube, a fifth resistor, a sixth resistor and a sixth NMOS tube, and the second control unit includes a ninth PMOS tube, a tenth PMOS tube, an eleventh PMOS tube, a twelfth PMOS tube, a seventh NMOS tube, an eighth NMOS tube, a ninth NMOS tube and a tenth NMOS tube; The source of the eighth PMOS tube, the source of the ninth PMOS tube, the source of the tenth PMOS tube, the source of the eleventh PMOS tube and the source of the twelfth PMOS tube are all connected to the power supply; the gate of the eighth PMOS tube and the gate of the ninth PMOS tube are both connected to the first node, the drain of the eighth PMOS tube is respectively connected to one end of the fifth resistor and the gate of the seventh NMOS tube, and the other end of the fifth resistor is respectively connected to one end of the sixth resistor and the drain of the sixth NMOS tube; the other end of the sixth resistor, the source of the sixth NMOS tube, the source of the seventh NMOS tube, the source of the eighth NMOS tube, the source of the ninth NMOS tube and the source of the tenth NMOS tube are all grounded; The drain of the ninth PMOS tube is connected to the drain of the seventh NMOS tube and then connected to the gate of the tenth PMOS tube and the gate of the eighth NMOS tube respectively; the drain of the tenth PMOS tube is connected to the drain of the eighth NMOS and then connected to the gate of the eleventh PMOS tube and the gate of the ninth NMOS tube respectively; the drain of the eleventh PMOS tube is connected to the drain of the ninth NMOS tube and then connected as the first output end of the second control unit to the gate of the sixth NMOS tube, the gate of the twelfth PMOS tube and the gate of the tenth NMOS tube respectively; the drain of the twelfth PMOS tube is connected to the drain of the tenth NMOS tube and then connected as the second output end of the second control unit; When the temperature of the LED device When the temperature exceeds the threshold, the seventh NMOS tube is turned on, so that the first output terminal of the second control unit is at a low level, and the second output terminal of the second control unit is at a high level.

9. The over-temperature protection circuit according to claim 1, characterized in that: The positive temperature coefficient current module includes: a thirteenth PMOS tube, a fourteenth PMOS tube, an eleventh NMOS tube, a twelfth NMOS tube and a seventh resistor; The source of the thirteenth PMOS tube and the source of the fourteenth PMOS tube are both connected to the power supply, the gate of the fourteenth PMOS tube is connected to the gate of the thirteenth PMOS tube, and the gate of the fourteenth PMOS tube is also connected to the drain of the fourteenth PMOS tube at the first node; The gate of the eleventh NMOS tube is respectively connected to the gate of the twelfth NMOS tube, the drain of the eleventh NMOS tube and the drain of the thirteenth PMOS tube, and the source of the eleventh NMOS tube is grounded; the drain of the twelfth NMOS tube is connected to the first node, and the source of the twelfth NMOS tube is grounded through the seventh resistor.

10. An LED driving system, characterized in that: The LED driving system comprises an LED device, an LED driving circuit and an over-temperature protection circuit as claimed in any one of claims 1 to 9.

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