Over-temperature protection circuit and load driving system

Abstract

The invention provides an over-temperature protection circuit and a load driving system. The over-temperature protection circuit comprises a signal sampling module, a differential amplification module and a difference calculation module. The signal sampling module is used for accessing a reference signal and a sampling signal; the differential amplification module is connected with the signal sampling module, and the differential amplification module generates a differential signal based on the reference signal and the sampling signal; and the difference calculation module is connected with the signal sampling module, the differential amplification module and the driving circuit, calculates a difference signal based on the reference signal and the differential signal, and outputs the difference signal to the driving circuit, so that the driving circuit drives a load based on the difference signal. According to the over-temperature protection circuit, the working current of the load can be correspondingly changed based on the changing difference signal, so that the purpose of over-temperature protection of the load is achieved, the operation reliability of the load is guaranteed, and the over-temperature protection circuit is low in power consumption and manufacturing cost, small in size and high in adaptability.

Description

Technical Field

[0001] The present application relates to the technical field of LED driving, and more specifically, to an over-temperature protection circuit and a load driving system. Background Art

[0002] High-power light emitting diodes (LEDs) are widely used in various fields due to their high brightness, high efficiency and long life. LEDs generate a lot of heat during operation. In order to prevent LEDs from being damaged by overheating, a microcontroller unit (MCU) is usually provided in the relevant technology. The MCU detects the temperature of the LED in real time and derates the LED for protection when the temperature is too high.

[0003] However, MCUs usually integrate multiple functions. If they only implement the derating function, there will be a certain waste of resources, and the cost and size of the MCU will be high. Summary of the invention

[0004] To solve the above problems, the present application provides an over-temperature protection circuit and a load drive system, aiming to solve the problems of high cost, large size and certain resource waste when the related technology uses MCU to perform derating protection on LEDs.

[0005] In a first aspect, the present application provides an over-temperature protection circuit for a load driving system, wherein the load driving system includes a load and a driving circuit, and the over-temperature protection system includes a signal sampling module, a differential amplification module, and a difference calculation module; the signal sampling module is used to access a reference signal and a sampling signal, wherein the sampling signal is a signal corresponding to the temperature of the collected load; the differential amplification module is connected to the signal sampling module, and the differential amplification module is used to access the reference signal and the sampling signal output by the signal sampling module, and generate a differential signal based on the reference signal and the sampling signal; the difference calculation module is connected to the signal sampling module, the differential amplification module, and the driving circuit, and the difference calculation module is used to access the reference signal and the differential signal, and calculate the difference signal based on the reference signal and the differential signal and output it to the driving circuit, so that the driving circuit drives the load based on the difference signal.

[0006] In the above technical solution, the differential amplifier module can obtain a corresponding differential signal based on a fixed reference signal and a changing sampling signal, and the difference calculation module can calculate the corresponding difference signal based on the fixed reference signal and the changing differential signal, that is, the difference signal is also a changing value. The driving circuit can change the working current of the load correspondingly based on the changing difference signal to achieve the purpose of over-temperature protection of the load and ensure the operating reliability of the load. Among them, the differential amplifier module and the difference calculation module can calculate the corresponding difference signal based on the changing sampling signal, that is, the size of the difference signal can be changed correspondingly through the hardware circuit, thereby correspondingly changing the working current of the load, without setting up additional MCU or other controllers to perform software monitoring and control on the load, avoiding the problem of waste of resources. Secondly, compared with the MCU in the related art, the over-temperature protection circuit provided by the present application has lower power consumption and production cost, smaller size, and higher adaptability.

[0007] In combination with the first aspect, in some possible implementations, the differential amplification module includes a first acquisition unit, a second acquisition unit and a first operational amplifier; the first end of the first acquisition unit is connected to the signal sampling module for accessing a reference signal, and the second end of the first acquisition unit is grounded; the first end of the second acquisition unit is connected to the signal sampling module for accessing a sampling signal; the non-inverting input end of the first operational amplifier is connected to the third end of the first acquisition unit, the inverting input end of the operational amplifier is connected to the second end of the second acquisition unit, the output end of the first operational amplifier is connected to the third end of the second acquisition unit and the difference calculation module, and the first operational amplifier is used to generate the differential signal based on the reference signal and the sampling signal, and output it to the difference calculation module.

[0008] In the above technical solution, the first acquisition unit, the second acquisition unit and the first operational amplifier constitute a differential amplifier, which can detect slight changes in the signal, that is, the first operational amplifier can detect slight changes in the sampling signal in a timely manner, and output a corresponding differential signal based on the changing sampling signal and the fixed reference signal, and the detection and output reliability and accuracy are high. Secondly, the first operational amplifier can well suppress the signal (i.e., the common mode signal) that exists in both input terminals to improve the signal-to-noise ratio and reduce interference noise.

[0009] In combination with the first aspect and the above-mentioned implementation methods, in some possible implementation methods, the first acquisition unit includes a first resistor and a second resistor; one end of the first resistor is connected to the signal sampling module; one end of the second resistor is connected to the other end of the first resistor and the in-phase input terminal of the first operational amplifier, and the other end of the second resistor is grounded.

[0010] In the above technical solution, the first resistor will divide the connected reference voltage and output it to the non-inverting input terminal of the first operational amplifier, and the first resistor will form a voltage divider network with the second resistor to adjust the actual voltage level input to the non-inverting input terminal of the first operational amplifier, thereby changing the gain setting. In this way, based on the needs of different loads, the ratio of the second resistor to the first resistor can be flexibly set to change the gain to adapt to the changing needs of the VDSET target curve of different loads, thereby ensuring the protection accuracy of the over-temperature protection circuit, and the applicability is high.

[0011] In combination with the first aspect and the above-mentioned implementation methods, in some possible implementation methods, the second acquisition unit includes a third resistor and a fourth resistor; one end of the third resistor is connected to the signal sampling module; one end of the fourth resistor is connected to the other end of the third resistor and the inverting input terminal of the first operational amplifier, and the other end of the fourth resistor is connected to the output terminal of the first operational amplifier; wherein the resistance value of the third resistor is the same as the resistance value of the first resistor, and the resistance value of the fourth resistor is equal to the resistance value of the second resistor.

[0012] In the above technical solution, the third resistor divides the input sampling signal and outputs it to the inverting input terminal of the first operational amplifier. The fourth resistor, as part of the feedback path, controls the amount of signal returning from the output terminal of the first operational amplifier to the inverting input terminal of the first operational amplifier to directly affect the closed-loop gain of the circuit. In order to obtain an accurate proportional relationship, the resistance value of the third resistor is the same as the resistance value of the first resistor, the resistance value of the fourth resistor is equal to the resistance value of the second resistor, and the ratio of the second resistor to the first resistor is equal to the ratio of the fourth resistor to the third resistor, so that the first operational amplifier can correctly amplify the difference between the two inputs, thereby outputting an accurate differential signal, so as to further improve the detection and output reliability of the first operational amplifier.

[0013] In combination with the first aspect and the above-mentioned implementation methods, in some possible implementation methods, the buffer module includes a second operational amplifier and a third operational amplifier; the non-inverting input terminal of the second operational amplifier is used to access the reference signal, and the inverting input terminal of the second operational amplifier is connected to the output terminal of the second operational amplifier and the first terminal of the first acquisition unit; the non-inverting input terminal of the third operational amplifier is used to access the sampling signal, and the inverting input terminal of the third operational amplifier is connected to the output terminal of the third operational amplifier and the first terminal of the second acquisition unit.

[0014] In the above technical solution, the second operational amplifier and the third operational amplifier are both high-impedance voltage followers, and the core function of the voltage follower is to faithfully copy the input signal to the output end and provide current gain at the same time. That is, the second operational amplifier can accurately copy the input reference signal and output it to the differential amplifier module, and the third operational amplifier can accurately copy the input sampling signal and output it to the differential amplifier module. Secondly, the voltage follower has high input impedance and low output impedance, wherein the high input impedance means that the current drawn by the second operational amplifier and the third operational amplifier from the signal source is very small and has almost no effect on the signal source, so that the reference signal and the sampling signal connected to the differential amplifier module are not affected by external parameters, thereby ensuring the accuracy of the reference signal and the sampling signal output to the differential amplifier module.

[0015] In combination with the first aspect and the above-mentioned implementation methods, in some possible implementation methods, the over-temperature protection circuit also includes a fifth resistor and a sixth resistor; one end of the fifth resistor is connected to the power supply; one end of the sixth resistor is connected to the other end of the fifth resistor and the in-phase input terminal of the second operational amplifier, and the other end of the sixth resistor is grounded.

[0016] In the above technical solution, the fifth resistor and the sixth resistor form a voltage divider network for reducing the actual output voltage of the power supply to a level suitable for the input of the second operational amplifier. By selecting the resistance values ​​of the fifth resistor and the sixth resistor, the voltage value of the reference signal can be changed to adapt to different derating requirements of different loads, and the applicability is high.

[0017] In combination with the first aspect and the above-mentioned implementation methods, in some possible implementation methods, the over-temperature protection circuit also includes a seventh resistor, an eighth resistor and a thermistor; one end of the seventh resistor is connected to the power supply; one end of the eighth resistor is connected to the other end of the seventh resistor and the in-phase input terminal of the second operational amplifier; one end of the thermistor is connected to the other end of the eighth resistor, the other end of the thermistor is grounded, and the thermistor is arranged adjacent to the load.

[0018] In the above technical solution, the thermistor is set close to the load to collect the temperature of the load in real time, and the resistance of the thermistor will show nonlinear characteristics as the temperature of the load changes. At this time, a voltage divider network can be formed by connecting the thermistor in series with the eighth resistor and the seventh resistor to linearize the relationship between the output voltage of the thermistor and the temperature, making the temperature measurement more accurate and easier to handle. The voltage divider formed by the seventh resistor and the eighth resistor can reduce the impact of the change in the characteristics of the thermistor itself on the entire circuit, thereby enhancing the stability and reliability of the over-temperature protection circuit.

[0019] In combination with the first aspect and the above-mentioned implementation methods, in some possible implementation methods, the difference calculation module includes a third acquisition unit, a fourth acquisition unit and a fourth operational amplifier; the first end of the third acquisition unit is connected to the signal sampling module for accessing the reference signal, and the second end of the third acquisition unit is grounded; the first end of the fourth acquisition unit is connected to the differential amplification module for accessing the differential signal, and the second end of the fourth acquisition unit is grounded; the in-phase input end of the fourth operational amplifier is connected to the third end of the third acquisition unit, the inverting input end of the fourth operational amplifier is connected to the second end of the fourth acquisition unit, the output end of the fourth operational amplifier is connected to the second end of the fourth acquisition unit and the driving circuit, and the fourth operational amplifier is used to generate a difference signal based on the reference signal and the differential signal, and output it to the driving circuit.

[0020] In the above technical solution, the third acquisition unit, the fourth acquisition unit and the fourth operational amplifier constitute a subtractor, which can be used to compare the expected value (i.e., the reference signal) and the actual value (i.e., the differential signal) to obtain a difference signal and output it to the drive circuit, so that the drive circuit can adjust the response of the load based on the difference signal, thereby realizing over-temperature protection of the load.

[0021] In combination with the first aspect and the above-mentioned implementation manner, in some possible implementation manners, the third acquisition unit includes a ninth resistor and a tenth resistor, one end of the ninth resistor is connected to the signal sampling module, the other end of the ninth resistor is connected to one end of the tenth resistor and the in-phase input terminal of the fourth operational amplifier, and the other end of the tenth resistor is grounded; and the fourth acquisition unit includes an eleventh resistor and a twelfth resistor, one end of the eleventh resistor is connected to the differential amplifier module, the other end of the eleventh resistor is connected to one end of the twelfth resistor and the inverting input terminal of the fourth operational amplifier, and the other end of the twelfth resistor is connected to the output terminal of the fourth operational amplifier; wherein the resistance values ​​of the ninth resistor, the tenth resistor, the eleventh resistor and the twelfth resistor are equal.

[0022] In a second aspect, an embodiment of the present application further provides a load driving system, comprising a load, a driving circuit, and an over-temperature protection circuit as described in any optional manner of the first aspect, wherein the over-temperature protection circuit is connected to the load, and the driving circuit is connected to the load and the over-temperature protection circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a circuit structure diagram of a load driving system provided by the related technology;

[0024] Figure 2 It is a schematic diagram of curvature change of a load driving system provided by the related technology;

[0025] Figure 3 is another schematic diagram of curvature change of a load driving system provided by the related art;

[0026] Figure 4 is a structural schematic diagram of a load driving system provided in an embodiment of the present application;

[0027] Figure 5 is a schematic diagram of a module structure of a load driving system provided in an embodiment of the present application;

[0028] Figure 6 is a circuit structure diagram of a load driving system provided in an embodiment of the present application;

[0029] Figure 7 is a circuit structure diagram of another load driving system provided in an embodiment of the present application;

[0030] Figure 8 is a circuit structure diagram of another load driving system provided in an embodiment of the present application;

[0031] Fig. 9 is a circuit structure diagram of another load driving system provided in an embodiment of the present application;

[0032] Fig.10 is a circuit structure diagram of another load driving system provided in an embodiment of the present application;

[0033] Fig.11 is a circuit structure diagram of another load driving system provided in an embodiment of the present application;

[0034] Fig.12 is a schematic diagram of curvature change of a load driving system provided in an embodiment of the present application;

[0035] Fig.13 This is a circuit structure diagram of another load driving system provided in an embodiment of the present application.

[0036] Among them, the reference numerals in the figure are:

[0037] 1', load driving system; 11', power supply module; 12', driving circuit; 13', load; 1, load driving system; 11, load; 12, driving circuit; 13, over-temperature protection circuit; 131, signal sampling module; 132, differential amplification module; 1321, first acquisition unit; 1322, second acquisition unit; 133, difference calculation module; 1331, third acquisition unit; 1332, fourth acquisition unit; 14, power supply;

[0038] R01, the first voltage-dividing resistor; R02, the second voltage-dividing resistor; R1, the first resistor; R2, the second resistor; R3, the third resistor; R4, the fourth resistor; R5, the fifth resistor; R6, the sixth resistor; R7, the seventh resistor; R8, the eighth resistor; R9, the ninth resistor; R10, the tenth resistor; R11, the eleventh resistor; R12, the twelfth resistor; RNTC, the thermistor; C, the capacitor; NTC, the thermistor; LED, the light-emitting diode; X1, the first operational amplifier; X2, the second operational amplifier; X3, the third operational amplifier; X4, the fourth operational amplifier; VNTC, the sampling signal; VREF, the reference signal; VF, the differential signal; VG, the difference signal. Detailed implementation

[0039] The technical solutions in the present application will be clearly and elaborately described below in conjunction with the accompanying drawings. Among them, in the description of the embodiments of the present application, unless otherwise specified, " / " means "or". For example, A / B may mean A or B: "and / or" in the text is only a description of the association relationship between associated objects, indicating that there can be three relationships. For example, A and / or B may mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of the present application, "a plurality" means two or more than two.

[0040] Hereinafter, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as implying or suggesting relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0041] High-power LEDs are widely used in various fields (such as lighting fixtures, display screens, etc.) due to their high brightness, high efficiency, and long lifespan. During operation, LEDs generate a large amount of heat. To prevent overheating and damage, LEDs are usually used in conjunction with heat sinks to reduce their operating temperature to a controllable and safe range. When factors such as the shape, structure, and manufacturing cost of the device limit the heat dissipation capacity, in order to ensure the heat dissipation effect, the LED is usually derated when it is in a high-temperature state. It should be noted that derating means reducing the operating current of the LED. When the operating current of the LED is reduced, the electrical energy input to the LED decreases, and the heat generated by the LED also decreases correspondingly, so that the operating temperature of the LED can be within a controllable and safe range.

[0042] In order to derate the LED at high temperature, a negative temperature coefficient thermistor (NTC) is usually provided in the related technology. NTC can collect the working temperature of the LED in real time and convert it into a corresponding voltage signal output. That is, when the working temperature of the LED changes, the voltage signal output by the NTC will also change accordingly. The LED current is adjusted by the voltage signal to achieve the derated treatment of the LED.

[0043] For example, Figure 1 As shown, the load driving system 1' in the related art includes a power supply module 11', a driving circuit 12', a load 13', a first voltage-dividing resistor R01, a second voltage-dividing resistor R02, a thermistor RNTC and a capacitor C. One end of the first voltage-dividing resistor R01 is connected to the power supply module 11', the other end of the first voltage-dividing resistor R01 is connected to one end of the second voltage-dividing resistor R02, the first plate of the capacitor C and the driving circuit 12', the other end of the second voltage-dividing resistor R02 is connected to one end of the thermistor RNTC and the second plate of the capacitor C, the thermistor RNTC is arranged adjacent to the load 13', and the driving circuit 12' is connected to the load 13'.

[0044] The first voltage-dividing resistor R01, the second voltage-dividing resistor R02, the thermistor RNTC and the power supply module 11' form a voltage-dividing circuit, wherein the load 13' is a plurality of LEDs connected in series, and the thermistor RNTC is arranged near the load 13' to collect the working temperature of the LED in real time and convert it into a corresponding voltage signal output. The thermistor RNTC can be selected from TDK's ntcg164kf104ft1s model. Under normal conditions, the working current of the LED is 1.1A (ampere), and the power supply module 11' is a low dropout linear regulator (LowDropout Regulator, LDO) power supply module, and its supply voltage is usually 3V (volt). Assume that the high temperature derating requirement of the LED is: no derating for thermistor RNTC<95℃ (degrees Celsius), derating is required when 95℃≤thermistor RNTC≤125℃, and the output current of the LED needs to be reduced from 100% to 50%. The driving circuit 12' usually includes a driving chip (Integrated Circuit, IC) and a DC / DC converter. The driving IC in the related art can be ROHM18353. The other end of the first voltage divider resistor R01 is connected to the dimming sampling PIN pin of the driving IC. The dimming sampling PIN pin is the 9PIN_DSET pin of the driving IC. It is worth noting that the DSET pin is the duty cycle signal input interface of the pulse width modulation (PWM) dimming inside the driving IC. The calculation formula of the PWM duty cycle is as follows (1):

[0045]

[0046] Among them, D PWM is the PWM duty cycle, V REF3 is the reference voltage, R DSET1 and R DSET2 is the resistance value, V RAMPB is the starting voltage of the ramp signal, V RAMPP is the end voltage of the ramp signal, where V RAMPB is 0.40V, V RAMPP is 2.40V.

[0047] The calculation formula of VDSET is as follows (2):

[0048] V DEST =V R02 +V RNTC =3V*((R02+RNTC) / (R01+R02+RNTC)) (2)

[0049] Among them, V DEST For the DSET pin, V R01 is the resistance of the first voltage divider resistor, V R02 is the resistance value of the second voltage divider resistor, V RNTC is the resistance value of the thermistor.

[0050] In order to meet the high temperature derating requirements of the above-mentioned LED, it can be deduced from formulas (1) and (2) that when thermistor RNTC is less than 95°C, VDSET ≥ 2.4V, and when thermistor RNTC is in the range of 95°C-125°C, VDSET changes from 2.4V to 1.4V, thereby achieving the purpose of "derating is required when 95°C≤thermistor RNTC≤125°C, and the output current of the LED needs to be reduced from 100% to 50%". In this way, the load driving system 1' in the related art can perform derating processing on the LED in a high temperature state through the thermistor RNTC.

[0051] The change of VDSET depends entirely on the thermistor RNTC. If the temperature derating requirement is to be achieved, when the thermistor RNTC changes between 95°C and 125°C, the rate of change curve needs to meet the change requirements of the target curve of VDSET. The relevant technology can change the display temperature and output current change characteristics of the thermistor RNTC by setting the resistance values ​​of the first voltage-dividing resistor R01 and the second voltage-dividing resistor R02. For example, when the resistance value of the first voltage-dividing resistor R01 is 1.5K and the resistance value of the second voltage-dividing resistor R02 is 0.3K, the curve of the display temperature and output current of the thermistor RNTC is as follows: Figure 2 The solid line shown, Figure 2The dotted line in is the target curve. When the resistance of the first voltage-dividing resistor R01 is 2.7K and the resistance of the second voltage-dividing resistor R02 is 0.18K, the curve of the temperature displayed by the thermistor RNTC and the output current is as follows: Figure 3 The solid line shown, Figure 3 The dotted line in is the target curve. Figure 2 and Figure 3 It can be seen that based on the value and type selection of the first voltage-dividing resistor R01 and the second voltage-dividing resistor R02, the load driving system 1' in the related art can only meet the design requirements of one temperature point at most. In this way, the change rate curve of the thermistor RNTC in the related art does not meet the change requirements of the target curve of VDSET. Secondly, the temperature and resistance change characteristics of the thermistor RNTC are nonlinear, and the change rate is also determined by the material formula of the thermistor RNTC itself. The thermistor RNTC is a universal standard part, and its corresponding resistance is pre-defined by the manufacturer, that is, its corresponding resistance-temperature curve is also pre-defined, and it cannot be set based on the needs of different loads. The adaptability is poor, resulting in low over-temperature protection accuracy.

[0052] To this end, the related art is usually equipped with an MCU, which is used in conjunction with a thermistor RNTC to detect the temperature of the LED in real time and derating the LED when the LED temperature is too high. However, the MCU usually integrates multiple functions. If it only implements the derating function, there is a certain waste of resources, and the MCU is more expensive and larger in size.

[0053] To this end, an embodiment of the present application provides an over-temperature protection circuit and a load driving system. The over-temperature protection circuit can change the operating current of the load based on the changing difference signal to achieve the purpose of over-temperature protection of the load and ensure the operating reliability of the load. The over-temperature protection circuit has low power consumption and manufacturing cost, small size, and high adaptability.

[0054] The over-temperature protection circuit and load driving system provided in the embodiments of the present application are exemplarily described below in conjunction with the drawings.

[0055] like Figure 4 As shown, the embodiment of the present application provides a load driving system 1, which includes a load 11 and a driving circuit 12, wherein the driving circuit 12 is connected to the load 11 and is used to drive the load 11 to work. The load 11 may be a plurality of light-emitting diodes LED connected in series, and the driving circuit 12 is respectively connected to the positive electrodes of the light-emitting diodes LED located at the head and the tail and the negative electrode of the light-emitting diode LED located at the end, so as to realize the driving of the plurality of light-emitting diodes LED connected in series.

[0056] Optionally, the driving circuit 12 may be a DC / DC converter. Correspondingly, the driving circuit 12 includes a driving chip 121 and a switch Q. The driving chip 121 drives the load 11 by controlling the on / off of the switch Q. The circuit architecture and functions of the DC / DC converter are common knowledge in the art and will not be described in detail.

[0057] The load 11 will emit a lot of heat during use. In order to prevent the load 11 from being damaged by overheating, in one example, Figure 5 As shown, the load driving system 1 provided in the present application further includes an over-temperature protection circuit 13, and the over-temperature protection circuit 13 is connected to the load 11. Exemplarily, the over-temperature protection circuit 13 may include a signal sampling module 131, a differential amplification module 132, and a difference calculation module 133, the differential amplification module 132 is connected to the signal sampling module 131, and the difference calculation module 133 is connected to the signal sampling module 131, the differential amplification module 132, and the driving circuit 12.

[0058] In this example, the signal sampling module 131 is used to access the reference signal VREF and the sampling signal VNTC, and the sampling signal VNTC is a signal corresponding to the temperature of the load 11. The differential amplifier module 132 accesses the reference signal VREF and the sampling signal VNTC output by the signal sampling module 131, and generates a differential signal VF based on the reference signal VREF and the sampling signal VNTC. The difference calculation module 133 accesses the reference signal VREF and the differential signal VF, and calculates the difference signal VG based on the reference signal VREF and the differential signal VF and outputs it to the driving circuit 12, so that the driving circuit 12 drives the load 11 based on the difference signal VG. It is worth noting that the difference calculation module 133 will output the difference signal VG to the dimming sampling PIN pin of the DC / DC converter in the driving circuit 12, so that the driving circuit 12 can adjust the working current of the load 11 based on the difference signal VG connected to the dimming sampling PIN pin to achieve the purpose of dimming.

[0059] Among them, the reference signal VREF is a preset reference voltage. For example, assuming that the derating requirement of the load 11 is: no derating when the temperature of the load 11 is less than 95°C, and derating is required when the temperature of the load 11 is in the range of 95°C-125°C, then the reference voltage is preset to the voltage corresponding to the temperature of the load 11 being 95°C. It is worth noting that the reference voltage is a fixed value preset based on the derating requirement. The sampling signal VNTC is a sampling voltage corresponding to the temperature of the collected load 11. For example, when the temperature of the load 11 is 95°C, the sampling voltage is V1, and when the temperature of the load 11 is 100°C, the sampling voltage is V2, that is, the sampling signal VNTC is a changing value that changes in real time with the temperature of the load 11. The differential amplifier module 132 can generate different differential signals VF based on a fixed reference voltage and a changing sampling voltage.

[0060] Exemplarily, when the temperature of the load 11 is normal (for example, the temperature of the load 11 is 95° C. at this time), the voltage value of the sampling signal VNTC is equal to the voltage value of the reference signal VREF, and the signal sampling module 131 will stably output the sampling signal VNTC and the reference signal VREF to the differential amplifier module 132. At this time, the differential signal VF generated by the differential amplifier module 132 is approximately equal to zero, for example, 0.01 V. Correspondingly, the difference signal VG calculated by the difference calculation module 133 based on the reference signal VREF and the differential signal VF is approximately equal to the reference signal VREF, that is, at this time, the driving circuit 12 drives the load 11 based on the reference signal VREF, and at this time, the working current of the load 11 is not reduced, and the working current of the load 11 is maintained at 100%. When the load 11 is in a high temperature state (for example, the temperature of the load 11 is 125°C at this time), the voltage value of the sampling signal VNTC is not equal to the voltage value of the reference signal VREF, and the signal sampling module 131 will stably output the sampling signal VNTC and the reference signal VREF to the differential amplifier module 132. At this time, the differential signal VF generated by the differential amplifier module 132 is greater than zero, for example, 1.152V. Correspondingly, the difference signal VG calculated by the difference calculation module 133 based on the reference signal VREF and the differential signal VF is not equal to the reference signal VREF, and the driving circuit 12 drives the load 11 based on the difference signal VG, that is, the working current of the load 11 has been reduced at this time, and the working current of the load 11 is 50%.

[0061] In this way, the differential amplifier module 132 in the present application can obtain the corresponding differential signal VF based on the fixed reference signal VREF and the changing sampling signal VNTC, and the difference calculation module 133 can calculate the corresponding difference signal VG based on the fixed reference signal VREF and the changing differential signal VF, that is, the difference signal VG is also a changing value. The driving circuit 12 can change the working current of the load 11 based on the changing difference signal VG to achieve the purpose of over-temperature protection of the load 11 and ensure the operating reliability of the load 11. Among them, the differential amplifier module 132 and the difference calculation module 133 can calculate the corresponding difference signal VG based on the changing sampling signal VNTC, that is, the size of the difference signal VG can be changed correspondingly through the hardware circuit, thereby correspondingly changing the working current of the load 11, that is, the present application enables the working current of the load 11 to change with the temperature, and there is no need to set up additional controllers such as MCU to perform software monitoring and control on the load 11, avoiding the problem of resource waste. Secondly, compared with the MCU in the related art, the over-temperature protection circuit 13 provided in the present application has lower power consumption and manufacturing cost, smaller size, and higher adaptability.

[0062] In order to enable the differential amplifier module 132 to obtain a corresponding differential signal VF based on the fixed reference signal VREF and the changing sampling signal VNTC, in one example, Figure 6 As shown, the differential amplifier module 132 includes a first acquisition unit 1321, a second acquisition unit 1322 and a first operational amplifier X1. The first end of the first acquisition unit 1321 is connected to the signal sampling module 131 to access the reference signal VREF, the second end of the first acquisition unit 1321 is grounded, and the first end of the second acquisition unit 1322 is connected to the signal sampling module 131 for accessing the sampling signal VNTC. The in-phase input end (as shown in FIG. 6, "+") of the first operational amplifier X1 is connected to the third end of the first acquisition unit 1321, the inverting input end (as shown in FIG. 6, "-") of the first operational amplifier X1 is connected to the second end of the second acquisition unit 1322, and the output end of the first operational amplifier X1 is connected to the third end of the second acquisition unit 1322 and the difference calculation module 133. The first operational amplifier X1 can generate a differential signal VF based on the reference signal VREF and the sampling signal VNTC, and output it to the difference calculation module 133.

[0063] In this example, the first acquisition unit 1321 processes the input reference signal VREF by voltage division and outputs it to the non-inverting input terminal of the first operational amplifier X1, and the second acquisition unit 1322 processes the input sampling signal VNTC by voltage division and outputs it to the inverting input terminal of the first operational amplifier X1. The first operational amplifier X1 can effectively amplify the difference between the reference signal VREF and the sampling signal VNTC, and output the corresponding differential signal VF. That is, at this time, the first acquisition unit 1321, the second acquisition unit 1322 and the first operational amplifier X1 constitute a differential amplifier, and the differential amplifier can detect slight changes in the signal, that is, the first operational amplifier X1 can detect slight changes in the sampling signal VNTC in time, and output the corresponding differential signal VF based on the changed sampling signal VNTC and the fixed reference signal VREF, and the detection and output reliability and accuracy are high. Secondly, the first operational amplifier X1 can well suppress the signal (i.e., the common mode signal) that exists in both input terminals to improve the signal-to-noise ratio and reduce interference noise.

[0064] In one example, if Figure 7 As shown, the first acquisition unit 1321 may include a first resistor R1 and a second resistor R2, one end of the first resistor R1 is connected to the signal sampling module 131, one end of the second resistor R2 is connected to the other end of the first resistor R1 and the in-phase input end of the first operational amplifier X1, and the other end of the second resistor R2 is grounded.

[0065] In this example, the first resistor R1 will divide the input reference signal VREF and output it to the non-inverting input terminal of the first operational amplifier X1, and the first resistor R1 will form a voltage divider network with the second resistor R2 to adjust the actual voltage level input to the non-inverting input terminal of the first operational amplifier X1, thereby changing the gain setting. In this way, based on the needs of different loads 11, the ratio of the second resistor R2 to the first resistor R1 can be flexibly set to change the gain to adapt to the change requirements of the VDSET target curve of different loads 11, thereby ensuring the protection accuracy of the over-temperature protection circuit 1, and having high applicability.

[0066] It is worth noting that the rate of change curve output by the over-temperature protection circuit 13 needs to meet the change requirements of the target curve of VDSET, that is, the two temperature points of the over-temperature protection circuit 13 and the rate of change of the curve need to meet the target curve. Among them, the reference signal VREF is a fixed value preset based on the derating requirement. When the temperature of the load 11 does not reach the derating temperature, the difference signal VG output by the over-temperature protection circuit 13 can meet the design requirements of the initial temperature point (for example, 95°C). Then, by setting the multiplier of the first operational amplifier X1 (that is, the ratio of the second resistor R2 to the first resistor R1), the voltage gain of the sampling signal VNTC that changes with temperature can be changed accordingly, so that the parameters of another temperature point (for example, 125°C) fall within the required value range, so that both temperature points can meet the design requirements.

[0067] In one example, if Figure 7 As shown, the second acquisition unit 1322 may include a third resistor R3 and a fourth resistor R4, one end of the third resistor R3 is connected to the signal sampling module 131, one end of the fourth resistor R4 is connected to the other end of the third resistor R3 and the inverting input end of the first operational amplifier X1, and the other end of the fourth resistor R4 is connected to the output end of the first operational amplifier X1. The resistance value of the third resistor R3 is the same as the resistance value of the first resistor R1, and the resistance value of the fourth resistor R4 is equal to the resistance value of the second resistor R2.

[0068] In this example, the third resistor R3 divides the input sampling signal VNTC and outputs it to the inverting input terminal of the first operational amplifier X1. The fourth resistor R4 is part of the feedback path. The fourth resistor R4 controls the amount of signal from the output terminal of the first operational amplifier X1 back to the inverting input terminal of the first operational amplifier X1 to directly affect the closed-loop gain of the circuit. The third resistor R3 and the fourth resistor R4 together determine the current in the feedback loop, thereby affecting the overall gain of the circuit. In order to obtain an accurate proportional relationship, the resistance of the third resistor R3 is the same as the resistance of the first resistor R1, the resistance of the fourth resistor R4 is equal to the resistance of the second resistor R2, and the ratio of the second resistor R2 to the first resistor R1 is equal to the ratio of the fourth resistor R4 to the third resistor R3, so that the first operational amplifier X1 can correctly amplify the difference between the two inputs, thereby outputting an accurate differential signal VF, so as to further improve the detection and output reliability of the first operational amplifier X1.

[0069] When the differential amplifier module 132 includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4 and a first operational amplifier X1, the calculation formula of the differential signal VF is as follows:

[0070] VF=(R2 / R1)*(VREF-VNTC) (3)

[0071] Wherein, VF is the voltage of the differential signal, R2 is the resistance value of the second resistor, R1 is the resistance value of the first resistor, VREF is the voltage of the reference signal, and VNTC is the voltage of the sampling signal. Wherein, the voltage value of VF needs to be in the range of 0-3V to meet the requirements of the rail-to-rail type op amp, that is, the minimum output is close to 0V and the maximum is close to the supply voltage 3V. Formula (3) shows that by setting the ratio of the second resistor R2 to the first resistor R1, the voltage difference between the reference signal VREF and the sampling signal VNTC can be correspondingly amplified or reduced to change the voltage gain, thereby achieving the design goal that both temperature points can meet the design requirements.

[0072] In order to prevent the reference signal VREF and the sampling signal VNTC connected to the differential amplifier module 132 from being affected by external parameters, in one example, Figure 8 As shown, the signal sampling module 131 includes a second operational amplifier X2 and a third operational amplifier X3, the non-inverting input terminal of the second operational amplifier X2 is used to access the reference signal VREF, and the inverting input terminal of the second operational amplifier X2 is connected to the output terminal of the second operational amplifier X2 and the first terminal of the first acquisition unit 1321. The non-inverting input terminal of the third operational amplifier X3 is used to access the sampling signal VNTC, and the inverting input terminal of the third operational amplifier X3 is connected to the output terminal of the third operational amplifier X3 and the first terminal of the second acquisition unit 1322.

[0073] In this example, the second operational amplifier X2 and the third operational amplifier X3 are both high-impedance voltage followers. The core function of a voltage follower is to faithfully copy the input signal to the output while providing current gain. That is, the second operational amplifier X2 can accurately copy and output the input reference signal VREF to the differential amplification module 132, and the third operational amplifier X3 can accurately copy and output the input sampled signal VNTC to the differential amplification module 132 to ensure the accuracy of the reference signal VREF and the sampled signal VNTC output to the differential amplification module 132. Secondly, the voltage follower has a high input impedance and a low output impedance. Among them, the high input impedance means that the second operational amplifier X2 and the third operational amplifier X3 draw very little current from the signal source and hardly affect the signal source, so that the reference signal VREF and the sampled signal VNTC connected to the differential amplification module 132 are not affected by external parameters. The low output impedance enables the second operational amplifier X2 and the third operational amplifier X3 to better drive the subsequent load (i.e., the differential amplification module 132).

[0074] In one example, as Fig. 9 shown, the overtemperature protection circuit 13 further includes a fifth resistor R5 and a sixth resistor R6. One end of the fifth resistor R5 is connected to the power supply 14, one end of the sixth resistor R6 is connected to the other end of the fifth resistor R5 and the non-inverting input terminal of the second operational amplifier X1, and the other end of the sixth resistor R6 is grounded.

[0075] In this example, the fifth resistor R5 and the sixth resistor R6 form a voltage division network for reducing the actual output voltage of the power supply to a level suitable for the input of the second operational amplifier X2. Secondly, by selecting the resistance values of the fifth resistor R5 and the sixth resistor R6, the voltage value of the reference signal VREF can be changed, so as to adapt to the different derating requirements of different loads 11, and the applicability is relatively high.

[0076] Among them, when the load 11 is an LED, the power supply 14 can be an LDO. When the load 11 is other loads, the power supply 14 can also be adjusted accordingly. This application does not make specific restrictions on this.

[0077] In one example, as Fig. 9 shown, the overtemperature protection circuit 13 further includes a seventh resistor R7, an eighth resistor R8, and a thermistor RNTC. One end of the seventh resistor R7 is connected to the power supply, one end of the eighth resistor R8 is connected to the other end of the seventh resistor R7 and the non-inverting input terminal of the second operational amplifier X2, one end of the thermistor RNTC is connected to the other end of the eighth resistor R8, the other end of the thermistor RNTC is grounded, and the thermistor RNTC is arranged adjacent to the load 11. At this time, the seventh resistor R7, the eighth resistor R8, and the thermistor RNTC form a sampling circuit.

[0078] In this example, the thermistor RNTC is set close to the load 11 to collect the temperature of the load 11 in real time, and the resistance of the thermistor RNTC will show nonlinear characteristics as the temperature of the load 11 changes. At this time, a voltage divider network can be formed by connecting the thermistor RNTC in series with the eighth resistor R8 and the seventh resistor R7 to linearize the relationship between the output voltage and temperature of the thermistor RNTC, making the temperature measurement more accurate and easy to handle. And the voltage divider formed by the seventh resistor R7 and the eighth resistor R8 can reduce the impact of the change in the characteristics of the thermistor RNTC itself on the entire circuit, thereby enhancing the stability and reliability of the over-temperature protection circuit 13. And the present application can make the working current of the load 11 change with the temperature, and this function is not limited to the selection restrictions of the thermistor RNTC, and has high applicability.

[0079] Among them, the seventh resistor R7 is used as a pull-up resistor, and the eighth resistor R8 is used as a pull-down resistor. By selecting appropriate resistance values ​​of the pull-up resistor and the pull-down resistor, the voltage of the sampling signal VNTC within the expected temperature range (for example, 95°C-125°C) can fall within the optimal input range of the second operational amplifier X2, thereby improving the measurement accuracy.

[0080] In one example, if Fig.10 As shown, the difference calculation module 133 may include a third acquisition unit 1331, a fourth acquisition unit 1332 and a fourth operational amplifier X4. The first end of the third acquisition unit 1331 is connected to the signal sampling module 131 for receiving the reference signal VREF, and the second end of the third acquisition unit 1331 is grounded. The first end of the fourth acquisition unit 1332 is connected to the differential amplifier module 132 for receiving the differential signal VF. The in-phase input end of the fourth operational amplifier X4 is connected to the third end of the third acquisition unit 1331, the inverting input end of the fourth operational amplifier X4 is connected to the second end of the fourth acquisition unit 1332, the output end of the fourth operational amplifier X4 is connected to the third end of the fourth acquisition unit 1332 and the driving circuit 12, and the fourth operational amplifier X4 can generate a difference signal VG based on the reference signal VREF and the differential signal VF, and output it to the driving circuit 12.

[0081] In this example, the third acquisition unit 1331 outputs the connected reference signal VREF to the non-inverting input terminal of the fourth operational amplifier X4 after voltage division processing, and the fourth acquisition unit 1332 outputs the connected differential signal VF to the inverting input terminal of the fourth operational amplifier X4 after voltage division processing, and the fourth operational amplifier X4 can obtain the changing differential signal VG based on the fixed reference signal VREF and the changing differential signal VF. It is worth noting that at this time, the third acquisition unit 1331, the fourth acquisition unit 1332 and the fourth operational amplifier X4 constitute a subtractor, which can be used to compare the expected value (i.e., the reference signal VREF) and the actual value (i.e., the differential signal VF), i.e., VG=VREF-VF, thereby obtaining the differential signal VG and outputting it to the drive circuit 12, so that the drive circuit 12 can adjust the response of the load 11 based on the differential signal VG, thereby realizing over-temperature protection for the load 11.

[0082] Exemplarily, when the temperature of the load 11 is normal (for example, the temperature of the load 11 is 95°C at this time), that is, when the thermistor RNTC is in the non-derating interval, the differential signal VF generated by the differential amplifier module 132 is approximately equal to zero, for example, 0.01V. Correspondingly, the difference signal VG calculated by the fourth operational amplifier X4 based on the reference signal VREF and the differential signal VF is approximately equal to the reference signal VREF, that is, at this time, the driving circuit 12 drives the load 11 based on the reference signal VREF, and at this time, the working current of the load 11 is not reduced, and the working current of the load 11 remains at 100%. When the load 11 is in a high temperature state (for example, the temperature of the load 11 is 125°C at this time), that is, when the thermistor RNTC is in the derating interval, the differential signal VF generated by the differential amplifier module 132 is greater than zero, for example, 1.152V. Correspondingly, the difference signal VG calculated by the fourth operational amplifier X4 based on the reference signal VREF and the differential signal VF is not equal to the reference signal VREF, and the driving circuit 12 drives the load 11 based on the difference signal VG, that is, the operating current of the load 11 has been reduced at this time, and the operating current of the load 11 is 50%.

[0083] The voltage value of the difference signal VG also needs to be in the range of 0-3V to meet the requirements of the rail-to-rail op amp, that is, the minimum output is close to 0V and the maximum is close to the supply voltage 3V.

[0084] In one example, if Fig.11As shown in the figure, the third acquisition unit 1331 includes a ninth resistor R9 and a tenth resistor R10. One end of the ninth resistor R9 is connected to the signal sampling module 131, and the other end of the ninth resistor R9 is connected to one end of the tenth resistor R10 and the non-inverting input terminal of the fourth operational amplifier X4. The other end of the tenth resistor R10 is grounded. The fourth acquisition unit 1332 includes an eleventh resistor R11 and a twelfth resistor R12. One end of the eleventh resistor R11 is connected to the differential amplification module 132, and the other end of the eleventh resistor R11 is connected to one end of the twelfth resistor R12 and the inverting input terminal of the fourth operational amplifier X4. The other end of the twelfth resistor R12 is connected to the output terminal of the fourth operational amplifier X4. Among them, the resistance values of the ninth resistor R9, the tenth resistor R10, the eleventh resistor R11, and the twelfth resistor R12 are equal.

[0085] In this example, the ninth resistor R9 and the tenth resistor R10 serve as a voltage divider network, and the eleventh resistor R11 and the twelfth resistor R12 serve as a voltage divider network. The functions they achieve can refer to the functions of the voltage divider and the effects of the above voltage divider, and will not be elaborated here.

[0086] It should be noted that the above first operational amplifier X1, second operational amplifier X2, third operational amplifier X3, and fourth operational amplifier X4 can be integrated in an IC chip at the same time. Assuming that the high-temperature derating requirement of the LED is that the thermistor RNTC does not derate when RNTC < 95°C, and derating is required when 95°C ≤ RNTC ≤ 125°C, the following uses a set of data to give an exemplary description of the over-temperature protection circuit 13 provided by the present application.

[0087] Exemplarily, when the load 11 in the present application is an LED, the power supply 14 uses an LDO, and the output voltage of the voltage reference LDO is supplied, that is, the output voltage of the power supply 14 can be 3V. At the same time, the above first operational amplifier X1, second operational amplifier X2, third operational amplifier X3, and fourth operational amplifier X4 are integrated in an IC chip, and this IC chip is a low-voltage operational amplifier chip (such as TLV9044), with a voltage range of 1.2 - 5.5V and rail-to-rail input and output.

[0088] Step 1: Calculate the reference signal VREF: The resistance of the fifth resistor R5 and the sixth resistor R6 is 1.5kΩ (kilo-ohm) ±1%, and the resistance of the ninth resistor R9, the tenth resistor R10, the eleventh resistor R11 and the twelfth resistor R12 is 10kΩ ±1%. Considering the output accuracy of the LDO and the resistance accuracy of each resistor, the typical voltage value of the reference signal VREF is calculated to be 2.553V, and the minimum voltage value of the reference signal VREF is 2.471V. It is worth noting that the minimum voltage value of the reference signal VREF must be greater than the sum of the maximum voltage 2.42V at VDEST_100% duty cycle + the minimum output voltage of the op amp. When designing the voltage parameters of the reference signal VREF, it is necessary to ensure that when the thermistor RNTC is in the non-derating range, LDO deviation, resistor deviation, sampling pin control deviation, op amp minimum output voltage, temperature offset and other extreme conditions, there will be no derating phenomenon.

[0089] Step 2, setting of pull-up resistor and pull-down resistor in sampling loop: Set a preset derating starting point. It is worth noting that the preset derating starting point is usually 3-10°C ahead of the target derating starting point, so as to flexibly adjust it when the later verification is not appropriate. When the target derating starting point is 95°C, the preset derating starting point can be set to 89°C, and the corresponding resistance of thermistor RNTC when the temperature of load 11 is 89°C is 6979Ω. Secondly, it is required that at the preset derating starting point, the voltage of sampling signal VNTC = reference signal VREF = 2.553V. And the parameters of the seventh resistor R7 (i.e., pull-up resistor) and the eighth resistor R18 (i.e., pull-up resistor) are calculated. For example, the resistance of the seventh resistor R7 is 1.2KΩ±1%, and the resistance of the eighth resistor R18 is 0Ω.

[0090] Step 3, setting the multiple of the first operational amplifier X1: The resistance of thermistor RNTC is 2176Ω when the temperature of load 11 is 125℃, and the corresponding voltage value of sampling signal VNTC at 125℃=3V*(2.176 / (1.2+2.176))=1.934V, at this time, the voltage of differential signal VF=the voltage of reference signal VREF-the de-rating requirement value at 125℃=2.553V-1.4V=1.153V. Correspondingly, the β (multiple) of the first operational amplifier X1=differential signal VF / (reference voltage VREF-VNTC))=1.153 / (2.553-1.934)=1.861. At the same time, according to β, the resistance of the first resistor R1 and the third resistor R3 is set to 10kΩ±1%, and the resistance of the second resistor R2 and the fourth resistor R4 is set to 18.6KΩ±1%.

[0091] Step 4: Based on the above data, the calculations at different temperature points are performed to obtain the following Table 1:

[0092]

[0093] Table 1

[0094] Based on Table 1, Fig.12 According to the above calculations, the over-temperature protection circuit 13 provided in the present application meets the design requirements, that is, the thermistor RNTC is less than 95°C without derating, the operating current of the LED is 100% (i.e. 1.1A), and derating is required when the thermistor RNTC is 95°C≤125°C, and the operating current of the LED is reduced to 50% (i.e. about 0.5A) of the high temperature derating requirement, and both temperature points can meet the design requirements.

[0095] In another example, the over-temperature protection circuit 13 provided in the present application can be partially integrated inside the DCDC conversion chip of the driving circuit 12 (ie, inside the driving chip 121), such as Fig.12 As shown, the first operational amplifier X1, the second operational amplifier X2, the third operational amplifier X3 and the fourth operational amplifier X4 are integrated inside the DCDC conversion chip, and the non-inverting input terminal of the third operational amplifier X3 is connected to the NTC_PIN pin of the DCDC conversion chip. The power supply 14 is connected to the LDO_PIN2 pin and the VIN_PIN1 pin of the DCDC conversion chip to realize the power supply of the DCDC conversion chip. The seventh resistor R7 and the eighth resistor R8 are arranged outside the DCDC conversion chip, and one end of the seventh resistor R7 is connected to the LDO_PIN2 pin of the DCDC conversion chip, and the other end of the seventh resistor R7 is connected to one end of the eighth resistor R8 and the NTC_PIN pin of the DCDC conversion chip. The other end of the eighth resistor R8 is connected to the thermistor RNTC. The power supply 14, the first resistor R1, the third resistor R3, the fifth resistor R5, the sixth resistor R6, the ninth resistor R9, the tenth resistor R10, the eleventh resistor R11 and the twelfth resistor R12 are integrated in the driving circuit 12. The power supply 14 is connected to the LDO_PIN pin and the VIN_PIN pin of the DCDC conversion chip to realize power supply to the DCDC conversion chip. The second resistor R2 and the fourth resistor R4 are arranged outside the driving circuit 2 and are respectively connected to the PIN pins of the DCDC conversion chip. In this example, the seventh resistor R7, the eighth resistor R8 and the thermistor RNTC are set according to the derating strategy and the internal reference voltage. The over-temperature protection circuit 13 can also be fully integrated outside the driving circuit 12, and this application does not make specific restrictions on this.

[0096] In summary, the differential amplifier module 132 in the present application can obtain the corresponding differential signal VF based on the fixed reference signal VREF and the changing sampling signal VNTC, and the difference calculation module 133 can calculate the corresponding difference signal VG based on the fixed reference signal VREF and the changing differential signal VF, that is, the difference signal VG is also a changing value. The driving circuit 12 can change the working current of the load 11 based on the changing difference signal VG to achieve the purpose of over-temperature protection of the load 11 and ensure the operating reliability of the load 11. Among them, the differential amplifier module 132 and the difference calculation module 133 can calculate the corresponding difference signal VG based on the changing sampling signal VNTC, that is, the size of the difference signal VG can be changed correspondingly through the hardware circuit, thereby correspondingly changing the working current of the load 11, and there is no need to set up additional controllers such as MCU to perform software monitoring and control on the load 11, avoiding the problem of resource waste. Secondly, compared with the MCU in the related art, the over-temperature protection circuit 13 provided in the present application has lower power consumption and manufacturing cost, smaller size, and higher adaptability.

[0097] Through the description of the above implementation methods, technical personnel in the relevant field can understand that for the convenience and simplicity of description, only the division of the above-mentioned functional modules is used as an example. In actual applications, the above-mentioned functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above.

[0098] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of modules or units is only a logical function division, and there may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0099] The above contents are only specific implementation methods of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. An over-temperature protection circuit is applied to a load driving system, wherein the load driving system comprises a load and a driving circuit, and is characterized in that: The over-temperature protection system comprises: A signal sampling module, the signal sampling module is used to access a reference signal and a sampling signal, wherein the sampling signal is a signal corresponding to the temperature of the load; a differential amplification module, the differential amplification module being connected to the signal sampling module, the differential amplification module being used to access the reference signal and the sampling signal output by the signal sampling module, and to generate a differential signal based on the reference signal and the sampling signal; and, A difference calculation module, the difference calculation module is connected to the signal sampling module, the differential amplification module and the driving circuit, the difference calculation module is used to access the reference signal and the differential signal, and calculate the difference signal based on the reference signal and the differential signal to output to the driving circuit, so that the driving circuit drives the load based on the difference signal.

2. The over-temperature protection circuit according to claim 1, characterized in that: The differential amplifier module comprises: A first acquisition unit, wherein a first end of the first acquisition unit is connected to the signal sampling module and is used to access the reference signal, and a second end of the first acquisition unit is grounded; A second acquisition unit, a first end of which is connected to the signal sampling module and is used to access the sampling signal; and A first operational amplifier, wherein the non-inverting input terminal of the first operational amplifier is connected to the third terminal of the first acquisition unit, the inverting input terminal of the first operational amplifier is connected to the second terminal of the second acquisition unit, the output terminal of the first operational amplifier is connected to the third terminal of the second acquisition unit and the difference calculation module, and the first operational amplifier is used to generate the differential signal based on the reference signal and the sampling signal, and output it to the difference calculation module.

3. The over-temperature protection circuit according to claim 2, characterized in that: The first acquisition unit includes: A first resistor, one end of which is connected to the signal sampling module; and A second resistor, one end of the second resistor is connected to the other end of the first resistor and the non-inverting input end of the first operational amplifier, and the other end of the second resistor is grounded.

4. The over-temperature protection circuit according to claim 3, characterized in that: The second acquisition unit includes: A third resistor, one end of which is connected to the signal sampling module; and a fourth resistor, one end of the fourth resistor being connected to the other end of the third resistor and the inverting input end of the first operational amplifier, and the other end of the fourth resistor being connected to the output end of the first operational amplifier; The resistance value of the third resistor is the same as the resistance value of the first resistor, and the resistance value of the fourth resistor is equal to the resistance value of the second resistor.

5. The over-temperature protection circuit according to claim 2, characterized in that: The signal sampling module comprises: a second operational amplifier, wherein a non-inverting input terminal of the second operational amplifier is used to receive the reference signal, and an inverting input terminal of the second operational amplifier is connected to an output terminal of the second operational amplifier and a first terminal of the first acquisition unit; and A third operational amplifier, wherein the non-inverting input terminal of the third operational amplifier is used to receive the sampling signal, and the inverting input terminal of the third operational amplifier is connected to the output terminal of the third operational amplifier and the first terminal of the second acquisition unit.

6. The over-temperature protection circuit according to claim 5, characterized in that: The over-temperature protection circuit also includes: a fifth resistor, one end of which is connected to a power source; and A sixth resistor, one end of the sixth resistor is connected to the other end of the fifth resistor and the non-inverting input end of the second operational amplifier, and the other end of the sixth resistor is grounded.

7. The over-temperature protection circuit according to claim 5, characterized in that: The over-temperature protection circuit also includes: a seventh resistor, one end of which is connected to a power source; an eighth resistor, one end of the eighth resistor being connected to the other end of the seventh resistor and the non-inverting input end of the second operational amplifier; and A thermistor, one end of the thermistor is connected to the other end of the eighth resistor, the other end of the thermistor is grounded, and the thermistor is arranged adjacent to the load.

8. The over-temperature protection circuit according to any one of claims 1 to 7, characterized in that: The difference calculation module comprises: A third acquisition unit, wherein a first end of the third acquisition unit is connected to the signal sampling module and is used to access the reference signal, and a second end of the third acquisition unit is grounded; a fourth acquisition unit, wherein a first end of the fourth acquisition unit is connected to the differential amplification module and is used to access the differential signal; and A fourth operational amplifier, wherein the non-inverting input terminal of the fourth operational amplifier is connected to the third terminal of the third acquisition unit, the inverting input terminal of the fourth operational amplifier is connected to the second terminal of the fourth acquisition unit, the output terminal of the fourth operational amplifier is connected to the third terminal of the fourth acquisition unit and the driving circuit, and the fourth operational amplifier is used to generate the difference signal based on the reference signal and the differential signal, and output it to the driving circuit.

9. The over-temperature protection circuit according to claim 8, characterized in that: The third acquisition unit includes a ninth resistor and a tenth resistor, one end of the ninth resistor is connected to the signal sampling module, the other end of the ninth resistor is connected to one end of the tenth resistor and the in-phase input end of the fourth operational amplifier, and the other end of the tenth resistor is grounded; and, The fourth acquisition unit includes an eleventh resistor and a twelfth resistor, one end of the eleventh resistor is connected to the differential amplifier module, the other end of the eleventh resistor is connected to one end of the twelfth resistor and the inverting input end of the fourth operational amplifier, and the other end of the twelfth resistor is connected to the output end of the fourth operational amplifier; Wherein, the resistance values ​​of the ninth resistor, the tenth resistor, the eleventh resistor and the twelfth resistor are equal.

10. A load driving system, characterized in that: include: load; The over-temperature protection circuit according to any one of claims 1 to 9, wherein the over-temperature protection circuit is connected to the load; as well as, A driving circuit is connected to the load and the over-temperature protection circuit.

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